Photochemistry (Volume 18)

Photoc hemist ry Volume 18 A Specialist Periodical Report Photochemistry Volume 18 A Review of the Literature publ...

Author: D. Bryce-Smith

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Photoc hemist ry

Volume 18

A Specialist Periodical Report

Photochemistry Volume 18

A Review of the Literature published between July 1985 and June 1986 Senior Reporter D. Bryce-Smith, Department of Chemistry University of Reading Reporters N. S. Alien, Manchester Polytechnic A. Cox, University of Warwick R. 8. Cundall, MRC Radiobiology Unit, Didcot A. Gilbert, University of Reading A. Harriman, The Royal Institution W. M. Horspool, University of Dundee S. T. Reid, The University of Kent

6

+&

ROYAL SOCIETY OF CHEMISTRY

ISBN 0-85 186-165-2 ISSN 0556-3860

Copyright @ 1987 The Royal Society of Chemistry A11 Rights Reserved

N o part of this book may be reproduced or transmitted in any form or by any means-graphic, electronic, including photocopying, recording, taping, or information storage and retrieval systems-without written permission from the Royal Society of Chemistry

Published by The Royal Society of Chemistry Burlington House, London, W1V OBN Printed in Great Britain by Whitstable Litho Ltd., Whitstable, Kent

Introduction ~~~

Volume 18 i s c o n t i n u i n g w i t h o n l y o n e major change from r e c e n t p r e v i o u s Volumes, namely o m i s s i o n of t h e C h a p t e r on G a s Phase P h o t o p r o c e s s e s .

T h i s change h a s a r i s e n from a number of

c o n s i d e r a t i o n s , n o t least o u r d e s i r e t o k e e p t h e o v e r a l l l e n g t h of t h e Volume, and hence t h e p r i c e , a t a manageable and economic level.

I n t h e p a s t , we have t r i e d t o p r o v i d e broad-spectrum

c o v e r a g e of p h o t o c h e m i s t r y , a l t h o u g h w e have r e a l i s e d t h a t most p h o t o c h e m i s t s t e n d t o work i n s p e c i a l i s e d a r e a s of t h e s u b j e c t , and many whose p r i n c i p a l i n t e r e s t s l i e i n , s a y , t h e more p h y s i c a l a s p e c t s may n o t f i n d t h e t i m e t o r e a d t h o s e s e c t i o n s more c o n c e r n e d w i t h s y n t h e t i c a p p l i c a t i o n s o f p h o t o c h e m i c a l t e c h n i q u e s , f o r example.

Although w e s t i l l r e t a i n t h e o r i g i n a l

i d e a l o f c o v e r i n g most a s p e c t s of p h o t o c h e m i s t r y w i t h i n a s i n g l e volume, w e have f e l t a b l e t o withdraw t h e s e c t i o n on gas-phase photoprocesses because D r . J.E.Baggott,

who c o n t r i b u t e d t h i s

s e c t i o n i n Volumes 16 and 1 7 , h a s now j o i n e d w i t h

Dr. M.N.R.Ashfold

(who i s a l s o a p r e v i o u s c o n t r i b u t o r t o

' P h o t o c h e m i s t r y ' ) t o p r o d u c e a new i n f o r m a l series o f books, commissioned by t h e Royal S o c i e t y of C h e m i s t r y , w h i c h are d e s i g n e d t o meet t h e r e q u i r e m e n t s of t h e s c i e n t i f i c community i n t h e f i e l d s of g a s k i n e t i c s , gas-phase m o l e c u l a r s p e c t r o s c o p y and p h o t o c h e m i s t r y , and r e a c t i o n dynamics.

These new r e v i e w s w i l l t h e r e -

f o r c o n t i n u e t h e c o v e r a g e o f gas-phase more g e n e r a l p h y s i c o - c h e m i c a l c o n t e x t .

photochemistry, but i n a R e a d e r s may l i k e t o n o t e

t h a t t h e f i r s t volume e n t i t l e d "Molecular P h o t o d i s s o c i a t i o n Dynamics" i s d u e t o be p u b l i s h e d i n t h e summer o f 1987. I t i s hoped t h a t t h e a n n u a l Review of t h e Year w i l l b e resumed i n Volume 1 9 .

D . Bryce-Smith.

Contents PART I

PHYSICAL ASPECTS OF PHOTOCHEMISTRY Photophysical Processes in Condensed Phases By R.B.

3

Cundall

1

General

3

2

Singlet State Processes

8

2.1 2.2 2.3 2.4 2.5 2.6 2.7

3 4

Electron Transfer Processes and Exciplexes Dyes and Related Systems Photoisomerization and Related Processes Electronic Excitation Energy Transfer Polymeric Systems Colloidal and Heterogeneous Systems Biological Systems

11

14

16 18 19

20 24

Triplet Processes

30

Other Systems References

36

37

PART I1

PHOTOCHEMISTRY OF INORGANIC AND ORGANOMETALLIC COMPOUNDS

Chapter 1

The Photochemistry of Transition-metal Complexes

57

B y A . Cox 1

Introduction

57

2

Titanium

57

3

Vanadium and Niobium

59

4

Chromium, Molybdenum, and Tungsten

59

5

6

Manganese Iron

63

7

Ruthenium

64

8

Osmium

72

9

Cobalt Rhodium

72

10 11

Iridium

76

12

77

13

Nickel Palladium and Platinum

14

Copper

79

63

74

77

Contents

viii 15

Lanthanides

16

Uranium

81 83

17

Actinides

84

18

Miscellaneous

84

References

88

Chapter 2

The Photochemistry of Transition-metal Organometallic Compounds By A .

105

Cox

1

Introduction

105

2

Zirconium

105

3

Vanadium,

4

Chromium, Molybdenum, a n d T u n g s t e n

105

5

Manganese a n d Rhenium

113

6

Iron

115

7

Ruthenium

121

8

Osmium

121

9 10

Cobalt

123

Rhodium and I r i d i u m

124

11

Nickel, Palladium, and Platinum

126

12

Copper

129

13

Miscellaneous

129

References

129

The Photochemistry of Compounds of the Main Group Elements

140

Chapter 3

By A .

Niobium, and Tantalum

105

Cox

Introduction

140

Anions

140

A l k a l i Metals

140

Boron

140

Silicon

140

Nitrogen

145

Oxygen a n d S u l p h u r

145

Halogens

146

Miscellaneous

147

References

147

ix

Contents PART I11

ORGANIC ASPECTS OF PHOTOCHEMISTRY

Chapter 1

Photolysis of Carbonyl Compounds B y W.M.

1 2 3

4

Chapter 2

Norrish Type I Reactions Norrish Type I1 Reactions Oxetan Formation Rearrangement and Fragmentation Reactions References Enone Cycloadditions and Rearrangements: Photoreactions of Dienones and Quinones By W . M .

1

2

3

4

5

6

Chapter 3

155 165 168 171 172

176

Horspool

Cycloaddition Reactions Intramolecular Additions Additions to Cyclopentenones Additions to Cyclohexanones Intermolecular Additions Open Chain Systems Cyclopentenone Cyclohexenones Miscellaneous Reactions Rearrangement Reactions

176 176 176 179 179 179 184 184 190 195

a,@-Unsaturated Systems $,y-Unsaturated Systems Photoreactions o f Thymines and Related Compounds Photochemistry o f Dienones Linearly Conjugated Dienones Cross-conjugated Dienones 1,2-, 1,3-, and 1,4-Diketones 1,2-Diketones 1,3-Diketones 1,4-Diketones Phthalimides and Related Compounds Quinones References

195 199 204 208 208 208 212 212 212 215 215 222 228

Photochemistry of Albenes, Alkynes. and Related Compounds

237

B y W.M.

1

155

Horspool

Horspool

Reactions of Alkenes Group Migration Reactions cis-trans Isomerization Halogeno-alkenes Addition Reactions

237 237 237 243 243

Contents

X

2

Alkynes Reactions involving Cyclopropane Rings

243 243

3

R e a c t i o n s of D i e n e s , T r i e n e s , a n d H i g h e r P o l y e n e s

248

4

(2+2) Intramolecular Additions

255

5

Dimerization and I n t e r m o l e c u l a r Cycloadditions

259

6

Miscellaneous Reactions

263

References

267

Photochemistry of Aromatic Compounds

273

Chapter 4

By A .

Gilbert

1

Isornerization Reactions

273

2

Addition Reactions

277

3

Substitution Reactions

289

4

Intramolecular Cyclization Reactions

303

5

Dimerization Reactions

322

6

Lateral-Nuclear

327

Chapter 5

Rearrangements

References

333

Photo-reduction and -oxidation

338

By A .

Cox

338

Introduction

338

R e d u c t i o n of t h e C a r b o n y l G r o u p R e d u c t i o n of N i t r o g e n - c o n t a i n i n g

Compounds

Miscellaneous Reductions

345

S i n g l e t Oxygen

346

O x i d a t i o n of A l i p h a t i c Compounds

347

O x i d a t i o n of A r o m a t i c Compounds Oxidation of Nitrogen-containing

Chapter 6

342

350

Compounds

353

Miscellaneous Oxidations

357

References

358

Photoreactions of Compounds containing Heteroatoms other than Oxygen

368

By S.T.

Reid

1

N i t r o g e n - c o n t a i n i n g Compounds

368

2

Rearrangements Addition Reactions Miscellaneous Reactions S u l p h u r - c o n t a i n i n g Compounds

368 386 399 402

xi

Contents 3

Chapter 7

Compounds containing Other Heteroatoms References

407

Photoelimination

420

By S . T .

414

Reid

1

Elimination of Nitrogen from Azo-compounds

420

2

Elimination of Nitrogen from Diazo-compounds Elimination of Nitrogen from Azides Photoelimination of Carbon Dioxide Fragmentation of Organosulphur Compounds

428

3 4 5 6

By N.S. 1 2

3

5 6

PART V

Introduction Photopolymerization

2

457

457 457

Photoinitiated Addition Polymerization Photografting 2.3 Photocrosslinking Optical and Luminescent Properties Photodegradation and Photooxidation Processes 4.1 Polyolefins 4.2 Poly(viny1 halides) 4.3 Polyacrylates 4.4 Polyamides and Copolymers 4.5 Polystyrenes and Copolymers 4.6 Polyesters 4.7 Bisphenol A Polymers 4.8 Miscellaneous Polymers

458 469 470

Photostabilization Processes Photochemistry of Dyed and Pigmented Polymers References

501

PHOTOCHEMICAL ASPECTS OF SOLAR ENERGY

523

By A . 1

442

Allen

2.1 2.2

4

440

Miscellaneous Decomposition and Elimination Reactions 4 4 6 References 450

POLYMER PHOTOCHEMISTRY

PART I V

434

474 487 487 489 491 491 492 493 495 495 506 509

Harriman

Introduction Homogeneous Photosystems Valence Isomerism Photosensitizer s

523 525 525 526

Contents

xii H2 P h o t o p r o d u c t i o n 0 Photoproduction Ciarge Separation

527 530 531

3

Heterogeneous Photosystems

533

4

P h o t o e l e c t r o c h e m i c a l Cells

538

5

Luminescence Solar C o l l e c t o r s

540

References

541

AUTHOR INDEX

555

Part I PHYSICAL ASPECTS OF PHOTOCHEMISTRY

Photophysical Processes in Condensed Phases BY R. B. CUNDALL T h e form o f t h i s r e v i e w follows that in previous volumes although it has been decided this year t o c i t e m o r e o f t h e w o r k published o n biochemical systems.

T h e applications o f l u m i n e s c e n c e

to biological problems is t h e most active area in condensed phase

photophysics and t h i s survey attempts t o reflect this situation. 1 General

Theoretical studies in photophysics tend t o be d i v e r s e and no particular themes are evident at the present time.

A somewhat

refined paper d e a l s w i t h radiation-molecule interactions f r o m t h e viewpoint o f q u a n t u m electrodynamics'

and a m o r e c o n v e n t i o n a l

approach through t u n n e l effect theory has been used t o interpret t h e a-cleavage o f k e t o n e s 2 .

Solvent influences o n excited states

and solvatochromism have also been examined theoretically in some detail3-"

A m o d e l for t i m e dependent

fluorescence dependent

solvent shifts is timely in view o f t h e current intensity o f e x p e r i m e n t a l effort'.

Theoretical a n a l y s i s o f t h e d e t a i l s o f

quenching processes have involved consideration o f long r a n g e , t h e role o f dielectric constant and

electrostatic interactions' ionic strength',

and t h e effects o f q u e n c h e r s on luminescent

polyelectrolytes w i t h pendant probes'

.

The theories o f

fluorescence depolarization in macroscopically ordered u n i v e r s a l systems

11

and concentration d e p o l a r i z a t i o n in t h e presence o f

orientational correlation d u e t o incoherent energy transfer"

are

highly t o p i c a l i n v i e w o f many e x p e r i m e n t a l studies w h i c h a r e underway. Steady progress in i n s t r u m e n t a l d e s i g n and data processing i s f u n d a m e n t a l to research in photophysics. this area can be quoted.

Only selected papers in

Yip13 has reviewed picosecond absorption

spectroscopy in some d e t a i l and treats both methods and applications.

Hopkins and Rentzepis"

discuss biological

applications, particularly primary processes in vision, o f picosecond laser phenomena.

Three papers w h i c h d e a l w i t h

3

Photochemistry

4

m e a s u r e m e n t o f m o l e c u l a r a n i s o t r o p i e s using l a s e r t e c h n i q u e s , a l t h o u g h d e a l i n g w i t h g a s p h a s e s i t u a t i o n s a r e a l s o relevant and applicable to condensed phase

photo physic^^^.

Details o f a high

resolution picosecond transient absorption spectrometer utilising d y e e m i s s i o n and s t r e a k c a m e r a have been published16 high s e n s i t i v i t y o f picosecond

and t h e u l t r a -

pump-probe measurements of

c o n c e n t r a t i o n has been d r a m a t i c a l l y d e m o n s t r a t e d using c r e s y l violet17.

O p t i c a l m u l t i c h a n n e l a n a l y s i s i s a l s o very u s e f u l in

e x a m i n i n g s h o r t l i v e d transients".

T h e use o f a h i g h i n t e n s i t y

l a s e r t o m o d u l a t e c o n c e n t r a t i o n d i f f e r e n c e s is e x p l o i t e d t o increase sensitivity o f detection i n concentration modulated a b s o r p t i o n s p e c t r o s c o p y (COMAS)'

.

Using m i c r o c h a n n e l p l a t e

detectors with time correlated single photon counting coupled with a pico- and s u b - p i c o s e c o n d l a s e r m a k e s i n s t r u m e n t a l f u n c t i o n w i d t h s of

20 ps s e e m feasible2'.

A d e s i g n f o r a high s e n s i t i v i t y l a s e r

f l u o r i m e t e r d e t e c t i n g as f e w a s 8 0 0 0 m o l e c u l e s o f r h o d a m i n e R 6 G i s noteworthy2'

.

W e h r y 2 2 h a s published a very c o m p r e h e n s i v e c o l l e c t i o n o f references to recent work o n techniques relevant to molecular f l u o r e s c e n c e , p h o s p h o r e s c e n c e , and c h e m i l u m i n e s c e n c e .

V i ~ s e rhas ~ ~

edited t h e q u i t e e x t e n s i v e p r o c e e d i n g s o f a s y m p o s i u m o n t i m e resolved f l u o r e s c e n c e s p e c t r o s c o p y . subjects, with multifrequency

P a p e r s d e a l , amongst o t h e r

p h a s e f l ~ o r o m e t r y, ~ p~h a s e resolved

f l u o r e s c e n c e s p e c t r o s c ~ p y, ~t~i m e c o r r e l a t e d s i n g l e p h o t o n c o u n t i n g using l a s e r e x c i t a t i o n 2 6 , t h e k i n e t i c i n t e r p r e t a t i o n o f fluorescence decays27 , determination o f t i m e resolved flUOreSCenCe spectra and a n i s o t r o p y d e c a y s using s i n g l e p h o t o n c o u n t i n g and synchronously pumped d y e l a s e r excitation2',

photon t i m e o f f l i g h t

( b r o u g h t a b o u t by u s e o f e x t r e m e l y l o n g silica l i g h t p i p e s ) 29 fluorescence spectroscopy , and t h e a p p l i c a t i o n o f picosecond s p e c t r o s c o p y t o a n a l y s e t h e s t r u c t u r e and m o t i o n s o f b i o p o l y m e r s , p a r t i c u l a r l y DNA3'.

Many o t h e r p u b l i c a t i o n s h a v e d e a l t w i t h t h e

m e a s u r e m e n t o f f l u o r e s c e n c e d e c a y times.

A system describing t h e

r e p l a c e m e n t o f a m u l t i c h a n n e l a n a l y s e r by A D C and a m i c r o c o m p u t e r has c o n s i d e r a b l e f i n a n c i a l a t t r a c t i o n s

31

.

Short l i v e d f l u o r e s c e n t

t r i p h e n y l m e t h a n e d y e s m a y b e used t o c o r r e c t f o r i n s t r u m e n t a l a r t i f a c t s i n p h o t o d e t e c t o r s in l i f e t i m e

measurement^^^.

On t h e fly

d e t e r m i n a t i o n o f f l u o r e s c e n c e l i f e t i m e s c a n be obtained f r o m t w o point d e c a y measurements3'

and p h o t o t u b e t i m e s h i f t s c a n be

e l i m i n a t e d by p h a s e p l a n e m e t h o d s 3 4 .

T h e use of microchannel plate

p h o t o m u l t i p l i e r s in a l l a s p e c t s o f t i m e c o r r e l a t e d f l u o r e s c e n c e

I: Photophysical Processes in Condensed Phases

5

spectroscopy 1 s described in a very u s e f u l paper by Y a m a z a k i Bt aL3’.

A comparative study o f correction methods for t h e

wavelength d e p e n d e n c e o f instrument r e s p o n s e functions i n t i m e correlated s i n g l e photon c o u n t i n g indicates this to be o n e o f t h e A method

principle d i f f i c u l t i e s in getting good data fits36.

for

carrying out t i m e resolved multiphoton counting has a l s o been developed3’

.

P h a s e shift and modulation t e c h n i q u e s have come i n t o greater P r o m i n e n c e largely d u e to t h e feasibility o f varying t h e m o d u l a t i o n frequency o f t h e exciting light.

An authoritative d e s c r i p t i o n o f

recent developments w i t h illustrative examples of multiexponent d e c a y s , decay o f a n i s o t r o p y , and t i m e resolved emission spectra has been given by Lakowicz pt al?

A n e w approach t o the analysis o f

heterogeneous emitting systems and t i m e d o m a i n fluorescence s p e c t r o m e t r y , has been f o r m u l a t e d 3 g and four components ( a n t h r a c e n e d e r i v a t i v e s ) analysed using two modulation frequencies and t h r e e 40 . A l l f o u r parameters needed t o express e m i s s i o n wavelengths systems w i t h two lifetimes h a v e shown to be d e t e r m i n a b l e by t h e use o f modulation techniques4

’.

G l o b a l and target analysis o f complex decay phenomena and t h e examination of ground state heterogeneity, anisotropic m o t i o n s , and excited state reactions has been critically reviewed42 and a method for t h e analysis o f t h e complete decay surface for systems undergoing excited state deprotonation proposed43

.

The theory and

applications o f anisotropy decay associated fluorescence spectra and analysis o f r o t a t i o n a l heterogeneity h a v e been d i s c ~ s s e d ‘ ~and applied to t h e behaviour o f U - U 1 , 6 - d i p h e n y l - t , 3 , 5 - h e x a t r i e n e ( D P H ) in lipid bilayers4’.

Global d e c o n v o l u t i o n has been used t o

g e n e r a t e time emission spectra and applied to 1 , 2 - - ( 1 0 acetoxyanthryl) e t h a n e , intramolecular excimer f o r m a t i o n , and analysis o f a t h r e e component m i x t u r e composed o f P O P O P , a n t h r a c e n e , and diphenylanthracene

46

,

Order parameters of ground

and excited states have been measured and it has been pointed out that t h e orientational distributions are not necessarily t h e s a m e for ground and excited s t a t e s , as is t h e case for D P H 4 t .

The

significance o f 4th rank orientational o r d e r parameters for fluorophores in m e m b r a n e s and their use a s a m e a n s o f distinguishing different m o d e l s o f structure and organization has been m a d e and t h e much studied DPH s y s t e m , in particular, has been examined in detail4’.

6

Photochemistry T h e p o s s i b i l i t y that m u l t i c o m p o n e n t d e c a y s obtained by s i n g l e

photon c o u n t i n g w h i c h , a l t h o u g h a p p e a r i n g t o yield a s a t i s f a c t o r y fit t o a s m a l l n u m b e r o f e x p o n e n t i a l d e c a y s m a y c o n c e a l u n d e r l y i n g e x t e n s i v e s e t s o f l i f e t i m e s w i t h a variety o f d i s t r i b u t i o n s has been c o n s i d e r e d i n s e v e r a l p u b l i c a t i o n s .

F a u l t s i n e q u i p m e n t can

m a k e t h i s s i t u a t i o n d i f f i c u l t t o d i s t i n g ~ i s h ' ~ and a m e t h o d for t h e recovery s u c h c o m p l e x d i s t r i b u t i o n has been p r o p o s e d S o . T h e d i s t r i b u t i o n o f f l u o r e s c e n c e l i f e t i m e s o f m o l e c u l e s absorbed o n s u r f a c e s w h i c h a r e c o n s i s t e n t w i t h t w o m e a s u r e d l i f e t i m e s c a n be fitted to either a single Gaussian or bimodal distributions1 A method developed

f o r e s t i m a t i n g e x c i t e d s t a t e pK

*

.

for

f l u o r e s c e n t c o m p o u n d s f r o m r a t e s o f proton t r a n s f e r t o an a p p r o p r i a t e d o n o r o r a c c e p t o r has been a p p l i e d t o t y r o s i n e , $ - n a p h t h o l , 2 - m e t h o x y c i n n a m i c acid and B - c a r b o l i n e S 2 .

It has been

proposed t h a t 8 - c a r b o l i n e i n 1 N H Z S 0 4 i s a b e t t e r f l u o r e s c e n c e (Amax = 4 5 0 nm, *F = 0 . 6 0 ) with a em s i n g l e e x p o n e n t i a l l i f e t i m e o f 22.03 2 0.12 n s s 3 . M e a s u r e d

standard t h a n q u i n i n e b i s u l p h a t e

f l u o r e s c e n c e i n t e n s i t y and p o l a r i z a t i o n v a l u e s a r e s e v e r e l y affected by a b s o r p t i o n a n d l o r s c a t t e r i n g i n c u v e t t e s and an e x p r e s s i o n has been d e r i v e d w h i c h r e l a t e s t h e o b s e r v e d a n i s o t r o p y t o sample turbiditys4.

Retro-diffracted light in T-format

f l u o r e s c e n c e s p e c t r o m e t e r s m a y be s o u r c e o f e r r o r p a r t i c u l a r l y w h e n m o d e l o c k e d l a s e r e x c i t a t i o n s y s t e m s a r e being usedss.

Two

papers d e a l w i t h c h a r a c t e r i s a t i o n of l a t e r a l d i f f u s i o n i n a r t i f i c i a l and b i o l o g i c a l m e m b r a n e s by p h o t o b l e a c h i n g and m e a s u r e m e n t o f t h e a p p r o p r i a t e d i f f u s i o n constantss6

I s 7

.

T h e a p p l i c a t i o n o f t i m e r e s o l v e d r e s o n a n c e Raman s p e c t r o s c o p y for studying t r a n s i e n t s has b e e n reviewed and t h e p r o p e r t i e s o f b a c t e r i o r h o d o p s i n and h a e m o g l o b i n d y n a m i c s a r e s p e c i f i c a l l y discusseds8.

T h i s t e c h n i q u e a l l o w s p h o t o p h y s i c a l and p h o t o c h e m i c a l

p r o c e s s e s in t h e s u b p i c o s e c o n d r e g i m e t o b e e l u c i d a t e d and characterised.

C i r c u l a r l y polarized

luminescence spectroscopy, a

t e c h n i q u e w h i c h is l i m i t e d to a s m a l l n u m b e r o f l a b o r a t o r i e s , h a s a l s o been c o m p r e h e n s i v e l y reviewed"

.

The application of E u l 1 1 1 )

and T b ( I I 1 ) c o m p l e x e s and p h o t o n c o u n t i n g m e t h o d s d e m o n s t r a t e s a method w i t h c o n s i d e r a b l e p r o m i s e f o r t i m e r e s o l v e d l u m i n e s c e n c e probe s t u d i e s o f b i o c h e m i c a l s t r u c t u r e s . extensively reviewed t h e application

of

8 r a s l a ~ s k y has ~~ p h o t o a c o u s t i c and

p h o t o t h e r m a l m e t h o d s as m e a n s o f s t u d y i n g r a d i a t i o n l e s s deactivation processes in systems o f biological interest.

The

a p p l i c a t i o n o f 3 0 f l u o r e s c e n c e t o t h e n e e d s o f f o r e n s i c science. in


7

particular t h e identification o f gasoline, have also been surveyed A n o t h e r u s e f u l r e v i e w w h i c h a s been p u b l i s h e d d e a l s

by S i e g e 1 6 1 .

w i t h bioanalytical applications o f fluorescence quenching62

.

A number o f interesting observations using luminescence s p e c t r o s c o p y f o r t h e o b s e r v a t i o n o f n e w e f f e c t s h a v e been r e p o r t e d . f l u o r e s c e n c e h a s been o b s e r v e d t o f o l l o w S n +-T 1

S,+S,,

apparently for t h e first time63.

absorption,

Shock compression of condensed

m e d i a c a n b e produced by i n t e n s e l a s e r l i g h t i l l u m i n a t i o n . s h i f t o f u p t o 800 cm-'

A red

has b e e n o b s e r v e d w i t h b a n d s i n t h e

a n t h r a c e n e f l u o r e s c e n c e s p e c t r u m at p r e s s u r e s u p t o 10 kbar6"

and

t h e c h a n g e o f v i s c o s i t y o f g l y c e r o l w i t h p r e s s u r e s u p t o 19 k b a r

.

e s t i m a t e d f r o m c r y s t a l violet f l u o r e s c e n c e polarization6'

A study

o f t h e e f f e c t s o f p H , s u b s t r a t e , heavy a t o m s , e 2 . o n use o f s o l i d s t a t e r o o m t e m p e r a t u r e f l u o r e s c e n c e and p h o s p h o r e s c e n c e f o r a n a l y s i s o f m i x t u r e s h a s a l s o been reported".

T i m e r e s o l u t i o n has

been used t o s u p p r e s s t h e e f f e c t s o f f l u o r e s c e n c e i n R a m a n spectroscopy

67

.

C o n v e r s e l y , Raman b a c k g r o u n d i n l a s e r i n d u c e d

f l u o r e s c e n c e has been r e d u c e d by d e t e c t i o n o f t h e second h a r m o n i c : i n fact t h e b a c k g r o u n d i s s o r e d u c e d t h a t a m o u n t s as l o w a s 210 f l u o r o p h o r e m o l e c u l e s c a n b e d e t e c t e d i n t h e p r o b e volume6'.

Time

r e s o l v e d d e t e r m i n a t i o n o f t e r b i u m as binary and t e r n a r y c o m p l e x e s h a s a l s o b e e n described6'.

A n i n t e r e s t i n g d e s i g n f o r an a n n u l a r

photochemical reactor shows that some o f t h e more conventional 70

photochemical techniques are still being improved also A

.

c o m p r e h e n s i v e a t l a s o f f l u o r e s c e n c e s p e c t r a and l i f e t i m e s o f

d y e s attached t o p r o t e i n s w i l l p r o v e i n v a l u a b l e t o u s e r s o f b i o l o g i c a l probes71.

F l u o r e s c e n c e i s proving t o be u s e f u l

p h e n o m e n o n in c y t o g e n e t i c s .

P e r t u r b a t i o n s o f d y e f l u o r e s c e n c e by

v a r i a t i o n s i n DNA c o m p o s i t i o n and i n t e r d y e e n e r g y t r a n s f e r c a n b e used t o study c h r o m o s o m e s t r u c t u r e , r e p l i c a t i o n and r e p a i r 7 2 . i s o b v i o u s l y o f c o n s i d e r a b l e v a l u e t o biologists.

This

Fluorescence

m i c r o s c o p y i s b e c o m i n g an e x t r e m e l y u s e f u l t o o l i n c e l l b i o l o g y e s p e c i a l l y i n v i e w o f t h e e x t e n s i v e r a n g e o f p r o b e s w h i c h have b e c o m e available.

A

very c o m p r e h e n s i v e r e v i e w o n f l U O r e S C e n C e

d i g i t a l i m a g i n g m i c r o s c o p y i n d i c a t e s t h e p o w e r and p r o m i s i n g f u t u r e 73 o f this technique . Amongst o t h e r p a p e r s p a r t i c u l a r a t t e n t i o n i s d r a w n to a d e s i g n f o r a f l u o r e s c e n c e m i c r o s c o p y s y s t e m w i t h p i c o s e c o n d t i m e r e s o l u t i o n 7 4 and t h e o b s e r v a t i o n o f f l u o r e s c e n c e microscopy in three dimensions o r microtomoscopy

75

Photochemistry

8 2 Siwalet State Processes

T h e r e i s a t r e n d away f r o m t h e s t u d y o f p a r t i c u l a r m o l e c u l e s , such as b e n z e n e , w h i c h h a v e been r e g a r d e d a s b e i n g e x a m p l e s o f specific chromophore properties which are essential for a complete u n d e r s t a n d i n g o f b e h a v i o u r in m o r e c o m p l e x s i t u a t i o n s .

Simple

m o l e c u l e s a r e h o w e v e r s t i l l i m p o r t a n t s u b j e c t s f o r research. l i f e t i m e s o f 'Ago2

The

m o l e c u l e s i n r a r e g a s m a t r i c e s h a v e been

m e a s u r e d and f o u n d t o r e l a t e t o t h e r e f r a c t i v e i n d e x o f t h e E m i s s i o n f r o m O 2 ('Eg*)

medium.76

has been detected for t h e first

t i m e by s e n s i t i z a t i o n f r o m t h e b e n z o p h e n o n e t r i p l e t at 1.93 p m w i t h a very s h o r t l i f e t i m e 7 7 .

T h e s a m e s t a t e h a s b e e n d e t e c t e d by

d e c o m p o s i t i o n o f l , 4 - d i m e t h y l n a p h t h a l e n e e n d o p e r o x i d e and by d i r e c t e x c i t a t i o n o f g r o u n d s t a t e 3 0 2 t o t h e S2 state.

The photochemistry

o f selected C2 and C3 c o m p o u n d s in l o w t e m p e r a t u r e m a t r i c e s has been r e v i e w e d by Perutz'l'

and f o u r w a v e m i x i n g h a s b e e n used t o

study i n t e r a c t i o n s and r e o r i e n t a t i o n o f c a r b o n d i s u l p h i d e i n o r g a n i c liquids7'. p h o t o l y s i s o f S8

An unusual study i s that reported on t h e in c y c l o p e n t a n e t o g i v e S3 and S4

80

.

T h e f l u o r e s c e n c e d e c a y o f a l k a n e s i s a c c e l e r a t e d by x e n o n w h i c h i n f l u e n c e s both i n t e r s y s t e m c r o s s i n g and i n t e r n a l c o n v e r s i o n 81 processes . T h e f l u o r e s c e n c e l i f e t i m e o f c y c l o h e x a n e i n solid l i q u i d , and v a p o u r phases has been m e a s u r e d by VUV s y n c h r o t r o n radiation".

S y n c h r o t r o n r a d i a t i o n h a s a l s o b e e n used t o m e a s u r e 83

.

l i f e t i m e s o f a n u m b e r o f p a r a f f i n s and a l i c y c l i c c o m p o u n d s S2

4

So

e m i s s i o n has b e e n s e e n i n u - t r a n s

-

1,3,5,7,9*11,13-

t e t r a d e c a - h e p t a e n e i n s o l u t i o n at r o o m t e m p e r a t u r e and a t 77 K i n glassese4.

In t h i s c a s e t h e S2

and t h a t f o r S 1

4

S

is 2 l A -

9

So

-+

-+

transition is l l B :

llA-. g

3

llA9

Picosecond t i m e resolved

a b s o r p t i o n s p e c t r a o f l i q u i d CC14 and a l k y l c h l o r i d e s h a s been m e a s u r e d by 266 n m m u l i p h o t o n l a s e r p h o t o l y s i s a 5 is involved.

.

Photoionisation

T h e s i n g l e t and t r i p l e t e x c i t e d s t a t e s o f

n i t r o s a m i n e s h a v e been e x t e n s i v e l y e x a m i n e d e 6 and t h e m e c h a n i s m o f photolysis o f nitromethane in ethyl ether solution studied

87

.

T r a n s i e n t s i n t h e v a p o u r and s o l u t i o n p h a s e s o f h e x a f l u o r o b e n z e n e h a v e b e e n c h a r a c t e r i s e d a s S n s t a t e s and t h e 88 L a s e r f l a s h p h o t o l y s i s h a s used precursor of t h e Dewar isomer

.

t o s t u d y n u c l e o p h i l i c s u b s t i t u t i o n o f 4-chloro- and 4 - f l u o r o a n i s o l e i n a q u e o u s s o l u t i ~ n ~ ~T h.e p h o t o p h y s i c a l b e h a v i o u r o f p h e n o l and a n i s o l e i n v a r i o u s s o l v e n t s i n v o l v e s d e a c t i v a t i o n o f S1 V J t h e triplet manifold, although t h e nature o f t h e final state is Solvent

I: Photophysical Processes in Condensed Phases dependent”.

9

S o l v e n t e f f e c t s o n Lne f l u o r e s c e n c e s p e c t r a o f

a m i n o b e n ~ e n e s ~, ’ p i c o s e c o n d s t u d i e s o n e x c i t e d s t a t e f o r m a t i o n i n

p-

d i e t h y l a n i l i n e g 2 , and t h e e f f e c t o f i n t r a m o l e c u l a r r o t a t i o n i n cyano-fl , N - d i a l k y l a n i l i n e s 3 h a v e a l s o been r e p o r t e d .

Red s h i f t s i n

t h e f l u o r e s c e n c e s p e c t r a o f t w o p y r r y l i u m i o n d e r i v a t i v e s h a v e been assigned t o f a s t s o l v e n t r e l a x a t i o n p r o c e s s e s g 4 . T h e S,

s t a t e o f b i p h e n y l i n s o l u t i o n h a s been o b s e r v e d by b o t h

a b s o r p t i o n and by Raman spectra”. s t e p w i s e t w o p h o t o n excitation.

T h e c a t i o n r a d i c a l i s f o r m e d by P u l s e r a d i o l y s i s h a s b e e n used t o

follow intramolecular excimer formation in stereoisomeric d i p h e n y l t r i d e ~ a n e s ’ ~w h i c h a r e m o d e l s y s t e m s f o r p o l y s t y r e n e . T h e S1

s t a t e o f n a p h t h a l e n e has a l s o been o b s e r v e d by t i m e r e s o l v e d

r e s o n a n c e R a m a n s p e c t r o s c o p y and has a broad a b s o r p t i o n a r o u n d 425 n m g 7 .

O t h e r s h o r t t i m e s t u d i e s o n t h e S2 s t a t e o f a z u l e n e h a v e

d e m o n s t r a t e d s i n g l e v i b r a t i o n a l l e v e l f l u o r e s c e n c e and t h i s h a s allowed t h e d y n a m i c s o f v i b r a t i o n a l e n e r g y r e l a x a t i o n t o be studied9’.

T h e same investigators have also examined t h e transient

Raman spectra o f various substituted stilbenesg9.

Fluorescence

l i f e t i m e s o f t r a n s - s t i l b e n e and i t s s t r u c t u r a l l y r i g i d d e r i v a t i v e s , t h e t e t r a h y d r o c h r y s e n e s , h a v e b e e n m e a s u r e d and compared’ O 0

.

The

effect o f m o d e r a t e l y high p r e s s u r e o n t h e a b s o r p t i o n and f l u o r e s c e n c e s p e c t r a o f D P H , 1 , 8 - d i p h e n y l o c t a t e t r e n e , and 4 , 4 ’ d i c y a n o - O P H s h o w t h e s e p a r a t e e f f e c t s on t h e e m i s s i o n f r o m b o t h t h e

’ Ag

and ’Bu states”‘.

A

detailed study o f t h e fluorescence o f a 102 S2 s t a t e

n u m b e r o f DPH d e r i v a t i v e s h a s a l s o been p u b l i s h e d

.

properties o f fixed 8-cyanoheptafulvenes, i n particular values o f B F and T~

have been measured l o 3 .

p y r i d i n e matrices’”

-

Anthracene excimers i n

and i n l i q u i d anthracene’

O5

have examined as

w e l l 8s m i x e d e x c i m e r s f o r m e d by a n t h r a c e n e and p h e n a n t h r e n e S1

Sn

and T 1 -+

T

d e r i v a t i v e s h a v e bee:

106

.

absorption spectra o f anthracene d e t e r m i n e d by l a s e r f l a s h p h o t ~ l y s i s ’ ~ ’ .

The

fluorescence anisotropy o f 1,9-dimethylanthracene has been studied o v e r a w i d e r a n g e o f t e m p e r a t u r e and v i s c o s i t y u s i n g s y n c h r o t r o n r a d i a t i o n f o r excitation’

O’

.

Solvent effects on electronically

excited s t a t e s o f 9 , 9 ‘ - b i a n t h r y l s h o w e v i d e n c e f o r s o l v e n t e x c i p l e x e s w h i c h m a y , i n s t r o n g l y p o l a r s o l v e n t , be p r e c u r s o r s o f ionsl o g E-l-(g-anthryl)-P-( 10-methyl-9-anthryllethene gives excimer emission which correlates well with predictions which can be m a d e f r o m t h e c r y s t a l structure‘”. of t r a n s - ( 9 - a n t h r y l ) e t h y l e n e s

The e x c i t e d s t a t e p r o p e r t i e s

show t h e effects o f geometric

d i s t o r t i o n about t h e s i n g l e bond”’.

The conformations o f 9 -

Photochemistry

10

cyanoanthracene excimers have studied i n t h e crystalline state as a f u n c t i o n o f pressure’

-

Torsional dynamics of 9-carbonyl

2.

substituted a n t h r a c e n e s a f t e r t h e S

*

S ( r , n 1 transition

s h o w a c h a n g e f r o m a nearly perpendPcularl t o a c o p l a n a r f o r m 1 l 3 . The fluorescence properties o f meso-substituted h a v e been e x a m i n e d also’

’‘ .

amidoanthracenes

Pyrene excimers still attract

c o n s i d e r a b l e i n t e r e s t , f o r e x a m p l e , a p i c o s e c o n d t i m e resolved study has been m a d e o f e x c i m e r f o r m a t i o n in s i n g l e c r y s t a l s 1 1 5

.

T h e c o r r e c t e m i s s i o n s p e c t r u m o f f l u o r a n t h r e n e has b e e n obtained by u s e o f purified

samples’16.

T h e e m i s s i o n at 350 n m , w h i c h has been

reported p r e v i o u s l y , is p r o b a b l y a n i m p u r i t y , a c e p h e n a n t h r e n e . Solvent e f f e c t s on t h e p u r e r a d i a t i v e l i f e t i m e o f o v a l e n e have a l s o been observed‘

’

7 .

Trace amounts o f polynuclear aromatic compounds

( P N A I can be d e t e c t e d by t h e use o f a n t h r a c e n e as sensitizer’”. T h e r o t a t i o n a l d i f f u s i o n o f p - t e r p h e n y l and fl-quarterphenyl i n s o l u t i o n has been e x a m i n e d as a f u n c t i o n o f v i s c o s i t y and t e m p e r a t u r e by t i m e r e s o l v e d f l u o r e s c e n c e depolarization”

.

The

d e t a i l s o f p r o c e s s e s i n v o l v e d h a v e been d i s t i n g u i s h e d . H e t e r o c y c l i c s y s t e m s e x a m i n e d i n c l u d e v i b r a t i o n a l and e l e c t r o n i c r e l a x a t i o n i n n a p h t h a z a r i n and i t s d e u t e r a t e d d e r i v a t e s i n Ne and Ar matrices12’, azanaphthalenes of durene’ 22.

121

r e l a x a t i o n k i n e t i c s in

, and r e a c t i o n s o f q u i n o x a l i n e i n s i n g l e c r y s t a l s

The picosecond reorientational dynamics of resorufin

has been c o r r e l a t e d w i t h l i q u i d s t r u c t u r e 1 2 3 .

It a p p e a r s that t h e

first solvent shell strongly influences t h e rotational dynamics. Work on t h e p h o t o p h y s i c s o f c a r b o n y l c o m p o u n d s i s m u c h l e s s e x t e n s i v e t h a n i n p r e v i o u s years.

S o l v e n t a f f e c t s h a v e been

i n t e r p r e t e d as i n v o l v i n g T I - r *and n-m* t r a n s i t i o n s i n c a r b o n y l s and h y d r a ~ o n e s ” ~ . T h e t - b u t y l and m e t h y l e s t e r s o f 9 - a n t h r o i c acid ( a n d also t e t r a p h e n y l b u t a d i e n e ) s h o w a d e p e n d e n c e o f t h e e m i s s i o n s p e c t r u m on e x c i t a t i o n w a v e l e n g t h d u e t o t h e p r e s e n c e o f

conformer^'^^.

CNDO/S-CI

c a l c u l a t i o n s h a v e been performed on

e l e c t r o n i c states o f s o m e c a r b o n y l c o m p o u n d s c o n t a i n i n g o r g a n i c luminophores with a stilbene chromophore

126

.

A b s o r p t i o n and f l u o r e s c e n c e s p e c t r a o f P - ( g - a m i n o p h e n y l ) benzimidazole is shown to excite in two forms arising from internal hydrogen bonding t o an e x t e n t w h i c h d e p e n d s o n s o l v e n t polarity’ 2 7 M u l t i p h o t o n i o n i s a t i o n and d i s s o c i a t i o n o f N - i s o p r o p y l d i m e t h y l o x a t i r i d i n e o c c u r s t h r o u g h an assigned Shizuka’*’

s e r i e s o f Rydberg states’ 2 8

.

has reviewed excited state proton transfer

r e a c t i o n s and proton induced q u e n c h i n g of a r o m a t i c c o m p o u n d s .

The

.


11

l a t t e r i n v o l v e s i n t r a m o l e c u l a r C T s t r u c t u r e and s i m p l e a c i d - b a s e e q u i l i b r i a c a n n o t be achieved d u r i n g t h e l i f e t i m e o f e x c i t e d s t a t e s and c a r e i s needed i n d e t e r m i n i n g p,K

*

values.

Excited s t a t e

proton t r a n s f e r in m e t h y l - 5 - c h l o r o s a l i c y l a t e and m e t h y l 5 0 are examples o f systems examined equilibrium m e t h ~ x y s a l i c y l a t e3 ~

is not set u p i n t h e excited s t a t e o f 4 - ( 9 - a n t h r y l ) - N , N - d i m e t h y l a n i l i n e d u e t o t h e very slow d e p r o t o n a t i o n o f t h e e x c i t e d ' A H * F r e q u e n c y - d o m a i n f l u o r o m e t r y has been used t o e x a m i n e 132 Both r e v e r s i b l e and excited state deprotonation o f $-naphthol state131.

.

i r r e v e r s i b l e i o n i z a t i o n p r o c e s s e s i n t h e $ - n a p h t h o l s y s t e m c a n be distinguished.

P i c o s e c o n d s i n g l e p h o t o n c o u n t i n g has b e e n used t o

measure rate constants for excited state proton transfer o f c a r b a z o l e i n a l k a l i n e solution' 3 3 . hydroxyflavone

134

, 3-hydroxyxanthone

O t h e r s y s t e m s e x a m i n e d a r e 3135 , 2-hydronybenzimidazole' 3 6 ,

2- ( a m i n ~ m e t h y l ) b e n z i m i d a z o l e ' ~ and ~ , protonated

S c h i f f bases13'.

T h e p h o t o p h y s i c s o f r a d i c a l s a t t r a c t s c o n s i d e r a b l e i n t e r e s t at present.

Emission from short lived p - a m i n o p h e n y l t h i y l r a d i c a l s has

an e f f i c i e n c y o f a b o u t 1.52

139

.

A r y l m e t h y l r a d i c a l s at 7 7 K s h o w

e m i s s i o n p r o p e r t i e s w h i c h d e p e n d u p o n i n t r a m o l e c u l a r twist' 4 0 R e a c t i o n s o f 1 - n a p h t h y l m e t h y l radicals'

4'

.

, r a d i a t i v e and n o n -

radiative decay o f electronically excited ketyl radicals o f several s u b s t i t u t e d b e n z o p h e n o n e k e t y l r a d i c a l s in p o l y ( v i n y 1 a l c o h o l ) f i l m s at 7 7 K l 4 * .

intersystem crossing efficiencies in biradicals as

affected by s p i n o r b i t

and m a g n e t i c field e f f e c t s u p o n

t h e l a t t e r h a v e a l l been m e a s u r e d by nanosecond absorption'"

transient UV

.

The photochemistry o f pyrenylmethylphosphonium salts shows p h o t o i n d u c e d s o l v o l y s i s by a h e t e r o l y t i c s c i s s i o n t o g i v e t h e a l k o x y m e t h y l p y r e n e and t r i p h e n y l p h o s p h i n e c o m p o u n d s i n alcohols'

2.1

".

F l e c t r o n T r a n s f e r R e m o n s and Fx-lexes.

-

New aspects o f

the role of solvent i n photoinduced electron transfer in polar s o l u t i o n s h a v e been analsyed i n d e t a i l by K a k i t a n i and Mataga'"

.

The effect o f solvent o n the dipolar contribution t o exciplex s t a b i l i t y has b e e n s h o w n by m e a s u r e m e n t s o n a r a n g e o f u n s a t u r a t e d c o m p o u n d s o n t h e d e a c t i v a t i o n o f t h e S, n a p h t h a l e n e derivatives1".

state of several

Q u e n c h i n g o f e x c i m e r s o f p y r e n e and

9 , l O - d i c h l o r o a n t h r a c e n e by e l e c t r o n d o n o r s i n d i f f e r e n t s o l v e n t s is less e f f i c i e n t t h a n f o r t h e parent

molecule^'^^.

The

thermodynamics o f formation of t h e perylene/Ag+ exciplex shows that

12

Photochemistry

q u e n c h i n g by t h i s r o u t e i s e s s e n t i a l l y e n t r o p y driven’”. Intramolecular exciplex formation occurs i n 6-(2’,3’butenoxy ) m e t h y l - I - c y a n o n a p h t h a l e n e ’ ” . T i m e r e s o l v e d s p e c t r o s c o p i c t e c h n i q u e s a r e w e l l suited t o t h e study o f e l e c t r o n t r a n s f e r and s o l v e n t e f f e c t s . and energy r e s o l v e d d e c a y m e a s u r e m e n t s

Both f l u o r e s c e n c e

show orientational

isomerization takes place in t h e excited singlet state of electrondonor acceptor complex o f p-xylene with 1 , 2 , 4 , 5 t e t r a c y a n ~ b e n z e n e ’ ~.’ T h e d y n a m i c s o f an e x c i t e d t r a n s - s t i l b e n e o l e f i n contact pair i n v o l v e s s o l v e n t and salt e f f e c t s on back e l e c t r o n t r a n s f e r and ion pair s e p a r a t i o n l S 2

.

Subpicosecond

spectroscopy shows that relaxation processes in iron ( 1 1 1 ) t e t r a p h e n y l p o r p h i n e o c c u r o n f e m t o s e c o n d t i m e scales’ 5 3

.

The

t r a n s i e n t s o l v a t e d e l e c t r o n g e n e r a t e d by p h o t o i o n i z a t i o n o f p h e n o l shows s p e c t r a l s h i f t s i n d i f f e r e n t s o l v e n t s and e v i d e n c e i s produced f o r a l o n g l i v e d solvated e l e c t r o n - i o n p a i r l S 4 .

The

i n f l u e n c e of s o l v e n t r e l a x a t i o n o n e l e c t r o n t r a n s f e r r a t e s h a s been examined i n rigid solution’s5 and t h e r o l e o f i o n pairs i n e l e c t r o n d o n o r - a c c e p t o r s y s t e m s m a d e in a f r u i t f u l c o m p a r i s o n o f picosecond s p e c t r o s c o p y and C I O N P studies’ 5 6

.

A very

detailed investigation

has been r e p o r t e d on t h e d i s a p p e a r a n c e o f t h e t w i s t e d c h a r g e transfer state ( T I C T ) of p - d i m e t h y l a m i n o b e n z o n i t r i l e by p i c o - and nanosecond

spectrosc~py’~~ I ’

and p h a s e m o d u l a t i o n

f l u o r o m e t r y h a s a l s o been used t o study s o l v e n t c a g e r e o r i e n t a t i o n around t h e e x c i t e d s t a t e o f e t h y l a m i n o - 9 - m e t h o x y - 2 - c h l o r o - 6 - a c r i d e in g l y e r o 1 1 5 9 . A number of similar

s t u d i e s h a v e a l s o b e e n made.

These

include the dynamic Stokes shift of trans-4-dimethylamino-4’cyanostilbenel

6o

, d i f f e r e n t r e l a x a t i o n m e c h a n i s m s i n a p r o t i c and

p r o t i c s o l v e n t s o f ~-bJ,fi-dimethylamino-benzonitrileand related

-N , N_-dialkylaniline

compounds’ 6 1 , t h e d u a l f l u o r e s c e n c e o f 4 - N ,y-

d i m e t h y l a m i n o b e n z o n i t r i l e r e l a t e s t o h y d r o g e n bonding and t h e red

shift i s d u e t o t h e t w i s t e d c o n f o r m a t i o n ’ 6 2 , and s o l v a t o c h r o m i c e f f e c t s i n t h e f l u o r e s c e n c e o f 2 - a m i n o a n t h r a c e n e and tj.N_-dimethyl -2-aminoanthracene where a detailed comparison with different m o d e l s i s g i ~ e n ” ~ . T h e g i a n t d i p o l e m o m e n t d e v e l o p e d by 4 d i e t h y l a m i n o - 4 ‘ - n i t r o s t i l b e n e o n e x c i t a t i o n i n s o l u t i o n and p o l y m e r films g i v e s r i s e t o p r o p e r t i e s w h i c h h a v e i n t e r e s t i n g t e c h n o l o g i c a l p o s s i b i l i t i e s i n o p t o - e l e c t r o n i c s ’ “ . A c o m p a r i s o n of e x c i t e d s t a t e d i p o l e m o v e m e n t s and p o l a r i z a b i l i t i e s w h i c h a r e e s t i m a t e d f r o m solvent s p e c t r a l s h i f t s h a v e been c o m p a r e d w i t h t h o s e d e t e r m i n e d by

I: Photophysical Processes in Condensed Phases electro-optical measurements’ 6 5

.

13

D u e t o t h e u n c e r t a i n t i e s involved

i n t h e a p p l i c a t i o n o f t h e f o r m e r m e t h o d s u c h c o m p a r i s o n s a r e very significant.

T h e f l u o r e s c e n c e s p e c t r a o f 4 and 4 , 4 ‘ - n i t r o -

d e r i v a t i v e s o f DPH a r e r e m a r k a b l y d e p e n d e n t o n s o l v e n t polarity’“. I n d o l e d e r i v a t i v e s h a v e been studied i n s o l u t i o n and t h e v a p o u r p h a s e and t h e ’La-’Lb

l e v e l i n v e r s i o n e f f e c t s a r e used t o

account for the o b s e r ~ a t i o n s ’ ~ ~ A p a p e r by Suppan17’

16’.

draws attention t o electrostatic

interaction effects on condensed phase photoinduced electron t r a n s f e r and t h e need t o t a k e a c c o u n t o f t h e f a c t t h a t s o l v e n t i s not i n r e a l i t y a u n i f o r m d i e l e c t r i c m a t e r i a l .

Pressure effects o n

e x c i p l e x f o r m a t i o n h a s been e x e m p l i f i e d i n t h e pyrene-pc y a n o b e n z e n e system’ 7’

.

Ternary electron donor acceptor complexes

a r e f o r m e d and in t h e c a s e o f anthracene-tetracyanoethylene g i v e s rise t o (DO+ 1 dimer radical cations17*.

Laser flash photolysis

shows that perylene i n acetonitrile undergoes three distinct electron transfer processes, P:

+

( i ) g i v e s P’ + MeCN:,

(iii g i v e s

P 7 , and ( i i i ) t r i p l e t - t r i p l e t i n t e r a c t i o n y i e l d s P:

and P T 1 7 3 .

T h e d u a l f l u o r e s c e n c e o f 4 , 4 ‘ - d i m e t h y l a m i n o - and

4,4‘-diaminophenylsulphone is a consequence of d-orbital

participation in intramolecular charge separation i n polar

solvent^'^'.

E x c i p l e x promoted e l e c t r o n t r a n s f e r h a s a l s o b e e n

e x a m i n e d i n 1 - ( p h e n y l a m i n o1-3- ( 9 a n t h r y l ) propanes’ ”

.

T h e barriei

d u e t o s o l v e n t r e o r g a n i s a t i o n h a s been c o n s i d e r e d i n t h e i n t e r p r e t a t i o n o f s o l v e n t e f f e c t s o n p h o t o i n d u c e d e l e c t r o n transfei in the rigid bichromophoric systems involving methoxybenzene as d o n o r and a variety o f e l e c t r o n a c c e p t o r groups’ 7 6 .

Intramoleculal

electron transfer involving porphyrins bearing trinitroaryl a c c e p t o r g r o u p s h a s been studied’ 7 7 .

T h e p h o t o p h y s i c s o f polarizec

enones in various solvents shows that intramolecular charge t r a n s f e r a l s o o c c u r s in t h e s e m o l e c u l e s 17’. Solute-solvent exciplexes are involved i n photoinduced f o r m a t i o n o f r a d i c a l i o n s o f 4-tJ,N-dimethylaminobenzonitrile and r e l a t e d c~rnpounds’~’.

T h e c o r r e s p o n d i n g t r i p l e t s t a t e s d o not

appear t o form exciplexes.

Radical ion formation from l-anisyl-

2 , 2 - d i p h e n y l b r o m i d e i n a c e t o n i t r i l e and a c e t i c acid h a s a l s o b e e n examined i n d e t a i l l e 0

.

Photo-induced methoxy substitution i n 3 -

n i t r o a n i s o l e and 3 , 5 - d i n i t r o a n i r o l e o c c u r s via a n u c l e o p h i l e C a t o m r e a c t i o n w h i c h i s t h e r a t e d e t e r m i n i n g step’”.

+

The

d y n a m i c s o f t r a n s i e n t i o n p a i r s and r a d i c a l pairs i n a n t h r a c e n e derivative/ tetranitromethane systems have been examined a s a

rin!

Photochemistry

14 f u n c t i o n o f s o l v e n t and salt e f f e c t s by t i m e r e s o l v e d spectroscopy’82.

The effect of solvent structure on t h e hydration

d y n a m i c s o f e l e c t r o n s formed f r o m t h e f l u o r e s c e n t p r o b e 6 - p t o l u i d i n e - 2 - n a p h t h a l e n e s u l p h o n a t e has been i n v e s t i g a t e d i n H 2 0 / E t O H

mixed s o l v e n t systernsle3.

A c l u s t e r o f t h r e e or f o u r w a t e r

m o l e c u l e s is found t o b e t h e e l e c t r o n a c c e p t o r i n t h i s case. TICT states occur i n t h e intramolecular quenching o f fluorescence in a m i n o - c o u m a r i n s w h e r e s o l v e n t e f f e c t s s h o w d e v e l o p m e n t o f a large dipole in the excited s t a t e t E 4 .

R e s o r u f i n i n t h e excited

s t a t e i n t e r a c t s w i t h a n i o n s a s s h o w n by m o l e c u l a r r e o r i e n t a t i o n measurements’”.

Aggregates of ions are probably involved in

q u e n c h i n g o f t h e f l u o r e s c e n c e o f t h e pyrene-H,pt-dimethylaniline e x c i p l e x in s o l v e n t s o f l o w e l e c t r i c constant“‘.

Picosecond

dynamics of proton transfer within amine-ketone acid-base pairs, including dimethylaniline

-

a n t h r a q u i n o n e h a s been studied”’

.

P h o t o i n d u c e d i s o m e r i z a t i o n and c h a r g e t r a n s f e r i n t r a n s - 1 , 2 - b i s ( l -

-

methyl-4-pyridine)

e t h y l e n e salts’”,

dichloroanthroquinone

photoreduction o f 1,8-

by t r i e t h y l a m i n e 1 8 9 and a n t h r a q u i n o n e by all occur via exciplexes.

t r i e t h y l a m i n e i n acetonitrile’”

Switching o f p h o t o c h e m i c a l r e a c t i o n p a t h w a y s i n a s e r i e s o f b i c h r o m o p h o r i c s p e c i e s , ~ - C w - ( ~ - n i t r o p h e n o x y l ) a l k y l la n i l i n e s f r o m a photo-Smiles rearrangement to a photoredox reaction with The effects o f electron

i n c r e a s i n g c a r b o n c h a i n length’”.

transfer processes i n heterogeneous photochemistry in various systems has been r e v i e w e d t g 2 .

2.7 Dves and Related

SYS-

-

A

m a j o r r e a s o n f o r an i n t e r e s t i n

dyes is the search for continuous improvement in t h e design o f tuntable lasers.

Amplified spontaneous emission is observed from

3 - h y d r o x y f l a v o n e and a r e l a t e d l a s e r d y e d u e t o a r a p i d t a u t o m e r i s m which occurs in t h e ground stateIg3.

Quaterphenyl dyes are

s u i t a b l e as U V l a s e r d y e s p a r t i c u l a r l y s u b s t i t u t e d

p-

q ~ a t e r p h e n y l s ” ~ and ring b r i d g e d q u a t e r p h e n y l ~ ’. ~ ~A very d e t a i l e d study has been m a d e o f t h e s p e c t r a l and t e m p o r a l fluorescence o f 4-dicyanomethylene-2-methyl-6-dimethylaminostyryl4H-pyran ( D C M ) l g 6 .

A n u m b e r o f e x p l a n a t i o n s a r e put f o r w a r d t o

explain t h e d u a l f l u o r e s c e n c e i n c l u d i n g a g g r e g a t i o n and s o l v e n t exciplex formation.

Q u a n t u m c o u n t i n g by l a s e r d y e s w h i c h c o v e r a

broad s p e c t r a l r a n g e i n c l u d i n g t h e n e a r I R can be used t o extend the range for correction o f fluorescence spectra up t o 7 0 0 - 7 8 0 nm

197

. I n v e s t i g a t i o n s o f b e n z o p y r y l i u m s a l t s C Z 1 4 4 and C Z 6 8 2 i n

I: Photophysical Processes in Condensed Phases CH2C12

s h o w t h a t Of > 0 . 5 .

15

Excited state absorption d a t a i n

l a s e r d y e s at t h e X e C l w a v e l e n g t h h a v e a l s o been publi~hed'~'. A b s o r p t i o n and f l u o r e s c e n c e spectra o f 7-aminocoumarin d e r i v a t i v e s h a v e been recorded'" i n c l u s i o n c o m p l e x e s w i t h B-

and t h e photophysics o f c o u m a r i n

and y - c y c l o d e x t r i n s investigated'".

Solvent e f f e c t s on t h e p h o t o p h y s i c a l behaviour o f pyrrolocoumarin d e r i v a t i v e s a r e similar t o t h o s e o n t h e psorolens2".

Vibronic

exciton bands and t h e absorption spectra o f Eosin Y d i m e r s h a v e been analysed theoretically and compared W i t h e x p e r i m e n t a l data202

.

Picosecond spectroscopic s t u d i e s h a v e been m a d e o n t h e i o n i c

.

photodissociation d y n a m i c s o f m a l a c h i t e g r e e n l e u ~ o c y a n i d e ~ ' ~ T h e lowest s t a t e p r o d u c e s i o n s w i t h i n 0.1 t o 0.5 n s w h i l s t f o r higher s t a t e s 6 - 1 3 ps a r e sufficient for t h e development o f c h a r g e separation.

T h e photophysics of c r y s t a l violet i n a series o f n-

a l c o h o l s 2 0 4 and t h e picosecond bleaching behaviour of c r y s t a l violet in t h e ground and excited s t a t e s between 4 5 5 and 7 2 0 nm'" are l a s e r relevant studies.

Picosecond spectroscopy o f

i n t r a m o l e c u l a r hydrogen bonding o f 4 , 4 ' , 7 , 7 ' - t e t r a m e t h y l i n d i g o is an interesting s t r u c t u r a l study206

.

T h e f l u o r e s c e n c e and

absorption spectra o f t h i o f l a v i n T a r e strongly affected by freezing in w a t e r d u e t o d i m e r i z a t i o n o f d y e s t u f f i o n s 2 0 7 . F l u o r e s c e n c e a s w e l l as t r i p l e t s t a t e properties h a v e been m a d e i n

.

l I 4 - U C 2 -( 5 - p h e n y l - o x a z o l y l )I b e n ~ e n e ~ ~ ' T h e t e m p e r a t u r e d e p e n d e n c e o f t h e l i m i t i n g f l u o r e s c e n c e anisotropy of P O P O P in c e l l u l o s e a c e t a t e film has a l s o been measured'".

The influence o f

solvent o n t h e absorption spectra and excited deactivation m e c h a n i s m o f U V stabilizers o f t h e 2 - ( h y d r o x y p h e n y l ) b e n z o t r i a z o l e class i s o f c o n s i d e r a b l e t e c h n i c a l interest'".

The n a t u r e o f t h e

red f l u o r e s c e n c e f r o m t h e coloured m e r o c y a n i n e f o r m o f 1 , 3 , 3 trimethyl-6'-nitrospiro[indoline-2,2'-

12Hlbentopyranl in s o l u t i o n

and polymer f i l m s has been examined and t h e extent o f t a u t o m e r i z a t i o n t o a c o l o u r l e s s f o r m assessed2".

The decay o f t h e

excited J a g g r e g a t e of p s e u d o i s o c y a n i n e i o d i d e has been found t o occur w i t h a decay t i m e of 25 ps2l2. 2-Phenyl-3- i n d o l o c y a n i n e d y e s show d o u b l e e x p o n e n t i a l d e c a y t i m e s indicating t h e involvement o f a photoinduced cis-trans isomerization2'3

.

Excited s t a t e r e l a x a t i o n

processes of m o n o m e r i c and aggregated d i e t h y l t h i a c a r b o c y a n i n e iodide h a v e been studied by picosecond a b s o r p t i o n spectra'". Aggregated states h a v e fast and efficient r a d i a t i o n l e s s d e c a y processes w h i c h depend on very strong d i p o l e - d i p o l e interactions which a r e enhanced by t h e i n f l u e n c e o f t h e solvent d i p o l e moment.

16

Photochemistry F l u o r e s c e n c e l i f e t i m e s and e f f e c t s o f a g g r e g a t i o n o f d y e s o n

microcrystals o f silver bromide give information directly relevant to the improvement o f photographic processes215

.

P h o t o p h y s i c a l and

photochemical properties o f common dyes i n amphiphilic media like

S O S and C T A B s h o w that t h e d y e s a r e l o c a t e d at c o n s i d e r a b l y hydrated s i t e s 2 1 6 . A x i a l l i g a t i o n s i g n i f i c a n t l y a f f e c t s t h e f l u o r e s c e n c e of tetrakispheny1porphyrins2’

and f o r s o m e p o r p h y r i n s and I X

m e t a l l o p o r p h y r i n s l u m i n e s c e n c e and p h o t o d i m e r i z a t i o n h a v e been reported2”

.

Very s h o r t f l u o r e s c e n c e l i f e t i m e s h a v e been m e a s u r e d

f o r i r o n , n i c k e l and c o b a l t p h t h a l o c y a n i n e s

(

2 - 3 ps 1 2 ’

.

P h o t o r e d u c t i o n o f i n d i g o d y e s by e l e c t r o n d o n o r s s h o w s t h e involvement o f o n e or two electron transfer reactions which occur as a c o n s e q u e n c e o f e x c i t e d s t a t e q u e n c h i n g 2 2 0 .

Quenching of

f l u o r e s c e n c e h a s b e e n used t o f o l l o w s u c h p h o t o i n d u c e d e l e c t r o n t r a n s f e r r e a c t i o n s o f r h o d a m i n e B w i t h s e v e r a l r e d o x q u e n c h e r s in films o f p o l y ( N - - v i n y l p y r r o l i d o n e ) 2 2 1

.

Electron transfer efficiency

d e p e n d s o n t h e r e d o x p o t e n t i a l o f q u e n c h e r and c a n o c c u r at distances up t o 1 5 8

.

7.3 Pho-tation

and R e b t e d Processes,

-

These

rearrangements provide model systems for t h e examination of primary processes but a r e n o w s h o w i n g i n c r e a s i n g p r o m i s e f o r e x p l o i t a t i o n in the design o f various electrooptical devices.

S t a t m a n and

Robinson222 have analysed the molecular dynamics of cis-trans i s o m e r i z a t i o n and d e t a i l s o f t h e i n f l u e n c e o f s o l v e n t s t r u c t u r e . Excluded v o l u m e e f f e c t s and t h e d i f f e r e n t s i z e s o f

cis

and t r a n s

i s o m e r s h a v e b o t h been t a k e n i n t o a c c o u n t in t h i s m o d e l .

The

isomerization o f alkenylanthracenes in solution has rate constants w h i c h a r e a f f e c t e d by s o l v e n t

The alternative Grote-

H y n e s and K r a m e r s m o d e l s f o r t h i s t y p e o f p r o c e s s a r e c o m p a r e d w i t h t h e experimental data. B e c k e r and his c o w o r k e r s h a v e i n v e s t i g a t e d t h e p h o t o i s o m e r i z a t i o n o f p r o t o n a t e d and u n p r o t o n a t e d n - b u t y l a m i n e S c h i f f b a s e s o f v a r i o u s r e t i n a l ~and ~ ~ a~l s o h a v e r e p o r t e d t h e s p e c t r o s c o p y and p h o t o i s o m e r i z a t i o n o f a s e r i e s o f p o l y f e t h y l e n e g l y c o l ) p e p t i d e S c h i f f bases o f 1 1 - c i s - r e t i n a 1 2 2 s . T h e picosecond d y n a m i c s o f b a r r i e r c r o s s i n g in t h e conformational change of 1 , l ‘ - b i n a p t h y l in a series o f alcohol solvents shows excellent agreement with t h e Kramer’s model for i n t e r m e d i a t e and high f r i c t i o n regimes226

.

Deviation from t h e


17

Kramer's m o d e l may b e d u e t o e f f e c t s o t h e r t h a n n o n - M a r k o v i a n friction.

The fluorescence properties o f t h e conformational isomer

mixtures of trans-2-styryl-naphthalene provides further evidence for different radiative decay properties o f t h e two rotamers o f t h i s compound227

.

T h e r e s o l u t i o n and c h a r a c t e r i s a t i o n h a s been

m a d e o f t h e r o t a m e r s o f 1-phenyl-2- ( 2 - a n t h r y l ) ethylene2"

and t h e

three conformers i n case o f trans-di(2-napthyl)ethyleneaa9

.

A

c o m b i n e d p h o t o c h e m i c a l and UV a b s o r p t i o n s t u d y c o n d u c t e d i n r i g i d media elucidates t h e role o f rotamers in a z o n a p h t h a l i n e ~ ~ ~ ~ . Dynamic solvent effects on t h e large amplitude isomeritation rates 231 , 2 - ( 2 ' - p r o p e n y l ) a n t h r a c e n e , and (=)-2-(but-

of 2-vinylanthracene 2'-en-2'yl)

anthraceneZ3'

coworkers.

T h e p h o t o i s o m e r i z a t i o n o f t h e S c h i f f b a s e o f 11-cis-

h a v e been r e p o r t e d by Barbara and h i s

r e t i n a l h a s been e x a m i n e d o v e r t h e u n u s u a l l y e x t e n s i v e ps t o 1 s

or l o n g l i v e d t r a n s i e n t s w e r e d e t e c t e d

time range233.

No t r i p l e t s

in t h i s study.

The photochemical trans-cis isomerization o f 1,2-

-

U ( h e t e r o a r y 1 ) e t h y l e n e and 1 , 2 - u ( p y r a z i n y l l e t h y l e n e s h o w s t h a t t h e q u a n t u m yield o f t r a n s

c i s conversion increases with solvent

polarity b e c a u s e o f t h e p r o x i m i t y o f ' ( n , I T * ) and states234.

'(IT, n * )

The triplet state i s involved i n t h e direct

i s o m e r i z a t i o n i n c o n t r a s t w i t h s t i l b e n e w h i c h only i n v o l v e s c h a n g e s occurring in t h e singlet manifold.

T h e fluorescence of trans-

s t i l b e n e in l i q u i d e t h a n e g i v e s b a r r i e r c r o s s i n g r a t e s a s a function

of

p r e s s u r e in t h e r a n g e 0 t o 170 atmZ3'.

r a t e o c c u r s at 1 2 0 a t m .

A peak

Femtosecond pulse excitation o f

in t h e

cis-

s t i l b e n e i n h e x a n e at 312.5 n m y i e l d s a t r a n s i e n t a b s o r p t i o n i n t h e visible with a 1.35 ps lifetime236.

The kinetics show a n evolution

which is interpreted as resulting from the intermediacy o f a s t i l b e n e 'phantom' s t a t e w i t h a l i f e t i m e o f 3 2 2 p s .

Fluorescence

and i s o m e r i z a t i o n i n 4 , C ' - d i a m i n o s t i l b e n e a r e m a r k e d l y a f f e c t e d by s o l v e n t viscosity w h i c h i n f l u e n c e s t h e e n e r g y barrier237

.

Photoinduced electron transfer competes w i t h phtoisomerization i n the quaternary salts o f 4-nitro-4'-azastilbene quinolinium analogues238.

and t h e i r

P h o t o i s o m e r i t a t i o n o f 3-styryl-2' , 4 * ,6'-

trisopropylstilbene shows t h e steric effects o n t h e location o f electronic excitation at groups within t h e molecule239. Trans

---*

c i s i s o m e r i z a t i o n o f 4 - s u b s t i t u t e d 4 - a z a s t i l b e n e s t a k e s p l a c e by a s i n g l e t m e c h a n i s m and t r i p l e t s t a t e s h a v e a l s o b e e n ~haracterised'~'. c i s isomerization

A n e w mechanism has been

o f c y a n i n e dyesz4'

.

proposed f o r t h e t r a n s -

Picosecond spectroscopic

m e t h o d s h a v e m a d e it p o s s i b l e t o o b s e r v e p h o t o i s o m e r s o f s h o r t

Photochemistry

18 chain cyanine dyes.

A l s o s o l v e n t d e p e n d e n t b a r r i e r h e i g h t s have

been e s t a b l i s h e d i n e x c i t e d s t a t e s o f d i e t h y l t e t r a m e t h y l i n d o carbocyanine iodide in n-alcohol solution242

.

S o l v e n t s t r u c t u r e and d y n a m i c s o f t h e e x c i t e d - s t a t e tautomerization o f 7-azaindole/alcohol complexes are explained as proton a r i s i n g f r o m t r a n s f e r r e a c t i o n s w h i c h r e q u i r e s o l v e n t involvement2‘

.

It has b e e n proposed t h a t c o n c e n t r a t e d s o l u t i o n s o f a z o b e n z e n e can be used f o r a ~ t i n o m e t r y ~ ~Q u~ a.n t u m y i e l d s o f t h e p h o t o i s o m e r i z a t i o n needed f o r t h i s p u r p o s e a r e f u l l y q u o t e d i n t h e paper.

. . 2.4 F l e c t r o n i c F x c i t a t i o n Enerav T r a n s f e r .

-

T h e n u m b e r o f papers

d e a l i n g w i t h t h e o r y and s i m p l e m o l e c u l e s a p p e a r t o h a v e d e c l i n e d o v e r r e c e n t years.

An e x c e p t i o n t o t h i s s t a t e m e n t i n v o l v e s

b i o l o g i c a l s y s t e m s and it i s i n b i o c h e m i s t r y t h a t m o s t s i g n i f i c a n t recent w o r k o n e l e c t r o n i c e x c i t a t i o n e n e r g y t r a n s f e r h a s been d o n e . S o m e r e c e n t e x a m p l e s w i l l be m e n t i o n e d i n a l a t e r s e c t i o n o f t h i s review. T w o very m a t h e m a t i c a l t r e a t m e n t s o f e n e r g y t r a n s f e r i n condensed m e d i a d e a l w i t h e x c i t o n s and phononsZ4’ ’ 2 4 6 . C l o s e l y related i s a p a p e r by P a r r i s and Kenkre247 w h i c h e x t e n d s e a r l i e r t h e o r y t o c o v e r l o n g r a n g e t r a p p i n g i n v o l v i n g e x c i t o n m i g r a t i o n and r e l a t e s t h i s t o t h e s t r e n g t h and r a n g e o f t h e c a p t u r e process.

A

detailed k i n e t i c a n a l y s i s h a s been m a d e o f i n t e r m o l e c u l a r m i g r a t i o n o f e x c i t a t i o n e n e r g y and q u e n c h i n g

in regular lattices248.

An

i n t e r e s t i n g i n v e s t i g a t i o n h a s been m a d e o n e n e r g y t r a n s f e r i n s y s t e m s w i t h r e s t r i c t e d g e o m e t r i e s s u c h a s e x e m p l i f i e d by m i c e l l e s , z e o l i t e s , p o l y m e r c o i l s , and p o r o u s glass249.

Deviations from

F o r s t e r t h e o r y , w h i c h a s s u m e s a n i n f i n i t e array a r e f o u n d i n t h e s e finite systems.

A

computer simulation o f t h e effects o f non-random

o r i e n t a t i o n on t i m e d e p e n d e n t e x c i t a t i o n p r o b a b i l i t y h a s a l s o been c o n ~ t r u c t e d ~ ~ ’ .Burshtein2”

h a s prepared a r e v i e w o f e n e r g y

t r a n s f e r k i n e t i c s i n d i s o r d e r e d s y s t e m s and a l s o p r o d u c e d a p a p e r w h i c h d i s c u s s e s q u a n t u m y i e l d s i n t e r m s o f M a r k o f f i a n and nonMarkoffian theories for luminescence o f solids252.

F o r fluid

s y s t e m s a k i n e t i c t h e o r y o f e x c i t a t i o n t r a n s f e r b e t w e e n d o n o r and a c c e p t o r s , w h e r e r e a c t i o n p r o b a b i l i t y i s m o d u l a t e d by t r a n s l a t i o n a l d i f f u s i o n s , h a s been submitted t o n u m e r i c a l analysis253

.

An e x p e r i m e n t a l i n v e s t i g a t i o n h a s been m a d e o f e n e r g y t r a n s f e r 254 for m e s i t y l e n e / 9 , 1 0 - d i p h e n y l a n t h r a c e n e , 2,3-


19

d i m e t h y l n a p h t h a l e n e l a n t h r a c e n e in mixed

c r y s t a l s 2 5 5 , and aromatic

.

hydrocarbons t o tetra cyanoquinone anions in MeOH

Investigation of r a d i a t i v e energy transfer in t h e case o f pyrene and 9 , l O - d i p h e n y l a n t h r a c e n e has indicated that t h i s process c a n provide t h e dominant m e c h a n i s m for t r a n s f e r in many s y s t e m s 2 5 7 . Fluorescence depolarization o f r h o d a m i n e 6 6 in g l y c e r o l has been used t o test t h e theories o f t h r e e d i m e n s i o n a l excitation transport theory2”.

Transfer between r h o d a m i n e 6 6 ( d o n o r ) and m a l a c h i t e

green ( a c c e p t o r ) has been followed by picosecond t i m e resolved single photon counting and donor fluorescence decay examined by a theoretical function including t r a n s l a t i o n a l d i f f u s i o n 2 S s .

The

simple Forster equation considering diffusion is found t o over estimate t h e critical d i s t a n c e for transfer. Intramolecular electronic energy transfer in bichromophoric molecules consisting o f t w o coumarins linked by a variable number of m e t h y l e n e g r o u p s has been investigated by multi-frequency phase modulation fluorometry260

.

Picosecond fluorescence spectroscopy

shows that fast energy transfer occurs in phycocyanin 6 1 2 2 6 1

2.5 P o l v w i c S v s t e m s .

-

.

Since polymer systems are extensively

discussed elsewhere in this volume only selected examples w i l l b e quoted which indicate h o w polymeric structures c a n i n f l u e n c e photophysical phenomena.

For e x a m p l e , fluorescence polarization

has been used to monitor polymer cure in resin mixtures w h e n a f l u o r o p h o r e , k-(2-hydroxyalkyl) d e r i v a t i v e o f 4-aminonaphthalimide. is u s e d 2 6 2 .

PolyC2- ( 9 - c a r b a z o y l l e t h y l methacrylatel f i l m s s h o w

monomer fluorescence from carbazoyl chromophores but no d e t e c t a b l e excimer emission is seen even in t h e solid s t a t e 2 6 3 .

Highly

efficient sensitized photoconductivity by electron acceptor d o p i n g shows effective electronic excitation migration can occur through carbazole chromophores.

Formation o f an exciplex by pyrene and

dimethylaniline has been used t o probe end t o end cyclisation o f polystyrene in a variety o f s o l v e n t s 2 6 4 .

Solvent site

inhomogeneity i s shown in polymethyl m e t h a c r y l a t e g l a s s e s by t h e extent o f t h e formation o f TICT states o f

.

same probe shows that t h e free d i r n e t h y l a m i n o b e n ~ o n i t r i l e ~ ~The ~ volume in polyhydroxyethyl m e t h a c r y l a t e i s l e s s than t h a t in PHHA. Electronic energy transfer in p o l y ( 2 - v i n y l n a p h t h a l e n e ) and polystyrene shows energy m i g r a t i o n i s not limited t o nearest neighbour rings266.

Short r a n g e interactions other t h a n dipole-

d i p o l e interactions are involved.

F l u o r e s c e n c e and energy

Photochemistry

20

m i g r a t i o n i n a l t e r n a t i n g and r a n d o m c o p o l y m e r s o f 2-vinyln a p h t h a l e n e and m e t h y l m e t h a c r y l a t e o r m e t h a c r y l i c acid s h o w s a l t e r n a t i n g c o p o l y m e r s h a v e e s s e n t i a l l y n o e x c i m e r e m i s s i o n and 267 The random exhibit a monoexponential fluorescence decay

.

c o p o l y m e r s h o w s e x c i m e r e m i s s i o n and a t h r e e e x p o n e n t i a l d e c a y . Q u e n c h i n g o f t h e f l u o r e s c e n c e o f acrylamidomethylthionine c o p o l y m e r s by Fe2+ and Fe3+ s h o w s Fe2+ f o r m s an a d d u c t t o g i v e t h e 268 semithionine radical which subsequently disproportionates

.

Fluorescence quenching of phenanthryl groups covalently linked t o p o l y e l e c t r o l y t e s h a s a l s o b e e n studied269

.

Such examples

c o n s t i t u t e u s e f u l m o d e l s f o r c o m p l e x b i o l o g i c a l systems. of the 6 s

-+

The rate

trans photoisomerization o f polymer azoaromatic

p o l y i m i d e i n c o n c e n t r a t e d H SO d i f f e r e n t s t r u c t u r e s involv:d2+'.

shows that t h e rate depends o n the P y r e n e has been used as a

photophysical probe for intermolecular interactions o f watersoluble polymers in dilute solution271

.

P e r y l e n e a g g r e g a t e s in

PMMA polymer matrices shows that there is a distribution o f ground state pair combinations272. 2 . 6 C o l l o i d a l and H e t e r o a e n e o u s S v s t e m a

-

The study o f photophysics

in colloidal systems i s now o n e of t h e most active areas o f photochemistry.

P r o b a b l y t h e m o s t n o t a b l e a c h i e v e m e n t so f a r

has been t h e i n f o r m a t i o n p r o v i d e d o n t h e n a t u r e o f c o l l o i d s and their properties. T h e f l u o r e s c e n c e o f 6 - d o d e c y l - 2 - n a p h t h o l i n m o n o l a y e r s at air273

water interfaces is the simplest o f all heterogeneous systems

.

P y r e n e and 1 , 3 - d i - l - p y r e n y l p r o p a n e h a v e b e e n used a s f l u o r e s c e n c e probes in rapidly f r o z e n w a t e r c o n t a i n i n g 0.5 t o 5 % ( v / v ) acetone274.

The liquid acetone forms domains within t h e ice

c r y s t a l and a n o t h e r p r o b e , 1 - a n i l i n o n a p h t h a l e n e s u l p h o n a t e , s h o w s that t h e amount o f water in these domains is less a s t h e temperature decreases.

S t r u c t u r a l d o m a i n s i n lipid m e m b r a n e s h a v e

been e x a m i n e d by m e a s u r e m e n t o f d e c a y t i m e s o f DPH using p h a s e and modulation techniques275.

Only i n s p e c i a l c a s e s c a n t h e c o -

e x i s t e n c e o f g e l and fluid p h a s e s be r e s o l v e d s i n c e t h e p r e c i s i o n r e q u i r e d f o r t h e d e c a y t i m e s i s very exacting.

Biexponential

d e c a y s a r e a l s o found f o r t h e l , l t - d i a l k y 1 - 3 , 3 , 3 ' , 3 ' - t e t r a m e t h y l i n d o c a r b o c y a n i n e d y e s ( N = 1 2 , 18 and 2 2 ) in a variety o f l i p i d bilayer membranes276.

The sensitivity o f t h e fluorescence lifetime

o f l-palmitoyl-2C2-[4-(6

phenyl-trans-l,3,5-hexatrienyl)

phenyllcarbonyll- 3 - s n - p h o s p h a t i d y l c h o l i n e

(DPH-PC)

t o environment


21

h a s b e e n used t o m o n i t o r l i p i d m i x i n g and p h a s e s e p a r a t i o n d u r i n g membrane fusion2??.

T h e e f f e c t s o f C a 2 + h a s a l s o been e x a m i n e d .

M o l e c u l a r r e l a x a t i o n f l u o r e s c e n c e m e t h o d s h a v e been used t o a n a l y s e t h e n a t u r e and d y n a m i c s o f a m p h i l i c m o l e c u l e s absorbed i n t h e p o l a r r e g i o n o f a p h o s p h o l i p i d b i l a ~ e r ~ ~ ’ .T h e power o f t h e m e t h o d i s demonstrated

in s h o w i n g t h a t t h e polar s u r f a c e i s h i g h l y m o b i l e and

d i p o l a r r e l a x a t i o n i s rapid. The theory of the concentration depolarization of luminescent molecules embedded in a homogeneous media with orientational c o n s t r a i n t s has been d e v e l o p e d 2 7 9 and t h e i n f l u e n c e o f m o l e c u l a r organisation on t h e photophysical properties of two a l k y l c y a n o d i p h e n y l s examined2”.

T h e l a t t e r s y s t e m s h o w s both head

t o head and t a i l t o head e x c i m e r s . F l u o r e s c e n c e d e c a y t i m e m e a s u r e m e n t s h a v e been used t o o b s e r v e c l u s t e r i n g in m i c r o e m u l s i o n s near t h e c r i t i c a l point2”.

The

d y n a m i c q u e n c h i n g o f f l u o r e s c e n c e i s used t o e s t i m a t e s i z e s o f t h e droplets.

F l u o r e s c e n c e probing h a s a l s o been used t o s t u d y

s u r f a c t a n t o x y g e n a t i o n i n a q u e o u s s o l u t i o n s o f mixed i o n i c micelles282.‘ k c r i d i n e f l u o r e s c e n c e has been used a s a p r o b e o f m i c e l l e f o r m a t i o n in S D S t o s h o w t h a t t h e p r e s e n c e of poly[N-(Whydroxyalkyll-L-glutaminesl

process2B3.

has n o s i g n i f i c a n t effect on t h i s

L a s e r probing s h o w s t h a t f a s t i n t e r m i c e l l a r e x c h a n g e

o f m i c e l l e s o l u b i l i z e d p y r e n e o r c e t y l p y r i d i n i u m ion o c c u r s o n a t i m e s c a l e o f 0.3 t o 10 v s 2 0 4 .

A model involving fragmentation

into submicellar aggregates is proposed. o f S D S h a v e been

Heptanol swollen micelles

studied u s i n g p y r e n e as c h r o m o p h o r e and

b e n z o p h e n o n e a s a quencher2”.

The aggregation numbers depend on

t h e h e p t a n o l / S D S c o n c e n t r a t i o n ratio.

Picosecond absorption o f d y e

probes o f water i n o i l microemulsions shows evidence of complexing o f d y e p r o b e s w i t h n e i g h b o u r i n g o u r f a c t a n t m o l e c u l e s and t h e r e o r i e n t a t i o n m o t i o n determined2“

.

The dynamic behaviour o f

fluorescence quenchers o f pyrene in cetyltrimethylammonium

chloride

m i c e l l e s by i m m o b i l e , m o b i l e h y d r o p h o b i c , and m o b i l e h y d r o p h i l i c q u e n c h e r s has been e x a m i n e d z 8 7 ,

The r e s u l t s a l l o w c o n c l u s i o n s t o

be d r a w n a b o u t t h e s h a p e and s i z e o f C T A C m i c e l l e s .

The quenching

o f p y r e n e f l u o r e s c e n c e by i n d o l e i n m i c e l l a r s o l u t i o n s i s i n c r e a s e d by l o c a l high c o n c e n t r a t i o n s o f i n d o l e w h i c h a c c u m u l a t e i n t h e micelle2B8.

T h e q u e n c h i n g o f p y r e n e f l u o r e s c e n c e by C s * i o n s i n

m i c e l l e s i s r e d u c e d by t h e p r e s e n c e o f s u r f a c e a c t i v e c r o w n etherszB9.

The effect o f alkali metals o n fluorescence of pyrene

on t h e m i c e l l a r p r o p e r t i e s o f c r o w n e t h e r s u r f a c t a n t and t h e

Photochemistry

22

i n f l u e n c e o f p o l a r i t y o n t h e 1 1 / 1 3 band r a t i o o f t h e p y r e n e have The evidence shows that t h e metal ions complex

been examined2".

w i t h t h e c r o w n e t h e r . T h e q u e n c h i n g o f e x c i t e d p y r e n e bound t o c e t y l t r i m e t h y l a m m o n i u m m i c e l l e s by i n o r g a n i c c a t i o n s has a l s o been r e p o r t e d by O l e a and Lissi2".

Ground and e x c i t e d s t a t e proton

t r a n s f e r s i n r e v e r s e d m i c e l l e s h a v e been e x a m i n e d i n I - h y d r o x y 1 , 3 , 6 - p y r e n e t r i s u l p h o n a t e and s h o w p o l a r i t y r e s t r i c t i o n s and isotope effects292.

S t e a d y s t a t e l u m i n e s c e n c e has been used t o

determine the polarity of ionic clusters o n t h e Nafion 293 . (perfluorosulphonate polymers) D i p y r e n y l p r o p a n e c a n be used t o m e a s u r e m i c r o v i s c o s i t y o f DMPC b i l a y e r s in t h e l i q u i d c r y s t a l p h a s e as a f u n c t i o n o f h y d r o s t a t i c pressure

294

.

Dynamic fluorescence measurements

show different

m e c h a n i s m s f o r e x c i m e r f o r m a t i o n i n l i q u i d c r y s t a l l i n e and p r e s s u r e induced g e l phases.

S u r f a c t a n t and h y d r o p h o b i c d e r i v a t i v e s o f

t r a n s - s t i l b e n e s as probes o f v e s i c l e and m i c e l l e s o l u b i l i z a t i o n sites235.

As w e l l a s fluorescence, photoisomerization

can also

g i v e i n f o r m a t i o n o n o r d e r l i m i t e d r a t h e r t h a n viscosity l i m i t e d factors.

The effect of micelles o f Triton X - 1 0 0

biexponential fluorescence decay o f inve~tigated~~'.

( U022t

on the

1 * has been

The ion penetrates into t h e core of t h e micelles

but e x c i m e r s d o not p e n e t r a t e .

Differences in spectroscopic

properties of tris(2,2'-bipyridine) ruthenium I 1 absorbed on inner and o u t e r s u r f a c e s m a y be d u e t o packing d i f f e r e n c e s and v a r i a t i o n of ionic strength297. An i m p o r t a n t a s p e c t o f p h o t o c h e m i c a l e f f e c t s i n m i c e l l e s i s t h e f o r m a t i o n and s t a b i l i z a t i o n o f c h a r g e t r a n s f e r e f f e c t s w i t h a v i e w t o a p p l i c a t i o n i n solar e n e r g y c o n v e r s i o n .

An e x a m p l e o f t h i s

i s a study o f e l e c t r o n t r a n s f e r in m i c e l l a r - m e t a l ion s y s t e m s , where k

q

and e l e c t r o n t r a n s f e r y i e l d s f r o m S 1

-N - e t h y l c a r b a z o l e ,

and t h e T,

s t a t e s o f p y r e n e and

state o f N-methylphenothiazine

by a

n u m b e r o f m e t a l i o n s i n s o d i u m t a u r o c h o l a t e and s o d i u m l a u r y l s u l p h a t e h a v e been m e a s u r e d 2 3 8

.

Photosensitized charge transfer

and r e c o m b i n a t i o n o f t h e i o n i c p r o d u c t s i n m i c e l l a r s o l u t i o n s h a v e been e x a m i n e d i n m e s o - t e t r a - m e t a - N - m e t h y l p y r i d y l p o r p h i n e i n a q u e o u s s o l u t i o n and m i c e l l e s 2 9 9 . f r o m t h e t r i p l e t state.

In this case electron transfer occurs Photoionization thresholds o f chlorophyll

a and N . ~ , l j ' , ~ ' - t e t r a m e t h y l b e n z i d i n ei n v e s i c l e and m i c e l l e f r o z e n s o l u t i o n s has been studied by esr3".

Differences are d u e t o the

i o n i c n a t u r e and d e g r e e o f p e n e t r a t i o n i n t o t h e m i c e l l e s and vesicles.

A full survey o f t h e influence o f micelles

on


23

p h o t o c h e m i c a l reactivity by c a g e and microviscosity e f f e c t s , l o c a l i s a t i o n and c o m p a r t m e n t a l i z a t i o n , p r e - o r i e n t a t i o n a l , p o l a r i t y , and counter ion e f f e c t s is extremely u s e f u l 3 0 1 -

The e f f e c t s o f

c e t y l t r i m e t h y l a m m o n i u m bromide m i c e l l e s on complex stability and photoinduced electron t r a n s f e r on t h e c o m p l e x formation w h i c h o c c u r s between a n t h r a q u i n o n e - 2 , 6 - d i s u l p h o n a t e and n e u t r a l z i n c 302

porphyrin c o n s t i t u t e a d e t a i l e d e x a m i n a t i o n of such a s y s t e m

.

P h o t o l y s i s o f 2-phenylbenzoin i n m i c e l l a r s y s t e m s g e n e r a t e s a rearranged r a d i c a l pair w h i c h c a n suosequently c o m b i n e t o g i v e s t a b l e product303.

T h e d y n a m i c s of r a d i c a l pair r e a c t i o n s i n

m i c e l l e s h a v e been t i m e resolved by t h e application o f pulsed l a s e r f l a s h p h ~ t o l y s i s ~ ' ~ . G e m i n a t e r a d i c a l pairs decay i n 20-2000 x 10%

w h e r e a s e n c o u n t e r s o c c u r at t i m e separations of l o n g e r t h a n In reversed m i c e l l e s o f

2000 x 1 O-'s.

Bin- (2-ethylhexyll-

s u l p h o s u c c i n a t e in h e p t a n e t h r e e fluorescent acid probes u n d e r g o photolysis in t h e m i c e l l e c o r e w h i c h c o n t a i n s water3''.

Phase

fluorometry w a s used i n t h i s investigation. S t u d i e s have been m a d e o n t h e m i c r o e n v i r o n m e n t a l effects o f cyclodextrins: t h e s e i n c l u d e excimer f o r m a t i o n in p o l y m e t h y l e n e bis-$-naphthoates3"

and t h e f l u o r e s c e n c e o f p y r e n e and n a p h t h a l e n e

in c y c l o d e x t r i n - a m p h i p h i l e c o m p l e x systems w h i c h provide a very h y d r o p h o b i c environment for pyrene307

.

Absorption and f l u o r e s c e n c e

s t u d i e s o f t h e i n t e r a c t i o n of pyrene w i t h fl-cyclodextrin i n a q u e o u s surfactant solutions have a l s o been examined

308

.

T h e f l u o r e s c e n c e decay of pyrene i n t h e presence o f n o n i o n i c surfactants at solid-liquid interface is influenced by t h e polar c h a i n length3".

T h e f l u o r e s c e n c e o f t h e bifunctional p r o b e 1 , 3 -

d i p y r e n y l p r o p a n e absorbed o n silica and reversed phase silica surfaces31

'

and t h e d u a l f l u o r e s c e n c e o f l - ( Y , N - d i m e t h y l a m i n o ) - 4 -

benzonitrile absorbed on silica surfaces c a n be used as a probe o f s u r f a c e polarity3''.

T h e effect of t e m p e r a t u r e on t h e singlet

q u e n c h i n g o f pyrene absorbed o n silica g e l by 2-bromonaphthalene i n d i c a t e s t h a t d i f f u s i o n of t h e s e m o l e c u l e s i s rapid w h e n t h e s u r f a c e i s uniform3''.

Dye t o s u r f a c e n o n r a d i a t i v e e x c i t a t i o n

t r a n s f e r is a n important decay m o d e for t h e S1

state of c r e s y l

violet separated f r o m Ti02 s u r f a c e s by d i s t a n c e s between 8 0 and 5098 3 1 3 .

T h i s paper e x a m i n e s t h e t h e o r y of energy t r a n s f e r f r o m

an excited s t a t e t o a d i e l e c t r i c surface.

T h e cis-trans

iiomerization o f six s t y r e n e d e r i v a t i v e s has been observed on c a d m i u m s u l p h i d e particles and a kinetic a n a l y s i s o f t h e data attempted3 l 4

.

Photochemistry

24

An e n h a n c e m e n t o f m o l e c u l a r f l u o r e s c n e c e and p h o t o c h e m i c a l r a t e s i s brought about by s m a l l m e t a l p a r t i c l e s c a p a b l e o f sustaining e l e c t r o m a g n e t i c r e s o n a n c e s

315

.

Picosecond resonance

Raman s c a t t e r i n g o f m e t h y l v i o l o g e n r e d u c t i o n on s u r f a c e o f phtoexcited C d S s h o w s that a f t e r o p t i c a l e x c i t a t i o n t h e M V * s p e c t r u m w h i c h is observed

i n d i c a t e s t h a t t h e n a s c e n t MV+ may be

complexed w i t h o t h e r species3’

.

2.7 B i o l o a i c a l S v s t e m s - T h e s e n s i t i v i t y

o f luminescence techniques

and t h e u s e o f e x t r i n s i c and i n t r i n s i c f l u o r e s c e n c e p r o b e s have Only a

found c o n s i d e r a b l e a p p l i c a t i o n s in b i o l o g i c a l r e s e a r c h .

s e l e c t i o n o f s u c h s t u d i e s h a v e been s e l e c t e d f o r c i t a t i o n . F l u o r e s c e n c e and p h o s p h o r e s c e n c e o f a r o m a t i c 8 - c a r b o l i n e s , n o r h a r m a n , h a r m a n , and h a r m i n e , as d i s p e r s e d s o l i d s at 7 7 K and absorbed o n c e l l u l o s e at r o o m temperature3’? tautomeric equilibria o f the S been r e p o r t e d .

T h e photophysi:s

ergostatetraen-3$-01

and S

and a c i d - b a s e and

s t a t e s o f h a r m 0 1 ~ ~ ’have

of e:go~terol~’~,

I9

‘ 2 2-

(”

in micelles as w e l l as with sterol-carrier

p r o t e i n c o m p l e x e s and i n i n t e r a c t i o n w i t h plasma m e m b r a n e s 3 2 0 , and excited s t a t e p r o t o n t r a n s f e r o f e q u i l e n i n and d i h y d r o e q u i l e n i n i n i n t e r a c t i o n w i t h b i l a y e r v e s i c l e s 3 2 1 h a v e a l l been i n v e s t i g a t e d i n considerable detail.

F l u o r e s c e n c e and p h o s p h o r e s c e n c e o f

p h y o s t i g m i n e , r u b r e s e r i n e , and a d r e n o ~ h r o m e and ~ ~ ~t h e p h o t o i o n i z a t i o n o f NADH i n a q u e o u s s o l u t i o n c o n s e q u e n t upon t w o photon e x c i t a t i o n 3 2 3 a r e o t h e r i n t e r e s t i n g i n v e s t i g a t i o n s w h i c h have reported. Indole derivatives including tryptophan compounds still c o n t i n u e t o g e n e r a t e p r o b l e m s and r e s e a r c h o f p h o t o p h y s i c a l P o l a r i z e d 2 p h o t o n f l u o r e s c e n c e s p e c t r a of i n d o l e i n a

interest.

number o f s o l v e n t s has been e x c i t e d i n t h e r e g i o n o f L The multiexponential

bands322.

and L b

fluorescence decay o f indole-3-

a l k a n o i c a c i d s as a f u n c t i o n o f pH s h o w s t h e d y n a m i c i n t e r a c t i o n o f t h e side chain with t h e indole moiety is probably occurring during t h e lifetime o f t h e excited state32S,

308 n m X e C l l a s e r l i g h t

e x c i t e s t h e red e d g e o f t h e 1st e x c i t a t i o n band and S1 and

T

-+

T

-+

Sn

t r a n s i t i o n s i n N - m e t h y l i n d o l e and t h e f o r m a t i o n

of i o n pair s p e c i e s c h a r a c t e r i z e d .

A

very i n t e r e s t i n g s t u d y h a s

been a study o f t r y p t o p h a n i n t h e g a s p h a s e using a cold s u p e r s o n i c jet327.

C o n f o r m e r s i n g r o u n d and e x c i t e d s t a t e s h a v e b e e n

i d e n t i f i e d and r o t a m e r m o d e l s c o n f i r m e d 3 2 7 .

The results o f t h e

study h a v e c o n s i d e r a b l e v a l u e f o r r e s o l v i n g m a n y a s p e c t s o f t h e


25

results arising from investigations i n solution.

The

n o n e x p o n e n t i a l f l u o r e s c e n c e d e c a y o f t r y p t o p h a n has been e x p l a i n e d by a m o d e l c o n s i s t i n g o f t w o c o n f o r m e r s e a c h c o n s i s t i n g o f d i s t r i b u t i o n s o f o t h e r very s i m i l a r c o n f o r m e r s 3 2 8

.

Homotryptophan,

an a n a l o g u e o f t r y p t o p h a n w i t h a CH2 g r o u p s e p a r a t i n g t h e i n d o l e ring f r o m t h e a m i n o acid m o i e t y , is very s i m i l a r in i t s fluorescence properties t o tryptophan32g

.

Its b e h a v i o u r i s a l s o

e x p l a i n e d by t h e i n v o l v e m e n t o f t w o r o t a m e r s ( o r c o n f o r m e r s ) e a c h with a distribution o f lifetimes which analyses a s only involving two apparent lifetimes. Complex formation with solvent also occurs. Intramolecular exciplex formation occurs with N-2-acetyl-1-pyrenyl-

.

alanyl- 1 -methyltryptophan methyl ester330

The evaluation o f

charge effects on quenching o f tryptophan fluorescence i n peptides by I- and C1- i o n s has been e x a m i n e d i n t e r m s o f s e p a r a t e d y n a m i c and s t a t i c q u e n c h i n g e f f e c t s as w e l l a s a s i n g l e p r o c e s s

mechanism^^^'.

T h e e f f e c t o f pH o n t h e a e r o b i c and a n a e r o b i c

p h o t o l y s e s o f t r y p t o p h a n and s o m e t r y p t o p h a n d i p e p t i d e s h a s been 332 studied using f l u o r e s c e n c e s p e c t r o s c o p y

.

T y r o s i n e i s t h e o t h e r s i g n i f i c a n t f l u o r e s c e n t a m i n o acid residue.

T i m e r e s o l v e d f l u o r e s c e n c e and p r o t o n NMR s t u d i e s h a v e

been r e p o r t e d f o r t y r o s i n e and t y r o s i n e a n a l o g u e s i n d i c a t i n g m o r e This w o r k h a s been

c o m p l e x i t y t h a n has been e x p e c t e d h i t h e r t o 3 3 3 . e x t e n d e d t o t h e o x y t o c i n and o t h e r s m a l l

pep tide^^^^.

Tyrosyl

fluorescence spectra o f proteins lacking tryptophan shows that t y r o s i n e e m i s s i o n i s affected by c o n f o r m a t i o n a l c h a n g e s t h o u g h t t o be d u e t o f o r m a t i o n o f h y d r o g e n b o n d s b e t w e e n t h e h y d r o x y l o f t y r o s y l r e s i d u e s and p r o t o n a c c e p t o r g r o u p s 3 3 S

.

P r o t e i n s p r o v i d e m a n y p r o b l e m s s u i t a b l e f o r s t u d y by photophysical techniques.

The fluorescence behaviour o f sequential

t y r o s y l p o l y p e p t i d e s has been studied in a l k a l i n e solution336

and

q u e n c h i n g by e n e r g y t r a n s f e r t o t r y p t o p h a n - 1 9 i n m e l i t t i n has been used i n c o n f o r m a t i o n a l s t u d i e s

337

.

The environment o f tryptophan

r e s i d u e s in a z u r i n h a s been e x a m i n e d by o b s e r v i n g e l e c t r o n i c e n e r g y t r a n s f e r w i t h and w i t h o u t t h e p r e s e n c e o f c o p p e r i o n s 3 3 8 . F l u o r e s c e n c e l i f t i m e q u e n c h i n g and a n i s o t r o p y s t u d i e s h a v e been m a d e w i t h r i b o n u c l e a s e T1 w h i c h a s a l o n e t r y p t o p h a n 3 3 9 .

The

s i n g l e t r y p t o p h a n r e s i d u e i n cod p a r v a l b u m i n i s l o c a t e d i n a p o l a r r e g i o n and q u e n c h i n g by O2 and a c r y l a m i d e s h o w s t h a t d y n a m i c p e n e t r a t i o n by a c r y l a m i d e i s r e q u i r e d 3 4 0 .

I o d i d e ion and

a c r y l a m i d e q u e n c h i n g o f t r y p t o p h a n f l u o r e s c e n c e has b e e n used t o probe t h e a c t i v e s i t e i n r e n i n

341

, creatine k i n a ~ e ~ ~ * ,

Photochemistry

26

.

u r ~ c a n a s e, ~and ~ ~ t e r m i n a l d e o x y n u c l e o t i d y l t r a n ~ f e r a s e ~ ~P r~ o b e m o e i t i e s g i v e i n f o r m a t i o n on both s t r u c t u r e and c o n f o r m a t i o n a l changes.

Energy transfer takes place between tryptophan residues

i n t u b u l i n and bound brig-(8-anilionaphthalene-l-sulphonate)

which

i s an i n h i b i t o r o f m i c r o t u b u l e a s s e m b l y t h a t binds t o a f l e x i b l e region in t h e enzyme345.

Excimer formation in N - a c e t y l - U ( l -

pyrenylalanine) methyl ester allows the dynamics o f peptide chain m o t i o n t o be s t u d i e d 3 4 6 .

Q u e n c h i n g c a n be used t o study protein

d y n a m i c s by t h e s e p a r a t i o n o f s o l v e n t exposed and s o l v e n t masked f l u o r ~ p h o r s. ~ ~F r~ e q u e n c y d o m a i n s p e c t r o s c o p y m a k e s it possible t o o b s e r v e s u b n a n o s e c o n d a n i s o t r o p y d e c a y s ; m e l i t t i n , m o n e l l i n and straphylococcal nuclease are systems examined with time resolution d o w n t o 50 ps3“. T h e s a m e t e c h n i q u e has b e e n used t o s t u d y d a n s y l c h r o m o p h o r e s in m o d e l c o m p o u n d s and e n z y m e s

349

.

A t t e n t i o n i s d r a w n t o t h e need

for f l u o r o p h o r e s w i t h better p r o p e r t i e s t h a n t h o s e a v a i l a b l e s o f a r f o r t h i s purpose.

I n t r a m o l e c u l a r e x c i t a t i o n energy t r a n s f e r

b e t w e e n p h e n y l a l a n i n e and t y r o s i n e i n t h e p e p t i d e d e m o r p h i n e and i t s a n a l o g u e s is i n good a g r e e m e n t w i t h t h e o r y 3 5 0 .

The association

of a c r y l a m i d e w i t h p r o t e i n s i s i m p o r t a n t i n v i e w o f i t s r e l e v a n c e

.

t o f h e i n t e r p r e t a t i o n o f f l u o r e s c e n c e q u e n c h i n g experiments3”

R a d i a t i o n l e s s e n e r g y t r a n s f e r h a s been used t o s t u d y t h e effect o f a n i o n s on t h e a c t i v i t y o f c a r b o x y p e p t i d a ~ e - A ~ ~The ~ . dimeric form o f ANS i s a b e t t e r p r o b e t h a n A N S i t s e l f and has been used f o r and ~ ~ tubulin3” structural studies o n b o v i n e - 2 - l a ~ t a l b u r n i n ~

.

ANS

has been used a s an e x t r i n s i c p r o b e f o r c o n f o r m a t i o n c h a n g e s i n c i l i a r y d y n e i n w h i c h p r o v i d e s t h e o r i g i n f o r m e c h a n i c a l t h r u s t in cell motility355.

T h e f l e x i b i l i t y o f m o l e c u l a r f o r m s of

a c e t y l c h o l i n e e s t e r a s e h a s been m e a s u r e d by steady s t a t e and t i m e c o r r e l a t e d f l u o r e s c e n c e p o l a r i z a t i o n s p e c t r o s c o p y using c o v a l e n t l y bound probes3”.

F l u o r e s c e n c e e n e r g y t r a n s f e r has been used t o

o b s e r v e c o n f o r m a t i o n a l c h a n g e s o f c y t o c h r o m e P - C S O .~ ~A ~ r e m a r k a b l e s t u d y has been m a d e o n t h e p r o t e i n b r e v i n w h i c h has 1 0 t r y p t o p h a n and 2 7 t y r o s i n e r e s i d u e s and t h e e f f e c t s o f Ca2* ions on t h e c o n f o r m a t i o n investigated3”.

Binding o f C a 2 * , L n 3 * , Eu”

Tb3+ t o p a r v a l b u m i n h a v e a l s o b e e n quantified3”.

and

Oistances

between a c t i v e s i t e p r o b e s i n g l u t a m i n e s y n t h e t a s e i n f r e e and stacked c o n d i t i o n s h a v e a l s o been m e a s u r e d by f l u o r e s c e n c e energy transfer360.

I n t r i n s i c t y r o s i n e f l u o r e s c e n c e o f h i s t o n e H 1 c a n be

used t o study t h e e f f e c t s o f f o l d i n g and u n f o l d i n g w h i c h i s i n d u c e d by salt and e f f e c t s excited s t a t e p r o t o n transfer36’.

The


27

i n h i b i t i o n o f b o v i n e p a n c r e a t i c t r y p s i n has been studied by t h e

.

l a b e l l i n g o f t h e 2 - a m i n o g r o u p w i t h 2 - n a p h t h o x y a c e t i c acid362

Interactions between subunits o f skeletal muscle troponin have been i n v e s t i g a t e d by f l u o r e s c e n c e q u e n c h i n g , p h o t o c h e m i c a l c r o s s l i n k i n g , and e n e r g y t r a n s f e r 3 6 3 .

Calcium binding t o troponin has

been s h o w n by l a b e l l i n g w i t h t h e p r o b e 5 - ( i o d o a c e t a m i d o e t h y l ) a m i n o n a p h t h a l e n e - 1 s u l p h o n i c acid

[1

, 5 -IAEDANS1364

.

Haem protein

fluorescence detects conformational changes a s small as a f e w t e n t h s o f an

8

d u e t o pressure induced folding365.

T h e plant

protein pinellin has tryptophan residues whose intrinsic f l u o r e s c e n c e and C D t h a t h a v e been used t o f o l l o w c o n f o r m a t i o n a l changes366.

P i c o s e c o n d t i m e - r e s o l v e d R a m a n s t u d i e s h a v e been used

t o e x a m i n e t h e p h o t o d i s socia t i o n o f c a r b o ~ y m y o g l o b i n ~ (Ca2+

+

.

M g 2 + ) - A T P a s e o f s a r c o p l a s m i d r e t i c u l u m i s an

e x t e n s i v e l y studied system.

Distances between functional sites

h a v e been m e a s u r e d by using l u m i n e s c e n t i o n s a s d o n o r s and acceptors368.

T h e q u e n c h i n g o f t r y p t o p h a n y l r e s i d u e s by a c r y l a m i d e

i n t h i s e n z y m e h a s been e x a m i n e d i n r e c o n s t i t u t e d s y n t h e t i c p h o s p h o l i p i d membranesJ6’.

T h e i n t e r a c t i o n w i t h v a l i n o m y c i n and

m o n o v a l e n t c a t i o n s w i t h t h e A T P a s e h a s been m e a s u r e d by u s e o f a f l u o r e s c e n t ATP a n a l o g u e a s probe370

and t h e o p e n i n g u p o f t h e

e n z y m e by Ca2* i o n s has been s h o w n by p y r e n e g r o u p l a b e l l i n g o f thiol residues3?’

.

I n t e r a c t i o n b e t w e e n A T P a s e m o l e c u l e s has b e e n

e x a m i n e d by p y r e n e e x c i m e r f o r m a t i o n 3 7 2 and a g g r e g a t i o n e x a m i n e d by energy t r a n s f e r b e t w e e n l a b e l l e d p r o t e i n m o l e c u l e s 3 7 3

.

I n t r a m o l e c u l a r d i s t a n c e d i s t r i b u t i o n s h a v e been m e a s u r e d by e x c i t a t i o n energy t r a n s f e r m e a s u r e m e n t s i n b o v i n e p a n c r e a t i c The effects of ionic strength o n t h e protein

trypsin inhibitor374.

c o n f o r m a t i o n and f l u i d i t y o f t h e p o r c i n e b r u s h b o r d e r m e m b r a n e h a s been m a d e using t h e p r o b e s ~ - [ 7 - d i m e t h y l a m i n o - 4 - c o u m a r i n y l l m a l e i m i d e and pyrene3 7 5

.

Calcium release from sacroplasmic

r e t i c u l u m c a n a l s o be f o l l o w e d by t h e u s e o f s u c h p r o b e s

376

.

P i c o s e c o n d and f e m t o s e c o n d f l u o r e s c e n c e s p e c t r o s c o p y h a s been used t o s t u d y b o v i n e r h ~ d o p s i n ~ and ~ ’ bacteriorhodopsin

378

.

In

t h i s l a s t c a s e i n t e r m e d i a t e s w i t h d e c a y t i m e s o f 4 3 0 2 5 0 fs h a v e been d e t e c t e d and a n u p p e r l i m i t o f 5 0 f s d e t e r m i n e d f o r t r a n s f e r o f excitation energy

from an electronically coupled trimer t o a

s i n g l e r e t i n a l unit. A t h e o r e t i c a l r e v i e w o f t h e a b s o r p t i o n o f l i g h t by V i s u a l p i g m e n t s i n v i t r o , i n s i t u and i n v i v o u n d e r d i f f e r e n t c o n d i t i o n s of i l l u m i n a t i o n has b e e n e x t e n s i v e l y r e v i e w e d ( 1 4 2

reference^)^'^.

Photochemistry

28

T h e f l u o r e s c e n c e q u e n c h i n g o f c h l o r o p h y l l a i n a c e t o n e has been examined by s i n g l e b e a m p h o t o a c o u s t i c s p e ~ t r o m e t e r ~ ~. ' A L a n g m i u r f i l m has been used t o o b s e r v e t h e effect o f m o l e c u l a r o r g a n i s a t i o n on t h e l i f e t i m e and s t e a d y s t a t e f l u o r e s c e n c e o f c h l o r o p h y l l a in monolayers of dioleophosphatidylcholine at an N2-water interface3a'.

The kinetics of fluorescence decay i n a small finite

v o l u m e has been a p p l i e d t o t h e $-subunit o f t h e p h y c o e r y t h r i n a g g r e g a t e w h e r e t h e r e i s ground s t a t e d e p l e t i o n and u p p e r excited state a b s o r p t i o n 3 8 2 . T h e m o n o m e r i z a t i o n o f t h y m i n e by i r r a d i a t i o n o f a c o m p l e x o f t h y m i n e d i m e r w i t h Hg2* i n v o l v e s b r e a k i n g o f t h e c y c l o b u t a n e ring of t h e d i m e r 3 8 3 .

T h e h y p o c h r o m i c e f f e c t and e l e c t r o n i c energy

t r a n s f e r in Y t - ( C H 1 - a d e n i n e s y s t e m s , w h e r e Y t i s a p u r i n e 2 n d e r i v a t i v e has been m e a s u r e d a s a f u n c t i o n o f n 3 a 4 . T h e effect o f interaction is strongest when n = 3 .

Energy t r a n s f e r i n n u c l e i c

a c i d s and p o l y n u c l e o t i d e s c a n be studied using c o m p l e x t e r b i u m a s T h e p h o t o p h y s i c s o f r u t h e n i u m c o m p l e x e s w i t h DNA

an acceptor3".

has been used t o e x a m i n e t h e n a t u r e o f t h e i n t e r a c t i o n and i t s environment386

.

The interactions of polycyclic aromatic

h y d r o c a r b o n s w i t h DNA by a b s o r p t i o n and f l u r o r e s c e n c e q u e n c h i n g involve moderately strong 1 : l

charge transfer states which

correlate with solvent reorganisation energies better than the Marcus model of electron transfer307

.

Nanosecond fluorescence

s t u d i e s o f DNA i n t e r c a l a t o r s , w h i c h a r e potent m u t a g e n s i n m o n o m e r i c and d i m e r i c s t a t e s , h a v e a l s o been made3".

Transition

m e t a l i o n s q u e n c h t h e f l u o r e s c e n c e o f DNA i n t e r c a l a t e d e t h i d i u m and a t i m e r e s o l v e d study h a s b e e n m a d e o f p h e n y l i n d o l e h y d r o c h l o r i d e binding t o p o l y n u c l e ~ t i d e s.~ ~T~h e l a t t e r r e a g e n t i s used a s a p r o b e o f n u c l e i c acid s t r u c t u r e w i t h a p p l i c a t i o n s t o cytology. F l u o r e s c e n c e d e t e c t e d C D o f e t h i d i u m i o n s bound t o DNA i n v i v o and i n v i t r p i n d i c a t e s t h a t t h e e t h i d i u m i o n binds t o n u c l e i c acid i n E.coli, c e l l s by i n t e r c a l a t i ~ n ~ ~ ' . T h e m e t h o d i s highly s e n s i t i v e and c o m b i n e s t h e s p e c i f i c i t y o f f l u o r e s c e n c e w i t h t h e c o n f o r m a t i o n a l s e n s i t i v i t y o f C D and c a n a l s o be used w i t h s c a t t e r i n g and o p t i c a l l y d e n s e samples. A n o t h e r very s i g n i f i c a n t study i s c o n c e r n e d w i t h e n e r g y t r a n s f e r i n p o l y n u c l e o t i d e s a f t e r t w o s t e p picosecond

excitation392

.

The distances measured under

d i f f e r e n t c o n d i t i o n s a r e r e l e v a n t t o both r a d i o b i o l o g y and photobiology.

T h e b i n d i n g o f 9 - a m i n o a c r i d i n e t o c a l f t h y m u s DNA i s

c o n s i s t e n t w i t h c u r r e n t binding m o d e l s and e x c i t o n i n t e r a c t i o n 3 3 3 T h e i n t e r a c t i o n s o f n o n - h i s t o n e c h r o m o s o m a l p r o t e i n H M G I w i t h DNA

.


29

h a v e been e x a m i n e d using t r y p t o p h a n as probe394.

Diffusion

e n h a n c e d energy t r a n s f e r s t u d y o f DNA bound C o ( I I 1 ) b l e o m y c i n s using e x c i t e d L n ( I 1 1 ) has been used t o c o m p a r e t h i s c o m p l e x w i t h e t h i d i u m and a c r i d i n e o r a n g e s y s t e m s 3 9 5

.

F l u o r e s c e n c e e m i s s i o n and

p o l a r i z a t i o n h a s been used t o s t u d y t h e c o n f o r m a t i o n s o f c o r e nucleosomes with histone H 4 3 9 6 .

An e x t r e m e l y s o p h i s t i c a t e d

a p p l i c a t i o n o f f l u o r e s c e n c e i s t h e o b s e r v a t i o n o f t-RNA t o p o g r a p h y d u r i n g t r a n s l o c a t i o n by t h e u s e o f w y b u t i n e as d o n o r and p r o f l a v i n e as acceptor397. T h e use o f diphenylhexatriene

(DPH)

as a p r o b e i s very

e x t e n s i v e . The t r a n s v e r s e l o c a t i o n o f OPH in m o d e l b i l a y e r m e m b r a n e s y s t e m s has been studied by r e s o n a n c e e x c i t a t i o n energy t r a n s f e r t o a fluorescein acceptor398.

Lipid s o l v a t i o n o f t h e a q u e o u s f o r m o f

m y e l i n p r o t e o l i p i d a p o p r o t e i n l e a d s t o t w o lipid p o p u l a t i o n s w h i c h c a n be c h a r a c t e r i z e d by t h e f l u o r e s c e n c e p o l a r i z a t i o n o f DPH3"

.

T h e r e l a t i o n s h i p b e t w e e n l i p i d f l u i d i t y and w a t e r p e r m e a b i l i t y o f b o v i n e t r a c h a e l e p i t h e l i a l c e l l a p i c a l m e m b r a n e s has been e x a m i n e d by f l u o r e s c e n c e p o l a r i z a t i o n o f OPH4"

.

Chronic ethanol increases

l i v e r plasma m e m b r a n e f l u i d i t y a s s h o w n by d e c r e a s e d p o l a r i z a t i o n o f O P H w h e r e a s t h e s u r f a c e probe t r i m e t h y l a m m o n i u m D P H 1 s unaffected4"

.

I n t r a c e l l u l a r pH c a n be m e a s u r e d by a n a l y s i n g t h e e m i s s i o n s p e c t r a o f 1 , 4 - d i h y d r o x y p h t h a l o n i t r i l e s i n c e both t h e a c i d and b a s e f o r m s f l u o r e s c e differently4".

T h i s p r o b e has t h e a d v a n t a g e t h a t

it i s a p p a r e n t l y not t o x i c t o cells.

Fluorimetric detection of

p h o s p h o l i p i d v e s i c l e s bound t o p l a n e r p h o s p h o l i p i d m e m b r a n e s and detection o f multilamellar vesicles (liposomes) can be m a d e with 6 - c a r b o x y f l u o r e ~ c e i n.~ ~ L~o c a l i z a t i o n o f t h e v i g i n i a m y c i n S b i n d i n g s i t e o n b a c t e r i a l r i b o s o m e by energy t r a n s f e r has b e e n a c h i e v e d by using t h e h y d r o x y p i c o l i n y l m o i e t y a s d o n o r and c o u m a r i n y l d e r i v a t i v e s o f r i b o s o m a l p r o t e i n s as a c c e p t o r s 4 0 4 .

The

theory o f t i m e resolved fluorescence polarization from ordered b i o l o g i c a l a s s e m b l i e s has been applied t o f l u o r e s c e n t l a b e l l e d m y o s i n c r o s s b r i d g e s i n r e l a x e d m u s c l e fibres405

.

Fluorescence

e n e r g y t r a n s f e r h a s b e e n used t o c h a r a c t e r i s e m y o s i n i n t h i c k f i l m a s s e m b l i e s , a m e t h o d w h i c h has been s h o w n t o be s e n s i t i v e and r e p r o d ~ c i b l e ~ ~. ' Rapid c h a n g e s i n t h e m e m b r a n e p o t e n t i a l o f heart m u s c l e c a n b e m a d e by f l u o r e s c e n c e m o n i t o r i n g o f t h e v o l t a g e s e n s i t i v e d y e f?H23T407

.

F l u o r e s c e n t i n d i c a t o r s f o r Ca2+ a r e e x t r e m e l y useful.

T h e r e l a t i o n s h i p b e t w e e n t h e c o n c e n t r a t i o n o f c y t o s o l i c f r e e Ca2+

Photochemistry

30

and s e c r e t i o n o f p a r a t h y r o i d h o r m o n e has b e e n i n v e s t i g a t e d i n b o v i n e p a r a t h y r o i d c e l l s u s i n g t h e C a 2 + i n d i c a t o r Q~in-2.'~'.

The

i d e n t i f i c a t i o n o f b a c t e r i a l p a t h o g e n s by l a s e r i l l u m i n a t i o n c a n be m a d e by t h e h y d r o l y s i s o f n o n f l u o r e s c e n t L - a m i n o acid-8naphthylamides.'"

.

Diffusion of dichlorofluorescein,

c a r b o x y f l u o r e s c e i n , and l u c i f e r y e l l o w w i t h i n s e p t a t e m e d i u m g i a n t axon o f t h e e a r t h w o r m h a s been m o n i t o r e d and a m o d e l Translational movements of mitochondria i n cultured rat liver cells a r e c h a r a c t e r i s e d by u s i n g a v i d e o c a m e r a and v i d e o - d i g i t i z e r computer system t o analyse fluorescent images o f mitochondria stained w i t h r h o d a m i n e - 1 2 3 4 1 1 .

The motion of myosin cross bridges

in s k e l e t a l m u s c l e f i b r e s h a s been studied b y t i m e r e s o l v e d f l u o r e s c e n c e d e c a y using 1 , 5 - 1 A E D A N S a s p r o b a 4 1 2 . P h o t o s e n s i t i z a t i o n i s o f both b i o l o g i c a l and c l i n i c a l importance.

The n a t u r a l l y o c c u r r i n g h y p e r c i n and i t s p h o t o d y n a m i c

a c t i o n has been c o m p r e h e n s i v e l y reviewed4'

.

P h t h a l o c y a n i n e s and

t h e i r use f o r t h e p h o t o d y n a m i c t h e r a p y o f t u m o u r s has been r e v i e w e d a p p a r e n t l y f o r t h e f i r s t t i m e , by S p i k e s 4 1 4 .

P h t h a l o c y a n i n e s could

have advantages over haematoporphyrin derivatives as clinical p h o t o s e n s i t i z e r s i n t h a t they a b s o r b m o r e strongly in t h e red and a l s o may b e t a k e n u p s e l e c t i v e l y by t u m o u r cells.

Moan4"

has also

produced a very c o m p r e h e n s i v e r e v i e w o f r e c e n t w o r k o n p o r p h y r i n p h o t o s e n s i t i z a t i o n and p h o t o t h e r a p y .

The nature of t h e active

c o m p o n e n t i n t h e t u m o u r l o c a l i s i n g h a e m a t o p o r p h y r i n s e n s i t i z e r has been considered in a n o t h e r r e v i e w by Kessel.""

The a b s o r p t i o n and

f l u o r e s c e n c e s p e c t r a o f h a e m a t o p o r p h y r i n I X , P h o t o f r i n , and P h o t o f r i n I 1 h a v e been m e a s u r e d as a f u n c t i o n o f pH. c o n c e n t r a t i o n , and t e m p e r a t u r e t o i s o l a t e i o n i c e q u i l i b r i a f r o m m o n o m e r f d i m e r / a g g r e g a t e f orma tion4

'

.

I n t e r e s t i n t h e t r i p l e t s t a t e i s not a s a c t i v e nor a r e t h e r e as m a n y d i v e r s e d e v e l o p m e n t s as i s t h e c a s e f o r e x c i t e d s i n g l e t states.

T h e r e i s l e s s d e t a i l e d s p e c t r o s c o p i c w o r k on t r i p l e t s t a t e

p r o p e r t i e s and b i o l o g i c a l i n v o l v e m e n t i s not e x t e n s i v e a l t h o u g h t h e photosensitizer systems mentioned in t h e previous section operate largely through triplet state intermediates. E v i d e n c e has been o b t a i n e d f o r a l i n e a r excited t r i p l e t s t a t e

(3E:)

o f a c e t y l e n e i n a rigid m a t r i x

( N e , Ar and X e ) at 4 . 8 K w h i c h

I: Photophysical Processes in Condensed Phases e m i t s b e t w e e n 190 and 2 4 0 n m 4 l 8 .

31

The phototoxic polyacetylene,

phenylheptatriyne shows strong triplet state absorption with a l i f e t i m e o f a b o u t 28

$JS

in methano1419.

1 , 3 - o c t a d i e n e and by O2 t o g i v e

lo2.

T h e t r i p l e t i s q u e n c h e d by

The triplet state of

c y c l o h e p t a t r i e n e has b e e n p r o d u c e d by p u l s e r a d i o l y s i s i n t o l u e n e w i t h a l i f e t i m e o f 6 2 1 ~ 1 s ~ ~ ' . T h e l o w e s t excited t r i p l e t s t a t e s o f a l l t r a n s - o c t a t r i e n e , a l l o c i m e n e , and n e o - a l l o c i m e n e h a v e been studied by t i m e resolved r e s o n a n c e Raman s p e c t r o ~ c o p y ~ ~ ' .It i s not p o s s i b l e t o d e c i d e w h e t h e r t h e t r i p l e t s t a t e s o f t h e s e t h r e e molecules are identical. A m a g n e t i c r e s o n a n c e study has been m a d e o f t h e t r i p l e t s t a t e o f p y r i d i n e present a s a g u e s t in a b e n z e n e s i n g l e c r y s t a l 4 2 2 . Evidence is produced for a pseudo Jahn-Teller deformation of the t r i p l e t state.

L a s e r f l a s h p h o t o l y s i s o f c h l o r o b e n z e n e in polar

s o l v e n t s a l l o w s t h e t r i p l e t s t a t e t o be c h a r a ~ t e r i s e d ~ ~Triplet ~. state properties of meas'ured

2-,

rn-

and e - d i c h l o r o b e n z e n e s and y i e l d s

by t r a n s f e r t o a n t h r a ~ e n e ~ ~T h~e. e f f e c t o f t h e

e n v i r o n m e n t o n t h e p h o s p h o r e s c e n c e p r o p e r t i e s o f _p-aminoa c e t o p h e n o n e ( P A A P ) under a w i d e r a n g e o f c o n d i t i o n s h a s been studied and it i s a p p a r e n t t h a t c h a r g e t r a n s f e r i s s i g n i f i c a n t i n t h e o b s e r v e d r o o m t e m p e r a t u r e p h o s p h o r e s c e n c e o f PAAP425

.

Interactions responsible for inducing the room temperature phosphorescence

o f p - a m i n o b e n z o i c acid absorbed o n N a A c - N a C 1

m i x t u r e s h a v e been e l u c i d a t e d and at l e a s t t w o m e c h a n i s m s identified426.

L a s e r f l a s h p h o t o l y s i s o f a c y l p h o s p h o r i c acid

e s t e r s g e n e r a t e s t r i p l e t s t a t e s w h o s e k e t o and e n o l s t a t e s h a v e been c h a r a c t e r i z e d 4 2 7

.

T h e c i s - t r a n s i s o m e r i z a t i o n o f 1 , 3 - p e n t a d i e n e and s e n s i t i z e d p h o s p h o r e s c e n c e o f b i a c e t y l h a v e been used t o m e a s u r e t h e e f f e c t o f t e m p e r a t u r e o n t h e t r i p l e t y i e l d s o f m e t h y l and p h e n y l - s u b s t i t u t e d biphenyl molecules428.

The phosphorescence o f trans-stilbene i n

t h e c r y s t a l l i n e s t a t e at 4 . 2 K h a s a l i f e t i m e o f 100 published

esr spectrum of t h e T,

The

state of trans-stilbene i n a glass

at 7 7 K i s t h e f i r s t r e p o r t o f t h e e s r s p e c t r u m o f a t r i p l e t 430 Triplet-triplet absorption spectra o f trans-stilbene,

polyene

.

6,4'-dehydroxystilbene, 4 , 6 ' - d i a m i n o - 2 , 2 ' - s t i l b e n e

disodium

d i s u l p h a t e , and 4 , & ' - d i p h e n y l s t i l b e n e w h i c h h a v e s h o r t t r i p l e t l i f e t i m e s have been m e a s u r e d 4 3 1 . C2,23

(1,C)

The phosphorescence properties o f

naphthaleno-paracyclophane

and C 2 , 2 1 ( 1 , 4 ) -

c h r y s e n o p a r a c y c l o p h a n e and t h e g r o u n d s t a t e c o m p l e x e s o f t h e s e hydrocarbons with silver perchlorate have also been

32

Photochemistry

published432 ' 4 3 3

.

T h e d e l a y e d f l u o r e s c e n c e and 7 - T a b s o r p t i o n

f o r a n t h r a c e n e , t e t r a c e n e , and m e s o d i p h e n y l h e l i a n t h r e n e

has been

used t o d e t e r m i n e t h e k i n e t i c s and e f f i c i e n c y o f s i n g l e t s t a t e Photoacoustic measurements o f triplet yields for a n t h r a c e n e , a c r i d i n e , p h t h a l a z i n e , and q u i n o x a l i n e a r e in good agreement with literature values435.

The lifetimes of the triplet

states i n v o l v e d m u s t be g r e a t e r t h a n 1 p s f o r t h e s u c c e s s f u l application of this technique.

T-T

t r a n s i e n t a b s o r p t i o n spectra

for a n t h r a c e n e , and i t s 2- and 9 - m e t h y l d e r i v a t i v e s i n d i f f e r e n t s o l v e n t s u n d e r t h e i n f l u e n c e o f p r e s s u r e s h o w s an e f f e c t upon intersystem crossing which is d u e t o a change to t h e Franck-Cordon factors brought about by v a r i a t i o n o f t h e S ,-TZ e n e r g y g a p

436

.

P h o s p h o r e s c e n c e l i n e n a r r o w i n g o f c o r o n e n e and p h e n a t h r e n e absorbed on c e l l u l o s e b e t w e e n 4 and 3 0 0 K has been o b s e r v e d f o r t h e f i r s t time437.

Intersystem crossing from singlet states o f molecular

d i m e r s o f p e n t a c e n e in m i x e d m o l e c u l a r c r y s t a l s (_p-terphenyl) has been studied by picosecond

s t i m u l a t e d p h o t o n e c h o experimentsi3'

.

T r a n s i e n t Raman s p e c t r a p r o v i d e e v i d e n c e f o r a " o n e w a y " c i s t o t r a n s i s o m e r i z a t i o n in t h e l o w e s t e x c i t e d t r i p l e t s t a t e o f 2 styrylanthracenei3'.

T h e d e c a y of p h o s p h o r e s c e n c e o f p h e n a n t h r e n e

in b i p h e n y l p o l y c r y s t a l s d e p e n d s o n t h e d u r a t i o n of t h e e x c i t a t i o n pulse due t o distance dependent interaction of quest molecules in t h e l o w e s t t r i p l e t state'". A time resolved

e s r s t u d y o f t h e m a g n e t i c and d e c a y p r o p e r t i e s

of t h e short l i v e d n o n p h o s p h o r e s c e n t

( n , n * ) state of pyridazine

shows t h e very l a r g e n o n r a d i a t i v e d e c a y constantb".

T h e yield t h e

triplet s t a t e o f 1 , 3 - d i a z a a z u l e n e in b e n z e n e has been m e a s u r e d t o be 0 . 6 3 4 4 2 .

The role o f triplet states in t h e trans

-+

cis

photoisomerization of quaternary salts o f 4-nitro-4'-azastilbene and t h e i r q u i n o l i n i u m s a l t s h a v e been c h a r a c t e r i s e d by l a s e r f l a s h p h o t ~ l y s i s ~ ~In ~ .c o n t r a s t w i t h s t i l b e n e t h e i s o m e r i z a t i o n o f 1 , Z - U - p y r a z y l e t h y l e n e p r o c e e d s t h r o u g h t h e t r i p l e t state. Nanosecond l a s e r f l a s h p h o t o l y s i s s h o w s e f f i c i e n t i n t e r s y s t e m crossing on direct excitation44i.

T h e e n e r g y l e v e l s o f t h e c i s and

t r a n s - t r i p l e t s h a v e b e e n d e t e r m i n e d and a c h a n g e o f '(IT,

TI*)

c h a r a c t e r o c c u r s w i t h s o l v e n t polarity.

( n , n * ) and

The triplet state

o f N , N - d i m e t h y l a n i l i n e d e c a y s by 2nd o r d e r k i n e t i c s i n c y c l o h e x a n e

and l e a d s t o d e l a y e d f l u o r e s c e n c e but d e c a y s f i r s t o r d e r i n methanoli4'.

The line pattern of t h e phosphorescence excitation

spectra o f b e n z o C a 3 p h e n a z i n e at b K i s s t r o n g l y s i t e d e p e n d e n t d u e t o t h e s m a l l e n e r g y s e p a r a t i o n o f t h e S,(n, n * ) and

S2(w,

a*)

I: Photophysical Processes in Condensed Phases states446.

33

The deactivation mechanism o f photoexcited phenazine in

s h o w s i n t e r s y s t e m c r o s s i n g and r a d i c a l f o r m a t i o n d e p e n d s

C F C H OH 3 2

o n t h e p r o x i m i t y o f S 2 ( n , n * ) , S1 ( n , n * ) , and T 2 ( n , n * ) states447. T h e r e l a t i v e s u b l e v e l populating r a t e s via t h e z e r o f i e l d s u b l e v e l s o f p h t h a l a z i n e i n 2 - o c t a n o l h a s been d e t e r m i n e d by OOMR'". Time resolved phosphorescence spectra of vitreous benzophenone at d i f f e r e n t t e m p e r a t u r e s h a v e been i n t e r p r e t e d a s d u e t o e n e r g e t i c relaxation o f triplet excitons44g

.

A l o w temperature emission

s t u d y o f d i m e t h y l b e n z o p h e n o n e and n a p h t h a l e n e - d i m e t h y l b e n z o p h e n o n e crystals shows that t h e mechanism o f phosphorescence quenching is d i f f e r e n t t o t h a t o f b e n z o p h e n o n e and i n v o l v e s e l e c t r o n - p h o n o n c o u p l i n g i n f l u e n c e d by c r y s t a l s t r u c t u r e i S 0

.

Triplet states of ring substituted $-phenylpropiophenones have been c h a r a c t e r i z e d by l a s e r f l a s h p h o t o l y s i s and p h o s p h o r e s c e n c e at

.

- 7 0 O c ~ ~ '

S p i n r e l a x a t i o n o f t h e b e n z i l t r i p l e t has b e e n s t u d i e d

by n a n o s e c o n d s i n g l e p h o t o n counting"

*

and p h o s p h o r e s c e n c e l i n e

narrowing reported for several 1-indanone derivatives

153

.

S o l v a t o c h r o m i c e f f e c t s i n t h e f l u o r e s c e n c e and T-T a b s o r p t i o n s p e c t r a o f x a n t h o n e , t h i o x a n t h o n e , and N - m e t h y l a c r i d i n e p r o d u c e red shifts with increasing solvent polarity ( p * increase) whereas T-T i s strongly blue shifted

(p*

decrease)454.

Laser flash photolysis

has been used t o study t h e t r i p l e t s t a t e s o f c y c l o b u t a n e t h i o n e s and the transfer of triplet excitation from them to D P H 4 5 5 . t h e r m a l d e a c t i v a t i o n o f S, and T,

The

states o f acridine dyes i n

p o l y ( v i n y 1 a l c o h o l ) f i l m s h a s been used t o m e a s u r e t r i p l e t y i e l d s by Parker's m e t h o d 4 s 6 . Hydrogen atom transfer from triplet 1-naphthol t o ground benzophenonei5

and q u e n c h i n g o f t r i p l e t b e n z o p h e n o n e by a V a r i e t y

of biological antioxidants, some o f which involve charge-transfer e f f e c t s 4 5 0 , a r e c h e m i c a l r e a c t i o n s w h i c h h a v e been s t u d i e d .

2-

Phenoxyacetophenone undergoes intramolecular triplet deactivation by q u e n c h i n g d u e t o p h e n y l r i n g , a p r o c e s s m u c h f a s t e r t h a n f o r 8 phenoxyacetophenone (n,

T*)

459

.

T h e photochemical reactions between t h e

t r i p l e t s t a t e o f b e n z o p h e n o n e and N , g - d i e t h y l a n i l i n e h a v e

been studied by a C I D E P m e t h o d i n p o l a r and n o n p o l a r media'". Direct h y d r o g e n a t o m t r a n s f e r o r t h e f o r m a t i o n o f an i o n pair a r e a l t e r n a t i v e p r o c e s s e s w h i c h d e p e n d u p o n t h e polarity o f t h e solvent.

T h e d e c a y k i n e t i c s and q u e n c h i n g o f w a t e r s o l u b l e i o n i c

b e n z o p h e n o n e s c o n t a i n i n g q u a r t e r n i s e d a m i n e and s u l p h o n a t e g r o u p h a v e been i n v e s t i g a t e d by l a s e r f l a s h p h o t ~ l y s i s. ~ ~W a~t e r s o l u b l e b e n z o p h e n o n e s i n m i c e l l a r s o l u t i o n a r e q u e n c h e d by m o n o m e r s and

Photochemistry

34

a m i n e ~ ~ ~and ' t h e i s o m e r i c a n t h r a c e n e sulphona t e s , 1 - A S , 1 , 5 - A S , and 1 , 8 - A S

2-AS

a l l p r o d u c e high y i e l d s of t r i p l e t s 4 6 3 .

D i f f u s e r e f l e c t a n c e l a s e r f l a s h p h o t o l y s i s o f a n u m b e r of k e t o n e s on silica and z e o l i t e s s h o w that t r i p l e t d e c a y k i n e t i c s a r e complex464

.

e4"

T h e effect o f t e m p e r a t u r e o n t h e l u m i n e s c e n c e

and l i f e t i m e o f b i s ( C - c h l o r o t h i o p h e n o l ) - ( l , 1 0 p h e n a n t h r o l i n e ) z i n c ( 1 1 ) has been

the

(n, **I

interpreted as d u e t o a barrier for t h e conversion of l e v e l t o l o w l y i n g CT l e v e l s 4 6 6 .

o f m e t h y l e n e blue i s q u e n c h e d by t h e ground

The

(n,

TT*)

state

state of phenazine

t h r o u g h a c h a r g e t r a n s f e r e x c i p l e x w h i c h p r e v e n t s b l e a c h i n g of t h e dye467.

T h e p h o t o p h y s i c s and r e a c t i o n s ot z i n c p r o t o p o r p h y r i n s

h a v e been characterized4"

and t h e r e s o n a n c e Raman s p e c t r a o f M g ,

Z n and P d t e t r a p h e n y l p o r p h i n e s annihilation o f metal

(71,

reported469

.

The triplet-triplet

m * ) p o r p h y r i n s and 3 ( a , r * )

phthalocyanines involves dimerization t h a n d i f f u s i o n controlled470

.

into excimers at a rate less

Contrary to earlier reports triplet

e x c i p l e x e s h a v e not b e e n d e t e c t e d i n t h e q u e n c h i n g o f t r i p l e t p o r p h y r i n s , c h l o r o p h y l l a , and a n t h r a c e n e by n i t r o c o m p o u n d s , q u i n o n e s , and c h l o r o c o m p o u n d s 4 7 1

.

Some triplet exciplexes have

been d e t e c t e d in o t h e r s y s t e m s h o w e v e r 4 7 2 .

Triplet state

p h o t o p h y s i c s and t r a n s i e n t p h o t o c h e m i s t r y o f c y c l i c e n e t h i o n e s , i n c l u d i n g t h i o c o u m a r i n , have a l s o b e e n r e p o r t e d 4 7 3 Q u e n c h i n g o f s t i l b e n e t r i p l e t by O2

.

in benzene gives

' O2

with

a n e f f i c i e n c y o f 18 f. 5 2 so q u e n c h i n g i s not e x c l u s i v e l y o n e s i n g l e 474 . Biphenyl enhances t h e rate of 9.10-dicyanoanthracene

process

sensitized p h o t o x i d a t i o n r e a c t i o n s by i n c r e a s i n g t h e

'

O2

yield475

.

S u b s t i t u e n t e f f e c t s i n t h e q u e n c h i n g o f a c e t o p h e n o n e and b e n z o p h e n o n e t r i p l e t s by 0 r a d i c a l s o n ' 0 2 generation'has

and t h e i n f l u e n c e d i - t e r t - b u t y l n i t r o x y been m e a s u r e d and t h e m e c h a n i s m

a n a l y ~ e d ' .~ ~ S i n g l e t O 2 g e n e r a t i o n by f u r o c o u m a r i n t r i p l e t s t a t e s varies f r o m 0 . 1 3 t o unity w i t h o u t g e n e r a t i o n o f 02 .

The use of cyanine

lo2 g e n e r a t i o n in o r g a n i c A b s o l u t e q u a n t u m y i e l d s o f lo2

dyes as alternatives to rose bengal for s o l v e n t s has been proposedi7'.

p r o d u c t i o n h a s b e e n d e t e r m i n e d by t h e r m a l l e n s i n g using s e v e r a l sensitizers including tetraphenylporphyrin, zinc 479 . Time resolved thermal

t e t r a p h e n y l p o r p h y n i n . and a n t h r a c e n e

l e n s i n g c a n a l s o b e used t o d e t e r m i n e q u a n t u m y i e l d s f o r p r o d u c t i o n o f t r a n s i e n t s w i t h l i f e t i m e s o f t h e o r d e r o f 1 t o 100 u s ie. s p e c i e s w i t h a l o n g e r l i f e t i m e t h a n t h e t r a n s i t t i m e o f a sound wave. Direct t i m e r e s o l v e d d e t e c t i o n o f l u m i n e s c e n c e at 1 2 7 0 nm


35

f r o m ' 0 2 has been used t o estimate sensitized singlet oxygen yields f r o m a series o f related p o r p h y r i n ~ ~ " .

Incorporation o f the

s e n s i t i z e r , dihaematoporphyrin ester ( D H E I into cetyltrimethylammonium bromide in 0 0 increases the yield of from 0 0 alone. DHE.

O2

This is attributed t o s t r u c t u r a l alteration o f t h e

i l e c t r o n transfer and ' 0 2 formation c o m p e t e in t h e 9 , l O -

d i c y a n o a n t h r a c e n e sensitized photooxygenation o f olefins4"

.

Microheterogeneous photooxidation can i n v o l v e enhancement of oxidation by covalently binding a sensitizer to a ligand complexing t h e acceptor

482

, for example r o s e bengal tethered t o $-cyclodextrin

enhances t h e photooxidation o f 1,2-diphenyl-p-dioxene. T i m e resolved studies have been m a d e o f t h e dynamics o f triplet state spectral d i f f u s i o n in the presence o f o r i e n t a t i o n a l and substitutional disorder in binary solutions4a3 .

For 1 -bromo-

4-chloronaphthlene and 1 , S - d i b r o m o n a p h t h a l e n e the spectral d i f f u s i o n is very concentration dependent and consistent with 2-dimensional excitation exchange interaction.

Steric e f f e c t s on

triplet energy transfer is not so m u c h d u e to limits on closeness of

m o l e c u l a r approach as limitation o n t h e twisting H systems w h i c h

m i n i m i s e s overlap for electron exchange according t o the findings o f S c a i a n o s t i ~ l . ~ Triplet-triplet ~ ~ . energy transfer between t h e s a m e species has been measured using deuterated a n a l o g u e s 4 a 5 .

The

c r i t i c a l transfer d i s t a n c e i s usually smaller for similar m o l e c u l e s than that for different molecules.

The quenching o f triplet

excited sensitizers by d i a r o y l peroxides apparently involves exchange energy transfer to the conjugated electronic systems o f peroxides486.

T h e fluorescence o f t h e furanoxy r a d i c a l can be used

to m o n i t o r triplet state energy t o t h i s s p e c i e s b a 7 .

OOMR

has been

used t o i n v e s t i g a t e t h e donor-acceptor pair orientation f r o m triplet-triplet transfer in frozen SDS micelles containing benzophenone and naphthalene-hg at 1 . 2 K 4 "

.

Quenching o f

anthracene and sodium anthracene-2-sulphonate triplets by s e v e r a l nitroxyl radicals in the presence of i o n i c surfactants g i v e s information on micelle-surfactant interaction on the p s t o ms t i m e scale4e9.

Triplet energy transfer involving $-ionone as acceptor

or donor i s another system ~tudied'~'.

Phosphorescence f r o m

biacetyl and benzophenone at surfaces has been induced by collision with the triplet state o f benzene produced by electron impact

491

.

The behaviour of g e m i n a t e triplet benzyl r a d i c a l pairs in anionic micelles has been investigated as a function o f added L n 3 + ions in the presence and a b s e n c e o f m a g n e t i c fields492. G e r m i n a t e

36

Photochemistry

r a d i c a l c o u p l i n g i s field s e n s i t i v e in t h e p r e s e n c e o f Ln3+ i o n s but u n a f f e c t e d by d i a m a g n e t i c ions.

A d e t a i l e d study o f t h e

m e c h a n i s m o f t h e p h o t o s e n s i t i z e d r e d u c t i o n o f m e t h y l e n e b l u e in a q u e o u s S D S m i c e l l a r s o l u t i o n s , u s i n g 1 0 - d o d e c y l a c r i d i n e o r a n g e has been r e p ~ r t e d " ~ . involved.

Both t r i p l e t e n e r g y and e l e c t r o n t r a n s f e r a r e

Excited t r i p l e t a c e t o n e i s g e n e r a t e d by t h e r m o l y s i s of

tetramethyldioxetane excites S2 xanthione4".

-+

So

e m i s s i o n f r o m a z u l e n e and

Only t h e t r i p l e t s t a t e t r a n s f e r s energy t o t h e S 2

state of the acceptor. A c t i v a t i o n o f u r o c a n a s e by e l e c t r o n i c a l l y excited t r i p l e t species occurs generated

495

.

For e x a m p l e , t r i p l e t i n d o l e - 3 - a l d e h y d e

by p e r o x i d a s e c a t a l y s e d o x i d a t i o n o f i n d o l e - 3 - a c e t i c acid

i s such an a c t i v a t o r .

T r i p l e t s i n g l e t energy t r a n s f e r o c c u r s in

the complex of auramine 0 with horse liver alcohol d e h y d r ~ g e n a s e ~ ~Many ~ . of t h e mechanistic details of peroxidase catalysed f o r m a t i o n o f t r i p l e t a c e t o n e and c h e m i l u m i n e s c e n c e f r o m i s o b u t y r a l d e h y d e and m o l e c u l a r o x y g e n h a v e a l s o been w o r k e d OU?.

A number of photochemical papers use physicochemical techniques which m a k e them relevant to this review.

These include

a study o f i n t e r m o l e c u l a r r e a c t i v i t y o f e x c i t e d d i p h e n y l m e t h y l radicals498, biradicals derived from the photodecomposition 499

2.2,6,6-tetraphenylcyclohexane

of

, and c h a r a c t e r i z a t i o n o f

transient i n t e r m e d i a t e s in t h e l a s e r e x c i t a t i o n o f c y c l o h e x e n o n e s in t h e p r e s e n c e o f a m i n e s S o 0 .

A comprehensive

examination o f the

picosecond d y n a m i c s o f P a t e r n o - B u c h i r e a c t i o n shows t h a t a 1 , 4 b i r a d i c a l u n d e r g o e s h e t e r o l y s i s t o a c o n t a c t i o n pairs0' A

.

very u s e f u l r e v i e w o f t i m e r e s o l v e d CIDNP and i t s

a p p l i c a t i o n t o r a d i c a l and b i r a d i c a l c h e m i s t r y has been prepared by c l o s s et .lSo2. C h e m i l u m i n e s c e n c e i s observed f r o m t h e t h e r m o l y s i s of trans-alkyl hyponitritesSo3.

of

a number

Excited s t a t e p r o d u c t i o n o c c u r s

via d i s p r o p o r t i o n a t i o n o f a l k o x y l r a d i c a l s w i t h i n t h e solvent c a g e f o l l o w e d by r e a c t i o n s o f t h e t r i p l e t state.

The mechanism o f

a q u a l u m i n e s c e n c e in a l k a l i n e l u m i n o l s t i m u l a t e d in v a r i o u s w a y s has been a n a l y s e d S o 4 .

S i n g l e t o x y g e n i s produced by S o y b e a n

l i p o x y g e n a s e i s o e n z y m e s in t h e o x i d a t i o n o f l i n o l e i c acid and i d e n t i f i e d by l u m i n e s c e n c e at 1 2 6 8 nrnSos. T r i b o l u m i n e s c e n c e o f E - a l k y l and E - a l k y l - 3 s u b s t i t u t e d


37

carbazole crystals has been related t o t h e crystal structureso6

.

Microsecond and nanosecond flash photolyses has been used t o study photochromic reactions o f spiropyrans o f the indoline seriesso7.

The photophysics, photochemistry, kinetics and

mechanism o f t h e photochromism o f 6‘-nitroindolinospiropyran h a v e New transients in the

b e e n i n v e s t i g a t e d by L e n o b l e a n d B e c k e r s o 8 .

1-10 ns time regimes have been detected and t h e triplet state gives t h e c i s o i d o p e n f o r m a l s o i n t h e t r i p l e t s t a t e w i t h i n 10 n s .

The

same authors have reported a n extensive study on photochromic 510 . Steric requirements

fulgidesSo9 and 2H-pyrans and chromenes

f o r p h o t o c h r o r n i s m a n d t h e r m o c h r o m i s m o f tj,lj’-bis(salicylidene) d i a m i n e s h a v e a l s o b e e n defined’”

.

References D.P.Craig and T.Thirunamachandran, Acc. Q&.m.

Res., 1986, 19. 10.

L.G.Arnout and S.J.Formosinho, J. Photochem,.

1985,

2.Smedartchina and F.Dietz, J. Photochem., 1985,

x,315.

2 ,13.

8.J.McClelland and A.Modinos, J. Chem. S O C . . Faradav Trans. 2 , 1985, 81, 673. 5

P.Suppan, Bectrochlm, Acta , 1985, 0 ,1353.

6

J.E.8rady and P.W.Carr, J. Phvs. CQ~QL, 1985, 89, 5759.

7

G.van der Zwan and J.T.Hynes, J. Phvs. C m , 1985,

8

R.I.Cukier,

9 10

Be,

4181.

a,5457. R.I.Cukier, J.Am. Chem. S O C . , 1985, m , 4115. R.E.Sassoon, Chem. Phvs. Lett., 1986, m , 74. J. Chem. Phvs., 1985,

11

J.J.Fisz, Chem. Phvs., 1985, 99, 177.

12

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Part 11 PHOTOCHEMISTRY OF INORGANIC AND ORGANOMETALLIC COMPOUNDS

1

The Photochemistry of Transition-metal Complexes BY A. COB 1.

Introduction

Reviews have solids,

appeared

on

the

of

luminescence

inorganic

photophysics of metal complexes,2'3 pressure effects on

photochemical react ions, compounds,

photoredox react ions of mixed-valence

photochemical

electron

transfer

react ions,

dipole-forbidden energy transfer processes in solution, and

of

mechanisms

hydrogen photogeneration photo-excited

react ions,8

me tallopor phyr in

metalloporphyr in-photosens it ized

format ion

of

from water ,lo exciplex

copper complexes,

' kinetics

hydrogen, quenching

of

photochemistry of transit ion

metal-organic systems,l2 photochemistry of metal-metal bonds, l3

-

photogeneration of cobalt ( I ) complexes,l4 photoisomer isation of

,

rhodium( I I I ) m i n e complexes

and cataly?is and photoelectro

chemistry on ruthenium disulphide surfaces .I6 The photodeposition of metallic catalysts on supports has also been discussed. l7

2.

.

.

Titanium

Intermed iates in colloidal t itania-catalysed photoreact ions have

been detected,18 and

a study of

the heterogeneous

and

homogeneous photoox idat ion of var ious organic cornpounda in both gas and liquid phases has associated the photocatalytic centre of the catalyst with the Ti-0 bond. During light absorption the Ti ion change8

its

oxidation

state

photocatalytic oxidation of

and

coordination

ethane has been

number.

studied

The

at room

temperature, and in particular the effect on the rate of ethane oxidation of the partial pressure of reactants, the W 57

light

58

Photochemistry

intensity, the amount of catalyst, and the residence time have all been evaluated.20

tracer study on the Ti0,-sensitized

An 0 '

photooxidation of aromatic compounds has shown that hydroxylation proceeds through two different reaction pathways depending on pH. At higher pH benzenes are attacked mainly by Hb formed by one-electron reduction of molecular oxygen with excited TiO,, and at low pH attack is by Hb formed from the h+ oxidation of water.21 4-Chlorophenol

has

been

catalytically photodegraded

in

the

presence of TiO, particles to give CO, and HCl quantitatively.22 The preparation of TiO, for use as a photocatalyst in the decomposition of water, acetic acid and isopropanol has been described23 and a simple method has appeared for the preparation of M/TiO, photocatalysts (M-metal or metal oxide).

This latter

method modifies not only the surface but also the internal electronic structure of the catalyst. 24 A complex formed by direct reaction between polymerised n-butyl orthotitanate and MeOH in benzene solution will catalyse the photodecomposition of water, and results involving the use of this catalyst alone and with added FeS0;7HZO presence of

or catalase have been compared.25 In the

plat inum/titania

photodehydrogenated

to

give

catalysts isopropanol has acetone

and

hydrogen

in

been equal

amounts26 and methanol has been photooxidised us ing a MoOJTiO, catalyst

comprising

a

molybdate

monolayer.

Although

the

photo-efficiency is about one fifth of the photoefficiency of pure TiO,, the selectivity for suppressing secondary oxidation is greater. 27

Dilute

aqueous

solutions

of

H,SO,

have

been

photooxidised by 0, in the presence of irradiated TiO, and the rate of oxidation is observed to be greatly enhanced when noble metals

are

deposited

on

the

TiO,

(Ru. I n s t . P h v s . Chem. R e s .

(an.),

98

M.

F.

1984, 78, 172. Gregory, p

99

1985,

Poliakoff,

and

J.

J.

Turner,

247.

R. Amadelli, C. B a r t o c c i , V. C a r a s s i t i , S. A i m e , D. O s e l l a , and L. Milone,

100

M.

A.

Gazz.. 1985, , m,

5. Goldman and D.

337.

R. Tyler, m r a . C h i m . A c t a , 1985,

B,

L47. 101 A . 5 . Goldman and D. R. Tyler, J . Am. Chem. Soq

-

r

1984, U.5,

4066. 102 K. 5 .

Schanze and T. J . M e y e r ,

m r a . Chem,,

1985, 24,

IIl2: The Photochemistry of Transition-metal Organometallic Compounds

137

2121. 103 C.

Daniel,

I. Hyla-Kryspin,

J. Demuynck, and A. V e i l l a r d ,

Nouv- J. Chlm., 1985, 9, 581. 104 M.

K.

Onishi,

Hiraki,

Kitarnura,

S.

Y.

Ohama,

YiurJon K a u U Ka i s h i , 1985, 400.

105 R. Y a n and H. Wang, W u e Xu-,

1985,

106 F. R. Anderson and M.S. Wrighton,

u, 654.

Inora.

ChglII=

1986,

t

25,

112.

Eaton,

107 B.

J.

King,

A.

K.

and

P.

Vollhardt,

C.

J. Am. Chem. SOG., 1986, .&Q@, 1359.

u., 1984,

108 G. A. Shagisultanova and A. V. Loginov, U o r d . ;Lp, 1675.

109 G. Zh.

A.

K. Ortigosa,

Shaglsultanova,

Flz.

Khm.,

110 P. Bougeard,

1984,

fia,

I.

Voyakin,

V.

2833.

Cooksey, M. D.

C.J.

and

Johnson, M. J. Lewin, S.

m.,1985, 288,

Mitchell, and P. A. Owens, J. Om-t.

349.

111 Y . Ohgo and

..J

S. Takeuchl,

Soc..

., 1985,

m*-C

21. 112 S. F. Clark, R. J. W a t t s , D. L. Duboia, J. 5 . Connolly, and J. C. Smart, w d . Chem. Rev., 1985,

u,273.

113 M. Hoshino and K. Yasufuku, m r a . Cham., 1985,

114 M.

I.

S.

Kenney,

,-

J.

Kenney,

W.

29, 4408.

0.

and

A.

Crosby,

1986,5, 230.

115 M. Hoshino and K.

Yaaufuku,

-.,

1985, JJ.2,

259. 116 M.

Hoshino,

J. PhYa. 117 Y.

I(.

H.

Sski,

and

Yamazaki,

H.

1985, SQ, 3080.

C-.,

Aoyama,

Yasufuku,

T.

Yoahida,

K.

Sakurai,

and

H.

Ogoshi,

138

Photochemistry Qraanometallics, 1986,

5, 168 -

118 H. Yamamoto, S. Shinoda, and Y. Saito, J. Mol. Catal., 1985,

30,

259.

119 T. Takahashi, S. Shinoda, and Y. Saito, J. Mol. Catal., 1985,

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535. 121 M.

D.

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P.

A.

MacNeil,

and

J.

S.

Rettig,

J. Am. Chem. S O C . , 1985, 107, 6708.

122 D. A .

Wink and P. C. Ford, J. Am.

Chem. S O C . , 1985, 107,

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R. Cutler, and C. P.

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Cusumano, G. Guglielmo, and V.

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Riahi, and J. P. Pete, J. Oraanomet. Chem . I

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Ito, J. Chem. SOC. Chem. C o m

. , 1985, 959.

3 The Photochemistry of Compounds of the Main GrouD Elements

-

BY A. COX

1. Introduction The photochemistry of

8

ilanes has been reviewed.

'

Measurements of the photodissociation dynamics of CO; show that in the energy range 1.95-2.2 eV fragmentation to CO, and 0occurs by two distinct mechanisms and involves three electronic states, the 'B, repulsive

LB,

ground state, a 'A,

weakly bound state and a

state . z

3 - AlkU Metals

-

The formation and dissociation of Kf, R b f , and Cs:

by ruby

laser radiation has been reported.

The photostability of boron-containing organic complexes has

discussed,*

been

properties

of

and

a

p-diketonates

study made of

of

disubstituted

the

luminescent

boron

and

of

bie-~-diketonatoboron. A novel photochemical alkyl migration from B to C in the dialkylboryl acetylacetonate complexes (1) ( R-cyclohexyl, Bu, isopinocampheyl, R'mH; R-cyclohexyl, Bur

R1=Me ) has appeared. Crossover experiments show that the alkyl migration is essentially intramolecular.6

5. Silicon A

report has appeared of the chemiluminescent gas-phaae

ailane-ozone system which incorporates a MO study supporting the conclusion that

the

important emitting

Reaction of atomic oxygen with Me,SiH 140

apecies

is

H,SiO.'

has been inveatigated by

IIl3: Compounds of the Main Group Elements

141

Me

S iM ezCMe3

\

Q’

(4)

OSiMej

142

Photochemistry

the discharge flow technique as well as by stationary photolysis exper iments

.

The pallad ium-catalysed ox idat ion of allyls ilanes

~ a novel with W and molecular oxygen has been d e s ~ r i b e d ,and photosubstitution reaction of dicyanobenzenes by allylic and benzylic silanes which occurs in homogeneous solution is reported to involve photoelectron transfer fromthe ailanes to the excited singlet state of the aromatic compound. lo Photolysis of SiH,-GeH, mixtures

has

been

studied

and

following

photodecomposition of SiH, to SiH, and H,,

primary

SiH, seems to insert

into an Si-H bond of SiH, or a Ge-H bond of GeH, to form Si,H, H,SiGeH,

respectively.

report

A

of

the

or

methylene-methyl

exchange in the reaction of triplet state methylene-d,

with

methylfluorosilanes has appeared12 and dimethyldiazidosilane is reported

to

be

matr ix-isolated

of

Irradiation

a

superior

photochemical

dimethylsilylene

MeN=CMeCH=C(OH)SiMe,,

(R=N,)

and for R=SO,Ph,

to

-

and

Me,CRCH,COSiMe,

precursor

l-methylsilene l3 in

hexane

gives

NCS, the product is the

.

pyrrolidine der ivat ive (2) l4 Evidence has been described for the primary formation of a benzyl-silyl radical pair and also for the mechanism

of

f ree-radical

+

1,2-(carbon

silicon)-acyloxy

migration following irradiation of acyloxymethyl(benzy1)silanes15. (R-9-anthryl) In benzene intramolecular

Photolysis

gives

9,lO:I' ,2'

(3)16 and

anthracene

bis( 9-anthry1)dimethylsilane

has

been

a

of

R,S iMe,

silicon guided

photodimerisation descr ibedl'.

An

in ESR

investigation of the photochemical reaction of aroylsilanes with phosphorus compound8 has appeared.

Two mechanisms have been

suggested, one involving fragmentation of an aroyl-Si bond and a second proceeding through a

siloxycarbene; the

experimental

IIN: Compounds of the Main Group Elements evidence

favours

the

Me,C(Me,Si)zSiCOQ

former

mechanism18.

(Q=l-adamantyl) which

Me,C(Me,Si)Si=C(OSIMe,)Q

Me(Me,SiO)Si=C[SiMe,CMe,]Q

an argon matrix

which

at

10

at

K

gives

the

of

silene

the

silene

spontaneously gives

the

n-Bonded silaacrylate has been isolated following photolysis of

10 K

Brief

pentamethyldisilanyldiazoacetate.

compound

Photolysis

photoisomer ises to

and

head-to-tail dimer (4). in

143

using

irradiation of

nm

240

ethyl

radiation

this

leads

to

(ethoxydimethylsilyl)(trimethylsilyl)ketone. 2o trans-l,2-Bis ( (trimethylsilyl)amino]-1,2-dimeaityldisilene and trans-l,2-di-tert-butyl-l,

2-dimes ityldis ilene

undergo photoisomerisations at 254 and 350 nm to give products having cis-enr ichment. mixtures

of

trens-and

25'C,

At

these revert to equilibrium

cis-disilenes. 21

TCNE

decomposition of the oxas ilacyclopropane (5) (R the carbene (6) and R,SiO, direct photolysis of

photosensitized

-

mesityl) gives

but by contrast DCA sensitized or

(5) gives R,Si

and

It has been

(7).

suggested that the first process involves an exciplex and that the

second

may

Photocleavage of

involve

a

rapid

back-electron

transfer.22

hexa-tert-butylcyclotr isilane catalysed by Pd

salts is reported to give (Me,C),Si:

and (Me,C)zSi=Si(CMe,),.23

Singlet methylene has been inserted into l-methylsilacyclobutane to produce an activated 1,l-dimethylsilacyclobutane (8). decays

to

products

whose

distribution

is

This

virtually

indistinguishable from that obtained by activating (8) with 254

nm photons.24

A

study has

been made

of

the photolysis of

1,1,3-tr imethylsilacycl~butane~~ and of 3-phenyl-Q-[phenyl(trimethylsilyl)methylene]-l,l,2-tris(tri-

Photochemistry

144 Me

Me

Me

Me

Me Me

IIl3: Compounds of the Main Group Elements

145

methyls ilyl)-1-8ilacyclobut-2-ene .26

Photoreaction

peralkylcyclotetraailanes, (R'R'Si),

CH,SiMe,)

in

hydrocarbon

(R' = RL

solvents

gives

-

CH,CHMe,,

the

of CHMeEt,

corresponding

cyclotrisilanes and the disilenes (R1R2Si:SiR'R2),27 and in the presence of CC1,

or CHCl,,

photolysis of

dodecaaxnethylcyclohexasi lane abstraction from

the

r esu Its

leads to

chloroalkanes by

Photolysis of the cyclotrigermane (R,Ge),

suggest ing

C1

dimethylsilanediyl.28 (R = 2,6-Et,CeH,)

gives

.

bis (2,6-diethylphenyl)germium ( I I ) 29

L-uhaml Meaeurements of the quenching rate constant between N,(ASC, u'=O)

and SO (x'f)

at room temperature suggest that the SO t N,(A)

excitation transfer process appears to be an efficient system for utilising the electronic

energy

quenching,

of

the metastable N,(A)

rotational

relaxation,

The and

radiative

u'-0 N ' ) have been measured31 and

lifetime of imidogen (NH)(A%,

vibrationally excited NOCl* has been observed via its strong cont inuous absorpt ion in the 230-280 nm reg ion following partial flash photodissociat ion of gaseous NOCl mixtures.

Format ion of

NOCl* is attributed to a vibrational energy transfer from C1,* which

itself

arises

by

reaction

of

C1

with

N O C L ~ ~

Photodissociation of methyl nitrite at 248 and 350 nm has been examined in a molecular beam and average translational energies compared with the results of a recent investigation of the NO internal state distr ibutions.33 7.

ow-

Reaction of oxygen (O('D)) with NO has been shown to be primarily an energy transfer process.34 and results of the L I P monitoring of ground state NH,

kinetics after pulsed laser 0,

Photochemistry

146

photolysis in the presence of NH, have been recorded.35, 36 Photolysis of a complex formed by codeposition of Me1 and 0, in an argon

matr ix

gives

iodosomethane

which

following

further

photorearrangement leads to a HCHO-HI molecular complex. The IR 37 spectra of this complex and of iodosomethane are reported. Sulphur

atoms

produced by

photolysis of

an Ar

matrix

containing OCS at 20 K have been found to react with PX,(X=P C1) and with the hydrocarbons CH,,

CzH,,

and C,Hz,38

or

and liquid

sulphur has been photochemically oxidised by Pe( I I I) at 150*5°.39 Calculations have been performed on species relevant to the photoionisation of the Van der Waals molecule (H,S),40

and the

photochemical reaction between SF, and F, at 365 nm and within the range 213-214 K is a chain process which gives SP, and SzF,, aa the only products.' *

Sulphur dioxide has been photoox id ised at

365 nm by 0, and proceeds via formation of the excited triplet state of ~0,.42 8. HalOaen8

Quantum yields of luminescence of iod ine chlor ide, xenon chloride, and xenon iodide have been measured in the presence of var ious

buffer

gases43

and

chlor ine

monof luor ide

has

been

synthesised by pulse phOtOly818 of stoichfometric mixtures of

.

gaseous chlor ine and f luor ine 44 SF,-sen8 it ized decompos it Ion of CH,I and cDsI

proceeds faster with the latter compound as a result

of a different distribution of energy levels in the Visible

radiation

photolysing CF,f

(A-450 nm)

is

reported to be

capable of

molecule8 which have been subject to strong IRMP

exc itat ion,46 and the distr ibut ion of photof ragmentat ion products of CH,I

resulting from irradiation at 249 nm i n ~ e s t i g a t e d .ESR ~~

studies of the photolysis of halogenated compounds in glassy and

1113: Compounds of the Main Group Elements

polycrystalline matrices results

of

a

have

study of

the

147

been

descr ibed48’

photooxidation of

and

49

CF,ClBr

the have

appeared.50 Photodissociation of the matrix isolated molecular complex CF,I-0,

at wavelengths greater than 470 nm gives CF,IO

whereas within the range 240-220 nm irradiation leads to CF,OI and

two CF,O-IF

homolytic

molecular complexes.51 The kinetics of

the

Pr, Me,CH,)

by

substitution of

R,SnI

(R-Me, Et,

photochemically generated iodine atoms have been measured52 and gas phase photolysis of a mixture of CC1, and silicon-containing compounds such as Me,SiH

or Me,ClSiH

gives products resulting

from abstraction of a hydrogen atom from the o ~ g a n o s i l a n e . ~ ~ 9. Miscellaneoua Photo induced react ions of benzyltr imethylt in with methylt in chlor ides54 and of tr iphenylgermane and l-naphthylphenylmethylgermane

have

been

.

descr ibed 55

Some

results obtained by flash and modulated photolysia experiments on several related gas phase reactions between fluorooxygenated compounds and CO have appeared,56 and chemiluminescence has been observed during oxidation of XeF, MO(CO)~,W(CO),,

by metal carbonyla such as

Fe(CO), and some of their de~ivatives.~’

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SSSE ,

Part 111 ORGANIC ASPECTS OF PHOTOCHEMISTRY

1

Photolysis of Carbonyl Compounds BY W. M. HORSPOOL

The interest in the photochemical behaviour of simple carbonyl compounds continues t o wane, a trend which has been detectable for a number of years. Several reviews which are of general interest to photochemists have been published during the period covered by this survey. Thus Scharf and his coworkers have published an account dealing with the energy storage of light and the synthetic uses of light in organic systems.' Coyle2 has reviewed some aspects of organic photochemistry and Horspool has reported on matrix isolation techniques and electron transfer reactions applied to organic photochemi~try.~Ramamurthy4 has published a review of the photochemistry of thiocarbonyl compounds and Xu and Wu have reported on some aspects of the Zimmerman-Mobius-Huckel approach to the interpretation of concerted react ions.5

1

Norrish Type I Reactions

There has been considerable interest on the influence of zeolites on several aspects of the photochemical behaviour of ketones. Turro et al. have carried out further work on the influence of zeolites on the photochemical activity of dibenzyl ketones. In this study pentasil zeolites were used.6 In other work Turro has reported the use of triplet-triplet energy transfer as a probe of surface diffusion rates.' The luminescent properties of some aromatic ketones in the presence of the hydrophobic zeolite Silicalite have been examined' and a spectral study of transients formed by the irradiation of aryl ketones in zeolites has been reported.' An examination" of the behaviour in the solid state of guest molecules such as aliphatic ketones ( acetone and ethyl methyl ketone) and aromatic ketones (acetophenone and mC1-acetophenone) in deoxycholic and apocholic acids has identified stereospecific addition of the guest molecules to the host by a hydrogen abstraction radical combination path." A flash photolytic study of fluorenone has shown that the triplet state reacts with electron rich alkenes in an electron transfer process.12 Norrish type I cleavage of benzyl ketones has been studied in detail using the CDNIP te~hnique.'~Excited state cleavage of the RT* state of the enone (1) in

155

156

Photochemistry

methanol/methyl hbutyl ether results in the formation of the radical pair (2) which recombines affording the ketene (3). This is trapped by methanol as the ester (4). 1,1,2,2-Tetraphenylethane is also formed as a minor product by combination of diphenylmethyl radicals. Other minor products such as methyl diphenylacrylate and the indanone (5) were also identified. The presence of the ketene (3) was demonstrated in the i.r. following photolysis of (1) in benzene.14 The substituted cyclopentanones (6) undergo normal Norrish Type I fission to yield the more stable biradical where fission has occurred between the carbonyl carbon and the substituted ring carbon. Disproportionation then follows to afford the E and 2 alkenes (7).15 Norrish type I reactivity is also observed on irradiation of the ketone (8a). In this example rebonding within the biradical brings about epimerization at C-13 to yield the product (Sb)." The steroidal ketone (9) is photochemically reactive and undergoes Norrish Type I fission in alcohol solution to afford the products (10) and (11). These products are the result of fission of the two a-bonds of the carbonyl group. This results in the formation of the appropriate ketenes which are subsequently trapped by solvent as the esters." Fetizon et aL" reported that irradiation of a mixture of the ketones (12) and (13) gave the enone (14) by a Norrish type I1 path. A reinvestigation of the photoreactions of the individual ketones has shown that the enone (14) is not formed. In this new study the transketone (12) yields the aldehyde (15) by Norrish type I fission and the cisketone (13) undergoes slow reduction yielding (16). Ring size appears to have Borne influence on reactivity as seen in the ring opening of the cicketone(l7) by the Norrish Type I route giving the aldehyde (18).19 Norrish Type I photoreactivity of the ketone (19)yields the aldehyde (20) which was used as an intermediate in the synthesis of (-)seco longifolenediol.20 The irradiation of the hydroxy ketones (21) in benzene yields the lactones (22) and (23) in a ratio of 96:4. The formation of these products is the result of Norrish type I fission followed by the formation of a ketene which is trapped intramolecularly. The loss of stereochemistry of the site next to the carbonyl group means that the alkyl radical centre does not retain its configuration during the hydrogen abstraction process. This is different behaviour to that exhibited by the steroidal analogues.21 An example in the steroidal system has been reported by Scharf and his coworkers who have observed that the irradiation of the steroid (24) results in the formation of the lactone (25) again by intramolecular trapping of the ketene (26). The presence of the ketene was demonstrated by trapping in methanol to yield the ester (27).22 In related work Stiver and Yates have studied the photochemical behaviour of the steroidal ketone (28). This ketone (28) undergoes Norrish type I fission to afford the biradical (29) which disproportionates to afford the ketoaldehdye (30). This compound is also photoreactive and is converted by Norrish type I1 reactivity into the fragmentation product (31). The path followed in this reaction, and which differentiates it from the previous

157

ZIIIl: Photofysis of Carbonyl Compounds

'h

Ph

Ph

Ph

) I

Ph

Ph

(1)

eM( , .Ph +}

Ph

Ph

Ph

Ph //C/'O

Ph

(3)

@

&

R2

Ph

(41

0 (5)

(6)

R' = H, Me,Et, Pr, MezCHCH2

R2= CN, COzMe

( 7 ) R' =H,Me, Et, Pr,Me,CHCH,

R2 =CN, C%Me

( 8 ) a; R = p - M e b; R = a - M e

LfPCSCH

0

H

Photochemistry

158

Q Qo m H

Ho 0

0

H

0

IIIIl: Photolysis of Carbonyl Compounds

159

0

Q-j?

‘

(30)

0

H

OHC) (31 1

Ph Ph

Ph Ph Ph

Ph

Ph

l l e h p h

(33)

(34)

(35) a ; n = 2 b;n = 1

160

Photochemistry

examples, is dictated by conformational factors.23 Photo-decarbonylation of the cyclohexanone (32a) is efficient with a quantum yield of 0.9. The reaction yields the two products (33) and (34) in a ratio of 1:2. The cyclopentanone (32b) also decarbonylates photochemically but is less efficient with a quantum yield of 0.5. A laser flash study has been carried out on these systems and has identified the biradicals produced by the Norrish type I process. The lifetime of the biradicals (35a) and (35b) are 0 . 9 ~ sand 0 . 5 ~ sr e ~ p e c t i v e l y . ~In~ a related study the photodecarbonylation of cis and trms2,6-diphenylcyclo-hexanone has been shown to yield a mixture of cis and tran41,2-diphenyl-cyclopentane and cis and trans1,5-diphenyl-pent-l-ene. The product yields did not depend upon the configuration of the starting ketone. The reaction is a standard Norrish type I process leading to was less stereospecific than decarbony lation. Interestingly recombination disprop~rtionation.~~ Johnston and Scaiano have studied the photochemical behaviour of the biradicals (35a) formed by the decarbonylation of the ketone (32a). The laser excitation of the biradical (35a) affords the new product. (36). This is formed by the path outlined in Scheme 1 involving cyclization and hydrogen migration.26 The irradiation of the cyclanone (37) in a variety of solvents leads to products, enals, of Norrish type I fission and disproportionation within the biradical. No evidence for the formation of cyclophanes (38) was obtained. In contrast, the larger ring cyclophanes (39) gave good to excellent yields of the cyclophane products with little of the more conventional products being detected. The formation of the cyclophane products is presumed to arise by pa-coupling of the biradical followed by rearomatization by hydrogen migration. The study was extended to examine the behaviour of the cyclanones (39) encapsulated in a zeolite.27 The ketocyclopropane (40) photochemically rearranges into the cyclo-octadiene (41) which itself is photoconverted into the isomeric compound (42). The formation of the cyclo-octadiene involves the ring opening of the cyclohexenone and the cyclopropane moieties t o afford the ketene (43),28 Another mode of reaction for small ring cyclic ketones involves Norrish Type I fission and rebonding to afford the ring expanded carbene. Pirrung has reported the use of this photo-ring expansion of cyclo butanones via the oxacarbene path in the synthesis of bicyclic acetals. The results of this are shown in Scheme 2.29 The optically active ketone (44a) follows the same photochemical path giving a carbene which is trapped intramolecularly as the ketal (45). An additional reaction mode, that of retro (2+2) addition, also occurs yielding the intermediate ketene (46) again trapped intramolecularly as the optically active lactone (47). These products are formed in a ratio of about 1:l. The irradiation of the isomeric ketone (44b) undergoes primarily retro (2+2) fragmentation to afford the lactone (48). The ketone (49) is also photoreactive giving

161

IIIi1: Photolysis of Carbonyl Compounds

(36) Scheme 1

(37)

(38)

H (40)

(39)n = 5,6,7 or 10

(41)

Photochemistry

162

Me

M

aC 0 2 M e (42 1

(43)

R'

MeO ~

o

'

R'

R2

H d; R ' = H, n = 2 , R 2 = H b; R 1 = Me, n = 1 , R2 = H C ; R' = H, R 2 = CN, /I = 1

Me0

+

Htf

Scheme 2

A

CO 2M e

Me

Me

Me H

Ri

@Me

R2

(45 1

( 4 4 ) a; R' = OH, R 2 = H b; R' = H, R 2 = OH

0

kMe Me

bH

Me

(46)

(47 1

~

IIZII: Photolysis of Carbonyl Compounds

163

H

HO’’ (50)

(49)

Me-‘

Me

151)

(53) R’ = H,Me E t ; R 2 = H

0

( 5 7 ) n = 1, 2,3

0

%

OR*

Ph

Ot

4

\

OH

Photochemistry

164

fiAr 0

(61) a; R' =OH, R 2 = Ar b; R' = A r , R2 = O H

( 6 0 ) Ar = p - MeOC6H5

,KN U R:f

(62) a;

R' = R 2 = H

b ; R' = R 2 = M e C ; R ' = R2 = P h d ; R' = MeO, R 2 = H e;

R' =EtO,

R2=

H

(63) a; 48% b ; 59"/0 c ; 11 V

O

d ; l6V0 e ; 26'10

0 ( 6 4 ) a; 0% b; c; d; e;

Oe/* 51Ye 31 *I* 56%

0 ( 6 5 ) C; 66'10 d ; 57% e ; 65%

%

Ph

(66) a; n = 1

b ; n= 2

(67)

I I I / l : Photolysis of Carbonyl Compounds

165

the ketal (50) and the lactone (51).30 The crystal structure of phototetrahydrozexbrevin (52) has been determined.31

2 Norrish Type 11 Reactions A study of the photochemical behaviour of a variety of ketones (e.g. 53) in Dianin’s compound (54) has been carried out. The conclusion is reached that the environment of the ketone included in the clathrate is non polar in character. The ratio of acetophenone to cyclobutanols obtained from the irradiations is not any different from those obtained from irradiation in Fragmentation is also observed on irradiation (at 254 nm) of the bile acid derivative (55). This brings about side chain degradation by a Norrish type I1 process to yield (56).33 A study of the photochemical Norrish type I1 process in the ketones (57) has shown that hydrogen abstraction follows the reactivity pattern of cycloheptane > cyclopentane = cyclohexane > cyclobutane. The hydrogen abstraction rate constants in solution do .not correlate with abstraction geometries determined by X-ray methods. The authors suggest that the hydrogen abstraction occurs from non-minimum energy conformations of the reactant.34 y-Hydrogen abstraction dominates the photochemistry of the ketone (58) affording the cyclobutanol (59) as the principal product.35 A comparison of the photochemical behaviour of the ketone (60) in benzene or acetonitrile with its behaviour in the solid In benzene solution the irradiation affords the two state has been carried out. cyclobutanols (61a) and (6lb) in a ratio of 2.6:l. The formation of the more hindered cyclobutanol (61b) predominates when the reaction is carried out in the solid state. The ratio of products in this instance is 051. The authors suggest that in solution conformational isomerism in the biradical is faster than bond closure while in the solid state the biradical is restricted to the conformation which gives rise to the more hindered product .36 The synthesis of p-lactams continues to be of interest. Sakamoto et a1 have studied the reaction of the thiazines (62) towards this end. On irradiation of (62) in benzene at temperatures > 4OoC elimination of the side chain affords (63) while cyclization yields (64) in reactions dependent on the substitutions pattern. At lower temperatures a different process occurs affording an unstable lactam which could be isolated as the

derivative (65).37 The Norrish Type I1 behaviour of the ketoaldehyde (%a) has been described by Ounsworth and Scheffer. The irradiation of the compound in benzene or moist acetonitrile through a Pyrex filter results in the formation of acetophenone and the ketobutanol (67). Under optimum conditions the yield of the cyclic product is 70%. The quantum yield for the formation of this product is 0.3 in benzene and 0.4 in

Photochemistry

166

A' (72) R' = M e or H

R3

R2

0

0 PhuNARf

+

+

Ph'.S.

(R1

It;' I

CH,R~

a; 29 ' l ~

R3

(73) a; R' = R 2 = R3 = H b ; R' = Me, c ; R1 = Ph, d ; R1 = Ph, e ; R' = Ph,

R2 = R3 = H

R2 = R3 =Me R 2 = Me, R 3 = H

b ; 27 ' l o

a ; 57 ' l a

c ; 86'10 d ; 71 '1. e ; 20 ' l o

b ; 66 ' l a c ; 11 'I'

R2 = R3 = H

d ; 28 '10

e ; 72 ' l o Scheme 3

RZCHC02R3

I

R2

kNk2,.' I H o d : '

Ph

R1 H

R

Ph"

Ph R = tosyl or benzyl ; R' = H, Me, Ph ; R 2 = H, Me, Ph;

(75)

(76)

R3 = Me, Et

(77)

Mil: Photolysis of Carbonyl Compounds

167

(78) R' = E t , R 2 = M e

R' = R2 = Me R' = Me, R2 =Et

R3 R 2 J 5 y M e

(81)

R' = R 2 = H , R3= H or Me (82) R' = MeO, R 2 = H, R 3 = Me R' = MeO, R2 =Ph, R 3 = PhCH, Me

I

Me

Me

Scheme 4 Me

Me

0

Me

0

168

Photochemistry

acetonitrile. The keto aldehyde (66b) also shows the same behaviour and on excitation undergoes abstraction of the aldehydo hydrogen to afford (68) as the product of cyclization!' The irradiation of ortho-kbutylbenzophenone affords the indanol (69) by way of &hydrogen abstraction from one of the kbutyl methyl groups. The quantum yield for the process varies from 0.04 in hexane to unity in methanol. Cyclization is also reported for (70) which yields (71) with a quantum yield of 0.35 in benzene. Details of a laser flash study of the transients involved were also reported.3g This recent work supplements the account originally reported in note f0rm.l' Hasegawa et al. have studied the photochemical behaviour of a series of alkyl oxamides (72, 73). The compounds are reactive from the triplet state and undergo hydrogen abstraction of the Norrish Type I1 type. y-Hydrogen abstraction is the only reaction of the oxamides (72) yielding the fragmentation product (74). Changes in substitution brings about competition between y- and &abstraction as shown in Scheme 3 resulting in Henning and his coworkers have fragmentation or the formation of pyrr~lidinones.~~ continued their study of the photo behaviour of amino ketones (75). In these examples irradiation brings about the formation of the cyclopropanols (76) and the In benzene and cyclohexane the hydroxyprolies (77) in non-polar solvents. hydroxyprolines (77) are f a v 0 ~ r e d . l ~ Photeenoliiation Reactions.- Pete et af. have reported that the photodeconjugation of the esters (78) in the presence of (-)-ephedrine leads to a product (79) where there is a small enantiomeric exce~s.4~ Photoenolization of the acetophenone derivative (80) has been studied. The structure of the product formed, after methylation of the react ion mixture, was identified as 4-benzy1-6-hydroxy-2-methyl-5-phenyla~etophenone~~ Bolivar et a/. have made use of the Diels-Alder trapping of the dienes (81), produced by the photo enolization of the ketones (82), in the synthesis of naphthalene derivative^.^^ The predominant product formed from the irradiation of the ketone (83) in methanol is the indanone (84). This ketone is accompanied by the three products shown in Scheme 4. The formation of the indanone and the dechlorinated product arise from a photoenolization path. The other two products are thought to be the result of expulsion of chlorine either as an atom or as chloride. The products of the latter type are suppressed with chloroketone (85). In this instance the only products formed are those resulting from the hydrogen abstraction path.lG The ability of polyketones, e.g. (86) to undergo cyclobutene formation by Norrish type I1 hydrogen abstraction/recombinanationhas been studied.17

3 Oxetan Formation The mixture of products (87) and (88) is formed on irradiation of furan and benzophenone in benzene at OOC. The structures of the products were established by X-ray and by chemical and spectral studies.18 Biacetyl adds photochemically to the

169

IIIII: Photolysis of Carbonyi Compounds

Bu"0

0

68""

(91)

(90)

BffO

X0+ 0

(94)

(93)

CO 2R

Ph

b; R

(97)

( 96)

(95) a; R = H

R = (-) 0- phenyI mnthyl

= Me

0 Q C\

( 98)

>:

C1 CL

0

y:

CI

CI

COzR

(99)

(100)

(101)

Photochemistry

170

Ph

t 102)

(103)

(106) Scheme 5

a;xPh 0

0

ph&

Ph Ph

O K N

0

(110)

.

N

'R2

.

R' = Ph, Et, Pr',Bu' ; R2= H R' = R2 = Ph

(111)

0

(112)

(113)

OPh

IIIIl: Photolysis of Carbonyl Compounds vinyl ether (89) to yield the oxetan (90) as the major product.

171 The cycloaddition

occurs with reversal of the regioselectivity normally expected for oxetan formation. Minor products of the addition were identified as the vinyl ether (91) and the ally1 ethers (92), products which presumably arise by 1,Shydrogen transfer within the alternative biradical (93). A 3-alkoxyoxetan (94) is formed using the vinyl ether (95a) while a 2-isomer (96) arises in the photoaddition of biacetyl to the vinyl ether (95b). The authors suggest that an exciplex between the vinyl ether moiety and the triplet biacetyl directs photoaddition to that site!' Photochemical addition of fiRJR,4S)(-)-&phenylmethyl phenyi glyoxalate (97) to the dioxole (98) affords the oxetan (99). This has been used as a building block in the synthesis of an L-apio f~ranoside.~'

4 Rearrangement and Fragmentation Reactions Abdul et a/. have reported the remarkable isomerization of the ketone (100) into the compound (101).51 Direct and sensitized irradiation of the cyclopropylketone (102) leads to the formation of the cisisomer (103) and the two rearrangement products (104) and (105). The transcis isomerization is a normal event by ring opening of the cyclopropane ring followed by rebonding. The formation of the rearrangement products is thought to arise via the biradical (106) as illustrated in Scheme 5.52 The benzoxazinone (107) decarbonylates to yield (108) on i r r a d i a t i ~ n . ~ ~ The photochemical Photodecarboxylation of (109) provides a route to e~aftoljde.~~ decarboxylation of the lactones (110) provides a convenient method for the synthesis of l-azabicyclobutanes (111). The reaction is, however, restricted to those compounds with two aryl groups on C-2.55 The norbornadienone (112) has been produced in a matrix by the irradiation of the azo compound (113). These authors point out that the outcome of the irradiation is dependent to a large extent on the material of which the matrix is composed.56

Acknowledgements.- I would like to express my sincere thanks to Dr. Stephen Bell and to Mr. Mike Whitehead of the Department of Chemistry and the Computing Centre respectively of the University of Dundee for invaluable assistance with the computer compiling programs used in these reviews.

Photochemistry

172

5 References 1. H. D. Scharf, H. Leismann, and H. Koch, Photochem. Convex, (symp. 1, 1983, 133 (Chem. Abstr., 1985, 102, 203351). 2. J . D. Coyle, Annu. Rep Pmg Chem., Sect. B, 1984, 80 (B),141. 3. W. M. Horspool, Annu. Rep. Pro& Chem., Sect. C, 1985, 80 ( C ) , 87. 4. V. Ramamurthy, Org. Photochem., 1985, 7, 231. 5. J. X u and G. Wu, Youj Huaxue, 1985, 113 (Chem. Abstf., 1985, 103, 159800). 6. N. J. Turro, X. Lei, C. Cheng, D. R. Corbin, and L. Abrams, J. Am. Chem. Soc.,1985, 107, 5824. 7. N. J. Turro, M. B. Zimmt, I. R. Gould, and W. Mahler, J. Am. Chem. Soc.,1985, 107, 5826. 8. H. L. Casal and J. C. Scaiano, Can. J. Chem., 1985, 63, 1308. 9. F. Wilkinson, C. J. Willsher, H. L. Casal, L. J. Johnston, and J. C. Scaiano, Can. J. Chem., 1986, 64, 539. 10. R. Popovitz-Biro, C. P. Tang, H. C. Chang, M. Lahav, and L. Leiserowitz, J. Am. Chem. Soc.,1985, 107, 4043. 11. C. P. Tang, H. C. Chang, R. Popovitz-Biro, F. Frolow, M. Lahav, L. Leiserowitz, and R. K. McMullan, J. Am. Chem. Soc.,1985, 107, 4058. 12. J. Gersdorf and J. Mattay, J. Photochem., 1985, 28, 405 (Chem. Abstr., 1985, 103, 177904). 13. M. Laeufer and H. Dreeskamp, J. Mag. Reson., 1984, 60,357 (Chem. Abstr., 1985, 103, 36967). 14. W. Adam, A. Berkessel, E.-M. Peters, K. Peteres, and H. G. von Schnering, J. Org. Chem., 1985, 50, 2811. 15. J. Totrajada, B. Van Hemelryck, and J. P. Morizur, Bull. Soc. Chim. Fr., 1985, 243.

IIIIl: Photolysis of Carbonyl Compounds 16. G. Neef, G. Sauer, R. Wiechert, S. Beier, W. Elger,

D. Henderson, and R. Rohde, Eur. Pat. A p - . EP 129,499 (Chem. Abs.fr., 1985, 103, 6617). 17. J. R. Williams, P. L. Mattei, A. Abdel-Magid, and J. F. Blount, J. Org. Chem. 1986, 51, 769. 18. D. D. H. Manh, J. Ecoto, M. Fetizon, H. Colin, and J.-C. Diez-Masa, J. Chem. Sm., Chem. Commun., 1981, 953. 19. R. J. Batten and H. A. J. Carless, J. Chem. Sac., Chem. Commun., 1985, 1146. 20. N. Satyanarayana and U. R. Nayak, Swth. Commun., 1985, 15, 331 (Chem. Abstr., 1985, 103, 160713). 21. S. Stiver and P. Yates, Tetrahedron Lett., 1985, 26, 5501.

H.-D. Scharf, J. Photochem., 1985, 28, 443. 23. S. Stiver and P. Yates, Tetrahedron Lett., 1986, 27, 2215. 24. D. H. R. Barton, B. Charpiot, K. U. Ingold, L. J. Johnston, W. B. Motherwell, J. C. Scaiano, and S. Stanforth, J. Am. Chem. Soc.,1985, 107, 3607. 25. V. F. Tarasov, B. B. Klimenko, D.' B. Askerov, and A. L. Buchachenko, Izv, Akad. Nauk SSSR, Ser. Khim., 1985, 361 (Chem. Abstr., 1985, 103, 53559). 26. L. J. Johnston and J. C. Scaiano, J. Am. Chem. Soc.,1986, 108, 2349. 27. X. Lei, C. E. Doubleday, jun., M. B. Zimmt, and N. J. Turro, J. Am. Chem. Sac., 1986, 108, 2444. 28. A. G. Schultz, K. K. Eng, and R. K. Kullnig, Tetrahedron Lett., 1986, 27, 2331. 29. M. Pirrung, Angew. Chem. ht. Ed. End.,1985, 24, 1043. 30. H. G. Davies, S. M. Roberts, B. J. Wakefield, and J. A. Winders, J . Chem. Soc., Chem. Commun., 1985, 1166. 31. M. Soriano-Garcia, R. A. Toscano, E. Dim, and L. R. Hahn, Rev. Latinoam. Quim., 1985, 16, 112 (Chem. Abstr,, 1986, 104, 149187).

22. G. Hilgers, G. Beyer, and

173

174

Photochemistry

32. P. C. Goswami, P. de Mayo, N. Ramnath, G. Bernard,

N. Omkaram, J. R. Scheffer, and Y.-F. Wong, Can. J. Chem., 1985, 63, 2719. 33. G. Hilgers and H.-D. Scharf, Liebig Ann. Chem., 1985, 1498. 34. A. Ariel, S. Evas, N. Omkaram, J. R. Scheffer, and

J. Trotter, J. Chem. Soc.,Chem. Commun., 1986, 375. 35. R. Phaff, N. Bischofberger, P. Mathies, W. Petter,

B. Frei, and 0.Jeger, Helve Chim. Acta, 1985, 68, 1204. 36. S. Evans, N. Omkaram, J. R. Scheffer, and

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J. C. Scaiano, J. Am. Chem. Soc., 1985, 107, 1087. 41. T. Hasegawa, Y. Arata, K. Mizuno, K. Masuda, and N. Yoshihara, J. Chem. Soc., Perkin Trans. 4 1986, 541.

42. H. Haber, H. Buchholz, R. Sukale, and

H. G. Henning, J. Prakt. Chem., 1985, 327, 51 (Chem. Abstr., 1986, 104, 130228). 43. R. Mortezaei, F. Henin, J. Muzart, and J.-P. Pete, Tetrahedron Lett., 1985, 26, 6079. 44. R. A. Bolivar and R. Machado, Acta Cient. Venez., 1984, 35, 208 (Chem. Abstr., 1985, 103, 53632). 45. R. A. Bolivar, R. Machado, and C. Rivas, Acta Stzd. Am. Quim., 1984, 4, 29 (Chem. Abstr., 1985, 103, 160190). 46. W. R. Bergmark, C. Barnes, J. Clark, S. Paparian,

and S. Marynovski, J. Org: Chem., 1985, 50, 5612. 47. Y. Ito, N. Kawatsuki, B. P. Giri, M. Yoshida, and T. Matsuura, J . Org. Chem., 1985, 50, 2893.

IIIII: Photolysis of Carbonyl Compounds

175

T. Oshima, S. Mihashi, and Y. Iitaka, Yakugaku Zasshi 1985, 105, 19 (Chem. Abstr., 1985,

48. H. Itokawa,

103, 71213). 49. 50. 51. 52.

53.

H. A. J. Carless and G . K . Fekarurhobo, Tetrahedron Lett., 1985, 26, 4407. A. Nehrings, H.-D. Scharf, and J. Runsink, Angvw. Chem. h t . Ed. Engl., 1986, 24, 877. M. H. Abdul, L. Huelskaemper, and P. Weyerstahl, Chem. Ber., 1985, 110, 840. H. E. Zimmerman and R. W. Binkley, Tetrahedron Lett., 1985, 26, 5859. E. Tauer and K.-H. Grellmann, Chem. Ber., 1986, 119, 215.

54. G. B. V. Subramanian, A. Mehrotra, and K. Mehrotra,

Chem. hd. Fondon), 1985, 379 (Chem. Abstr., 1985, 103, 160267). 55. R. Bartnik, 2. Cebulska, A. Laurent, and

B.

Orlowska, J. Chem. Research (S), 1986, 5. 56. B. F. LeBlanc and R. S. Sheridan, J. Am. Chem.

Soc.,1985, 107, 4554.

3

L

Enone Cycloadditions and Rearrangements: Photoreactions of Dienones and Quinones BY W. M. HORSPOOL

1 Cycloaddition Reactions Intramolecular Additions.- A comparison of the influence of a trimethylsilyl group with alkyl groups on photo-cyclization reactions has been carried out using two sets of compounds (1) and (2). The irradiation of the enones (1) gave the bicyclic compounds (3), a l,!kyclization, shown in Scheme 1 accompanied by the esters (4). The esters are formed by 1,6-closure to the biradical ( 5 ) which then ring opens to a ketene and is trapped by solvent. In contrast, irradiation of the enone (2a) gave only the 1,5-cyclization products (6). Enone (2b) failed to yield products of this type but was photoreactive yielding the cyclopropyl ketone (7). The influence of the trimethylsilyl group on the reaction is not understood.'

Additions to Cyclopentenones. Considerable use is being made of intramolecular cycloadditions to cyclopentene systems to provide key intermediates for the synthesis of natural products or highly strained compounds. Several examples of this have been published this year. Thus the enone (8) undergoes intramolecular (2+2)-addition to afford the tricyclic ketone (9) which was used as the starting material in a synthesis of (4.4.5.51-fenestrane (10).' Intramolecular cycloaddition of the allene unit t o the cyclopentenone in the compounds (11) affords two products (12) and (13) the result of straight (2+2)-additi0n.~ The enone (14) undergoes efficient intramolecular cycloaddition using a uranium glass filter to afford the products shown in Scheme 2. At shorter wavelengths several unidentified products are formed. The cyclobutane ring in the cycloadducts (Scheme 2) can be ring opened to afford the spiro compounds (15) which can be used in the synthesis of pentalene derivatives! Photo-cycloaddition in the enone (16) yields the adduct (17) which was used as a key step in a new synthesis of stoe~hospermol.~ Adduct (18) is formed in high yield on irradiation of enone (19) in a variety of solvents.'

A detailed report of the reactions of bishomocubane and homocubane systems has been reported. The key step in the synthetic sequence is the photochemical ring closure of the enone (20) to yield the cage compound (21).7 The major compound from 176

11112 Enone Cycloadditions and Rearrangements

177 SiMe,

0 (1)

a; R b;

0 I

H

R =Me

( 2 ) a; R = H b; R = Me

( 4 ) a; 6% b; 87'10 Scheme 1 H

(3) a; 94% b ; 13 '/e

Photochemistry

178

H

Me

(14) Scheme 2

#

Me (17)

(16)

(1 5 )

(18)

4 Br 0

(1 9)

(20)

ZZZl2 Enone Cycloadditions and Rearrangements

179

the irradiation of the enone (22) is the (2+2)-cycloaddition product (23). Accompanying this is a minor product which has been identified as the cage structure (24). The authors discuss the formation of this compound that it is formed via a 3,5-allyl shift. They suggest that the intra molecular arene-alkene complex which gives a biradical yields an intermediate (26) which subsequently undergoes a yield the final product (24).8

and reject the possibility product (24) arises via an (25). Bonding within this photochemical 1,3-shift to

Additions to Cyclohexenones. Intramolecular additions in cyclohexene systems also provide access to natural products. Thus the photocyclization of enone (27) affords the adduct (28) which is suggested as a route to the nortaxane or taxane ~ k e l e t o n . ~ Intramolecular reaction of the enone (29) affords two products (30,70%) and (31, 14%). The identity of the major products was determined by X-ray crystallography and is the result of hemiacetalisation of the original (2+2)-adduct (32). The minor product (31) is formed from the major by a retmAldol reaction." Cycloaddition occurs on irradiation of the alkenyltropone (33) in acidic methanol not in aprotic solvents. The products from the addition are the (6+2)- (34) and and (8+2)-adducts (35). The reaction is complicated in terms of the re+ sterwchemical outcome as shown in Scheme 3. To account for the products authors propose that two conformers (36, 37) of the tropylium species are involved."

but the the the

Intermolecular Additions.- Open Chain Systems. The involvement of a singlet exciplex is proposed in the selective photoaddition of 2,3-dimethylbut-2-ene to the transnitrile (38) yielding the (2+2)-adducts (39).12 The photodimerization of (40) affords the cyclobutane derivative (41).13 The de Mayo addition reaction continues to be of considerable value for the formation of precursors for further synthesis. One example of this is the formation of the photoadducts (42, 43), prepared by photoaddition of isoprene to the enol of the dione ester (44), and have been used in a general synthesis of cyclopentenes. The photoadducts (42, 43) are produced in the standard fashion by the formation of a labile cyclobutane which subsequently ring open^.^^^^^ Takeshita et al. have reported the photochemical addition of myrcene (44A)to the enolate ester (45). The normal mode of addition is accompanied by a minor product which has been identified as (46). This product is formed via a proton transfer step within the initial photoadduct (46A). The yield of the adduct (42) is 28% when the reaction is carried out at -35OC but is only formed in 20 % yield at 0 to 50C.16 Photoaddition of the ynone (47) to 1,l-diethoxyethene gave the oxetan (48) (so%), by a conventional (2+2)-cycloaddition route, as well as the furan derivative (49) (18%). The formation of this latter product arises by way of the carbene (50), itself a product of (3+2)-addition of the ynone to the alkene. Intramolecular trapping of the carbene

180

Photochemistry

Me

Br

&

(24)

( 2 5)

(26)

fi OH

(29)

(30)

181

IIIi2 Enone Cycloadditions and Rearrangements

+

+

f

Scheme 3

Ar

/J?*

% Ar

A r = m - Br, m - C I , p - C I , m - O M e , p - O M e , m - N O z and p - N O z C 6 H ,

(38)

(39)

COPh COPh

\

RO, C

rco X Ar

Ar

Photochemistry

182

COzMe

(44A)

(46)

(45)

OEt

Ph

OEt OEt

(49)

(50)

(51) R'

= OEt, R Z = H

R ' = H, R Z = OEt


183

BU'

But

(52)

(53)

H

HO

0

Me

-

(+I (63)

'Me

Photochemistry

184

affords the isolated product. The ynone also adds to ethoxyethene yielding the isomeric oxetans (51) and the corresponding (3+2)-adduct (52). In both these examples there is a preference for the (2+2)-cycloaddition mode. However, when but-2-yne is used as the olefin component in the cycloaddition, the (3+2)-adduct (53) was obtained in 60% yield.17

+

Cyclopentenones. Phot- (2 2) -cycloaddit ion of 1,l-die t hoxyet hene to cyclopentenone yields the adduct (54). Subsequent involved chemical transformations were used to complete a total synthesis of racemic Ag(12)-capneffene.’8 The cyclopentenone (55) photochemically ( a laser source) adds hex-l-yne to yield the cycloadduct (56) in good yield. By using a Pyrex-filtered Hg arc lamp the same starting materials yield the tropovalene (57) (25%) and the bicyclic product (56) (38%). Independent irradiation of the tropovalene (57) yields the tropone (58) (83%). The cycloadduct (56) can also be converted into the tropone (58) by A120, catalyzed elimination of acetic acid followed by irradiation of the enone (59).” Meyers and Fleming have reported a synthesis of (-)-Grandisof (60) commencing with photochemical (2+2)-addition of ethene to the chiral enone (61). This yields the adduct (62) in 93% yield contaminated with 7 4 % of the endoisomer. Ring opening of the adduct (62) affords the two keto esters (63) and (64) in 45 and 55% respectively. The former is taken on to complete the synthesis of GrandisoL20 A study of the influence of silica gel surfaces on the photochemical addition of allene to a series of cyclic enones has been carried out. Using this technique cycloaddition occurs to the more hindered face of the enone.21 A typical example of allene addition, where addition takes place to the less hindered face, is reported by Piers et af. in the photoaddition to the enone (65) which affords the four isomeric products (66) in ratios of 40:51:6:3. The two major products (66a) and (66b) were used as starting materials for total syntheses of naturally occurring compounds of the stemodane type.22 (2+2)-Cycloaddition of 1,2-dichloroethene to the enone (67) affords, after elimination of chlorine, the adduct (68).23 Cyclohexenones. A short review has been published dealing with the cycloaddition reactions leading to the formation of (+)-fongrblene and Corey’s lact0ne.2~ Phot-addition of ethene to 3-methylcyclohex-2-en-l-onegives the (2+2)-adduct (69).25 Lange and Lee have described a route to Germacranolides starting from the photoaddition of cyclobutene carboxylic acid to the enone (70) to give the adduct (71) in an overall yield of 58%. This was elaborated to afford the Germacranofides.2G Photocycloaddition of the cyclobutene (72) to cyclohex-Zenones provides adducts (73) which are useful in the synthesis of decalins. The functionalisation of these decalins makes them useful precursors for the synthesis of some natural products.27

185

HI12 Enone Cycloadditions and Rearrangements

I

Me

0

(69)

(68) Me

Me

*Me COOH 0 (70)

COOMe

(71)

OSiMe3 OSiMe,

R (73)

Photochemistry

186 Asymmetric

induction

in synthesis continues to receive attention as in the

photoaddition of cyclopentene to the optically active enone esters (74). The (2+2)-cycloadducts obtained are claimed to have substantial enantiomeric excesses. The adducts are diastereoisomeric and two types are obtained, the cisanticis (75) and the c i s s p c i s (76). Analysis of the results shows that the yield of the cisaaticis isomers diminishes as the size of the ester group increases due to steric interactions.28 The photochemical addition of ethene at O°C in methylene chloride to the enedione (77) affords a high yield of the adduct (78). This was converted to the monochloro derivative (79) which also undergoes photoaddition of ethene to yield the bisadduct (80). This on elimination of HC1 yielded the quinol (81) which can be oxidised to the quinone (82).29 Cycloaddition of alkenes (cyclopentene, cyclohexene, and cycloheptene) has been carried out to the same enedione (77) to yield the adducts (83).30 Iyoda et al. have also described a convenient synthesis of the bicyclo-octanediones(84) by a photochemical addition of alkenes to the enedione (77). The adducts (84) can be reduced by zinc in acetic acid to the desired products. Cycloaddition of ethyne to the same enedione followed by reduction affords the bicyclooctanes (85). The photoaddition of alkenes to the dibromo-enedione (86) is also effective and yields, after reduction, the adducts (87). 31 The de Mayo reaction with cyclohexa-l,3-diones is a method which still attracts interest as a synthetic approach to natural products. Typical of this is the short route to hirsutene (88). This involves photoaddition of the cyclohexanedione (89) to 2-methylcyclopent-Zen01 to yield the adducts (90,91) following ring expansion of the initial (2+2)-adduct. Adduct (90) is used as the precursor to (88).32 Photo-addition of the enone (92) to the alkene (93) gives the ring opened cycloadduct (94). This compound was used as a starting material for the synthesis of bicyclo~ndecenes.~~ Harwood et al. have reported a variant of the photochemical addition of alkenes to the enols of lY3-diketones. By using the enol ethers (95) as the alkene component reasonable yields of the 2-alkylated products (96) are obtained by the route shown in Scheme 4. Apparently there is little evidence for the formation of cyclobutane products and the usual cyclization path is diverted by the intramolecular hydrogen abstraction route shown. The reaction is prone to the influence of substituents and fails with heavily substituted enol ethem3* Several approaches to the taxane skeleton (97) have been published recently (see also reference 9). All have involved (2+2)- cycloaddition of the type reported by Berkowitz et a/. who have added cyclopentene and cyclohexene to the enone (98) to yield the cycloadducts (99). Successful addition of the alkene (100) to the same enone yields the ring-opened adduct (101). In a similar fashion the intramolecular addition of the enone (102) affords a (2+2)-adduct which can be treated with base to provide a route to the skeleton of the same natural product.35


187

R’ = Ph or H

+ + 0

OH

OH

0

(80)

(81)

“fp”

0

Cl”

0

(83) n

-

0

1,Z or 3

II

(84) R ’ = H, Me, But, Ph, COMe, CH,=CH, M e OH

RZ= H R’ = R Z = S C H ~ +cH,+, ~ ~ ,

CHZ-CH

=C H-CHZ

+ c H ~ + ~ or .

Photochemistry

188

0

AOH Q?" (89)

@" AOAc Me

0

(93)

(94)


= H or Me, R 2 = Et, Bun, R 3 = H R' = H or Me, RZ = Me, R3 I Me R'

189

(95)

Scheme 4

(97)

(98)

(99)

n

= I, R '

t

p-~-

n =z, R ' = ~ - H and a - H

0

0

190

Photochemistry

Acetone-sensitized addition of ethyne to the enone (103) gives the adduct (104) in 50% yield. This adduct was subsequently elaborated to provide a route to optically active tri~hothecenes.~’The photoaddition of the enone (105) to a-terphed (106) gives a mixture of (2+2)-cycloadducts (107) containing both the head to head and head to tcu‘l isomers. The bead to head mixture was used as the starting material for a total synthesis of (+)-Elemol (108).37 Qu’mtitative yields of the adducts (109) are obtained by low temperature, -20 to -4OoC, irradiation of the enamine carbaldehyde (110) with the alkenes (lll).38The enamide (112) also undergoes photoaddition of acrylonitrile. The adduct from this, on catalytic hydrogenation, provides a synthetic route to the carboxamides (113).39 (2+2)-Adducts (114) are formed on irradiation of the quinolone (115) with cyclopentene, cyclohexene, and 2,3-dimethylb~t-%ene.~~ Kaneko et a/. have studied the addition of diketene to the quinolinone (116) to yield the adduct (117)?l The rearrangement of the cyclobutanol (118) can be brought about by irradiation in the presence of H ~ o / I , . ~ ~ Successful dimerization of the coumarin derivatives (119) in the solid state has been reported.43 The photobasicity of several coumarin derivatives (120) has been e~a1uated.l~A series of twenty eight coumarins have been studied in the solid state. This has shown that only twelve of these, as shown in (121), actually photodimerize. X-Ray crystal data indicates that double bonds can interact in (2+2)-dimerizations even if the bonds are more than 420 pm apart.45 Calculations relating to the reactivity of the double bond in the psoralen (122) have been made?‘ Other work on furocoumarins has been reviewed by Bensasson4’ and Dall-Acqua et .d8 Photochemical addition of alcohols and acetic acid to the enone double bond of Decomptin (123) affords the adducts (124) in high yield when the irradiations are carried out in benzene solution.49 Dimethyl acetylenedicarboxylate photoadds to the pyrone (125) under sensitized conditions to yield the benzene derivative (126) presumably by decarboxylation of the (4+2)-adduct (127). Adducts of this type (128) are obtained by the sensitized addition of acrylonitrile to the same substrate. The (2+2)-adduct (129) is formed also but in low yield.50

A detailed study of the photo-ring closure of the hydroxychalcones (130) to yield the flavanones (131) has been made51 and proton transfer reactions in 3-hydroxyflavones have also been carried out.52 Miscellaneous Reactions.- The syn-trans dimer (132) is obtained on irradiation of the pyrazinone (133) in the solid state. The structure, a (4+4)-dimer, was fully identified by X-ray crystallographic analysis.53 This report corrects an earlier account of the


191

O & iy PH

Me M e

(107b)

(107~)

(107d)

(108)

(109)

(110)

R1 = e g r o R AcO

OAc

Rz = R 3 = C02Me RZ = COZMe, R3 = H or vice versa R 2 = C02But, R3 = H or vice versa RZ = R3 = H or Me

(111)

Photochemistry

192

$ 8' NH,

RZ

I

H

Ph

'Ph

(113) a; R' = CN, RZ = H b; R ' = H, RZ = CN

(112)

(114) R-R = (CH2& or R = R =Me

(CtiZl4

Me Me

OAc

&; 0

H (115)

Me

Me

(117) R

Me

a.

(119)

(116)

R

= CI or Me0

R'

Rz

R3

R4

R5

Me0

AcO

H Me0 H H

H H Me0 H

H H H H

H H H H

H

AcO

H H H

Cl

H Me CI H H Me Me H

H H H

CL

AcO H H

H H H H H H H H

~~

H H (1 20)

R5

R4

Cl

H

H H

Cl Me

H H H

H H

193


& -(

*

OAc

OMe

(122)

$O,Me MeOzC

D

-

0

OAc

(124)

i

R = H, Me, Pr or Ac

(126)

(125)

CN C0,Me

II

\

Meo2c*

QK”o-.

qA 0

OH

(131)

(130) Me

Ph

Photochemistry

194

R (&

H

(135) a; n = 1

( 1 3 4 ) a; n = 1, 8lol0 ( R = Me) b; n = 2, 76% (R = Me) c; n = 1, 67%(R = H )

b;n=2

0

cp

(1 35c)

(135d)

(137)

(140)

(138)

( 1 39)


195

dimerization of (133) by the same authors.54 Cyclopentanols (134) are formed by the photo-reductive cyclisation of the enones (135). Reactions are carried out in HMPA and irradiation of the enones (135) in this medium effects electron transfer to yield the radical anion of the carbonyl group. Cyclization follows the "Rule of Five" and yields the cycl~pentanols.~~

2

Rearrangement Reactions

a,P-Unsaturated Systems.- A reinvestigation of the photochemistry of the epoxy enone (136) has been carried out. The W I T * excitation of this compound yields several products which were reported previ~usly.~' The present work has shown that the compounds (137-139) are also formed. This result adds to the already known complexity of the reaction system." Muller has reported that the epimino derivatives of these systems are also reactive. Thus the irradiation of the derivative (140) affords the two products (141) and (142) by reactions which are similar to the reactions of the epoxy ana~ogues.~' A detailed study of the photoenolization of the ketones (143) and their reketonization has been rep~rted.~'The enone (144) undergoes deconjugation when subjected to u. v. irradiation.m White et a/. have observed that the photochemical deconjugation reaction Deconjugation, of the triene (145) yields (146) as a mixture of E and $isomers. yielding (147) as a 51:59 mixture of isomers, was reported to occur for either triene (148)6' Photo-deconjugation of the lactones (149) in the presence of (-)- ephedrine rapidly yields the deconjugated lactones (150) with a slight enantiomeric excess. To some extent the reactions were both solvent and temperature dependent62 George et al. have reported a study of electron transfer reactions of the furanones (151)."3 The triplet state of the ecdpone (152) is reactive and affords the products shown in Scheme 5. The formation of the reduction products (153) and (154) is presumed to follow a path where loss of a hydroxyl radical yields the ally1 radical (155) which then gives the products (153) and (154) by hydrogen abstraction. The ketone (156) is formed by a 1,2-bond migration and the cyclobutanol (157) arises by secondary irradiation of the diketone (156).0Q The enone (158) shows solvent dependent photochemistry. Thus in ethyl acetate the deconjugated product (159) is formed while in methanol the reduced ketone (160) is pr0d~ced.g~ Irradiation of the thiolactone (161) in alcohols produces the esters (162). The ester (162, R = Me) is itself photochemically reactive and on prolonged irradiation in methanol is converted into the acetal (163).% The enones (164) all undergo photoisomerisation into the lactones (165). The mechanism suggested for this isomerization involves the intermediacy of the cyclopropyl ketone (e.g. 166). However

196

Photochemistry R4

R2 R* (1 4 3 )

R'

RZ

R3

R4

Me H H H Me H

Me Et ally1

H H H H

Me Me

R ' Me Me Ph Me

Me H Me Ph

&

C02Me

Me

i)SiMe3

(145)

(144)

%

COzMe RZ OAc

OSiMe, (147)

(146)

OAc (148) a; R' b; R '

= C02Me, R2 = H = H, R2 = COLMe

(149)

Ph

n n n n

= 2, R ' = R 2 = H =l, R'=R2=H = 1, R' = Me, RZ = H = 1, R ' = R 2 = Me

0

197


OH

OH

'

O --H -

hv

0 R

{flj

+

0

OH (157)

(156)

(1 55)

Scheme 5

& M3 0

0

/

(159)

(1581 R ' = H, R Z = Me, R 3 = d-H, P-OH R' o H, R2 = Et, R 3 = cl-CfCH, P-OH

R'

P

R2

=

Me, R 3

= a-H, P-OH

&

0

H

(160)

OMe

JYcozR (161)

(162)

R = Me, C,H5, Pr', But

(163)

Photochemistry

198

(164)

(166)

R3 R'

R 3 = Ph, R' = Me or Ph, R 2 = Me or Et

(169)

0 Ph

Ph

COOPh

Ph

Me

Ph

ii

Me (172)

(171)

ph%

(173)

R'

(174)

(170)


199

no direct evidence for this was obtained. The irradiation of enone (164e) did show divergence from the general path and gave the enone (167) as the principal photoproduct. This is proposed as reasonable evidence for the intermediacy of (168) which in this instance undergoes decarbonylation rather than cy~1ization.b~ The allenic esters (169) yield the the cyclobuteneones (170) on irradiation. In these is the major product and is accompanied by examples , this 1,1,4,4-ktraphenylbuta-1,3-diene. The cyclobutenones are photochemically unstable and can be completely destroyed by irradiation for 4-6 h. When the phenyl ester (171) was irradiated no cyclization occurred and the only compound obtained was the photo-Fries product (172). One interpretation of the cyclization process is that the ester undergoes Cyclization and fission of the carbonyl-ester 0 bond yielding a radical pair. recombination would afford the product. However, attempts to trap intermediates such as (173) were unsuccessful.08

transcis Isomerisation of the oxime (174) can be brought about photochemi~ally.6~ Irradiation of a mixture of E,Zisomers (175) induces cyclization and loss of methanol to yield the fused quinoline derivatives (176).70 The cinnamates (177) are photochemically reactive in micelles. Irradiation brings about G O bond fission and recombination within the radical pair affords the chalcones (178).71 The E Z isomerization of the enone (179) is followed by the photochemical isomerization into the cyclopentenone derivative (180). This occurs by amide bond fission followed by recombination within the biradi~al.~'

P,y-Unsaturated Systems.- The direct irradiation of the cyclohexenone (181) affords the three products shown in Scheme 6. The quantum yield for the direct irradiation are shown below each product. The influence of triplet sensitizers and quenchers on the reaction was studied and a triplet state was shown to be involved. A detailed interpretation of the mechanism of the reaction was g i ~ e n . ' ~The enone (182a) undergoes triplet excited state rearrangement into the two products (183) and (184). It is of considerable interest that the bicyclehexanone (183) is formed to the exclusion of the cisisomer. The reaction is remarkably efficient and the quantum yields are shown below the appropriate structures. Again a detailed analysis of the mechanism is reported. Interestingly the P-naphthyl enone (185b) is also photoreactive and yields the products shown in Scheme 7. In this instance both the trans and the cisbicyclic isomers were formed.74 Details of the photochemical behaviour of the p,y- unsaturated enones (186) has been reported. This supplements the report made earlier in note form.75 The reaction described involves the photoconversion of the enones (186) into the imines (187) and (188) by a path which is thought to involve a 1,Sbenzoyl migration. The terminus for this is a pendant phenyl group. Such a process has not previously been described. An

Photochemistry

200

R’ = R Z = (CH=CHIZ R’ = H, RZ = But

(176)

R4

R4

OH

(177)

0 (180)

( 1 79)

+

oih--Ar + t? - -Ar

At

Ar

Ar A T

0

Scheme 6

= 0.024

0

H

= 0.020

201

IIIJ2 Enone Cycloadditions and Rearrangements

4 Ar

H- J%+o

Ar

a; Ar = a-naphthyl b;Ar = 0-naphthyt

(182)

(&

Ar I I

(183) d

Ar

5

0.46

(184) 0

Ar 0

Ar

0.54

Ar

= 0.38

0 = 0.02

Scheme 7

(186) A t

=

C,H,

or p-ClC6H,

( 1 88)

(187)

Art L

p

h

A r ’ A k P Ph h Me

ArCO

H

OCOAr (189 1

( 1 SO)

(192 A )

(191) a; R’ = Me, R 2 L: H b; R’ = H , R Z = Me

(192 8 )

Photochemistry

202

1193) a; R'

COMe, COPh, R 2 = H

(194) a; R = COMe

b; R' = H, R Z = COMe, COPh

& R3

b; R

= COPh

a; R' = R Z = R 3 = H

b; R' = Me or OMe, R 2 = R3 = H R' = OMe, R Z = M e or H, R 3 = H or Me d; R ' = OMe, R Z = R 3 = Me c;

R2

( 1 96)

O

a

HM

(195)

e

CH=C=O

R'

(197)

m %

0

0

a

02"

(261)

( 202 1

(203)

P > O (204)

(205)

(206)


203

electron transfer mechanism is thought to be ~ p e r a t i v e . ~A~ full account of the photochemical conversion of the azadiene esters (189) into the dihydrwxazole derivatives (190) has also been reported. The reaction is interpreted in terms of a l,%benzoyl migration in the enol ester followed by cyclization within the resultant biradical. The rearrangement is proposed as the first example of a 1,2-acyl migratioxi in an enol ester.77 This paper expanda the material originally published in note The photodecarbonylation of the dienones (191a) and (191b) has been examined and shown to be a concerted process. The cisisomer (191a) yields initially the triene (192A) while the trwisorner (191b) affords the triene (192B). These experiments prove conclusively that the decarbonylation is a concerted process?' 1,SAcyl migrations occur on the irradiation of the lactones (193, R1 = COMe). This treatment yields (193b, R' = COMe) which is also photoreactive and is transformed into the valence bond isomers (194). Irradiation of the lactone (193a, R' = COPh) under acetone-sensitized conditions also brings about the 1,Smigration yielding (193b) which is not isolated since it undergoes oxetan formation yielding (195).8* A full account of the photochemical reactivity of the enones (196) and their photoconversion into (197) by a 1,bacyl migration has been reported!' This supplements the material already published in note form.82 In contrast acetone-sensitized irradiation of (196b, R1 = Me) brings about an oxa-di-n-methane reaction affording the tricyclic product (198). With a methoxy substituent at the bridgehead only the 1,3-acyl migration is observed. The derivative (196b, R' = MeO), on both direct and acetone sensitized irradiation, affords a mixture of the isomeric ketones (199). The carene skeleton can be synthesized using the ready rearrangement of bicyclic systems of the type illustrated in structure (200). Irradiation of these molecules has been shown to proceed by Norrish type I bond fission with rebonding within the resultant biradical to yield ketenes (201). This route has been applied by Uyehara et d as part of a total synthesis of sesqicarene and sirenin and involves the specific rearrangement described above with trapping of the ketene as the acid (202). Subsequent chemical transformation of the acid provides a route to the natural products.83 Mehta and Subrahmanyam have reported the oxa-di-n-methane photoconvenion of the enone (203) into (204) as a route to (3,3,3)- propellanes and specifically to racemic modhephene (205).84 Uyehara et a/. have described the photochemical conversion of the enone (206) into (207) by a 1,bacyl migration. The compound (207) was used as the starting material for a synthesis of racemic @i/ocauiin (208)8 5 Adam and his coworkers have studied the oxa-di-n-methane rearrangement of the norbornenone (209). They approached the problem by the synthesis of precursors of the putative biradicals such as (210).86 The oxa-di-n-methane rearrangement of the P,y-unsaturated enones (211, 212) has been reported by Schultz and his coworkers.

2 04

Photochemistry

Acetone- or acetophenone-sensitized irradiation of the enones yields the rearranged ketones (213, 214) which are described as useful substrates for the synthesis of polyquinane natural products.87 The enones (215) can be converted by photosensitized irradiation into the diquinanediones (216). Irradiation of (215) in acetone gives a low yield of the tricyclic ketone (217). This ketone, while stable in the dark, is photochemically converted into the diquinanedione (215). The authors present evidence that this conversion results from fission of the cyclopropyl bond to yield the biradical (218).88 Demuth and Hinsken have reported the use of the oxa-di-.rr-methane rearrangement in the synthesis of annelated triquinanes. Thus the photo conversion of the enone (219) affords the tetracyclic ketone (220,72%). In an analogous reaction the enone (221) is converted into the isomeric ketone (222,7O%)ag

3 Photoreactions of Thymines and Related Compounds A review has outlined some chemical aspects of the photo-induced cross-linking of proteins to nucleic acidsg0 The irradiation of the bromouracil (223) in the presence of the electron rich aromatic compound (224) affords the &substituted uracil (225) exclusively. With other aromatic compounds both the 5- and the 6- substituted uracil derivatives (226) and (227) were obtained. The formation of the 5-substituted uracil was not unexpected but the &isomer had not previously been reported from such reactions. The mechanism by which this latter type of product is formed is not knownqgl A study on the photochemical isomerization of 4-pyrimidones (228) has provided a synthetic approach to the Dewar pyrimidones (229). These are prone to hydration and under the conditions of the irradiation are converted into the hydrates (230, 231). An examination of the behaviour of the hydrates has shown that they readily undergo reversal to starting materialg2 Photoisomerization to (232) and dimerisation yielding (233) of the pyridones (234) occurs on irradiation in ethyl acetate solution.93 A study of the photochemical behaviour of the uracil derivative (235) has been carried out. Details regarding the triplet energy of the Eisomer and the singlet-triplet crossing efficiency have been The fluorescence of l,3-dimethyluracil is quenched by water. The yield of photohydrates of pyrimidines in general is sensitive to the water c~ncentration?~A spectroscopic study of the triplet behaviour of the thiouracils (236) has been reported.% Irradiation of 5-ethylorotic acid (237) leads to the formation of the ethylidene analogue (238) and the dimer (239). The continued irradiation of the analogue (238) yielded 5-ethyluracilg7 The adducts (240) can be prepared by the irradiation of thymidine in the presence of 8-methoxypsoralen?8 The photocycloaddition of the thymidine derivative (241) results in the formation of six cyclobutane isomers.99

11112 Enone Cjlcloadditions and Rearrangements

205

Mpo (207)

b

0

(209)

(208)

9 @O : zMe

MeOzCH

(211) R = H or Br, n = 1 RrH, n r 2 R = H , n = 3

’\

--C02Me a

\’H

0

(212)

R@:~e (213) R = H or Br, n = 1

R=H, n=Z R = H, n = 3

“2cp&* C0,Me

OMe

(215) R = CHzCHzOMe or CH,CH(OMe),

(214)

OMe

(217)

&0 =O

(216)

Photochemistry

206 OR

8

OR

&

&

0

0

0

(219)

( 2 2 1 ) R = CH,OCH,CH,OMe

(220)

o&joR

O / \ O M eO M

Me

MeN

OMc

Me

Me (225)

0

MeN

( 2 2 6 ) R = Me, OMe or 1,4-di-Me

207


.'ao R1

Et

dN$

A

0

RZ

OH

(240)

(239)

Me$Ko I

"

O 0I-i Y (242)

Photochemistry

208 The irradiation, using 350 nm light, of a dry film of

dimethoxycoumarin (242) and adenosine (243) affords the adduct (244). No evidence for the formation of cyclobutane products was obtained.lm A study of several psoralena has shown that only compound (245) undergoes intercalation with DNA. Photoinduction of interstrand crosslinks in calf thymus DNA was also efficient."'

4 Photochemistry of Dienones Linearly-conjugated Dienonee.- The only observed reaction of the dienones (246) from either the triplet or the singlet state was transcis isomerization around the C-7,C-8 bond The isomeric compound (247) also undergoes this isomerization as well as transcis isomerism of the C-9,C-10 bond. The diene (248) is also photo-reactive giving the product (249) by a 1,Shydrogen transfer. Irradiation of (249) yields (250) by a Norrish type I1 process.lo2

A detailed study of the photochemical reactivity axid synthetic usefulness of the o-quinolacetates (251) has been reported.lo3 Quinkert and his coworkers have lodged a patent dealing with the formation of macrolides from the photochemical ring opening of the cyclohexadienones (252).lo* The steroidal dienone (253) has been studied by laser flash excitation. The triplet state energy of this system is 42-43 k.cal. mol.-' and is slightly lower than expected from the estimates made from the spectroscopic triplet. The lower energy is thought to be due to molecular re1axati0n.l~~ Croes-conjugated Dienones.- The isomers (254) and (255) are obtained from the direct irradiation of the cyclohexadienone (256) in benzene. Prolonged irradiation of the mixture results in the photoisomerization of (254) into (255). The irradiation of (255), however, does not bring about isomerization. The study of enantiomerically pure (256) was also carried out and from this it was found that the starting material isomerized into a mixture of enantiomers.lW The photochemical rearrangement of the cyclohexadienone (257) in methanol occurs in a stereospecific fashion and yields the adduct (258) whose structure was proven by X-ray crystallographic analysis.107 Cyclohexadienone (259) is photochemically reactive and can be converted in two steps This process represents the into the adduct (260) as shown in Scheme 8. intramolecular trapping of the zwitterionic intermediate (261).'08 The photochemical reactions of a series of proaporphines have been studied. Thus the irradiation of orientahnone (262a) in sunlight affords the two isomeric products isobo/dine (263a) as the major and isothebaine (262a) as the minor. Roemeridinone (262b) is also photoreactive and is converted into methyl isothebaine (26413) as the major product and N-methyl/aurotetanine (263a) as the minor.

The stereochemical

209


HO OH

(244)

Coke

(246)

(247)

(248)

(249)

--OAc

RZ R+

(250)

R3

(251)

R4 (252) R = H or C1 to C4 alkyl n = 2-16

210

Me0

Me0

COzMe

o,, cot Me

H

H

Photochemistry

Me0

Me

Me’

0

M eQCC13 (257)

(258)

p.

(259)

(260)

(261) Scheme 8

J$ C0,Me


MROe

o

F

N

l

Me0 OMe

Me0

\

Me

/

0

( 2 6 4 ) a; minor b, major

b; minor

J&-& \

OH

OMe NMez

*- H

HO

.H

OH ( 2 6 3 ) a; major

( 2 6 2 ) a; R = H m

IIvMe

e 'l;@lMe

b, R

211

Me0

* -

OH

(270)

(269)

OMe

OMe

212

Photochemistry

implications of the rearrangements were discussed in some detail.'@' Photochemical rearrangement of the cyclohexadienone (265) yields the lumiproduct (266).110 The cyclohexadienone derivative (267) undergoes photochemical isomerization into the four products (268-271). The latter three of these result from ring contraction of the cyclohexadienone moiety.'"

A new approach to bklactams has been described and involves the photochemical cyclization of the pyrimidinium enolates (272). Typically irradiation of (272) in acetonitrile affords a high yield (96%) of the bicyclic lactam (273).'12 Photo-cistmmisomerization of the dienones (274) affords the transisomers (275) which can be trapped by dienes such as cyclopentadiene and isoprene yielding e.g. (276).l13 Kazama et a/. have studied the influence of conformation on the photocyclization and photoreduc t ion react ions of lo-(SH-xanthenylidene)-g ( 10H)-anthracenone. l4

'

5 1,2-) 1)3-, and 1,CDiketones 1,Z-Diketon=.- Rubin has reviewed the recent photochemistry of l,Z-diket~nes."~ Studies of the gas phase photo-decomposition of glyoxylic acid"' and of pyruvic acid have been carried out."' Hamer has reported a synthesis of cyclopentane-l,3-diones (277) using silver ion catalysed ring expansion of the cyclobutanones (278) formed on irradiation of the 172-diones (279).'18 Birney and Berson have described the photochemical double decarbonylation of the triketone (280). At room temperature in CD,CI, tri-decarbonylation gives benzene but at low temperature in a matrix the norbornadienone (281) is formed.'" 1,S-Diketones.- Intramolecular electron transfer has been used to explain the photo-degradation of gi!yy/&cine (282).120 The dione (283) undergoes Norrish Type I1 hydrogen abstraction to afford the biradical (284) as the reactive intermediate. In the presence of oxygen this biradical is trapped and the furanone (285) is the product formed.121 A detailed study of the photochemical behaviour of the ketoesters (286) has revealed that they undergo Norrish type I1 hydrogen abstraction, The products from this reaction are shown in Scheme 9. Interestingly the authors suggest that back hydrogen transfer is suppressed because of intramolecular H-bonding within the 174-biradical formed in the Norrish type I1 step. The H-bonding controls the stereochemistry of the cyclization to the cyclobutanols.122

Unstable p-lactams (287), benzoylation affords stable products, are formed by the photochemical cyclization of thioamides (288). The authors believe that a Norrish type

IIIt2 Enone Cycloadditions and Rearrangements

213

I

R2

( 2 7 2 ) a; R’ = R3

=

(273) a; 96.10 b; 91’10 C; 83’10 d; 61% e; 92’10

Ph, R Z = H

b; R’ = Ph, R 2 = Me, R 3 = H c; R’ = Ph, R 2 = R3 = M e d; R’ = R 3 = Ph, R Z = Me

e; R’ = Me,

( 2 7 4 ) R’

I

RZ = H

R’ R’

= =

OMe, R 2 = t i H, R Z = M e

RZ = SEt, R3 = Ph

(276) a; R 3 = H

(275)

b;

RA h0 R

e

B

(277)

=CH2

0 (279)

(278)

a; R = Mel, R’ = H b; R = Ph, R’ = H

&2l

0

3

R*

r

R’

R’

R 3 -R

1

R-R = +CH,+, d; R = R’ = Me C;

H H 3 2 y N +

0

co

-

Photochemistry

214

+ R Scheme 9 R2

R3

0 dN ''

Ph

(287)

t Ph, R 2 = R 3 = M e 2 9 '1. 16 % = Me, R2 = R3= Me 35% c ; R' = Me, R 2 = H , R3= Ph d; R' = Me R 2 = H, R 3 = OMe 76% 1 2 e; R = Ph ,R = H , R 3 = OMe 90%

a; R'

(287)

(288)

(288)

b; R'


215

I1 process is involved and that a zwitterion is produced following the hydrogen transfer step.123 1,4-Diketones.- A detailed study, by product analysis and by laser flash photolysis, of the photochemical reactivity of the barrelenes (289) has been reported.la4

An n.m.r. study of phenyl fulgides has been p ~ b 1 i s h e d . l ~Heller ~ and his coworkers have continued their study of photochromic systems. In the present report the photochromism of succinic anhydride derivatives ( e.g. 290) has been Carbonyl compound-sensitized dimerization of maleic anhydride affords the dimer (291) in good ~ie1d.l~' The two dimers (292) and (293), obtained from the photodimerization of the anhydride (294), have been used as a starting material for the synthesis of some propellanes.'28 Wirz and his coworkers have developed a method for the study of the dienone (295)/ phenol equilibrium. The dienone (295) is obtained by irradiation of dione (296) which undergoes photochemical elimination of ketene. Ketene formation can be confirmed at low temperature but under these conditions very little of the dienone (295) is observed since it readily undergoes photochemical ring opening to ketene (297).12' P-Lactams (298) can be formed in low yield by the photochemical ring contraction of the diones (299). This involves N-0 bond fission followed by loss of CO, and rebonding in the resultant 1,4-biradi~al.'~' Scheffer has made use of the intramolecular hydrogen abstraction reactions in the diketones (300) to synthesize the cage compound (301). This compound was shown to have no anti viral activity.13' The cage compound (302) is formed easily on irradiation the dione adduct (303). The synthesis of the cage (302) confirms the endoarrangement in the a d d ~ c t . ' ~ ~

of

The photochemical isomerization of the muconic acid anhydride (304) to the bicyclic compound (305) has been reported to occur in high yield.'33 Phthalimides and Related Compounds.- The piperazinetetrones (306) are photochemically reactive. Irradiation of the derivative (306a) affords the cyclized product (307a) by a path involving Norrish type I1 hydrogen abstraction, 1,4-hydrogen migration within the biradical, and bond formation. The same path is followed for the derivatives (306 b, c) yielding the cyclized products (307 b, c). In these examples a 1,Shydrogen migration path also competes and yields the products (308).134

Photochemical reactions of phthalimides and related systems continues to produce new and interesting results. N-Ethylsuccinimide is converted into the azepinedione (309) in 64% yield on irradiation with a low pressure Hg lamp.135 N-Methylglutarimide adds photochemically to Zmethylpropene to yield the oxetan (310).136

Photochemistry

216

d'

'0 (292)

(293)

(294)

0

6

( 2 95)

0

(2981 R = Ph or PhCHMe (299)

(300)

(301)

0

(302)

(303)

0

217


I R'

(307)

(3 08)

NO@

Me

0 0 (311)

(310)

(309)

RO

Me

2&NMe '

Me

0 (312) R ' = R Z = H

(313)

2

R'= M e , R = H R ' = H , R 2 = Me

R'e( 0

F?

0

218

Photochemistry

A detailed account of the photobehaviour of the phthalimide (311) with alkenes has supplemented earlier reports. The reactions encountered are either a 27r+21~addition yielding benzazepinediones or electron transfer from the alkene to the phthalimide followed by intermolecular t r a ~ p i n g . l ~ ~ - l ~In' another study N-methylphthalimide derivatives (312) undergo electron transfer reactions on irradiation in alcoholic solution. Reaction between the radical anion and radical cation yields adducts e.g. (313) a8 well as the more conventional products of addition to the carbonyl group. The identity of these new structures was verified by X-ray c r y ~ t a l l o g r a p h y . ~ ~ ~ Coyle and his coworkers have reported an approach to the alkaloids of the protoberberine type by the photochemical cyclization of the Mannich bases (314). This cyclization step yields the products (315) in moderate to good yields.14' The phthalimides (316) and (317) also undergo photochemical cyclization to afford products of the type represented by (318) and (319) respectively.142 Intramolecular photocyclization of the phthalimide derivatives (320) yields the ring expanded compounds (321) as the predominant products. Alternative modes of reaction are also encountered such as hydrogen abstraction and cyclization followed by Norrish type I1 chain elimination as shown in Scheme 10. Phthalimide (320d) also shows a solvent dependency when the isomers (322) are formed on irradiation in methanol (or ethanol).lU In another example Maruyama et a/. have reported the cyclization of the phthalimide derivative (323) to give a high yield of the benzazepinedione (324).'44 As can be seen from the foregoing, phthalimide photocyclizations have provided useful synthetic routes to a variety of heterocyclic products. Machida et al. have used the reaction to yield the spiro compounds (325) from the irradiation (in methanol) of the phthalimide derivatives (326). The products are presumed to be formed via bond formation in the biradical produced by the addition of methanol to the radical cationlradical anion pair.145 The indoles (327) undergo photochemical (2+2)-addition with N-methyl phthalimide to afford the oxetan adducts (328).'4G This work has also been the subject of a patent app1i~ation.l~' The photochemical reaction of N-methylphthalimide with 1,l-diphenyl ethene affords the phthalimide adduct (329) and the ether (330) in 44 and 12 % yield respectively. With imide (331) the byproducts are the ring opened adduct (332) and the ether (330) in yields of 31 and 44% yield respectively. The authors suggest that the formation of the ether is the result of a second electron transfer as illustrated in Scheme ll.'48 Photochemical addition of N-methylthiophthalimide to diphenylketene and the corresponding tolylketenimine affords the (2+2)-adducts (333) and (334) respectively. The ketene adduct (333) is itself photochemically reactive and undergoes loss of COS to yield (335).14' The thiophthalimide (336) undergoes hydrogen abstraction and cyclization affording (337) on irradiation using visible light.15* Norrish type I1

219


@:

(C HtIn S R

0

0

(316) R = Me, Et,PhCH,, But , e t c . n =1-4

q, HO

(317) R = Me or E t

m - 1 or2

0

S

R (31 8)

(319)

(320)

CJy (3211

HO

(320b)

hv

*" 0

0

0

Scheme 10

NH

Photochemistry

220

(322) R =

p-

0 CHzOMe or ol- CHzOMe

0

(323)

(3 2 4)

m = 2 , n - 1 m = n = 2

m t 3 , n - l

= 3,n = 2

m

(326)

(325)

d

R

R'=

2

R'

=

R'

A c , R2 =

R3= Me, H

Ac , R2=

R3= (CH213,

0

(CH2)&, (CH,),

(328)

(327)

e

O

M

e Ph

0 (329)

Ph

(330)

22 1


NH Me

(33 2 1

1331)

ph)+&

Ph

MeOH H+

phh

~

Ph

OMe

electron transfer

-

(330)

Ph

Scheme 11

Ph Ph

X

(333)

x=

0

(335)

(334) X = N-tolyl

(33 7)

(336)

Ph

( 3 3 8 ) n - 3 or 4 Scheme 12

Photochemistry

222

cyclization has been reported to occur on irradiation of the cyclic thioimides (338). Both 13- or E- hydrogen abstraction can arise and yield the products shown in Scheme 12. The cyclization within the Norrish type I1 biradical is followed by elimination of hydrogen sulphide. Interestingly cyclization also occurs with the thioimides (339) but excitation and hydrogen abstraction arises only at the thio carbonyl group.15' The xanthate (340) undergoes decarbonylation to afford the alkyl xanthate (341) when irradiated in benzene s01ution.l~~ Phot-addition of alkenes to N-methylnaphthalene dicarboxamides in benzene has been studied. The structure of the arene moiety in the imide was important in determining the reaction path. Mainly cyclobutane and oxetan formation occurred.lM The dicarboximide (342) undergoes photochemical cyclization with incorporation of methanol to yield the two products (343) and (344) in 55 and 16% respectively. This type of cyclization appears to be quite general for such systems and is also reported for the h i d e s (345) and (346).15* A variety of products resulting from aminolysis, reduction, and radical coupling is produced on irradiation of the phthalimide (347) in diethy lamine.155 The benzophthalimide (348) undergoes photochemical reaction with alkenes e.g. In some cisbut-2-ene to afford the isomeric addition products (349) and (350). instances, with 2,3-dimethylbut-2-ene and stilbene, the addition reaction afforded the oxetans (351, 352) or oxetan fragmentation products with no evidence for the formation of the ring expansion products encountered with the other alkenes. The oxetan products were also accompanied by products formed by hydrogen abstraction and radical combination. An electron transfer path is thought to be involved in these latter cases.15' A detailed study of the photochemical reactivity of the N-methyl carboxamide (353) with alkenes and dienes has been carried out. Typical reactions for the two addends are shown in the Schemes 13 and 14 respectively. A tentative mechanistic rationalization of the process has suggested the involvement of two exciplexes generated from the singlet state of the carboxamide and the unsaturated compounds The nature of the product is to some extent dependent on the substitution on the unsaturated moiety. Thus stilbene (both cis and trans) in addition to yielding the (2+2)-cyclobutane product also affords products (354) from the fragmentation of an oxetan product (355).I5'

6 Quinones The photochemical reaction of phosphorous derivatives with p -benzoquinones has been studied.15' The Argon matrix isolation of cyclopentadienone has been achieved using a variety of photo -precursors such as o - and p - b e z o q u i n ~ n e s . l ~ ~ pBenzoquinone and 1,Cnaphthoquinone add to cycloheptatriene to afford spirocyclic


223

0

( 3 4 0 ) R = E t , P r , C H M e , , B u , Me,CHCH,

&-ph

&--OM. \

(341)

/

0

0

Ph

0 ( 3 4 41

(3 4 5 )

Photochemistry

224

0 (352)

(353)

(353)

Scheme 13

+ 1

Scheme 14

225

IIIl2 Enone Cycloadditions and Rearrangements

( 3 5 4 ) a; R'=

H , R'=

Ph

'0 (355)

OEt

0

Me

-Q^ OH

Me

(357)

(356)

"'WA HO

Me

0 OH

(359)

0

0

(360)

(3611

0

@? \

R2

R'

OH (362)

(363)

R'= R 2 t H R'=

M e , R2= H

R 1 = R2= Me

OH (364)

Me

226

Photochemistry

*x

Br

0 (365)

(366)

Qod 0 0(367)

(368)

@:x /

WoM OCOR 0

NwAr

Ph Ph

0 (3 69)

(370)

WoMe 0

0 (371)

OCOR

OPh 0

(372)


227

ethers.leO The irradiation of the quinone (356) in alcohols has been studied. The authors suggest that the products formed are the result of protonation and cyclization of the excited state molecule to afford (357). Trapping by solvent yields (358) and (359) while ring expansion gives the isomeric chromones (360) and (361).16' The quinone derivatives (362) are also photochemically reactive and yield the cyclized products (363) on irradiation under nitrogen. The formation of this product arises by a Norrish type I1 hydrogen abstraction reaction affording the biradical (364) which cyclizes to the observed product.16' Maruyama et a/. have reported the use of irradiation in the conversion of the quinone (365) into the adduct (366).'63 An e.s.r. study of the photochemical reactivity of the quinone (367) has shown that the radical (368) is formed.'64 Photoaddition of triarylketenimines to phenanthraquinone affords adducts of the type illustrated in (369).165 The results of a study of structural factors on the photochemical reactions of amino anthraquinone derivatives have been published.lM Migration of the acetyl group arises on the irradiation of the anthraquinone analogues (370) yielding (371).16' The photochromic behaviour of the quinone analogue (372) has been studied.'08

228

Photochemistry

References

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108, 800. 5. M. Tanaka, K. Tomioka, and K. Koga, Tetrahedron Lett., 1985, 26, 3035.

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McArdle, J. Chem. Sm., Chem. Commun., 1985, 1698. 9. T. Kojima, Y. Inouye, and H. Kakisawa, Chem. Lett., 1985, 323. 10. A. B. Gray, L. M. Harwood, S. A. Leeming, and K. Prout, J.

Chem. Research @), 1986, 138. 11. K. S. Feldman, J. H. Come, A. J. Freyer, B. J. Kosmider, and C. M. Smith, J. Am. Chem. Soc.,1986, 108, 1327. 12. Y. M. Chae, S. K. Yoon, and S. C. Shim, Bu/l. Korean Chem. Sm., 1985, 6, 95 (Chern. Abs.fr., 1986, 104, 33667). 13. M. Hasegawa, M. Nohara, K. Saigo, and H. Harashina, Jpn. Kokai Tokkyo Kokai JP 60,248,644( Chem. Abstr., 1986, 104, 168172). 14. N. Kato and H. Takeshita, Bull. Chem. SOC.J p . , 1985, 58, 1574. 15. H. Takeshita, T. Hatsui, and T. Masuda, Kyushu Daigaku S o p

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ZIIl2 Enone Cycloadditions and Rearrangements

229

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Photochemistry

230 38.

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23 1

232 76. D. Armeeto, M. G. Gallego, W. M. Horspool, and R. Perez-Oaaorio, J. Chem. Soc.,Perkin Trans. 4 1986, 799. 70. D. Armesto, M. G. Gallego, W. M. Horspool, and R. Perez-Ossorio, Tetrahedron Lett., 1983, 24, 1089. 77. D, Armesto, M. J. Ortiz, R. Perez-Ossorio, and W. M. Honspool, J. Chem. Soc.,Perkin Trans. I; 1986, 623. 78. D. Armesto, M. J. Ortiz, R. Perez-Ossorio, and W. M. Horspool, Tetrahehn Lett., 1983, 24, 1197. 79. D. I. Schuster, L. Wang, and J. M. van der Veen, J. Am. Chem. Soc.,1985, 107, 7045. 80. N. Hoahi and H. Uda, J. Chem. Res. @), 1985, 70. 81, T. Uyehara, Y. Kabasawa, T. Furuta, and T. Kato, Bull. Chem. Soc. Jp., 1986, 59, 539. 82. T. Uyehara, Y. Kabasawa, T. Kato, and T. Furuta, Tetrahedmn Lett., 1985, 26, 2343. 83. T. Uyehara, J. Yamada, K. Ogata, and T. Kato, Bull. Chem. Soc. Jp., 1985, 58, 211. 84. G . Mehta and D. Subrahmanyam, J. Chem. Soc.,Chem. Commun., 1986, 768. 85. T. Uyehara, T. Furuta, Y. Kabasawa, J. Yamada, and T. Kato, J. Chem. Soc.,Chem. Conmun., 1986, 539. 86. W. Adam, 0. De Lucchi, K. Hill, E.-M. Peters, K. Peters, and H. G. von Schnering, Chem. Ber., 1985, 118, 3070. 87. A. G. Schultz, F. P. Lavieri, and T. E. Snead, J. Org. Chem., 1986, 50, 3086. 88. M. Demuth, B. Wietfeld, B. Pandey, and K. Schaffner, Angew. Chem., h t . Ed. End., 1985, 24, 763. 89. M. Demuth and W. Hinsken, Angew. Chem. ht. Ed. Engi., 1985, 24, 973. 90. I. Saito and T. Matsuura, Acc. Chem. Res., 1985, 18, 134. 91. K. Seki, Y. Bando, and K. Ohkura, Chem. Lett., 1986, 195. 92. T. Takahashi, S. Hirokami, M. Nagata, and T. Yamazaki, Tetrahedmn ‘Lett., 1985, 26, 3247. , 93. A. Matsushima and K. Terada, J. Chern. Si.,Perkin Trans. I. 1985, 1445. 94. S. C. Shim, E. J. Shin, and K. H. Chae, Bull. Korean Chem. Soc.,1985, 6, 234 (Chem. Abstr., 1986,104,108845). 95. A. Garner and G. Scholes, NATO AS1 Ser. A, 1985, 85, 49 (Chem. Ahtr., 1985, 103, 21437).

Photochemistry


233

96. S. J. Milder and D. S. Kliger, J. Am. Chem. Soc.,1985, 107, 7365. 97. E. Kulikowska, Z. Zawadzki, and

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M.

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Photochemistry

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T.

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23 5

236

Photochemistry

155. Y. Kubo,

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3 Photochemistry of Alkenes, Alkynes and Related Compounds BY W. M. HORSPOOL 1 Reactions of Alkenes Group Migration Reactions.- Direct irradiation of cyclooctene (la) in pentane brings about cis -trans isomerization as well as the formation of the bicyclic products (28) and (3). These are formed via the carbene intermediates (4) and ( 5 ) . The latter carbene (5) also affords methylenecycloheptene. cis -trans -Isomerization also arises with the cycloalkenes (lb) and (lc). Product (2b) is formed from cyclodecene (lb) and cyclododecene (lc) yields (6) both by carbene paths.' A group migration is also reported by Hannaby and Warren. The 1,3-PhS migration results on the irradiation of the alkene (7) affording the isomer (8).2 The alkenes (9) undergo photoreaction from the singlet state. The key intermediates are thought to be the biradicals (10) and (11) arrived at via the intermediacy of electron transfer processes. The biradicals (10) and (11) are formed by 1,6 and 1,7-hydrogen transfer steps. The products obtained by the resultant cyclization are shown in Scheme l.3 Brook et al. have reported that the irradiation of the silene (12) brings about a complex rearrangement to yield the isomeric silene (13). Although the details of the mechanistic steps are not yet known the authors propose that silene to silylene steps are i m p ~ r t a n t . ~ cis -trans -Isomerieation.- Geometric isomerization, 1,bhydrogen shift, and structural isomerization results on the 184.9 nm irradiation of acyclic alkenes in the gas phase.5 The gas phase irradiation (at 184.9 nm) of cis -pent-Z-ene produces the trans -isomer. Some isomerization affording 2-methyl- but-l-ene and pent-l-ene also occurs6 A study of the cis -trans -isomerization of but-2-ene in the gas phase has shown that the photostationary state composition is independent of the pressure of butene? Irradiation (at 185 nm) of the alkenes (14-16) brings about isomerization of the double bond.8

A detailed study of the photochemical formation of the cyclobutene (17) by irradiation of 1,l'-bicyclohexenyl has been carried out. The photoreaction also affords 1,2- and 1,4- addition products involving the incorporation of methanol. Steady state and transient methods have shown that the intermediate involved in the formation of these products is a highly strained ground state cis - trans -compound (18). This compound is the only precursor to the cyclobutene (17) following triplet sensitization of 237

Photochemistry

238

( 1 ) a; n = 1 b;n =3

H ( 2 ) a; n = 1 b; n = 2

c; n = 5

c;n= 5

0 (3)

H (61

(7)

&;

L N P Pv h

Ph

L P h

%

I

(10)

Ph R1 = Me, R2 = Ph

R1 =Ph, R2 =Me

Ph \-Ph

( 9 ) a; n = 1 b;n=2 Ph

Ph

(11)

Scheme 1

e3S

i,si 4c10H15

/

Me Si-Bu'

Me

OSiMe3

But

(12)

(13)

IIIf3: Photochemistry of Alkenes, Alkynes and Related Compounds

239

the bicyclohexenylg The trans -crown ethers (19) have been prepared by the irradiation of the corresponding cis -isomers (20). Resolution of the racemates was also carried out." cis -trans -Isomerization of isosafrole (21), by direct and sensitized irradiation, has been studied and the photo stationary photo state composition determined. Under these conditions the concentration of the cis - isomer is increased. Under electron transfer conditions the situation is reversed and the trans -isomer becomes predominant." trans -c,k Photeisomerization of the alkene (22) depends on the nature of the solvent and on the wavelength of excitation.12 Photoelectron transfer processes between styrenes and Cu(I1) and Fe (111) species have been studied. The reactions encountered include the addition of methanol to the double bond of the styrene.13 Some styrene derivatives have been irradiated in the presence of CdS. The trans -cis isomerization still occurs but the authors suggest that electron transfer is involved forming a radical-cation.14 Interest is shown still in the isomerization of stilbene and its derivatives. A study of the pathways for the cis -trans isomerization of 4-nitro, 4,4'-dinitro, and li-nitrd'-rnethoxy stilbenes has been reported.15 The dynamics of the photoisomerization of stilbenes in hydrocarbon solution has been studied" and a comparison of the trans -cis isomerization of stilbene in low viscosity liquid alkanes arid in the gas phase has been carried 0ut.l' The photoisomerization of stilbene in straight chain alcohols has provided evidence for the existence of rotational relaxation in the excited and the ground states.18 An analysis of the isomerization rates of photoexcited stilbene has been madelg and the photobehaviour of poly deuteriated stilbene has been studied.20 De Mayo and Hasegawa have studied the cis -trans -isomerization of stilbenes (23) mediated by a CdS semiconductor." Whitten and his coworkers have continued their study of photochemical processes in organized assemblies. The present work deals with the photochemistry of the stilbenes (24),22 and on photobehaviour of surfactant ~tilbenes.'~ Pic0 second spectroscopic investigations of cis -trans -isomerization of stilbene and the derivative (25) have demonstrated the presence of an intermediate which is involved in the is~merization.'~ cis -trans -Lsomerization of several pyridinium analogues of stilbene have been studied.25 The salts (26) also undergo singlet state trms 4 s -isomerization on irradiation. A detailed mechanistic examination of these systems has been carried out26 and a physical study of the influence of solvent and quencher on the decay of the excited singlet state of the stilbene derivatives (27) has been rep~rted.~'The cis trans isomerization of bis -heteroaryl ethenes has been reported in detail.28 The direct irradiation 'of the stilbene derivative (28) brings about trans

-

cis

240

Photochemistry

n= 1 or 2

Ar

Ar

ph%

R ( 2 2 ) Ar =4-N02%H4

(23) R

=H,NO2, COZMe, CI,Me, MeO, NMez

24 1

IIIi3: Photochemistry of Alkenes, Alkynes and Related Compounds

f

l/ R

% R'

3

N

0

+NR*X-

R'

R2

(?6 1

&Clc

CI

(30) a; R = C I b; R = H

( 2 7 ) R ' = Me,N, R,N, X'= 1-or Cl0,-

R Z = Me or Et,

Photochemistry

242

Jijp)

CI

2

CI

I;

(321

&CIc

CI

(36)

YcPh

Ph

(43)

OH

Cl

(33)

IIIl3: Photochemistry of Alkenes, Alkynes and Related Compounds -isomerization

of

the

hindered

olefinic

double

bond.

243

Surprisingly benzophenone

sensitization effects isomerization of the less hindered double bond. The origin of the steric control is not known.2Q A report has suggested that the isomerization of the cyclophene (29) yielding the all trans -isomer occurs from the triplet state and is a direct six-fold process with no intervention of ground state intermediate^.^' Halogenc4kenes.- The photochemical behaviour of Afdrin (30a) is complex. A reinvestigation of the irradiation of this cyclodiene insecticide in hexane has isolated two new photo products (30b) and (31). Irradiation in acetone also provides surprises and the two new adducts (32) and (33) have been identifiede31 The influence of triethylamine on photodehalogenation of cyclodiene insecticides has also been evaluated. Irradiation appears to bring about selective dehalogenation at C-11 in (30a) yielding a 9:l mixture of the products (34a) and (34b). This stereoselective loss of chlorine is also seen with Dje/drin (35) and Endrin (36).32 Photoreduction products are obtained on the irradiation of the bromocamphene derivative (37) in non polar media. A vinyl radical is thought to be involved. In polar media, however, ether derivatives are produced via a carbocation intermediate and trapping by

Addition Reactions.- The photoelectron transfer process of the iminium salt (38) with the 3-butenoate anion results in the formation of the allylated product (39). The reaction involves decarboxylation of the 3-butenoate followed by a radical coupling reaction.34 The photoaddition of halogenated alkenes to the tetraiaza phenanthrene (40) yields products (41) of (2+2)-additi0n.~' The Eu(III)/Eu(II) photoredox system has been studied with regards to its reactivity towards a-methylstyrene. Irradiation of the system at A > 280 nm in methanol yielded the products (42) and(43).36 Alkynes.- Coyle has reviewed the photochemical reactions of e t h ~ n e . ~ The ~ photodissociation of acetylene has been studied at 193.5 nm.38 The alkyne (44) is photochemically reactive and has been studied in a variety of solvents.3Q

2 Reactions involving Cyclopropane Rings Zimmerman and Schissel have reported on the photochemical reactions of the highly crowded dienes (45-48). Within this series only the diene (45) was unreactive. All of the others undergo the di-n-methane rearrangement by both direct and sensitized irradiation as shown in Scheme A full account of the photochemical aza-di-n-methane rearrangement of the' azapentadienes (49) has been reported. The reaction provides a route to the cyclopropyl aldehyde (50). This rearrangement is of considerable interest since the parent aldehyde (51) from which the imines (49) are prepared does not undergo the corresponding oxaidi-n-methane rearrangement. The reaction reported in

244

Photochemistry

the paper is the first example of an aza-di- n-methane process in an acyclic imine.41142 Adam and his coworkers have described the synthesis and photochemistry of the divinyl ether (52). The direct irradiation of this compound gave several products which are thought t o arise from radical combination paths of the vinyl/vinyloxy radical pair. The 3-oxa-di-n-methane reactivity of this compound was not observed.43 The dicyanobicycloheptene (53) undergoes photorearrangement to yield three products. Tne first two products, (54) and (55), are the result of 1,3-carbon migrations. The third product, (56), is proposed to arise by a di-n- methane rearrangement to the nonisolated intermediate (57) which transforms into the isolated product (56). The introduction of the cyan0 groups appears to alter radically the photochemistry which such systems undergo but the authors suggest that a charge transfer mechanism is not 0perative.4~ The irradiation of the analogue (58) of the above using 254 nm light results in the formation of the isomeric product (59). Several routes were considered for the formation of this product and the authors suggest that the most likely mechanism involves photoconversion to the thermally unstable intermediate (60) followed by its rearrangement to the isolated product (59).45

A synthesis of substituted phenanthrenes has been reported using the bicyclooctadienes (61) as starting material. The process makes use of the nucleofugal group on C-8 and follows the path outlined in Scheme 3. This involves a di-.rr-methane bridging process followed by the collapse of the intermediate biradical (62).4G Normal di-n-methane behaviour is reported in the acetophenone-sensitized irradiation of the isoquinolinone derivative (63a). This yields the two products (64) and (65) as a 3:l mixture in a total yield of 75%. An N-oxide derivative gave a brown polymer with little evidence for the formation of di-Tr-methane products. The influence of ring substituents was also studied for the derivatives (63b, d) and the results of this are shown in Scheme 4. The authors conclude that the cyclization process is under LUMO control!’ Irradiation of the dihydropyridine (66) affords the oxidised pyridine (67) as the major product. A minor product (68) is also formed by a di-n- methane process.** Irradiation of the benzoazanorbornadiene (69) does not follow the conventional route for such photochemically active systems. The reaction, affords l-chloronaphthalene, by deamination, as well as two thermally labile indole derivatives (70, 71) by the route shown in Scheme 5. These are formed by 1,Snitrogen migrations within the a~anorbornadiene.~’ A detailed study of the rearrangement of the cyclopropanonaphthalene (72) has identified the products shown in Scheme 6. The reaction is solvent dependent and is more rapid in non polar solvents, such as benzene, than in polar solvents. The isomeric cyclopropanonaphthalene (73), a product of the rearrangement shown in Scheme 6, yields l-cyanonaphthalene as the principal product on irradiati~n.~’

245

IIIl3: Photochemistry of Alkenes, Alkynes and Related Compounds

Ph Ph Ph Ph

(45 1

848

Ph

h Ph Ph

Ph

Ph

(46)

& Ph Ph Ph Ph

MeS

ph&Ph

v

Ph

+& .'Ph

Ph

Ph

Ph

SMePh Ph

(48)

MeS

SMe

Scheme 2

ph45

Ph

Ph CHO

(49) R

= PhCH2, Ph, PhCHMe PhCH,CH,

( 50)

or Pr' CN

p Ph

o Ph

(51)

Photochemistry

246

CN

i

CN

(56)

(58)

(57)

CN

HgOAc

HgOAc

Me

Me

1

F y (61)

-

(62)

several steps

Me

AcOH

0

Mk Scheme 3

0;

R~=R*=H

b; R' = MeO, R2 = H C ; R' = CI, R L = H d ; R' = H, R 2 = OMe

a; ratio

3 : 1

b ; ratio 85 : 15 c ; ratio d ; ratio

79 : 21

0 : 100

75% 92.6% 55% 73%

247


(66)

CI

Me

Me

Me

(71 1 Scheme 5

H

CN

H

(72)

1

( 7 3 ) 2%

+

35 *I*

11*/*

&+&+ N

\

15 'lo

18%

Scheme 6

0 */*

248

Photochemistry

Several reports have focussed attention on the photochemical behaviour of methylene bicyclohexene derivatives. Thus the photoisomerization of the ex0 - or endo -isomers of (74) affords the methylenecy~lohexadienes(75)~~ with similar behaviour exhibited by the ethyl and is0 -propyl derivatives (76).52 Triplet sensitized irradiation of the methylene bicyclohexene (77) also brings about isomerization. The authors report that there is evidence for steric effects in the energy transfer step.53 Both the ex0 - and the endo isomers of the bicyclohex-2-ene (78) undergo excited singlet state rearrangement.54 Changes in substitution do seem to have an effect and Brune and his coworkers have examined the photobehaviour of the isomeric trifluoromethyl substituted bicyclohexenes (79). Irradiation of either of these follows a different path to the foregoing examples yielding a mixture of (80a) and (80b).55

A reinvestigation of the photobehaviour of the triene (81) at 254 nm has identified two new products (82) and (83). The authors suggest that a carbene species is involved in the formation of the cyclopropene (83).56 A detailed report, supplementing preliminary accounts, of the photo chemical behaviour of cyclonona-1,2-diene has been published. The reactivity encountered is outlined in Scheme 7.57558 Detailed studies of the behaviour of allenes (84) on irradiation have demonstrated that rearrangement to indenes occur. Thus the tetraphenyl derivative (84a) slowly affords the indene (85a) as the sole primary photo product while allene (84b), where both phenyl and hydrogen migration are possible, rearranges into indene (85b), 1,3,3-triphenylcyclopropene, and the alkyne (86). The authors have demonstrated congruence of product identities in the irradiation of allenes and cyclopropenes and also with carbenes generated thermally. From this it is clear that vinyl carbenes are implicated in allene photochemistry as outlined in Scheme 8.59 Full details of the rearrangement of the vinylcyclopropene (87) have been published.B0 This supplements a previous note.'l Electron transfer from 3,3'-dimethylbicyclopropenyl (88) to chloranil or fluoranil results in the formation of o and m -xylene in a ratio of 4:1.62 The photochemical ring opening of cyclopropyl anions has been studied and found to be substitution dependent. Thus irradiation of (89a) fails to bring about ring opening while irradiation of (89b) affords the anion (90).O3

3 Reactions of Dienes, Trienes, and Higher Polyenes Reviews have dealt with the selective isomerization of alkenes, dienes, and trienes with i n h r e d lasers,64 and with the photochemical reactivity of c u m u l e n e ~ . ~ ~ The formation of 3-anilinoalkenes (91) results on irradiation of acetonitrile solutions of cyclohexa-1,3-diene and aniline or N-methyl aniline. Similar addition occurs with the

IIIJ3: Photochemistry of Alkenes, Alkynes and Related Compounds

Me@MeMe

M e , & Me. ; Me

Me

Me M

Me

R'

'

hie

Me

e

e

i

i

Me

Me

Me

H (77) a; R' =Me, E!, Pr', R 2 = H b; R' '= H, R 2 = M e , Et, Pri

..

V

(78)

H (79)

Me

(80) a;

R' =CF3, R 2 = H ( D )

b;

R' =H(O), R2 =CF3

@+ H

H

H

hu

v 254 nm

C6H6

Me

( 7 6 ) R = Et or Pr'

(75 1

(74)

e

Meg

Me

Me@--R2

249

el + & ti

Scheme 7

H

250

Photochemistry Ph Ph

Ph Ph-

Ph

= -Qh Ph

Ph

( 8 4 ) a; R = Ph

b; R = H

(86 1

Ph ( 8 5 ) a; R = Ph

b ; R = H

Ph Scheme 8

Me

the

Ar

(87)

RL

(88)

Ph

(89) a; R' = CH=CH,, R 2 = Me, H b; R' = Ph, R z = H

Ph

H

H

I

R ( 90)

= H , Me

(91) R

(92)

Ph

Ar

OCOPh

(93) R = H Me

( 94)

0

(95)

11113: Photochemistry ofAlkenes, Alkynes and Related Compounds

251

same amines and 2,5-dimethyI hexa-2,4-diene. Alkyl amines and tertiary aniline derivatives do not undergo addition. An electron transfer mechanism is thought to be operative.? Reynolds and Bauld have studied the electron transfer reaction of the cyclohexa-l,3-diene / 1,Cdicyanobenzene system. The back electron transfer from the dicyanobenzene radical-anion to the diene radical- cation results in the formation of the diene triplet state. The outcome of the reaction was studied by product analysis."l The wavelength (185-254 nm) dependent photochemistry of cyclo-octa- and cycl-hepta-l,3-dienes has been studied68 cis,cis -Cyclohepta-1,3-diene is converted to the trans -cis -isomer (92) when irradiated in a matrix at low temperature. On warming this intermediate ring closes to afford to temperatures above -78OC bicyclo(3,2,0)hept-6ene, the same product obtained by irradiation at room temperature.6' The ionone series of compounds has been fruitful for Jeger and his coworkers. The area is clearly not exhausted and they have studied the behaviour of the epoxy dienes (93) under acetone-sensitized i r r a d i a t i ~ n . ~ ' , ~ Irradiation' ~ of the enol benzoate (94) in the presence of acid yields the isoquinolinone (95) in good yield by a mechanism involving cyclization, elimination and ~xidation.~' Matrix-isolated diene (96) undergoes photochemical transformation into the isomeric compounds (97) and (98) as the primary photo product^.^^ Maier and his coworkers have observed the photoisomerization of the cyclobutadiene dimer (99) into the pentacyclic compound The U.V. irradiation of the Dewar benzene (101) affords the paracyclophane (102, 13%).75 The prismane (103) can be produced by the irradiation of the Dewar benzene (104). The intermediacy of the benzene (105) in the transformation is likely.76 Considerable attention has been focussed, in the past year, on the photochemical transformation of steroidal dienes. Several of these reports have been lodged as patents. Thus the irradiation of the androstadienediols (106) brings about ring opening and the formation of the triene isomer (107).77 The conversion of the diene (108) to the open chain triene (109) yields a product used in enzyme immunoassay procedures.78 Irradiation of the provitamin D derivatives (110) at 254-300 nm and 310-350 nm gives the previtamin D derivatives (111) in 85% yield. This product is accompanied by small ~ (112) yield the trienes (113) amounts of tachysterols and l u m i ~ t e r o l s . ~Androstadienes and (114) on irradiation." Dauben et af. have reported the synthesis of 6-fluoro vitamin D, by a sequence involving the photoisomerization of the dehydrocholesterol (115) to the previtamin D, (116).81 An antimony-doped lamp can be used in the preparation of the lumisterols by the photoisomerization of 7-dehydrocholesterol.'' Irradiation of hydroxypyrylium cations (117) in sulphuric acid brings about photo-transposition. The yield of the rearranged products (118) and (119) is dependent

Photochemistry

252

(97 1

(90)

(100)

(99)

"2*

M

e

O

2

H

eC 0 2 M e

But

BU'

C02Me C02M e

But BuJ%

BU'

C02Me

BU'

(104)

(103)

HO

d

(105)

& \" p 2

HO

(107)

f

CO2 H

253

11113: Photochemistry of Alkenes, Alkynes and Related Compounds

(110) R 1 =

H, alkyl, acyl, trialkylsilyl R 2 = H, HO, acyloxy, alkoxy, trialkylsiloxy R3 = CH=CHCHMeCHMez, CHzCH2CH2CHMc2

C02 H

(109)

R'O (111 1 Me

Me

02CBu'

AcO (112 1

AcO

-

iso-octy I

HO

@ F (115 1

is? octyl

@ F

(116)

Photochemistry

254

OH

Me

Scheme 9

Me Me

R3

CO2Me (128)

$-R -2-

R3

Me

R! =C02Me, R2 =H, R3 =Me ( 5 4 : 4 6 ) R' =C02Me, R 2 =H, R3 =But ( 3 5 : 6 5 )

R ' =CC+H, R 2 =H, R3 =Me ( 5 6 : 4 4 )

C02Me (129)


255

upon the concentration of the acid with transposition products predominant in 100% sulphuric acid and at a minimum in 50% sulphuric acid. At these lower concentrations of acid the ring contraction product (120) is formed to ca. 100%. At O°C in 50% sulphuric acid the cyclopentenone diol (121) is produced from the irradiation of pyrylium salt (122). Product (121), at higher temperature, thermally rearranges to the acetyl furan (123). This route to the ring contracted products is operative in all the pyrylium salts studied.83 Several products are obtained on irradiation (at 254 or 300 nm) of thymol in trifluoro methane sulphonic acid. The analysis of the mixture indicates that four competitive paths are operative involving the ions (124) and (125) formed by protonation of the phenol in its excited state. The isolation of umhiiulone (126) from this complicated mixture of products is of interest and arises by a cross-conjugated dienone type A rearrangement as shown in Scheme 9.84 Other references describing the rearrangement of cross-conjugated cyclohexadienones can be found in Part 111, Chapter 2, Section 4 of this volume. A study of photochemical 1,7-hydrogen migrations. within the cycloheptatriene derivatives (127) has been reported.85 Hansen and his coworkers have demonstrated that irradiation of the heptalenes (128) brings about reversible isomerization into a mixture of isomers composed of (129) and starting material (128). To some extent, the ratio of photo-product : starting material is dependent upon the substitution as indicated by the yields shown under the appropriate structure.86 Laaxhoven et a/. report that irradiation of (130) in methanol or hexane yields (131) by the route illustrated in Scheme A mechanism involving radicals is proposed to for the transformation of P-methyl-2-vinyl stilbene into account 1-(l-indany1)-l-phenylethene on irradiation.88 Calculations have been carried out in an analysis of the photo isomerization of naphthvalene into na~hthalene.~’Photocyclization of the 2-vinylbiphenyls (132) under both direct and xanthone-sensitized irradiation conditions has been studied.” The tetraene (133) is isomerized into (134) on irradiation?’ Tochtermann et a/. have reported the photochemical conversion of the oxepine derivatives (135) into the tricyclic aldehydes (136).”

4 (2f2) Intramolecular Additions Cristol has published a short review of the syntheses of quadri~yclanes?~The photochemical cyclization of norbornadiene to quadricyclane has been achieved using acridinones and benzo-fused acridinones as sensitizers. The reaction is thought to involve an exciplex between the sensitizer and the norbornadiene.% The photoformation of quadricyclanes from norbornadienes is still one of the main approaches by organic photochemists to a workable sunlight energy storage system. Research has continued on this in the past year as seen by the several patents which

Photochemistry

256

have been lodged dealing with this process such as the synthesis of some norbornadienes of use in energy storage photocyclizations to quadricylanes has been patentedg5 A patent has been lodged dealing with the formation of the quadricyclanes (137) by irradiation of the norbornadiene derivatives (138) using acetophenone sensitization.% Novel examples, using intramolecular sensitization, have also appeared involving the norbornadiene/benzophenone derivatives (139) 97 and (140). This latter cyclization is of interest since it can be brought about in high yield by solar irradiati~n.'~ Solar irradiation is also effective in the formation of the quadricyclane (141) from the corresponding norbornadiene. Again the chemical yields are high." The photocyclization of other norbornadienes (142)loo and (143)lo' also yield the corresponding quadricyclanes.

A detailed study of the photochemical cyclization of norbornadiene to quadricyclane The quadricyclane (144) is using aryl phosphine copper(1) halides has been reported."' formed on irradiation of the norbornadiene (145) at 366 nm. The quantum yield (0.68) for the process is high. The influence of triplet sensitizers ( metal complexes, biacetyl = 0.1). The authors suggest that and acetophenone) were found to be less efficient ( the lowest singlet state of norbornadiene is much more reactive than the triplet ~tate.1'~

+

Both the acid induced and the photochemical rearrangement of the norbornadiene derivative (146) affords the hydroxynaphthalene (147). The photo-process is not affected by triethylamine and it is thought to involve benzylic-allylic G O bond cleavage. No evidence was put forward for the intermediacy of a q~adricyclane.~'~ Prinzbach and his coworkers have reported the synthesis of the oxanorbornadienes (148) and their photoconversion into the corresponding oxaquadricyclane derivatives (149) on irradiati~n."~ The azaquadricyclanes (150) have been prepared by the irradiation of the corresponding norbornadiene derivatives (151).lO6 Xanthone-sensitized irradiation of the triene (152) affords the cage compound (153) which can be converted into the benzene dimer (154) by treatment with t-butyl 1ithi~m.l'~ A synthesis of pentaprismane (155) has been developed using the photochemical ring closure of (156) to the cage compound (157) as the key step. This compound (157) can be readily converted to the corresponding ketone (158) which was elaborated to yield pentaprismane."' The cage photoproduct (159) is formed efficently (98%) by acetone- sensitized cyclization of the bis -alkene (16O).lm Paquette et a/. have synthesized the highly strained cage compound (161) by acetone-sensitized cyclization of the diene (162).110 Compound (163) is formed on irradiation of the pentaene (164) establishing the syn-arrangement of the two dicyano-alkene moieties."' In connection with cage compounds Prinzbach et a/. have also studied the photoequilibrium in the diary1 systems (165).l12 Interest in the photochemical additions in constrained systems has continued and Prinzbach and his collaborators have reported

257

11113: Photochemistry of Alkenes, Alkynes and Related Compounds

hu

(1301

(131 1 Scheme 10

(133)

(134)

(132) n = 1 - 4

G!Yo-o-"ph ( 139 1

(140)

258

Photochemistry

(142) R' and R4- R*

= ti, alkyl, a r y l

( 1 4 3 ) R' =Ph,COZEt R2 = M e , H R3 = M e , P h

& RR (148) R = H, CF3,0Me, COZMe

R'

R

& '(149)

(151)

(150) R2

R3

R4

H H COzMe COZMe

p-TOS

H

H

p -TOS

H

CI

H CI CH20CH2CSCH H H COzCHzCH=CHz H p -TOS p-Tos

COzMe


259

that the direct and acetone-sensitized irradiation of the imine (166) results in the formation of the cage structure (167).l13 Both direct and acetophenone-sensitized irradiation of the diene lactones (168) have been carried out. In the direct irradiation, three reactions occur in competition namely decarbonylation, cyclization, and the formation of the bicycloheptenones (169). Triplet sensitized irradiation yields the bicycloheptenones (169) exclusively. The cyclization of (168~)to (169c) is in competition with phenyl migration processe~."~ Salomon and his coworkers have over the years studied the influence of copper(1) triflate on the cyclization of non-conjugated dienes. In the present example the diene (170) is converted readily on irradiation in the presence of the catalyst and affords the alcohol (171). This is oxidised to the corresponding ketone.ll5 The intramolecular cyclization of the diene (172), using a copper triflate catalyst, affords the straight (2+2) adduct (173). This cyclization was used as an approach to the synthesis of Robustadial B. However, it was shown that the proposed structure of the natural product was wrong and that the robustadiah should have the camphane moiety in their structure as shown in (174).'" A mechanistic study of the (2+2)-cycloaddition reaction of the dicinnamates (175) has been reported.'"

5 Dimerization and Intermolecular Cycloadditions Acrylonitrile and methyl acrylate can be dimerised to afford trans - 1,2-cyclobutanes using (ethylene) bis -(triphenylphosphine) nickel or bis -(triphenylphosphine) Photodimerization of the coloured styrylpyrylium nickelacyclopentane as the salts (176) and (177) in the crystalline state has been reported.'" The (2+2)-photocycloadditions of 4-dimethylaminostyrene with other styrenes has been examined.12' A theoretical investigation of the mercury sensitized (2+2)-additions of penta-lY4-dienes and hexa-1,Sdienes has been reported.12' Irradiation of the cyclohexadiene / zeolite / methylene chloride system yields a mixture of the two Diels-Alder dimen, (178) and (179), of cyclohexadiene.122 Photochemical addition of alkenes to C=N systems has been studied and interpreted by means of perturbation MO theory.la3 (2+2)-Cycloadducts (180) and (181) are formed on irradiation of the isoxazoline (182) in the presence of indene.la4 The dimerization of acenaphthylene yielding head to head and head to tad dimers is dependent on the polarity of the solvent in which the irradiation is carried out. Mayer et a/. report that the dimerization in micelles produces the same ratios of products to those obtained from reaction in polar s01ution.l~~

Photochemistry

260 H

2%

Ph -/-0

0 4 - p

M

~

(159 1

NC NC’ N*

0

6

0

(160 1

CN

(163)

e

261


R2

0

(168) a ; R' = R Z = Me b ; R' = H, R2 = Pr' c ; R' = H o r M e , R 2 = P h

(167)

Go 2:: OH

H

(169)

(171 1

(170)

OMe CHPr'OH

Me0

Me0

OMe (172)

OMe (173)

OH

CH-Pr'

HO Me

Me Me

Photochemistry

2 62

Ar

Bu'

(175) R' = R 2 = H R1 = W e , R * = H R1 = H , R 2 = O M e n = 3 , 1 , 5 or 6

Ph

H

(1 79)

H

(181) a; 11 % b; 4%

(180) a; 64'10 b; 57'10

(182) a; Ar = 4-CNC6H4 b ; Ar = 4-CsHhC02Me

-

(183 ) R = 1 naphthyl , 9- phenanthryl

/SiMe3

IIIN: Photochemistry of Alkenes, Alkynes and Related Compounds

263

6 Miscellaneous Reactions Salt effects ( addition of lithium tetrafluoroborate and magnesium perchlorate) have been evaluated in the photochemical electron transfer reaction between 9,10-dicyanoanthracene and 1,2-bis -(Qmethoxyphenyl) cyclopropanes.12' Direct irradiation of the cyclopropanes (183) results in fission into alkene and dimethylcarbene as the minor reaction path. The major process encountered is ring opening to afford a butene d e r i ~ a t i v e . ' ~ ~ Adam and his coworkers have carried out a detailed study of the irradiation of cyclobutene, bicyclo(l.l.0)butane,128 and of bicyclo(2.l.O)pentane at 185 nm.12' The influence of electron transfer reagents on the photochemical behaviour of cis -1,2-diphenylcyclobutane has been assessed. In the main, the photoreactions give styrene, tram -1,Z-diphenyl cyclobutane, and l-phenyltetralin. However, change of solvent from benzene to acetonitrile leads to a decrease in the quantum yields and a diminished yield of the tetralin.13' Selective bond fission has been reported in the photoinduced electron transfer reactions of the cyclobutanes (184).131 The behaviour of the cation radicals derived from bicyclobutane systems has been under intensive study by Gassman and his coworkers. Currently they have observed that the substituted derivative (185) photorearranges in good yield, using l-cyanonaphthalene as the electron acceptor, to the isomer (186). Although this product can be synthesized independently by the photocyclization of the diene (187) the authors argue that this route is not in operation. The formation of the product (186) follows the one electron transfer path with subsequent rearrangement within the radical cation ( I M ) . ' ~ ~ The photochemical reactivity of the epoxides (189) and ( 1 9 0 ) ~ and ~ ~ (191)134 have been studied. A detailed examination of the photo-ring opening of the epoxides (192) Laser flash photolysis of to yield carbonyl ylides has been reported by George et the epoxide (193) has been carried out and a study of the resultant ylide has been r e ~ 0 r t e d . l ~ 'The related spirooxaziridines (194, 195) are also photoreactive and yield the lactams (196, 197).137 Irradiative (185 nm) conversion of the dihydrofurans (198) affords the cyclopropyl aldehydes (199).138 The photochemical fragmentation of the adduct (200) yields benzene and the photolabile dimer (201) which can also be converted into benzene on further irradiation. 13' Mariano has used his iminium salt approach as part of a synthesis of erythrina alkaloids as outlined in Scheme ll.'*'

264

Photochemistry

(192) R' =

R2 = H = H; R 2 = OMe,Me R1 = Me, OMe,CN; R2 = H R 1 =CN; R 2 = OMe R1

(195)

265

lIIl3: Photochemistry of Alkenes, Alkynes and Related Compounds

Rge

a R M e

Me

A

R'2

1198) R = C02Mc,

(199) R ' = CHO; R2:H

CH(OMe),

R' = H;

R2 = CHO

Me0

Meo%vc%Et TMs

Scheme 11

QX

X

(203) a; X = I b; X = Br

OMe ( 204)

Photochemistry

266

Davidson et a/. have reviewed the photochemistry of aryl halides.141 The corresponding ethers and carbinols are formed from the irradiation of 2-phenyl ethylbromide in the lower alcohols.142 A study of the photochemical debromination of meso -1,2-dibromostilbene in multiphase systems has been r e ~ 0 r t e d . l ~ Interest ~ in the generation of vinyl cations by irradiation of vinyl halides and related compounds has received sporadic attention over the years. In the present report Sonawane et al. have compared the photo behaviour of the dihalides (202a,b) with the mono halides (203a,b). Thus the irradiation of (202a) in methanol affords the ether (204) and the mono halide

(203a). Mono halide (203a) can be converted into the hydrocarbon (202c) on further irradiation. Lowering the temperature of the irradiation enhanced the formation of the product (204) from the ionic reaction path but suppressed this type of reactivity in the dibromo compound (202b). Interestingly no products of ionic reaction . were obtained from the irradiation of the mono halides (203)either at room temperature or at -20°C.'44 Irradiation of cyclohexyl iodide in the presence of aromatic compounds affords products of aromatic cyclohexylation by a process involving the cyclohexyl cation.14'j Cristol has continued his studies on the photo- Wagner-Meerwein processes in compounds of the type shown in (205). In this instance the influence of aryl substitution was examined.146 Other studies have reported the photochemical behaviour of the dibenzeoctadiene (206)14' and the octadienes (207).148 The photochemical reported. 14'

behaviour

of

2-aryl-1,3-diphenyl propenyl anions

(205) a; R' = CI, RZ = CI, methylsulphmy or acetoxy, R 3 = H or OMe b; R1 = H, R3 = MeO, R 2 = CI, ace t oxy or me thy lsul phoxy

&J I

(206)

has

been


267

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Photochemistrv of Aromatic Comnounds BY A. GILBERT Photo-induced c h e m i c a l change o f a r o m a t i c chromophores c o n t i n u e s t o be w i d e l y s t u d i e d and as i n p r e v i o u s y e a r s , t h e a r e a s of s u b s t i t u t i o n and c y c l i z a t i o n p r o c e s s e s a t t r a c t t h e g r e a t e s t i n t e r e s t . The r e a c t i o n s of ground s t a t e a r e n e s w i t h p h o t o g e n e r a t e d r a d i c a l s are o u t s i d e t h e p r e s e n t s c o p e b u t i n t r a m o l e c u l a r c y c l i z a t i o n s r e s u l t i n g from t h e l o s s o f h a l o g e n a c i d are c o n s i d e r e d h e r e as t h e s e p r o c e s s e s have s y n t h e t i c a p p l i c a t i o n s and are complementa r y t o t h e o x i d a t i v e c y c l i z a t i o n s described i n Section 4 of t h i s Chapter. Few r e v i e w s have a p p e a r e d d u r i n g t h e y e a r b u t L a b l a c h e Combier h a s d i s c u s s e d t h e photo-induced r e a r r a n g e m e n t , a d d i t i o n , s u b s t i t u t i o n , d i m e r i z a t i o n , and c y c l i z a t i o n r e a c t i o n s of t h i o p h e n e s i n a u s e f u l and w e l l - r e f e r e n c e d a r t i c l e . 1 1 Isomerization Reactions The p h o t o c o n v e r s i o n of 9 - t - b u t y l a n t h r a c e n e t o i t s Dewar i s o m e r (1) c o n t i n u e s t o a t t r a c t a t t e n t i o n and R u s s i a n w o r k e r s r e p o r t t h a t a l t h o u g h t h e f l u o r e s c e n c e o f t h e a n t h r a c e n e i s quenched by a n i l i n e and P J , g - d i m e t h y l a n i l i n e , t h e quantum y i e l d o f i t s p h o t o i s o m e r i z a t i o n i s u n a f f e c t e d . 2 From t h e s e o b s e r v a t i o n s i t i s deduced t h a t t h e f o r m a t i o n of (1) o c c u r s from a n o n - r e l a x e d Franck-Condon s t a t e . I t i s of i n t e r e s t here t o n o t e t h a t t h e r e v e r s e process of photoi n d u c e d c o n v e r s i o n o f D e w a r isomers t o a r e n e s h a s been u s e d t o s y n t h e s i z e C51 p a r a c y c l o p h a n e which i s t h e s m a l l e s t p a r a - b r i d g e d 3 compound s o f a r r e p o r t e d . I t was r e p o r t e d l a s t y e a r t h a t Dewar t h i o p h e n e c o u l d b e t r a p p e d a s i t s f u r a n a d d u c t from room t e m p e r a t u r e i r r a d i a t i o n e ~ p e r i m e n t s ,b~u t t h a t t h e c o r r e s p o n d i n g a d d u c t from Dewar f u r a n w a s not obtained. F u r t h e r e x p e r i m e n t s i n v o l v i n g i r r a d i a t i o n of t h i o p h e n e and f u r a n i n a r g o n matrices a t 1 0 K have, however, p r o v i d e d i n f r a r e d s p e c t r o s c o p i c e v i d e n c e f o r t h e f o r m a t i o n of b o t h Dewar isomers:6 a l l e n e s and c y c l o p r o p e n e s a r e a l s o formed, t h e l a t t e r by p h o t o r e a r r a n g e m e n t o f t h e Dewar isomer a t w a v e l e n g t h s l o n g e r t h a n 320 nm. Although n e i t h e r g- n o r 3-(trimethylsily1)pyrroles undergo p h o t o r e a r r a n g e m e n t r e a c t i o n s , i r r a d i a t i o n o f t h e 2- i s o m e r i n deg a s s e d p e n t a n e g i v e s an 84% y i e l d of t h e 3- i ~ o m e r . The ~ process

273

Photochemistry

274

But

I

&SiMe3

SiMe3

N

I

I

Me

Me

1

1, 3-Shif t

Me

0

TFf 0

(6)

+

&*”+

OH

OH ( 7 ) R = H , . R ~= Pri ( 8 ) R = Pr’, R ’ = H

IIIl4: Photochemistry of Aromatic Compounds

275

is reasonably interpreted in terms of the photoformation of the Dewar isomer ( 2 ) which undergoes a 1,3-shift followed by ring opening. Since 1973 several accounts have appeared which describe the phototransposition reactions of 4-hydroxy- to 2-hydroxy-pyrylium cations.8 It is now reported that those cations which undergo this isomerization in concentrated sulphuric acid yield ring contraction products when the reaction is carried out in 50% sulphuric acid. 9 At O°C the initial product of irradiation of the 2,3-dimethyl cation (3) is the 4,5-dihydroxycyclopent-2-enone (4) which can be isolated following neutralization, At higher temperatures a secondary acid catalyzed thermal process of ( 4 ) occurs to give acetylfurans (5). Within the year, two groups have reported on the photochemical transformations of phenols and one of these studies has led to a one-step synthesisof umbellulone (6) from thymol (7) albeit in only The reaction is carried out in trifluoromethanesul10% yield.'' phonic acid solution with either 254 or 300 nm radiation and gives nine products as well as ( 6 ) . From characterization of eight of the products, four competing photoprocesses are deduced to operate for protonated thymol: these involve rearrangement to (6), formal C2 + C3 transposition giving ( 8 ) , intermolecular transalkylation to yield the di-isopropylphenols (9), (10) and (11) and formation of piperitenone (12) by hydrogen abstraction. Other workers have examined the photoreactions of dichloromethane solutions of complexes of methyl substituted phenols with aluminium The position of the methyl groups on the phenol deterbromide." mines whether the oxonium (13) or 0x0 (14) complex will be favoured in the equilibrium and only the latter species undergo photoisomerization. The initial product is a complexed bicyclor3.1.Olhexenone which can be hydrolized to give (15) or undergo further photoreaction to give an isomeric phenol. The photoisomerization also occurs under heterogeneous conditions and irradiation of a stirred slurry of aluminosilicate in 2,3,5,6-tetramethylphenol solution leads to the formation of 2,3,4,6-tetramethylphenol. The bicyclic ketones were, however, only observed in the presence of aluminosilicate in the absence of solvent. It is of interest to note here that irradiation between 280-350 nm of the anionic form of 2chlorophenol induces an efficient ring contraction and the fornThe reaction has been - ation of cyclopentadiene carboxylic acids.12

276

Photochemistry R

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p h e n o l a t e s a n d a l s o o c c u r r e d i n n e u t r a l s o l u t i o n b u t i n t h i s case p h o t o h y d r o l y s i s t o form, f o r example, c a t e c h o l from t h e 2-chloro compound, a l s o o c c u r s . E a c h y e a r t h e r e a p p e a r r e p o r t s o f p h o t o r e a c t i o n s of aromatic Such compounds w h i c h o c c u r via n o n - a r o m a t i c i n t e r m e d i a t e s . rearrangements and p h o t o e n o l i z a t i o n o f r e a c t i o n s as di-n-methane aromatic c a r b o n y l compounds are c o n s i d e r e d e l s e w h e r e i n t h i s Volume a n d t h e l i t e r a t u r e c i t e d h e r e is i n t e n d e d t o e x e m p l i f y o t h e r t y p e s The p h o t o i s o m e r i z a t i o n o f 2 , 2 - d i p h e n y l - 1 , 4 , 4 o f process. triphenyl-3-azabut-3-en-l-one ( 1 6 ) t o ( 1 7 ) a n d (18) i s c o n s i d e r e d t o p r o c e e d by a 1 , 5 - m i g r a t i o n t o y i e l d ( 1 9 ) a n d t h e n c e t h e nonaromatic i n t e r m e d i a t e ( 2 0 ) , l 3 a n d i r r a d i a t i o n of 5 - c h l o r o - l , 4 dihydro-9-methylnaphthalen-l,4-imine (21) i n cyclohexane, y i e l d s 22% l - c h l o r o n a p h t h a l e n e a n d 1 0 a n d 12% r e s p e c t i v e l y o f t h e i s o m e r i c d i h y d r o c y c l o b u t Cbl i n d o l e s ( 2 2 ) a n d ( 2 3 ) . l4 The n o n - a r o m a t i c i n t e r m e d i a t e ( 2 4 ) is s u g g e s t e d i n t h e l a t t e r r e a c t i o n a n d t h i s p r o c e s s c o n t r a s t s i n t e r e s t i n g l y w i t h t h a t r e p o r t e d f o r nonc h l o r i n a t e d d e r i v a t i v e s ( 2 5 ) which are r e p o r t e d t o g i v e ( 2 6 ) a s t h e major p r o d u c t . l5 S e v e r a l r e p o r t s f r o m C r i s t o l a n d c o - w o r k e r s d e s c r i b e t h e p h o t o r e a c t i o n s of v a r i o u s d e r i v a t i v e s o f 2 , 3 : 6 , 7 - d i b e n z o 16-20 bicycloC3.2.1locta-2,6-dienes a n d of s i m i l a r C 2 . 2 . 2 l o c t a d i e n e s . I n t r a m o l e c u l a r c y c l i z a t i o n t o g i v e non-benzenoid i n t e r m e d i a t e s is t h e k e y s t e p i n p h o t o Wagner-Meerwein r e a r r a n g e m e n t s of s u c h s y s t e m s a n d i n t h e u n p r e c e d e n t e d r e a c t i o n t o form p h e n a n t h r e n e s a n d 9,lO-dihydrophenanthrenes f r o m ( 2 7 ) .I6 The f o r m a t i o n o f t h e p h e n a n t h r e n e s i s a t r i p l e t s t a t e p r o c e s s a n d is promoted by t h e p r e s e n c e of a n u c l e o f u g a l g r o u p a t C-8. The mechanism i s c o n s i d e r e d t o i n v o l v e i n t r a m o l e c u l a r e l e c t r o n t r a n s f e r from t h e e x c i t e d

s t a t e of a n aromatic r i n g t o t h e C - n u c l e o f u g a l bond t o f o r m a z w i t t e r i o n i c b i r a d i c a l which o n l o s s o f t h e n u c l e o f u g e y i e l d s t h e intermediates outlined i n ( 2 8 ) a n d h e n c e t h e p h e n a n t h r e n e &y Scheme 1. 2 Addition Reactions I t i s twenty y e a r s s i n c e t h e first r e p o r t s a p p e a r e d d e s c r i b i n g t h e i n t r i g u i n g p r o c e s s o f meta p h o t o c y c l o a d d i t i o n o f e t h y l e n e s t o t h e b e n z e n e r i n g which c o n v e n i e n t l y y i e l d s t h e d i h y d r o s e m i b u l l v a l e n e s k e l e t o n ( 2 9 ) .21 Numerous p u b l i c a t i o n s c o n c e r n e d w i t h b o t h t h e m e c h a n i s t i c a n d s y n t h e t i c a s p e c t s of t h e r e a c t i o n h a v e a p p e a r e d a n d w h i l e t h e l a t t e r h a v e b e e n , a n d c o n t i n u e t o he, over t h e years

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e x p l o i t e d , t h e r e are s t i l l d e t a i l s o f t h e mechanism which r e m a i n t o b e c l a r i f i e d . D i f f e r e n c e s between a d d e n d i o n i z a t i o n p o t e n t i a l w ( A 1 . P . ) have i n t h e p a s t been used t o p r e d i c t p r e f e r r e d arenee t h y l e n e r e a c t i o n modes,22 b u t M a t t a y h a s now p r o p o s e d t h a t t h e f r e e e n t h a l p y o f e l e c t r o n t r a n s f e r (ACI) between t h e r e a c t a n t s p r o v i d e s a c o n v e n i e n t method w i t h f e w e r e x c e p t i o n s t h a n t h a t involving A 1 . P . f o r determining and r a t i o n a l i z i n g favoured pathw a y ~ .Thus ~ ~ f o r s y s t e m s i n which t h e e l e c t r o n t r a n s f e r becomes e x e r g o n i c , t h a t is t o s a y A G is l e s s t h a n 0 , t h e n s u b s t i t u t i o n i s p r e f e r r e d a n d c y c l o a d d i t i o n o c c u r s when AG i s g r e a t e r t h a n 0. T h i s s i t u a t i o n i s w e l l - i l l u s t r a t e d by t h e p h o t o r e a c t i o n s o f a , a , a - t r i f l u o r o t o l u e n e w i t h v a r i o u s d i o x o l e s and v i n y l e n e carbone x a m p l e , 2 5 4 nm i r r a d i a t i o n o f t h e a r e n e w i t h 2 , 2 , 4 , 5 a t e ~ .F o~r ~ d i m e t h y l - l , 3 - d i o x o l e ( A G < O ) y i e l d s t h e p r o d u c t o f s u b s t i t u t i o n by t h e e t h y l e n e a t t h e -CF3 g r o u p whereas w i t h v i n y l e n e c a r b o n a t e ( A G > O ) meta c y c l o a d d u c t s are t h e p r i n c i p a l p r o d u c t s . For addend p a i r s which h a v e AC_ a p p r o x i m a t e l y e q u a l t o 0 t h e p r o d u c t r a t i o i s m a r k e d l y i n f l u e n c e d by s o l v e n t p o l a r i t y a n d w h i l e t h e s u b s t i t u t i o n process is l a r g e l y u n a f f e c t e d t h e e f f i c i e n c y of c y c l o a d d i t i o n f a l l s a p p r e c i a b l y o n c h a n g e from c y c l o h e x a n e t o a c e t o n i t r i l e as t h e s o l v e n t . F u r t h e r , from examination o f a c o n s i d e r a b l e range o f a r e n e - e t h y l e n e s y s t e m s i t i s n o t e d t h a t a s t h e A G v a l u e between t h e a d d e n d s i n c r e a s e s t h e n t h e r a t i o o f meta t o o r t h o c y c l o a d d i t i o n a l s o i n c r e a s e s 2 5 b u t i t i s e v i d e n t from t h e s e a n d p r e v i o u s s t u d i e s o n t h i s a s p e c t of t h e s e p h o t o c y c l o a d d i t i o n r e a c t i o n s t h a t n e i t h e r A 1 . P . n o r a b s o l u t e v a l u e s o f AG_ c a n p r e d i c t s u c h r a t i o s f o r a l l systems and a u n i v e r s a l l y a p p l i c a b l e measure o f t h e p o l a r f a c t o r s s t i l l a w a i t s d i s c o v e r y . Over t h e y e a r s , s e v e r a l mechanisms h a v e b e e n c o n s i d e r e d f o r t h e meta p h o t o c y c l o a d d i t i o n b u t t h a t which seems t o r a t i o n a l i z e a l l t h e e x p e r i m e n t a l r e s u l t s i n v o l v e s t h e i n t e r m e d i a c y o f t h e s p e c i e s ( 3 0 ) a s t h e immediate adduct p r e c u r s o r and a t l e a s t i n t h e case o f t h e a d d i t i o n s of d i o x o l e s t o b e n z e n e a n d t o l u e n e t h i s i n t e r m e d i a t e r e s u l t s from c o l l a p s e o f a n S1 a r e n e - S o e t h y l e n e e x c i p l e x . 2 6 I n a n a t t e m p t t o g a i n f u r t h e r i n f o r m a t i o n o n which bond ( s ) i n t h e meta c y c l o a d d u c t i s ( a r e ) formed i n t h e p r i m a r y s t e p , and which bond f o r m a t i o n is r a t e d e t e r m i n i n g , C o r n e l i s s e and co-workers have measured deuterium i s o t o p e e f f e c t s on t h e r e a c t i o n o f t o l u e n e and a n i s o l e w i t h c y c l o p e n t e n e . 27 R e p l a c e m e n t o f m e t h y l h y d r o g e n by d e u t e r i u m g i v e s e f f e c t s which are i n a g r e e m e n t w i t h t h e a b o v e g e n e r a l mechanism b u t


28 1

t h e a u t h o r s n o t e t h a t normal e f f e c t s o b s e r v e d w i t h 3,5- a n d 2 , 6 -

d e u t e r a t i o n of t h e a r e n e c a n n o t be r e a d i l y e x p l a i n e d , I t i s , however, deduced t h a t s i n c e t h e s e e f f e c t s c a n be measured i n intermolecular competition experiments, t h e formation o f t h e cyclop r o p a n e r i n g i n t h e i n t e r m e d i a t e species ( 3 0 ) i s t h e r a t e d e t e r m i n i n g s t e p . The e x t e n t o f p o l a r i t y i n t h e r e a c t i o n i n t e r m e d i a t e ( 3 0 ) \and i n d e e d e v i d e n c e f o r i t s i n v o l v e m e n t i n t h e r e a c t i o n , are p o i n t s o f c u r r e n t c o n c e r n . The r e g i o c h e m i s t r y o f t h e a d d i t i o n o f c y c l o p e n t e n e t o 3- a n d 4 - c y a n o a n i s o l e s i s r e p o r t e d t o be c o n s i s t e n t w i t h a mechanism i n v o l v i n g a d i p o l a r s p e c i e s and i n t h i s same a c c o u n t it is a l s o n o t e d t h a t p o s i t i o n a l a d d u c t i s o m e r s c a n be both thermally a n d p h o t o c h e m i c a l l y i n t e r c o n v e r t e d : 28 t h i s makes mechani s t i c d e d u c t i o n s based o n p r o d u c t r a t i o s from G . C , a n a l y s i s a n d / o r from p r o l o n g e d i r r a d i a t i o n somewhat d u b i o u s . For example, t h e isomers (31) and ( 3 2 ) i n t e r c o n v e r t by a n e t h e n y l c y c l o p r o p a n e c y c l o p e n t e n e r e a r r a n g e m e n t and t h e e q u i l i b r i u m p o s i t i o n f a v o u r s t h e f o r m e r isomer t h e r m a l l y and t h e l a t t e r p h o t o c h e m i c a l l y . Such p r e v i o u s l y u n r e c o g n i s e d l a b i l i t i e s o f meta p h o t o c y c l o a d d u c t s may well a c c o u n t f o r t h e r e p o r t t h a t t h e r e l a t i v e y i e l d s o f t h e p a r a a n d meta a d d u c t s (33) and ( 3 4 ) r e s p e c t i v e l y from c y c l o n o n a - 1 , 2 ~ ~ the d i e n e and benzene a s d e t e r m i n e d by n . m . r . s ~ e c t r o s c o p yare r e v e r s e o f t h o s e based on G.C. a n a l y s i s . 30 The s t e r e o c h e m i s t r y of t h e meta a d d u c t s from i r r a d i a t i o n o f a n i s o l e a n d benzene w i t h 2-methyl-1,3-dioxole are s i m i l a r l y i n t e r p r e t e d i n terms of p o l a r i t y w i t h i n t h e i n t e r m e d i a t e ( 3 0 ) . 3 1 The predominance o f t h e exo a d d u c t s (35) from b o t h s y s t e m s is c o n s i d e r e d t o r e f l e c t t h a t r e p u l s i o n between t h e n e g a t i v e l y c h a r g e d p - o r b i t a l s o f t h e d e l o c a l i z e d a l l y l i c s y s t e m i n (30) and t h e o r b i t a l s o f t h e oxygen i n h i b i t s a n endo a p p r o a c h o f t h e addends. The a u t h o r s a l s o n o t e t h a t by t h e t i m e t h e o r i e n t a t i o n of t h e addend i s d e t e r m i n e d , t h e d i p o l a r c h a r a c t e r of t h e 6-membered r i n g i s a l r e a d y d e v e l o p e d . A p r e v i o u s a t t e m p t t o g e n e r a t e a r a d i c a l s p e c i e s ( 3 0 ) by a n i n d e p e n d e n t thermal r o u t e was u n s u c c e s ~ f u lb~u t~ i t is now r e p o r t e d t h a t d i r e c t and s e n s i t i z e d i r r a d i a t i o n o f t h e a z o compounds (36) and ( 3 7 ) which are r e s p e c t i v e l y formed from t h e meta p h o t o c y c l o a d d u c t s ( 3 8 ) and (39) of c y c l o p e n t e n e and m_-xylene, y i e l d s t h e two meta c y c l o a d d u c t s i n t h e same r a t i o a s t h a t o b s e r v e d i n t h e p h o t o a d d i t i o n r e a c t i o n . 3 3 T h i s r e s u l t i s s u p p o r t e d by t h a t from t h e c y c l o p e n t e n e - 2 - x y l e n e s y s t e m and h e n c e t h e s e d a t a are c o n s i d e r e d t o p r o v i d e direct e v i d e n c e f o r t h e i n t e r m e d i a c y o f t h e b i r a d i c a l

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(48)


283

s p e c i e s i n t h e meta p h o t o c y c l o a d d i t i o n p r o c e s s . D e t a i l s of t h e H ' n.m.r. s p e c t r a l d a t a o f t h i r t y meta p h o t o c y c l o a d d u c t s o f 34 benzenoid compounds and e t h y l v i n y l e t h e r have been p u b l i s h e d : t h e s e d a t a w i l l be much a p p r e c i a t e d by o t h e r w o r k e r s i n t h i s a r e a . Wender and co-workers c o n t i n u e t o make e l e g a n t s y n t h e t i c u s e o f t h e i n t r a m o l e c u l a r meta p h o t o c y c l o a d d i t i o n o f p h e n y l e t h e n y l non-conjugated b i c h r o m o p h o r i c s y s t e m s and t h i s y e a r d e s cribe t h r e e such a p p l i c a t i o n s o f t h e r e a c t i o n . The s y n t h e s i s o f ( + ) - s i l p h i n e n e ( 4 0 ) , t h e f i r s t member of a new f a m i l y of t r i q u i n a n e n a t u r a l p r o d u c t s , h a s been a c h i e v e d i n t h r e e s t e p s and i n v o l v e s t h e i n t r a m o l e c u l a r p h o t o c y c l o a d d i t i o n o f t h e bichromop h o r e (41) a s t h e k e y r e a c t i o n . 3 5 I r r a d i a t i o n of ( 4 1 ) i n p e n t a n e y i e l d s ( 4 2 ) and ( 4 3 ) i n a 1:l r a t i o by t h e two p o s s i b l e modes of c y c l o p r o p a n e f o r m a t i o n i n t h e i n t e r m e d i a t e s p e c i e s ( 4 4 ) and as f o r some o t h e r s y n t h e t i c a p p l i c a t i o n s of t h i s r e a c t i o n o n l y one i s o m e r , i n t h i s case ( 4 2 ) , h a s t h e r e q u i r e d s t r u c t u r e f o r e l a b o r a t i o n t o t h e t a r g e t compound. C o n t r o l o v e r t h e d i r e c t i o n of c y c l o p r o p a n e f o r m a t i o n i n meta p h o t o c y c l o a d d i t i o n would d o u b t l e s s improve t h e a c c e p t a b i l i t y o f t h e p r o c e s s as a s y n t h e t i c p r o c e d u r e p a r t i c u l a r l y f o r a s y s t e m which y i e l d s a d d u c t s t h a t are n o t c o n v e n i e n t l y a n d / o r e f f i c i e n t l y i n t e r c o n v e r t e d t h e r m a l l y or p h o t o The p h o t o p r o d u c t s ( 4 5 ) and ( 4 6 ) formed i n a resp e c t i v e r a t i o of 1:1.88 from t h e bichromophore ( 4 7 ) a r e , however, r e p o r t e d t o b e p h o t o - i n t e r c o n v e r t e d a l t h o u g h competing decomposit i o n d o e s o c c u r . 3 6 The minor isomer ( 4 5 ) is c o n v e r t e d i n 6-7 s t e p s i n t o ( + ) - s i l p h i p e r f o l - 6 - e n e ( 4 8 ) and (?)-7aH- ( 4 9 ) and (+)-7@H-(50)-silphiperfol-5-enes i n o v e r a l l y i e l d s of 8 . 4 , 5 . 0 , and 6 . 0 % r e s p e c t i v e l y . The s u c c e s s which h a s a l r e a d y been a c h i e v e d i n t h e a p p l i c a t i o n of t h i s i n t r a m o l e c u l a r c y c l o a d d i t i o n p r o c e s s i s r e m a r k a b l e and t h e p o t e n t i a l u t i l i t y o f t h e r e a c t i o n is f u r t h e r emphasised by i t s e x t e n s i o n t o f o r m a t i o n o f seven-membered r i n g s w i t h t h e f i r s t t o t a l s y n t h e s i s of t h e a n t i l e u k e m i c a g e n t The bichromophore (52) y i e l d s a r e s p e c t i v e ( ? ) - r u d m o l l i n (51). 37 r a t i o o f 2 . 3 : l of t h e two i n t r a m o l e c u l a r a d d u c t s ( 5 3 ) and ( 5 4 ) and w h i l e c o n v e r s i o n t o a common p r o d u c t from s u c h i s o m e r s h a s t o o c c u r by bromine-induced c l e a v a g e of p r e v i o u s l y been shown t h e i n t e r n a l c y c l o p r o r a n e r i n g , i n t h e p r e s e n t c a s e , f o r m a t i o n of t h e r e q u i r e d a l c o h o l ( 5 5 ) is a c h i e v e d from e i t h e r ( 5 5 ) o r ( 5 4 ) by t h e i r t r e a t m e n t w i t h m e r c u r i c acetate. The c o n v e r s i o n o f ( 5 5 ) t o ( 5 1 ) is a c h i e v e d i n f i f t e e n s t e p s . The f e a s i b i l i t y of u s i n g t h e

Photochemistry

284

(49) R = H, R1 = Me (50) R =Me, R’ = H

OH OMe

(57)

(56)

(58) R = OMe (60) R = CHN2 (611 R = OCO *CH2CHMe2

Me

C0,Me

(59)

F5 (62) X = O (64) X = 5

(63)

285

IIii4: Photochemistry of Aromatic Compounds

(68)

(65)

Y - s h i f t

(6 7)

&

Me

0

Me0

(70)

(69)

(75)

(72) R = CN (74) R = -CH=CH,

X =OorS

(71)

Y = 0, NH, or NMe

R = M e or H

Photochemistry

286

Me

(77)

(78) R = H, Me, or Ph

(79)

R

Me

(80)

(81)

f+ 0

(84)

(85)X-Y (86)X-Y (87)X-Y

= -NMe-

= -NMe-

CH(Me)--CH(Me)-

= -CH(Mel-CH(Mc)-NMc-

11114: Photochemistry of Aromatic Compounds

287

i n t r a m o l e c u l a r meta c y c l o a d d i t i o n a s a k e y s t e p t o w a r d s ( 5 . 5 . 5 . 5 ) f e n e s t r a n e s h a s b e e n p r e v i o u s l y i n v e s t i g a t e d by Keese a n d cow o r k e r ~a n~d ~ t h e same g r o u p now r e p o r t s s u c c e s s i n t h i s a p p r o a c h b y t h e s y n t h e s i s o f t h e f e n e s t r a - d i e n o n e ( 5 6 ) . 3 9 The s t a r t i n g m a t e r i a l i s t h e b i c h r o m o p h o r e ( 5 7 ) which on i r r a d i a t i o n i n d e g a s s e d hexane and i n a c c o r d w i t h s t e r i c and c o n f o r m a t i o n a l c o n s i d e r a t i o n s u n d e r g o e s 1 , 3 - c y c l o a d d i t i o n a s t h e major r e a c t i o n t o g i v e t h e two i s o m e r s ( 5 8 ) a n d ( 5 9 ) i n a r e s p e c t i v e y i e l d o f 3 : 4 . Isomer (58) is r e a d i l y c o n v e r t e d t o ( 5 6 ) by t r e a t m e n t of t h e d i a z o k e t o n e (60), p r o d u c e d f r o m t h e mixed a n h y d r i d e ( 6 1 ) , w i t h t r i f l u o r o a c e t i c acid. Intramolecular ortho-cycloaddition

of benzene-ethylene systems

h a s o n l y been p r e v i o u s l y r e p o r t e d f o r s y s t e m s i n which t h e t w o c h r o m o p h o r e s a r e h e l d i n a f a v o u r a b l e ~ r i e n t a t i o n . ~ ' I t is now, h o w e v e r , r e p o r t e d b y w o r k e r s who h a v e c o n t r i b u t e d much t o t h e understanding of t h e photoreactions of f l u o r i n a t e d benzenes, t h a t 254 nm i r r a d i a t i o n o f pentafluorophenyl-prop-2-enyl e t h e r ( 6 2 ) i n cyclohexane r e s u l t s i n t h e formation of t h e 1,2-cycloadduct I n c o n t r a s t tetrafluoropyridyl-prop-2-enyl

(63).

41

i s s t a b l e u n d e r t h e same

c o n d i t i o n s a n d t h e t h i o e t h e r ( 6 4 ) u n d e r g o e s C-S bond c l e a v a g e t o g i v e p e n t a f l u o r o t h i o p h e n o l a n d cyclohexylpentafluorophenyl s u l p h i d e . The p h o t o r e a r r a n g e m e n t of ( 6 5 ) t o ( 6 6 ) h a s p r e v i o u s l y been proposed t o arise & y

a [ 3 , 5 l s i g m a t r o p i c s h i f t , 4 2 b u t f r o m a re-

e x a m i n a t i o n o f t h e r e a c t i o n i t i s now s u g g e s t e d t h a t t h e mechanism

-

i n v o l v e s a n i n t r a m o l e c u l a r S1 a r e n e So e t h y l e n e e x c i p l e x which Rather than yield t h e intramol-

collapses t o t h e species (67).43

e c u l a r o r t h o cycloadduct, ( 6 7 ) is considered t o undergo c y c l i s a t i o n

t o ( 6 8 ) which by a 1 , 3 - s h i f t y i e l d s ( 6 6 ) . The p h o t o r e a c t i o n o f 1 , 3 - d i e n e s w i t h b e n z e n o i d compounds t y p i c a l l y y i e l d s c o m p l e x m i x t u r e s of p r o d u c t s a n d t h e r e a c t i o n o f (69) w i t h b e n z e n e is s e e m i n g l y no e x c e p t i o n . 4 4

The 1 , 4 - 1 ' , 4 ' -

adduct ( 7 0 ) i s , however, i s o l a t e d and i n f o u r f u r t h e r s t e p s , one of which i n v o l v e s x a n t h o n e - s e n s i t i z e d

photocyclization,

pentacyclo

C6.4.0. 0 2 ' 7 0 3 9 1 2 0 6 J 9 1 d o d e c a - 4 , 1 0 - d i e n e (71) is obtained, a l b e i t i n o n l y 2% y i e l d . The p h o t o r e a c t i o n o f f u r a n w i t h b e n z e n e a l s o g i v e s a v a r i e t y of a d d u c t s , b u t by t h e u s e of c o n j u g a t i v e s u b s t i t u e n t s o n t h e a r e n e , t h e a d d i t i o n p r o c e s s h a s been r e n d e r e d r e g i o - a n d s t e r e o - s p e c i f i c . 45 T h u s i r r a d i a t i o n o f b e n z o n i t r i l e i n t h e p r e s e n c e o f f u r a n p r o d u c e s t h e 2,6-2'5'-e= adduct (72) e x c l u s i v e l y a n d t h i s is c o n s i d e r e d t o r e s u l t f r o m a n i n t e r a c t i o n b e t w e e n t h e

Photochemistry

288

cyano s u b s t i t u e n t a n d t h e f u r a n which p r o d u c e s t h e o r i e n t a t i o n (73).

A similar d i r e c t i n g e f f e c t is observed f o r t h e r e a c t i o n

w i t h p h e n y l a c e t y l e n e a n d i t would a p p e a r t h a t e v e n t h e v i n y l g r o u p h a s some c o n t r o l s i n c e s t y r e n e and f u r a n , d e s p i t e an e x p e c t e d non-ideal

a l i g n m e n t f o r a d d i t i o n t o t h e b e n z e n e ring, g i v e ( 7 4 ) a s

w e l l as t h e 2 ? ~ + 2 7p~r o d u c t ( 7 5 ) on i r r a d i a t i o n . The s e n s i t i z e d p h o t o c y c l o a d d i t i o n o f maleic a n h y d r i d e d e r i v a t i v e s t o thiophenes to give t h e

exo

a d d u c t s ( 7 6 ) h a s b e e n known f o r

some t i m e a n d t h e r e a c t i o n h a s now been s u b j e c t e d t o a m e c h a n i s t i c study.46

I t would a p p e a r f r o m t h e p r e s e n t r e s u l t s t h a t t h e e n e r g y

a c c e p t o r s i n t h i s p r o c e s s can be t h e a n h y d r i d e , t h e t h i o p h e n e , and

a c h a r g e - t r a n s f e r complex b e t w e e n t h e a d d e n d s . The p h o t o r e a c t i v i t y o f n a p h t h a l e n e d e r i v a t i v e s w i t h e t h y l e n e s i s v e r y d e p e n d e n t o n t h e p o s i t i o n of t h e a r e n e s u b s t i t u e n t a n d t h e p a r t i c u l a r e t h y l e n e employed. Thus w h i l e t h e c a p t o d a t i v e e t h y l e n e , a - m o r p h o l i n o a c r y l o n i t r i l e ( 7 7 ) g i v e s 55-72% of t h e 1 , 4 - c y c l o adduct ( 7 8 ) w i t h l - a c y l n a p h t h a l e n e s , 2-acetonaphthone i s u n r e a c t S i m i l a r p r o d u c t s t o ( 7 8 ) a r e , however, formed from Me3CSC( : CH2)CN a n d 1- and 2 - n a p h t h a l d e h y d e s a n d t h e t r i p l e t s t a t e of t h e a r e n e i s i m p l i c a t e d i n t h e a d d i t i o n r e a c t i o n . The r e s u l t s o f f u r t h e r s t u d i e s i n t o t h e d i v e r s e a d d i t i o n r e a c t i o n s o f N,methylnaphthalene dicarboximides have been p u b l i s h e d .

A t wave-

l e n g t h s l o n g e r t h a n 320 nm, a l k e n e s u n d e r g o r e g i o s p e c i f i c p h o t o a d d i t i o n t o t h e 1 , 8 - i m i d e ( 7 9 ) t o g i v e , f o r e x a m p l e , ( 8 0 ) i n good y i e l d s a n d 1 , 3 - d i e n e s b e h a v e s i m i l a r l y t o p r o d u c e ( 8 1 ) . 4 8 I n cont r a s t , t h e p h o t o r e a c t i o n of ( 7 9 ) w i t h f u r a n p r o d u c e s ( 8 2 ) and ( 8 3 ) i n approximately equal y i e l d s *,it

is suggested, t h e oxetan ( 8 4 ) ,

and t h e 1,2-dimide

(85) with a l k e n e s undergoes photo-induced CO-NMe i n s e r t i o n t o g i v e ( 8 6 ) a n d ( 8 7 ) . 4 9 The same w o r k e r s h a v e

a l s o shown t h a t i n m e t h a n a l s o l u t i o n a n d i n t h e p r e s e n c e of 1 , l - d i p h e n y l e t h y l e n e , ( 7 9 ) a c t s as a t y p i c a l e l e c t r o n t r a n s f e r p h o t o s e n s i t i z e r f o r t h e anti-hlarkovnikoff a d d i t i o n and 2,2d i p h e n y l e t h y l m e t h y l e t h e r i s formed i n 70% y i e l d w i t h 93% o f ( 7 9 ) 50 being recovered. The p h o t o r e a c t i o n s o f a n t h r a c e n e i n t h e p r e s e n c e o f t r a n s t r a n s hexa-2,4-diene

have been re-examined.

The p r o d u c t s from t h e

r e a c t i o n a r e t h e a n t h r a c e n e d i m e r , t h e two isomers ( 8 8 ) a n d ( 8 9 ) o f C4+4lcycloaddition t o t h e 9 , l O - p o s i t i o n s of t h e a r e n e , and a 51 C2+41 a d d u c t ( 9 0 ) as w e l l as s e v e r a l u n i d e n t i f i e d m i n o r a d d u c t s . D i m e r i z a t i o n of t h e a r e n e i s r e d u c e d by t h e d i e n e r a t h e r t h a n enhanced, and a Diels-Alder r e a c t i o n of t h e s t r a i n e d t r a n s

IIII4: Photochemistry of Aromatic Compounds

289

e t h y l e n e i n t h e m a j o r a d d u c t (88) a n d a n t h r a c e n e t o g i v e ( 9 1 ) a c c o u n t s f o r t h e h i g h a r e n e l o s s w h i c h h a d been p r e v i o u s l y c o n s i d -

ered t o a r i s e f r o m t h e d i m e r i z a t i o n p r o c e s s .

These f i n d i n g s sub-

s t a n t i a t e t h e e a r l i e r q u a l i t a t i v e r e s u l t s and c o n c l u s i o n s o f Kaupp a n d T e ~ f e l . The ~ ~ a d d u c t s ( 8 8 ) , ( g o ) , a n d ( 8 9 ) are f o r m e d i n r e s p e c t i v e y i e l d s o f S l X , 1 4 % , a n d < 5% f r o m t h e s i n g l e t e x c i p l e x w h e r e a s t r i p l e t q u e n c h i n g a n d s e n s i t i z a t i o n s t u d i e s show t h a t ( 9 0 ) i s t h e major p r o d u c t f r o m t h e t r i p l e t p a t h w a y which a l s o y i e l d s a n a d d u c t o f unknown s t r u c t u r e . P h o t o a d d i t i o n o f a l i p h a t i c a m i n e s t o benzene53 a n d n a p h t h a l e

n

e w~a s ~r e ~p o r t e d many y e a r s a g o b u t t h e p r o c e s s i n v o l v i n g

ammonia a n d v a r i o u s p r i m a r y a m i n e s w i t h p h e n a n t h r e n e , a n t h r a c e n e and n a p h t h a l e n e h a s been examined i n t h e p r e s e n c e o f 2-dicyanob e n z e n e . 55

R e a c t i o n s are i n a c e t o n i t r i l e - w a t e r m i x t u r e s and y i e l d s

o f t h e a m i n a t e d a r e n e s ( 9 2 ) , ( 9 3 ) , a n d ( 9 4 ) are b e t w e e n 48-95%. The mechanism f o r t h e p h o t o - a m i n a t i o n

is r e a s o n a b l y s u g g e s t e d t o

i n v o l v e n u c l e o p h i l i c a t t a c k o f t h e amine on t o t h e c a t i o n r a d i c a l o f t h e a r e n e w h i c h i s g e n e r a t e d by p h o t o - i n d u c e d e l e c t r o n t r a n s f e r

t o t h e dicyanobenzene.

I r r a d i a t i o n at wavelengths longer than

500 nm of d i c h l o r o m e t h a n e s o l u t i o n s o f t h e c h a r g e - t r a n s f e r

com-

plexes of various anthracenes with tetranitromethane leads t o rapid b l e a c h i n g o f t h e s o l u t i o n and r e g i o - and s t e r e o - s p e c i f i c f o r m a t i o n of t h e a d d u c t s ( 9 5 ) i n h i g h y i e l d . 5 6

Again t h e r e a c t i o n i s c o n -

s i d e r e d t o p r o c e e d b y e l e c t r o n t r a n s f e r and t h e m u l t i - s t e p p a t h w a y involving t h e g e m i n a t e s p e c i e s [Ant C(N02)3- NO;]

is discussed.

Two f u r t h e r p h o t o a d d i t i o n s t o aromatic r i n g s r e p o r t e d w i t h i n t h e y e a r are t h e f o r m a t i o n o f a d i a s t e r e o i s o m e r i c m i x t u r e o f ( 9 6 ) produced from i r r a d i a t i o n o f t h e 9-(B-D-ribofuranosyl)

purine (97)

i n methanol,57 and t h e c o n v e r s i o n o f n a p h t h o l s and a n t h r o l s i n t h e

t o t h e corresponding quinone The l a t t e r p r o c e s s makes u s e o f t h e e n h a n c e d a c i d i t y o f t h e s i n g l e t e x c i t e d s t a t e o f p h e n o l s t o c a u s e d i s s o c i a t i o n of t h e N - n i t r o s o compound i n n e u t r a l salts.

presence of g-nitrosodimethylamine mono-oxime

3

i n c h e m i c a l y i e l d s o f 64-84%.58

Substitution Reactions

Each y e a r it i s e v i d e n t t h a t p h o t o s u b s t i t u t i o n p r o c e s s e s o f aromatic s y s t e m s c a n n o t r e a d i l y be c l a s s i f i e d a n d a g a i n t h e o r d e r of reviewing the l i t e r a t u r e i n t h i s Section is largely arbitrary. F u r t h e r d e t a i l s and a p p l i c a t i o n s have appeared o f t w o r u l e s which w e r e f i r s t p r o p o s e d i n 1984 t o r a t i o n a l i z e t h e r e g i o c h e m i s t r y o f

Photochemistry

290

(92)

(91)

NHZ

(95) R = NO,, CN, CHO, C02Me, COMe CI, Br, H, Ph or OCOMe

(93)

hv

MeOH

AcoG AcO

AcO (97)

OAC

(96)

OAc


291

p h o t o - i n d u c e d n u c l e o p h i l i c aromatic s u b s t i t u t i o n . 5 9 The r u l e s a r e based on f r o n t i e r m o l e c u l a r o r b i t a l t h e o r y and c o n s i d e r e d t o be widely a p p l i c a b l e .6 o I n n u c l e o p h i l i c p h o t o s u b s t i t u t i o n s proceeding by a a-complex formed i n o n e s t e p from i n t e r a c t i o n between t h e e x c i t e d a r e n e a n d n u c l e o p h i l e , t h e r e g i o c h e m i s t r y is r e p o r t e d t o be c o n t r o l l e d by t h e HOMO of t h e s u b s t r a t e w h e r e a s r e a c t i o n s i n v o l v i n g t h e e l e c t r o n t r a n s f e r t o a n i t r o a r o m a t i c from a n u c l e o p h i l e a n d c o m b i n a t i o n o f t h e r a d i c a l i o n s a r e LUMO-controlled. A s w e l l as a n a l y z i n g v a r i o u s s u b s t i t u t i o n p r o c e s s e s by t h e s e r u l e s , t h e p r o p o s e r s r e p o r t s u p p o r t for t h e s e c o n d o f t h e r u l e s f r o m t h e i r r a d i a t g o n o f 4 - n i t r o n a p h t h y l e t h e r s ( 9 8 ) which y i e l d s The same g r o u p a l s o r e i n f o r c e t h e e a r l i e r t h e isomers ( 9 9 ) . 6 1 p r o p o s a l e 2 t h a t t h e p h o t o - S m i l e s r e a r r a n g e m e n t p r o c e e d s via an i n t r a m o l e c u l a r r a d i c a l i o n p a i r a n d a M e i s e n h e i m e r complex a n d q u a l i t a t i v e l y d e s c r i b e t h e r e a c t i o n p a t h by t h e u s e o f h y p e r s u r 63 f a c e s f o r t h e ground, c h a r g e - t r a n s f e r , and l o c a l l y e x c i t e d states. F u r t h e r s t u d i e s on t h e photo-Smiles r e a c t i o n and r e l a t e d p r o c e s s e s of 6 - ( n i t r o p h e n o x y ) e t h y l a m i n e s (100) by Wubbels a n d c o - w o r k e r s i l l u s t r a t e t h a t t h e r e a r r a n g e m e n t i s m a r k e d l y i n f l u e n c e d by t h e r e l a t i v e p o s i t i o n s of t h e s u b ~ t i t u e n t s . ~ The ~ Smiles r e a c t i o n t o g i v e W( nitrophenyl)-2-aminoethanols ( 1 0 1 ) i s o b s e r v e d f o r t h e 2a n d m_-isomers t h e r m a l l y and o n l y t h e 2-isomer u n d e r g o e s r e a r r a n g e ment p h o t o c h e m i c a l l y . I r r a d i a t i o n of t h e 2- a n d m-isomers a s h y d r o c h l o r i d e s y i e l d s ( 1 0 2 ) a n d ( 1 0 3 ) , a n d (104), ( 1 0 5 ) , a n d ( 1 0 6 ) r e s p e c t i v e l y w h i c h shows t h a t t h e 6-amino g r o u p i n b o t h cases b o n d s a t t h e r i n g C-atom a d j a c e n t t o t h e s i d e c h a i n a n d meta t o t h e n i t r o group. These r e s u l t s c o n t r a s t s h a r p l y with t h o s e 8 o b t a i n e d when t h e -NHPh m o i e t y i s t h e a t t a c k i n g n u c l e o p h i l e . P h o t o n u c l e o p h i l i c s u b s t i t u t i o n o f f l u o r o - and c h l o r o - a n i s o l e s h a s been t h e s u b j e c t o f t h r e e r e p o r t s w i t h i n t h e y e a r . C o r n e l i s s e a n d co-workers h a v e s t u d i e d t h e p h o t o c y a n a t i o n a n d p h o t o h y d r o l y s i s of 4 - f l u o r o - a n d c h l o r o - a n i s o l e s by l a s e r s p e c t r o s c o p y a n d r e p o r t t h a t t h e i n i t i a l s t e p of t h e r e a c t i o n involves formation of a t r i p l e t s t a t e t r a n s i e n t complex composed o f a g r o u n d s t a t e a n d a n e x c i t e d s t a t e aromatic m o l e c u l e . 6 5 Only i n t h e p r e s e n c e of

water d o e s t h e complex y i e l d r a d i c a l i o n s a n d i t is t h i s p r o c e s s which d e t e r m i n e s t h e p r o d u c t quantum y i e l d . The r a d i c a l c a t i o n t h e n reacts w i t h t h e n u c l e o p h i l e t o g i v e a n e u t r a l r a d i c a l which y i e l d s t h e s u b s t i t u t e d a r e n e i n a s i n g l e s t e p . L i u a n d Weiss r e p o r t o n anomalous e f f e c t s d u r i n g p h o t o n u c l e o p h i l i c aromatic s u b s t i t u t i o n o f 2- a n d 4 - f l u o r o a n i s o l e s a n d a l s o on t h e p h o t o -

Photochemistry

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h y d r o x y l a t i o n , photobyanation and f l u o r e s c e n c e quenching o f t h e 2 - i s o m e r c o m p l e x e d w i t h c y c l ~ d e x t r i n s . 67 ~ ~ ’In the f i r s t study t h e r e a c t i o n s are i n s o l v e n t m i x t u r e s o f water a n d t - b u t a n o l a n d t h e rate c o n s t a n t r a t i o f o r s u b s t i t u t i o n o f t h e f l u o r i n e b y CN- a n d OH- i s o b s e r v e d t o b e r e m a r k a b l y d e p e n d e n t on t h e c o m p o s i t i o n o f t h e s o l v e n t and on t h e s i t e of r e a c t i o n r e l a t i v e t o t h e methoxy g r o u p . T h u s , f o r e x a m p l e , t h e r a t i o o f 2 - h y d r o x y a n i s o l e t o 2 - c y a n o a n i s o l e from t h e 2 - f l u o r o isomer v a r i e s r e s p e c t i v e l y f r o m 2 . 4 4 : l t o 0 . 6 4 : l a s t h e t - b u t a n o l t o water r a t i o c h a n g e s f r o m 1 : 5 t o 3 : l a n d f o r t h e 4 - f l u o r o isomer t h e c o r r e s p o n d i n g h y d r o x y a n d c y a n o p r o d u c t s are formed i n 0 . 0 6 1 : l a n d 0.018:l r a t i o s w i t h r e s p e c t i v e m i x t u r e s o f t - b u t a n o l a n d water o f 1 : 3 a n d 2 : l . The authors report t h a t t h e i r preliminary s t u d i e s with other alcoholwater m i x t u r e s s u p p o r t t h e g e n e r a l i t y o f t h e s e o b s e r v a t i o n s a n d t h e y p o i n t o u t t h a t a f u l l e x p l a n a t i o n o f t h e s e e f f e c t s must i n c l u d e t h e dynamic i n f l u e n c e o f t h e s o l v e n t s t r u c t u r e on b o t h t h e n u c l e o p h i l e a n d s u b s t r a t e . Complexing o f 4 - f l u o r o a n i s o l e w i t h a- a n d B - c y c l o d e x t r i n s t r o n g l y i n h i b i t s p h o t o c y a n a t i o n a n d p h o t o h y d r o x y l a t i o n p r o c e s s e s b u t t h e r e i s v i r t u a l l y no e f f e c t w i t h y-cyclodextrin. The p h o t o s u b s t i t u t i o n o f t h e 2 - f l u o r o i s o m e r h a s been s t u d i e d and it i s r e p o r t e d t h a t with a - c y c l o d e x t r i n b o t h t h e r e a c t i o n s of water a n d CN- w i t h t h e a r e n e a r e s t r o n g l y i n h i b i t e d b u t t h a t s u r p r i s i n g l y t h e 0-cyclodextrin r e t a r d s t h e photohydroxyl67 a t i o n t o a f a r g r e a t e r e x t e n t t h a n it d o e s t h e c y a n a t i o n p r o c e s s . The p h o t o r e a c t i o n s o f f l u o r o - 6 8 a n d r n e t h o ~ y - ~ ’b e n z e n e s i n t h e p r e s e n c e o f amines had been e a r l i e r d e s c r i b e d b u t t h e s e s u b s t i t u t i o n and a d d i t i o n p r o c e s s e s have been re-examined w i t h d i e t h y l a m i n e as t h e n u c l e o p h i l e i n o r d e r t o i n v e s t i g a t e f u r t h e r t h e mechanism i n v o l v e d . 7 0 The e a r l i e r p r o p o s a l s are s u b s t a n t i a t e d b y t h e l a t e r s t u d y a n d a mechanism i n which t h e S1 a r e n e is q u e n c h e d by t h e amine t o g i v e a n e x c i p l e x i s o u t l i n e d . P r o t o n t r a n s f e r w i t h i n t h e e x c i p l e x and combination o f r a d i c a l s l e a d s t o t h e a c y c l i c a d d i t i o n p r o d u c t s some o f w h i c h u n d e r g o e l i m i n a t i o n o f HF o r m e t h a n o l t o yield the substituted arenes. The p h o t o - i n d u c e d s u b s t i t u t i o n o f t h e methoxy g r o u p of 3n i t r o a n i s o l e a n d o f 3 , 5 - d i n i t r o a n i s o l e s by OH- h a s p r e v i o u s l y b e e n s t u d i e d u n d e r s t e a d y s t a t e condition^,^^ a n d h a s now been 72 i n v e s t i g a t e d by nanosecond t i m e r e s o l v e d a b s o r p t i o n s p e c t r o s c o p y . The s p e c t r a o b t a i n e d i m m e d i a t e l y f o l l o w i n g t h e d i s a p p e a r a n c e o f t h e t r i p l e t s t a t e of t h e n i t r o a n i s o l e showed t h a t f o r m a t i o n o f t h e s u b s t i t u t i o n p r o d u c t i s complete a t t h a t p o i n t and from t h e s e

Photochemistry

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(114)

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IIIl4: Photochemistry of Aromatic Compounds r e s u l t s i t is c o n c l u d e d t h a t t h e a d d i t i o n o f t h e OH- a t C-1 t h e rate determining s t e p .

is

There i s a l s o a t least one f u r t h e r

r e a c t i o n o f t h e n u c l e o p h i l e w i t h t h e t r i D l e t a r e n e a n d t h i s comp e t e s w i t h t h e a t t a c k a t C - 1 a n d lowers t h e quantum y i e l d o f substi-tution.

The p r o d u c t o f t h i s s i d e r e a c t i o n is a l o n g - l i v e d

s p e c i e s w i t h a n a b s o r p t i o n maximum a t 370 nm.

Marquet a n d c o -

workers have pursued t h e i r i n t e r e s t i n t h e u s e of t h e photon u c l e o p h i l i c a r o m a t i c s u b s t i t u t i o n i n p h o t o a f f i n i t y l a b e l l i n g and r e p o r t a model s t u d y a n d t h e r e a c t i o n o f a c y c l o h e x i m i d e d e r i v a t i v e . 73

From r e s u l t s of 4 - n i t r o c a t e c h o l

e t h e r s (107) with methyl-

a m i n e i t is shown t h a t t h e s u b s t i t u t i o n o c c u r s a t t h e p o s i t i o n

meta t o t h e n i t r o g r o u p a n d so i r r a d i a t i o n o f t h e ester (108) o f t h e i m i d e ( 1 0 9 ) which is a n a n t i b i o t i c o f t h e g l u t a r i m i d e f a m i l y , i n t h e p r e s e n c e of t h e amine y i e l d s ( 1 1 0 ) . The a u t h o r s p o i n t o u t t h a t t h e c o n v e r s i o n o f (108) t o ( 1 1 0 ) i l l u s t r a t e s t h e p o t e n t i a l o f nitrophenyl esters as p h o t o a f f i n i t y probes t o i d e n t i f y b i o l o g i c a l receptor sites. The p h o t o r e a c t i o n s o f d i c y a n o b e n z e n e s w i t h a l l y l s i l a n e s which y i e l d a l l y l a t e d benzenes74 h a s been e x t e n d e d t o dicyano n a p h t h a l e n e s , a n t h r a c e n e s , a n d p h e n a n t h r e n e s . 75 I r r a d i a t i o n s o f t h e a r e n e s a n d a l l y l t r i m e t h y l s i l a n e are c a r r i e d o u t i n a c e t o n i t r i l e w i t h wavel e n g t h s l o n g e r t h a n 290 nm a n d w i t h 1 , 4 - d i c y a n o n a p h t h a l e n e , f o r e x a m p l e , as w e l l a s t h e e x p e c t e d s u b s t i t u t i o n p r o d u c t t w o a d d u c t s ( 1 1 2 ) a n d ( 1 1 3 ) a r e formed:

(111) t h e

as p r e v i o u s l y t h e r e a c t i o n

is c o n s i d e r e d t o p r o c e e d b y e l e c t r o n t r a n s f e r t o t h e a r e n e f r o m t h e silane. S i m i l a r d i c y a n o a r e n e s on i r r a d i a t i o n i n t h e p r e s e n c e o f a l k y l t r i p h e n y l b o r a t e s a l t s g i v e a l k y l s u b s t i t u t e d p r o d u c t s . 76 The b o r a t e s a l t s are c o n s i d e r e d a s a new c l a s s o f p h o t o - o x i d i z a b l e r e a g e n t s which e n a b l e f a c i l e a l k y l t r a n s f e r t o an e l e c t r o n a c c e p t o r t o o c c u r a n d y i e l d s c a n b e e x t r e m e l y good. Thus i r r a d i a t i o n of i n t h e p r e s e n c e o f Me4N+CMeR(Ph) 3 1- i n a c e t o n i t r i l e s o l u t i o n g i v e s 100% o f a m i x t u r e o f 3- a n d 4-methyl-11,4-dicyanonaphthalene

cyanonaphthalenes i n a ratio o f 1 . 4 : l . The r e a c t i o n i s c o n s i d e r e d t o p r o c e e d b y e l e c t r o n t r a n s f e r f r o m t h e b o r a t e s a l t t o t h e S1 a r e n e t o g i v e t h e s p e c i e s ( 1 1 4 ) . Cleavage of t h e boron r a d i c a l produces t r i p h e n y l b o r o n a n d 'CH3 w h i c h t h e n c o m b i n e s w i t h t h e a r e n e r a d i c a l a n i o n t o y i e l d ( 1 1 5 ) a n d (116 ) P r o t o n a t i o n and dehydrocyanat i o n of t h e latter i n t e r m e d i a t e s produces t h e methyl s u b s t i t u t e d arenes. I t w a s r e p o r t e d i n 1 9 8 2 by J a p a n e s e w o r k e r s t h a t i r r a d i a t i o n o f b i p h e n y l a b s o r b e d o n s i l i c a g e l i n t h e p r e s e n c e of s o d i u m n i t r a t e s o l u t i o n produced t h e h y d r o x y l a t e d and n i t r a t e d p r o d u c t s

.

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(117), (118), and ( I I ~ ) . Runce ~ ~ and co-workers have rei n v e s t i g a t e d t h e p r o c e s s m o s t l y u n d e r homogeneous c o n d i t i o n s i n aqueous m e t h a n o l w i t h t h e o b j e c t i v e of d e t e r m i n i n g t h e mechanism of t h e s u b s t i t u t i o n p r o c e s s e s and r e p o r t t h a t t h e i n i t i a l p r o d u c t s are 0- and p - h y d r o x y b i p h e n y l s which t h e n undergo p h o t o n i t r a t i o n . 78 The p r i m a r y s t e p i s NO; q u e n c h i n g o f t h e b i p h e n y l S1 s t a t e t o g i v e a n e x c i p l e x o r a caged r a d i c a l i o n p a i r w h i c h c o l l a p s e s t o t h e hydroxy compounds. T h r e e r e p o r t s which a p p e a r e d w i t h i n t h e year on t h e p h o t o s u b s t i t u t i o n p r o c e s s e s of hydroxy a r e n e s i l l u s t r a t e a l o n g w i t h t h e a c c o u n t s i n r e f e r e n c e s 10-12 t h e d i v e r s e p h o t o c h e m i c a l i n t e r e s t s i n these s u b s t r a t e s . The p h o t o f o r m y l a t i o n o f a number of p h e n o l s h a v e been d e s c r i b e d , 7 g and i t i s r e p o r t e d t h a t i r r a d i a t i o n o f a 5,l0,15,20-tetraphenylporphyrin-~-~nzoquinone-4-methoxyphenol In the latter s y s t e m l e a d s t o t h e s u b s t i t u t i o n p r o d u c t (120).80 r e a c t i o n t h e e f f i c i e n c y of t h e p r o c e s s i s dependent on t h e concent r a t i o n a n d r e d u c t i o n p o t e n t i a l of t h e q u i n o n e employed and from ESR a n d CIDNP e x p e r i m e n t s t h e mechanism is s u g g e s t e d t o i n v o l v e r a d i c a l c o u p l i n g . I r r a d i a t i o n of 4-phenylazo-l-naphthol (121) i s r e p o r t e d to i n d u c e p h o t o - o x i d a t i v e d i m e r i z a t i o n t o g i v e (122) and t h e r e a c t i o n i s most e f f i c i e n t i n s o l v e n t s w h i c h f a v o u r t h e f o r m a t i o n o f t h e h y d r a z o n e r a t h e r t h a n t h e a z o form o f (121). 81 The i n v o l v e m e n t of k e t o - e n o l t a u t o m e r i s m i n t h e p r o c e s s is s u p p o r t e d by t h e o b s e r v a t i o n t h a t t h e methoxy compound (123) is i n e r t under t h e present conditions. P h o t o s u b s t i t u t i o n r e a c t i o n s of 9,lO-anthraquinones c o n t i n u e t o a t t r a c t i n t e r e s t and t h e s e l e c t i v e p h o t o h y d r o x y l a t i o n and p h o t o a l k y l a m i n a t i o n o f t h e amino d e r i v a t i v e s h a s been d e s c r i b e d . 82 I r r a d i a t i o n o f ( 1 2 4 ) i n t h e p r e s e n c e of t - b u t y l a m i n e w i t h oxygen b u b b l e d t h r o u g h t h e b e n z e n e - e t h a n o l s o l u t i o n g i v e s a 79% y i e l d o f t h e hydroxy compound (125) whereas s i m i l a r t r e a t m e n t of t h e Na c y l a t e d d e r i v a t i v e (126) g i v e s t h e a m i n a t e d compound (127). T h e s e d i f f e r e n c e s are s u g g e s t e d t o r e s u l t from a change i n t h e e n e r g y l e v e l s i n t h e e x c i t e d s t a t e s of t h e two s t a r t i n g materials. As f o r a v e r y wide r a n g e o f a r y l h a l i d e s (see below) l - c h l o r o a n t h r a q u i n o n e s u n d e r g o p h o t o d e c h l o r i n a t i o n r e a c t i o n s . 83 Thus 366 nm i r r a d i a t i o n o f 1,5-dichloroanthraquinone f o r example y i e l d s a n t h r a q u i n o n e via a number of photo-induced s t e p s which i n v o l v e f o r m a t i o n of t h e chloroanthrahydroquinones and t h e i r p h o t o c o n v e r s i o n t o t h e d e c h l o r i n a t e d q u i n o n e . D u r i n g t h e i n v e s t i g a t i o n of t h i s

2 98

Photochemistry

process it w a s observed t h a t i r r a d i a t i o n of t h e c h l o r i n a t e d q u i n o n e s g a v e a s p e c i e s which i n a d a r k r e a c t i o n p r o d u c e d t h e hydroquinone and t h e s t a r t i n g quinone s i m u l t a n e o u s l y . T h i s i n t e r m e d i a t e i s a s s i g n e d t o a complex o f t w o c h l o r i n a t e d a n t h r a s e m i quinone r a d i c a l s . I t is a l s o of i n t e r e s t t o n o t e t h a t although i r r a d i a t i o n of 2-chloroanthraquinone y i e l d s the 2-chloroanthrah y d r o q u i n o n e , h e r e t h e r e a c t i o n s t o p s a n d no c o n v e r s i o n t o t h e d e c h l o r i n a t e d quinone is observed. Photodimerizations of a n t h r a c e n e s (see S e c t i o n 5 ) is n o r m a l l y a v e r y f a c i l e r e a c t i o n b u t i n t h e case o f t h e 9 - t r i m e t h y l s i l y l d e r i v a t i v e t h i s p r o c e s s i s r e p o r t e d t o be n e g l i g i b l e and i r r a d i a t i o n of methanol s o l u t i o n s r e s u l t s i n ~ ~ substid e s i l y l a t i o n a n d t h e f o r m a t i o n o f t h e p a r e n t a r e r ~ e . The t i o n is g r e a t l y e n h a n c e d i n t h e p r e s e n c e o f CC13CH20H a n d i n h i b i t e d i n t-butanol: t h e s e o b s e r v a t i o n s are r a t i o n a l i z e d i n terms of a n H-bonding i n t e r a c t i o n i n t h e e x c i t e d s t a t e r e s u l t i n g from i n t r a m o l e c u l a r c h a r g e - t r a n s f e r i n t h e e x c i t e d s i n g l e t state o f t h e s t a r t i n g material. Again t h i s y e a r t h e r e have been s e v e r a l a c c o u n t s o f p h o t o d e c h l o r i n a t i o n of a v a r i e t y o f a r o m a t i c s u b s t r a t e s . The l a s e r f l a s h p h o t o l y s i s o f chlorobenzene i n p o l a r s o l v e n t s h a s been d i s c u s s e d i n terms o f a s i n g l e t s t a t e s u b s t i t u t i o n r e a c t i o n w i t h a r a d i c a l c a t i o n i n t e r m e d i a t e a n d a s i n g l e t and t r i p l e t h o m o l y t i c C-C1 c l e a v a g e p r o c e s s . 85 T e t r a c h l o r o b e n z e n e s i n a c e t o n i t r i l e water m i x t u r e s u n d e r g o p h o t o - i n d u c e d r e d u c t i v e d e c h l o r i n a t i o n a s t h e p r i n c i p a l r e a c t i o n f r o m b o t h d i r e c t and s e n s i t i z e d i r r a d i a t i o n s , 86 a n d t e t r a - a n d p e n t a - c h l o r o p h e n o l s react s i m i l a r l y b u t i n t h e l a t t e r s e r i e s p r o d u c t s o f m o l e c u l a r f o r m u l a C8H4C13N0 a n d C8H3C14N0 r e s p e c t i v e l y are a l s o f o r m e d . 87 F u r t h e r , t h e i r r a d i a t i o n o f 2,3,5,6-tetrachlorophenol l e a d s t o t h e f o r m a t i o n o f h e x a - , h e p t a - , a n d octa-chlorodihydroxybiphenyls as w e l l a s t h e r e d u c t i o n a n d a d d i t i o n compounds a n d s u c h r e a c t i o n i s u n i q u e t o t h i s p h e n o l . P h o t o d e h a l o g e n a t i o n of c h l o r o b i p h e n y l h a s f o r a number o f y e a r s been o f i n t e r e s t and c o n c e r n l a r g e l y f o r e n v i r o n m e n t a l r e a s o n s . E p l i n g a n d F l o r i o now r e p o r t t h a t t h e d e c h l o r i n a t i o n of t h e s e s u b s t r a t e s 8 8 a n d o f c h l o r o t o l ~ e n e si ~n ~9 : 1 a c e t o n i t r i l e : water s o l u t i o n s is e n h a n c e d by 1 4 - f o l d i n t h e p r e s e n c e o f s o d i u m b o r o h y d r i d e a n d t h a t t h e r a t e o f r e a c t i o n is g r e a t e r by a f a c t o r o f 33 i n m i c e l l a r s o l u t i o n s . T h e s e workers d e d u c e t h a t a f r e e r a d i c a l mechanism d o e s n o t o p e r a t e f o r e i t h e r series of compounds b u t from o t h e r s t u d i e s i t i s s u g g e s t e d t h a t t h e p h o t o d e h a l o g e n a t i o n o f c h l o r i n a t e d p h e n o l s may i n v o l v e a r y l r a d i c a l a n d a r y l c a r b e n e /

M l 4 : Photochemistry of Aromatic Compounds a r y l cation intermediates.

299

The l a t t e r s t u d y h a s b e e n e x t e n d e d

t o a c o n s i d e r a t i o n o f p o l y c h l o r i n a t e d diphenyl e t h e r s and c h l o r o a n i s o l e s a n d a g a i n t h e r e d u c t i o n i s p r o p o s e d t o p r o c e e d via a r y l radicals: i n t e r m e d i a t e s i n t h e photohydrolysis of t h e a n i s o l e s and diphenyl e t h e r s are r e p o r t e d t o be a r y l c a r b e n e s / a r y l c a t i o n s . The p h o t o h y d r o l y s i s of 2 - c h l o r o - 4 - n i

t r o d i p h e n y l e t h e r h a s been

s t u d i e d by R u s s i a n w o r k e r s who n o t e t h a t t h e r e is a l i n e a r r e l a t i o n s h i p b e t w e e n t h e r e c i p r o c a l o f t h e quantum y i e l d a n d b a s e c o n c e n t r a t i o n , a n d t h a t t h e r e a c t i v i t y of t h e e x c i t e d s t a t e correlates w i t h t h e change i n e l e c t r o n d e n s i t y r e s u l t i n g from p h o t o e x ~ i t a t i o n . ~As~ may be e x p e c t e d , t h e e f f i c i e n c y o f p h o t o d e h a l o g e n a t i o n v a r i e s w i t h t h e h a l o g e n s a n d o t h e r p r o c e s s e s may compete.

T h u s i r r a d i a t i o n o f 2-(4-halophenyl)benzoxazoles (128) a t 300 nm i n o x y g e n - f r e e h e x a n e s o l u t i o n r e s u l t s i n d e h a l o g e n a t i o n f o r X = B r a n d I,2.rr+21~h e a d - t o - t a i l d i m e r i z a t i o n f o r X = F , I t is r e p o r t e d t h a t and b o t h p r o c e s s e s a r e observed f o r X = C l . 9 3 t h e d e h a l o g e n a t i o n f o r t h e c h l o r o compound is a s i n g l e t s t a t e

process involving an excimer.

The r e a c t i o n i s c o n s i d e r a b l y

enhanced i n t h e p r e s e n c e o f t h e e l e c t r o n donors,*-piperylene and t r i e t h y l a m i n e , and i n s u c h c i r c u m s t a n c e s p r o c e e d s an T h e p ho t o d e c h l o r i n a t i o n

e x c i t e d s t a t e c h a r g e -t r a n s f e r c o m p l e x ,

p r o d u c t (129) i s o b s e r v e d i n t h e r e a c t i o n m i x t u r e o b t a i n e d from i r r a d i a t i o n o f v i n c l o z o l i n (130) i n methanol but i n benzene s o l u t i o n (130) g i v e s mainly t h e biphenylyloxazolidine

(131).

94

Such p h o t o c o u p l i n g r e a c t i o n s a r e a l s o o b s e r v e d on i r r a d i a t i o n o f 5-bromo-1, 3 - d i m e t h y l u r a c i l g 5 benzenes.

o r 2 - i o d 0 p y r i d i n e ~ ~i n s u b s t i t u t e d

I n t h e f o r m e r case b o t h isomers ( 1 3 2 ) a n d ( 1 3 3 ) are

formed i n a r e s p e c t i v e r a t i o o f approximately 7 : l b u t t h e r e a c t i o n

i s o n l y r e p o r t e d f o r methyl benzenes and a n i s o l e . In contrast a c o u p l i n g r e a c t i o n w i t h t h e p y r i d i n e t o g i v e 2 - a r y l p y r i d i n e s is o b s e r v e d f o r a wide v a r i e t y o f s u b s t i t u t e d benzenes, and A n t o n i o l e t t i and co-workers r e p o r t t h a t t h e photocoupling p r o c e s s o f bromofuran-2-carbaldehyde a n d k e t o n e s w i t h a r e n e s p r o v i d e s good 97,98 derivatives. y i e l d s (60-70%) o f 3- a n d 5 - a r y l - 2 - f u r y 1 Work c o n t i n u e s o n t h e f a c t o r s which c a n a f f e c t t h e p h o t o m e t h o x y l a t i o n of e s t e r s o f p y r i d i n e c a r b o x y l i c a c i d s i n a c i d i c methanol s o l u t i o n s and a remarkable e f f e c t o f atmosphere h a s been r e p o r t e d . 99 Under o x y g e n , m e t h o x y l a t i o n o f , f o r e x a m p l e , (134 ) o c c u r s a t b o t h t h e a - a n d @ - p o s i t i o n s i n a r e s p e c t i v e r a t i o o f 3:s but i n nitrogen degassed s o l u t i o n s ,

substitution occurs specific-

Photochemistry

300 CONH,

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301

a l l y a t t h e a-site and i n v o l v e s b o t h methoxylation and m e t h y l a t i o n t o g i v e ( 1 3 5 ) a n d ( 1 3 6 ) i n a 11:l r a t i o r e s p e c t i v e l y .

I t is

suggested t h a t under t h e former c o n d i t i o n s t h e r e a c t i o n proceeds by way o f a t e r p l e x o f two m o l e c u l e s o f t h e p r o t o n a t e d d i e s t e r a n d o n e m o l e c u l e o f oxygen w h i l e u n d e r n i t r o g e n t h e p r o d u c t arises d i r e c t l y from t h e a r e n e e x c i m e r .

The same g r o u p o f w o r k e r s have

e x t e n d e d t h e i r s t u d i e s i n t h i s area t o a n e x a m i n a t i o n o f t h e photoreactions of 3-pyridine

carboxamide i n a c i d i c methanol and

a g a i n r e a c t i o n s o f m e t h o x y l a t i o n a n d m e t h y l a t i o n are r e p o r t e d ( s e e Scheme 2 ) . l o o The e f f e c t s o f q u e n c h e r s o n t h e p r o c e s s a r e s u g g e s t e d t o i n d i c a t e t h a t t h e m e t h y l a t i o n o r i g i n a t e s from o n e e x c i t e d t r i p -

l e t s t a t e a n d t h a t t h e m e t h o x y l a t i o n a r i s e s from t w o d i f f e r e n t e x c i t e d s i n g l e t s t a t e s which are q u e n c h e d by a n e l e c t r o n t r a n s f e r P h o t o s u b s t i t u t i o n o f t h e p y r i d i n e a-position also

mechanism.

o c c u r s o n i r r a d i a t i o n o f 4-benzoyl-~-ethoxycarbonylimino~yridinium

s a l t s ( 1 3 7 ) i n t h e p r e s e n c e o f a l k e n e s . lo'

Thus ( 1 3 7 ) a n d c y c l o -

hexene y i e l d t h e e r y t h r o adduct (138) and s m a l l amounts o f 4b e n z o y l p y r i d i n e , and from trans-hex-3-ene

b o t h t h e t h r e o and

e r y t h r o p r o d u c t s ( 1 3 9 ) are formed i n a r e s p e c t i v e r a t i o o f 5:l. The e f f i c i e n c y o f t h e p r o c e s s is o b s e r v e d t o be o p t i m i s e d i n t h e p r e s e n c e o f c h l o r o f o r m a n d a m u l t i s t e p b i r a d i c a l mechanism i s proposed.

F u r t h e r d e t a i l s have been p u b l i s h e d o f t h e p h o t o -

i n d u c e d f u n c t i o n a l i z e d C - a l k y l a t i o n s i n p u r i n e s y s t e m s . lo2 The r e a c t i o n i n v o l v e s i r r a d i a t i o n o f , f o r example, t h e potassium e n o l a t e o f a c e t o n e i n ammonia s o l u t i o n w i t h 6 - i o d o - 9 - e t h y l p u r i n e ( 1 4 0 ) which g i v e s a f t e r c h r o m a t o g r a p h i c s e p a r a t i o n 70% o f 6acetonyl-9-ethylpurine

(141).

Each y e a r r e p o r t s are p u b l i s h e d which d e s c r i b e p h o t o - i n d u c e d changes within an arene s u b s t i t u e n t .

Examples o f s u c h p r o c e s s e s

which may n o t be c o n v e n i e n t l y c o n s i d e r e d e l s e w h e r e i n t h i s Volume are b r i e f l y m e n t i o n e d h e r e t o i l l u s t r a t e t h e t y p e o f r e s e a r c h currently of i n t e r e s t .

Hexamethylbenzene a n d m e r c u r i c t r i f l u o r o -

a c e t a t e form a g r o u n d s t a t e complex which e x h i b i t s c h a r g e - t r a n s f e r a b s o r p t i o n a n d i r r a d i a t i o n w i t h i n t h i s band y i e l d s p e n t a m e t h y l benzyl t r i f l u o r o a c e t a t e . The same p r o d u c t is o b t a i n e d from i r r a d i a t i o n o f t h e complex i n b o t h d i c h l o r o m e t h a n e a n d t r i f l u o r o -

acetic a c i d s o l u t i o n s . A r n o l d and c o - w o r k e r s h a v e s t u d i e d t h e h o m o l y t i c v e r s u s h e t e r o l y t i c c l e a v a g e f o r a wide v a r i e t y o f l-naphthylmethyl d e r i v a t i v e s (142) i n methanol s o l u t i o n F o r R=C1, Rr, SMei, under d i r e c t and s e n s i t i s e d c o n d i t i o n s .

photo-induced

Photochemistry

302

* Q (yCH & CH20Ac

QCH20H

Me (143)

\

+

Me

/

(1 4 4 )

(145)

X

0 ( 1 4 9 ) R = CHZOH (150)R = H

(147) R = H ( 1 4 8 ) R = Me

(146)

WPh (154) A l l rings aromatic

R (153) R = B r (156) R = H

5 \' \ 0

(155) R = Br (157) R = H

IIIt4: Photochemistry of Aromatic Compounds

3 03

B F i , a n d SO 2Me i n ( 1 4 2 ) , t h e c l e a v a g e i s s e n s i t i z e d by x a n t h o n e b u t e v i d e n c e i s p r e s e n t e d which i n d i c a t e s t h a t f o r t h e f o r m e r f o u r compounds e x c i p l e x f o r m a t i o n occurs r a t h e r t h a n t r i p l e t e n e r g y A u s e f u l semi q u a n t i t a t i v e scale o f p h o t o f u g a c i t i e s o f transfer. t h e s u b s t i t u e n t groups i n t h e e x c i t e d s i n g l e t state is given. W i t h i n t h e r e v i e w p e r i o d Wan a n d c o - w o r k e r s h a v e d e s c r i b e d t h e g e n e r a t i o n and subsequent r e a c t i o n s o f charged s p e c i e s from i r r a d i From p h o t o s o l v o l y s i s a t i o n of v a r i o u s aromatic compounds. '05-'07 a n d M e ) i n n e u t r a l and a c i d i c s t u d i e s o f m- a n d E-RC~H~CH~OH(R=F media it h a s b e e n shown t h a t t h e m-isomers react p r e d o m i n a n t l y by a h e t e r o l y t i c r o u t e c a t a l y s e d by H30+ t o y i e l d t h e b e n z y l cat i o n s . I n c o n t r a s t t h e p - i s o m e r s react more s l o w l y a n d i n v o l v e r a d i c a l i n t e r m e d i a t e s and t h e s e d i f f e r e n c e s are a s s i g n e d t o t h e a b i l i t i e s of t h e R - s u b s t i t u e n t s t o s t a b i l i s e t h e p o s i t i v e charge developing at t h e benzylic p o s i t i o n of t h e s i n g l e t e x c i t e d s t a t e o f t h e a r e n e . The p r o d u c t s f r o m (143), for e x a m p l e , are ( 1 4 4 ) a n d ( 1 4 5 ) i n t h e p r e s e n c e o f a c e t i c a c i d . The p h o t o r e a c t i o n s o f 9-phenyl-xanthen-9-01 ( 1 4 6 ) have been s t u d i e d i n some d e t a i l and evidence h a s been p r e s e n t e d t h a t t h e a r e n e undergoes a d i a b a t i c p h o t o d e h y d r o x y l a t i o n i n a q u e o u s s o l u t i o n : t h i s f i r s t example o f a new c l a s s of a d i a b a t i c p h o t o r e a c t i o n d o e s n o t o c c u r i n aceton i t r i l e or 95% e t h a n o l s o l u t i o n . From a s t u d y o f r e l a t e d s y s t e m s , a g e n e r a l method h a s been d e s c r i b e d f o r a s s e s s i n g t h e r e l a t i v e s t a b i l i t y of d i b e n z o y l a t e d c a t i o n i c and a n i o n i c s p e c i e s as 107 a f u n c t i o n of t h e number o f n - e l e c t r o n s i n t h e e x c i t e d s t a t e . From i r r a d i a t i o n of ( 1 4 7 ) i n w a t e r - m e t h a n o l s o l u t i o n t h e methoxy d e r i v a t i v e (148) r e s u l t s a n d t h e a n i o n p r o d u c e d from ( 1 4 9 ) g i v e s (150). 4 Intramolecular Cyclization Reactions T h i s S e c t i o n i s concerned w i t h photo-induced c y c l i z a t i o n r e a c t i o n s o f aromatic compounds i n which t h e f i n a l p r o d u c t i s a l s o a n a r e n e . Examples of i n t r a m o l e c u l a r c y c l i z a t i o n i n w h i c h t h e p r o d u c t i s a s t a b l e a l i p h a t i c s y s t e m (e.g. i n t r a m o l e c u l a r meta p h o t o c y c l o a d d i t i o n o f e t h y l e n e s t o b e n z e n e s ) are c o n s i d e r e d i n S e c t i o n 3 o f t h i s C h a p t e r . The p r e s e n t t y p e o f p r o c e s s o c c u r s f o r a w i d e v a r i e t y o f s y s t e m s and may i n v o l v e a r e n e - a r e n e a n d a r e n e e t h y l e n e p h o t o - o x i d a t i v e c y c l i z a t i o n o r r e a c t i o n s p r o c e e d i n g by l o s s o f h a l o g e n a c i d . F o r s e v e r a l y e a r s now o n e o f t h e major i n t e r e s t s i n t h e s e p r o c e s s e s h a s been i n t h e i r u s e a s s y n t h e t i c p r o c e d u r e s a n d a g a i n w i t h i n t h e r e v i e w p e r i o d there h a v e a p p e a r e d a number o f a c c o u n t s which i l l u s t r a t e t h i s f e a t u r e . S t i l b e n e -

Photochemistry

304

(1 6 0 )

(159)

Br

OMe

Ph

eo (162)

R' R

'(161) X = C I or Br R's = H, Me, OMe and -0-CH2-O-

M e 0 +OAC

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305

p h e n a n t h r e n e c y c l i z a t i o n s h a v e been o f p a r t i c u l a r u s e i n t h i s r e s p e c t a n d Hopf a n d c o - w o r k e r s

h a v e s u c c e s s f u l l y employed t h e

r e a c t i o n a s a new method f o r t h e s y n t h e s i s o f c o n d e n s e d C2.21 p a r a c y c l o p h a n e s . lo8 T h u s i r r a d i a t i o n o f t h e s t i l b e n e ( 1 5 1 ) i n h e x a n e s o l u t i o n i n t h e p r e s e n c e o f i o d i n e a n d a i r p r o d u c e s t h e C2.21

(1,4)phenanthrenoparacyclophane ( 1 5 2 ) i n 31% y i e l d . T h i s type o f c y c l i z a t i o n h a s p r e v i o u s l y been e x p l o i t e d f o r t h e s y n t h e s i s o f h e l i c e n e s 8 a n d by t h e u s e o f b r o m i n e as a d i r e c t i v e s u b s t i t u e n t 1 09 S u d h a k a r a n d K a t z h a v e d e v i s e d a n i m p r o v e d r o u t e t o C71 h e l i c e n e . The b r o m i n e atom i s f o u n d t o d i r e c t t h e s t i l b e n e c y c l i z a t i o n away f r o m o c c u p i e d p o s i t i o n s a n d t h o s e o r t h o t o t h e s u b s t i t u e n t so t h a t w i t h ( 1 5 3 ) t h e bromo C77 h e l i c e n e ( 1 5 4 ) i s f o r m e d i n 75% y i e l d o n i r r a d i a t i o n o f benzene s o l u t i o n s c o n t a i n i n g i o d i n e , and less t h a n 1 0 % o f t h e p l a n a r a r e n e ( 1 5 5 ) i s o b s e r v e d . S u c h r e s u l t s compare v e r y f a v o u r a b l y w i t h t h o s e from i r r a d i a t i o n o f t h e hydrocarbon ( 1 5 6 ) when e q u a l q u a n t i t i e s o f t h e C71 h e l i c e n e a n d ( 1 5 7 ) are f o r m e d . 'lo

I r r a d i a t i o n o f ( 1 5 8 ) , t h e meta isomer o f ( 1 5 6 ) ,

c y c l i z e s s e l e c t i v e l y w i t h o u t bromine d i r e c t i o n and (159) is formed 111 i n 75% f r o m x y l e n e s o l u t i o n i n t h e p r e s e n c e o f oxygen a n d i o d i n e . The o r i g i n s o f t h i s s e l e c t i v i t y may n o t b e r e a d i l y e v i d e n t a n d it

i s d i f f i c u l t t o a p p r e c i a t e why o f t h e f o u r p o s s i b l e c o n f o r m e r s o f the f i r s t intramolecular

photo-oxidative cyclization product only (160)

undergoes f u r t h e r r e a c t i o n .

The a u t h o r s s u g g e s t t h a t t h i s f e a t u r e

r e f l e c t s t h a t o f t h e f o u r c o n f o r m e r s ( 1 6 0 ) h a s t h e smallest d e g r e e o f s t e r i c i n t e r a c t i o n s b e t w e e n t h e t w o a r y l moieties.

The p h o t o -

c y c l i z a t i o n s o f h a l o s t i l b e n e s h a v e b e e n e x a m i n e d by o t h e r w o r k e r s who r e p o r t t h a t v a r i o u s o_-chloro a n d bromo-compounds

(161) undergo

o x i d a t i v e c y c l i z a t i o n i n cyclohexane s o l u t i o n i n t h e presence of i o d i n e and dehydrohalogenation i n b a s i c s o l u t i o n .

Thus, f o r

e x a m p l e , ( 1 6 1 ) ( X = B r , R=OMe, R'=H) y i e l d s r e s p e c t i v e l y ( 1 6 2 ) a n d ( 1 6 3 ) u n d e r t h e t w o s e t s of c o n d i t i o n s a n d t h a t t h e f o r m e r p r o c e s s o c c u r s i n y i e l d s u p t o 95% a n d t h e l a t t e r 5 7 % , h a v e e n c o u r a g e d t h e u s e o f t h e r e a c t i o n as a r o u t e t o d e h y d r o - o r c h i n o l

acetate (164) which is a p r e c u r s o r o f t h e f u n g i c i d a l p h y t o a l e x i n orchinol. I r r a d i a t i o n o f (165) i n t h e presence of potassium t - b u t o x i d e g i v e s 60% o f ( 1 6 4 ) a n d n o o t h e r c y c l i z e d p r o d u c t s : t h i s r e p r e s e n t s a s i g n i f i c a n t improvement o v e r p r e v i o u s a t t e m p t s t o o b t a i n (164) from t h e 2-iodo-3-acetoxy derivative. Martin and co-workers

h a v e c o n t i n u e d t h e i r work i n t h i s area a n d h a v e

i n v e s t i g a t e d t h e u s e of t h e s t i l b e n e - p h e n a n t h r e n e t y p e c y c l i z a t i o n a s a r o u t e t o f l u o r o h e l i c e n e s . 114'115 1-Fluoropentahelicene (166)

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IIII4: Photochemistry of Aromatic Compounds

307

a n d r e l a t e d compounds h a v e b e e n s y n t h e s i z e d by p h o t o - o x i d a t i v e dehydrocyclization of 3-styrylphenanthrenes and of l,Z-bis(ZFor e x a m p l e , i r r a d i a t i o n o f ( 1 6 7 ) y i e l d s naphthyl) ethylenes. ( 1 6 8 ) a n d ( 1 6 9 ) b u t i n some cases t h e p r o d u c t u n d e r g o e s f u r t h e r c y c l i z a t i o n by e i t h e r t h e l o s s o r m i g r a t i o n o f t h e f l u o r i n e atom: t h i s i s i l l u s t r a t e d by t h e f o r m a t i o n o f t h e b e n z o p e r y l e n e s ( 1 7 0 ) a n d ( 1 7 1 ) f r o m i r r a d i a t i o n o f t h e s t y r y l p h e n a n t h r e n e ( 1 7 2 ) . By t h e u s e o f s i m i l a r p r o c e d u r e s t h e same w o r k e r s s y n t h e s i z e d l - f l u o r o h e x a h e l i c e n e and l - f l u o r o h e p t a h e l i c e n e and t w e l v e o f t h e i r d e r i v a t i v e s from t h e i r r a d i a t i o n o f l - f l u o r o - l l - s t y r y l b e n z o t c l p h e n a n t h r e n e s ( 1 7 3 ) a n d l-fluoro-13-styrylpentahelicenes ( 1 7 4 ) r e s p e c t i v e l y b u t a g a i n t h e c y c l i z a t i o n s were a c c o m p a n i e d b y a dehydrofluorS t i l b e n e s w h i c h are c o n s t r i c t e d i n t o a, cis ination reaction. geometry undergo p h o t o - o x i d a t i v e c y c l i z a t i o n r e a d i l y and f r e q u e n t l y i n good c h e m i c a l y i e l d s . S p a n i s h w o r k e r s h a v e a c h i e v e d t h i s n e c e s s a r y c o n f o r m a t i o n a l r i g i d i t y by means o f t h e c y c l o p h a n e s ( 1 7 5 ) w h i c h on i r r a d i a t i o n i n e t h e r s o l u t i o n w i t h i o d i n e a n d o x y g e n a n d i n t h e a b s e n c e o r p r e s e n c e o f C u ( I 1 ) d e c a n o a t e g i v e s good y i e l d s o f ( 1 7 6 ). '16 The p h e n a n t h r e n e s are r e a d i l y o b t a i n e d f r o m ( 1 7 6 ) by r e d u c t i v e c l e a v a g e and u s i n g t h i s p r o c e d u r e on t h e dimetho x y compound ( 1 7 7 ) w h i c h u n d e r g o e s s i m u l t a n e o u s r e d u c t i o n o f t h e 9 , 1 0 - b o n d , c a n n i t h r e n e I1 ( 1 7 8 ) i s c o n v e n i e n t l y o b t a i n e d . C y c l i z a t i o n o f f i x e d c i s - s t i l b e n e h a s also been o b s e r v e d by K l e t t and Johnson d u r i n g t h e i r s t u d i e s i n t o t h e photorearrangement o f t r i - a n d t e t r a - p h e n y l a l l e n e i n a p r o t i c s o l v e n t s . '17 R o t h a l l e n e s y i e l d p h e n y l a t e d i n d e n e s among t h e p r i m a r y p r o d u c t s a n d ( 1 7 9 ) f r o m t h e t e t r a p h e n y l compound c y c l i z e d p h o t o c h e m i c a l l y t o t h e p h e n a n t h r e n e (180) d i r e c t l y whereas t h e p r e c u r s o r of t h e phenanthrene (181) w a s f o r m e d i n a s e c o n d a r y r e a c t i o n f r o m t r i p h e n y l a l l e n e . The p h o t o p r o c e s s e s o f v i n y l s t i l b e n e s ( 1 8 2 ) c o n t i n u e s t o b e o f i n t e r e s t and t h e product formation and r e l a t i v e r e a c t i o n rates o f compounds h a v i n g a l k y l s u b s t i t u e n t s o n t h e v i n y l g r o u p h a v e b e e n ~ r e p o r t e d . '18 The u s u a l r e a c t i o n p r o d u c t f r o m ( 1 8 2 ) i s a 5 phenylbenzohicyclo~2.l.lJhex-2-ene (183) a n d it i s d e d u c e d t h a t where r e l e v a n t t h e v i n y l m o i e t y must h a v e a n g - c o n f i g u r a t i o n w h e r e a s t h a t o f t h e s t i l b e n e m o i e t y h a s no e f f e c t o n p r o d u c t f o r m a t i o n . The mechanism f o r t h e f o r m a t i o n o f (183) i s r e g a r d e d as i n v o l v i n g a n i n t r a m o l e c u l a r t r a p p i n g of t h e t w i s t e d s i n g l e t b i r a d i c a l of t h e s t i l b e n e by t h e v i n y l g r o u p a n d c o n s i s t e n t w i t h t h i s i n t e r p r e t a t i o n 2 - ( 1- c y c l o h e p t e n y l ) st il b e n e ( 1 8 4 ) y i e l d s 1,6-pen t ame t h y l e n e -5 -ex0 phenylbicycloC2.1.11hex-2-ene ( 1 8 5 ) : t h i s c o n v e r s i o n i s a l s o n o t e -

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w o r t h y f o r i t s quantum y i e l d o f 0 . 9 . The p h o t o r e a c t i o n s o f 2v i n y l s t i l b e n e a n d of 1 , 2 - d i s t y r y l b e n z e n e (186) a n d 2 , 2 ' d i s t y r y l b i p h e n y l ( 1 8 7 ) a d s o r b e d o n s i l i c a g e l h a v e been i n v e s t i g a t e d a n d t h e i n f l u e n c e of g r o u n d - s t a t e c o n f o r m e r s o n t h e f o r m a t i o n of p h o t o p r o d u c t s h a s been d i s c u s s e d . Under s u c h c o n d i t i o n s t h e v i n y l s t i l b e n e g i v e s s e v e r a l p r o d u c t s i n c l u d i n g d e r i v a t i v e s of n a p h t h a l e n e a n d i n d e n e as w e l l as t h e a n d endo-5-phenylbicycloC2.1.1lhex-2-enes which are t h e o n l y p r o d u c t s i n s o l u t i o n . T h i s c o n s i d e r a b l e d i v e r g e n c e of r e a c t i o n pathway i s c o n s i d e r e d t o a r i s e from v a r i a t i o n s i n t h e p h o t o r e a c t i v i t i e s o f t h e v i n y l s t i l b e n e c o n f o r m e r s a n d t h e r e d u c e d m o b i l i t y of t h e b i r a d i c a l p r e c u r s o r s o f t h e bicycloE2.l.llhex-2-enes when t h e s e i n t e r m e d i a t e s are a d s o r b e d on t h e s i l i c a s u r f a c e . D i m e r s are e s s e n t i a l l y t h e s o l e p r o d u c t f r o m i r r a d i a t i o n of s o l u t i o n s o f ( 1 8 6 ) b u t o n a s i l i c a s u r f a c e , t h e s e are accompanied by 5 - e ~ , 6 - e n d o - d i p h e n y l b i c y c l o C 2 . 1 . 1 l h e x e n e (188) a n d t h e i n d e n e d e r i v a t i v e ( 1 8 9 ) w h e r e a s ( 1 8 7 ) p r o d u c e s ( 1 9 0 ) a n d ( 1 9 1 ) i n t h e same r a t i o i n s o l u t i o n and i n the surface reaction. Castle a n d L e e h a v e c o n t i n u e d t h e i r s t u d i e s i n t o t h e u s e o f t h e s t i l b e n e - p h e n a n t h r e n e t y p e c y c l i z a t i o n f o r t h e s y n t h e s i s of p o l y n u c l e a r a r e n e s h a v i n g t h i o p h e n e u n i t s a n d have d e s c r i b e d t h e p r e p a r a t i o n of p e n t a - a n d h e x a - c y c l i c t h i o p h e n e s b y p h o t o - o x i d a t i v e c y c l i z a t i o n of (ary1vinyl)benzothiophenes a n d - d i b e n z o t h i o p h e n e s . 120'121 Thus i r r a d i a t i o n o f ( 1 9 2 ) g i v e s a 73% y i e l d o f benzotriphenylenothiophene ( 1 9 3 ) l 2 O a n d s i m i l a r l y 52% of benzoc h r y s e n o t h i o p h e n e ( 1 9 4 ) is o b t a i n e d f r o m t h e ( n a p h t h y l v i n y 1 ) 121 dibenzothiophene (195). L a s t y e a r R a w a l a n d Cava gave a p r e l i m i n a r y a c c o u n t o f t h e i r s t u d i e s i n t o t h e p h o t o c y c l i z a t i o n of 1,2-dipyrrolyl-ethylenes a n d related systems and p o i n t e d o u t t h a t such p h o t o - o x i d a t i v e c y c l i z a t i o n may be employed as t h e k e y s t e p t o t h e t r i c y c l i c r i n g 122 s t r u c t u r e p r e s e n t i n t h e a n t i t u m o u r a n t i b i o t i c d i p e p t i d e CC-1065. The same w o r k e r s have r e p o r t e d f u r t h e r o n t h e p h o t o c h e m i s t r y o f s u c h s y s t e m s a s ( 1 9 6 ) a n d described t h e i r c y c l i z a t i o n t o ( 1 9 7 ) u n d e r non - o x i d a t i v e c o n d i t i o n s . 123 The r e a c t i o n s are p e r f o r m e d under n i t r o g e n i n a c e t o n i t r i l e s o l u t i o n c o n t a i n i n g 2-nitrobenzoic a c i d a n d t r i e t h y l a m i n e i n t h e p r e s e n c e o f a c a t a l y t i c amount o f palladium on c h a r c o a l as t h e oxidant and under t h e s e c o n d i t i o n s , t h e d i p y r r o l y l compound, f o r e x a m p l e , g i v e s a n 85% y i e l d of a 3 : l m i x t u r e of t h e b e n z o d i p y r r o l e a n d 1,2-di(2-g-methylpyrrolyl) e t h a n e r e s p e c t i v e l y . These workers have also pursued f u r t h e r

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t h e i r o b j e c t i v e o f t h e development of a g e n e r a l a n d f l e x i b l e r o u t e f o r t h e s y n t h e s i s of t h e i n d i v i d u a l m o i e t i e s of t h e d i p e p t i d e CC-1065 a n d a n a l o g u e s and r e p o r t t h e s y n t h e s i s o f t h e B and C u n i t s ( 1 9 8 ) and ( 1 9 9 ) . 124

The k e y s t e p o f p h o t o c y c l i z a t i o n i n c o r -

p o r a t e s t h e u s e o f t h e above p a l l a d i u m m e d i a t i o n o f t h e p r o c e s s and by s u c h a p r o c e d u r e ( 2 0 0 ) i s c o n v e r t e d i n t o ( 2 0 1 ) i n 82% y i e l d . By t h i s a p p r o a c h t h e B and C u n i t s are s y n t h e s i z e d i n o n l y t e n s t e p s s t a r t i n g from p y r r o l e s and i n o v e r a l l y i e l d s of > 20%. A r y l g r o u p s s e p a r a t e d by m o i e t i e s o t h e r t h a n e t h y l e n e a l s o undergo f a c i l e photo-oxidative

c y c l i z a t i o n and t h i s t y p e o f

r e a c t i o n h a s been u s e d t o p r o v i d e t h e r e g i o s p e c i f i c s y n t h e s i s of

2,3,6,7,10,11-hexasubstituted t r i p h e n y l e n e s from 3 , 3 " , 4 , 4 ' , 4 " , 5 ' h e x a s u b s t i t u t e d 1,l' : 2 ' , l " - t e r p h e n y l s . 125 I r r a d i a t i o n o f t h e dimethoxy compound ( 2 0 2 ) i n benzene s o l u t i o n i n t h e p r e s e n c e of i o d i n e g i v e s ( 2 0 3 ) i n 72% y i e l d a n d t h e hexa s u b s t i t u t e d compound ( 2 0 4 ) is s i m i l a r l y formed from ( 2 0 5 ) .

The c o n t r o l of t h e r e g i o -

c h e m i s t r y of t h e p r o c e s s is c o n s i d e r e d t o a r i s e from s t e r i c factors.

The p h o t o c y c l i z a t i o n o f 1 , 2 - d i a r y l p y r r i d i n i u m compounds

i s a w i d e l y a p p l i c a b l e and f r e q u e n t l y h i g h y i e l d r o u t e t o compounds o f t y p e ( 2 0 6 ) . 12' F u r t h e r s t u d i e s on m e c h a n i s t i c a s p e c t s o f t h e p r o c e s s have been d e s c r i b e d and d i h y d r o s p e c i e s a re p r o p o s e d a s r e a c t i o n i n t e r m e d i a t e s . 127

The p h o t o c h e m i s t r y o f t h e b i s

p y r i d i n i u m s a l t ( 2 0 7 ) h a s been examined and q u a n t i t a t i v e y i e l d s o f t h e c y c l i s e d p r o d u c t ( 2 0 8 ) are r e p o r t e d . 12'

The i r r a d i a t i o n o f 2,2,6,6-tetraphenylcyclohexanone is known t o y i e l d ( 2 0 9 ) a n d ( 2 1 0 ) v i a N o r r i s h Type I c l e a v a g e and d e c a r b o n y l a t i o n . J o h n s t o n and S c a i a n o have u s e d t h i s r e a c t i o n t o g e n e r a t e t h e b i r a d i c a l ( 2 1 1 ) 130 and have t h e n s t u d i e d t h e p h o t o c h e m i s t r y o f t h i s s p e c i e s ( ~ z l p s ) . I n b e n z e n e s o l u t i o n a t room t e m p e r a t u r e t h e e x c i t e d s t a t e of ( 2 1 1 ) h a s ~ = 2 . 5 n sa n d t h i s d e c a y s t o a n i n t e r m e d i a t e which a b s o r b s s t r o n g l y a t 480 nm a n d which is b e l i e v e d t o be ( 2 1 2 ) . The f i n a l p r o d u c t from i r r a d i a t i o n o f t h e b i r a d i c a l ( 2 1 1 ) i s ( 2 1 3 ) and t h i s i s r a t i o n a l i z e d by t h e 1 , 5 - s h i f t s a n d r i n g o p e n i n g r e a c t i o n s o u t l i n e d i n Scheme 3. T h i s s t u d y e l e g a n t l y d e m o n s t r a t e s t h e p r o d u c t d i f f e r e n c e s a c h i e v a b l e i n one- and two-photon p r o c e s s e s . I n t r a m o l e c u l a r p h o t o - i n d u c e d c y c l i z a t i o n between a r y l and e t h y l e n e m o i e t i e s is a common r e a c t i o n o b s e r v e d f o r a v a r i e t y o f m o l e c u l a r s t r u c t u r e s . The f o r m a t i o n o f 9,lO-dihydrophenanthrene from i r r a d i a t i o n o f 2 - v i n y l b i p h e n y l s h a s been a s o u r c e o f i n t e r e s t f o r some y e a r s , 131and Lapouyade and co-workers now r e p o r t on t h e s t e r e o c h e m i s t r y of t h e c y c l i z a t i o n . 13' The s i n g l e t e x c i t e d s t a t e

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, 1 0 - d i h y d r o p h e n a n t h r e n e s ( 2 1 5 ) which are a l s o t h e e x c l u s i v e p r o d u c t s f r o m t h e t r i p l e t s t a t e of ( 2 1 4 ) f o r n = l a n d 2. The t r i p l e t s t a t e o f ( 2 1 4 ) f o r n=3 a n d 4 , however, y i e l d s b o t h ( 2 1 5 ) a n d t h e c o r r e s p o n d i n g cis isomers ( 2 1 6 ) which

t r a n s 9,10-cycloalkano-9

are c o n s i d e r e d t o a r i s e from t h e c y c l i z a t i o n of t h e p e r p e n d i c u l a r t r i p l e t of t h e cycloheptenylbiphenyl and from both t h e t r a n s and t h e p e r p e n d i c u l a r t r i p l e t i n t h e case o f t h e c y c l o - o c t e n y l biphenyl.

The mechanism of t h e x a n t h o n e s e n s i t i z e d r e a c t i o n

of t h e 2 - v i n y l b i p h e n y l s

( 2 1 7 ) h a s been s t u d i e d by laser f l a s h

p h o t d l y s i s a n d i t is c o n c l u d e d t h a t t h e f i r s t s t e p i n t h e r e a c t i o n

t o ( 2 1 8 ) is a n a d i a b a t i c p r o c e s s t o g i v e t h e c y c l i z e d p d l y e n e ( 2 1 9 ) i n t h e t r i p l e t s t a t e : 133 T h i s s p e c i e s h a s a l i f e t i m e of 550-750 n s .

F o r compounds i n w h i c h a 90'

t w i s t of the vinylic

bond i s f e a s i b l e , t h e r e s u l t i n g p e r p e n d i c u l a r t r i p l e t l e a d s t o a non-stereospecific

cyclization.

Previous s t u d i e s of t h e i r r a d i -

a t i o n o f l-phenyl-lJ2-dihydronaphthalene

( 2 2 0 ) had been c a r r i e d o u t

i n a p r o t i c s o l v e n t s u s i n g a b r o a d s p e c t r u m lamp and a p a r t f r o m

exo

4-phenyl-benzobicycloC3.l.Olhex-2-ene ( 2 2 1 ) was t h e s o l e p r o d u c t 134 The same r e s e a r c h group h a v e re-examined t h e photo-induced p r o c e s s e s of (220) i n methanol s o l u t i o n i n t h e a b s e n c e or p r e s e n c e of a c i d a n d u s i n g 254 nm r a d i a t i o n now r e p o r t t h a t u n d e r s u c h c o n d i t i o n s t h e sole p r o d u c t i s c i s - d i b e n z o b i c y c l o C3.3.Olocta-2 , 7 - d i e n e ( 2 2 2 ) w h i c h is c o n s i d e r e d t o a r i s e the p e n t a e n e ( 2 2 3 ) a n d t h e c y c l i z e d compound ( 2 2 4 ) . 135 T h i s r e a c t i o n o f f e r s a n a t t r a c t i v e r o u t e t o ( 2 2 2 ) as t h e o v e r a l l y i e l d f r o m n a p h t h o l i s a c h i e v e d i n 65%. The s t e r e o c h e m i c a l c o u r s e of t h e p r e v i o u s l y r e p o r t e d r e d u c t i v e p h o t o c y c l i z a t i o n o f g-cyclohex-le n y l b e n z a m i d e ( 2 2 5 ) t o t h e lactam ( 2 2 6 ) i n t h e p r e s e n c e o f sodium borohydride h a s been e l u c i d a t e d from a n x-ray c r y s t a l l o g r a p h i c s t u d y o f t h e maleic a n h y d r i d e D i e l s - A l d e r a d d u c t ( 2 2 7 ) this r e s u l t s u p p o r t s t h e earlier deductions on t h e s t r u c t u r e of t h e 137 p ho t o p r o d u c t s I t h a s b e e n known f o r o v e r t w e n t y y e a r s t h a t t h e l - a r y l b u t 1 , 3 - d i e n e u n i t i s p h o t o c h e m i c a l l y v e r y r e a c t i v e and u n d e r g o e s f a c i l e c y c l i z a t i o n t o y i e l d n a p h t h a l e n e d e r i v a t i v e s . 13' F u r t h e r a c c o u n t s a n d a p p l i c a t i o n s of t h i s p r o c e s s h a v e b e e n r e p o r t e d i n t h e r e v i e w p e r i o d a n d t h e o x i d a t i v e c y c l i z a t i o n o f 5 - s t y r y l - 1 ,3d i m e t h y l u r a c i l (228) i n d i l u t e a c e t o n i t r i l e s o l u t i o n t o (229) h a s b e e n d e s c r i b e d . 13' Q u e n c h i n g a n d s e n s i t i z a t i o n s t u d i e s i n d i c a t e polymer,

.

316

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317

t h a t t h e c y c l i z a t i o n i s a s i n g l e t s t a t e p r o c e s s but y i e l d s o f t h e p r o d u c t are improved i n t h e p r e s e n c e o f benzophenone s i n c e t h e e f f i c i e n c y of t h e n e c e s s a r y E t o c o n v e r s i o n o f ( 2 2 8 ) i s improved. T h i s t y p e o f c y c l i z a t i o n h a s been o b s e r v e d f o r 2 - s t y r y l i s o f l a v o n e s (230) and p r o v i d e s t h e k e y s t e p i n a f a c i l e s y n t h e s i s o f 5 - a r y l 12H-benzotalxanthen-12-ones (231 ). Over t h e years Heller and co-workers have d e v e l o p e d and e x p l o i t e d t h e p h o t o r e a c t i o n s o f s t e r i c a l l y crowded l - a r y l b u t - 1 , 3 - d i e n e s a s photochromic s y s t e m s and t h e i r s t u d i e s of 16 compounds from t h i s class o f p h o t o l a b i l e s y s t e m s have been described. 14' F o r example, 366 nm r a d i a t i o n o f (232) i n toluene y i e l d s t h e deep blue solvatochromic 1,8ad i h y d r o n a p h t h a l e n e ( 2 3 3 ) which u n d e r g o e s a t h e r m a l 1 , 5 - s h i f t t o t h e c o l o u r l e s s 1 , 2 - d i h y d r o n a p h t h a l e n e as w e l l as t h e r m a l d i s r o t a t o r y r i n g o p e n i n g . The c y c l i z a t i o n i s a l s o r e v e r s e d by w h i t e l i g h t and t h e i m i d e s c o r r e s p o n d i n g t o ( 2 3 2 ) show s i m i l a r p h o t o p r o p e r t i e s . A n o v e l example o f t h i s t y p e of p h o t o c y c l i z a t i o n is o b s e r v e d on i r r a d i t i o n o f benzene s o l u t i o n s o f t h e y-methoxyiminoa , @ - u n s a t u r a t e d carboxamide ( 2 3 4 ) . 142 The i s o l a t e d p r o d u c t is t h e q u i n o l i n e carboxamide (235) b u t t h i s is r e a s o n a b l y p r o p o s e d t o be formed t h e c y c l i z e d i s o m e r ( 2 3 6 ) which e l i m i n a t e s t h e e l e m e n t s o f methanol. I n t r a m o l e c u l a r c y c l i z a t i o n r e s u l t i n g from t h e p h o t o c h e m i c a l l y i n d u c e d l o s s o f h a l o g e n a c i d s i s a common p r o c e s s and o b s e r v e d f o r a wide v a r i e t y o f d i f f e r e n t t y p e s o f compound. Two g r o u p s have r e c e n t l y r e p o r t e d t h e f o r m a t i o n of p h e n a n t h r i d o n e ( 2 3 7 ) by i r r a d i a t i o n of c h l o r i n a t e d d e r i v a t i v e s o f b e n z a n i l i d e , 143 and now Korean w o r k e r s have d e s c r i b e d t h e c y c l i z a t i o n o f t h e same compounds and of t h e bromo- and m e t h o x y - s u b s t i t u t e d d e r i v a t i v e s The r e a c t i o n i s c o n s i d e r e d t o p r o c e e d y& t h e t r i p l e t s t a t e and is e f f i c i e n t f o r t h e 2 - c h l o r o b e n z a n i l i d e ( 2 3 8 ) b u t a p p r e c i a b l y less so f o r t h e 2 ' - c h l o r o isomer ( 2 3 9 ) w h i c h is s u g g e s t e d t o r e f l e c t t h e a s s i s t a n c e g i v e n by t h e N-Ph g r o u p t o t h e l o s s of c h l o r i n e from t h e Ph-CO group: t h i s i s s u p p o r t e d by t h e o b s e r v a t i o n t h a t e l e c t r o n d o n a t i n g g r o u p s i n t h e former m o i e t y accelerate t h e reaction. The c y c l i z a t i o n rate o f 2-methoxybenzanilide i s enhanced i n t h e p r e s e n c e of oxygen and t h i s is i n t e r p r e t e d i n terms of s i n g l e t s t a t e i n t e r m e d i a t e s . I r r a d i a t i o n o f (240) i s r e p o r t e d t o y i e l d (241) which is a f u r t h e r example o f photoi n d u c e d d e h y d r o h a l o g e n a t i o n o f 3-chloronaphthothiophenes t o y i e l d n o v e l naphthothienoquinolines,145 a n d i r r a d i a t i o n of t h e 2-bromo-

Photochemistry

318

( 2 4 2 ) as t h e h y d r o c h l o r i d e

2 ' -iodo-5-benzyl-6-phenethylamine l e a d s t o t h e iododibenzazocine

( 2 4 3 ) . 146

The l a t t e r t y p e o f

r e a c t i o n is a l s o o b s e r v e d f r o m i r r a d i a t i o n o f 1 - ( h y d r o x y p h e n y l -

ethyl)-3-(bromophenyl)propionamides

( 2 4 4 ) u n d e r basic c o n d i t i o n s

when t h e 11-membered r i n g lactams ( 2 4 5 ) a n d ( 2 4 6 ) a r e o b t a i n e d i n 5-46% y i e l d . 147 The p h o t o c h e m i s t r y of t h e g - c h l o r o a c e t y l compound ( 2 4 7 ) h a s b e e n e x a m i n e d w i t h t h e a i m o f f i n d i n g a convenient r o u t e t o t h e p e n t a c y c l i c r i n g system of Strychnos indole I t w a s hoped t h a t i r r a d i a t i o n o f ( 2 4 7 ) would l e a d a l k a l o i d s . 148

t o a dehydrohalogenation and c y c l i z a t i o n a t t h e i n d o l e 3 - p o s i t i o n b u t a l t h o u g h c y c l i z a t i o n d i d o c c u r t h e p r o c e s s i n v o l v e d t h e benzo I r r a d i a t i o n o f 1r i n g a n d ( 2 4 8 ) w a s i s o l a t e d i n 40% y i e l d . chlom-2-phenylethane i n alcohols y i e l d s t h e corresponding carbinols a n d e t h e r s b u t 1 - c h l o r o - 4 - p h e n y l b u t a n e u n d e r g o e s c y c l i z a t i o n t o give t e t r a l i n as w e l l a s f o r m a t i o n o f n - h u t y l b e n z e n e a n d 4 - p h e n y l b u t 1 49 1-ene A wide d i v e r s i t y o f 2-aryl s u b s t i t u e n t s r e s u l t i n c y c l i z a t i o n products on i r r a d i a t i o n . R e p r e s e n t a t i v e examples o f t h i s t y p e o f r e a c t i o n f r o m t h e c u r r e n t l i t e r a t u r e are g i v e n h e r e f o r i l l u s t r a t i v e purposes. Japanese workers have s t u d i e d t h e i r r a d i a t i o n o f s e v e r a l 2- a n d E - s u b s t i t u t e d aromatic p o l y c a r b o n y l compounds a n d f r o m t h e t r i - i s o p r o p y l compound ( 2 4 9 ) i n b e n z e n e s o l u t i o n , h a v e i s o l a t e d t h e b e n z o c y c l o b u t e n e ( 2 5 0 ) . 150 L a s t y e a r Wagner a n d co-

.

w o r k e r s r e p o r t e d s e v e r a l cases o f i n t r a m o l e c u l a r c y c l i z a t i o n i n v o l v i n g a c e t o p h e n o n e s a n d b e n z o p h e n o n e s a n d h a v e now d e s c r i b e d t h e q u a n t i t a t i v e conversion of 2-t-butylbenzophenone dimethyl-1-indanol

t o 1 - p h e n y l - 3 ,3-

( 2 5 1 ) i n t h e s o l i d s t a t e o r s o l u t i o n from

77K t o room t e m p e r a t u r e . 15'

A s i m i l a r p r o c e s s occurs w i t h

when ( 2 5 2 ) i s f o r m e d both i n e t h y l 152 acetate s o l u t i o n or i n c r o s s l i n k e d e t h y l e n e - v i n y l acetate beads, a n d Dspp a n d c o - w o r k e r s h a v e d i s c u s s e d s t r u c t u r e - r e a c t i v i t y c o r r e l a t i o n i n v o l v e d i n t h e c o n v e r s i o n of c e r t a i n 2 - n i t r o - t b u t y l b e n z e n e s t o ( 2 5 3 ) . 153 I n t h e l a t t e r s t u d y t h e m o l e c u l a r s t r u c t u r e o f t h e s t a r t i n g material h a s been determined by x - r a y c r y s t a l l o g r a p h y and t h e p h o t o r e a c t i v i t y o f t h e n i t r o a r e n e i n t h e s o l i d s t a t e is r a t i o n a l i z e d i n t e r m s of i n t r a m o l e c u l a r g e o m e t r i c a l parameters a n d i n t e r m o l e c u l a r p a c k i n g c o n s i d e r a t i o n s . 4-Substituted 2 ' -hydroxychalcones (254) undergo s e l e c t i v e photo154 c y c l i z a t i o n i n p o l a r a p r o t i c s o l v e n t s t o y i e l d flavanones (255). The e f f i c i e n c y o f t h e p r o c e s s is l o w a n d h y d r o x y l i c s o l v e n t s which

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i n h i b i t f o r m a t i o n o f t h e c y c l i c i n t r a m o l e c u l a r H-bond markedly retard

t h e r e a c t i o n which i s c o n s i d e r e d t o p r o c e e d

the

i n t e r m e d i a t e s o u t l i n e d i n Scheme 4. As may be e x p e c t e d i n t r a m o l e c u l a r c y c l i z a t i o n of 2 - d i s u b s t i t u t e d photo-induced

a r e n e s c a n be i n i t i a t e d by

e l i m i n a t i o n of h a l o g e n a c i d and f o r example ( 2 5 6 )

is among t h e p r o d u c t s f r o m i r r a d i a t i o n o f t h e a - c h l o r o compound ( 2 5 7 ) . 155 Tulo g r o u p s have d e s c r i b e d p h o t o c y c l i z a t i o n r e a c t i o n s of o r g a n o s i l a n e s . Canadian w o r k e r s have o b s e r v e d a two-photon p r o c e s s from m e s i t o y l tris(trimethylsily1)silane ( 2 5 8 ) which y i e l d s y t h e i n t e r m e d i a t e s i l e n e (260 ) : 156 t h e b e n z o c y c l o b u t e n e (259) & t h e c y c l i z a t i o n p r o c e s s t o (259) i n v o l v e s a photo-induced

insert-

i o n of t h e C=Si m o i e t y i n t o a r e l a t i v e l y u n a c t i v a t e d C-H bond. The second r e p o r t i s concerned w i t h t h e p h o t o r e a c t i o n s o f t h e l-silaeyclobut-2-ene

( 2 6 1 ) . 157

The i r r a d i a t i o n i s c a r r i e d o u t

i n d r y benzene u n d e r n i t r o g e n and y i e l d s t h e l - s i l a c y c l o p e n t a - 2 , 4 d i e n e (262)

e, i t is p r o p o s e d ,

t h e l-silabicycloC2.1.0lpent-3-

ene intermediate (263). 5 Dimerization Reactions P h o t o d i m e r i z a t i o n i s common for a n t h r a c e n e s , less s o f o r n a p h t h a l e n e s , and u n t i l t h i s y e a r o n l y o n e example o f t h i s r e a c t i o n w i t h a b e n z e n o i d compound had a p p e a r e d . Thus i r r a d i a t i o n o f

diheteraC3.3lmetacyclophanes y i e l d s ( 2 6 4 ) and f u l l d e t a i l s of t h i s A somewhat more s i m p l e example of p h o t o d i m e r i z a t i o n of benzene r i n g s h a s , however, now been d e s c r i b e d by P r i n z b a c h and co-workers. 159 I r r a d i a t i o n (254 nm) of ( 2 6 5 ) and (266) i n i s o - o c t a n e i n d u c e s a C6+6lbenzo-benzo c y c l o a d d i t i o n and t h e f o r m a t i o n o f ( 2 6 7 ) . The retro a d d i t i o n i s a l s o i n i t i a t e d under t h e c o n d i t i o n s of formation of t h e i n t r a m o l e c u l a r dimer and hence t h e r e a c t i o n r e a c h e s a p h o t o e q u i l i b r i u m w i t h r a t i o s of ( 2 6 5 ) t o ( 2 6 7 ) of 1:l t o 2 : 5 r e s p e c t i v e l y dependent on t h e s u b s t i t u e n t s . The same group have also examined t h e u s e of s u c h m o l e c u l a r c o n s t r a i n t s as i n ( 2 6 5 ) t o o r i e n t t h e benzo and azo (and a z o x y ) chromophores and t h e r e b y r e n d e r C6+21 c y c l o X-Ray c r y s t a l l o g r a p h i c d a t a f o r ( 2 6 8 ) a d d i t i o n s v e r y l i k e l y . 160 show t h a t t h e geometry is i n d e e d f a v o u r a b l e for t h e c y c l o a d d i t i o n b u t 254 nm or w a v e l e n g t h s l o n g e r t h a n 280 nm i r r a d i a t i o n o f t h e bichromophore i n methanol o r a c e t o n e s o l u t i o n a t -5OOC s i m p l y i n i t i a t e s t h e s l o w e l i m i n a t i o n of n i t r o g e n and f o r m a t i o n of ( 2 6 9 ) . The azoxy d e r i v a t i v e of ( 2 6 8 ) u n d e r s i m i l a r c o n d i t i o n s y i e l d s (268) and t h e n c e (269).

p r o c e s s have now been p u b l i s h e d . 158


(270) R-R = bond (272) R = H

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(279) X = -C H, -CHz(282) X = S i M e 2 (283) X =GeMe2

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325

Over t h e y e a r s t h e r e have been many r e p o r t s t h a t photoreactions, particularly dimerization processes, carried out i n m i c e l l e s , m i c r o e m u l s i o n s , and c y c l o d e x t r i n c a v i t i e s f r e q u e n t l y show a higher s e l e c t i v i t y and o c c u r a t a greater r a t e t h a n t h e corresponding process i n simple s o l u t i o n . I t i s , t h e r e f o r e , of i n t e r e s t b u t no g r e a t s u r p r i s e t o n o t e t h a t t h e p h o t o d i m e r i z a t i o n of w a t e r - s o l u b l e a n t h r a c e n e s s u c h a s 2 - a n t h r a c e n e s u l p h o n a t e i n aqueous s o l u t i o n i s a c c e l e r a t e d i n t h e p r e s e n c e o f B and y c y c l o dextrins. The s e l e c t i v i t y of t h e p r o c e s s i s , however, markedly dependent on t h e p a r t i c u l a r h o s t m o l e c u l e and w h i l e t h e f o u r c o n f i g u r a t i o n a l i s o m e r s of t h e 9 , l o - , 9',10' -photodimer were o b t a i n e d i n t h e p r e s e n c e o f y - c y c l o d e x t r i n i n r a t i o s similar t o t h o s e o b s e r v e d i n h o s t - f r e e s o l u t i o n , i n t h e p r e s e n c e o f B-cyclod e x t r i n o n l y one o f t h e isomers was formed. These r e s u l t s a g a i n i l l u s t r a t e t h e ' f i n e t u n i n g ' which may be imposed on p h o t o r e a c t i o n s by t h e u s e of h o s t - g u e s t s i t u a t i o n s . I t was r e p o r t e d l a s t y e a r t h a t 1-(9-anthry1)-2-phenylacetylene p h o t o d i m e r i z e d t o g i v e ( 2 7 0 ) i n 70% y i e l d . 162 The same g r o u p have a l s o examined t h e photo-induced r e a c t i o n s o f t r a n s - l - ( g - a n t h r y l ) 2 - p h e n y l e t h y l e n e ( 2 7 1 ) , and w h i l e t h e dimer ( 2 7 2 ) c o r r e s p o n d i n g t o ( 2 7 0 ) is t h e major p r o d u c t , 9,10-,9',10'-dimerization t o g i v e ( 2 7 3 ) and C B ~ ~ + 6 1 ~ l c y c l o a d d i tri eo snu l t i n g i n t h e f o r m a t i o n o f (274) and ( 2 7 5 ) are a l s o o b s e r v e d . 163 The r e s p e c t i v e r a t i o o f ( 2 7 2 ) , ( 2 7 3 ) , ( 2 7 4 ) , and ( 2 7 5 ) i s 2 0 : 2 : 2 : 1 and a s t h i s r a t i o i s c o n s t a n t i t i s deduced t h a t a l l p r o d u c t s a r i s e d i r e c t l y from ( 2 7 1 ) . I t i s a l s o r e p o r t e d t h a t t h e m a j o r p r o d u c t ( 2 7 2 ) i s o m e r i z e s t o (274) and u n d e r g o e s c y c l o r e v e r s i o n on direct i r r a d i a t i o n and w i t h b i a c e t y l s e n s i t i z a t i o n forms ( 2 7 5 ) : t h e quantum y i e l d s f o r t h e s e p r o c e s s e s are 0 . 1 , 0 . 0 3 , and 0 . 0 1 r e s p e c t i v e l y . 9,10-,9',10'-Photodimers o f a n t h r a c e n e s undergo p h o t o r e t r o a d d i t i o n and i n t h e past t h i s has been a l s o a c h i e v e d w i t h c h l o r a n i l and d i c y a n o a n t h r a c e n e a s s e n s i t i z e r s . 164 F u r t h e r s t u d i e s on similar s y s t e m s have now been r e p o r t e d and a r a n g e o f head-to-tail d i m e r s of s u b s t i t u t e d a n t h r a c e n e s have been monomerized by i r r a d i a t i o n w i t h i n e i t h e r of t h e 165 t w o c h a r g e - t r a n s f e r b a n d s of t h e dimer-tetracyanoethylene complex. The r e c e n t i n t e r e s t i n t h e p h o t o c h e m i s t r y of l i n k e d a n t h r a c e n e s y s t e m s c o n t i n u e s . The syn[2.2.l(1,4)anthracenophane ( 2 7 6 ) and i t s photodimer ( 2 7 7 ) had been p r e v i o u s l y d e s c r i b e d i n 1972,166 and now t h e same workers have c o n f i r m e d these s t r u c t u r e s by Z-ray c r y s t a l l T h e d i m e r i z a t i o n o c c u r s w i t h 374 nm r a d i a t i o n and ogr aphy .167 is r e v e r s e d w i t h 254 nm r a d i a t i o n o r a t 22OoC. Two r e p o r t s O f

326

Photochemistry

1,2-,9',10'-dimerization of l i n k e d a n t h r a c e n e s have a p p e a r e d r e c e n t l y , 1687169 and f u r t h e r s t u d i e s i n v o l v i n g t h e p r o c e s s f o r 1 , 2 - d i ( g - a n t h r y l ) e t h a n e ( 2 7 8 ) have been d e s c r i b e d . 1709171 B i a c e t y l s e n s i t i z e d i r r a d i a t i o n o f ( 2 7 8 ) l e a d s e x c l u s i v e l y t o t h e 1 , 2 - , 9',10'dimer ( 2 7 9 ) w i t h a quantum y i e l d o f 0 . 1 and a c h e m i c a l y i e l d o f 62% whereas d i r e c t i r r a d i a t i o n p r o d u c e s t h e 9 , 1 0 - , 9 ' , 1 0 ' - d i m e r . T h e d i m e r i z a t i o n p r o c e s s e s a r e , n o t s u r p r i s i n g l y , i n f l u e n c e d by g e o m e t r i c a l e f f e c t s and f o r example, w h i l e t h e t e t r a c h l o r o compound ( 2 8 0 ) b e h a v e s a n a l o g o u s l y t o t h e hydrocarbon ( 2 7 8 ) i n b o t h d i r e c t and b i a c e t y l s e n s i t i z e d i r r a d i a t i o n s , o n l y t h e 9 , 1 0 - , 9 ' , 1 0 ' dimer i s formed from t h e t e t r a c h l o r o isomer ( 2 8 1 ) u n d e r b o t h sets of c o n d i t i o n s . Bouas-Laurent and co-workers r e c e n t l y r e p o r t e d t h a t w i t h a -Si(Me)2- u n i t c o n n e c t i n g t h e two a n t h r a c e n e s a t t h e 9 - p o s i t i o n s , t h e p h o t o d i m e r i z a t i o n r e a c t i o n is d i r e c t e d e x c l u s i v e l y

t o t h e 1 , 2 - , 9 ' , 1 0 ' - p o s i t i o n s t o y i e l d (282). Japanese workers have a l s o o b s e r v e d t h i s p r o c e s s and now d e s c r i b e t h e i r own s t u d i e s which a r e s i m i l a r t o t h o s e r e p o r t e d e a r l i e r b u t which a l s o i n c l u d e t h e f o r m a t i o n o f ( 2 8 3 ) from t h e germanium compound. 172 An e l e g a n t example o f t h e u s e o f c a t i o n s t o d i r e c t t h e p h o t o p h y s i c s and p h o t o c h e m i s t r y o f l i n k e d a n t h r a c e n e s h a s been d e s c r i b e d f o r t h e anthraceno-crown e t h e r ( 2 8 4 ) . 173 I r r a d i a t i o n a t w a v e l e n g t h s l o n g e r t h a n 330 nm o f ( 2 8 4 ) i n d e g a s s e d methanol s o l u t i o n y i e l d s t h e 9,10-,1',4'-intramolecular dimer ( 2 8 5 ) and t h e a b s e n c e o f t h e c l a s s i c a l 9,10-,9',10'-dimer ( 2 8 6 ) i s r a t i o n a l i z e d i n terms o f e l e c t r o n i c r e p u l s i o n between t h e l o n e p a i r s o f t h e oxygen atoms a t these positions. I n t h e p r e s e n c e o f sodium i o n s , however, t h e p h o t o p r o d u c t i s deduced t o be ( 2 8 6 ) and a l t h o u g h t h i s i s n o t i s o l a t e d t h e evidenCe f o r i t s f o r m a t i o n i s c o m p e l l i n g . I t i s s u g g e s t e d t h a t t h e change of d i r e c t i o n i n t h e p h o t o d i m e r i z a t i o n r e s u l t s from a d e c r e a s e i n t h e oxygen l o n e p a i r r e p u l s i o n on comp l e x a t i o n and t h i s r e s t o r e s t h e normal r e g i o c h e m i s t r y o f t h e r e a c t i o n . T h i s change i n t h e p o s i t i o n s o f d i m e r i z a t i o n i s accompani e d by s i g n i f i c a n t d i f f e r e n c e s i n t h e f l u o r e s c e n c e o f (284) i n t h e a b s e n c e and p r e s e n c e of sodium i o n s : i n t h e former case b o t h s t r u c t u r e d monomer and u n s t r u c t u r e d excimer e m i s s i o n are o b s e r v e d b u t when complexed t h e l a t t e r band is r e d s h i f t e d and i n c r e a s e s Intrachain i n i n t e n s i t y a t t h e e x p e n s e o f t h e monomer band. p h o t o d i m e r i z a t i o n of t h e a n t h r a c e n e m o i e t i e s of 9 - a n t h r y l m e t h y l m e t h a c r y l a t e - m e t h y l m e t h a c r y l a t e copolymers i n d i o x a n e s o l u t i o n h a s been s t u d i e d by R u s s i a n w o r k e r s who c o n c l u d e t h a t t h e r e a c t i o n a r i s e s from t w o mechanisms which g i v e s d i m e r s h a v i n g d i f f e r e n t

lIll4: Photochemistry of Aromatic Compounds

327

s t r u c t u r e s . 174 A c r i d i z i n i u m s a l t s a l s o undergo C4+41 d i m e r i z a t i o n t o y i e l d ( 2 8 7 ) and a s p e c t s of t h e i n t r a m o l e c u l a r i n t e r a c t i o n and r e a c t i o n of t h e a r e n e chromophores i n compounds o f t y p e (288) w i t h n=1-6 and 8 have been 176 The quantum y i e l d s o f t h e r e v e r s i b l e i n t r a m o l e c u l a r d i m e r i z a t i o n have been d e t e r m i n e d i n s e v e r a l s o l v e n t s and are r e p o r t e d t o depend upon t h e v a l u e of g . Formation of t h e dimer a r i s e s from t h e i n t r a m o l e c u l a r excimer and a common p e r i c y c l i c t r a n s i t i o n s t a t e i s assumed f o r t h e forward and back reactions. 6 L a t e r a l - N u c l e a r Rearrangements Arenes of t h e t y p e Ar-X-Y i n which t h e X-Y bond i s r e a d i l y c l e a v e d h o m o l y t i c a l l y undergo f a c i l e l a t e r a l - n x c l e a r r e a r r a n g e m e n t . The a r c h e t y p a l example o f t h i s p r o c e s s i s t h e p h o t o - F r i e s r e a r r a n g e ment which o c c u r s w i t h a r y l e s t e r s and a n i l i d e s and s e v e r a l r e p o r t s o f t h e s e r e a c t i o n s have a p p e a r e d w i t h i n t h e r e v i e w p e r i o d . S e v e r a l b e n w y l o x y n a p h t h a l e n e s , q u i n o l i n e s , and b e n z e n e s have been p h o t o r e a r r a n g e d t o t h e c o r r e s p o n d i n g C-benzoyl p r o d u c t s and t h e m a g n e t i c i s o t o p e and e x t e r n a l m a g n e t i c f i e l d e f f e c t s upon t h e 178 p h o t o - F r i e s r e a c t i o n o f l - n a p h t h y l acetate have been r e p o r t e d . The y i e l d o f 2 - a c e t y l - l - n a p h t h o l , t h e i n - c a g e p r o d u c t from 1n a p h t h y l acetate, show an e x t e r n a l m a g n e t i c f i e l d e f f e c t f o r t h e e s t e r l a b e l l e d w i t h m a g n e t i c a l l y a c t i v e 1 3 C b u t none f o r t h e 1 2 C e s t e r . T h i s f e a t u r e is e x p l a i n e d i n terms o f a r a d i c a l p a i r mechanism from a c o n s i d e r a t i o n of h y p e r f i n e c o u p l i n g between t h e H' and 1 3 C and t h e u n p a i r e d e l e c t r o n on t h e a c e t y l r a d i c a l . Two g r o u p s t h i s y e a r have d e s c r i b e d f e a t u r e s of t h e p h o t o - F r i e s r e a c t i o n of a r y l c i n n a m a t e s . 179J180 I t h a s been p r e v i o u s l y r e p o r t e d t h a t p h e n y l cinnaniate g i v e s 20-308 y i e l d s of 2 ' -hydroxyc h a l c o n e s , 18' b u t now I n d i a n w o r k e r s have examined t h e p h o t o r e a r r a n g e m e n t of t h e c i n n a m a t e s ( 2 8 9 ) i n micellar environment and o b s e r v e an e f f i c i e n t and h i g h y i e l d s y n t h e s i s o f t h e c o r r e s p o n d i n g 2'-hydroxy c h a l c o n e s ( 2 9 0 ) . 17' The 4 ' - i s o m e r ( 2 9 1 ) i s a l s o formed and a l t h o u g h t h e r a t i o of t h e two p r o d u c t s depends on t h e a r y l s u b s t i t u e n t s , t h e t o t a l y i e l d s o f r e a r r a n g e m e n t a r e between 'ZO and 90%. The o t h e r s t u d y of t h e p h o t o c h e m i s t r y of c i n n a m a t e s h a s been c o n c e r n e d w i t h a comparison between t h e r e a c t i o n s o f ( 2 8 9 ) The l a t t e r undergo t h e p h o t o - F r i e s and a r y l d i h y d r o c i n n a m a t e s .

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r e a c t i o n more e f f i c i e n t l y t h a n ( 2 8 9 ) and y i e l d t h e 2'-hydroxyd i h y d r o c h a l o n e s ( 2 9 2 ) so t h a t i t a p p e a r s b e n e f i c i a l t o c o n s i d e r

Photochemistry

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Photochemistry

330

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(305) R = OMe, R’ = H (307)

R = H,

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d e h y d r o g e n a t i o n of ( 2 9 2 ) t o ( 2 9 0 ) i n t h e s y n t h e s i s o f f l a v o n e s ( 2 9 3 ) r a t h e r t h a n u s e t h e more d i r e c t r o u t e i n v o l v i n g r e a r r a n g e m e n t of t h e cinnamates. D u r i n g an i n v e s t i g a t i o n o f t h e p h o t o c h e m i c a l r e a r r a n g e m e n t o f a l l e n i c ester t o c y c l o b u t e n o n e s , it h a s been o b s e r v e d t h a t f o r t h e p h e n y l ester ( 2 9 4 ) a p h o t o - F r i e s r e a c t i o n o c c u r s 182 Y i e l d s are low ( 4 % ) and as e x p e c t e d t h e p r o d u c t ( 2 9 5 ) is accompanied by p h e n o l .

.

A c e t a n i l i d e s have been known f o r many y e a r s t o undergo p h o t o F r i e s r e a r r a n g e m e n t s , 182 and s u c h p r o c e s s e s w i t h b e n z a n i l i d e s have r e c e i v e d f u r t h e r comment. 183 The 2- and 2 ' - m e t h y l b e n z a n i l i d e s b o t h y i e l d t h e e x p e c t e d F r i e s p r o d u c t s and t h e e f f i c i e n c y o f t h e former i s g r e a t e r i n non-polar and non-viscous s o l v e n t s t h a n i n p o l a r and v i s c o u s media. The c o r r e s p o n d i n g n i t r o b e n z a n i l i d e s are p h o t o i n e r t which is c o n s i d e r e d t o r e f l e c t t h e lower e n e r g y o f t h e e x c i t e d s t a t e r e s u l t i n g from t h e p r e s e n c e of t h e s u b s t i t u e n t . Both N,_N-dibenzoyl and _N,N-di-(2-chlorobenzoyl) a n i l i n e s undergo t h e photo-Fries r e a c t i o n . The o b s e r v a t i o n o f t h e p r o c e s s i n t h e l a t t e r c a s e i s s u r p r i s i n g i n view o f t h e r e p o r t e d f a c i l e photode144 h y d r o h a l o g e n a t i o n and c y c l i z a t i o n o f 2 - c h l o r o b e n z a n i l i d e . F u r t h e r d e t a i l s have a p p e a r e d o f t h e p h o t o r e a r r a n g e m e n t of Pl,O_-diacyl-N-phenylhydroxylamines ( 2 9 6 ) . 184 The m i g r a t i n g s p e c i e s i n t h i s c a s e is 'OCOR' ( r a t h e r t h a n 'COR) and b o t h o r t h o and p a r a i s o m e r s ( 2 9 7 ) and ( 2 9 8 ) r e s p e c t i v e l y are formed as w e l l as RCONHPh, R'C02H, and R ' H . The mechanism o f t h i s p r o c e s s h a s been derivative i n v e s t i g a t e d u s i n g t h e g-(l-naphthoyl)-Q-(p-toluoyl) and i t i s r e p o r t e d t h a t t h e r e a c t i o n i s s e n s i t i z e d by benzophenone b u t t h a t t h e r e a r r a n g e m e n t from d i r e c t i r r a d i a t i o n o c c u r s e x c l u s i v e l y from t h e S1 s t a t e : 185 t h i s is r a t i o n a l i z e d by t h e l a r g e e n e r g y gap between t h e S1 and TI s t a t e s of ( 2 9 6 ) . Two examples o f r i n g e x p a n s i o n by l a t e r a l - n u c l e a r r e a r r a n g e ment have b e e n r e p o r t e d w i t h i n t h e y e a r . J a p a n e s e w o r k e r s have given a f u l l e r account of t h e i r earlier r e p o r t e d o b s e r v a t i o n s c o n c e r n i n g t h e p h o t o r e a r r a n g e m e n t o f 2-aryl-1,2-benzisothiazolino n e s ( 2 9 9 ) which w i t h 340 nm r a d i a t i o n i n benzene s o l u t i o n g i v e 13% of (300),186 and T u r r o and co-workers have d e s c r i b e d t h e forma t i o n o f p a r a c y c l o p h a n e s (301) from t h e i r r a d i a t i o n o f l a r g e r i n g 2-phenylcyclanones ( 3 0 2 ) . 187 T h i s l a t t e r r e a c t i o n o c c u r s f o r 1 0 , 1 1 , 1 2 , and 15-membered r i n g c y c l a n o n e s and a r i s e s an u n p r e c e d e n t e d c o m b i n a t i o n p r o c e s s o f b i r a d i c a l s . A t < 15% conv e r s i o n , t h e CI1 compound g i v e s a 94% y i e l d of t h e cyclophane w i t h a quantum y i e l d o f 0 . 6 and t h e s t u d y h a s been e l e g a n t l y and

332

Photochemistry

successfully extended to the formation of the biradicals in the intracrystalline supercage of a NaX zeolite: the cyclanone is absorbed, photolyzed, and gives the paracyclophane trapped by a 'ship in bottle' strategy. The photorearrangement of azoxybenzenes to hydrazobenzenes is a well-studied process but one which continues to attract attention. The reaction has now been studied for methoxy and dimethylamino azoxybenzenes and the rearrangement is observed with 188 varying efficiency for all but the disubstituted derivatives. The intermediate is considered to be (303) which either reverts to starting material or yields the 2-hydroxy compound (304) by either acid or base catalysis. Rates of reaction are very dependent on positions of the substituents and while the conversion of (305) to (306) is efficient, the corresponding process of (307) proceeds slowly. Introduction of dimethylamino substituents markedly reduces the photoreactivity of the azoxybenzene and products derived from intramolecular hydrogen abstraction and cleavage of M=N or C=N bonds become evident. The conversion of (305) to (307) is reported to be a general one-way process for these systems and the azoxy isomer formed is always that with the -N-oxide function far from the arene moiety which has the stronger electron donating substituent. Irradiation of sulphonium salts (308) in acetonitrile solution has been shown to lead to lateral-nuclear rearrangement and the 189 formation of l-(methylthi0)-2-~ubstituted alkylnaphthalenes (309). The quantum yield of product formation varies between 0 . 2 4 and 0.1 but bond cleavage to yield 1-naphthyl methyl sulphide also occurs and MeCONH-CH2-R is a by-product of the migrating group and the solvent. The steric crowding in Ctris(trimethylsilyl)methyll benzene (310) is considered to be the origin of its photolability and on irradiation it efficiently yields (311), (312), and five isomers of (310) in a respective approximate ratio of 13:1:6: a trace of phenyltrimethylsilane is also formed. The reaction is acid catalyzed and with DC1, all the deuterium is incorporated at the benzylic position of (311). The observations are rationalized by a radical combination within a cage to give (313) which on protonation (deuteration) gives (314) and thence either (311) or (312) by deprotonation or loss of Me3Si+respectively.


333

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Photochemistry L.J.Johnston and J.C.Scaiano, J.Amer.Chem.Soc., 1986, 108, 2349. See for example A.Padwa, C.Doubleday, and A.Mazzu, J.Org.Chem., 1977, 42, 3271. R.Lapouyade, C.Manigand, and A.Mourmamode, Canad.J.Chem., 1985, 63, 2192. S.Lazare, R.Lapouyade, and R.Bonneau, J.Amer.Chem.Soc., 1985. 107,6604. J.J.M.Lamberts and W.H.Laarhoven, Rec1.Trav.Chim.Pays-Bas, 1984, 103, 131. W.H.Laarhoven, F.A.T.Lijten, and J.M.M.Smits, J.Org.Chem., 1985, 50, 3208. T.Naito, I.Ninomiya, M.Doi, and M.Inoue, Heterocycles, 1985, 23, 1215. T.Naito, Y.Tada, Y.Nishiguchi, and I.Ninomiya, J.Chem.Soc.Perkin Trans.1, 1985, 487. G.J.Fonken, Chem.and Ind., 1962, 1327. S.C.Shim, E.J.Shin, and B.S.An, J.Photochem., 1986, 32, 369. B.V.Maliaiah, G.L.D.Krupadanam, and G.Srimannarayana, Indian J.Chem.Sect.B, 1985, E , 862. P.J.Darcy, H.G.Heller, S.Patharakorn, R.D.Piggott, and J.Whittal1, J.Chem.Soc.Perkin Trans.1, 1986, 315. V.H.M.Elferink and H.J.T.Bos, J.Chem.Soc.Chea.Com., 1985, 882. J.Grimshaw and A.P.de Silva, J.Chem.Soc.Perkin Trans.11, 1982, 857; M.Orlic-Nuber, G.Karminski-Zamola, L.Fiser-Jakic, and J.Jakopcic, Glas.Hem.Drus.Beograd., 1983, 48, 409. Y .T. Park, S.R. Do, and K.D. Lee, Taehan Hwahakhoe Chi. , 1985, 3, 426 (Chem.Abstr. , 104,108 729). H.Kudo, R.N.Castle, and M.L.Lee, J.Heterocycl.Chem., 1985, 22, 211. S.Kobayashi, M.Kihara, and Y.Miyake, Heterocycles, -1985, 2, 159. O.Hoshino, H.Ogasawara, A.Takahashi, and B.Umezawa, Heterocycles, 1985, 23, 1943. J.Bosch, M.Amat, E.Sanfeliu, and M.A.Miranda, Tetrahedron, 1985, 41, 2557. V.K.Bhalerao, B.S.Nanjundiah, H.R.Sonawane, and P.M.Nair, Tetrahedron, 1986 , 42, 1487. Y.Ito, N.Kawatsuki, B.P.Giri, M.Yoshida, and T.Matsuura, J.Org.Chem., 1985, 50, 2893. P.J.Wagner, B.P.Giri, J.C.Scaiano, D.L.Ward, E.Gabe, and F.L.Lee, J.Amer.Chem.Soc., 1985, 107, 5483. J.E.Guillet, W.K.MacInnis, and A.E.Redpath, Canad.J.Chem., 1985, 63, 1333. K.Padmanabhan, D . d p p l K.Venkatesan, and V.Ramamuthy, J.Chem.Soc.Perkin Trans.11, 1986, 897. R.Matsushima and H.Kageyama, J.Chem.Soc.Perkin Tians.11, 1985, 743. W.R.Bergmark, C.Barnes, J.Clark, S.Paparian, and S.Marynowski, J.Org.Chem., 1985, 50, 5612. A.G.Brook and H.J.Wessely, Organometallics, 1985, 2, 1487. M.Ishikawa, H.Sugisawa, S.Matsuzawa, K.Hirotsu, and T.Higuchi, Organometallics, 1986, 5, 182. H.Higuchi, E.Kobayashi, Y.Sakata, and S.Miswni, Tetrahedron, 1986, 42, 1731. G.Sedelmeier, W-D.Fessner, C.Grund, P.R.Spurr, H.Fritz, and H.Prinzbach, Tetrahedron Letters, 1986, 27, 1277. G.Fischer, E.Beckmann, and H.Prinzbach, Tetrahedron Letters, 1986, 27, 1273. T.Tamaki and T.Kokubu, J.Inclusion Phenom., 1984, 2, 815. H-D.Becker and K.Andersson, J.Photochem., 1984, 26, 75. 3913. H-D.Becker, K.Andersson, andJ.Org.Chem., 1985, R.A.Barber, P.de Mayo, K.Okada, and S.K.Wong, J.Amer.Chem.Soc., 1982, 104, 4995. J.M.Masnovi and J.K.Kochi, J.Amer.Chem.Soc., 1985, 107, 6781. T.Otsubo, Y.Sakata, and S.Misumi, Tetrahedron Letters, 1972, 1731.

so,

IIIl4: Photochemistry of Aromatic Compounds 167. 168. 169. 170. 171. 172.

337

T.Toyoda, N.Kasai, and S.Misumi, Bull.Chem.Soc.Jap., 1985, 58, 2348. H-D.Becker and K.Sandross, Tetrahedron Letters, 1983, 24, 3273. M.Daney, C.Vanucci, J-P.Desvergne, A.Castellan, and H.Bouas-Laurent, Tetrahedron Letters, 1985, 2, 1505. H-D.Becker and K.Andersson, Tetrahedron Letters, 1985, 3,6129. H-D.Becker andK.Andersson, Tetrahedron, 1986, 42, 1555. H.Sakurai, K.Sakamoto, A.Nakamura, and M.Kira, Chemistry Letters, 1985, 497.

173. 174, 175. 176. 177. 178. 179. 180. 181. 182. 183. 184.

H.Bouas-Laurent, A.Castellan, M.Daney, J-P.Desvergne, G.Guinand, P. Marsau, and M-H.Riffaud, J.Amer.Chem.Soc., 1986, 108,315. S.P.Koze1, G.I.Lashkov, M.G.Krakovyak, M.G.Shelekhov, and S.S.Skorokhodov, Khim.Fiz., 1985, 4, 56. J.Wagner, J.Bendig, and D.Kreysig, J.Prakt.Chem., 1984, 326, 747. J.Wagner, J.Bendig, and D-Kregsig, J.Prakt.Chem., 1984, 326, 757. P.K.Sharma and R.N.Khanna, Monatsh.Chem., 1985, 116,353. R.Nakagaki, M.Hiramatsu, T.Watanabe, Y.Tanimoto, and S.Nagakura, J.Phys.Chem. , 1985, 89, 3222. A.K.Singh and T.S.Raghuraman, Tetrahedron Letters, 1985, 26, 4125. H.Garcia, S.Iborra, and M.A.MBiranda, Heterocycles, 1985, 23, 1983. V.T.Ramakrishna and J.Kagan, J.Org.Chem., 1970, 35, 290. L S Trifonov, A.S Orahovats , R Prewo , J .H.Bieri, and H Heimgartner, J.Chem.Soc.Chem.Comm., 1986, 708. Y.T.Park, H.C.Yun, S.R.Do, and Y.D.Kim, Taehan Hwahakhoe chi., 1985, 29, 441 (Chem.Abstr.,*, 68 329). T.Sakurai, H.Yamamoto, S.Yamada, and H.Inoue, Bull.Chem.Soc.Jap.,

..

.

.

.

1985, 58, 1174.

187.

T.Sakurai, H.Sukegawa, and H.Inoue, Bull.Chem.Soc.Jap., 1985, 58, 2875. N.Kamigata, S.Hashimoto, M,Kobayashi, and H.Nakanishi, Bull.Chem.Soc.Jap., 1985, 58, 3131. X.Lei, C.E.Doubleday, M.B.Zimmt, and N.J.Turro, J.Amer.Chem.Soc.,

188. 189. 190.

A.Albini, E.Fasani, M.Moroni, and S.Pietra, J.Org.Chem., 1986, 51, 88. F.D.Saeva, B.P.Morgan, and H.R.Luss, J.Org.Chem., 1985, 50, 4360. H.Sakurai, H.Yoshida, and M.Kira, J.Chem.Soc.Chem,Comm., 1985, 1780.

185. 186.

1986, 108,2444.

5

Photo-reduction and -oxidation BY A. COX 1

Introduction

Reviews

have appeared of the solid-state dimer isation of

the photooxidat ion of sulphur compounds,

thiones,

photochemistry,

thiocarbonyl

the DCA sen8 it ized photooxygenat ion of olef ins,

and of the role of intersystem crossing steps in singlet oxygen chemistry. Redu ction of the Carbonvl Grouq

2 Mutual

effects

of

nuclei

on

proton

CIDNP

formation

in

benzophenone photoreduct ion using var ious hydrogen donors such as cyclohexane, observed.6

aliphatic

alcohols

and

triethylamine have

been

The pH dependence of the lifetime of the Norrish type

I I biradical derived from y-phenylbutyrophenone has been studied from which it seems that biradical lifetimes may be determined by several

subtle

and

finely balanced

Alkyl

factors.

phenyl

ketones of the type PhCOCRzCHzRo (R=H, RI-Me, Bu; R-R'-Me) been absorbed on to zeolites NaA, Nay, NaX, Na-Mordenite

intermediate

is

favoured

cyclobutanols by more than 50:l. permitting are

greater

c 1.

mobility,

(HOCH,) ,CO,

MeCOCHMeCH,OH

,

and

On Silicalite, fragmentation of the

Silicalite and photolysed. biradical

have

cyclisation

to

However, on Nay, a zeolite

f ragmentat ion-cyclisat ion rat ios

MeCOCHMeOH,

MeCOCH,CMe,OH

over

,

and

MeCOCMe,OH, MeCO (CH, ) ,OH,

PrCOCHPrOH I have

been

irradiated in heptane or PrCN and the a-hydroxyketones found to decompose by a Type I mechanism. by

H-0

intramolecular

The p-hydroxyketones decompose

H-abstraction 338

and

reactions

of

the

IIIi5: Photo-reduction and -oxidation resulting biradicals intramolecular H

.'

An

339

2-quinonoid intermediate resulting from

abstract ion has

-O-substituted 2-nitrobenzylic

been

observed

for

several

compounds in THF solution. In 8ome

cases, both the triplet excited state and the 2-quinonoid are observed at early times and the p-quinonoid intermediate is formed from the singlet excited state at a rate much faster than triplet decay.1°

A

further report of the photocyclisation of

-o-tert-butylbenzophenone s-hydrogen existing

abstraction in

a

accounts for the very observed,

conformation

in

ideal

terms €or

rapid tr iplet the

compound

internal

hydrogen

of

abstraction, and suggests that this may represent tunne1ling.l' Details of the photoenolisation reactions of some acyclic a,p-unsaturated

ketones

have

appeared

and

competing

reketonisation mechanisms used to rationalise the wide variation in the photochemical deconjugation reactivity of enones. l2 A study of the photoenolisation of 4-benzyl-2-methyl-6-methoxy-5-phenylacetophenone has appeared13 and use of the photoenoliaation of 9-methylacetophenone as a synthetic tool has been investigated. l4 Photoenolisation of the chlorine

containing

compound

2,5-Me,C,H3COCHMeC1

2,6-dimethylindan-l-one, 5,2-Me(MeOCH,)C,H,COEt,

and

2,5-Me,C,H3CHMeC0,Me.

gives

2,5-MezC,H3COEt,

The first two products arise by

H

abstraction followed by C1 loss, and the latter two from initial C1 loss.15 (3-MeCoH,CH0 but not o-MeC,H,COMe

photoenol in var ioua gas matrices.

is observed to give a

2,5- and 2,4-MezC,H,CHO

also

produce enola, and it is concluded that the matrix environment, by

imposing

conformational constraints on

intermediates and

starting materials, can determine the course of reactions-l6 A

method of photocyclising a-(2-toly1)acetophenone dissolved

Photochemistry

340 in small crosslinked polymer beads has been described.

Despite

the high internal viscosity of the beads, the efficiency of this intramolecular photocyclisation is not impaired and the procedure may be

useful for

carrying out

a variety of

photochemical

reactions by means of solar radiation.l7 Some aliphatic and alicyclic ap-unsaturated nitro compounds are also reported to undergo

a

light-induced

E o s in-sens it ized

intramolecular

photoreduction

l-benzyl-l,4-dihydronicotinamide

of

cyclisation.l8 benz i 1

with

involves participation of both

an excited triplet state and an unquenchable excited singlet state; initiation seems to occur by electron-transfer.I9 Interest continues to be shown in photodeconjugation reactions and a study has been reported of the synthetic utility of adding base. ap-unsaturated

esters

RCR' :CRZCOzEt(R=Ph,

RI-Me,

R=R'=R2=Me; R=Me, R1=Rr-H; R=R2-Me, R1=H), Me,C:CHCO,Mej all

(2)

of

inefficiently &-unsaturated Aliphatic

which are

undergo

found

to

photochemical be

efficiently

The RL-H;

(1), or

deconjugation converted

to

isomers in the presence of 1,2-dimethylirnidaz0le?~

thiols

have

been

observed

to

catalyae

the

photoreduction of aromatic carbonyl compounds having a lowest '(nn*) mines.

state by

primary,

secondary, and

The mechanism involves abstraction by an aminyl radical

of H from

S

of the thiol, followed by abstraction of H from the Ca

of the aminyl radical by the thiyl radical. in

tertiary aliphatic

competition with

d isproport ionat ion

of

These processes are ketyl and

aminyl

radicals which have a retarding effect.21 A time-resolved ESR investigation of the photodecomposition of dibenzyl ketone in micellar solution has revealed the existence of a CIDEP effect which

is

cons istent

with

phenacyl-benzyl

radical

pair

lIIL5: Photo-reduction and -oxidation interactions, but interaction.

34 1

little

if

any

benzyl-benzyl radical pair

The micelle thus s e e m to be acting as a "super

cage" which allows strong interactions between both initial and subsequent geminate radical pairs. 22 The intramolecular hydrogen abstraction of tetradecyl anthraquinone-2-carboxylate in aerated 1,1,2-trichlorotrifluoroethane has been found to show a magnetic

field

effect.

This

is

attributed

to

reduction

of

the

tr iplet-singlet intersystem crossing rate which in turn brings about

a

reduction

application of

in

spin

the

cage product yield.23

trapping

to

the

study

of

The a

first

magnetic

field-dependent photochemical reaction has been demonstrated in the case of the photoreduction of naphthoquinone in SDS micellar solution.24 The role of micelle-bound L-ascorbic acid in the photoreduct ion of micelle-solubilized 2-acetoxymethyl-9,10-anthraquinone has been studied and it has been found that only those L-ascorbic acid molecules directly associated

with

the

nonionic

micelles

are

involved

in

photoreduct ion. 25 Complex format ion between exc ited z inc ( I I ) m - t e t r a k i s [ 1-( 3-sulphonatopropyl)-4-pyr idiniolporphyrin

and

anthraquinone-2,6-disulphonate leads to quenching by the quinone

acceptor and -its reduction26 and quinones such as dutoquinone and sodium ant.hraqu inone-2-su 1 phonat-a can be photor educed to their radical anions in a propan-2-01 water mixture in the presence of triethanolamine and eosin Y.27

The effect of the nature of

reagents and solvents on the rate of photoreduction of 2-quinones in the presence of aminee has alao been discuesed, and the relative

rate

constants

found

to

increase

with

increasing

electron-donor ability of the m i n e and electron-acceptor ability of

the

gu inone. 28

Radical

intarmed iatee, obtained

in

the

Photochemistry

342 of

photor educt ion

2,6-dimethyl-y-pyrone

and

y-pyrone-2,6-dicarboxylic acid and its anion have been identified

by ESR measurements.29 3

Reduct ion of N itroaen-containina COmDOUndS

Irradiation of methyl viologen in the presence of simple dicarboxylic or polycarboxylic acids brings about their reduction by a photoinduced electron transfer process.

This depends upon

the appearance of a long wavelength absorption associated with viologen carboxylate ion-pairs, the medium pH, and the excitation wavelength.30 In SDS reversed micelles the benzophenone ketyl radical is found to reduce methyl viologen at a rate which is leas than that observed in their absence, and this is thought to be a consequence of

the

lower rate of

quenching of

benzophenone

triplets by the alcohol medium.31 The same authors also report the effects of salts on the methyl viologen reduction rate in micelles and interpret the results quantitatively by an equation for the second approximation of the Debye-Htckel theory.3z It has also been

suggested that

eosin-sensitized photoreduction of

methyl viologen by di-Na EDTA in micelles in the presence of anthracene may serve as a model for photosystem I in a

SDS

micellar

system

containing

triethanolamine and

In zinc

tetraphenylporphyrintrisulphonate, the rate of photoreduction of

methyl viologen reaches a constant value: this is explained by depr ess ion of

complexation between the por phyr in and methyl

~iologen.~*Methylene blue has also been photoreduced in SDS micelles using 10-dodecyl(acridine orange) (DAO')

as sensitizer.

Singlet-singlet and triplet-triplet energy transfer from DAO' to

MB'

and electron transfer from triplet DAO' to MB'

to

be

important primary

processes.35

were all found

Isopropanol has

been

IIII.5: Photo-reduction and -oxidation

as

described

an

343

efficient

anthraquinone-2-eulphonate

reagent

sens it ized

for

the

sodium

of

methyl

reduct ion

v i ~ l o g e nand ~ ~ photochromism of the crystalline viologen (3) has been

attributed

to

the

formation

of

radical

cations,37

Irradiation of methyl viologen containing tetraphenylporphin or various metal derivatives as sensitizer, and EDTA as electron donor, induces its reduction.38 Net viologen reduction has been observed on

excitation of

the CT

complexes formed between

methylviologen and electron donors such as aniline, aniline derivatives, and

naphthalenes,

and

the

yields

of

electron

transfer are dependent on the excitation ~avelength.~’A laser flash photolysis study has been carried out on the photoreduction of the lumiflavin triplet state in the pH range 3-14 using various donors and only one electron equivalent transfer was found to be significant.

However, several secondary reactions

were observed including back reaction to starting materials, transfer

of

a

second

disproportionation

electron the

of

from

donor

to

flavin,

f lavosemiquinone

and

radical.4o

Photochemical deoxygenation of triphenodioxazine y-oxides has also been descr ibed.41 A singlet state-dr iven photogalvanic cell based

on

chloride

the

photoreduct ion

(oxonine)

by

of

Pe( I I )

3,7-diaminophenoxazinylium

has

been

descr ibed42

and

g-arylidenamines have been reduced to the corresponding m i n e s by irradiation in benzene solution under nitrogen.

The reaction

also occur8 in the solid state, and a two-phase system has been successfully tested far recycling an NADH model for photoreduction of &arylideneanilines been

used

as

using sunlight. 43 Aromatic aminea have

sensitizers

for

cls-5,6-dihydroxy-5,6-dihydrothymine

the in

photoreduction aqueous

of

solution;

Photochemistry

344

2x-

( 3 ) X = 4-MeC6H,S03-,

BF4'

C02Me

Qd

C02Me

O Me w Me he

M

e

@io2Me @Jo2Me

8

C02Me

CO2Me (6)

(7)

345

IIIL5: Photo-reduction and -oxidation 6-hydroxythymin-5-yl radicals are involved as intermediates. 44 4

Miscellaneous Reductions

HMPT has been reported to be a useful solvent for the photoreduction of esters. For example, perf luor inated esters give def luor inated esters as well as the corresponding alkane45 ,46 and alkyl esters give alkanes alone,47 in processes which involve electron-transfer

from

HMPT

to

RO,SMe(R=S-cholesten-3p-y1,

ester.

Methanesulphonates,

4,4-dimethyl-3p-cholestanyl,

3~-cholestanyl, n-nonyl) can also be photoreduced in the same solvent .48 Colloidal platinum catalysts have been prepared by hydrogen- and photo-reduction of

chloroplatinic acid

in the

presence of surfactants and these have been found to be highly active

catalysts

Acetone-sensitized

for

hydrogenation

photolysis

of

1,2,3,4-,

1,2,4,5-tetrachlorobenzene at htrr>285 nm

reductive dechlor inat ion.

’*

of

olef ins. 49

1,2,3,5-,

and

leads principally to

In the presence of certain dyes,

3-methyl-2-aryl- or alkyl-2,3-dihydrobenzothiazoles are reported to be capable of reducing activated halides, sulphonium salts?

and certain pyr idiniurn salts under completely neutral conditions. An electron transfer chain as established in similar reactions of

1,4-dihydropyridines is probably involved. 51 Aqueous solutions of 9-phenylxanthen-9-01 undergo adiabatic photodehydroxylation and as such are the first reported example of this new class of adiabatic photochemical reaction. 52 Photoreduction of water to hydrogen has been catalysed using an aqueous suspension of poly(_p-phenylene) in the presence of Et,N as electron donor, and is the first report of hydrogen evolution photocatalysed by an

organic semiconductor

in sacr if ic ial systems. 53

The

use

of

inclusion complexes of hydrophobic viologens to protect the

Photochemistry

346

pyr idinium moiety from hydrogenation in photochemical hydrogen formation has been descr ibed. 54 Singlet Oxvaen

5 Singlet

oxygen

has

been

produced

non-transition metal oxides such as A1,0,

by

irradiation

of

and MgO in an oxygen

atmosphere. A n energy-transfer mechanism involving 0 and excitons on the metal oxide surface appears to be ~perating.’~A new series of Rosc Bcngals has been described in which the Rose Bengal molecules may aggregate.

The quantum yield of singlet

oxygen formed using such a sensitizer is reported to be dependent on the number of Rose Bengal units attached to the polymer chain. 5 6

Thermal decomposition of

tr iphenylphosphite ozonide

leads to an efficient generation of singlet oxygen with yields of 70-903

depending on reaction conditions.57 Similarly, thermal

decomposition of

1,4-dimethylnaphthalene endoperoxide in CC1,

also leads to expulsion of O,( Microheterogeneous ox idat ion ref era

to a photosens it ized

ox idat ion whose ef f ic iency is enhanced beyond that of d if f us ion

control by the covalent bonding of a sensitizer to a ligand.

A

paper has appeared citing several examples of this phenomenon and suggest ing that chemical organiaat ion in a photochemical system must have a significant effect on the rate of a photosensitized process.59 Singlet oxygen luminescence has been used as a probe of the stilbene triplet surface6’ and a quantum mechanical study of mechanisms of photosens itizat ions, luminescence and quenching of O,(‘ag)

in solution has appeared.

The MINM3/3 method is used

to evaluate the collis ion- induced trans it ion moments for the collision complexes between ethylene and 0, and it is found that during the collision there ia an appreciable strengthening of the

IIIt.5: Photo-reduction and -oxidation S,-T, interconversion. transition

moment

347

This is caused by a large rise in dipole

during

the

collision.61

Singlet

oxygen

generated in the flash photolysis of 0, can be quenched by atomic oxygen.

A two-step mechanism involving formation of a transient

excited 0; complex has been suggested.62

c-Phenyl-N-tert-butylnitrone primarily by

a

is reported to deactivate

reversible electron-transf er

O,('%)

mechanism63 and

quantitative aspects of the quenching of a l l - w - r e t i n o l

by

.

singlet and tr iplet oxygen have been described 64 Intermolecular perturbation and elucidate

the

electron-rich

CI

calculations have

attacking olefins.

mode8 The

of

been

O,('a,)

crucial

interactions, exciplex formation, and

carried out on

roles

allylic

played

to and

by

CI

ionic dissociation are

emphasised.65 Reaction of singlet oxygen with (lB,4E)- (lE,43)and (1~,4~)-1,4-di-tert-butoxybuta-l,3-diene leads to dioxetana rather than to the expected (4+2)-cycloadducts. Two mechaniama, namely a concerted 2,

+

2, cycloaddition and a ptocesa involving a

zwitter ionic intermediate have been advanced, and solvent effect and kinetic data presented in support of the suggestions.66f67 The chemilumineacence intensity at A-1270 for the H,O, reaction and corresponding to the

'A,-,

.)

+

NaOCl

c i transition of 0, ha8

been measured as a function of the concentration8 of H,O,

and

NaOCl. 68 6

Comr>ounds

Oxidation of -tic

Photooxidation of

C,,

and

C,,

studied in the NO-air

C,

cycloalkanes has been

and as part of an investigation

of the chemistry of small ring compound8 the

cyclopropylidenecycloalkane8,

cyclopropylideneadamantane

cyclopropylidenecyclohexane

have

been

oxidised

using

and

singlet

Photochemistry

348 oxygen.

Mechanisms of,

processes

have

been

and

possible

discussed.70

It

intermediates is

also

in these

reported

that

2,3-dimethylbut-2-ene undergoes a novel photooxygenation in an oxygen matrix when excited at the contact charge-transfer band by W-vis

light.71 Some simple alkenea have been oxidised using

various cyanoanthracenes as sensitizer ,72 a reactivity order of singlet oxygen towards conjugated dienes and double bonds has appeared,73 and a study made of the photosensitized oxidation of

.

subst ituted oleates 74 Sen8 it ized photooxygenat ion of thujopsene proceeds by a singlet oxygen mechanism but in the presence of added biphenyl electron transfer occurs to give (4), presumably by

a

radical

cation ~ n e c h a n i s m . ~Cyclic ~

olefins

have

been

photooxidised using FeC1, and the reaction has found application in the synthesis of exo-brevicomin. 76 Detail8 of the singlet oxygenation of

COT

and

of

its methoxy,

methyl,

and

phenyl

der ivat ives ,77 and of the sen8 it ized photooxygenat ion of methyl substituted

1,2-diphenylcyclobutenes have been reported. 78 In

these latter reactions methylene blue sensitized photooxidation of

1,2-diphenylcyclobutenes

the

to

ring

functionalised

cyclopropanea is thought to occur by initial [4+2] cycloaddition to the

styryl

unit

to give

an

endoperoxide.

The

comstock

mealybug pheromone has also been synthesised by an oxidative procedure starting from 2,6-dimethylhepta-2,5-diene. 79 a-Pinene has been photooxidised*O and a study of the competition between the ene reaction and a 1,4-cycloaddition of O , ( ' h g ) l-vinylcycloalkenea

@=5-10,12)

and

in a series of

isopropylcycloalkenes

(IJ-6-8) described.81 Methyl 5,8,11,14,17-eicosopentaenoate gives

only

dihydroperoxide

methylene

isomers

blue-sensitized

as

the

secondary

photooxidation. 8 2

products Two

on

dimer ic

1111.5: Photo-reduction and -oxidation

epidioxides

are

formed

349

on

reaction of

l-~-butylcyclohexa-1,3-diene

Ph,C+EF,

and

83

sen8 it ized

triplet

oxygen with

in a phOtOpKoCeS8 catalysed by

photooxygenat ion

of

[2 , 6 ]

the

spirocycloheptatriene (5) with singlet oxygen gives (6) and (7). This and other work suggests that (5) does not equilibrate with .its

valence

Stereoselect ive

isomer. 84

photooxidat ion

of

isocembrol at the C, double bond gives a aeries of epimeric d

and ant itumour -act ive photochemical ox idat ion products of

provitamin D have been prepared. 86 Photosensit ized oxygenat ion of

us ing var ioua

3,4-dihydro-2H-pyran

cyanoanthracenes

has

been

investigated. The mechanism involves electron tranafer between the excited singlet state of the sensitizer and the substrate, followed

by

reaction

of

singlet

oxygen

as

the

reactive

intermediate in subsequent proces8es. 87 Two stable hydroperoxides are

formed

in

the

photooxygenation acid

3,4-dihydro-6-methyl-2H-pyran-5-carboxylic

transformations

which

of

give

The mechanism

intermediates. 88

of

other

ethyl

of ester,

monooxygenated

the chain process

forming

hydrogen in the photooxidation of formaldehyde and the effect of 89 temperature on the photooxidation of formaldehyde in oxygen-lean atmospheresg0 have been described and a mechanistic study of the photooxidat Ion of a-diketones involving interact ion of tr iplet carbonyl

compound

with

oxygen

has

appeared.

Two

reaction occur competitively, the formation of Oz('%)

types

of

by energy

~~ transfer to 0, and the addition of 0, to triplet d i k e t ~ n e .The effect

of

reactivity

substituents, of

the

photooxygenat ion

solvent,

and

temperature

zwitterionic peroxides of

arising

2-(methoxymethylidene)-

on

the

from

the and

2-(phenoxymethylidene)adamantane and other enol ethers have been

Photochemistry

350 descr ibed92,’93 and methionineg4 general

the results of. photooxidation

studies on

and ketoglutar ic acidg5 have also appeared.

method

for

the

of

synthesis

a-keto

derivatives

A

of

lactones, esters, amides lactams and ketones and involving the dye-sens it ized photooxygenation of enamino carbonyl systems has appeared .96

7

Oxidation of Aromatic COmDOUndS

The 9,lO-dicyanoanthracene sensitized 1,4-dimethylnaphthalene media

gives

the

photooxygenation

is solvent dependent and endoperoxide

of

in non-polar

exclusively.

Mechanisms

incorporating a radical ion pair and a singlet exciplex have been proposed

to

explain

these

solvent

effects .97

W o

reaction

channels are found to be open to the photoexcited 1,4-bridged endoperoxide of 1,4-dimethoxy-9,10-diphenylanthracene, both of which start from upper excited states.98 Only excited oxygen and Photolysis of

the ground state parent anthracene are formed.

dipotassium anthracen-9,lO-ylene disulphate in water or ethanol gives anthraquinone and anthrone, and in deoxygenated solution 9,lO-anthracenediol intermediate.99

has

been

Studies

benzophenone-sens it ized

detected

on

ox idat ion

the of

as

a

long

mechanism

lived

of

the

9-phenylxanthene

with

oxygen us ing inhibitors, quenchers, and a s inglet sent3 it izet , suggest that the reaction occurs by a type I non-chain processloo and

photooxygenat ion

of

the

glycosylf ur an

(R-2,3-O-isopropylidene-p-D-erythrofuranot3yl,

( 8)

,

R’=CH (0H)Me)

followed by reaction with hydrazine gives the

erythrofuranosylpyridazine (9) (same R, RZ=CH(OH)Me) .lol Electron transfer photooxygenat ion of sensitized

by

9,lO-dicyanoanthracene

gives

Ph,C-C-CPh,

in MeCN

benzophenone

and

ML5: Photo-reduction and -oxidation

351

Replacement of MeCN by acetone as solvent leads to

polymer.

increased yields of product in a transformation which occurs v i a Ph,C(OOH)COC(OOH)Ph, Ph,&C(OO-) :CPh,

and

formed

as

an

intermediate

from

tetraphenylcyclopropane.Io2 Electron-donor

1,2-diazylcyclopropanes undergo an ef f icient photooxygenat ion to give 3,5-diaryl-l,2-dioxolanes in polar

solvents and

presence of

These processes are

DCA

as

electron acceptor.

in the

accelerated by addition of some aromatic hydrocarbons and metal salts but

are

DABCO. Io3

completely quenched by Cosens it ized

addition of

Et,N

and

photooxygenation

of

1,l-diphenyl-2-vinylcyclopropane in oxygen-saturated MeCN with

biphenyl

and

9 , l O -d icyanoanthracene

3,3-diphenyl-5-vinyl-l,2-dioxolane,

Ph,CO,

gives

and buta-1,3-diene.

1,2-Cycloaddition with singlet oxygen is not obaerved.lo4 A n investigation of the role of cosensitizers such as biphenyl in 9,lO-dicyanoanthracene-sensitized

cis-trans

reactions

has

appeared."'

a-and

Photoisomerisation and photooxygenation of

tzans-1,2-bis(4-methoxyphenyl)cyclopropaes

are

sensitized

by

9,10-dicyanoanthracene, and the efficiencies of these reactions are enhanced by the addition of inorganic salts such as LiBF, and Mg( CLO,)

,. lo6

The

same

authors

have

also

discussed

the

photochemical oxidat ion of styrylcyclopropanes in the presence of Cu(BF,),. lo7 Unsaturated substrates such as PhChCR Ph,C=CPh,,

w-PhCH-CHPh,

2,3-diphenyldihydro-l,4-dioxine

(R-Ph,H),

PhCMe*CH, , undergo

oxidation

and using

2,4,4,6-tetrabromocyclohexa-2,4-dienone as electron acceptor in a process in which the intermediate radical cation reacts with 0,

through a

radical cation chain mechanism.lo8 DCA-sensitized

photooxidation of 1,4-diphenylbuta-1,3-diene

in MeCN gives an

Photochemistry

352 Me

R

Me

(11)

Me

(14)

Me

R’

1115: Photo-reduction and -oxidation

353

epoxide, ozonide, the cleavage products PhCHO and PhCH-CHCHO, and the endoperoxide. transfer

process

The mechanism appears to be involving

O;.lo9

Ce( IV)

an electron

will

induce

the

photochemical side-chain nitroxylation of alkylbenzenes probably via the nitrate radica1,l.l'

and Fe(I1I) is reported to increase

the rate and quantum yields of photoinitiated hydroxylation of salicylic acid by

Some f lavin analogues have been

HzO,.

reported to catalyse the photooxidation of p-methylbenzyl alcohol by oxygen in the presence of Mg2+ or Znz+ in acetonitrile.l12 Electron transfer photooxygenation of 2,3-diaryl-2,3-dimethyloxiranes

in the presence of DCA gives a

mixture of cis- and grans-ozonides and the observations have been interpreted In terms of the addition of singlet oxygen as a dipolarophile to intermediate carbonyl ylides. '13

Dye-sensitized

photooxygenation of PhNHCSNHPh gives the corresponding urea which ( 1141 undergoes photorearrangement to 2-H,NC,H4C,H,NHCHO-2 and sensitized photooxygenation of isorhamnetin-4',5-dimethyl ether is reported to lead to the depside (10).l15

. . ComDoun& Oxidation of Nitroaen-containina

B

It is reported that although enamines (11) and (12) undergo photosens it ized

ox idat ion

in toluene to give the ox idat ion

product normally expected, in methanol the pr inc ipal products are the

oxetans

( 13 )

and

( 14)

r espect ively .116

Photochemical

oxidative dehydrogenation of cyclic enamino diketones of the 8-azasteroid ser ies ha8 been described.'17 PhCOCHPhNR,

Compounds such as

(NR,-morpholino or piperidino) and PhCH(OH)CHPhNR,

(NR,-morpholino)

which

contain potentially

labile C-C

bonds

adjacent to the m i n e have been prepared.

Irradiation in the

presence

electron

of

Ru[4,4'-COZEt(bpy) ],(PF,),

as

acceptor

354

Photochemistry

induces C-C bond cleavage and radical formation.

Methylene

blue

sensitized

photooxidation of

ser ies of

a

Schif f bases

-

derived from p-substituted benzaldehydea and 3-alkoxycarbonyl- or 3-acyl-4-amino-5-aryl-2-methylpyrrole8 can proceed via one of two

reaction channels.

These involve fission of the pyrrole ring to

give enamidonitriles and rearrangement to 4-aroyl-2-aryl-5-hydroxy-6-methylpyr imidines .'I9 C,F ,CH=NC,F

,

has

been

peracetic acid or H20, [C,F,NHCH(C,F,) sen8 it ized

ox id ised

C,F ,CH (OOH)NHC,P

,

us ing

in CHC1, and which on irradiation gives

]202.120 Low

temperature

photooxygenat ion

Me,C(OOH)N:NH

to

The Schif f base

of

in l o w yield.121

acetone

tetraphenylporphyrin hydrazone

produces

Irradiation of acidic methanolic

solutions of 2,4- and 3,4-pyridinedicarboxylic acids under an oxygen atmosphere causes methoxylat ion at the w p o s it ion of the

r ing,

pyridine

whereas

a-methoxylation occurs. decrease

a

under

nitrogen

atmosphere

It has been suggested that the observed

in methoxylation at

the a-poeition

is

not

due

to

quenching of the excimer by oxygen but rather to participation of another excited complex.

A possibility here may be an excited

terplex consisting of two molecules of protonated heterocycle and

of

one

oxygen. 122

Base- induced

oxygenat ion

of

the

3,6-disubatituted pyr idazines (15; R-H, Ph; R'=RZ-OH, C1, OCMe,, OMe;

R1-C1, R'-OCMe,)

using

MesCOK

in

Me,SO

proceeds

with

chemiluminescence. This transformation may be a suitable model for

lum ino1

chemiluminescence.123

FeC1,-H,O-catalysed

photooxidation of the benzylpyrazine (16; R-R'-H, RZ-Ac) leads to (16: RR'=O, R'=Ac;

R-H, R'-OAc,

OH, RZ-Ac), a compound which on

hydrolysis gives products (16; Rz=H) related to the biologically active

metabolite

septor ine.

4( 1H)-Quinolinones

undergo

IlIf5: Photo-reduction and -oxidation

355

-

M e O e C R R '

Me Me

Me Me

(17) OOSiMe, 1 02

Me

Me CN

R = Me, R' IMe,CH R=H,R'=Me Scheme 1

Photochemistry

356 oxidative

cleavage

to

the

2-acylaminobenzoic

acids

on

dye

sensitized photooxygenation in MeOH-aq NaOH, and in some cases to the derived useful

2-aminobenzoic

route

to

derivatives .12'

This may be an alternative

acid.

nuclear

substituted

anthranilic

acids

and

Acr idine and Acr idine yellow are decolour ised in

the presence of Fe(II1) on irradiation at h>360 nm in a process brought about by Ht) radicals. This process has found use in the determination Qu inolines

of have

indole-3-acetic

micro

amounts

been

prepared

acids

and

conversion through N-1-C-2

of

iron,

by

F-and

photooxygenat ion

indole-3-acetaldehydes

and

of this

fission by singlet oxygen may have

significance as a model experiment for the biomimetic synthesis of

alkaloids. 127

quinine

1,1,3,3-tetramethylindan-2-one

Photooxygenation

of

triphenylphosphazine leads to a

carbonyl oxide intermediate and also to chemiluminescence via a zwitter ionic intermediate.

The same workers also report the

first direct observation of the 3-phospha-l,2-dioxa-4,5-diazine (17) by high field 'P

NMR.129 Flash photolysie of lumif lavin in

the presence of C(N02)+ leads to a transient assigned as the one-electron oxidised radical130 and tr imethylsilyl nitr ile is

to

reported

be

a

trapping

intermediates (Scheme 1) oxygen

in methanolic

inc lud ing

agent

for

dipolar

peroxide

Benzimidazole reacts with singlet

solution to give

2,4'-bibenzimidazole,

a

range

of

products

2 , 5 ' -bibenzimidazole

benzimidazolone and 2 (3H)-oxobenzimidazole. 132 The steady state photochemical behaviour of N_,N,N_:N_'-tetramethylbenzidine (TMB) in SDS anionic micelles and on the effect of protonation on the photoionisation of TMB has been

of

diphenylamine

by

hydroxyl

and the oxidation radicals

investigated. 134

IIIl5: Photo-reduction and -oxidation Photooxygenation

of

357

the

pos it ions

benzylic

var i o u s

of

nitroaromatic compounds has been achieved and interpreted in terms of

the greatly enhanced

C-H

acidity of

the benzylic

methylene hydrogens on photochemical excitation,135 and singlet oxygen

is

thought

photodegradation

of

to

an

play

methyl

orange

important in

role

micellar

in

the

solution. 136

N-Vinylcarbazole has been photooridised in a functionalised oil-in-water microemuls ion using bis (hexadecyltrimethylarrpnonium) peroxydisulphate

in

an

electron

transfer

process

The

one-electron photooxidation of E-ethylcarbazole in the presence of

has

CC1,

been

discussed.138

photooxidised in methanol under

(-)

-p-Narcotine

has

been

air,139 and a synthesis of

(*)-sibiricine from the corresponding protoberberine using a photooxygenation procedure has been developed.

9

Mifmllaneous

Oxidation@

Oxidation of t-butanol by benzophenone triplets leads to a number of side products including formic acid, acetone, and at long radiation t imes, Norr ish type-I fragmentation products of benzophenone.141 Laser-induced n-butane and

CO

vibrational photooxidation

of

has been studied142 as has the photooxidation of

1,5-dithiacyclooctane using benzophenone.143 This latter prOC888 involves a two-electron relay and a radical cation intermediate. Radical

anions

have

been

prepared

by

two

complementary

procedures, photooxidation of an electron richer species as for example in the case of tetrabenzocyclooctatetraene dianion, and light-induced electron transfer from a stable carbanion, such as

,'F

to a neutral compound.144 Diacussione have appeared of the

photolysis of m e t h a n e t h i ~ l l and ~ ~ of dimethyl dieulphide in the presence of oxygen,146 and rate constant8 for the photooxidation

Photochemistry

358 of R,S

(R-Me, Et, Pr, CHMe,, determined. 147

been

Bu, CH,CHMe,,

Fluorescence

CMe,)

by O,('A~) have

quenching

processes

of

9,lO-dicyanoanthracene by organic sulphides have been examined and an assessment made of the evidence supporting an electron transfer mechanism. 148 Photooxidation of

the

sodium salt

4,4'-dimethyl-6,6'-dichlorothioindigobissulphonate

of

leuco dye sol

in microheterogeneous media leads to replacement of both OS0,Na groups by

0 groups, 149

and

photooxidat ion of

thiones gives the corresponding reaction

occurring

chromophore.

by

@-unsaturated

ketone as the only product,

attack of

O,('%)

on the thiocarbonyl

Selected and stereospecif ic hydroxylation a to

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f i t

6

Photoreactions of Compounds containing Heteratoms other than Oxygen BY S.T. REID 1

N i t r o g e n - c o n t a i n i n g Compounds

R e a r r a n g e m e n t s . - Examples o f L , E - p h o t o i s o m e r i z a t i o n i n i m i n e s h a v e a g a i n b e e n r e p o r t e d . The p h o t o i s o m e r i z a t i o n s o f m e t h a n i m i n e ' a n d o f f l u o r i n a t e d m e t h a n i m i n e s ' have b e e n examined a n d t h e s t u d y o f t h e p h o t o i s o m e r i z a t i o n o f p r o t o n a t e d and unprotonated imines of 9-*-, ll-%-, 13-*-, and a l l t r a n s - r e t i n a l s h a s a t t r a c t e d a t t e n t i o n i n v i e w o f t h e c o n t i n u i n g i n t e r e s t i n t h e mechanism o f t h e v i s u a l p r o c e s s .3 Evidence from f l a s h p h o t o l y s i s s t u d i e s i n d i c a t e s t h a t t h e p h o t o i s o m e r i z a t i o n of t h e E-hydrazone (1) t o t h e A-hydrazone ( 2 ) may p r o c e e d by way o f a n a z o i n t e r m e d i a t e . 4 Reversible 2,lj-photoisomerization h a s been r e p o r t e d i n 2 , 2 ' dihydroxy-1 - n a p h t h a l d a z i n e , and s h o r t - l i v e d phototautomers have been d e t e c t e d on i r r a d i a t i o n o f t h e same n a p h t h a l d a z i n e ' a n d various salicylideneanilines. 6

'

The quantum y i e l d f o r t h e p h o t o i s o m e r i z a t i o n o f E - a z o benzene h a s been determined, and analogous c o n v e r s i o n s have been r e p o r t e d f o r 1- (phenylazo) -2-naphthols .8 F u r t h e r s u p p o r t f o r t h e i n v o l v e m e n t o f a n i n v e r s i o n mechanism i n s u c h t r a n s f o r m a t i o n s h a s b e e n o b t a i n e d f r o m a s t u d y o f 4-(dimethylamino)-4'-nitroazoS u r p r i s i n g l y , an o x i d a t i v e dimer i s t h e only product o f benzene.' i r r a d i a t i o n of 4-phenylazo-1-naphthol i n t h e p r e s e n c e of oxygen. 1 0 New p h o t o r e s p o n s i v e crown e t h e r s i n c o r p o r a t i n g a n a z o b e n z e n e m o i e t y h a v e b e e n p r e p a r e d . The b i n d i n g p r o p e r t i e s of t h e crown e t h e r ( 3 ) c o n t a i n i n g an i n t r a a n n u l a r 4-methoxyphenylazo s u b s t i t u e n t Photoa r e s i g n i f i c a n t l y a l t e r e d on E + L p h o t o i s o m e r i z a t i o n . l l 13 i n d u c e d a g g r e g a t i o n changes"-and photocontrol of s o l u b i l i t y have been observed f o r poly(L-glutamic a c i d ) , and poly[N-(phenyla z o b e n z o y 1 ) - L - l y s i n e ] s i m i l a r l y shows p r o m i s e a s a p h o t o r e s p o n s i v e s y s t e m . l 4 New a z o b e n z e n e p h o t o r e s p o n s i v e c o m p l e x e s c o n t a i n i n g two i m i n o d i a c e t i c a c i d u n i t s o r e t h y l e n e d i a m i n e u n i t s h a v e a l s o been p r e p a r e d . 1 5 Examples o f p h o t o r e a r r a n g e m e n t a r i s i n g by a 4 ~ ie l e c t r o c y c l i c pathway have b e e n d e s c r i b e d . The low quantum e f f i c i e n c e s

368

IIIJ6: Photoreactions of Compounds containing Heteroatoms other than Oxygen 0

Ph

I

I

Ph

Ph

0Q+R

I R’ (5)

= 3 - , 4 -, =Me,R2= H

( 4 ) R’ = H, R’ R’

R’ = Et or CH=CH,

(6)

5 -, or 6 - M e

, RZ= H

(7)

369

370

Photochemistry

(0.01 - 0.07) r e p o r t e d f o r t h e p h o t o i s o m e r i z a t i o n o f a l k y l a t e d p y r i d i n e s ( 4 ) t o t h e azabicyclo[2.2.0]hexene.s ( 5 ) h a v e b e e n a t t r i b u t e d t o s h o r t - l i v e d s i n g l e t s t a t e s . l 6 The c o m p e t i n g LT4 + T 4 ] photodimerizations a r e believed t o involve preliminary association

v i a a s t r o n g d i p o l e - d i p o l e i n t e r a c t i o n r a t h e r t h a n hydrogen-bonded pairing. Stereospecific photocyclization of the diazepine (6) t o t h e t r i c y c l e ( 7 ) 1 7 and c o n v e r s i o n of t h e 4-pyrimidones (8) i n t o t h e diazabicyclo[Z.Z.O]hexenes t h e p h o t o h y d r a t e s (9) and ( 1 0 ) ( 1 1 ) on i r r a d i a t i o n i n a q u e o u s s o l u t i o n 1 8 h a v e b e e n r e p o r t e d . In a s i m i l a r f a s h i o n , t h e n o v e l 2,6-diazabicyclo[2.2.O]hexane-3,5d i o n e s ( 1 2 ) c a n be p r e p a r e d i n h i g h y i e l d by i r r a d i a t i o n o f t h e c o r r e s p o n d i n g p y r i m i d i n i u m - 4 - o l a t e s ( 1 3 ) i n a c e t o n i t r i l e ' and B-lactam d e r i v a t i v e s a r e o b t a i n e d o n i r r a d i a t i o n o f 3 - d e a z a u r i d ines." The h i g h l y s u b s t i t u t e d p y r i d i n e s ( 1 4 ) h a v e b e e n i d e n t i f i e d a s i n t e r m e d i a t e s i n t h e p h o t o r e a r r a n g e m e n t o f Dewar p y r i d i n e s ( 1 5 ) t o t h e i s o m e r s ( 1 6 ) ; 2 1 t h e same p y r i d i n e d e r i v a t i v e s ( 1 4 ) were s e p a r a t e l y c o n v e r t e d i n t o t h e i d e n t i c a l azabicyclo[2.2.0]hexenes ( 1 6 ) o n i r r a d i a t i o n i n c h l o r o f o r m . The mechanism o f t h e f o r m a t i o n o f Dewar s p e c i e s i n t h e s i n g l e t p h o t o i s o m e r i z a t i o n o f p y r i d i n e , p y r i d a z i n e , p y r i m i d i n e , and p y r a z i n e h a s been d i s c u s s e d . 2 2 P h o t o c h e m i c a l l y i n d u c e d IT e l e c t r o c y c l i c r e a c t i o n s o f t h e stilbene-to-dihydrophenanthrene t y p e a r e common i n n i t r o g e n c o n t a i n i n g systems. Oxidative p h o t o c y c l i z a t i o n of t h e s t y r y l - 1 , 3 d i m e t h y l u r a c i l ( 1 7 ) , f o r example, proceeds from t h e lowest e x c i t e d * s i n g l e t IT,^ s t a t e a n d a f f o r d s t h e n a p h t h a l e n e ( 1 8 j a s shown i n Scheme 1 . 2 3 , 2 4 A s i m i l a r s t r a t e g y h a s b e e n employed i n t h e s y n t h e s i s of two b e n z o [ l Y 2 - b ; 4 , 3 - b ] d i p y r r o l e f r a g m e n t s o f t h e p o t e n t a n t i - t u m o u r a g e n t CC-1065 . 2 5 An a n a l o g o u s e l e c t r o c y c l i z a t i o n h a s b e e n o b s e r v e d o n i r r a d i a t i o n i n b e n z e n e o f t h e y-methoxyimino-aB-unsaturated carboxamide (19) t o g i v e , a f t e r e l i m i n a t i o n of methanol, t h e f u s e d q u i n o l i n e carboxamide ( 2 0 ) . 2 6 P r o t o n a t e d 2-azabuta-lY3-dienes s i m i l a r l y undergo o x i d a t i v e p h o t o c y c l i z a t i o n t o 1 , l -diphenyl-3-arylisoquinolin-4-ones ,27 a n d t h e p h o t o c y c l i z a t i o n o f 1 , 2 , 4 - t r i a r y l p y r i d i n i u m c a t i o n s h a s b e e n shown t o p r o c e e d via d i h y d r o i n t e r m e d i a t e s . 2 8 y 2 9 More s u r p r i s i n g i s t h e r e p o r t e d c o n v e r s i o n o f t h e N-a-cyanoamine ( 2 1 ) i n t o t h e 2-0x0-1 , 2 , 2a,ll-tetrahydrobenzo[3,4-~]imidazolo[3,4-~]quinoline(22) o n i r r a d i a t i o n i n methanol i n t h e p r e s e n c e of potassium hydroxide and p o t a s s i u m i o d i d e ; 3 0 no s a t i s f a c t o r y e x p l a n a t i o n h a s y e t b e e n p r o p o s e d t o a c c o u n t f o r t h i s t r a n s f o r m a t i o n which h a s b e e n shown t o involve i n c o r p o r a t i o n of methanol.

IIIi6: Photoreactions of Compounds containing Heteroatoms other than Oxygen R'

R''N

-1

A \N

hv

(8) R' = F$= Me, R3 = M e or But R'

-$ =

(11)

, R3 = But

(CH,),

+

Rz\

N

H'

R3

(13)

R

= C0,Et

R'

RZ

R3

Ph

H

Ph

Ph

Me

H

Ph

Me

Me

Ph

Me

Ph

Me

SEt

Ph

or CN

(12)

371

372

Me \ 0A

Photochemistry

+

0

NI

Me

Me (17)

0

0

[OI

+---

Scheme

1

OMe

OMe h'V ___)

NEtz (19)

.1

-MtOH

IIIl6: Photoreactions of Compounds containing Heteroatoms other than Oxygen

hY, MeOH

KOH, K I

H H (21)

MeX)&o

Me0

hV

v NaBH,

(25)

A?

(26)

LQ H

hV

c

0 (27) Ar

=

Ph , o

p

(28)

- MeOC6H4, p - MeOC,H,,

- CIC,H,,

o r d -nclphthyl

373

374

Photochemistry

Novel synthetic applications of the photocyclization of enamides have been reported. Preparation of the fused quinolone (23) from the enamide (24) was achieved by photocyclization and subsequent elimination of a suitably positioned methoxyl group.31 Reductive photocyclization of enamides, usually carried out in the presence o f sodium borohydride, is of particular value in the synthesis of alkaloids. Cyclization of the enamide (25) to the furanoquinolizine (26), for example, has been employed in the synthesis of ipecac and heteroyohimbine alkaloids.32 2,3,9,10Tetraoxygenated protoberberine alkaloids can similarly be converted into 2,3,10,11-protoberberine alkaloids by a sequence of reactions which includes oxidative cleavage, reductive photocyclization in the presence of sodium borohydride , and deoxygenation.33 The stereochemistry of the lactam obtained by reductive photocyclization of N-cyclohex-1-enylbenzamide has been confirmed by a crystal structure determination of the Diels Alder adduct with maleic anhydride. 34 An unusual photocyclization has been observed in the bicyclic dienamides (27) and affords the spiro compounds (28) ;3s there is little precedent for this transformation and the precise mechanism is still uncertain. In contrast to this behaviour, monocyclic dienamides have been shown to undergo a photochemically induced 1 ,3-acyl migration. The reverse process, the electrocyclic ring cleavage of azacyclohexadienes, can also be effected photochemically. Evidence that ring opening of %-substituted 1,Z-dihydroquinolines proceeds from the lowest triplet excited state has been published. 36 The formation of homoadamantano [4,5--R


CH,S iMe

CHzS iMe h9

413

Photochemistry

414

d e s i l y l a t i o n h a s been o b s e r v e d on i r r a d i a t i o n of 9 - t r i m e t h y l s i l y l a n t h r a c e n e i n m e t h a n o l ,208 and e l e c t r o n t r a n s f e r p r o c e s s e s a r e involved i n t h e r e g i o s e l e c t i v e p h o t o a l l y l a t i o n of dicyanoarenes w i t h a l l y t r i m e t h y l ~ i l a n ea n~d~ ~ i n t h e photorearrangement of t h e t r i c y c l o h e p t a n e (234) t o t h e b i c y c l o h e p t e n e ( 2 3 5 ) . 2 1 0 Evidence s u p p o r t i n g a c o n c e r t e d [ l , 3 ] s i g m a t r o p i c pathway i n t h e n o v e l p h o t o r e a r r a n g e m e n t of 3-phenylprop-2-enylgermanes t o l - p h e n y l p r o p 2-enylgermanes h a s been d e s c r i b e d . 21 1 P h o t o r e a c t i o n s have a l s o been r e p o r t e d i n organophosphoru s , o r g a n o s e l e n i u m a n d o r g a n o b o r o n compounds. P h o t o c h e m i c a l l y i n d u c e d v a l e n c e i s o m e r i z a t i o n h a s been o b s e r v e d i n 1 , 8 - b i s ( p h o s phano)octa-1 , 3 , 5 , 7-tetraenes'l a n d a c y l p h o s p h i n e o x i d e s undergo p r e f e r e n t i a l a - s c i s s i o n t o g i v e phosphonyl r a d i c a l s on i r r a d i a t i o n i n s o l u t i o n . 2 1 3 p 2 1 4 P h o t o i n i t i a t e d a d d i t i o n of phosphorus t r i b r o m i d e t o d i m e t h y l a c e t y l e n e h a s been r e p o r t e d . 2 1 Irradiation of t h e s e l e n i u m - c o n t a i n i n g p y r a z o l o n e ( 2 3 6 ) i n t h e p r e s e n c e o f oxygen gave t h e b i c y c l e (237) a l o n g w i t h o t h e r p r o d u c t s o f p h o t o oxidation. The p h o t o d e c o m p o s i t i o n o f a z a b o r e t i d i n e s h a s been s t u d i e d , 2 1 7 and a n o v e l p h o t o c h e m i c a l a l k y l m i g r a t i o n h a s been o b s e r v e d i n d i a l k y l b o r y l a c e t o a c e t o n a t e complexes. 2 1 8 The a l k y l a t i o n o f dicyanoarenes with a l k y l t r i p h e n y l b o r a t e s a l t s can 219 be i n d u c e d p h o t o c h e m i c a l l y .

'''

Reference s 1 2 3 4 5 6

7 8 9 10 11

12 13 14 15 16 17

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,

84,

2,

-

x,

102,

IIII6: Photoreactions of Compounds containing Heteroatoms other than Oxygen 97 98 99 100 i0l 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 j.27 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142

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,

104,

17,

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143 144

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145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171

172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187

Y-L-Chow and Z.Z.Wu,

A. A-Freer, D.K.MacAlpine,

103,

2,

102,

108,

19,

118,

108,

-

-

67,

24,

11116: Photoreactions of Compounds containing Heteroatoms other than Oxygen 188 189 190 191 192 193 194 195 196 197 198 199 200

201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219

419

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-

-

s,

7 Photoelimination BY S. T. REID This Chapter i s p r i n c i p a l l y concerned with t h e photochemically i n d u c e d f r a g m e n t a t i o n o f o r g a n i c compounds, accompanied by t h e formation of s m a l l molecules such a s n i t r o g e n , carbon d i o x i d e and s u l p h u r d i o x i d e . P h o t o d e c o m p o s i t i o n s r e s u l t i n g i n t h e f o r m a t i o n of two o r more s i z a b l e f r a g m e n t s a r e r e v i e w e d i n t h e f i n a l s e c t i o n . F r a g m e n t a t i o n s a r i s i n g by N o r r i s h Type I a n d I 1 r e a c t i o n s o f c a r b o n y l - c o n t a i n i n g compounds a r e c o n s i d e r e d i n P a r t 111, C h a p t e r 1 , 1

E l i m i n a t i o n o f N i t r o g e n f r o m Azo-compounds

The p h o t o e l i m i n a t i o n o f n i t r o g e n f r o m a c y c l i c a z o a l k a n e s p r o v i d e s an e a s y a n d c o n v e n i e n t r o u t e t o a l k y l r a d i c a l s . Few r e s u l t s o f a n y s i g n i f i c a n c e have, however, been r e p o r t e d i n t h i s a r e a i n t h e p e r i o d c o v e r e d by t h i s r e p o r t . The p h o t o d e c o m p o s i t i o n of a r y l a z o p h o s p h o n a t e s a n d arylazoalkylphosphonates h a s b e e n s t u d i e d , a n d c y c l o h e x y l o x y r a d i c a l s h a v e b e e n g e n e r a t e d by p h o t o l y s i s o f d i c y c l o h e x y l h y p o n i t r i t e C6H1 , 0 N 2 0 C 6 H 1 Much a t t e n t i o n h a s b e e n d e v o t e d t o t h e s t u d y o f t h e p h o t o e l i m i n a t i o n o f n i t r o g e n f r o m c y c l i c a z o a l k a n e s . The p h o t o d e c o m p o s i t i o n of d i a z i r i n e s i s known t o p r o c e e d 9c a r b e n e intermediates r a t h e r than b i r a d i c a l i n t e r m e d i a t e s ? but d e t a i l s of t h e mechanism o f f o r m a t i o n of t h e s e s p e c i e s a r e n o t known w i t h c e r t a i n t y . A t h e o r e t i c a l s t u d y of t h e decomposition h a s been undertaken. P h e n y l c h l o r o c a r b e n e ( 1 1 , g e n e r a t e d by i r r a d i a t i o n o f p h e n y l c h l o r o d i a z i r i n e ( Z ) , h a s been c h a r a c t e r i z e d s p e c t r o s c o p i c a l l y warming t h e m a t r i x t o 3 3 K i n t h e i n an a r g o n m a t r i x a t 1 0 K ; 4 p r e s e n c e o f oxygen gave t h e c a r b o n y l o x i d e ( 3 ) . D i r e c t s p e c t r o s c o p i c i d e n t i f i c a t i o n o f b i s (trifluoromethyl)carbene5 a n d m e t h o x y c h l o r o c a r b e n e 6 o b t a i n e d i n t h e same way f r o m b i s ( t r i f 1 u o r o m e t h y 1 ) d i a z i r i n e and m e t h o x y c h l o r o d i a z i r i n e r e s p e c t i v e l y , h a s a l s o been r e p o r t e d , and evidence f o r t h e e x i s t e n c e and photochemically i n d u c e d i n t e r c o n v e r s i o n o f cis- a n d t r a n s - i s o m e r s o f phenoxyc h l o r o c a r b e n e , g e n e r a t e d by p h o t o e l i m i n a t i o n o f n i t r o g e n from The r e a c t i v i t y o f phenoxychlorodiazirine, h a s been published.

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Photochemistry

422

benzylchlorocarbene

( 4 ) , o b t a i n e d i n a s i m i l a r manner f r o m b e n z y l -

c h l o r o d i a z i r i n e ( S ) , h a s been examined; an a c t i v a t i o n b a r r i e r of 6 . 4 k c a l mol-’ h a s b e e n a s s i g n e d f o r 1 , 2 - H m i g r a t i o n , 8 a n d

E-

and Z - c h l o r o s t y r e n e s d e c o m p o s i t i o n i n t h e p r e s e n c e of H C 1 gave ( 6 ) by 1 , 2 - H m i g r a t i o n a n d 1-phenyl-2,2-dichloroethane ( 7 ) by The s t e r e o c h e m i s t r y of d i r e c t r e a c t i o n of t h e c a r b e n e w i t h H C l . ’ such 1 , 2 - H s h i f t s i n s i n g l e t c h l o r o - and phenyl-carbenes h a s been examined. Benzylchlorocarbene h a s a l s o been r e p o r t e d t o undergo a d d i t i o n t o t h e e l e c t r o n - d e f i c i e n t a l k e n e d i e t h y l f u m a r a t e , l 1 and t h e energy b a r r i e r f o r 1,Z-hydrogen m i g r a t i o n i n t h e r e l a t e d b e n z y l b r o m o c a r b e n e h a s b e e n shown t o be 4 . 7 k c a l mol-’ l 2 P h o t o e l i m i n a t i o n o f n i t r o g e n from 1- p y r a z o l i n e s can be

.

used t o g e n e r a t e 1 , 3 - b i r a d i c a l s and p r o d u c t s d e r i v e d therefrom. T r i p l e t 1 , 3 - c y c l o p e n t a d i y l , o b t a i n e d i n t h i s way by benzophenones e n s i t i z e d p h o t o d e c o m p o s i t i o n o f 2,3-diazabicyclo[2.2.llhept-2-ene, h a s been t r a p p e d i n e s s e n t i a l l y q u a n t i t a t i v e y i e l d w i t h molecular o x y g e n . 1 3 The l i f e t i m e s o f t r i p l e t b i r a d i c a l s o b t a i n e d f r o m t h i s a n d o t h e r a z o c y c l o a l k a n e s h a v e b e e n compared. l 4 I n t r a m o l e c u l a r 1 , 3 - d i y l t r a p p i n g on i r r a d i a t i o n o f a z o a l k e n e ( 8 ) t o g i v e t h e t r i c y c l o a l k e n e ( 9 ) i s t h e key s t e p i n a r e c e n t s y n t h e s i s o f (?Ic o r i ~ l i n , ’a n ~d t h e b i r a d i c a l i n t e r m e d i a t e ( 1 0 ) h a s b e e n p r o p o s e d t o a c c o u n t f o r t h e c o n v e r s i o n o f t h e a z o a l k e n e (11) i n t o t h e The p o s s i b l e i s o m e r i c b i c y c l o [ Z . l . O ] p e n t e n e s ( 1 2 ) a n d ( 1 3 ) .I6 intermediacy of diazenyl r a d i c a l s i n such photoelimination r e a c t i o n s h a s b e e n d i s c u s s e d w i t h r e f e r e n c e t o 2,3-diazabicyclo[2.2.1]h e p t - 2 - e n e a n d spiro[cyclopropane-l,7’-[2,3ldiazabicyclo[2.2.1]h e p t - 2 - e n e ] l 7 The d i f f e r e n c e i n t h e p h o t o c h e m i c a l b e h a v i o u r o f

.

4 , 5 - d i a z a t r i c y c l o [ 4 . 3 . 0 .03y7]non-4-en-8-one and t h e corresponding c y c l i c e t h y l e n e a c e t a l h a s b e e n e x p l a i n e d i n t e r m s o f i n i t i a l onebond c l e a v a g e s l e a d i n g t o d i a z e n y l r a d i c a l s ? The r e l a t e d a z o a l k a n e , 4 , s - d i a z a t r i c y c l o [ 4 . 3 . 0 . O 3 7 ] n o n a - 4 , 8 - d i e n e ( 1 4) , u n d e r g a e s competing e l i m i n a t i o n t o t h e t r i c y c l o h e p t e n e (1 5 ) and r e a r r a n g e the aziridine ment t o t h e a z i r i d i n e ( 1 6 ) on d i r e c t i r r a d i a t i o n ; ” i s o b t a i n e d e x c l u s i v e l y on benzophenone-sensitized i r r a d i a t i o n . 1 , 5 - B i r a d i c a l s b e l i e v e d t o b e i n v o l v e d i n t h e m e t a - p h o t o a d d i t i o n of a r e n e s t o a l k e n e s h a v e b e e n i n d e p e n d e n t l y p r e p a r e d by p h o t o Direct e l i m i n a t i o n of n i t r o g e n from t h e a p p r o p r i a t e azoalkanes.

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o b s e r v a t i o n o f t h e p r e v i o u s l y unknown t h e r m a l l y l a b i l e 7 - n o r b o r n a d i e n o n e ( 1 7 ) h a s b e e n a c h i e v e d on i r r a d i a t i o n o f t h e 1 - p y r a z o l i n e 21 (18) o r t h e 1 , 2 - a z e t i n e ( 1 9 ) i n 3 - m e t h y l p e n t a n e a t 1 0 K . S i m i l a r l y , Dewar b e n z e n e h a s b e e n p r e p a r e d by p h o t o e l i m i n a t i o n o f


423

N=N'

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(21)

424

Photochemistry

.

] o c t - 7 -ene , and n i t r o g e n from 7 ,8 - d i a z a t e t r a c y c l o [ 3 . 3 . 0 0 4 0 d i r e c t P y r e x - f i l t e r e d i r r a d i a t i o n of t h e 1 - p y r a z o l i n e ( 2 0 ) i n 23 methanol gave t h e v i n y l c y c l o p r o p a n e ( 2 1 ) i n q u a n t i t a t i v e y i e l d . S u c c e s s i v e p h o t o e l i m i n a t i o n s of n i t r o g e n have been o b s e r v e d i n t h e b i s a z o a l k a n e ( 2 2 ) l e a d i n g i n i t i a l l y t o t h e a z o a l k a n e (23) and t h r e e o t h e r s t e r e o i s o m e r i c a z o a l k a n e s w i t h no e v i d e n c e f o r t h e i n t e r m e d i a c y o f a t e t r a r a d i c a l . 2 4 F u r t h e r i r r a d i a t i o n gave t h r e e s t e r e o i s o m e r i c bi-5,5'-bicyclo[2.1.Olpentanes. 2,3-Diazabicyclo[2.2.2]oct-2-enes undergo p h o t o c h e m i c a l l y i n d u c e d e l i m i n a t i o n o f n i t r o g e n l e s s e f f i c i e n t l y and h i g h e r t e m p e r a t u r e s a r e o f t e n r e q u i r e d t o e f f e c t r e a c t i o n . Slow e l i m i n a t i o n o f n i t r o g e n l e a d i n g t o t h e b i c y c l o [ 2 . 2 . 0 ] h e x a n e ( 2 4 ) was t h e o n l y r e a c t i o n o b s e r v e d on i r r a d i a t i o n of a z o a l k a n e ( 2 5 ) i n methanol o r a c e t o n e s o l u t i o n . 25 P h o t o r e a c t i v i t y c a n be enhanced by t h e i n t r o d u c t i o n of s u i t a b l y p o s i t i o n e d c y c l o p r o p y l g r o u p s . I n t h e 2,3-diazabicyclo[2.2.2]oct-2-ene ( 2 6 1 , f o r example, c y c l o p r o p y l c a r b i n y l r e a r r a n g e m e n t l e a d i n g t o c y c l o a l k e n e s ( 2 7 ) , ( 2 8 ) a n d (29) s u c c e s s f u l l y competes w i t h r i n g c l o s u r e a n d s c i s s i o n o f t h e i n t e r m e d i a t e l Y 4 - b i r a d i c a l ( 3 0 ) which g i v e r e s p e c t i v e l y t h e 26 bicyclo[2.2.0]hexane (31) and t h e hexadiene (32). E l i m i n a t i o n of n i t r o g e n i s t h e major r e a c t i o n pathway o b s e r v e d on i r r a d i a t i o n ( A = 185 nm) o f g- o r ~ - 1 , 2 - d i a z a c y c l o i s p r e f e r r e d on i r r a d i a o c t - l - e n e , whereas 2,:-photoisomerization t i o n a t l o n g e r w a v e l e n g t h s (A = 350 nm) . 2 7 The t r i p l e t b i r a d i c a l , 2-methylenecyclohept-3-en-ly5-diyl, i s formed and h a s been i d e n t i f i e d by e . s . r . s p e c t r o s c o p y on i r r a d i a t i o n o f 6,7-diaza-Z-me28 thylenebicyclo[3.2.2]nona-3,6-diene i n a g l a s s y m a t r i x a t 77K. The a n a l o g o u s c o n v e r s i o n o f 3H-pyrazoles i n t o c y c l o p r o p e n e d e r i v a t i v e s i s known t o p r o c e e d via c y c l i z a t i o n o f a t r a n s i e n t v i n y l c a r b e n e . The c y c l o p r o p e n e ( 3 3 ) , f o r example, h a s been o b t a i n e d i n t h i s way i n e x c e l l e n t y i e l d by i r r a d i a t i o n o f t h e 3H-pyrazole (34) . 2 9 The f u s e d 3 H - p y r a z o l e s ( 3 5 1 , however , behave d i f f e r e n t l y a n d t h e b i r a d i c a l i n t e r m e d i a t e s (36) c a n be t r a p p e d w i t h f u r a n t o g i v e t h e a d d u c t s ( 3 7 ) . 30 A z i r i d i n e s c a n s i m i l a r l y be o b t a i n e d by p h o t o e l i m i n a t i o n of n i t r o g e n from l Y 2 , 3 - t r i a z o l i n e s . T h i s a p p r o a c h h a s been u s e d i n t h e s y n t h e s i s o f h e t e r o [ 4 . 2 . l ] p r ~ p e l l a n e s . ~1~, 2 , 3 - T r i a z o l e s , however, undergo p h o t o d e c o m p o s i t i o n i m i d o y l c a r b e n e s . The t r i a z o l e s ( 3 8 ) , f o r example, a r e c o n v e r t e d i n t h i s way i n t o t h e e x p e c t e d b e n z i n d o l e s (39) . 3 2 S u r p r i s i n g l y , t h e i s o m e r i c t r i a z o l e s

425

IIIl7: Photoelimination

(2 4)

(25)

t

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hv - N 2

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Photochemistry

426

SiMe,

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SO,A r Me

- N2

Me

Me

(33)

(34)

Ye N-f-Me II

Me

Me hv

- N2

(3 5 )

(36)

Y=Z=CH Y=N, Z=CH Y=CH, Z = N

1

furan

iiIi7: Photoelimination

427

R' = C02Et, R 2 = H R1 = C 0 2 M e or CN, R2 = H or Me

(38)

1

hv -Nq

(42)

(39) Scheme 1

Photochemistry

428

( 4 0 ) gave t h e same b e n z i n d o l e s ( 3 9 ) t o g e t h e r w i t h s m a l l e r amounts Intermediate 1I-J-azirines ( 4 2 ) a s of t h e e x p e c t e d b e n z i n d o l e s ( 4 1 ) . shown i n Scheme 1 a r e p r o p o s e d t o a c c o u n t f o r t h e s e o b s e r v a t i o n s . 4aH-Carbazoles ( 4 3 ) a r e b e l i e v e d t o be i n t e r m e d i a t e s i n t h e photochemically induced conversion of ? - s u b s t i t u t e d l-arylbenzot r i a z o l e s ( 4 4 ) i n t o c y c l o p e n t a q u i n o l i n e s ( 4 5 ) ;33 t h e r e a c t i o n

s e q u e n c e which i n v o l v e s p h o t o e l i m i n a t i o n o f n i t r o g e n f o l l o w e d by p h o t o c h e m i c a l l y i n d u c e d a z a - d i - r - m e t h a n e r e a r r a n g e m e n t i s shown i n Scheme 2 . Benzo d e r i v a t i v e s o f 4 a - m e t h y l - 4 a g - c a r b a z o l e have 34 been i s o l a t e d from a n a l o g o u s r e a c t i o n s . Examples o f p h o t o e l i m i n a t i o n of n i t r o g e n from t e t r a z o l e s have a l s o been r e p o r t e d . The diazacyclopentadienonimines (46) were o b t a i n e d on i r r a d i a t i o n o f t h e i m i d a z o [ l , 5 - ~ J ] t e t r a z o l e s ( 4 7 ) . 3 5 The i m i n o t e t r a z o l e s (48) a r e s i m i l a r l y c o n v e r t e d via t h e 36 t r i s ( i m i n o ) m e t h a n e b i r a d i c a l i n t o t h e 2-aminobenzimidazole ( 4 9 1 , and d i a r y l n i t r i l i m i n e s have been i d e n t i f i e d a s p r o d u c t s o f p h o t o 37,38 e l i m i n a t i o n of n i t r o g e n from a r y l - s u b s t i t u t e d 2 I - J - t e t r a z o l e s . 2

E l i m i n a t i o n o f N i t r o g e n from Diazo-compounds

C a r b e n e s a r e r e a d i l y o b t a i n e d by t h e p h o t o d e c o m p o s i t i o n o f d i a z o compounds. The r e a c t i o n s of c a r b e n e s g e n e r a t e d i n t h i s way i n r i g i d m a t r i c e s a t low t e m p e r a t u r e s have been r e v i e w e d . 39 A d d i t i o n of s i n g l e t methylene t o a c e t o n i t r i l e a f f o r d s t h e n i t r i l e y l i d e + + MeC=N-CH2, 4 0 and d i d e u t e r i o f o r m a l d e h y d e g - m e t h y l i d e , C D 2 =0-CHZ , h a s s i m i l a r l y been shown t o be a n i n t e r m e d i a t e i n t h e r e a c t i o n o f 41 photochemically generated dideuteriomethylene with formaldehyde. C o n f l i c t i n g r e s u l t s o b t a i n e d on p h o t o d e c o m p o s i t i o n of d i a z o c y c l o p e n t a d i e n e i n t h e p r e s e n c e o f oxygen have been r e c o n c i l e d by t h e i d e n t i f i c a t i o n of two p r o d u c t s , c y c l o p e n t a d i e n o n e 2 - o x i d e and t h e i s o m e r i c d i o x i r a n e . 4 2 T r i p l e t ground s t a t e c y c l o h e p t a t r i e n y l i d e n e ( S O ) h a s been p r e p a r e d by i r r a d i a t i o n o f a r g o n m a t r i x - i s o l a t e d diazocycloheptatriene(51) and c h a r a c t e r i z e d s p e c t r o s c o p i c a l l y ; 43 f u r t h e r i r r a d i a t i o n i s thought t o a f f o r d e i t h e r bicyclo[4.1.0]but there h e p t a - 2 , 4 , 6 - t r i e n e o r bicyclo[3.2.0]hepta-l,3,6-triene, i s no e v i d e n c e f o r t h e r m a l o r p h o t o c h e m i c a l f o r m a t i o n o f c y c l o heptatetraene. P a r t i c u l a r a t t e n t i o n h a s been d e v o t e d t o t h e c h a r a c t e r i z a t i o n and t o t h e r e a c t i o n s of a r y l c a r b e n e s . Energy d i f f e r e n c e s between s i n g l e t and t r i p l e t ground s t a t e c a r b e n e s a r e u s u a l l y

429

IIIl7: Photoelimination R1 = R 2 = H or Me R1 = H, R 2 = M e

Me

Me (45)

Scheme 2

R

R

A N-N

N’ Me0,C

hv

MN,i I

-N2

M e 0,C -NPh

Ph ( 4 7 ) R = Me or Ph

(46)

430

Photochemistry

s m a l l a n d a r e d e p e n d e n t on c h e m i c a l s t r u c t u r e . A t r i p l e t g r o u n d s t a t e h a s been d e t e c t e d i n t h e carbene d e r i v e d photochemically from 2,3-benzo-1 l - d i a z ~ f l u o r e n e ! ~w h e r e a s s i n g l e t g r o u n d s t a t e s a r e e n e r g e t i c a l l y p r e f e r r e d i n 9-xanthylidene4’ and i n 3,6-dimethoxyfluorenylidene . 4 6 R e s u l t s o b t a i n e d from a s t u d y of t h e photodecomposition of phenyldiazomethane i n cyclohexane and i n c y c l o h e x e n e a r e c o n s i s t e n t w i t h t h e i n v o l v e m e n t of s i n g l e t r a t h e r t h a n t r i p l e t p h e n y l c a r b e n e .47 The e n e r g y s e p a r a t i o n b e t w e e n s i n g l e t and t r i p l e t d i a r y 1 c a r b e n e s h a s been c o r r e l a t e d w i t h s t r u c t u r e . 4 8 The p h o t o l y s e s o f d i a r y l d i a z o m e t h a n e s h a v e a l s o b e e n 49 examined u s i n g p o l a r i z e d l i g h t . U n l i k e p h e n y l d i a z o m e t h a n e which i s c o n v e r t e d on i r r a d i a t i o n i n t o cyclohepta-1,2,4,6-tetraene, t h e c a r b e n e s ( 5 2 ) g e n e r a t e d by p h o t o d e c o m p o s i t i o n of t h e n a p h t h y l d i a z o m e t h a n e s ( 5 3 ) u n d e r g o r e a r r a n g e m e n t t o t h e benzobicyclo[4.1.O]hepta-2,4,6-trienes ( 5 4 ) . 50 Hydrogen a b s t r a c t i o n by t r i p l e t d i p h e n y l c a r b e n e i s o b s e r v e d on photodecomposition of diphenyldiazomethane i n cyclohexane, whereas s i n g l e t - d e r i v e d s o l v e n t i n s e r t i o n r e a c t i o n s compete w i t h h y d r o g e n a b s t r a c t i o n i n t h e analogous r e a c t i o n o f photochemically generated 51 fluorenylidene. A s t u d y o f t h e e f f e c t o f t e m p e r a t u r e on t h e photodecompo s i t i o n of diphenyldiazomethane i n methanol s u p p o r t s t h e p r e v i o u s view t h a t diphenylcarbene i n s e r t i o n t o g i v e t h e corresponding e t h e r i s s i n g l e t - d e r i v e d . 5 2 An a d d i t i o n a l s t e p i n v o l v i n g t h e r e v e r s i b l e f o r m a t i o n o f a n y l i d e h a s b e e n p r o p o s e d . The 0 - H i n s e r t i o n s e l e c t i v i t y of o t h e r photochemically generated carbenes i s influence d by t h e p r e s e n c e of 1 , 4 - d i o x a n e which h a s t h e a b i l i t y t o s t a b i l i z e s i n g l e t c a r b e n e s by c o m p l e x i n g w i t h t h e l o n e p a i r of e l e c t r o n s on o x y g e n , 53 a n d t h e r e a c t i o n s o f c a r b e n e s d e r i v e d f r o m 4 - s u b s t i t u t e d and 4 , 4 ’ - d i s u b s t i t u t e d diphenyldiazomethanes with m e t h a n o l i s e n h a n c e d by p - m e t h y l s u b s t i t u e n t s a n d r e t a r d e d by p - e l e c t r o n - w i t h d r a w i n g s u b s t i t u e n t s . 54 The f o r m a t i o n o f a n e n a n t i o m e r i c a l l y p u r e p r o d u c t on p h o t o d e c o m p o s i t i o n o f d i p h e n y l diazomethane i n s o l i d S-(+)-butan-2-01 i s thought t o a r i s e a t r i p l e t - d e r i v e d r a d i c a l p a i r i n which t h e r e i s no r o t a t i o n a l movement.55 A c o n c e r t e d s i n g l e t pathway d o e s n o t a p p e a r t o b e i n v o l v e d . Analogous i n t r a m o l e c u l a r h y d r o g e n a b s t r a c t i o n i s undoubtedly r e s p o n s i b l e f o r t h e formation of t r i p l e t b i r a d i c a l s (55) on i r r a d i a t i o n o f t h e n a p h t h y l d i a z o m e t h a n e s ( 5 6 ) i n r i g i d g l a s s e s a t 77 K.56

43 1


(48) R 1 = R 2 = Me, R 3 = Ph R2 = Ph, R1 = R 3 = M e

R

I

CRN,

R

hv

(53) R = H.or D

(52)

R

(56) R = H, Cl, Br, I , SPh, or SOzPh

(54)

R

(55)

432

Photochemistry

Reactions of photochemically generated a r y l carbenes with o t h e r s p e c i e s have a l s o been s t u d i e d . The mechanism o f a d d i t i o n o f c a r b e n e s t o a l k e n e s i s of c u r r e n t i n t e r e s t . A n o n - c o n c e r t e d pathway w i t h a r e v e r s i b l e f i r s t s t e p h a s been shown t o be i n v o l v e d i n t h e a d d i t i o n s of t r i p l e t f l u o r e n y l i d e n e and diphenylmethylene t o fumarate e s t e r s . 57 Nitrogen-laser e x c i t a t i o n of diazofluorene ( 5 7 ) i n a c e t o n e a t room t e m p e r a t u r e a f f o r d s t h e c a r b o n y l y l i d e ( 5 8 ) 58 which undergoes f u r t h e r p h o t o r e a r r a n g e m e n t t o t h e o x i r a n e ( S S ) , and l o n g - l i v e d t h i o c a r b o n y l y l i d e s have been i d e n t i f i e d i n t h e r e a c t i o n s of f l u o r e n y l i d e n e and d i p h e n y l c a r b e n e w i t h d i - t - b u t y l t h i o k e t o n e and adamantanethione. 59 The benzylamines ( 6 0 ) and t h e amines ( 6 1 ) a r e t h e major p r o d u c t s o f i r r a d i a t i o n of a r y l d i a z o methanes (62) i n d i e t h y l a m i n e ; t h e y a r i s e r e s p e c t i v e l y by N-H and C-H c a r b e n e i n s e r t i o n r e a c t i o n s .60 Hydrogen a b s t r a c t i o n p r o d u c t s were formed a t t h e expense o f i n s e r t i o n p r o d u c t s on i r r a d i a t i o n of p-nitrophenyldiazomethane under t h e same c o n d i t i o n s . P o s s i b l e e x p l a n a t i o n s f o r t h i s d i f f e r e n c e i n r e a c t i v i t y have been o f f e r e d . P h o t o c h e m i c a l l y g e n e r a t e d a r y l c a r b e n e s have been i n t e r c e p t e d w i t h carbon monoxide" and w i t h oxygen. Benzophenone 2-oxide h a s been d e t e c t e d s p e c t r o s c o p i c a l l y on i r r a d i a t i o n ( 5 1 5 nm) o f d i p h e n y l diazomethane a t 8 K i n t h e p r e s e n c e of oxygen,62 b u t t h e r e i s no e v i d e n c e f o r c a r b o n y l o x i d e f o r m a t i o n on p h o t o e l i m i n a t i o n o f n i t r o g e n from phenyldiazomethane under i d e n t i c a l c o n d i t i o n s . 6 3 Benzoic a c i d and benzaldehyde have been i d e n t i f i e d a s p r o d u c t s . The photochemical g e n e r a t i o n o f a r y l c a r b e n e s f o r p o t e n t i a l u s e a s o r g a n i c f e r r o m a g n e t s h a s been r e p o r t e d . 6 4 9 6 5 The e l e c t r o p h i l i c c a r b e n e , 4 g - i m i d a z o l y l i d e n e (631, h a s 66 (64). been p r e p a r e d by photodecomposition of 4-diazo-4€j-imidazole R e a c t i o n w i t h cyclohexane a f f o r d s t h e C-H i n s e r t i o n p r o d u c t , 4(5)c y c l o h e x y l i m i d a z o l e ( 6 5 ) , whereas r e a c t i o n w i t h benzene y i e l d s 4 ( 5 ) - p h e n y l i m i d a z o l e ( 6 6 ) . Analogous a d d i t i o n of 4 5 - i m i d a z o l y l i d ene t o d e r i v a t i v e s of benzene i s i n f l u e n c e d by t h e p r e s e n c e and n a t u r e of t h e s u b s t i t u e n t s . - a - D i a z o a c e t a t e s and r e l a t e d e s t e r s a r e a u s e f u l s o u r c e of c a r b e n e s . I r r a d i a t i o n of t h e c h o l e s t e r o l diazopcetate (67) i n 67 c y c l o h e x a n e , f o r example , gave t h e C-H i n s e r t i o n p h d u c t ( 6 8 ) , and a d d i t i o n of t h e c a r b e n e s i m i l a r l y g e n e r a t e d from d i m e t h y l diazomalonate t o bis[trimethylsilyllacetylene a f f o r d e d t h e c o r r e s p o n d i n g 2 , 3 - d i s i l y l a t e d c y c l o p r o p e n e . 6 8 The r e a c t i o n s o f t h e same c a r b e n e w i t h c y c l i c d i s u l p h i d e s have been examined.

69


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Ar-CH2-CH,

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(66)

434

Photochemistry

a-Diazo k e t o n e s and r e l a t e d s p e c i e s r e a d i l y undergo l-Diazo-3-(l-methylcyclopenta-2,4-diphoto-Wolff r e a r r a n g e m e n t . eny1)propan-2-one (691, f o r e x a m p l e , i s c o n v e r t e d i n t h i s way on d i r e c t i r r a d i a t i o n i n t o t h e k e t e n e ( 7 0 ) ; 70 i n c o n t r a s t , i n t r a m o l e c u l a r c a r b e n e a d d i t i o n i s p r e f e r r e d on b e n z o p h e n o n e - s e n s i t i z e d O t h e r examples o f t h e i r r a d i a t i o n y i e l d i n g t h e adduct ( 7 1 ) . a p p l i c a t i o n of t h e p h o t o c h e m i c a l l y i n d u c e d Wolff r e a r r a n g e m e n t t o a c y c l i c d i a z o k e t o n e s have been r e p o r t e d . 7 1 - 7 4 Of p a r t i c u l a r i n t e r e s t i s t h e m i g r a t i o n o f a carbomethoxy group o b s e r v e d on i r r a d i a t i o n i n e t h a n o l of methyl 3-diazo-2-oxopropionate ( 7 2 ) t o g i v e e t h y l m e t h y l m a l o n a t e ( 7 3 ) a s shown i n Scheme 3 . 7 4 P h o t o i n d u c e d Wolff r e a r r a n g e m e n t i n c y c l i c a - d i a z o k e t o n e s i s f r e q u e n t l y accompanied by r i n g c o n t r a c t i o n . Thus, diazodimedone ( 7 4 ) i s c o n v e r t e d i n t o t h e c y c l o p e n t a n o n e s ( 7 5 ) on i r r a d i a t i o n i n t h e p r e s e n c e o f o p t i c a l l y a c t i v e a l c o h o l s . 7 5 An a n a l o g o u s r i n g c o n t r a c t i o n h a s been r e p o r t e d f o r 5 - d i a z o - 2 , 2 - d i m e t h y l - 4 , 6 - d i o x o - l , 3 - d i o x a n e , 76 and t h e p h o t o d e c o m p o s i t i o n o f u n s y m m e t r i c a l l y s u b s t i t u t e d 4-diazopyrazolidine-3,5-diones h a s been used i n t h e s y n t h e s i s of aza-B-lactams. 7 7 Examples of p h o t o e l i m i n a t i o n of n i t r o g e n from o t h e r r e l a t e d s y s t e m s have been r e p o r t e d . The A3-phosphinocarbene ( 7 6 ) , o b t a i n e d by p h o t o d e c o m p o s i t i o n o f t h e a - d i a z o p h o s p h i n e ( 7 7 ) , h a s been i n t e r c e p t e d w i t h d i m e t h y l a m i n e t o g i v e t h e t e r t i a r y amine (78) , 7 8 and i r r a d i a t i o n o f t h e t o s y l h y d r a z o n e ( 7 9 ) a f f o r d s t h e t r i e n e ( 8 0 ) and t h e c y c l o p r o p e n e ( 8 1 ) by way o f a c a r b e n e i n t e r m e d i a t e a s shown i n Scheme 4 . 79 I n t r a m o l e c u l a r c a r b e n e a d d i t i o n h a s been o b s e r v e d on i r r a d i a t i o n o f t h e q u i n o n e d i a z i d e (82) t o g i v e t h e spiro-cyclopropane-cyclohexadienone ( 8 3 ) ;80 oxygen t r a n s f e r from t h e sulphonamido g r o u p i s a c o m p e t i n g p r o c e s s . The p h o t o d e c o m p o s i t i o n o f 2-benzoquinone d i a z i d e i t s e l f h a s b e e n examined i n a p i p e r y l e n e o l i g o m e r m a t r i x a t 7 7 K , 8 1 a n d f u r t h e r s t u d i e s o f t h e p h o t o l y s i s o f a r e n e d i a z o n i u m s a l t s have been described. 8 2 83 3

E l i m i n a t i o n of N i t r o g e n from A z i d e s

The p h o t o r e a c t i o n s o f a z i d e s c a n i n most c a s e s b e r a t i o n a l i z e d i n t e r m s of t h e f o r m a t i o n of i n t e r m e d i a t e n i t r e n e s which t h e n undergo r e a r r a n g e m e n t , i n s e r t i o n , o r a d d i t i o n . A t h e o r e t i c a l s t u d y o f t h e p h o t o d e c o m p o s i t i o n o f m e t h y l a z i d e h a s been r e p o r t e d . 84


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P h o t o e l i m i n a t i o n of n i t r o g e n from f l u o r o a l k y l a z i d e s gave t h e c o r r e s p o n d i n g f l u o r o i m i n e s by r e a r r a n g e m e n t o f s h o r t - l i v e d i n t e r m e d i a t e n i t r e n e s . 8 5 Dimeric p r o d u c t s o b t a i n e d on i r r a d i a t i o n of 9-azido-10-methyltriptycene (84) a r i s e via t h e i n i t i a l l y formed b r i d g e h e a d imine ( 8 5 ) . 8 6 A v a r i e t y o f r e a c t i o n s have been r e p o r t e d f o r a n a l o g o u s l y formed p h o s p h i n o n i t r e n e s . 8 7 I r r a d i a t i o n o f t h e phosphine a z i d e (86) i n m e t h a n o l , f o r example, gave t h e p r o d u c t (87) by a d d i t i o n of s o l v e n t t o t h e t r a n s i e n t oxo-iminophosphorane ( 8 8 ) . P h o t o e l i m i n a t i o n of n i t r o g e n from t h e d i a z i d e d i m e t h y l d i a z i d o s i l a n e h a s been shown t o y i e l d d i m e t h y l s i l y l e n e , 8 8 and s u c c e s s i v e l o s s of n i t r o g e n h a s been o b s e r v e d on i r r a d i a t i o n o f 2 , 3 - d i a z i d o - 1 , 3 - b u t a 89 (90). d i e n e (89) t o g i v e t h e b i s - 2 H - a z i r i n - 3 - y l S t u d i e s of t h e p h o t o r e a c t i o n s of a r y l and h e t e r o a r y l a z i d e s have a l s o been d e s c r i b e d . N i t r o - s u b s t i t u t e d a r y l a z i d e s a r e of i n t e r e s t b e c a u s e o f t h e i r p o s s i b l e u s e i n p h o t o a f f i n i t y The r e a c t i v i t i e s of r o t a m e r i c a p - and s p - 3 , 5 dimethyl-2-(9-fluorenyl)phenylnitrenes, o b t a i n e d by p h o t o l y s i s o f t h e c o r r e s p o n d i n g a z i d e s , have been c o m p a r e d Y g 2and d i o x o a n t h r a [ 1 , 2 - d ] p y r a z o l i n e s have been p r e p a r e d by i r r a d i a t i o n of l - a z i d o - 2 [ ( d i a l k y l a m i n o ) m e t h y l ] -9 ,1 0 - a n t h r a q u i n o n e s . 9 3 H e t e r o a r y l a z i d e s f r e q u e n t l y undergo r i n g e x p a n s i o n on p h o t o e l i m i n a t i o n of n i t r o g e n ; f u s e d a z i r i n e i n t e r m e d i a t e s have been p r o p o s e d . I r r a d i a t i o n of t h e 4 - a z i d o i s o q u i n o l i n e s ( 9 1 ) , f o r example, gave i n t h e p r e s e n c e o f sodium methoxide t h e 1!-2,4b e n z o d i a z e p i n e s ( 9 2 ) . 9 4 The l i k e l y pathway i s o u t l i n e d i n Scheme 5 . Analogous r i n g e x p a n s i o n s have been r e p o r t e d f o r 5 - a z i d o - , 8 - a z i d o - , 6-azido-8-methoxy- and 8-azido-6-methoxy-quinolines i n a l c o h o l a l k o x h e - d i o x a n e s o l u t i o n c o n t a i n i n g 18-crown-6 . 9 5 I r r a d i a t i o n of t h e 2-substituted 3-azidopyridines ( 9 3 ) , again in t h e presence of sodium m e t h o x i d e , l e d t o t h e f o r m a t i o n o f t h e n o v e l 2 H - l Y 4 - d i a z e p i n e s (94) a s shown i n Scheme 6 , whereas 2 - u n s u b s t i t u t e d and 2 , 4 d i s u b s t i t u t e d 3 - a z i d o p y r i d i n e s a r e c o n v e r t e d i n t o t h e known 5H1 , 3 - d i a ~ e p i n e s . ~No~ r i n g e x p a n s i o n p r o d u c t s were d e t e c t e d on i r r a d i a t i o n of 3- and 4 - a z i d o p y r i d i n e l - o x i d e s i n n u c l e o p h i l i c s o l v e n t s . 9 7 P h o t o c h e m i c a l l y i n d u c e d d e c o m p o s i t i o n o f 3-azido-2v i n y l t h i o p h e n e s l e a d s t o t h e f o r m a t i o n of t h i e n o [ 3 , 2 - b l p y r r o l e s .98 9 9 The a z i d e ( 9 5 ) , f o r example, i s c o n v e r t e d on i r r a d i a t i o n i n a c e t o n i t r i l e i n t o t h e p y r r o l e ( 9 6 ) ; t h e p r o p o s e d mechanism, which involves i n i t i a l formation of a n i t r e n e , 1,5-electrocyclization t o t h e f u s e d 2 H - p y r r o l e , and s i g m a t r o p i c m i g r a t i o n o f t h e Z - s u b s t i t u e n t , i s shown i n Scheme 7 . 2 - A z i d o s t y r e n e s have s i m i l a r l y been

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P h o t o e l i m i n a t i o n o f Carbon D i o x i d e

Photochemically induced decarboxylations o f (phenyla1koxy)acetic a n d of a c i d s i n t h e p r e s e n c e o f m e r c u r y (11) o x i d e and iodine1'' t h r e o - a l e u r i t i c a c i d i n t h e p r e s e n c e o f l e a d t e t r a a c e t a t e and iodine"' have been r e p o r t e d . Carbon d i o x i d e i s o n e o f many p r o d u c t s o b t a i n e d by g a s - p h a s e p h o t o l y s i s o f d i m e t h y l o x a l a t e . 102 Carbon d i o x i d e i s a l s o e l i m i n a t e d on i r r a d i a t i o n o f t h e l a c t o n e (97) t o g i v e 1 - m e t h y l n a p h t h a l e n e (98) i n h i g h y i e l d . l o 3 S e l e c t i v e mixed c o u p l i n g h a s b e e n o b s e r v e d on p h o t o d e c o m p o s i t i o n o f unsym* l o 5 t h e p e r o x i d e (99), f o r e x a m p l e , metrical diacyl peroxides; i s c o n v e r t e d i n 61% y i e l d i n t o t h e a l k e n e ( l o o ) , and c y c l o p e n t a decanone a n d c y c l o t e t r a d e c a n e h a v e s i m i l a r l y b e e n p r e p a r e d by p h o t o e l i m i n a t i o n of carbon d i o x i d e from t h e a p p r o p r i a t e c y c l i c 106 tetraacyl diperoxide The s y n t h e s i s of 1 - a z a b i c y c l o b u t a n e s ( 1 0 1 ) h a s b e e n a c c o m p l i s h e d i n r e a s o n a b l e y i e l d by i r r a d i a t i o n o f t h e c y c l i c 107 carbarnates (102) i n a c e t o n i t r i l e i n t h e p r e s e n c e of p y r i d i n e . E l i m i n a t i o n o f c a r b o n d i o x i d e h a s a l s o b e e n o b s e r v e d on i r r a d i a t i o n ring o f t h e [1,2,4]oxadiazolo[2,3-clquinazolinazolin-2-one ( 1 0 3 ) ; l o 8 cleavage p r o d u c t s ( 1 0 4 ) and (105) were o b t a i n e d and t h e proposed pathway i s o u t l i n e d i n Scheme 8 . @-Lactams (106) h a v e b e e n o b t a i n e d i n t h e same way by p h o t o d e c o m p o s i t i o n o f t e t r a h y d r o - 1 , 2 oxazine-3,6-diones (107) , l o g and photochemically induced n i t r o g e n n i t r o g e n bond h o m o l y s i s f o l l o w e d by l o s s o f c a r b o n d i o x i d e h a s been used i n t h e s y n t h e s i s of 1 , 2 , 4 - o x a d i a z o l e s from N-nitroso-N-acetyla-amino a c i d s . l o P r o d u c t s c o n s i s t e n t w i t h a pathway i n v o l v i n g s e q u e n t i a l e l e c t r o n t r a n s f e r were o b t a i n e d on p h o t o l y s i s o f t h e p e p t i d e t r i g l y c i n e . 111 D e t a i l e d s t u d i e s of t h e photoinduced decarboxylative 112 rearrangement of thiohydroxamic e s t e r s have been undertaken. C r o s s o v e r e x p e r i m e n t s i n d i c a t e t h e p h o t o d e c o m p o s i t i o n t o be a r a d i c a l c h a i n p r o c e s s a s shown i n Scheme 9 . 1 1 3 P e r f l u o r o a c i d

.

e s t e r s of Ij-hydroxypyridine 2-thione a l s o undergo decarboxylative r e a r r a n g e m e n t on i r r a d i a t i o n t o g i v e 2-perfluoroalkylthiopyridines i n h i g h y i e l d . ' 1 4 The c a r b o n r a d i c a l s t h u s formed h a v e b e e n t r a p p e d with e l e c t r o n - r i c h a l k e n e s . Alkyl r a d i c a l s d e r i v e d i n a s i m i l a r f a s h i o n add r e a d i l y t o p v i n y l sulphone and v i n y l - h e n .y l phosphonium bromide" a n d t o p r o t o n a t e d h e t e r o a r o m a t i c compounds

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c o n t a i n i n g a b a s i c methine n i t r o g e n . l 6 ( L ) -Glutamate e s t e r s of h a v e b e e n shown t o u n d e r g o t h e same d e c a r b o x y l a t i v e r e a r r a n g e m e n t a s t h e i r t h i o - a n a l o g u e s . 117

N-hydroxy-2-selenopyridine

5

F r a g m e n t a t i o n of O r g a n o s u l p h u r Compounds

C a r b o n - s u l p h u r bond h o m o l y s i s i s r e s p o n s i b l e f o r many p h o t o c h e m i c a l l y i n d u c e d d e c o m p o s i t i o n s o f o r g a n o s u l p h u r compounds. P e n t a fluorophenylprop-2-enyl t h i o e t h e r (108) undergoes carbon-sulphur bond c l e a v a g e on i r r a d i a t i o n i n c y c l o h e x a n e t o g i v e t h e t h i o l (109) Photoelimination of and t h e cyclohexyl t h i o e t h e r (110). l 1 methanethiol i s t h e p r i n c i p a l r e a c t i o n observed i n t h e d i t h i o a c e t a l ( 1 1 1 1 and l e a d s t o t h e Z,E-stereoisomeric b e n z o t h i a z o l e s (1 1 2 ) . ’ l 9 A r y l p h e n a c y l s u l p h i d e s u n d e r g o c a r b o n - s u l p h u r bond h o m o l y s i s on i r r a d i a t i o n , t h e major p r o d u c t s b e i n g t h e corresponding methyl k e t o n e s a n d d i s u l p h i d e s . 1 2 0 A wide v a r i e t y o f s u b s t i t u t e d t h i o a l d e h y d e s , o b t a i n e d by p h o t o d e c o m p o s i t i o n o f t h e a p p r o p r i a t e phenacyl s u l p h i d e s , have been t r a p p e d a s t h e d i h y d r o t h i o p y r a n s by r e a c t i o n w i t h d i e n e s . 1 2 ’ An example o f t h i s c o n v e r s i o n , which

i s t h o u g h t t o i n v o l v e a Type I 1 f r a g m e n t a t i o n , i s shown i n Scheme 1 0 . a - S c i s s i o n h a s a l s o b e e n o b s e r v e d o n i r r a d i a t i o n of ( 2 , 4 , 6 t r i m e t h y l b e n z o y l ) diphenylphosphine s u l p h i d e , 2 2 and t h e c - a l k y l S - p h t h a l y l g l y c y l x a n t h a t e s ( 1 1 3 ) u n d e r g o d e c o m p o s i t i o n on i r r a d i a 123 t i o n i n benzene t o g i v e t h e a l k y l x a n t h a t e s ( 1 1 4 ) . E x t r u s i o n o f s u l p h u r f r o m s u l p h i d e s by i r r a d i a t i o n i n t h e presence of t r i m e t h y l o r t r i e t h y l p h o s p h i t e h a s a g a i n been used i n s y n t he s i s . The f i r s t [ 2 . 1 ] p h a n e , 6 , 7 - d i hy d r o b e n zo [&I n a p h t ho [ 2 ,1 , 8 g h i l o x e c i n e ( 1 I S ) , h a s b e e n o b t a i n e d i n t h i s way f r o m t h e s u l p h i d e 125 ( 1 1 6 ) . 2 4 D i t h i a [ 3.31 - a n d [ 2 . 2 1 - a z u l e n o ( 2 , 6 ) p y r i d i n o p h a n e s and isomeric b i s (methoxycarbonyl) [ 2 . 2 1 (2,S)pyridinophanes’ 26 have been s i m i l a r l y p r e p a r e d . I r r a d i a t i o n of t h e Z-thioxo-1,3-dithiole ( 1 1 7 ) i n t h e p r e s e n c e o f t r i e t h y l p h o s p h i t e , h o w e v e r , gave t h e t e t r a t h i o f u l v a l e n e (1 1 8 ) ; 2 7 p h o t o i n d u c e d e l e c t r o n t r a n s f e r f r Q m

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t h e phosphite appears t o a c c e l e r a t e t h e formation of zwitterion intermediate (119). I r r a d i a t i o n of t h e aB-unsaturated sulphine ( 1 2 0 ) i n c h l o r o f o r m gave a s i n g l e p r o d u c t , t h e k e t o n e ( 1 2 1 1 , i n 9 0 % y i e l d . ’ 2 8 An o x a t h i i r a n e i n t e r m e d i a t e i s p r o b a b l y i n v o l v e d in t h i s transformation. Bis(trifluoromethy1)sulphine i s s i m i l a r l y 129 c o n v e r t e d w i t h e x t r u s i o n of s u l p h u r i n t o h e x a f l u o r o a c e t o n e .


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6

Miscellaneous Decomposition and E l i m i n a t i o n Reactions

Fragmentation and e l i m i n a t i o n r e a c t i o n s t h a t cannot be included i n any of t h e above c a t e g o r i e s a r e b r i e f l y r e v i e w e d i n t h i s S e c t i o n . I t has not proved p o s s i b l e t o c l a s s i f y t h e s e p r o c e s s e s , but l i k e r e a c t i o n s a r e grouped t o g e t h e r . Carbon-oxygen bond h o m o l y s i s i s r e s p o n s i b l e f o r t h e f o r m a t i o n o f some of t h e p r o d u c t s o b t a i n e d on p h o t o d e c o m p o s i t i o n o f l i q u i d 1 , 3 - d i o x a n e , ' 30 a n d t h e n u c l e o p h i l i c a d d i t i o n of primary a l c o h o l s t o N-methylacridinium c h l o r i d e t o give N-methyl-9-alkoxyacridans i s r e v e r s e d on i r r a d i a t i o n a t 7 7 K . 131 P r o d u c t s of i r r a d i a t i o n o f o x i r a n e s a r e d e r i v e d a number o f d e c o m p o s i t i o n p a t h w a y s . Both t h e c a r b o n y l y l i d e ( 1 2 2 ) a n d t h e c a r b e n e (123) a r e i m p l i c a t e d i n t h e e x c i t e d s i n g l e t s t a t e r e a c t i o n s of t h e a 8 - u n s a t u r a t e d y6-epoxy n i t r i l e ( 1 2 4 ) . 32 I n t r a m o l e c u l a r a d d i t i o n of a photochemically generated vinyl carbene i s a l s o r e s p o n s i b l e f o r t h e c o n v e r s i o n o f t h e two e p o x y d i e n e s ( 1 2 5 ) i n t o t h e c y c l o p r o p e n e ( 1 2 6 ) . 33 B i r a d i c a l i n t e r m e d i a t e s have b e e n proposed t o account f o r t h e formation of t r i p l e t - d e r i v e d products of o t h e r 5 , 6 - e p o ~ y - l , 3 - d i e n e s , ~a~n~d f u r t h e r s t u d i e s o f t h e p h o t o c h e m i s t r y of c a r b o n y l - c o n t a i n i n g o x i r a n e s have b e e n r e p o r t e d . 135137 Oxygen-oxygen bond h o m o l y s i s i s t h e i n i t i a l s t e p i n t h e p h o t o r e a r r a n g e m e n t of 9,10-dimethyl-9,10-dihydro-9,lO-epidioxya n t h r a c e n e (127) t o t h e d i m e t h y l a c e t a l ( 1 2 8 ) . 1 3 * Cyclohexanone 139 p e r o x i d e s have s i m i l a r l y been c o n v e r t e d t o c a r b o x y l i c a c i d s , and h y d r o x y l r a d i c a l s a r e g e n e r a t e d on i r r a d i a t i o n o f u n s a t u r a t e d f a t t y a c i d h y d r o p e r o x i d e s . 1 4 0 The u n s t a b l e 2 - a z a c a r b a p e n e m s ( 1 29) 141 a n d (130) were p r e p a r e d by p h o t o l y s i s o f t h e o z o n i d e ( 1 3 1 ) . P h o t o d e a l k y l a t i o n o f amines i s a well-documented r e a c t i o n p-Dimethylamino-p'-nitrodiphenylethyne h a s b e e n shown t o u n d e r g o t h i s decomposition e x c l u s i v e l y on i r r a d i a t i o n i n t o l u e n e , e t h e r o r acetone. 142 Numerous e x a m p l e s o f p h o t o c y c l i z a t i o n accompanied by e l i m i n a t i o n of H C 1 , H B r o r H I have a g a i n been d e s c r i b e d a l t h o u g h i n most c a s e s d e t a i l s o f t h e r e a c t i o n mechanism a r e n o t c l e a r . Noteworthy e x a m p l e s i n c l u d e t h e c o n v e r s i o n o f t h e I j - ( h y d r o x y p h e n y l ethyl)-3-(bromophenyl)propionamide (132) i n t o t h e 11-membered l a c t a m ( 1 3 3 ) ' 4 3 and t h e s y n t h e s e s o f 4 , 5 , 7 a Y 8 - t e t r a h y d r o - 1 ,2d i m e t h o x y p h e n a n t h r o [ 1 0 , l -&I a z e p i n - 6 (7H) -one1 4 4 a n d (+I - c a t h a r a n t b A key s t e p i n t h e s y n t h e s i s of c r a s s i f o l a z o n i n e i s t h e i n e 14' u n u s u a l p h o t o c y c l i z a t i o n u n d e r a l k a l i n e c o n d i t i o n s o f t h e bromo

.

447

lIIl7: Photoelimination

OH

Meo&N"

-

0

KOH,hv+ MeOH

QJ0

Me0

OMe

(132)

OMe

(133)

OH

OH

MeotLA

Meo*

HowNH &:: \

hv

______j

KOH, MeOH

Me0

OMe (134)

(136)

(137) R = Me or OMe

(135)

(139)

(138)

448

Photochemistry

compound (134) i n t o t h e i n d o l i n e ( 1 3 5 1 , a p r o c e s s which i s t h o u g h t t o o c c u r by n u c l e o p h i l i c a t t a c k o f amide a n i o n on t h e a r y l 146 radical. I n t e r m o l e c u l a r p h o t o e l i m i n a t i o n o f HX h a s b e e n employed i n t h e s y n t h e s i s of 2 - a r y l p y r i d i n e s 4 - h e t e r o a r y l p y r i d i n e s , 148 a n d c y c l o h e x y l a r e n e s . 51 I r r a d i a t i o n o f 5-bromoa r y l f u r a n s 14’ ’’ 1 , 3 - d i m e t h y l u r a c i l (136) i n t h e p r e s e n c e o f s u b s t i t u t e d b e n z e n e s (137) s u r p r i s i n g l y a f f o r d s t h e 6 - a r y l d e r i v a t i v e s (138) a s w e l l a s t h e e x p e c t e d 5 - a r y l i s o m e r s ( 1 39) ; ’ 5 2 d i f f e r e n t r e a c t i o n mechanisms may b e i n v o l v e d . The s y n t h e s e s o f 5 - a l k y l p y r i m i d i n e a n d 5 - a l k y 1- a n d 5 - h e t e r o a l ky 1- p y r i m i d i n e nuc l e o s i d e s n u c l e o t i d e ~h a~v~e ~b e e n a c h i e v e d i n a s i m i l a r manner u s i n g 2 - i o d o e t h a n o l . The p h o t o c h e m i s t r y o f a r y l h a l i d e s h a s b e e n r e v i e w e d . 155 Much i n t e r e s t h a s b e e n shown i n t h e s t u d y a n d u s e o f p h o t o i n i t i a t e d SRNl r e a c t i o n s . 1 5 6 - 1 6 7 I n p a r t i c u l a r , t h e p r o c e s s h a s b e e n employed i n t h e c o n s t r u c t i o n o f b e n z o [ ~ l p h e n a n t h r i d i n e s a n d benzo [ c l p h e n a n t h r i d o n e s , 1 6 8 o f 3 - b e n z a z e p i n e s a n d 3-benzoxep170,171 i n e s , I 6 ’ and of f u n c t i o n a l i z e d 6 - a l k y l a t e d p u r i n e s . Many o t h e r p h o t o c h e m i c a l l y i n d u c e d d e c o m p o s i t i o n s a r i s e by c a r b o n - h a l o g e n bond c l e a v a g e . The m a j o r i t y o f t h e s e r e a c t i o n s a r e r a d i c a l p r o c e s s e s w i t h l i t t l e photochemical s i g n i f i c a n c e and a r e t h e r e f o r e n o t reviewed i n d e t a i l i n t h i s Report. Interest is evident i n photochemically generated vinyl r a d i c a l c y c l i z a t i o n . I r r a d i a t i o n i n benzene of t h e v i n y l a z e t i d i n o n e

(1401, f o r

e x a m p l e , gave t h e l a - m e t h y l c a r b a p e n a m ( 1 4 1 ) t o g e t h e r w i t h t h e r e d u c t i o n p r o d u c t ( 1 4 2 ) . ’ 7 2 P r o d u c t s d e r i v e d by b o t h r a d i c a l and i o n i c pathways have been o b t a i n e d from 2-phenylethyl and 174 4 - p h e n y l - 1 - b u t y l h a l i d e s , ’ 7 3 f r o m w-bromo-w-phenylcamphene, a n d f r o m v i n y l i d e n e d i h a l i d e s d e r i v e d f r o m camphene. 17’ Benzyl c a r b o c a t i o n s , h o w e v e r , a r e formed e x c l u s i v e l y on i r r a d i a t i o n of benzyl c h l o r i d e o r benzyl a c e t a t e i n aqueous methanol,176 and t h e t r i a r y l c h l o r o a l l e n e s (143) a r e photochemically c o n v e r t e d i n t o t h e 1,3,3-triaryl-3-methoxypropynes ( 1 4 4 ) i n m e t h a n o l , s u g g e s t i n g the i n t e r v e n t i o n of t r i a r y l a l l e n y l c a t i o n s . 77 Photochemically i n d u c e d Wagner-Meerwe i n r e a r r a n g e m e n t s h a v e b e e n r e p o r t e d i n c h l o r o - s u b s t i t u t e d d i b e n z o b i c y c l o [ 2 . 2 . 2 1 o c t a - 2 , S - d i e n e s , ’ 78 i n 179 c i s - a n d trans-7,8-dichlorodibenzobicyclo[2.2.2]octadienes, and i n syn- and anti-8-chloro-2,3:6,7-dibenzobicyclo[3.2.llocta2 , 6 - d i e n - 4 - y l s y s t e m s . 8o 2 , 4 - D i n i t r o - 6 - (pheny1iodonio)phenolate ( 1 4 5 ) r e a d i l y u n d e r g o e s p h o t o r e a c t i o n w i t h n u c l e o p h i l e s ; 18’ w i t h


449

H

$ 2

0

hv benzene

__i)

0

(140)

R2

R2

R’

)c=c=c, R2

hV MeOH

/

CI

1

R ~ - C-CEC-R’

1

OMe (143) R1 = R 2 = P h R1 = Ph, R 2 = p-MeC6H4 R1 = p-MeOC&,R2 = Ph

(145)

(146)

0

I

py ridine

0’ (151) S c h e m e 11

CHO (150)

Photochemistry

450

p h e n y l t h i o c y a n a t e , f o r e x a m p l e , t h e o x a t h i o l e (146) i s o b t a i n e d . P h o t o c h e m i c a l l y i n d u c e d n i t r o g e n - h a l o g e n bond c l e a v a g e i s r e s p o n s i b l e f o r t h e c o n v e r s i o n o f N,N-dihalo-1,l-difluoroamines i n t o t h e c o r r e s p o n d i n g d i a z e n e s , 18' a n d f o r t h e f o r m a t i o n o f t h e 1 , l - a d d u c t ( 1 4 7 ) a n d t h e 1 , Z - a d d u c t ( 1 4 8 ) o b t a i n e d on photodecompo s i t i o n of 1,4-dibromo-Z,5-piperazinedione ( 1 4 9 ) i n t h e p r e s e n c e of 1 8 3 The p h o t o l y s i s o f h y p o i o d i t e s c o n s t i t u t e s 3,4-dihydro-Z!-pyran. a v a l u a b l e a p p r o a c h t o a l k o x y r a d i c a l s . The f o r m a t i o n o f t h e

f o r m a t e (150) by i r r a d i a t i o n o f t h e l a c t o l ( 1 5 1 ) i n t h e p r e s e n c e o f HgO-IZ a s shown i n Scheme 1 1 i s a k e y s t e p i n t h e c o n v e r s i o n o f 5 a - c h o l e s t a n - 6 - o n e i n t o 6 - o x a - 5 a - c h o l e s t a n e . 1 8 4 The mechanism o f t h e f o r m a t i o n o f oxa s t e r o i d s from 3 - h y d r o x y - A s - s t e r o i d h y p o i o d i t e s has been i n v e s t i g a t e d . 18' P h o t o l y s i s of s e v e r a l s t e r o i d a l l a c t o l s i n t h e p r e s e n c e of i o d o s o b e n z e n e d i a c e t a t e a n d i o d i n e a l s o l e a d s t o t h e p r o d u c t i o n o f a l k o x y r a d i c a l s , 18' a n d i o d o s o b e n z e n e d i a c e t a t e h a s b e e n shown t o b e a n e f f i c i e n t r e a g e n t f o r t h e p h o t o c h e m i c a l l y i n d u c e d o x i d a t i v e d e c a r b o x y l a t i o n o f c a r b o x y l i c a c i d s . 187 References 1

2 3 4 5 6

7 8 9 10

11 12 13 14 15 16 17 18 19 20 21 22 23 24

Ya.A.Levin, T.G.Valeeva$ I.P.Gozman, and E.I.Gol'dfarb, Zh. Obshch. Khim., 1985, 55, 1290 (Chem. Abstr., 1986, 34140). J - D - D r u l i n e r , P.J.Krusic, G.F.Lehr, and C.A.Tolman, J. Org. Chem., 1985, 50, 5838. ,, P.L.Muller-Remmers and K.Jug, J . Am. Chem. SOC., 1985, 7275. G.A.Ganzer, R.S.Sheridan, and M.T.H.Liu, J. Am. Chem. SOC., 1986, 1517. A.K-Mal'tsev, P.S.Zuev, and O.M.Nefedov, Izv. Akad. Nauk SSSR, Ser. Khim., 1985, 957 (Chem. Abstr., 1985, 103, 122837). 99. M.A.Kesselmayer and R.S.Sheridan, J. Am. Chem. SOC., 1986, M.A.Kesselmayer and R.S.Sheridan, J. Am. Chem. SOC., 1986, 844. M.T.H.Liu, J. Chem. SOC., Chem. Commun., 1985, 982. M.T.H.Liu and R.Subramanian, H.Tomioka, T.Sugiura, Y.Masumoto, Y. Izawa, S. Inagaki, and K. Iwase, J. Chem. Soc., Chem. Commun., 1986, 693. M.T.H.Liu and R.Subramanian, Tetrahedron L e t t . , 1985, 26, 3071. M.T.H.Liu and R.Subramanian, J. Phys. Chem., 1986, 90, 75. 929. W.Adam, K.Hannemann, and R.M.Wilson, J. Am. Chem. SOC., 1986, W.Adam, K.Hannemann, and R.M.Wilson, Angew. Chem. I n t . Ed. Engl., 1985, 24, 1071. L.Van H i j f t e and R.D.Little, J. Org. Chem., 1985, 2, 3940. 794. F.-G.KL&ner, V.Glock, and H.Figge, Chem. Ber., 1986, W.Adam, T.Opp&lander, and G.Zang, J. Org. Chem., 1985, 3303. W-Adam, O.De Lucchi, K . H i l l , E.M.Peters, K.Peters, and H.G.Von Schnering, Chem. Ber., 1985, 3070. WeAdam and K . H i l 1 , J. Am. Chem. Soc., 1985, 3686. D-E-Reedich and R.S.Sheridan, J. Am. Chem. SOC., 1985, 3360. 4554. B.F.LeBlanc and R.S.Sheridan, J. Am. Chem. Soc., 1985, 4203. M.Christ1 and B-Mattauch, Chem. Ber., 1985, A.G-Schultz, K.K.Eng, and R.K.Kullnig, Tetrahedron L e t t . , 1986, 27, 2331. W. Adam, LHannemann, E. M.Pe t e r s , K. Pe t e r s , H.G.Von Schnering, and R.M. Wilson, Angew. Chem. I n t . Ed. Engl., 1985, 24, 421.

104,

107,

108,

108, 108,

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-

119, 2,

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107, 107,


45 1

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(w.

-

c,

Photochemistry

452 69 70 71 72 73 74 75 76

77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114

W.Ando, Y.Kumamoto, and T.Takata, Tetrahedron L e t t . , 1985, 26, 5187. U.Burger and D-Zellweger, Helv. Chim. Acta, 1986, 69, 676. 1127. E.J.Walsh and G.B.Stone, Tetrahedron L e t t . , 1986, J.E.Baldwin, J.K.Cha, and L.I.Kruse, Tetrahedron, 1985, 41, 5241. R.D.Miller and W.Theis, Tetrahedron Lett., 1986, 27, 2447. R.R.Gallucci and M.Jones, J. Org. Chem., 1985, 2, 4404. F.Kunisch, K.Hobert, and P.Welze1, Tetrahedron L e t t . , 1985, 26, 5433. V.A.Nikolaev, N.N.Khimich, and I.K.Korobitsyna, Khim. G e t e r o t s i k l . Soedin., 1985, 321 (Chem. Abstr., 1985, 87818). C.J.Moody, C.J.Pearson, and G.Lawton, Tetrahedron L e t t . , 1985, 2,3167. A.Baceiredo, G.Bertrand, and G.Sicard, J. Am. Chem. SOC., 1985, 107, 4781. 1395. A.M.Brouwer and H.J.C.Jacobs, Tetrahedron L e t t . , 1986, R.J.Sundberg and E.W.Baxter, Tetrahedron L e t t . , 1986, 2687. A-P-Vorotnikov, E.Ya.Davydov, and D.Ya.Toptygin, Izv. Akad. Nauk SSSR, Ser. K h i m . , 1985, 1275 (Chem. Abstr., 1986, 19304). W.Ortmann and E.Fanghaene1, Z. Chern., 1985, 109. H.Baumann, H.G .O.Becker, K.P .Kronfeld, D. P f e i f e r , and H. J .Timpe, J. Photochem., 1985, 28, 393. M.T.Nguyen, Chem. Phys. L e t t . , 1985, 290. C.G.Krespan, J. Org. Chem., 1986, 2,332. H.Quast, P.Eckert, and B . S e i f e r l i n g , Chem. Ber., 1985, 3535. A. Baceiredo, G B e r t r a n d , J .Pa Maj o r a l , F .E .Anba, and G. Manue 1, J. Am. Chem SOC., 1985, 3945. G.Raabe, H.VanEik, R.West, and J.Mich1, J. Am. Chem. SOC., 1986, 671 K.Banert, Tetrahedron L e t t . , 1985, 26, 5261. M.J.Torres, J. Zayas, and M.S.Platz, Tetrahedron L e t t . , 1986, 2 7 , 791. T.-Y.Liang and G.B.Schuster, J. Am. Chem. Soc., 1986, 546. S.Murata, T. Sugawara, and H. Iwamura, J. Am. Chem. SOC., 1985 6317. L.M.Gornostaev and T.I.Lavrikova, Khim. G e t e r o t s i k l . Soedin. 1985, 956 (Chem. Abstr., 1986, 5813). H.Sawanishi, H.Sashida, and T.Tsuchiya, Chem. Pharm. B u l l . , 1985, 33, 4564. D.I.Pate1, E.F.V.Scriven, R.K.Smalley, H.Suschitzky, and D.1 . .C. Scopes, J. Chem. SOC., P e r k i n Trans. 1, 1985, 1911. H. Sawanishi and T.Tsuchiya, Chem. R.A.Abramovitch, B.Bachowska, and P.Tomasik, Pol. J. Chem., 1984, 58, 805. R.S.Gairns, C.J.Moody, and C.W.Rees, J. Chem. SOC., Chem. Commun., 1985, 1818 R.S.Gairns, C.J.Moody, and C.W.Rees, J. Chem. SOC., P e r k i n Trans. I, 1986, 501. S.A.Glover, A-Goosen, S.L.Golding, and C.W.McCleland, S. Afr. J. Chem., 1985, 5. G.B.V.Subramanian, A.Mehrotra, and K.Mehrotra, Chem. Ind.(London), 1985, 379. E.Hassinen, P.Riepponen, K.Blomqvist, K.Kalliorinne, A.M.Evseev, and J . K o s k i k a l l i o , I n t . J. Chem. Kinet., 1985, 1125. D.E.Reedich and R.S.Sheridan, J. Org. Chem., 1985, 50, 3535. M.Feldhues and H.J.Schgfer, Tetrahedron, 1985, 41, 4195. M.Feldhues and H.J.SchZfer, Tetrahedron, 1985, 4213. M.Feldhues and H.J.Schgfer, T e t r a h e d r o n , 1986, 42, 1285. R.Bartnik, Z.Cebulska, A.Laurent, and B.Orlowska, J. Chem. Research ( S ) , 1986, 5. D.Ranganathan, S.Bamezai, and P.V.Ramachandran, Heterocycles, 1985, 3, 623. J.Nally, N.H.R.Ordsmith, and G.Procter, Tetrahedron L e t t . , 1985, 26, 4107. Y.L.Chow and J.S.Polo, J. Chem. SOC., P e r k i n Trans. 2 , 1986, 727. D.Birch, J.D.Coyle, R . R . H i l 1 , and G.E.Jeffs, J. Chem. Soc., Chem. Commun., 1986, 293. D.H.R.Barton, D.Crich, and G.Kretzschmar, J. Chem. SOC., P e r k i n Trans. 1, 1986, 39. D.H.R.Barton, D.Crich, and P . P o t i e r , Tetrahedron L e t t . , 1985, 26, 5943. D.H.R.Barton, B.Lacher, and S.Z.Zard, Tetrahedron, 1986, 2325.

27,

103,

27, 27,

-

104, 2,

117,

s,

. 107,

-

108,

108,

8 ,

104,

2,

17,

3,

42,

107,


453

115 D.H.R.Barton, H.Togo, and S.Z.Zard, Tetrahedron Lett., 1985, 26, 6349. 116 D.H.R.Barton, B-Garcia, H.Togo, and S.Z.Zard, Tetrahedron Lett., 1986, 27, 1327. 117 D.H.R.Barton, D.Crich, Y.Hervi, PaPotier, and J.Thierry, Tetrahedron, 19t5, 41, 4347. 118 B. Sket, N. ZupanhE, and K.Zupan, Tetrahedron, 1986, 42, 753. 119 G.Kaupp, Chem. Ber., 1985, 118, 4271. 120 K.J.S.Aroba, J.R.Collier, D.J.Deodhar, M.M.Hesabi, and J.Hil1, J. Chem. Research ( S ) , 1985, 184. 121 E.Vedejs, T.H.Eberlein, D.J.Mazur, C.K.McClure, D.A.Perry, R.Ruggeri, E Schwartz, J.S.Stults, D.L.Varie, R.G.Wilde, and S.Wittenberger, J. Or&. 1986, 2,1556. 122 T.Sumiyoshi, W.Weber, and W.Schnabe1, 2, Naturforsch., A: Phys., Phys. Chem., Kosmophys., 1985, 40, 541. 685. 123 R-RmDaraji and A-Shah, Indian J. Chem., Sect. B, 1985, 124 K.-H.Duch&ne and F.Vogtle, Angew. Chem. Int. Ed. Engl., 1985, 2,885. edron Lett., 1985, 26, 115 Y.Fukazawa, J.Tsuchiya, M. Sobukawa, and S. Ita, 5473. 126 H.A.Staab, Ha-J-Hasselbach,and C.Krieger, Liebigs Ann. Chem., 1986, 751. 127 K.Tsujimoto, Y.Okeda, and M.Ohashi, J. Chem. SOC., Chem. Commun., 1985, 1803. 128 V.P.Rao and V.Ramamurthy, Synthesis, 1985, 526. and W.Sundermeyer, Chem. Ber., 1985, 118,4553. 129 A.Els&ser 130 H.P.Schuchmann and C.Von Sonntag Can. J. Chem., 1985, 63, 1833. 131 K.: t o l u e n e > b e n z e n e . 241

Poly

(E,N_-dimet hy l a m i d e )

c o n t a i n i n g pendant triphenylmethane leucohydroxide r e s i d u e s 242 undergoes a p h o t o - r e v e r s i b l e v i s c o s i t y change i n methanol. This i n t e r e s t i n g e f f e c t is associated with t h e r e v e r s i b l e leuco -triphenylmethyl

c a t i o n e q u i l i b r i u m shown i n Scheme 8

which a l s o g i v e s r i s e t o an i n t e n s i v e c o l o u r c h a n g e .

Local m o t i o n s o f a , w - b i s ( 1 - p y r e n e )

a l k a n e s and pyrene

-

l a b e l l e d poly(methy1 m e t h a c r y l a t e ) i n s o l u t i o n have been m e a s u r e d by p i c o - s e c o n d e x c i m e r

fluorescence spectroscopy.

243

I n t h i s s t u d y t h e formation of t h e polymers d u r i n g p o l y m e r i s a t i o n c o u l d b e a c c u r a t e l y m a i n t a i n e d by m e a s u r i n g excimer f l u o r e s c e n c e l i f e t i m e .

The p h o t o p h y s i c a l p r o p e r t i e s

of p o l y ( N - v i n y l c a r b a z o l e ) h a v e b e e n i n t e r p r e t e d on t h e b a s i s o f a s t u d y i n d i a s t e r e o i s o m e r s of 2 , 4 - d i ( ~ - c a r b a ~ o l y l ) $ ~ ~ I n t h i s work i t is c o n c l u d e d t h a t 95% o f t h e e x c i t a t i o n e n e r g y occurs w i t h chromophoresassociated w i t h s p e c i f i c excimer sites.

Excimer f o r m a t i o n i n v a r i o u s p o l y v i n y l c a r b a z a l e

s t r u c t u r e s h a s been found t o b e d i r e c t l y connected w i t h t h e T h u s , a n enhancement p h o t o c o n d u c t i v i t y of t h e p o l y m e r s . 245

i n excimer forming s i t e s g i v e s rise t o reduced c a r r i e r g e n e r a t i o n c a p a b i l i t y and hence a lower p h o t o c o n d u c t i v i t y .

IV: Polymer Photochemistry

483

PolyCN-(viny1oxy)carbonyl carbazole] has been prepared and found t o g i v e rise t o t w o d i s t i n c t t y p e s o f t r i p l e t e x c i m e r e m i s s i o n s 246 w h i l e i n p u r e p o l y ( 2 4 i n y l n a p h t h a l e n e ) t r a n s p o r t theory normally a p p l i c a b l e t o

t h e 3-dimensional

polystyrene for a s p a t i a l p e r i o d i c lattice d i d not apply i n t h i s case d u e t o a h i g h e r t r a n s p o r t r a t e i n t h e case of t h e f o r m e r . 247

The a c t i v a t i o n e n e r g y f o r r a d i a t i o n l e s s

d e c a y processes i n isobutylene-naphthylmethyl m e t h a c r y l a t e methyl methacrylategraft

copolymer h a s been found t o

c o r r e s p o n d t o t h a t a s s o c i a t e d w i t h r o t a t i o n o f t h e a-methyl g r o u p . 248

Relaxation t i m e s i n anthracene labelled

poly(E-vinylacetamide),poly ( & - v i n y l c a p r o l a c t a m ) End p o l y (N-vinylpYrolidine)have been found t o decrease markedly i n an o r g a n i c s o l v e n t owing t o t h e loss o f h y d r o p h o l i c i n t e r a c t i o n s i n t h e m o l e c u l e s . 249 I n t h e case o f a s c e n a p h t h a l e n e amylnitride and 2-vinylnaphthalene copolymers excimer formation is a s s o c i a t e d with next t o n e a r e s t neighbours

250

w h i l e i n n a p h t h a l e n e and a n t h r a c e n e labelled methyl methacrylate-acrylic

acid copolymers i n t r a m o l e u c l a r s i n g l e t

energy migration w a s s i g n i f i c a n t l y enhanced i n aqueous media 251 when c o m p a r e d w i t h n o n - a q u e o u s m e d i a . The e f f e c t o f s o l v e n t v i s c o s i t y o n t h e r a t e c o n s t a n t o f

eximer f o r m a t i o n h a s b e e n s t u d i e d f o r p y r e n e t e r m i n a t e d Two classes o f c o n f o r m a t i o n a l t h e o r y

p o l y a c r y l a t e s . 252

were r e q u i r e d t o e x p l a i n t h e r a t e c o n s t a n t b a s e d o n d i f f u s i o n a l and non-diffusional

effects.

Temperature

e f f e c t s o n t h e f l u o r e s c e n c e a n i s o t r o p y d e c a y of a n t h r a c e n e 253 l a b e l l e d polybutadiene have been measured i n t h e m e l t u s e d t h e r e s u l t s showed t h a t l o c a l o r i e n t a t i o n a l m o t i o n s f o l l o w e d t h e same t e m p e r a t u r e l a w a s f o r t h e m a c r o s c o p i c For p h e n y l mechanical p r o p e r t i e s o f t h e polymer. terminated polybutadiene, fluorescence' quenching i n s o l u t i o n h a s b e e n f o u n d t o b e d i f f u s i o n c o n t r o l l e d . 254 The composition o f s e v e r a l flavin-containing p o l y e l e c t r o l y t e s h a s been found t o i n f l u e n c e markedly t h e s t a t i c a n d dynamic p r o p e r t i e s of t h e f l u o r e s c e n c e e m i s s i o n o f t h e f l a v i n m o l e c u l e . The d e c a y of t h e a n i s o t r o p i c e m i s s i o n w a s f o r e x a m p l e , r e s o l v e d i n t o t w o relaxation t i m e s , t h e longest corresponding with

484

Photochemistry polymer chain motions whilst the shortest is associated Chiroptical with rotat ion of the flavin molecule.255 spectroscopy has been found t o be a powerful technique for the elucidation of complex excited-state interactions in 256 . For example, in novel arowatic chromophar ic polymers poly(a-aminoacids) such as poly(L-1-pyrenealanine) strong ground-state interactions between pyrenyl groups were observed to be in a helical arrangement along the polypeptide chain. Two excimericspecies were observed by fluorescence analysis, one with a negative circularily polarised fluorescence dissymmetry at 460 nm while the other had positive dissymmetry The latter was found to be dominant at wavelengths >500 nm. at lower temperatures. Fluorescence anisotropy decay measurements have been carried out on a series of 9,lO-dialkylanthracenes in polybutadiene with alkyl substituents rangingin the power from 6 to 16 methylene Such a study allowed a striation of the groups.257 orientation autocorrelation functions which were found to increase with an increase in the alkyl chain length. For fourteen carbon atoms or more this function corresponded closely to that for the 1 - 3 diffusion found in long-chain labelled polymers. Intra-coil sensitisation of the singlet excited state of 9,lO-diphenylanthracene and fluorescence tagged pOly(viny1pyrrolidone)has been found to depend 258 strongly on the size of the polymer coil in solution. Analysis of the fluorescence decay curves in water indicated that the intracoil process is static and that anthryl aggregation induces non-exponentiality in the fluorescence decay associated with a dynamic equilibrium between the singlet diphenyl-anthracene and a non-fluorescent dimer state. Further evidence was also presented to show that these polymers self-organise into hydrophobic and hydrophilic regions Energy migration in alternative and random copolymers of 2-vinylnaphthalene and methyl methacrylate/methacrylic acid was found to vary fitting into a single exponential in the former case and a three segmental fitting in the latter.259 Spectral and time dependent fluorescence analysis of meso and meso and r s - b i s c and =-2,4-di(l-pyrenyl)pentane 1-( 1-pyrenylIetherJether have shown that these compounds are

ZV: Polymer Photochemistry

485

excellent models for isotactic and heterotactic diads of poly(1-vinylpyrene). 260 No evidence for triplet excimer formation has been found on laser flash photolysis of diastereoisomers of bis [l-( l-and 2-naphthyl) ethyllethers.261 Stereoisomers that exhibit strong excimer fluorescence show a corresponding reduction in the quantum yield of intersystem crossing. Photophysical models and experimental techniques have been developed to allow the determination of the ratio of the intrinsic quantum yields of excimerto monomer emission Apparently to apply this method the in polymer blends.262 host matrix must be miscible with the guest fluorescent polymer at low concentrations and a suitable small probe molecule must be available to model the polymer monomer signal. The singlet and triplet state properties of poly (dimethylsilylene-co-methyl( l-naphthy1)silylenel have 263 been characterised and found to be highly solvent dependent. Strong excimerfluorescence is seen at room temperature in THF but at 77 K in methyltetrahydrofuran strong dimer emission is observed. The rate of energy migration in a photo-Fries reaction in naphthyl methacrylate copolymers is Fluorescence decays did not considered to be small.264 match those of the predicted Fryer model and was associated with inhomogeneous distribution of quenchers produced by the photo-Fries reaction. The phosphorescence emission properties of copolymers of poly(viny1benzophenone) closely match those of benzophenone itself apart from some E-type No triplet energy migration could delayed fluorescence.265 be observed. Changes in fluorescence depolarisation have been used to determine the coil-globule transitions for, anthryl labelled poly( styrene-maleic anhydride)266 and The depolarisation pyvinyl-labelled poly(viny1 acetate). 267 of fluorescence resulting from the transport of electronic excitations in chromophore containing polymers has been investigated as a technique for detecting non-ideal chain statistics268 and kinetic modelling of the 3-pulse dynamics of a monomer excimer pair has been attempted in the presence Segmented orientation of energy migration and detrapping.269 in polyisoprene networks has been maintained by fluorescence ~ lrevised his own work polarisat ion270 and Mor a w e t ~ ~has

486

Photochemistry on applications of synthetically labelled polymers. Chemiluminescencefrom polymers continues to attract wide-spread interest. The technique has been used as a sensitive monitor for the extent of Oxidation which occurs during the radiation sterilisation of In a similar respect plastic medical components.272 the technique has been used for measuring the extent of physical property changes in electron-beam irradiated polypropylene.273 The kinetics of aging of cellulosic materials has been correlated with their chemiluminescence 274’275 and in one study the presence of low molecular weight phenolics and hydrolysable hydrocarbons were assumed to play a minimal role in the chemiluminescence properties of hydrolysed wood material276 which in another study singlet oxygen was concluded to be important.2 77 Variations in the chemiluminescence emission from hydrolysed wood pulp have been associated with the intermittent decomposition of peroxides and hydroperoxides. 278 ’ 279 The chemiluminescence of poly [ 9-phenyl-l0-( 4vinylpheny1)anthracenel films has been found to be similar to that of 9,lO diphenylanthracene itself showing that the polymer backbone has little if any influence on this phenomenon !80 Other studies of interest include the chemiluminescence of weakly degraded polyethylene glycol ,281 residual initiators in PVC,282 polymer equipment 283 and a-tocatrienyl acetate.284 The radiothermoluminescence of polyethylene is associated with orientation of the tie molecules in the amorphous regions of the polymer285 while radiolysis products of hexabromotetrakisl(allyloxycarbony1)diphenyl oxide 286 quenched the radiothermoluminescence of this polymer. This type of emission has been used to investigate the cross-linking in butadiene rubber287 and also peel strength of polymer films.288 Thermoluminescence glow curves of butadiene-styrene rubber were associated with two processes, the first being independent and the second dependent on molecular relaxations289 which in doped polymethylmethzrylate containing anthracene and pyrene this emission was associated


487

with the recombination of polymer cations and aromatic Electroluminescence from polyethylene in anions.290 an electric field is associated with a double carrier injection mechanism acting at the metalpolymer interface. Spectra were directly related to the molecular structure of the polymer. Electroluminescence has also been observed from degassed (W,) and SF6 impregnated polyethylene when subjected to a divergent electric field and is associated with electron-hole recombination at luminescent centres present as deep traps between amorphous and crystalline regions.292 The electroluminescence of polyethyleneterephthalate has been found to be only weakly dependent upon temperature and is associated with electron injection from the electrode through the interfacial barrier and subsequent deactivation of the excited Ir.olecules to their groundA similar mechanism was proposed for state.293 polyethylene and polystyrene.294

,''

4

Photodegradation and Photooxidation Processes Interest in polymer photodegradation and oxidation processes is still widespread. Several reviews in this area have 295 appeared covering initiation mechanisms in polypropylene, kinetics and mechanisms in all polymers 296 coatings 297 and biphenol-type polymers.298 Other articles of topical interest include computer simulation of polymer weathering 299 photooxidation of polymer containing jet ESR as an early detection method of resin oxidation3'l and a comparison of light sources for weathering polymers.302 Polyolefins These continue to be the most widely studied materials. Detailed spectroscopic and mechanical testing studies on polyethylene have shown that whilst pre-crosslinking of the polymer gives enhanced oxygenated products, the mechanical properties are improved.303 Limitation of the photodegradation of crosslinked polyethylene is

4.1

488

Photochemistry associated primarily with diene chromophors and proceeds in an oxygenation process involving peroxy radicalsas shown In the case of silane crosslinked in Scheme 9.304 polyethylene hydroperoxidation rates during photoooxidation have been found to be the same as for normal low density Oriented polypropylene films have on grade polymer.305 the otherhand been found to exihibit better stability compared with that of unoriented film30' The reinforcing effect of crystalline films in the former case is attributed to the improvement in polymer stability. The photooxidation kinetics of branched polyethylenes has been found to be strongly influenced by processing history307 and the incorporation of poly(2,6-dimethyl-l,4-phenylene acid) has been found to suppress double bond formation during photooxidation.308 ESCA studies 309 on photooxidised low density polyethylene shows that oxidation rapidly 0 declines in the top 150 A of the surface . Using sandwich layers of polymer oxidation at the vinyl surface is found The to be twice as great as that at a 20 pm depth. mechanisms of thermal and photooxidation in octene-1 linear low density polyethylene have been found to be the same as those found for normal low density polyethylene.310 During photooxidation both isolated and parallel hydroperoxides are produced, the former being stable whilst the latter are fairly unstable at a temperature of 85OC. Surprisingly, variations in branching are concluded to have no effect on photooxidation rate. Uniaxial deformation of polyethylene and related polymers has been found to improve photostability of the polymers311 due to reduced oxygen permeability. This would be difficult to visualise particularly in view of ESCA work where photooxidation is a maximum on the surface of the polymer. Photooxidation of poly(4-methyl-l-pentene) results in oxidation of both the main chain as well as the pendant side chains. 312 Water transmission rates of polyethylene films have been altered by the photochemical irradiation of blendsof the polymer with acrylic monomers.313


489

D e t a i l e d ESR s t u d i e s on t h e p h o t o o x i d a t i o n of i s o t a c t i c p o l y p r o p y l e n e a t d i f f e r e n t t e m p e r a t u r e s showed t h a t d e c o m p o s i t i o n of t e r t i a r y h y d r o p e r o x i d e s is t h e key s t e p

i n i n i t i a t i o n and t h a t t h e N o r r i s h t y p e I p h o t o c l e a v a g e o f k e t o n e s is o n l y a minor c o n t r i b u t i o n t o f r e e r a d i c a l p r o d u c t i o n . 314

The photo-induced

c r o s s l i n k i n g of

p o l y e t h y l e n e by a n t h r a q u i n o n e h a s been a s s o c i a t e d n o t o n l y w i t h i t s p h o t o r e d u c t i o n by hydrogen atom a b s t r a c t i o n b u t a l s o by p r o d u c t s o f t h e p h o t o r e d u c t i o n p r o c e s s .

315

4 . 2 Poly(viny1 h a l i d e s )

P h o t o t h e r m a l d e h y d r o c h l o r i n a t i o n of PVC as s t u d i e d by derivative

u l t r a v i o l e t a b s o r p t i o n and f l u o r e s c e n c e

a n a l y s i s t e c h n i q u e s h a s shown t h a t c a r b o n y l and h y d r o p e r o x i d e g r o u p s a r e more i m p o r t a n t i n t h e i n i t i a t i o n s t e p s t h a n r e s i d u a l d o u b l e bonds. 316

O t h e r w o r k e r s however, have

shown t h a t r e s i d u a l u n s a t u r a t i o n i s p r i m a r i l y i m p o s s i b l e f o r t h e p r o d u c t i o n of h y d r o p e r o x i d e s and e v e n t u a l l y a , @ - u n s a t u r a t e d c a r b o n y l g r o u p s by Scheme 1 0 , t h e l a t t e r

317

b e i n g p r i m a r i l y r e s p o n s i b l e f o r t h e f l u o r e s c e n c e emission. The c o n c e n t r a t i o n of t h e l a t t e r s p e c i e s were a l s o found t o c o r r e l a t e c l o s e l y w i t h t h e p h o t o o x i d a t i v e s t a b i l i t y of t h e polymer.

The SbC13 c a t a l y s e d p h o t o c h e m i c a l

d e g r a d a t i o n of PVC h a s been a s s o c i a t e d w i t h an i o n i c i n t e r a t i o n between t h e SbC13 a n d p o l y e n e s e q u e n c e s .

318

C a t i o n i c p o l y e n i c s e q u e n c e s w i t h absorpti-on maxima from 500-900 c m were i d e n t i f i e d i n t h e polymer. Lubricants have been found t o p l a y l i t t l e , i f a n y , r o l e i n t h e p h o t o i n d u c e d o x i d a t i o n of PVC, 319 a l t h o u g h it s h o u l d b e pointed out t h a t o t h e r important a d d i t i v e s such a s metal c a r b o x y l a t e s t a b i l i s e r s w e r e n o t c o n s i d e r e d and i n commercial r e a l i t y s y n e r g i s t i c e f f e c t s may p r e v a i l . Low m o l e c u l a r weight waxes were found t o b e weak sensitisers.

The p h o t o s t a b i l i t y of p l a s t i c i s e d PVC i s

improved i n t h e p r e s e n c e of m e t a l o x i d e , p a r t i c u l a r l y Zn0.320 D i b a s i c l e a d p h o s p h i t e was found t o b e e x c e p t i o n a l l y good.

O t h e r w e a t h e r i n g s t u d i e s on

p l a s t i c i s e d PVC have examined l o s s of p l a s t i c i s e r ,321 ESR

Photochemistry

490

pO' -CH=CH-CH-CH2W

+

wCH=CH-C-CH,

HO ,

II

I

0

Scheme 10

-

CH2-

-

C H z-

CH -NH -C0 -CH2-

( P H)

X

1

ihv(hr340nm) -

CH2- NH

CO

I

hv (observed at

r*

CH

I

I

J . 1

1-+1- f -

/ c r 0t 0n i2 at i 0n

\h:o2

-CH2COOH

CHz-~H-NH-CO-CH2~

-

CH

(Po)

1

O2

CH

i

-N H -C0-CHz~

00.

1+pH

*OH

+

CHz-CO-NH-CO-

~CH2-CH-NH-CO-CHZ-

I

?

J.

-CH2-CH0

h = 3 4 0 nm)

pH

+ NHz-CO-CH2~

Scheme 11

CH


491

a n a l y s i s o f c o p o l y m e r s 3 2 2 a n d g e n e r a l p h o t o a g i n g .3 2 3 The s e n s i t i s e d p h o t o c h e m i c a l o x i d a t i o n o f PVC f i l m s h a s b e e n c h a r a c t e r i s e d by t h e f o l l o w i n g f e a t u r e s namely

-

(1) a l i n e a r d e p e n d e n c e o f o x i d a t i o n r a t e on l i g h t intensity;

(2) l o w h y d r o p e r o x i d e quantum y i e l d s ; (3) h i g h c a r b o n y l y i e l d s ; ( 4 ) l i n e a r g r o w t h of c a r b o n y l i c g r o u p s ; (5) short-links i n t h e oxidative chain; (6) f i r s t - o r d e r decay of peroxy r a d i c a l s ; (7) v a l e n c y m i g r a t i o n s o v e r v e r y l o n g d i s t a n c e s 324 i n t h e s o l i d polymer. ,

The t r a p p i n g of hydroxy r a d i c a l s was c o n s i d e r e d t o b e t h e b e s t way o f p r o t e c t i n g t h e p o l y m e r .

In another study i t was f o u n d t h a t PVC p h o t o o x i d a t i o n w a s a n o n - u n i f o r m

process involving photooxidation a t t h e s u r f a c e and photodehydrochlorination i n t h e h u l k . 325

4 . 3 Polyacrylates The quantum y i e l d o f t h e u l t r a v i o l e t l i g h t i n d u c e d photolysis

of polymethyl methacrylate has been found 326 t o be 0.03 chain emissions p e r absorbed photon. I n d e t a i l e d k i n e t i c s t u d i e s t h e p r e s e n c e of oxygen was f o u n d t o b e u n i m p o r t a n t i n t h e i n i t i a t i o n of t h e p h o t o x i d a t i o n of p o l y m e t h y l m e t h a ~ r y l a t ea n~d~ t~h e s e r v i c e l i f e of t h e polymer c o u l d b e p r e d i c t e d w i t h r e a s o n a b l e a c c u r a c y . 328 I r r a d i a t i o n of p o l y m e t h y l

m e t h a c r y l a t e w i t h an excimer l a s e r a t 1 9 3 nm p r o d u c e d a b l a t e d particles with temperatures

S 3000K. 329

4 . 4 P o l y a m i d e s a n d Copolymers The p h o t o o x i d a t i o n of n y l o n s 6 , 1 1 a n d 1 2 h a v e b e e n

e amined u n d e r b o t h s h o r t 300 nm c o n d i t i o n s . 330 p h o t o p r o d u c t s are i n d e p e n d e n t o f t h e s t r u c t u r e of t h e p o l y a m i d e a n d i n t h e f o r m e r case C-N bond s c i s s i o n of

Photochemistry

492

t h e amide g r o u p i s t h e key i n i t i a t i o n s t e p i n v o l v e d . A t l o n g e r w a v e l e n g t h s up t o 340 nm it is c l a i m e d t h a t

i n i t i a t i o n is t h e same a s t h a t f o r s h o r t - w a v e l e n g t h i r r a d i a t i o n w h e r e a s a t w a v e l e n g t h s >340 nm p h o t o o x i d a t i o n o f t h e p o l y m e r s i s i n d u c e d s o l e l y by i m p u r i t i e s s u c h a s carbonyl o r hydroperoxide groups.

B e t w e e n 300-340 nm a d u a l mechanism i n v o l v i n g b o t h C-N bond s c i s s i o n a n d i m p u r i t y chromophores is invoked.

Scheme 11 o u t l i n e s

t h e v a r i o u s o x i d a t i o n pathways involved.

I n t h e case of

t h e polyether-block-polyamides t h e p o l y e t h e r s e c t i o n s a r e highly prone t o r a d i a t i o n t o give hydroperoxides vhich a r e u n s t a b l e a b o v e 6 O o C a n d breakdown t o g i v e h e m i a c e t a l s which t h e m s e l v e s breakdown t o g i v e a l c o h o l a n d a l d e h y d e s 331 t h u s p r o t e c t i n g t h e polyamide s e c t i o n of t h e c h a i n . O t h e r w o r k e r s u s i n g l i g h t w a v e l e n g t h s >360 nm h a v e p r o p o s e d t h a t p o l y a m i d e s p h o t o x i d i s e i n t h e p r e s e n c e of 332,333 a-ketoimide groups.

4.5

P o l y s t y r e n e s a n d Copolymers

Weir h a s r e v i e w e d s p e c i f i c mechanisms,phenomena a n d u n s o l v e d p r o b l e m s i n t h e p h o t o d e g r a d a t i o n of p o l y s t y r e n e s 3 3 4 I n d e p t h s t u d i e s i n t h e d e g r a d a t i o n p r o d u c t s of p o l y s t y r e n e and t h e i r involvement i n i n d u c i n g p r o p e r t y changes h a s l e d

some w o r k e r s t o c o n c l u d e t h a t lower m o l e c u l a r w e i g h t f u n c t i o n s a r e more s u s c e p t i b l e t o o x i d a t i v e a t t a c k . 335 Quantum y i e l d s o f c h a i n s c i s s i o n p r o c e s s e s i n p o l y s t y r e n e s have been measured i n solution336 w h i l e o t h e r w o r k e r s h a v e examined t h e i n f l u e n c e o f d e g r a d a t i o n p r o d u c t s o n p h o t o d e g r a d a t i o n r a t e s m e a s u r e d by u l t r a v i o l e t a b s o r p t i o n s p e c t r o s c o p y .337

O p t i c a l f i l t e r e f f e c t s by

t h e p r o d u c t s o n t h e m e a s u r e d r a t e had t o b e c o r r e c t e d a n d s u i t a b l e e x p r e s s i o n s were d e r i v e d f o r t h i s p u r p o s e .

The r o l e of s i n g l e t oxygen i n t h e p h o t o o x i d a t i o n of s t y r e n e b u t a d i e n e c o p o l y m e r s h a s b e e n examined i n some d e p t h , 338-340 A n t h r a c e n e a n d 9 - m e t h y l a n t h r a c e n e were f o u n d t o b e e f f e c t i v e p h o t c s e n s i t e r s of t h e o x i d a t i o n of t h e copolymer a n d w a s a s s o c i a t e d w i t h t h e f o r m a t i o n of s i n g l e t oxygen


493

produced from the quenching of the lowest triplet excited state of the sensitiser by ground-state molecular oxygen. The singlet oxygen will then attack the double bond in the butadiene moiety. In the absence of any sensitiser the initiation of the photooxidation of the copolymer was accounted for on the basis of singlet oxygen formation via. a copolymer oxygen complex.340 Methane production through the depth of a film of poly(p-methoxy-styrene) on long wavelength irradiation ( X ' s > 3 0 0 nm) has been used in an attempt to provide information on depth profiles of polymer photodegrations.341

-

4.6

Polyesters Photodegradation of poly(ethyleneterephtha1ate) has been found to cause dramatic changes in the electrical properties of the polymer342 while in another study water extractable phthalate residue were f o ~ n d 3The ~ ~adhesion properties of poly(ethy1ene terephthalate) have been 344 and infrafound to increase during photodegradation red changes in the photooxidation of vinyl acetate copolymers has indicated that hydroperoxide groups are the key photoinitiators.345 The photothermal oxidation of segmented copoly (etheresters) have been found to behave like two polymers with different portions of polyether. 346 The polymers of the general structure(17) apparently photooxidise in the a-position with respect to oxygen of the polyether segment to give hydroperoxides of the structure.'l8)The latter will then proceed to photolyse by the overall Scheme 12 to give esters, hemi-acetals and formates as products.

Photochemistry

494

OOH

I

Q

C-0-CH,

I

-

H

(18)

OOH

I

- C -0-C

H,

Q

I

H

6 I

+ HOa

-C-O-CH,I

I

H

J

- CO-O-CH,-

Esters

OH

I

*C-O-CH,

I

H

*

Hemiacetal

S c h e m e 12

Formates

IV: Polymer Photochemistry 4.7

495

Bisphenol A Polymers Bisphenol A-polycarbonate

does n o t undergo a photo-Fries

r e a r r a n g e m e n t when e x p o s e d t o l o n g

wavelength l i g h t i n

n i t r o g e n o r oxygen a t m o ~ p h e r e s ? ~ ~t hI ne a b s e n c e o f oxygen a n d w i t h l i g h t of w a v e l e n g t h s 4) 3 B i d d l e t J . R . (5) 1 7 Bideau,' M. ( 1 ) 192; ( 5 ) 163 B i e r i , J.H. (3.2) 68; ( 3 . 4 ) 182 B i g l e r , P. (3.4) 38 Bignozzi, C.A. (2.1) 92 B i l a l , B.A. ( 2 . 1 ) 209 (3.2) B i l l h a r d t , U.-M. 103, 104 Binana-Lirnbele, W. (1) 282 Bingmann, H . ( 3 . 3 ) 105,

Author Index

558 106; (3.6)

100

Binkley, R.W. (3.1) 52 Birch, D. (3.2) 120; (3.7)

111

Birch, D . J . S . (1) 27, 55 Birney, D.M. (3.2) 119 Biryukov, V.P. (4) 429 Bisby, R.H. (1) 145, 398 Bischofberger, N. (3.1) 35; (3.3) 133, 135

133; (3.7)

Biseau, M. (2.1) 20 Bishop, A.R. (4) 188 Bitai, I. (4) 67 Bityurin, M.N. (4) 378 Bjerring, P. (3.2) 101 Bjoerkling, F. (3.5) 79 Blagov, S.N. (4) 429 Blaha, J.P. (2.2) 87, 92 Blais, N.C. (2.3) 34 Blanchard, D . J . (1) 17 Blanco, M. (4) 321, 424 Blaney, D.G. (2.1) 98; ( 5 ) 96 Blasse, G. (2.1) 1 Blatt, E. (1) 351 Blazej, A. (3.3) 12 Blenkinsop, R.E. (5) 15 Blinov, 1.1. (2.1) 182 Blornqvist, K. (3.7) 102 Blondeel, G. (5) 127 Blount, J.F. (3.1) 17;

Bolognese, A. (3.5)

41;

(3.6) 61

Bolte, M. (2.1) 53, 54 Bolton, J . R . (4) 226; (5) 13, 126, 128, 132

Bombieri, G. (2.2) 126 Bonacic-Koutecky , V. (3.6)

1

Bondybey, V.E. (1) 120 Bong, P.-H. (1) 234, 444; (3.3)

28

Bon Hoa, G.H. (1) 365 Bonneau, R . (1) 500; (3.2) (3.4)

105; (3.3) 9; 133 Bonsal, W.R. (1) 467 Bootsma, J.P.C. (4) 255 Borden, P.G. (4) 55 Borgarello, E. (2.1) 22, 178; (5) 211, 212 Borisevich, Y.E. (1) 471 Borkman, R.F. (1) 332 Borovik, A.S. (2.2) 137 Bortolus, P. (4) 314, 355, 393 Bos, F.C. (1) 422 BOS, H.J.T. (3.2) 70, 149, 165; (3.3) 94; (3.4) 142, (3.6) 26, 121, 180; (5) 43 Bosch, J. (3.4) 148 Bosch, P. (5) 151 Bott, D.C. (4) 186 (3.2) 65 Blow, D. (4) 190 Bottcher, H. (4) 196 Blumen, A. (1) 249 Bouas-Laurent , H. (2.3) 17; (3.4) 84, 169, 173; Bocarsley, A.B. (2.1) (3.6) 208 185; (2.2) 46 Bochu, C. (3.6) 35 Bouchard, D.A. (5) 112 Boeger, B.E. (1) 281 Bougeard, P. (2.2) 110 Boehm, H.P. (2.1) 28; (5) Boukouvalas, J. (3.5) 92, 93 178 Boens, N. (1) 36, 213; Boule, P. (3.4) 12 Bourdeaux, M. (1) 159 (4) 260 Boente, J.M. (3.7) 146 Bourdelande, J.L. ( 5 ) 93 Boettcher, W. (2.1) 108 Bourgin, D. (3.2) 133 Bogdantsaliev, J. (4) 353 Bowen, M. (3.2) 138, 139 Boghillo, V.I. (1) 472 Bowman, W.R. (3.7) 158, Bohne, C. (1) 497 163 Boikov, V.N. (2.1) 218 Boyd, M.K. (3.4) 106; Boileaus, S. (4) 246 (3.5) 52 Bois-Choussy, M. (3.7) Bragatssvilli, V.N. (2.3) 46 165 Boivin, S. (4) 246 Branca, S . J . (3.3) 108 Bojarski, C. (4) 238, 240 Brand, L. (1) 42-45, 321, Bokadia, M.M. (3.5) 95, 333 Brandt, 0. (1) 292 114 Bokobza, L. (3.5) 97 Brasitus, T.A. (1) 400 Boldridge, D.W. (1) 121 Braslavsky, S.E. (1) 60, Bolivar, R.A. (3.1) 44, 479 45; ( 3 . 4 ) 4 6 ; ( 3 . 5 ) 13, Brauer, H.D. (3.5) 98 14 Braun, C. (2.1) 30 Bolletta, F. (2.1) 104 Braun, D. ( 4 ) 120, 1 2 1

Braun, M. (2.1) 122 Braunschweig, F. (4) 63 Bravar, M. ( 4 ) 335, 342 Braven, B. (4) 363 Bray, B.L. (3.7) 145 Bray, R.G. (2.2) 52 Brearley, A.M. (1) 223, 232

Brecht, E. (1) 197 Breckenridge, W.H. (2.2) 12

Breen, P.J. (1) 359 Brenner, H.C. (1) 448 Brenner, K. (1) 446 Brewer, K.J. (2.1) 129; (5) 60

Briere, R. (2.2) 75 Briggs, L.M. (4) 394, 395 Bright, F.V. (1) 40 Brillante, A. (1) 112 Brillas, E. (5) 93 Brink, P.R. (1) 410 Brisirnitzakis, A.C. (3.2) 107

Brittain, H.G.

(2.1) 203, 205, 206, 210-213, 215 Brodbeck, H. (3.2) 133

Brokatzky-Geiger, J . (3.3)

105, 106; (3.6)

100 Bromberg, A. (1) 140; (3.5)

134

Bronstein-Bonte, I. (1) 221

Brook, A.G.

(2.3) 19; 4; (3.4) 156; 198, 199 Brooke, G.M. (3.4) 42 Brookfield, R.L. (1) 218 Brouwer, A.M. (3.3) 56; (3.7) 79 Browett, W.R. (2.1) 239 Brown, D.W. (1) 246 Brown, P.E. (1) 295; (3.3) 23 Brown, T.L. (2.2) 64 Briiggemann, K. (3.6) 94 Brugger, P. (3.3) 86 Bruice, T.C. (2.1) 52 Brummer, J . G . (2.1) 56 Brune, H.A. (3.3) 51-55 Bruno, G. (2.2) 126 Brunschwig, B.S. (2.1) 109 Brus, L.E. (1) 316 Bryant, L.R.B. (3.2) 141 Bryce-Smith, D. (3.4) 21, 22, 53 Buchachenko, A.L. (3.1) 25 Buchardt, 0. (3.2) 101 Buchholz, H. (3.1) 4 2 ; (3.3) (3.6)

559

Author Zndex ( 3 . 6 ) 76

Buchler, J.W. ( 2 . 1 ) 135 Buckland, S.J. ( 3 . 7 ) 30 Buechler, J. ( 2 . 1 ) 242; ( 5 ) 73

Buenzli, J.C.G. ( 2 . 1 ) 1 9 6 , 197

Buerbanner, J. ( 4 ) 269 Buffel, D.K. ( 3 . 4 ) 5 7 ; ( 3 . 6 ) 127

Cameron, R.E. ( 2 . 1 ) 1 8 5 ; ( 2 . 2 ) 46

Campa, C. ( 5 ) 151 Camparini, A. ( 3 . 6 ) 56 Campillo, A.J. ( 1 ) 6 4 , 65 Camps, J. ( 5 ) 9 3 , 151 Canas, L.R. ( 5 ) 42 Canonica, L. ( 3 . 2 ) 64 Canonica, S . ( 1 ) 2 8 , 9 4 , 119

Cava, M.P. ( 3 . 4 ) 122-124; ( 3 . 6 ) 2 5 , 159

Cavanagh, R.R. ( 4 ) 243 Cavatorta, P. ( 1 ) 390 Cavazza, M. ( 3 . 2 ) 1 9 Cazeau, P. ( 1 ) 162 Cazeau-Dubroca, C. ( 1 ) 162

Cebulska, 2. ( 3 . 1 ) 5 5 ; ( 3 . 7 ) 107

Cecchi, L. ( 5 ) 20 Cech, F. ( 3 . 2 ) 103 67 Celander, D.W. ( 3 . 4 ) 62 Buku, A. (1) 334 Cellucci, T.A. ( 2 . 1 ) 69 Bulgakov, R.G. ( 2 . 3 ) 57 95 Bulinski, A.T. ( 4 ) 292 Cao, Y. ( 3 . 3 ) 11, 8 7 , 109 Cen, J. ( 4 ) 399 Cerfontain, H. ( 3 . 2 ) 6 9 , Buma, W.J. ( 1 ) 422 Capponi, M. ( 3 . 2 ) 129 102 Bunce, N.J. ( 3 . 4 ) 6 9 , 7 0 , Capps, N.K. ( 3 . 6 ) 169 Cernak, V. ( 4 ) 9 7 , 133 Carassiti, V. ( 2 . 1 ) 7 1 ; 7 8 ; ( 3 . 6 ) 155 Cesca, S. ( 4 ) 141 ( 2 . 2 ) 99 Buono-Core, G.E. ( 2 . 1 ) Cha, J.K. ( 3 . 7 ) 72 Cardenas, J. ( 3 . 2 ) 49 168 Cha, Y. ( 3 . 7 ) 4 0 , 52 Burbo, E.M. ( 3 . 5 ) 3 1 , 32 Ca-rdona, R. ( 2 . 2 ) 136 Chadda, S.K. ( 3 . 4 ) 11 Cargill, R.L. ( 3 . 2 ) 25 Burger, U. ( 3 . 6 ) 1 1 9 ; Carless, H.A.J. ( 3 . 1 ) 1 9 , Chae, K.H. ( 1 ) 2 3 4 , 4 4 4 ; ( 3 . 7 ) 70 ( 3 . 2 ) 94; ( 3 . 3 ) 28; Burghardt, T.P. (1) 4 0 5 , 49 412 Carlini, C. ( 4 ) 213 ( 3 . 6 ) 24 Chae, Y.M. ( 3 . 2 ) 1 2 ; Burkhart, R.D. ( 4 ) 246 Carlsson, D.J. ( 4 ) 3 7 9 , Burlov, A.S. ( 2 . 1 ) 188 ( 3 . 6 ) 93 386 Burnett, J.F. ( 3 . 7 ) 1 5 7 , Carmely, Y. ( 3 . 5 ) 90 Chai, C.K. ( 4 ) 186 Chakraborty, K.B. ( 4 ) 408 166 Carpendale, N. ( 5 ) 34 Challa, G. ( 4 ) 255 Burns, V.W. ( 1 ) 385 Carr, P.W. ( 1 ) 6 Challal, D. ( 2 . 1 ) 1 3 7 ; Carrascosa, M. ( 5 ) 2 3 5 , Burshtein, A.I. ( 1 ) 2 5 1 ,

Bukhtiyarov, V.K. ( 2 . 1 )

252

Bursten, B.E. ( 2 . 2 ) 92 Buser, C.A. (1) 229 Bushby, R.J. ( 3 . 4 ) 1 2 5 ; ( 3 . 7 ) 28

Busse, R. ( 1 ) 310 Busulini, L. ( 4 ) 355 Butler, A.P. ( 1 ) 394 Buttafava, A. ( 4 ) 314,

Cao, D. ( 2 . 3 ) 30 Cao, H. ( 3 . 6 ) 7 Cao, W. ( 4 ) 8 6 , 8 7 , 9 0 ,

2 36

Carraway, E.R. ( 1 ) 34 Casal, B. ( 2 . 1 ) 137; ( 5 ) 117

Casal, H.L. ( 1 ) 8 0 , 461,

465; ( 3 . 1 ) 8 Casarin, M. ( 2 . 2 ) 8 1 Casey, C.P. ( 2 . 2 ) 9 4 Caspar, J.V. ( 2 . 1 ) 1 3 , 1 3 4 ; ( 2 . 2 ) 124 393 Butter, R.J. ( 4 ) 134 Cassano, A.E. ( 1 ) 7 0 Castedo, L. ( 3 . 4 ) 1 1 6 ; Buys, T.S.V. ( 3 . 2 ) 69 ( 3 . 7 ) 146 Castel, N. ( 1 ) 230 Cabaness, W.R. ( 4 ) 250 Castellan, A. ( 2 . 3 ) 1 7 ; ( 3 . 4 ) 8 4 , 169, 173; Cadet, J. ( 3 . 2 ) 9 9 ; ( 3 . 6 ) 87 ( 3 . 6 ) 208 Caffieri, S. ( 3 . 2 ) 48 Castello, A. ( 3 . 4 ) 7 3 Cai, 2. ( 2 . 1 ) 225 Castelvetro, V. ( 2 . 1 ) 150 Calalini, L.H. ( 1 ) 494 Casti, T.E. ( 5 ) 145 Calderwood, T.S. ( 2 . 1 ) 52 Castle, R.N. 1 2 0 , 1 2 1 , Caldwell, R.A. ( 2 . 1 ) 6; 1 4 5 ; ( 3 . 6 ) 161 Castleman, A.W. ( 2 . 3 ) 2 (3.5) 7 ; ( 5 ) 8 Caldwell, W.E. ( 3 . 2 ) 25 Catalan, J. ( 1 ) 130 Calgari, S . ( 4 ) 105 Catalina, F. ( 4 ) 8 3 , 84 Calhorda, M.J. ( 2 . 2 ) 35 Cater, R.S. ( 3 . 4 ) 7 0 , 7 8 ; Callender, R.H. ( 1 ) 377 ( 3 . 6 ) 155 Callis, P.R. ( 1 ) 324 Cato, C. ( 1 ) 95 Calo, V. ( 3 . 5 ) 108 Caucik, P. ( 4 ) 403 Calvin, M. ( 5 ) 145 Caufield, C.E. ( 3 . 2 ) 7 3 , Calzaferri, G. ( 5 ) 4 , 209 74

( 5 ) 3 0 , 117

Challiner, J.F. ( 3 . 2 ) 141 Chamberlain, G. ( 3 . 2 ) 28 Chamberlain, S.D. ( 3 . 4 ) 1 0 2 ; ( 3 . 7 ) 1 7 0 , 171

Chambers, S. ( 4 ) 125 Chambron, J.C. ( 2 . 1 ) 1 2 8 ; ( 5 ) 59

Chan, C.K. Chan, K.H. Chan, M.G. Chan, S.S.

( 2 . 1 ) 205 ( 4 ) 386 ( 4 ) 142 (2.1) 27; ( 5 )

191

Chan, Y. ( 3 . 5 ) 88 Chance, M.R. ( 1 ) 367 Chander, K. ( 4 ) 308 Chandrasekaran, K. ( 2 . 1 ) 248; ( 5 ) 193

Chandross, E.A. ( 1 ) 174 Chang, C.-H. ( 1 ) 267, 395; ( 4 ) 259

Chang, H.C. ( 3 . 1 ) 1 0 , 11 Chang, L.C.P. ( 4 ) 223 Chang, M.C. ( 1 ) 20 Chang, Z. ( 4 ) 8 5 , 88 Chanon, M. ( 2 . 1 ) 1 8 0 ; ( 3 . 7 ) 167

Chapman, O.L. ( 3 . 7 ) 4 3 , 50

Charpiot, B. ( 3 . 1 ) 2 4 ; ( 3 . 4 ) 129

Author Index

560 Chasey, K.L. ( 3 . 3 ) 91 Chassot, L. ( 2 . 1 ) 175, 176

Chastanet, J. ( 3 . 7 ) 168 Chattopadhyay, N . ( 1 ) 133 Chattopadhyay, S.K. ( 1 ) 111, 476, 490

Chauveau, F. ( 5 ) 222 Chauvet, J . D . (1) 381 Che, M. ( 5 ) 168 Chelibanov, V.P. ( 2 . 3 ) 42 Chen, C.C. ( 3 . 3 ) 6 3 Chen, J. ( 3 . 5 ) 8 7 , 109 Chen, L.X.-Q. ( 1 ) 328 Chen, R.F. (1) 71 Chen, S. ( 4 ) 191 Chen, W.Y. ( 4 ) 297 Chen, Y. ( 3 . 5 ) 38; ( 4 ) 12 Cheng, C.-C. ( 1 ) 464; (3.1) 6

Cheng, C.P. ( 2 . 2 ) 6 2 , 63 Cherek, H. ( 1 ) 132, 348, 456

Cherkasov, V.K. ( 3 . 5 ) 28 Chermette, H . ( 2 . 1 ) 180 Chernysh, Yu.E. ( 3 . 6 ) 4 1 Cherry, W.R. ( 1 ) 283; (2.1) 84-86

Chervenkova, V. ( 3 . 5 ) 139 'Cheskis,S.G. ( 2 . 3 ) 35, 36

Chesnokov, S.A. ( 3 . 5 ) 28 Chetwynd-Talbot, J. (2.2) 8

Chevalier, J.L. ( 5 ) 20 Chevalier, Y. ( 5 ) 141 Chevychelor, V.A. ( 4 ) 56 Chew, J.-F.A. ( 1 ) 417 Chiao, Y.C. ( 4 ) 201 Chiba, M. ( 2 . 1 ) 145 Chiba, T. ( 3 . 2 ) 4 1 Chiba, Y. ( 3 . 5 ) 54 Chibisou, A.K. ( 1 ) 507 Chiellini, E. ( 4 ) 215 Chigladge, L.G. ( 5 ) 107 Childs, R.F. ( 3 . 4 ) 11 Chin, I.J. ( 4 ) 232 Chiorboli, C. (2.1) 92 Chirinos-Padron, A.J. ( 4 ) 295, 384, 419

Cho, J.-H. ( 3 . 4 ) 38 Cho, K . ( 4 ) 409 Cho, T.H. ( 3 . 2 ) 100; ( 3 . 6 ) 139

Chockalingam, K. ( 3 . 7 ) 144

Chodankar, N.K. ( 4 ) 447 Chodosh, D.F. ( 3 . 6 ) 170 Choi, I.S. ( 4 ) 237 Choi, J.H. ( 2 . 1 ) 4 3 Choi, K . Y . ( 2 . 1 ) 208 Chondhary, V. ( 4 ) 404

Chou, P.T. (1) 77, 193; ( 3 . 5 ) 58 Choudhry, G.G. ( 3 . 4 ) 86, 8 7 ; ( 3 . 5 ) 50 Chow, Y.L. (1) 8 6 ; ( 2 . 1 ) 168; ( 3 . 4 ) 58; ( 3 . 6 ) 142, 143; ( 3 . 7 ) 110 Chowdhury, M. ( 1 ) 133 Christensen, P . A . ( 2 . 1 ) 102, 240; ( 5 ) 113, 120 Christensen, R . L . ( 1 ) 26, 84 Christensen, S. ( 3 . 5 ) 78 Christl, M. ( 3 . 7 ) 22 Chu, C.H. ( 4 ) 45 Chu, D . Y . ( 2 . 1 ) 121 Chu, G . ( 1 ) 196 Chu, W.T. ( 4 ) 45 Chuang, C. ( 3 . 7 ) 46 Chuang, J.C. ( 4 ) 127 Chukovskaya, E.Ts. ( 2 . 2 ) 61 Chung, D.G. (1) 396 Chung, J.J. ( 2 . 1 ) 4 3 Chupka, E.I. ( 4 ) 274-279 Church, S.P. ( 2 . 2 ) 1 5 , 7 3 Ci, X. ( 3 . 5 ) 118 Ciano, M. ( 2 . 1 ) 142; ( 5 ) 99 Ciardelli, F. ( 3 . 6 ) 1 2 , 13; ( 4 ) 213, 220 Cik, G. ( 3 . 3 ) 12 Cilento, G. (1) 494 Claesens, F. (1) 30 Clark, J. ( 3 . 1 ) 46; ( 3 . 4 ) 155; ( 3 . 5 ) 15 Clark, S.F. ( 2 . 1 ) 155; ( 2 . 2 ) 112 Clark, T. ( 3 . 4 ) 94 Claudel, R. (1) 192 Clement, A. ( 3 . 4 ) 6 ; (3.6) 164 Clennan, E.L. ( 3 . 5 ) 67 Cloke, F.G.N. ( 2 . 2 ) 4 8 , 66 Closs, G.L. ( 1 ) 502 Coburn, J.T. ( 1 ) 33 409 Coghlan, M.J. ( 3 . 3 ) 47; (3.6) 50 Cohen, H. ( 2 . 1 ) 166 Cohen, R.E. ( 4 ) 117 Cohen, S.G. ( 3 . 5 ) 2 446 Colin, H. ( 3 . 1 ) 18 Collart, P. ( 4 ) 260 Collier, J.R. ( 3 . 7 ) 120 Collin, G.J. ( 3 . 3 ) 5 , 6 Collins, S. ( 2 . 3 ) 29; ( 3 . 6 ) 196 Comba, P. ( 2 . 1 ) 47 Come, J.H. ( 3 . 2 ) 11

Comi, D. ( 4 ) 113 Commes, K. ( 1 ) 341 Concepcion, J.I. ( 3 . 7 ) 187

Condie, C.C. ( 1 ) 337 Condorelli, G. ( 2 . 1 ) 70 Conesa, J.C. ( 5 ) 166 Connolly, J . S . ( 2 . 2 ) 112; ( 5 ) 1 3 , 126

Conte, J.C. ( 1 ) 257 Cook, D.R. ( 5 ) 126 Cooke, J . M . ( 4 ) 273 Cooksey, C.J. ( 2 . 2 ) 110 Cooper, S.L. ( 4 ) 137 Corbin, D.R. ( 3 . 1 ) 6 Corbin, G.A. ( 4 ) 117 Cornelisse, J. ( 1 ) 8 9 ; ( 3 . 4 ) 2 7 , 28, 31, 3 4 , 6 5 , 71 Correa da Silva, P.A. ( 2 . 1 ) 192 Cosito, C. ( 1 ) 404 Cossy, J. ( 2 . 3 ) 9; (3.2) 55 Costa, J. ( 3 . 6 ) 148 Costa, S.M.B. ( 2 . 2 ) 35 Costanzo, L.L. ( 2 . 1 ) 70 Cotsaria, E. ( 5 ) 134 Cottrell, C.E. ( 3 . 3 ) 47; ( 3 . 6 ) 50 Coulon, D.A. ( 4 ) 101 Courbon, H. ( 5 ) 175 Courtney, S.H. ( 1 ) 20; (3.3) 17 Couture, A. ( 3 . 6 ) 35 Cowlen, M.S. (1) 320 Cox, M.E. ( 4 ) 200 Coyle, J . D . ( 3 . 1 ) 2 ; ( 3 . 2 ) 1 2 0 , 141, 149, 150; (.3.3) 37; ( 3 . 6 ) 175, 180, 185, 189; ( 3 . 7 ) 111 Cozman, I . P . (3.7) 1 Crackel, R.L. ( 1 ) 313 Cragg, J.E. ( 3 . 2 ) 141 Craig, D.P. ( 1 ) 1 Creaser, 1.1. ( 2 . 1 ) 47, 110; ( 5 ) 9 8 Creed, D. ( 2 . 1 ) 6 ; ( 3 . 5 ) 42; ( 5 ) 8, 223 Creighton, J.R. ( 2 . 2 ) 30 Creutz, C. ( 2 . 1 ) 1 4 , 109 Crich, D. ( 3 . 7 ) 112, 113, 117 Crimmins, M.T. ( 3 . 2 ) 4 Cristol, S.J. ( 3 . 3 ) 4 6 , 93, 146-148; ( 3 . 4 ) 1620; (3.7) 178-180 Crivello, J . V . ( 4 ) 20, 21, 101 Croncher, M.D. ( 4 ) 202 Crosby, G.A. ( 1 ) 466;

561

Author Index ( 2 . 1 ) 5 6 , 162, 229; ( 2 . 2 ) 114 Cross, A.J. ( 1 ) 20 Croucher, M.P. ( 4 ) 248 Cruces Blanco, C. ( 1 ) 124 Csongar, C. ( 3 . 7 ) 3 7 , 38 Cuendet, P. ( 5 ) 187 Cuevas, A. ( 4 ) 424 Cui, G. ( 3 . 5 ) 1 4 7 , 148 Cuivas, A. ( 4 ) 321 Cukier, R.I. ( 1 ) 8 , 9 Culp, S.J. ( 3 . 3 ) 6 6 ; ( 3 . 6 ) 132 Cundall, R.B. ( 1 ) 101, 1 4 5 , 166, 398 Cuniberti, C. ( 4 ) 267 Cunningham, J. ( 5 ) 180 Cunningham, P.D. ( 3 . 2 ) 8 ; ( 3 . 4 ) 43 Cuppen, T.J.H.M. ( 3 . 4 ) 118 Currell, L.J. ( 1 ) 240; ( 3 . 3 ) 26 Cusso, F. ( 5 ) 235, 236 Cusumano, M. ( 2 . 2 ) 126 Cutler, A.R. ( 2 . 2 ) 125 Czochralsk, B. ( 1 ) 323

Dabestani, R. ( 3 . 4 ) 51 Daems, D. ( 1 ) 36 Dagen, A.J. ( 1 ) 382 Da Graca, M. ( 2 . 1 ) 216 Dai-Ho, G. ( 3 . 6 ) 137 Dailey , W.P ( 3 . 3 ) 7 3 Daino, Y. ( 3 . 3 ) 6 8 , 69 Dale, R.E. ( 1 ) 398 Dall-Acqua, F. ( 3 . 2 ) 48 Dallinger, R.F. ( 2 . 1 ) 88 Dalores Baena, M. ( 1 ) 369 Dalton, J.C. ( 2 . 3 ) 1 ;

.--

( 3 . 6 ) 194

Dalton, J.R. ( 3 . 2 ) 25 Daltrozzo, E. ( 1 ) 210 Daney, M. ( 2 . 3 ) 1 7 ; ( 3 . 4 ) 1 6 9 , 173

Daniel, C. ( 2 . 2 ) 103 Danieli, B. ( 3 . 2 ) 64 Danielsen, P.L. ( 4 ) 187 Danielzik, B. ( 4 ) 329 Danko, S . ( 1 ) 376 Dankowski, M. ( 3 . 7 ) 139 Danziger, J.L. ( 1 ) 331 Daraji, R.R. ( 3 . 2 ) 1 5 2 ; ( 3 . 7 ) 123

Darbarwar, M. ( 1 ) 199 Darcy, P.J. ( 3 . 4 ) 141 Dardoux, M. ( 2 . 1 ) 2 0 ; ( 5 ) 163

Darey, M.C.P. ( 3 . 2 ) 34 Darlak, K. ( 1 ) 350 Darmanyan, A.P. ( 3 . 5 ) 63

Darwent, J.R. ( 2 . 1 ) 6 4 ; (5) 79

Das, P.K. ( 1 ) 1 1 1 , 315, 455, 487, 124; 136; 136

463, 473, 476, 490; ( 3 . 2 ) 6 3 , ( 3 . 3 ) 6 4 , 135, (3.6) 54; (3.7)

Das, S. ( 2 . 1 ) 194 da Silva, A.G. ( 1 ) 257 Daub, G.H. ( 1 ) 100 Dauben, W.G. ( 3 . 2 ) 3 ; ( 3 . 3 ) 7 7 , 81

Daudey, J.P. ( 2 . 2 ) 8 0 D'Auria, M. ( 3 . 4 ) 9 7 , 9 8 ; ( 3 . 7 ) 149, 150

Dave, V. ( 3 . 2 ) 21 Davenport, L. ( 1 ) 4 4 , 4 5 , 321, 398

David, C. ( 4 ) 163 David, P.G. ( 2 . 1 ) 192 Davidson, G.A. ( 1 ) 370 Davidson, R.S. ( 1 ) 1 7 3 , 475; ( 2 . 1 ) 2 3 ; ( 3 . 3 ) 141; ( 3 . 5 ) 105; (3.7) 155; ( 4 ) 456; ( 5 ) 172, 206 Davies, A.N. ( 1 ) 19 Davies, G.M. ( 3 . 6 ) 169 Davies, H.G. ( 3 . 1 ) 30 Davis, H.F. ( 3 . 2 ) 63 Davoust, J. (1) 75 Davydov, E.Ya. ( 3 . 7 ) 81 Day, J.P. ( 2 . 2 ) 66

Deal Olivera, M.E.C.D. (1) 145 DeArmond, M.K. ( 2 . 1 ) 48 de Bernardez., E.R. ( 1 ) 70

De Boer, T.J. ( 3 . 5 ) 70 De Bruyn, V.H. ( 3 . 4 ) 6 4 ; ( 3 . 6 ) 74

Decicco, C. ( 3 . 2 ) 28 Dedolph, D.F. ( 3 . 7 ) 1 5 9 , 160

Defay, N. ( 3 . 4 ) 115 Degani, Y. ( 1 ) 3 0 2 ; ( 2 . 1 ) 125; ( 3 . 5 ) 2 6 ; ( 5 ) 1 0 9 , 110 Degl ' Innocenti, A. ( 2 . 3 ) 18 DeGraff, B.A. ( 1 ) 3 4 ; (2.1) 112 Degrief, H. ( 1 ) 201 De Guidi, G. ( 2 . 1 ) 70 de Haas, M.D. ( 1 ) 109 de Haut de Sigy, A. ( 3 . 4 ) 8 4 ; ( 3 . 6 ) 208 Deibel, M.R. (1) 344 Deiker, C. ( 4 ) 69 De Kanter, F.J.J. ( 3 . 4 ) 3 De Keukeleire, D. ( 3 . 2 )

2 7 ; ( 3 . 6 ) 205; ( 5 ) 127

De Lange, W.G.J. ( 2 . 2 ) 58 de la Rosa, F.F. ( 5 ) 12 De la Rosa, M.A. ( 3 . 5 ) 40; ( 5 ) 12

Delcourt, M.O. ( 2 . 1 ) 1 6 4 ; ( 5 ) 105, 106

De Leeuw, F.A.A.M.

(3.2)

99

Delfini, M. ( 4 ) 215 Del Giacco, T. ( 3 . 5 ) 110 Dell'Amico, M. ( 1 ) 159 Dellonte, S. ( 1 ) 8 1 , 90 DeLoach, J.A. ( 3 . 2 ) 4 De Lucchi, 0 . ( 3 . 2 ) 8 6 ; ( 3 . 6 ) 1 5 8 , 171; ( 3 . 7 ) 18 De March, P. ( 5 ) 9 3 , 151 Demas, J.N. ( 1 ) 3 4 ; ( 2 . 1 ) 112 de Mayo, P. (1) 5 1 , 312, 314; ( 3 . 1 ) 3 2 ; ( 3 . 2 ) 21; (3.3) 14, 21; ( 3 . 4 ) 164; ( 5 ) 216 Demchenko, A.P. ( 1 ) 278 De Mico, A. ( 3 . 4 ) 9 7 , 9 8 ; ( 3 . 7 ) 1 4 9 , 150 Demmer, D.R. ( 1 ) 339 Dempsey, M.E. ( 1 ) 320 Demuth, M. ( 3 . 2 ) 8 8 , 89 Demuynck, J. ( 2 . 2 ) 103 Denisov, V.Ya. ( 3 . 2 ) 166 Den Ouden, B. ( 3 . 3 ) 9 4 ; ( 5 ) 43 Densley, R.J. ( 4 ) 292 Deodhar, D.J. ( 3 . 7 ) 120 De Oliveira, S.M. ( 2 . 2 ) 69 De Paoli, M.A. ( 2 . 2 ) 6 9 ; ( 4 ) 313 Depew, M.C. ( 3 . 2 ) 164 Derker, C. ( 4 ) 70 Derrick, J.M. ( 2 . 1 ) 44 Dervan, P.B. ( 5 ) 131 De Ryck, P.H. ( 2 . 3 ) 52 Deschaux, M. ( 2 . 1 ) 207

De Schryver, F.C. (1) 3 6 , 201, 213, 330, 346; ( 2 . 1 ) 8 9 ; ( 4 ) 244, 260, 261 Deshayes, H. ( 3 . 5 ) 47 de Silva, A.P. ( 3 . 4 ) 143 Desilvestro, J. ( 2 . 1 ) 100; ( 5 ) 119 Deslauriers, H. ( 3 . 3 ) 5 , 6 Desvergne, J.P. ( 2 . 3 ) 1 7 ; ( 3 . 4 ) 8 4 , 169, 1 7 3 ; ( 3 . 6 ) 208 de Vaal, P. ( 3 . 4 ) 27 De Ville, G.Z. ( 3 . 4 ) 126 Devys, M. ( 3 . 5 ) 124

Author Index

562 Dewar, J.C. ( 2 . 2 ) 9 2 ; (3.6) 196

Dewey, T.G. ( 1 ) 373 de Wolf, W.H. ( 3 . 3 ) 75; (3.4) 3

De Zeeuw, P. (3.3) 88 Dhawan, S.N. (3.5) 7 Dias, A.R. ( 2 . 2 ) 35 Diaz, E. ( 3 . 1 ) 3 1 ; (3.2) 49

Dibenedetto, J. ( 2 . 1 ) 4 Dickens, B. (49 328 Dickinson, J.T. ( 4 ) 288 Di Cocco, M.E. ( 4 ) 215 Dietz, F. ( 1 ) 3, 241; ( 4 )

Donnigue, R.P. ( 4 ) 222 Donohue, T. ( 2 . 1 ) 224 Dopp, D. ( 3 . 4 ) 4 7 , 153 Dordet, Y. ( 5 ) 243 Dore, P. ( 2 . 1 ) 226 Dorofeev, Yn.1. ( 4 ) 327 Dorr, G. (5) 62 Doshi, S.V. ( 1 ) 504 Dote, T. ( 1 ) 239; ( 3 . 3 ) 29

Dotsenko, V.P. ( 4 ) 80 Doubleday, C.E. ( 1 ) 143,

144; ( 3 . 1 ) 27; (3.4) 131, 187 Doukas, A.G. ( 1 ) 377 Dovbii, E.V. ( 4 ) 414 441, 442 Diez-Masa, J.-C. ( 3 . 1 ) 18 Dowling, S.D. ( 4 ) 207 DiGiambattista, M. ( 1 ) Downs, A.J. ( 2 . 3 ) 38 Dracy, P.J. ( 3 . 2 ) 126 404 Dignam, M.J. ( 5 ) 230 Drake, J.M. (1) 200 Dikareva, L.M. ( 2 . 2 ) 37 Drake, R.C. ( 1 ) 26 Dillinger, R. ( 2 . 2 ) 4 1 Dreeskamp, H. ( 1 ) 149; (3.1) 13 Dillon, S.B. ( 5 ) 34 Dilung, 1.1. ( 1 ) 472; Dreher, B. (2.3) 4 8 , 49 (2.1) 55; ( 4 ) 9 1 Dressel, J. ( 3 . 3 ) 91 Ding, Y.S. ( 4 ) 137 Dressick, W.J. ( 2 . 1 ) 134 Dirk, N.A. ( 4 ) 205 Dreyfus, R.W. ( 4 ) 363 Disanayaka, B.W. ( 3 . 2 ) 32 Druliner, J.D. ( 3 . 7 ) 2 Disdier, J. ( 5 ) 175 Duan, Y. ( 2 . 1 ) 220 Dittrich, U. ( 3 . 6 ) 160 Dubey, R. ( 3 . 5 ) 9 4 , 9 5 , Dixon, D.A. ( 2 . 3 ) 7 114 Dixon, D.W. ( 3 . 5 ) 121 Dubois, D.L. ( 2 . 2 ) 112 Dmitrieva, N.B. ( 2 . 1 ) 136 Ducasse, A . ( 1 ) 286 Dmitrieva, S.Yu. ( 4 ) 323 Duchgne, K.-H. ( 3 . 7 ) 124 Do, S.R. ( 3 . 4 ) 144, 183; Dudeja, P.K. ( 1 ) 400 Dudek, M. ( 2 . 1 ) 60 (3.6) 45 Doany, F.E. ( 1 ) 236; Dudkiewicz, J. ( 1 ) 248 Duerner, G. ( 3 . 2 ) 103, ( 3 . 3 ) 24 Dobashi, S. ( 3 . 5 ) 73 104 Dobrov, E.N. (1) 392 Duerr, H. ( 5 ) 62 Dobvescu, V. ( 4 ) 345 Duesler, E.N. ( 3 . 2 ) 140; Dodsworth, E.S. (2.1) 131 ( 3 . 6 ) 126 Dopp, D. ( 3 . 6 ) 120, 153 Duhaime, R.M. ( 3 . 5 ) 20 Dogan, B.M.J. ( 3 . 3 ) 111 Dunford, H.B. (1) 497 Dogra, S.K. ( 1 ) 127, 136, Dung, D. ( 2 . 1 ) 100; ( 5 ) 137 119 Doherty, N.M. (2.2) 38 Dunkin, I.R. ( 3 . 7 ) 42, Dohmaru, T. ( 2 . 3 ) 28; 49, 61 ( 3 . 6 ) 203 Dunn, R . ( 4 ) 200 Doi, E. ( 3 . 6 ) 31 Dunn, D.A. ( 1 ) 500; ( 3 . 2 ) Doi, M. ( 3 . 4 ) 136; ( 3 . 6 ) 105 Dupuy, C. ( 2 . 1 ) 40 34 Doi, T. ( 4 ) 34 Duran, M. ( 5 ) 1 6 3 Domen, K. ( 2 . 1 ) 33; ( 5 ) Duran, N. ( 1 ) 413; ( 2 . 1 ) 2 5 , 27, 190 20; ( 4 ) 356 Domenech, J. ( 5 ) 201 Dureja, P. ( 3 . 3 ) 31, 32 Dominey, R.N. ( 3 . 3 ) 22 Durmis, J. ( 4 ) 386, 403 Dominguez, D. ( 3 . 7 ) 146 Durocher, G. ( 3 . 5 ) 138 Donald, L. ( 3 . 4 ) 104 Dutch, A. ( 1 ) 55 Donaldson, E.E. ( 4 ) 288 Dvornikov, I.V. ( 3 . 5 ) 6 2 Donati, D. ( 3 . 2 ) 3 9 ; Dzau. V.J. ( 1 ) 341 ( 3 . 6 ) 88, 125 Dzhabiev, T:S. ( 3 . 5 ) 31-

33; ( 5 ) 1 4 3

Dzhafarov, A.S. ( 4 ) 410 Dziemionowicz, T.S. ( 4 ) 273

Eaton, B. (2.2) 107 Eaton, D.F. ( 1 ) 150 Eaton, P.E. (3.3) 108 Ebara, N. (1) 485 Ebbesen, P. ( 3 . 2 ) 101 Ebbesen, T.W. (1) 154, 188, 423; (3.4) 85

Eberbach, W. ( 3 . 3 ) 105, 106; ( 3 . 6 ) 100

Eberlein, T.H. ( 3 . 7 ) 121 Eckert, P. (3.7) 86 Eckl, E. (3.6) 212 Ecoto, J. (3.1) 18 Ediger, M.D. (4) 222 Edmondson, G. ( 4 ) 452 Eftink, M.R. (1) 340 Egan, L.S. ( 4 ) 202 Egana, H. ( 4 ) 122 Egorochkin, A.N. ( 2 . 2 ) 27 Eguchi, S. ( 3 . 6 ) 37 Egusa, C. (3.2) 155; ( 3 . 6 ) 135

Eichenberger, H. ( 3 . 2 ) 57 Eichler, R. ( 4 ) 453 Eisenberg, M. ( 1 ) 403 Eisenberg, R. ( 2 . 2 ) 120 Eisenthal, K.B. ( 1 ) 226 Eisinger, J. ( 1 ) 54 Elbanowski, M. ( 2 . 1 ) 202 El-Bayoumi, M.A. (1) 125 Elferink, V.H.M. (3.2) 70; ( 3 . 4 ) 142; ( 3 . 6 ) 26

Elger, W. ( 3 . 1 ) 16 Elizarova, L.E. ( 4 ) 428 Elliott, C.M. ( 2 . 1 ) 97, 98; ( 5 ) 96

Ellis, A.B. ( 2 . 1 ) 217; ( 2 . 2 ) 138

Ellis, R.W. ( 3 . 7 ) 4 1 Ellul, H. ( 1 ) 218; (2.1) 247

Elofson, R.M. ( 5 ) 214 Elsaesser, A. ( 3 . 7 ) 129 Elsaesser, T. ( 1 ) 206 El-Sayed, M.A. (1) 58 Elschenbroich, C. ( 2 . 2 ) 38

El-Tamany, S. ( 3 . 4 ) 108 El'tsov, A.V. ( 3 . 3 ) 1 2 ; ( 3 . 6 ) 216

Emeren, A. ( 5 ) 215 Encinas, M.V. ( 1 ) 147, 288, 458; (3.5) 9

Endicott, J.F. (2.1) 7 , 49. 111

Endo; A. (2.2) 8 4

563

Author Index Endoh, M. ( 3 . 2 ) 122 Enea, 0. ( 5 ) 179 Eneinas, M.V. ( 4 ) 82 Eng, K.K. ( 3 . 1 ) 28; ( 3 . 7 )

127, 128; ( 3 . 6 ) 2 8 , 29

Feitelson, J. ( 1 ) 468 Fekarurhobo, G.K. ( 3 . 1 ) 49

Felberg, J.D. ( 3 . 7 ) 41 Engel, K. ( 2 . 2 ) 5 Felder, B.N. ( 4 ) 397 Engel, P.S. ( 3 . 7 ) 26 Felder, P. ( 2 . 3 ) 33 Engelhardt, H.E. ( 2 . 2 ) 22 Feldhues, M. ( 3 . 7 ) 104106 Engh, R.A. ( 1 ) 328 Feldkamp, L.A. ( 1 ) 411 Engst, P. ( 2 . 3 ) 45 Epling, G.A. ( 3 . 4 ) 8 8 , 89 Feldman, K.S. ( 3 . 2 ) 11 Felisberti, I.M. ( 4 ) 114 Epperlein, J. ( 3 . 6 ) 8 Equsa, S . ( 4 ) 256 Felker, P.M. ( 3 . 3 ) 20; ( 5 ) 131 Erbs, W. ( 2 . 1 ) 102; ( 5 ) Fellow, R. ( 3 . 6 ) 174 120 Fendler, J.H. (1) 292; Erker, C. ( 2 . 2 ) 4 , 5 ( 5 ) 215 Erman, B. ( 4 ) 270 Feng, L. ( 3 . 6 ) 63 Ernst, L. ( 3 . 4 ) 108 Ershov, Yu.A. ( 4 ) 414 Feng, S . ( 4 ) 106 Feng, X. ( 3 . 5 ) 80; ( 4 ) Ertl, P. ( 3 . 6 ) 2 85-88, 90,. 95 Eryavec, G. ( 2 . 1 ) 131 Fenzion, B. (5) 38 Escudero, J.L. ( 1 ) 169 Fernandez, A. ( 2 . 1 ) 242, Esplugas, S . ( 3 . 6 ) 148 243; ( 5 ) 7 2 , 73 Esquivel, B. ( 3 . 2 ) 49 Fernandez, P.F. ( 2 . 3 ) 40 Euler, K. ( 3 . 3 ) 74 Fernandez Martin, J.-A. Evans, C. ( 1 ) 419 Evans, S. ( 3 . 1 ) 34, 36 ( 3 . 3 ) 4 1 , 42; ( 3 . 6 ) 48 Evseev, A.M. ( 3 . 7 ) 102 Ferraudi, G. ( 1 ) 470; ( 2 . 1 ) 194; ( 2 . 2 ) 6 5 , Eychmuller, A. ( 3 . 6 ) 42 134 Eyring, E.M. ( 2 . 2 ) 60 Ferri, A. ( 2 . 1 ) 71 Ferrier, R.J. ( 3 . 2 ) 60 Fery-Forgues, S. ( 3 . 4 ) Fabian, W. ( 3 . 3 ) 123; 23

( 3 . 6 ) 9 5 , 102; ( 4 ) 448 Fabricius, N. ( 4 ) 329 Fagan, M.H. ( 1 ) 373 Fagan, P.J. ( 2 . 2 ) 94 Fakazawa, Y. ( 3 . 7 ) 125 Fan, F.R. ( 4 ) 280 Fan, M. ( 3 . 6 ) 122 Fan, P. ( 3 . 6 ) 122 Fanghaenel, E. ( 3 . 7 ) 82 Fanter, D.L. ( 4 ) 351 Fanton, E. ( 4 ) 310 Farwaha, R. ( 3 . 2 ) 21 Fasani, E. ( 3 . 4 ) 188; ( 3 . 6 ) 65 Fassler, D. ( 3 . 3 ) 7 9 ; ( 3 . 5 ) 9 9 , 149 Fatinikun, K.O. ( 4 ) 317 Fatti, G. ( 4 ) 220 Faucitano, A. ( 4 ) 314, 393 Faulkner, L.R. ( 1 ) 186 Faure, L. ( 1 ) 192 Fauri, J. ( 4 ) 69 Fawcett, N.C. ( 3 . 5 ) 4 2 ; ( 5 ) 223 Fayer, M.D. ( 1 ) 438; ( 4 ) 222 Federici, J. ( 1 ) 31 Feigel'man, V.M. ( 3 . 4 )

9 3 ; ( 3 . 6 ) 103

Fissi, A. ( 3 . 6 ) 1 2 , 13 Fisz, J.J. ( 1 ) 11 Fizeb, M. ( 4 ) 69 Flamigni, L. ( 1 ) 81 Flammersheim, H.J. ( 4 ) 4 1 , 71

Fleming, G.R. ( 1 ) 2 0 , 328; ( 3 . 3 ) 17

Fleming, S.A. ( 3 . 2 ) 2 0 ; (3.3) 60, 61; (3.6) 9

Fletcher, S.C. ( 2 . 2 ) 95 Fletcher, T.R. ( 2 . 2 ) 11 Flom, S.R. ( 1 ) 223, 231 232

Flores, J. ( 1 ) 54 Floret-David, D. ( 1 ) 462 Florio, E. ( 3 . 4 ) 8 8 , 89 Fojtik, A. ( 1 ) 240; ( 3 . 3 ) 26

Fok, N.V. ( 4 ) 51 Fokin, E.P. ( 3 . 2 ) 167 Folcher, G. ( 2 . 1 ) 221; ( 5 ) 135, 222

Fonken, G.J. ( 3 . 4 ) 138 Font, J. ( 5 ) 9 3 , 151 Fontanges, R. ( 5 ) 35 Foote, C.S. ( 1 ) 8 4 ; ( 3 . 5 ) 4 , 125

Forat, F.P. ( 5 ) 35 Ford, P.C. ( 2 . 1 ) 4 , 153, 159; ( 2 . 2 ) 122

Formenti, M. ( 2 . 1 ) 2 6 ; (5) 3

Formosinho, S.J. ( 1 ) 2 ,

Fessenden, R.W. ( 1 ) 487 296; ( 2 . 1 ) 216 Fessner, W.-D. ( 3 . 3 ) 112; Fornasiero, D. ( 1 ) 202, ( 3 . 4 ) 159

Fetizon, M. ( 3 . 1 ) 1 8 ; ( 3 . 2 ) 36

Fetterolf, M.L. ( 2 . 1 ) 83 Field, M. ( 1 ) 400 Fields, R.A. ( 2 . 1 ) 41 Fife, D.J. ( 2 . 2 ) 1 3 5 ; ( 3 . 3 ) 102; ( 5 ) 44

Figge, H. ( 3 . 7 ) 16 Findak, D.C. ( 3 . 6 ) 168 Findsen, E.W. (1) 367 Finey, P.A. ( 1 ) 74 Fink, J. ( 3 . 6 ) 21 Finter, J. ( 4 ) 359 Firl, J. ( 3 . 7 ) 140 Fischer, A.B. ( 1 ) 221 Fischer, E. ( 1 ) 228, 230 Fischer, G. ( 3 . 2 ) 104-

393

Forrester, J. ( 3 . 4 ) 30 Forster, L.S. ( 2 . 1 ) 42 Fouassier, J.P. ( 1 ) 461, 462; ( 4 ) 16

Foulger, B.E. ( 3 . 4 ) 30 Fournier, J. ( 1 ) 418 Foust, D.F. ( 2 . 2 ) 9 Fox, M.A. ( 2 . 1 ) 9 6 ; ( 2 . 2 ) 136;' ( 3 . 3 ) 63; ( 4 ) 81

Fozard, H.A. ( 1 ) 400 Francisco, C.G. ( 3 . 7 ) 187 Frank, A.J. ( 2 . 1 ) 179 Frank, C.W. ( 1 ) 266; ( 4 ) 247, 257, 262, 268

Frank, P. ( 4 ) 326 Frankel, E.N. ( 2 . 2 ) 28 Frankel, R.B. ( 2 . 2 ) 92 Frankowski, A. ( 3 . 6 ) 69 106, 113; ( 3 . 4 ) 160; Franz, L.H. ( 3 . 2 ) 159 ( 3 . 6 ) 105; ( 3 . 7 ) 25 Fratev, F. ( 1 ) 126 Fischer, J.W. ( 3 . 3 ) 109 Frauenrath, H. ( 3 . 3 ) 138 Fischer, R.T. ( 1 ) 320 Freas, R.B. ( 2 . 2 ) 10 Fischman, D.A. ( 1 ) 406 Fredrickson, G.H. ( 4 ) 268 Fisera, L. ( 3 . 6 ) 58 Fiser-Jakic, L. ( 3 . 4 ) 143 Freedman, K.A. ( 1 ) 224, 225, 233: ( 3 . 6 ) 3 Fisher, K. ( 3 . 4 ) 37

Author Index

5 64 Freeman, M.J. ( 2 . 2 ) 40 F r e e r , A.A. ( 3 . 6 ) 144 F r e e r , J. ( 4 ) 356 F r e i , B. ( 3 . 1 ) 35; ( 3 . 2 ) 56; ( 3 . 2 ) 57; ( 3 . 3 ) 70, 71, 133; ( 3 . 7 ) 133-135, 137 F r e i , H. (1) 77; ( 3 . 5 ) 58 F r e i l i c h , S.C. ( 1 ) 501 F r e i r e , R . ( 3 . 7 ) 186, 187 F r e i s e r , B.S. ( 2 . 2 ) 7 F r e i t a g , B.-J. ( 3 . 2 ) 103 F r e i t a g , R.A. ( 2 . 1 ) 9 7 , 98; ( 5 ) 9 6 F r e y e r , A.J. ( 3 . 2 ) 11, 111; (3.6) 85 Friedman, J.M. ( 1 ) 367 F r i e d r i c h , C. ( 4 ) 195 F r i n g s , R.B. ( 4 ) 147 F r i n k , M.E. ( 1 ) 470; ( 2 . 1 ) 153, 159 F r i p i a t , J. ( 2 . 1 ) 137; ( 5 ) 30, 117 F r i t z , H. ( 3 . 3 ) 106, 112, 113; ( 3 . 4 ) 159; ( 3 . 6 ) 1 7 , 100, 105 F r i t z , M.J. ( 3 . 7 ) 56 Frolow, F. ( 3 . 1 ) 1 1 Fryde, C.A. ( 4 ) 347 Fryzuk, M.D. ( 2 . 2 ) 121 Fu, S. ( 4 ) 382, 411 Fu, W.K. ( 2 . 2 ) 96 F u c a l o r o , A.F. ( 2 . 1 ) 42 F u e k i , K. ( 4 ) 303, 304 Fueno, T. ( 3 . 5 ) 6 5 F u j i e , H . ( 5 ) 94 F u j i h a r a , M. ( 2 . 1 ) 35 F u j i i , N. ( 4 ) 112 F u j i m o r i , T. ( 3 . 6 ) 106 Fujimoto, M. ( 2 . 1 ) 6 8 F u j i n a m i , M. ( 3 . 2 ) 31 F u j i o k a , T. ( 2 . 1 ) 21 F u j i t a , T. ( 4 ) 396; ( 5 ) 17 F u j i w a r a , M. ( 5 ) 118 F u j i w a r a , T. ( 5 ) 69 Fukaya, C. ( 3 . 2 ) 110 Fukishima, T. ( 4 ) 375 Fukuda, H. ( 4 ) 130, 157 Fukuda, Y. ( 1 ) 452 Fukumoto, K. ( 3 . 5 ) 127 Fukumoto, T. ( 2 . 3 ) 28; (3.6) 203 Fukumura, H. ( 1 ) 6 3 Fukunaga, T . ( 3 . 3 ) 130 Fukushima, M. (1) 457 Fukuzumi, S. ( 3 . 5 ) 112 Fu-Mian L i ( 4 ) 32 F u r a k o s h i , N . ( 3 . 6 ) 39 Furlong, D.N. ( 1 ) 297; ( 2 . 1 ) 114 Furue, M. ( 4 ) 233; (5)

Gasyna, Z. ( 2 . 1 ) 239 G a t e c h a i r , L.R. ( 4 ) 13 G a u g l i t z , G. (1) 244 Gautron, R. (1) 434 Gauvin, P. ( 4 ) 331 G a v r i l i n a , L.M. ( 4 ) 277 G a v r i l y u k , R.P. ( 4 ) 370 Gazel, A. ( 4 ) 305 Gaziev, S.A. ( 2 . 1 ) 219 G e b i c k i , J. ( 3 . 5 ) 1 6 Geenevasen, J.A.J. ( 3 . 2 ) 6 9 , 102 Gabe, E. ( 3 . 1 ) 39; ( 3 . 4 ) G e h r i s c h , R. ( 4 ) 120, 121 151; ( 3 . 5 ) 11 G e i g e r , D. ( 2 . 2 ) 6 5 , 134 G e i r s s o n , J. ( 3 . 5 ) 116 G a b r i e l , R. ( 3 . 5 ) 98 Gaceva-Bogreva, G. ( 4 ) Geisel, M. ( 3 . 7 ) 182 Genkin, V.N. ( 4 ) 325, 378 109 Gadd, G.E. ( 2 . 2 ) 14 Geoffroy, G.L. ( 2 . 2 ) 44; Gafney, H.D. ( 2 . 1 ) 122; ( 4 ) 48 George, C.A. ( 2 . 3 ) 24, ( 2 . 2 ) 42 25; ( 4 ) 158 Gahan, L.R. ( 2 . 1 ) 4 7 , George, M.V. ( 1 ) 487; 110; ( 5 ) 9 8 G a i r n s , R.S. (3.6) 166; ( 3 . 2 ) 6 3 , 124; (3.3) 135; (3.6) 54; ( 3 . 7 ) (3.7) 98, 99 G a l k i n , B.Ya. (2.1) 227 136 G a l l a g h e r , M . J . ( 3 . 3 ) 39; Georgieva, T. ( 4 ) 353 ( 3 . 7 ) 142 Geraghty, N.W.A. ( 3 . 2 ) 8 ; G a l l e g o , M.G. ( 3 . 2 ) 75, (3.4) 43 76; (3.4) 13; ( 3 . 6 ) 46 G e r a l d , R . (1) 175 G a l l h u b e r , E. ( 2 . 1 ) 81 Gerard, D. (1) 335, 358 G a l l i , C. (3.7) 157, 166; Gerasimenko, Yu.E. (3.2) ( 4 ) 166 168 Gerasimova, T.N. ( 3 . 5 ) G a l l u c c i , R.R. ( 3 . 7 ) 74 120 Gandhi, P. ( 3 . 5 ) 9 4 , 9 5 , 114 Gergely, J. ( 1 ) 363, 364 G a n d o l f i , M.T. ( 2 . 1 ) 103; G e r h a r t z , W. ( 2 . 2 ) 1 7 G e r l o c k , J.L. ( 4 ) 394, (5) 91 Ganjoo, A. ( 1 ) 467 395 G e r r a r d , D.L. ( 4 ) 186 G a n r i a , E.S. ( 4 ) 119 Ganz, A.M. (1) 281 G e r s d o r f , J. ( 3 . 1 ) 1 2 ; Ganzer, G.A. (3.7) 4 ( 3 . 4 ) 24 Gershuni, S. ( 2 . 1 ) 118; Gao, Z. ( 4 ) 106 Garacia Sahchez, F. ( 1 ) 166 Gethner, J.S. ( 2 . 2 ) 52 124 G e t o f f , N. ( 5 ) 22 Garbuz, N.I. ( 3 . 5 ) 117 Geue, R . J . ( 2 . 1 ) 110; ( 5 ) Garcia, B. (3.7) 116 Garcia, H. ( 3 . 4 ) 180 98 Gezalov, Kh.B. ( 4 ) 294 G a r c i a , J. ( 3 . 2 ) 49 Ghiggino, K.P. (1) 5 2 , Garcia, N.A. ( 1 ) 479 G a r d e t t e , J.L. ( 4 ) 346 53, 228, 237 Ghiron, D.A. ( 1 ) 168 G a r n e r , A . (3.2) 95 G a r r i d o , J. ( 4 ) 8 2 Ghosh, S. (1) 488; (3.2) G a r r i s o n , J . B . ( 4 ) 366 113; ( 3 . 3 ) 115, 122 Gasanov, R.G. ( 2 . 2 ) 61 Ghosh, T. (3.3) 104 Giamello, E. (5) 168 Gasanova, L.V. (3.5) 31; 32 G i a n n o t t i , C. (1) 220; Gasdaska, J . R . ( 3 . 7 ) 40 (2.1) 221; (3.5) 118; Gasking, D . I . ( 2 . 3 ) 1 4 ( 5 ) 70 Gassman, P.G. (3.3) 132; Giasson, R . (3.5) 10; ( 3 . 6 ) 210 ( 3 . 6 ) 72 Gaston-Bonhomme, Y. ( 5 ) Gibson, D.H. (2.2) 32 Giesse, R. ( 4 ) 114, 313 20

152 F u r u s a k i , A. ( 3 . 2 ) 4 0 , 42 F u r u t a , H. (3.4) 80 F u r u t a , T. ( 3 . 2 ) 81, 8 2 , 85 Furuya, Y. ( 3 . 4 ) 81; ( 3 . 6 ) 10 F u s i , S. ( 3 . 2 ) 39; (3.6) 88, 125 F u s s , A. ( 3 . 7 ) 36

Author Index G i l , M.H. ( 4 ) 111 G i l b e r t , A. ( 3 . 4 ) 2 1 , 2 2 , 3 0 , 4 5 , 5 3 , 68 G i l b e r t , B.C. ( 3 . 7 ) 48 G i l l , S. ( 3 . 5 ) 43 G i l l , U.S. ( 2 . 2 ) 86 G i l l b r o , T. ( 1 ) 214, 242; ( 3 . 3 ) 1 6 ; ( 4 ) 438 G i l p i n , R.W. ( 5 ) 34 G i l y a n o v s k i i , P.V. ( 2 . 1 ) 188 Gimenez, M. ( 5 ) 21 G i n i g e r , R. ( 1 ) 117 Ginsberg, A. ( 1 ) 360 Ginsburg, A.P. ( 2 . 1 ) 165 Ginsburg, D. ( 3 . 3 ) 111 Ginsburg, H. ( 3 . 7 ) 1 6 8 , 169 G i o r g e t t i , A. ( 2 . 1 ) 1 9 6 , 197 G i r i , B.P. ( 3 . 1 ) 3 9 , 4 0 , 47; ( 3 . 4 ) 150, 151; ( 3 . 5 ) 11 Gismondi, T.E. ( 2 . 2 ) 5 4 ; ( 4 ) 374 Gitzel, J. ( 2 . 1 ) 2 3 3 ; ( 5 ) 66 G i u f f r i d a , S. ( 2 . 1 ) 7 0 Glasser, N. ( 1 ) 167 Gleiter, R. ( 1 ) 93 G l e i x n e r , G. ( 4 ) 67 Glenneberg, J. ( 3 . 2 ) 103 G l e n t o , G. ( 1 ) 497 Gleria, M. ( 4 ) 355 Gliemann, G. ( 2 . 1 ) 1 7 6 ; ( 2 . 2 ) 41 G l i e s i n g , S. ( 3 . 3 ) 7 9 G l i n c h i k o v , S.V. ( 5 ) 114 Glinski, R.J. (2.3) 7 Glock, V. ( 3 . 7 ) 16 G l o v e r , S.A. ( 3 . 5 ) 1 0 0 ; ( 3 . 7 ) 100 G l o v e r , S.G. ( 2 . 1 ) 42 Gnanaguru, K. ( 3 . 2 ) 4 3 , 45 Goan, K. ( 3 . 3 ) 8 Godburt, E. ( 4 ) 216 Goedeweeck, R. ( 1 ) 330, 346 Goedken, V.L. ( 2 . 2 ) 1 3 9 ; ( 3 . 4 ) 51 G o e l l e r , G. ( 1 ) 210 C o r n e r , H. ( 1 ) 238, 240, 4 4 3 ; ( 2 . 1 ) 242, 243; ( 3 . 3 ) 1 5 , 25-27; ( 5 ) 72, 73 G o e t z b e r g e r , A. (5) 238 G o z l e r , B. ( 3 . 6 ) 8 4 Gohre, K. ( 3 . 5 ) 55 Gold, J.S. ( 2 . 1 ) 82 Goldener, U. ( 3 . 3 ) 7 0 , 7 1 ; ( 3 . 7 ) 134

565 G o l ' d f a r b , E.I. ( 3 . 7 ) 1 Golding, S.L. ( 3 . 7 ) 100 Goldman, A.S. ( 2 . 2 ) 4 7 , 100, 101 Gole, J.L. ( 2 . 3 ) 7 Golikov, I.V. ( 4 ) 156 G o l l n i c k , K. ( 1 ) 481; ( 3 . 5 ) 102 Golombek, M. ( 1 ) 7 9 Golovanov, S.P. ( 2 . 1 ) 136 Golovina, A.P. ( 2 . 1 ) 136 Gomes, A.G.L. ( 1 ) 212 Gomez, P.M. ( 4 ) 411 Gomez-Fernandez, J.C. ( 1 ) 369 Gondo, Y. ( 1 ) 440 Gong, B. ( 4 ) 131 Gonzalez, L.A. ( 4 ) 320 Gonzalez, R. ( 3 . 4 ) 46 Gonzalez-Elipe, A.R. ( 5 ) 166 Gooden, R. ( 4 ) 352 Goodin, J.W. ( 3 . 3 ) 141 Goodman, J.L. ( 1 ) 152 Goodwin, D. ( 1 ) 4 7 5 ; ( 3 . 5 ) 105 Goodwin, J.W. ( 3 . 7 ) 155 Goodwin, K.V. ( 2 . 1 ) 11 G o o i j e r , C. ( 1 ) 116 Goosen, A. ( 3 . 5 ) 1 0 0 ; ( 3 . 7 ) 100 Gopidas, K.R. ( 1 ) 4 8 7 ; (3.2) 63 Gorman, A.A. ( 1 ) 4 2 0 , 474; ( 3 . 5 ) 6 0 Gornostaev, L.M. ( 3 . 7 ) 93 Gorodetsky, G. ( 4 ) 365 Gorodova, L.V. ( 5 ) 107 Gorovkov, A.T. ( 4 ) 369 Gorsane, M. ( 3 . 4 ) 1 1 4 , 115 Gorshkov, N.G. ( 2 . 1 ) 219 Gosh, P. ( 4 ) 92 Goswami, P.C. ( 3 . 1 ) 32 G o t t h a r d t , H. ( 3 . 2 ) 1 1 2 ; ( 3 . 6 ) 19 G o t t s c h a l k , P. ( 1 ) 478 Gould, I . R . ( 1 ) 1 4 3 , 289, 304, 4 6 4 , 4 9 2 ; ( 3 . 1 ) 7 ; ( 3 . 7 ) 4 0 , 52 Goursot, A. ( 2 . 1 ) 180 Goyal, I . C . ( 1 ) 379 G o z l e r , B. ( 3 . 2 ) 109 Grabarek, Z. ( 1 ) 364 Grabielle-Madelmont, C . ( 1 ) 399 Grabowski, Z.B. ( 1 ) 435 G r a e t z e l , C.K. ( 3 . 5 ) 137 Graetzel, M. ( 2 . 1 ) 2 2 , 100; ( 3 . 5 ) 1 3 7 ; ; ( 5 ) 119, 186. 1 8 7 , 194. 206; 2 1 1 ; 2 2 4 -

Graham, D.J. ( 1 ) 450 G r a i f e r , A.Yu. ( 5 ) 200 Gramain, J.C. ( 3 . 5 ) 141 Granchak, V.M. ( 4 ) 153 Grancludon, P. ( 3 . 6 ) 35 Granger, R. ( 2 . 2 ) 34 Granozzi, G. ( 2 . 2 ) 8 0 , 8 1 Granshak, V.M. ( 4 ) 9 1 G r a n t , E.R. ( 2 . 2 ) 8 8 G r a n t , H.G. ( 3 . 5 ) 9 2 G r a n t , R.D. ( 3 . 5 ) 18 Grasse, P.B. ( 3 . 7 ) 44 G r a t t i n i , F. ( 4 ) 3 1 4 , 393 G r a t t o n , E. ( 1 ) 2 4 , 3 8 , 3 9 , 260 G r a v e l , D. ( 3 . 5 ) 1 0 ; ( 3 . 6 ) 7 2 , 73 Gray, A.B. ( 3 . 2 ) 10 Gray, H.B. ( 2 . 1 ) 149 Gray, T.H. ( 1 ) 203 Grayson, D.H. ( 3 . 2 ) 33 Grayson, M.A. ( 4 ) 351 Grebenik, P. ( 2 . 2 ) 8 Green, J.C. ( 2 . 2 ) 48 Green, K.E. ( 3 . 3 ) 110 Green, M. ( 2 . 2 ) 4 0 ; ( 5 ) 214 Green, M.L.H. ( 2 . 2 ) 48 Green, P.N. ( 4 ) 8 3 , 8 4 Green, W.A. ( 4 ) 8 3 , 8 4 Greenberg, D.B. ( 5 ) 42 Greene, B . I . ( 1 ) 1 5 3 , 2 1 9 , 236; ( 3 . 3 ) 24 G r e g o i r e , F. ( 5 ) 21 Gregory, M.F. ( 2 . 2 ) 98 Grellmann, K.-H. (3.1) 5 3 ; ( 3 . 6 ) 3 8 , 42 G r e s a l f i . N.J ( 2 . 2 ) 19 Gretz, J: ( 5 ) 16 G r e v e l s , F.W. ( 2 . 2 ) 1 5 , 1 7 , 73 Griesser, F. 1 ) 273 G r i f f i n , G.L. ( 2 . 1 ) 2 7 ; ( 5 ) 191 G r i f f i n , G.W. ( 3 . 3 ) 1 3 6 ; ( 3 . 5 ) 78 G r i f f i n g , B.F. ( 4 ) 326 G r i g o r e v a , G.L. ( 4 ) 286 G r i g o r o v , I . ( 1 ) 323 G r i l l e r , D. ( 3 . 7 ) 4 8 , 49 Grime. W. ( 3 . 3 ) 139 Grimshaw, J. ( 3 . 4 ) 143 G r i s k i n a , A.D. ( 4 ) 173 G r i t s a n , N.P. ( 2 . 1 ) 1 9 1 ; ( 3 . 2 ) 167 Grosch, W. ( 3 . 7 ) 140 Grossman, N. ( 4 ) 443 Gruen, H. ( 3 . 3 ) 27 Grutzmacher, H.-F. ( 3 . 6 ) 160 Grummt, U.-W. (3.5) 99; (3.6j 5, 6 , 8

566 Grund, C. ( 3 . 3 ) 112; ( 3 . 4 ) 159 G r u t s c h , P . A . ( 2 . 2 ) 129 Gryczynski, I. ( 1 ) 348, 350, 384, 456 Grzonka, Z. ( 1 ) 350 Gu, B. ( 5 ) 186 Guard-Friar, D. ( 1 ) 261 G u a r r , T. ( 5 ) 160 Gudgin Templeton, E.F. ( 1 ) 123 Gudzera, S.S. ( 4 ) 6 8 , 75 Guedel, H.U. (2.1) 51 Guenther, U. ( 3 . 3 ) 51 Guenzburger, D.J.R. (2.2) 69 Guerry-Butty, E. ( 1 ) 91 Guesten, H. ( 1 ) 194, 195 Gugliemo, G. ( 2 . 2 ) 126 Gugumus, F.L. ( 4 ) 389 G u i g l i a n o , R.P. ( 1 ) 128; ( 3 . 6 ) 67 G u i l l e t , J.E. (3.4) 152; (3.5) 17; ( 4 ) 1 6 7 , 179; 226, 251, 299, 354 Guinand, G. (3.4) 1 7 3 Guinaudeau, H. ( 3 . 2 ) 109; (3.6) 84 G u l o t t y , R . J . ( 1 ) 20 Gulyakevich, O.V. ( 3 . 5 ) 117 Gunstone, F.D. ( 3 . 5 ) 74 Guo, L.W. ( 2 . 2 ) 6 3 Gupta, A . ( 4 ) 382, 411 Gupta, B.P. ( 1 ) 379 Gustav, K. (3.6) 4 Gut, I. ( 3 . 2 ) 129 G u t h r i e , J.T. ( 4 ) 111, 124, 125 Guyon, C. ( 3 . 4 ) 1 2

H a l e v i , E . A . ( 3 . 3 ) 89 Hall, D.O. ( 5 ) 187 Haller, K . J . ( 2 . 2 ) 94 H a l t o n , B. ( 3 . 7 ) 30 Halverson, A.M. ( 3 . 4 ) 6 4 ; ( 3 . 6 ) 74 Hamada, T. (3.6) 154 Hamada, Y. ( 2 . 3 ) 22 Hamaguchi, H. ( 1 ) 439 Hamanoue, K. ( 1 ) 189, 190; ( 3 . 4 ) 83 Hamazaki, H. ( 3 . 6 ) 146 Hamblett, I. ( 1 ) 420 Hambley, T.W. ( 3 . 5 ) 83 Hambright, P . ( 2 . 1 ) 160 Hamer, N.K. ( 3 . 2 ) 118 Hamidi, A . ( 4 ) 405 Hamiotis, Z. ( 4 ) 359 Han, P. ( 4 ) 8 6 Hanaoka, M. (3.5) 140; ( 3 . 6 ) 33, 156 Hancock, L.E. (1) 261 Handa, T. (3.5) 136 Haneda, T. ( 3 . 6 ) 20 Hanfland, M. ( 1 ) 112 Hanly, N.M. ( 3 . 2 ) 8; (3.4) 43 Hannaby, M. ( 3 . 3 ) 2 Hannak, D. ( 1 ) 225 Hannemann, K. ( 3 . 7 ) 13, 1 4 , 24 Hansen, C.M. ( 4 ) 36 Hansen, H.-J. (3.3) 8 6 ; ( 3 . 6 ) 101 Hansen, J . B . ( 3 . 2 ) 101 Hansen, L. ( 1 ) 110 H a n z l i k , C . A . ( 1 ) 261 Har, G. ( 4 ) 398 Harada, H. ( 2 . 1 ) 24; ( 5 ) 1 7 1 , 173, 174, 185 H a r a s h i n a , H. ( 3 . 2 ) 13 Hardy, C. ( 3 . 4 ) 125 Haas, E. ( 1 ) 362, 374 Hargreaves, J . S . ( 4 ) 258 Haas, 0. ( 5 ) 228 Harle, I . L . ( 3 . 2 ) 140 Haber, H. ( 3 . 1 ) 42; ( 3 . 6 ) H a r r i g a n , L. ( 1 ) 8 4 76 Harriman, A . ( 1 ) 218 Haber-Patz, U. ( 3 . 3 ) 76 ( 2 . 1 ) 9 , 102, 160, 240, Hace, D. ( 4 ) 335 247; (5) 63, 113, 115, Hada, H . ( 5 ) 198, 199 120, 127 Hadel, L . M . ( 3 . 7 ) 54 Harris, C.B. ( 1 ) 204 Haga, M. ( 2 . 1 ) 131 Harris, R . A . ( 1 ) 401 Hagaman, K . A . (1) 340 Harris, R.L. ( 2 . 1 ) 165 Hageman, H . J . ( 4 ) 77 H a r r i s o n , M.J. ( 4 ) 182 H a r r i s o n , W.D. ( 2 . 1 ) 196 Hagiwara, H. ( 1 ) 457; ( 3 . 3 ) 114 Harrop, R . ( 4 ) 229 Hagiwara, S. (3.3) 6 8 , 69 H a r r o w f i e l d , J.M. ( 2 . 1 ) 47 Hagiwara, T. ( 4 ) 151 Hahn, L . R . ( 3 . 1 ) 31 Hart, D.E. ( 1 ) 258 H a i m , A . (2.1) 9 5 , 108 H a r t a n , H.-G. (3.2) 159 H a i n d l , E. (2.1) 41 H a r t l e y , R . J . ( 1 ) 186 Hakushi, T. ( 3 . 3 ) 8, 6 8 , Hartmann, M. ( 4 ) 108 69 Hartmann, W. ( 3 . 6 ) 178

Author Index Harwood, L.M. (3.2) 10, 34 Hasegawa, M. ( 3 . 2 ) 13 Hasegawa, T. (3.1) 41; ( 3 . 2 ) 121, 122; (3.3) 21; (3.6) 75; ( 5 ) 216 Haselbach, E . ( 1 ) 1 7 3 Hashem, M.M. ( 4 ) 127 H a s h i , T. ( 1 ) 452 Hashida, T. (2.2) 29 Hashimoto, S. ( 1 ) 274, 298, 307; ( 3 . 4 ) 186; (3.5) 71; (3.7) 131 Hashimoto, T. ( 4 ) 1 7 4 , 209; ( 5 ) 159 Hashimoto, Y. (1) 388 Hassan, M.E. (3.7) 153, 154 Hasselbach, H.-J. (3.7) 126 Hassinen, E. (3.7) 102 Hata, N. ( 3 . 6 ) 5 9 Hata, Y. ( 1 ) 83 Hatakeyama, Y. ( 2 . 1 ) 147 Hatanaka, Y. (3.2) 135, 140, 142; ( 3 . 6 ) 81, 83, 126 H a t s u i , T. ( 3 . 2 ) 15; ( 3 . 5 ) 75 Haubs, M. ( 3 . 6 ) 70 H a u e n s t e i n , B.L. ( 1 ) 34 Hauge, R.H. (2.2) 8 2 Haupt, J . ( 2 . 1 ) 77 Hauqing, W. ( 3 . 6 ) 64 Hauser, M. (1) 349 Havranek, A . ( 4 ) 289 Hawecker, J. (2.1) 124 Hawkins, M. ( 2 . 3 ) 37, 38, 51 H a w s , E.J. ( 3 . 2 ) 141 Hay, B.A. (3.3) 132; ( 3 . 6 ) 210 Hayakawa, K. (3.2) 132; (5) 53 Hayase, S. ( 4 ) 10 Hayashi, H. ( 2 . 1 ) 198; ( 2 . 3 ) 55 Hayashi, K. (4) 19 Hayashi, S. ( 4 ) 37, 126 Hayenes, R.K. ( 3 . 5 ) 83 Hayes, W. ( 4 ) 190 He, H. ( 3 . 5 ) 57 He, X. ( 4 ) 86, 95 He, Y. ( 4 ) 89 Hebeish, A . ( 4 ) 436 Heckel, A . (3.6) 192, 193 Hedstrom, J.F. ( 1 ) 258 Heelis, P.F. (3.5) 40, 130 Hegedus, L.S. ( 2 . 2 ) 25 H e i c k l e n , J. (3.5) 145, 146; ( 3 . 6 ) 141

567

Author Index Heimgartner, H. ( 3 . 2 ) 6 8 ; ( 3 . 4 ) 182

Heisel, F. ( 1 ) 1 5 7 , 158 Heitele, H. ( 5 ) 133 Heldal, J.A. ( 2 . 2 ) 28 Heldt, J. ( 1 ) 107 Heller, H.G. ( 3 . 2 ) 126; ( 3 . 4 ) 141

Hellman, M.Y. ( 4 ) 352 Helman, W.P. ( 1 ) 31 Helwic, N. ( 2 . 1 ) 44 Hemmila, I. ( 1 ) 69 Hemmingsen, T.H. ( 3 . 7 ) 138

Henderson, D. ( 3 . 1 ) 16 Henderson, L.J. ( 2 . 1 ) 85 Hendrich, M.P. ( 3 . 7 ) 44 Henglein, A. ( 2 . 1 ) 1 8 ; ( 5 ) 170

Henin, F. ( 3 . 1 ) 4 3 ; ( 3 . 2 ) 62

Henlin, J.-M. ( 3 . 7 ) 141 Henman, T.J. ( 4 ) 295, 384 Henne, A. ( 3 . 6 ) 213, 214 Henner, A. ( 4 ) 46 Hennig, H. ( 2 . 1 ) 7 2 ; ( 2 . 2 ) 3 1 , 33

Henning, H.G. ( 3 . 1 ) 4 2 ; ( 3 . 6 ) 76

Henre, A. ( 1 ) 427 Hensler, G. ( 2 . 1 ) 8 1 Heppener, M. ( 5 ) 134 Herbert, D . J . ( 3 . 2 ) 22 Hermanies, E. ( 4 ) 154 Hermann, H. ( 2 . 2 ) 1 5 , 7 3 Hernandez, R. ( 3 . 7 ) 187 Hernandez, S. ( 2 . 2 ) 85 Heropoulos, A. ( 1 ) 341 Herreman, W. (1) 48 Herrmann, J.M. ( 5 ) 175 Hertl, W. ( 5 ) 225, 226 Herve', Y. ( 3 . 7 ) 117 Hervet, H. ( 4 ) 228 Herz, W. ( 3 . 5 ) 81 Hesabi, M.M. ( 3 . 7 ) 120 Hesse, K. ( 3 . 3 ) 119 Hessler, D. ( 2 . 1 ) 132 Hetrick, R.E. ( 5 ) 231 Hettich, R . L . ( 2 . 2 ) 7 Heuffer, J. ( 3 . 6 ) 153 Heyward, I.P. ( 4 ) 142 Hibbard, L.B. ( 1 ) 332 Hidaka, H. ( 5 ) 171 Higgins, B.E. ( 2 . 2 ) 60 Highland, R.G. ( 1 ) 4 6 6 ; ( 2 . 1 ) 229

Higuchi, H. ( 3 . 4 ) 158 Higuchi, T. ( 2 . 2 ) 2 9 ; ( 2 . 3 ) 26; ( 3 . 4 ) 157; ( 3 . 6 ) 200 Hikada, T. ( 1 ) 1 4 2 , 442 Hikasa, M. ( 3 . 4 ) 8 2 ;

( 3 . 6 ) 134

Hilary, J.L. ( 4 ) 195 Hild, E.K. ( 1 ) 359 Hild, G. ( 4 ) 237 Hildenbrand, K. ( 3 . 3 ) 43 Hilgers, G. ( 3 . 1 ) 2 2 , 33 Hilinski, E.F. ( 1 ) 172 Hill, C.L. ( 5 ) 111, 112 Hill, D.J.T. ( 4 ) 361 Hill, J. ( 3 . 7 ) 120 Hill, K. ( 3 . 2 ) 8 6 ; ( 3 . 7 ) 1 8 , 19

Hill, R.R. ( 3 . 7 ) 111 Hiller, W. ( 2 . 2 ) 24 Hine, K. ( 4 ) 198 Hinsken, W. ( 3 . 2 ) 89 Hinzmann, G. ( 3 . 5 ) 99 Hirai, H. ( 3 . 5 ) 4 9 ; ( 5 ) 101, 102

Hiraki, K. ( 2 . 2 ) 104 Hiramatsu, M. ( 1 ) 1 9 1 ; ( 3 . 4 ) 6 3 , 1 7 8 ; ( 3 . 5 ) 23

Hirao, K. ( 1 ) 211 Hirase, S. ( 3 . 4 ) 8 3 Hiratsuka, H. ( 1 ) 142 Hirayanagi, K. ( 4 ) 236 Hirokami, S . ( 3 . 2 ) 9 2 ; ( 3 . 6 ) 18

Hirota, K. ( 3 . 6 ) 62 Hirota, M. ( 4 ) 449 Hirota, N. ( 1 ) 1 2 2 , 441 Hirotsu, K. ( 2 . 2 ) 29; ( 2 . 3 ) 2 6 ; ( 3 . 4 ) 157; ( 3 . 6 ) 200 Hitchcock, P.B. ( 3 . 6 ) 169 Ho, C.N. ( 1 ) 62 Ho, P.P. ( 1 ) 32 Ho, T.F. ( 5 ) 1 2 6 , 132 Ho, T.I. ( 3 . 6 ) 133 Hobert, K. ( 3 . 7 ) 75 Hochstrasser, R.M. ( 1 ) 235, 236; ( 3 . 3 ) 24 Hoegberg, H.E. ( 3 . 5 ) 79 Hoel, E.L. ( 2 . 2 ) 93 Hoenes, G. ( 1 ) 349 Hoerhold, H.H. ( 4 ) 41 Hoffman,,M.Z. ( 2 . 1 ) 9 4 , 1 3 2 ; ( 5 ) 8 5 , 8 6 , 92 Hoffmann, M.R. ( 5 ) 195 Hoffmeyer, H. ( 2 . 3 ) 8 Hofmann, M. ( 2 . 3 ) 2 Hofstraat, J.W. ( 1 ) 116 Hofzumahaus, A . ( 2 . 3 ) 31 Hoganson, C.W. ( 1 ) 205 Hogea, I. ( 4 ) 345 Hogiguchi, R. ( 1 ) 105 Holden, D.A. ( 4 ) 264 Hollebone, B.R. ( 2 . 1 ) 140 Holler, J.F. ( 2 . 1 ) 8 8 ; ( 5 ) 56 Hollingsworth, W.E. ( 2 . 2 ) , l

L

Holroyd, R.A. (1) 82 Holt, E.M. ( 2 . 2 ) 96 Holton, G.R. ( 1 ) 235 Holzwarth, A.R. ( 1 ) 453 Honda, H. ( 3 . 3 ) 44 Honda, K. ( 2 . 3 ) 20 Honda, Y. ( 2 . 1 ) 189 Hong, A.P. ( 5 ) 195 Hong, S. ( 4 ) 149 Honi, K. ( 4 ) 214 Hontzopoulos, E. ( 2 . 1 ) 170; ( 5 ) 76

Hooker, R.H. ( 2 . 2 ) 7 0 Hoornweg, G.P. ( 1 ) 116 Hopf, H. ( 1 ) 432, 4 3 3 ; ( 3 . 4 ) 108

Hopfield, J.J. ( 5 ) 131 Hopkins, J.B. ( 1 ) 1 4 , 9 8 , 99

Horak, M. ( 2 . 3 ) 45 Horie, K. ( 1 ) 9 6 , 211, 270; ( 4 ) 1 7 5 , 236

Horie, 0. ( 2 . 3 ) 8 Horiuchi, T. ( 2 . 2 ) 29 Horner, M.G. ( 3 . 3 ) 1 0 7 ; ( 3 . 4 ) 44

Horowitz, A. ( 3 . 5 ) 90 Horowitz, P.M. ( 1 ) 345, 354

Horrocks, W.D. ( 1 ) 359 Horspool, W.M. ( 3 . 1 ) 3 ; ( 3 . 2 ) 75-78; ( 3 . 3 ) 4 1 , 42, 72; (3.4) 13; (3.6) 2 7 , 46-48, 79 Horvath, 0 . ( 2 . 1 ) 1 8 7 , 190; ( 5 ) 31 Hoser, H. ( 1 ) 210 Hoshi, B. ( 3 . 2 ) 80 Hoshi, N. ( 3 . 3 ) 114 Hoshino, M. ( 2 . 1 ) 1 3 8 ; ( 2 . 2 ) 5 9 , 113, 1 1 5 , 116, 139 Hoshino, 0 . ( 3 . 4 ) 1 4 7 ; ( 3 . 7 ) 143 Hosoda, M. ( 4 ) 242 Hosoda, Y. ( 2 . 3 ) 6 ; ( 3 . 6 ) 218 Hosseini, M.W. ( 2 . 1 ) 150 Hou, H. ( 2 . 1 ) 225 Houben, J.L. ( 3 . 6 ) 1 2 ; ( 4 ) 213 Houlding, V.H. ( 2 . 1 ) 179 Hoyle, C.E. ( 4 ) 150 Hrllovic, P. ( 4 ) 354 Hruska, F.E. ( 3 . 2 ) 9 9 ; ( 3 . 6 ) 87 Hsu, W.L. ( 2 . 2 ) 32 Hu, C. ( 4 ) 54 Hu, J. ( 2 . 1 ) 220 Hu, Q. ( 3 . 3 ) 4 8 ; ( 3 . 6 ) 49 Hu, X. ( 4 ) 399 Huang, B. ( 4 ) 54

568 Huang, D. ( 1 ) 203 Huang, S. ( 2 . 3 ) 47 Huang, W. ( 4 ) 54 Huang, X. ( 3 . 3 ) 48; (3.6) 49 Huang, Y. ( 4 ) 223 Huber, D.M. ( 1 ) 409 Huber, J . R . ( 2 . 3 ) 33 Huber, W. ( 3 . 5 ) 144 Hubesch, B. ( 2 . 1 ) 158; (5) 74, 104 Hubig, S. ( 1 ) 244 Hubmann, B. ( 4 ) 189 Hucker, J. ( 1 ) 433 Hudson, A. ( 3 . 2 ) 158 Huelskaemper, L. ( 3 . 1 ) 51 Hunig, S. (3.3) 119; ( 3 . 6 ) 118 Hug, D.H. ( 1 ) 343, 495 Hug, G.L. ( 1 ) 31, 487 Hui, Y. (3.3) 22 Huizer, B.H. ( 1 ) 88, 109, 179 H u l t , A. ( 4 ) 38, 98 Humphrey-Baker, R . ( 1 ) 217 Hunter, E.P.L. ( 1 ) 18 Hunton, D.E. ( 2 . 3 ) 2 Huppert, D. ( 1 ) 120, 138 Hurley, J . ( 5 ) 34 H u r t u b i s e , R . J . (1) 426 Husain, A . (1) 351 Hush, N.S. ( 5 ) 134 Hussmann, G.P. ( 3 . 4 ) 7 ; (3.6) 55 Huston, A.L. ( 1 ) 6 4 , 65 Hutchinson, J . A . (1) 233 H u t z i n g e r , 0. ( 3 . 4 ) 87 Hwang, K.K.S. ( 4 ) 137 Hyla-Kryspin, I. ( 2 . 2 ) 103 Hynes, J.T. (1) 7 I b a r z , A . ( 3 . 6 ) 148 I b o r r a , S. (3.4) 180 Ibrahim, M. ( 4 ) 434 I c h i n o s e , N. (3.3) 126; (3.5) 103, 106; ( 5 ) 47 I d e , H. ( 3 . 5 ) 44 I d e , J.P. ( 1 ) 280 I g a , R. ( 4 ) 219 I g a r i s h i , T. ( 1 ) 511 I h , K.J. ( 4 ) 6 1 Ihama, M . ( 2 . 1 ) 126 I h a r a , M. ( 3 . 5 ) 127 I'Haya, Y.J. ( 1 ) 460 I i t a k a , Y. ( 3 . 1 ) 48 I i z a w a , T. ( 4 ) 146, 148 I i z u k a , H. (3.6) 165 I k a , K . V . ( 4 ) 417 I k e d a , K. ( 4 ) 112

Author Index I k e d a , M . (2.3) 1 0 ; (3.4) I t a g a k i , H. ( 1 ) 96 74, 75; (3.6) 96, 209 I t a y a , A. (5) 165 I t o , K. (2.2) 29 I k e d a , Y. (3.5) 65 Ikekawa, N. ( 3 . 7 ) 67 I t o , S. ( 1 ) 263; ( 3 . 7 ) Ikemoto, I. (5) 203 125 Ikemoto, N. (1) 376 I t o , T. ( 2 . 2 ) 139; (5) Ikeyama, T. ( 1 ) 429 203 Ikezawa, H. (3.3) 103; I t o , Y. (1) 239; ( 3 . 1 ) 47; ( 3 . 3 ) 29; ( 3 . 4 ) 150 ( 5 ) 48 I k e z u , S. ( 3 . 3 ) 118 I t o h , H. ( 3 . 4 ) 100; ( 3 . 6 ) I l g e , H.D. ( 3 . 2 ) 125; 130 I t o h , K. (3.4) 81; (3.6) ( 3 . 3 ) 79 I l i c h , P. ( 1 ) 324 10; ( 3 . 7 ) 64, 183 I l l i s k o v i c , N. ( 4 ) 341 I t o h , M . ( 1 ) 135, 141, Imaeda, K. ( 4 ) 281 388; (3.2) 40; ( 3 . 5 ) 2 3 Imamura, T. ( 2 . 1 ) 68 Itokawa, H. ( 3 . 1 ) 4 8 I m a n i s h i , Y. ( 4 ) 256 Ivanov, V.F. ( 5 ) 158, Imhof, R.E. ( 1 ) 27, 55 324, 430 I n a g a k i , S. ( 3 . 7 ) 10 Ivanova, L.V. ( 2 . 2 ) 6 1 Inamoto, N. ( 2 . 2 ) 29 I v e s , J.L. ( 3 . 5 ) 96 Iwabuchi, S. ( 3 . 5 ) 25 I n d e l l i , M . T . ( 2 . 1 ) 92 I n g o l d , K.U. ( 3 . 1 ) 24; Iwahama, K. ( 4 ) 189 I w a h a s h i , M. ( 1 ) 401 (3.4) 129 Inou, Y. (5) 197 Iwai, J. (2.2) 49, 50, 59 Inoue, H. ( 2 . 1 ) 248; Iwai, K . ( 4 ) 72, 233 Iwamoto, H. ( 3 . 2 ) 161, ( 3 . 4 ) 184, 185 ( 3 . 6 ) 44, 149 162 Inoue, M. ( 3 . 4 ) 136; Iwamoto, M. ( 3 . 6 ) 15 ( 3 . 6 ) 34 Iwamura, H. ( 2 . 1 ) 21; Inoue, T. ( 4 ) 245 ( 3 . 7 ) 6 4 , 92 I n o u e , Y. (3.3) 8 , 6 8 , 69 Iwasa, K. (3.6) 6 8 Inouye, Y. ( 3 . 2 ) 9 I w a s a k i , H. ( 3 . 7 ) 6 5 I o g a n s e n , A . A . (2.3) 35, I w a s a k i , K . (3.5) 1 2 3 36 I w a s a k i , N. ( 1 ) 105 I o n i n , B.I. ( 3 . 6 ) 215 Iwase, K. (3.7) 10 Ionov, S . I . ( 2 . 3 ) 46 Iwata, K. ( 4 ) 151 I q b a l , M. (2.2) 86 Iwayanagi, T. ( 4 ) 221 I q b a l , R. ( 2 . 3 ) 39 Iweibo, I. (1) 165 I r i e , M. ( 4 ) 209, 219, Iyoda, J. ( 4 ) 152 221, 242; (5) 159 I y o d a , M. ( 3 . 2 ) 29-31 I r i e , T. ( 3 . 3 ) 47; ( 3 . 6 ) Izawa, Y. (3.5) 123; 50 ( 3 . 7 ) 10, 39, 53, 60 I r n g a r t n e r , H. ( 3 . 3 ) 74, Izumridov, V . A . ( 4 ) 204 76 I r v i n e , M. ( 1 ) 420 I s a k o v , I . V . ( 4 ) 56 J a a r i n e n , S. (3.7) 176 I s e n o r , N.R. ( 2 . 3 ) 3 Jackson, W.R. (1) 216 I s h i b a s h i , I. (3.6) 96 J a c o b i , M. ( 4 ) 46 I s h i d a , A . ( 2 . 1 ) 201; J a c o b s , H.J.C. (3.3) 56; ( 3 . 3 ) 36; ( 3 . 6 ) 129 ( 3 . 7 ) 79 I s h i d a , H. ( 4 ) 1 2 3 J a c o b s , P.A. ( 2 . 2 ) 6 8 I s h i i , K. ( 3 . 3 ) 134; J a c o b s s o n , U. ( 3 . 3 ) 84; ( 3 . 4 ) 8 2 ; ( 3 . 6 ) 134; ( 3 . 4 ) 10 ( 3 . 7 ) 132 J a c q u e s , P. ( 1 ) 461, 462 Ishikawa, M. ( 2 . 3 ) 26; J a e g e r , W. ( 4 ) 208 ( 3 . 4 ) 157; ( 3 . 6 ) 197, J a f f r e z i c , N . ( 5 ) 175 200 J a g g i , D. ( 3 . 5 ) 92 Ishikawa, Y. ( 3 . 2 ) 121 J a h n , R. ( 3 . 3 ) 76 I s h i t a n i , 0. ( 2 . 1 ) 126 J a i n , S. ( 3 . 5 ) 114 I s h i z a k a , S. ( 1 ) 139 J a k o p c i c , J. (3.4) 1 4 3 I s k a h o r , N . I . ( 4 ) 94 Jakoubkova, M . ( 2 . 3 ) 45 I s o b e , K. ( 2 . 2 ) 39 James, D.R. ( 1 ) 49-51,

Author Zndex 3 2 5 , 3 2 9 , 339

Jameson, D.M. ( 1 ) 2 4 , 39 Janic, I. ( 1 ) 209 Janovia, Z. ( 4 ) 412 Jans, A.W.H. ( 3 . 4 ) 34 Janzen, E.G. ( 2 . 1 ) 245 Jaque, F. ( 5 ) 2 3 5 , 236 Jardon, P. ( 1 ) 434 Jarecki, C. ( 3 . 7 ) 28 Jarosiewicz, M. ( 1 ) 87 Jawad, H. ( 2 . 2 ) 2 3 , 24 Jefford, C.W. ( 3 . 5 ) 9 2 , 93

Jeffries, P.R. ( 3 . 3 ) 77 Jeffs, G.E. ( 3 . 2 ) 1 2 0 ; ( 3 . 7 ) 111

Jeganathan, M.B. ( 4 ) 124 Jeger, 0 . ( 3 . 1 ) 3 5 ; ( 3 . 2 )

569 Jones, R.D. ( 1 ) 324 Jones, R.G. ( 4 ) 103 Jones, R.J. ( 3 . 4 ) 1 2 3 ; ( 3 . 6 ) 159

Jones, S.B. ( 2 . 2 ) 6 Jones, S.K.R. ( 4 ) 456 Jones, W.D. ( 2 . 2 ) 67 Jones, W.J. ( 1 ) 1 9 Jones, W.M. ( 2 . 2 ) 9 0 , 91 Jong, D.-J. ( 1 ) 16 Joran, A.D. ( 5 ) 131 Joranovic, D. ( 4 ) 367 Jordan, K. ( 4 ) 264 Jorritsma, R. ( 3 . 2 ) 102 Joshi, N. ( 1 ) 372 Joussot-Dubien, J. ( 1 ) 106

Jovanovic, S. ( 4 ) 64 Jovin, T.M. ( 1 ) 7 3 56, 57; ( 3 . 3 ) 7 0 , 7 1 , 1 3 3 ; ( 3 . 7 ) 133-135, 137 Jug, K. ( 3 . 7 ) 3 Jenden, C.M. ( 4 ) 362 Junnarkar, M.R. ( 1 ) 377 Jenkins, A.D. ( 4 ) 7 0 Juo, R.R. ( 3 . 5 ) 8 1 Jennesken, L.W. ( 3 . 4 ) 3 Jurgens, A. ( 3 . 4 ) 104 Jenny, B. ( 5 ) 175 Juris, A . ( 2 . 1 ) 7 8 , 7 9 , Jensen, B.L. ( 3 . 7 ) 144 1 3 0 ; ( 5 ) 5 5 , 58 Jensen, N.-H. ( 1 ) 421 Justus, B.L. ( 1 ) 6 4 , 65 Jesion, G . ( 1 ) 411 Jian, S.Z. ( 4 ) 4 0 6 , 427 Jiang, F.-B. ( 1 ) 387 Kabaivanov, V. ( 4 ) 353 Jiang, L. ( 3 . 3 ) 127 Kabanov, V.A. ( 4 ) 1 1 9 , Jian-hu, X. ( 3 . 2 ) 7 3 204 Jin, T. ( 2 . 1 ) 6 8 Kabasawa, Y. ( 3 . 2 ) 8 1 , Jingui, M. ( 1 ) 1 0 3 , 442 8 2 , 85 Jirakova-Audouin, L. ( 4 ) Kabir, S.E. ( 2 . 2 ) 77 Kabumoto, A. ( 3 . 5 ) 53 4 20 Jirousek, M. ( 3 . 5 ) 137 Kachan, A.A. ( 4 ) 1 5 3 , 315 Jitsumatsu, T. ( 4 ) 28 Kaczmarck, H. ( 4 ) 322 Johansen, 0 . ( 2 . 1 ) 1 1 4 ; Kaddouri, A. ( 1 ) 418 Kadota, H. ( 3 . 4 ) 8 2 ; (5) 71 Johansson, L.B.-A. ( 1 ) 47 ( 3 . 6 ) 134 Johnson, B.V. ( 2 . 2 ) 32 Kafafi, Z.H. ( 2 . 2 ) 82 Johnson, C.R. ( 2 . 1 ) 206 Kagan, J. ( 3 . 4 ) 181 Johnson, G.P. ( 3 . 3 ) 1 3 7 ; Kageyama, H. ( 3 . 2 ) 5 1 ; ( 3 . 6 ) 66

( 3 . 4 ) 154

Johnson, I.D. ( 1 ) 166 Johnson, M.D. ( 2 . 2 ) 110 Johnson, R.P. ( 3 . 3 ) 57-

Kagi, J.H.R. ( 1 ) 342 Kagiya, T. ( 3 . 5 ) 4 4 ; ( 4 )

5 9 , 6 5 ; ( 3 . 4 ) 2 9 , 117 Johnson, T.J. ( 2 . 1 ) 162 Johnston, L.J. ( 1 ) 465, 499; ( 3 . 1 ) 9 , 24, 26; ( 3 . 4 ) 1 2 9 , 130 Jolidon, S. ( 3 . 6 ) 101 Jolliet, P. ( 2 . 1 ) 175 Jones, A.C. ( 1 ) 319 Jones, D.J. ( 2 . 2 ) 72 Jones, G. ( 1 ) 216; ( 2 . 1 ) 9 9 ; ( 3 . 5 ) 30, 39, 143; ( 5 ) 8 7 , 8 8 , 137 Jones, G.R. ( 1 ) 101 Jones, J. ( 4 ) 65 Jones, M. ( 3 . 7 ) 7 4

Kahlow, M.A. ( 1 ) 223 Kaiser, G. ( 3 . 2 ) 128 Kaiser, W. ( 1 ) 2 0 6 , 378 Kaizu, Y. ( 2 . 1 ) 228 Kaji, N. ( 2 . 1 ) 232; ( 3 . 5 )

372; ( 5 ) 182

34; ( 5 ) 68, 89, 9 0 , 94, 9 5 , 140 Kajitani, M. ( 2 . 2 ) 8 3 , 8 4 ; ( 5 ) 77 Kajiwara, Y. ( 1 ) 189 Kakisawa, H. ( 3 . 2 ) 9 Kakitani, K. ( 1 ) 146 Kakitani, T. ( 5 ) 121 Kakiuchi, K. ( 3 . 2 ) 2 3 ; (3.4) 3

Kalashmik, A.T. ( 4 ) 414 Kalbas, C . ( 2 . 2 ) 55 Kaliaguine, S. ( 2 . 1 ) 63 Kalinnikov, V.T. ( 2 . 2 ) 37 Kalisky, Y. ( 4 ) 211 Kalkar, C.D. ( 1 ) 504 Kallfass, D. ( 3 . 3 ) 7 6 Kalliorinne, K. ( 3 . 7 ) 102 Kallir, A.J. ( 1 ) 437 Kalontarov, I.Ya. ( 4 ) 428 Kalyanasundaram, K. ( 1 ) 217; ( 2 . 1 ) 1 7 7 ; ( 5 ) 82

Kamat, P.V. ( 4 ) 8 1 , 263 Kambayashi, M. ( 4 ) 7 3 Kametani, T. ( 3 . 5 ) 127 Kamigata, N. ( 3 . 4 ) 1 8 6 ; ( 3 . 6 ) 165

Kaminsika, A. ( 4 ) 322 Kamiya, M. ( 3 . 2 ) 114 Kamiyama, N. ( 3 . 5 ) 103 Kamogawa, H. ( 3 . 5 ) 3 7 ; ( 4 ) 210; ( 5 ) 155

Kamphuis, J. ( 3 . 2 ) 1 4 9 , 165; ( 3 . 6 ) 1 2 1 , 180

Kan, S.L. ( 3 . 2 ) 99; ( 3 . 6 ) 87

Kanai, M. ( 3 . 4 ) 9 9 ; ( 3 . 5 ) 122

Kanakarajan, K. ( 3 . 7 ) 47 Kananiaru, N. ( 1 ) 326 Kanaoka, Y. ( 3 . 2 ) 1 3 5 , 1 4 0 , 1 4 2 , 145-147, 1 5 1 ; ( 3 . 4 ) 96 ( 3 . 6 ) 8 0 , 8 1 , 83, 114, 116, 126, 128, 179, 1 8 1 , 183, 1 8 4 , 1 8 6 ; ( 3 . 7 ) 1 4 7 , 148 Kanatomi, H. ( 1 ) 511 Kane, C . ( 1 ) 31 Kane, V.V. ( 2 . 2 ) 7 9 Kaneko, C. ( 3 . 2 ) 2 4 , 4 1 ; ( 3 . 6 ) 2 0 , 9 0 , 97 Kaneko, M. ( 2 . 1 ) 1 2 0 ; ( 5 ) 1 1 , 1 5 3 , 154

Kane-Maguire, N.A.P. ( 2 . 1 ) 4 4 , 46

Kanematsu, K. ( 3 . 2 ) 132 Kanemoto, A. ( 1 ) 447 Kang, H.K. ( 3 . 2 ) 9 8 ; ( 3 . 6 ) 93

Kang, W.S. ( 4 ) 32 Kang. Z.H. ( 1 ) 196 Kanno, H. ( 2 . 1 ) 2 4 ; ( 5 ) 173

Kano, K. ( 1 ) 274; ( 3 . 7 ) 131

Kanofsky, J.R. ( 1 ) 505 Kanoktanaporn, S. ( 1 ) 216 Kanstrup, A. ( 3 . 2 ) 101 Kapinus, E . I . ( 1 ) 472 Kaplan, A.M. ( 5 ) 34 Kaplan, L. ( 3 . 4 ) 21 Kaplan, R. ( 1 ) 75

570 Karasev, V.E. ( 2 . 3 ) 5 Karatsu, K. ( 1 ) 188, 439 Karavaev, A.D. ( 2 . 1 ) 106 Karle, I . L . ( 3 . 6 ) 126 Karlivam, V. ( 4 ) 286 Karminski-Zamola, G. (3.4) 143 Karnaukh, A.P. ( 4 ) 75 Karplyuk, V.A. ( 4 ) 370 Karpukhin, O.N. ( 4 ) 454 Kartuzhanskii, A.L. ( 2 . 1 ) 195 Karup, G. ( 3 . 2 ) 101 Karuyama, K. (3.4) 80 Karvas, M. ( 4 ) 403 Kasai, N. (3.4) 167 Kashuba, E.V. ( 5 ) 207 Kasprzyk, P.G. ( 1 ) 360 Kastening, B. ( 5 ) 219 Katagiri, N. ( 3 . 6 ) 20, 97 Katakis, D. ( 2 . 1 ) 170; ( 5 ) 76 Katayama, T. ( 4 ) 451 Kato, H. ( 4 ) 28 Kato, K. ( 3 . 5 ) 8 2 Kato, M. ( 2 . 2 ) 139; (2.3) 27; (3.3) 50; (3.5) 123; ( 3 . 6 ) 197; ( 4 ) 23, 27, 172; ( 5 ) 203 Kato, N . ( 3 . 2 ) 1 4 Kato, S. ( 5 ) 148 Kato, T. ( 3 . 2 ) 81-83, 85 Katritzky, A.R. (3.4) 126 Katsukura, Y. (3.5) 8 6 Katz, T.J. (3.4) 109 Kauffmann, H.F. ( 4 ) 269 Kaufman, S . J . ( 1 ) 7 3 Kaufmann, F. (3.6) 51 Kaupp, G. ( 3 . 4 ) 52; ( 3 . 7 ) 119 Kawaguchi, H. (5) 164 Kawaharada, Y. (2.2) 8 4 Kawai, K. ( 5 ) 199 Kawamura, T. (2.2) 56 Kawamura, Y. ( 3 . 3 ) 124; (3.6) 104 Kawanishi, Y. ( 2 . 1 ) 90, 127; ( 5 ) 61, 122 Kawase, K. ( 3 . 3 ) 95; ( 5 ) 53 Kawata, H. ( 3 . 6 ) 60 Kawata, K. (2.1) 200 Kawata, S. ( 2 . 1 ) 147 Kawato, T. (1) 511 Kawatsuki, N. ( 3 . 1 ) 47; (3.4) 150 Kawski, A. ( 1 ) 209, 350, 384, 456 Kayak, Ya.A. ( 4 ) 344 Kayakawa, Y. (3.3) 9 5 Kazachkova, O.L. ( 4 ) 344 Kazakov, V.P. ( 2 . 1 ) 106,

Author Index 222, 249; ( 2 . 3 ) 57 Kazama, S. (3.2) 114 Kazuya, M. ( 3 . 3 ) 117 Kazyaka, T.G. ( 4 ) 365 Keene, J.P. (1) 480 Keese, R. (3.4) 38, 39 Keghouche, N. (2.1) 164; (5) 105 Keller, B.A. ( 2 . 3 ) 33 Keller, R.A. ( 1 ) 68 Kelley, C.K. ( 2 . 2 ) 127: (5) 45 Kelley, D.F. ( 1 ) 1 6 Kellog, R.M. ( 3 . 5 ) 51 Kelly, J.M. ( 2 . 2 ) 7 3 Kemp, G. (3.3) 141; ( 3 . 7 ) 155 Kemp, T.J. ( 1 ) 1 6 3 , 454 Kenig, S. ( 4 ) 349 Kenimov, M.K. ( 4 ) 294 Kenji, F. ( 4 ) 141 Kenkre, V.M. ( 1 ) 247 Kennedy, J. ( 1 ) 417 Kennelly, T. (2.1) 122 Kenney, J.W. ( 2 . 2 ) 114 Kenney, M.I.S. ( 2 . 2 ) 114 Kenney-Wallace, G.A. (1) 79, 123 Kerr, S.R. ( 4 ) 138 Kessel, D. ( 1 ) 416, 480 Kesselmayer, M.A. ( 3 . 7 ) 6, 7 Kevan, L. ( 1 ) 300; ( 3 . 5 ) 133 Keys, D.E. ( 3 . 7 ) 26 Keyser, P. (5) 34 Khac, D.D. ( 3 . 2 ) 36 Khamzamulina, R.E. ( 4 ) 203, 208 Khan, A . Y . ( 2 . 3 ) 39 Khan, J . D . (3.5) 21 Khan, M.M. ( 5 ) 218 Khanna, R . N . ( 3 . 4 ) 177 Khanova, L.A. (5) 227 Kharitonov, A.P. (2.3) 44 Khimich, N.N. ( 3 . 7 ) 76 Khokhlova, V.P. ( 2 . 1 ) 222 Kholmanskii, A.S. (3.6) 40 Kholmogorov, V.E. ( 5 ) 29 Kholodova, N.V. ( 3 . 4 ) 128; (3.6) 29 Khripach, V.A. ( 3 . 5 ) 117 Khristova, N.N. ( 4 ) 129 Khvorostovskii, S.N. (2.3) 42 Khvostova, V.P. (2.1) 136 Kido, K. ( 3 . 2 ) 132 Kido, M. (3.6) 9 6 Kiesewetter, R. (3.2) 66 Kieu, H.T. ( 2 . 3 ) 4 Kihara, M. ( 3 . 4 ) 146

Kikkawa, M. ( 2 . 1 ) 147 Kikuchi, K. ( 1 ) 6 3 , 208, 447, 493; ( 3 . 5 ) 35 Kilhoffer, M.-C. ( 1 ) 358 Kim, D.H. ( 1 ) 376, 469 Kim, H.J. ( 1 ) 234; ( 3 . 3 ) 28 Kim, H.S. ( 4 ) 149 Kim, J.H. (2.1) 146 Kim, K . J . ( 4 ) 149, 150, 24 1 Kim, W. ( 4 ) 194 Kim, Y. (2.1) 127; ( 5 ) 61 Kim, Y.D. (3.4) 183; ( 3 . 6 ) 45 Kimoto, M. ( 1 ) 189 Kim-Thuan, N. ( 1 ) 461 Kimura, E. ( 1 ) 131 Kimura, M. ( 2 . 1 ) 101, 105, 123 Kimura, S. ( 2 . 2 ) 39 Kincaid, J . R . (2.1) 88; ( 5 ) 56 King, D. ( 4 ) 456 King, J.A. ( 2 . 2 ) 107 King, R.B. (2.2) 96 King, R.K. ( 3 . 2 ) 73, 74 Kinoshita, S. ( 1 ) 29 Kinoshita, T. ( 4 ) 218 Kira, M. ( 2 . 3 ) 15, 1 6 ; ( 3 . 4 ) 172, 190; ( 3 . 6 ) 201, 202, 207 Kirchhof, B. (3.5 149; ( 4 ) 445 Kirchhoff, J . R . ( 2 . 1 ) 11 Kirk, A.D. ( 2 . 1 ) 4 2 , 45 Kirk, N.J. ( 1 ) 332 Kirsch, B. ( 1 ) 21 Kirschenheuter, G.P. ( 3 . 5 ) 78 Kiryukhin, Yu.1. ( 5 ) 217 Kisch, H. ( 2 . 1 ) 242, 243; ( 5 ) 72, 7 3 Kisilev, A . (2.1) 199 Kislinger, J. (2.1) 135 Kissinger, P.T. ( 1 ) 33 Kita, H. ( 2 . 1 ) 29; ( 5 ) 176 Kita, T. (2.1) 232; ( 3 . 5 ) 34; (5) 8 9 , 94. 9 5 , 140 Kitaigorodskii, A . N . ( 2 . 2 ) 132 Kitami, S. ( 3 . 2 ) 31 Kitamura, A . ( 1 ) 486; ( 3 . 7 ) 26 Kitamura, N. ( 1 ) 506; (2.1) 90, 127; ( 5 ) 61, 122 Kitamura, S. ( 2 . 2 ) 104 Kitamura, T. ( 3 . 7 ) 177 Kitani, T. (5) 148 Kitao, T. ( 4 ) 449, 450;

Author Index ( 5 ) 69

Kivana, D. ( 2 . 1 ) 20 Kiwi, J. ( 5 ) 186, 206 Klabunovskii, E . I . ( 5 ) 144

Klarner, F.-G.

(3.3) 111; ( 3 . 7 ) 16 Klafyer, J. ( 1 ) 249 Kleijn, M. ( 2 . 1 ) 100; ( 5 ) 119 Kleiner, E. ( 3 . 2 ) 103 Klemm, E. ( 4 ) 41, 71 Klett, M.W. ( 3 . 3 ) 5 9 ; ( 3 . 4 ) 117 Kliger, D.S. ( 2 . 1 ) 8 2 , 152; ( 3 . 2 ) 96 Klimenko, B.B. ( 3 . 1 ) 25 Klimenko, L.S. ( 3 . 2 ) 167 Klock, A. ( 1 ) 184 Kloosterboer, J.G. ( 4 ) 132 Klotzbuecher, W.E. ( 2 . 2 ) 1 7 , 73 Klug, G. ( 3 . 5 ) 77 Klunder, A.J.H. ( 3 . 2 ) 7 Klvana, D. ( 5 ) 163 Kmelinskii, I . V . ( 2 . 1 ) 191 Kneuper, H.J. ( 2 . 2 ) 38 Knight, J. ( 3 . 7 ) 172 Knoesel, R. ( 4 ) 265 Knoester, J. ( 1 ) 1 2 ; 279 Knoll, P. ( 4 ) 189 Knothe, L. ( 3 . 3 ) 105, 106; ( 3 . 6 ) 100 Knox, C.N. ( 1 ) 477 Knox, R . S . ( 1 ) 261 Knox, S.A.R. ( 2 . 2 ) 38 Knudsen, P.H. ( 3 . 2 ) 101 Knutson, J . R . ( 1 ) 4 4 , 4 5 , 321 Knyazhanskii, M . I . ( 2 . 1 ) 188; ( 3 . 4 ) 126-128; ( 3 . 6 ) 28, 29 Kobayashi, E. ( 3 . 4 ) 158; ( 4 ) 59 Kobayashi, H. ( 2 . 1 ) 228; ( 3 . 3 ) 50 Kobayashi, K. ( 3 . 2 ) 4 0 ; ( 3 . 5 ) 76 Kobayashi, M. ( 3 . 4 ) 186; ( 3 . 6 ) 165, 211 Kobayashi, S. ( 3 . 4 ) 1 4 6 ; ( 3 . 7 ) 177 Kobayashi, T. ( 1 ) 164, 269; ( 2 . 2 ) 49-51, 5 9 ; ( 4 ) 225; ( 5 ) 148 Kober, E.M. ( 2 . 1 ) 134 Koch, H. ( 3 . 1 ) 1 Koch, R. ( 3 . 5 ) 99; ( 4 ) 445 Kocherov, A.V. ( 4 ) 129

57 1 Kochi, J . K .

(1) 172, 182; ( 3 . 4 ) 56, 103, 165; ( 3 . 6 ) 140 Kodama, S. ( 2 . 1 ) 244; ( 5 ) 190, 202 Koek, J.H. ( 3 . 2 ) 72 Koffi, P. ( 2 . 1 ) 128; ( 5 ) 84 Koga, K. ( 3 . 2 ) 5 Kogan, V.A. ( 2 . 1 ) 188 Kohjiya, S . ( 4 ) 209; ( 5 ) 159 Kohler, B. ( 3 . 3 ) 81 Kohmoto, K. ( 1 ) 452 Kohmoto, S . ( 3 . 5 ) 9 2 , 93 Kohzu, M. ( 3 . 5 ) 140; ( 3 . 6 ) 156 Koike, T. ( 1 ) 208 Koizumi, H. ( 1 ) 83 Kojima, A. ( 3 . 2 ) 30 Kojima, K. ( 3 . 5 ) 25; ( 4 ) 293 Kojima, M. ( 3 . 3 ) 13 Kojima, N. ( 3 . 6 ) 32 Kojima, T. ( 2 . 1 ) 181; (3.2) 9 Kokado, H. ( 4 ) 245 Kokkes, M.W. ( 2 . 2 ) 5 7 , 58 Kokubu, T. ( 3 . 4 ) 161 Kokubun, H. ( 1 ) 6 3 , 208, 447, 493; ( 3 . 5 ) 3 5 ; ( 3 . 6 ) 60 Kokunova, V.N. ( 2 . 1 ) 133 Koleski, J . V . ( 4 ) 26, 104 Kolling, E. ( 1 ) 378 Kolodziej, R.M. ( 2 . 2 ) 18 Komatsu, N. ( 3 . 6 ) 204 Komiyama, K. ( 3 . 2 ) 16 Komorowski, S.J. ( 1 ) 435 Komozin, P.N. ( 2 . 1 ) 133 Konak, C. ( 4 ) 239 Konaka, R. ( 3 . 5 ) 24 Konarski, J. ( 2 . 1 ) 202 Konda, H. ( 3 . 6 ) 162 Kondo, A. ( 2 . 2 ) 8 3 , 8 4 ; ( 5 ) 77 Kondo, K. ( 3 . 5 ) 73 Kondo, M. ( 3 . 2 ) 5 3 ; 3 . 6 ) 123 Kondow, T. ( 1 ) 491 Konijnenberg, J. ( 1 ) 89 179; ( 3 . 4 ) 65 Konopikova, M. ( 3 . 6 ) 58 Konstantatos, J. ( 2 . 1 170; ( 5 ) 76 Konstantinova, A.V. ( 3 . 2 ) 167 Koob, R.D. ( 2 . 3 ) 24, 25 Koolhaas, W.E. ( 3 . 4 ) 3 Kopelman, P. ( 4 ) 199 Koper, N.W. ( 1 ) 176; ( 5 ) 125

Kop'eva, L.G. ( 2 . 3 ) 42 Korobitsyna, I.K. ( 3 . 7 ) 76

Korolev, G.V. ( 4 ) 156 Korotkikh, O.A. ( 2 . 3 ) 5 Korotkov, V . I . ( 5 ) 29 Korovin, Yu.V. ( 2 . 1 ) 214 Koshiba, M. ( 4 ) 137 Koshima, H. ( 2 . 1 ) 39 Koskikallio, J. ( 3 . 7 ) 102, 176

Kosmider, B.J. ( 3 . 2 ) 11 Kossanyi, J. ( 1 ) 94; ( 4 ) 444

Kostermans, G.B.M.

(3.3)

75

Kosugi, N. ( 2 . 1 ) 33; ( 5 ) 27

Kotani, M. ( 1 ) 139 Kotzian, M. ( 2 . 2 ) 21 Kouchi, N. ( 1 ) 83 Kougo, Y. ( 2 . 3 ) 27 Koulkes-Pujo, A.M. ( 5 ) 135

Koutek, B. ( 3 . 3 ) 8 4 ; ( 3 . 4 ) 10

Kovacevic, V. ( 4 ) 335 Kowalski, J. ( 3 . 4 ) 8 4 ; ( 3 . 6 ) 208

Koya, G. ( 2 . 1 ) 186 Koyama, H. ( 1 ) 511 Koyama, K. ( 3 . 6 ) 81 Kozel, S.P. ( 3 . 4 ) 174; ( 4 ) 79

Koz'menko, M.V. ( 3 . 4 ) 2 Kraakman, P.A. ( 3 . 4 ) 3 Kracke, G. ( 1 ) 372 Kraft, G. ( 2 . 2 ) 55 Krakovyak, M.G. ( 3 . 4 ) 174; ( 4 ) 7 9 , 169, 249

Kramarenko, A.S. ( 4 ) 327 Kramer, A. ( 2 . 2 ) 25 Kramer, H.E.A. ( 1 ) 210 Kranovskii, V.A. ( 4 ) 74 Krantz, A. ( 3 . 5 ) 16 Krausz, E. ( 2 . 1 ) 87 Kreiter, C.G. ( 2 . 2 ) 21, 26, 53

Kremer, E.B. ( 4 ) 183 Kresins, E. ( 4 ) 285 Krespan, C.G. ( 3 . 7 ) 85 Krestonosich, S. ( 3 . 4 ) 68 Kretzschmar, G. (3.7) 112 Kreysig, D. ( 2 . 3 ) 4 8 , 49; ( 3 . 3 ) 8 5 ; ( 3 . 4 ) 175, 176; ( 3 . 6 ) 124 Krichevskii, G.E. ( 4 ) 454 Krieger, C. ( 3 . 7 ) 126 Krishnan, C.V. ( 2 . 1 ) 109 Krishnan, S. ( 4 ) 343 Krishnan, V. ( 1 ) 177; ( 5 ) 129

Author Index

572 Kriss, E. ( 2 . 1 ) 67 K r i s t e n s e n , 0. ( 1 ) 30 Krogh, K. ( 3 . 4 ) 107 Krok, K. ( 4 ) 290 Krone, K.P. ( 1 ) 76 K r o n f e l d , K.P. ( 3 . 7 ) 8 3 Krongauz, V. ( 4 ) 216 Kropp, P.J. (3.3) 1 Kriiger, C. ( 2 . 2 ) 5; ( 3 . 3 ) 106; ( 3 . 4 ) 47; ( 3 . 6 ) 100, 120 Krupadanam, G.L.D. ( 3 . 4 ) 140 K r u p i t s k i i , S.V. ( 2 . 1 ) 227 Krusic, P.J. (2.2) 72, 75; ( 3 . 7 ) 2 Kryszewski, M. ( 4 ) 307 Kryukov, A . I . (2.1) 6 2 , 67 Ku, H.S. ( 3 . 6 ) 168 Kubiak, C.P. ( 2 . 2 ) 125 Kubichi, A. ( 1 ) 209 Kubo, M. ( 4 ) 3 Kubo, Y. ( 3 . 2 ) 136, 143, 144, 148, 153-157; ( 3 . 4 ) 48-50; ( 3 . 6 ) 108111, 113, 115, 117, 135 Kubokawa, Y. ( 2 . 1 ) 244; (5) 167-169, 1 9 0 , 202 Kubota, H. ( 4 ) 42 K u c h i t s u , K. ( 1 ) 491 Kuchmii, S.Ya. ( 2 . 1 ) 62 Kudo, A. ( 2 . 1 ) 33; ( 5 ) 25, 27 Kudo, H. ( 3 . 4 ) 121, 145; ( 3 . 6 ) 161 Kuehnle, W. ( 5 ) 124 Kugler, K . J . ( 1 ) 76 Kuhnert, L. ( 2 . 1 ) 107 Kulagina, L.V. ( 3 . 5 ) 62 Kulagowski, J.J. ( 3 . 7 ) 33, 34 Kuleshov, S.P. ( 2 . 3 ) 57 Kuliev, A.M. ( 4 ) 410 Kulikowska, E. ( 3 . 2 ) 97 Kulkar, M.G. ( 3 . 2 ) 18 K u l l b e r g , M.L. ( 2 . 2 ) 125 K u l l n i g , R.K. ( 3 . 1 ) 28; (3.7) 23 Kumagai, T. ( 3 . 3 ) 4 4 , 4 5 , 124; ( 3 . 6 ) 60, 104 Kumamoto, S. ( 3 . 2 ) 50 Kumamoto, Y. ( 3 . 7 ) 69 Kumar, C . V . (1) 386, 476, 490; ( 3 . 2 ) 6 3 , 124; ( 3 . 3 ) 135; ( 3 . 6 ) 54; ( 3 . 7 ) 136 Kumar, S. (1) 336 Kume, H. ( 1 ) 35 Kun, H.B. (1) 506 Kundu, T. ( 1 ) 133

( 3 . 4 ) 1; (3.6) 35, 163; ( 4 ) 177 Lach, P. (3.3) 51-55 Lacher, B. (3.7) 114 L a c o s t e , J. ( 4 ) 312 Laczko, G ( 1 ) 348 Ladouceur, G. ( 3 . 6 ) 7 3 L a e u f e r , M. (3.1) 13 Lagnov, V.M. ( 4 ) 156 Lahav, M. ( 3 . 1 ) 1 0 , 11 L a i , Z. ( 3 . 2 ) 46 Lakin, D.C. (3.5) 7 8 Lakowicz, J . R . ( 1 ) 38, 132, 348 L a l , K. (3.3) 116 L a l a n d i , M. ( 1 ) 72 Lalanne, J . R . ( 1 ) 286 L a l o , C. ( 3 . 5 ) 142 La-Mantia, F.P. ( 4 ) 306 Lamberts, J.J.M. ( 3 . 4 ) 134 Lamette, M. ( 1 ) 106 Lami, H. ( 1 ) 167 Lammel, U. ( 4 ) 39 Lamos, M.L. ( 1 ) 391 Lampe, F.W. (2.3) 11 Lan, A . J . Y . ( 3 . 6 ) 137 Lan, J . Y . ( 3 . 4 ) 7 6 ; ( 3 . 6 ) 219 Lan, M.R. (1) 196 Land, E.J. ( 1 ) 477, 480 Landahl, P.S. ( 4 ) 188 Landon, S . J . ( 2 . 2 ) 44 L a n f r a n c h i , M. (3.5) 119 Lang, J . ( 1 ) 284, 287 Langa, F. (3.3) 72; ( 3 . 6 ) 27 Langbein, H. (3.5) 9 9 ; ( 4 ) 445 Lange, G.L. (3.2) 26, 28 Langford, C.H. ( 2 . 1 ) 140 L a n g k i l d e , F.W. ( 1 ) 421 Langley, A . J . ( 1 ) 19 L a n t r i p , D.A. ( 1 ) 33 Lanz, K. (3.2) 159 Lapcik, L. (3.3) 1 2 L a p i n , S.C. ( 3 . 7 ) 44-46 Laplane, J . P . ( 5 ) 21 L a P l a n t e , J.P. ( 1 ) 417 Lapouyade, R. ( 1 ) 162; ( 3 . 3 ) 90; ( 3 . 4 ) 132, 133 L a r a , S. ( 4 ) 355 L a r r y , R.E. ( 4 ) 230 Lashkov, G . I . (3.4) 17 ( 4 ) 79 L a t t , S.A. ( 1 ) 72 Lau, M.P. ( 1 ) 8 6 ; ( 3 . 6 Laarhoven, W.H. ( 3 . 3 ) 8 7 , 142 Lau, S. (3.2) 6; ( 3 . 6 ) 88; ( 3 . 4 ) 118, 119, 134, 135 172 Lau, W. ( 3 . 4 ) 103 L'Abbe, G. ( 3 . 7 ) 35 Lablache-Combier, A. L a u f e r , A.G.E. (1) 149

Kunin, A . J . (2.2) 120 Kunisch, F. (3.7) 75 Kunkel, L.M. (1) 72 Kunkely, H. (2.1) 5 Kuntyi, 0.1. ( 2 . 1 ) 6 1 Kuntz, R.R. ( 1 ) 168 Kunyama, A. ( 4 ) 58 Kunze, U . (2.2) 23, 24 Kunzer, H. ( 3 . 3 ) 110 KUO, P.-L. ( 1 ) 289, 290 Kuo, Y.H. ( 3 . 5 ) 131 Kupfer, M. ( 1 ) 161; ( 3 . 3 ) 85 Kurahashi, K. ( 2 . 1 ) 161; ( 5 ) 64 Kuramto, N. ( 4 ) 433, 449 Kurauchi, Y. ( 3 . 3 ) 3 4 ; ( 3 . 6 ) 136 Kurbako, V.Z. ( 3 . 5 ) 117 K u r i t a , J . (3.6) 5 7 , 71 K u r i t a , S. ( 2 . 1 ) 181 Kuroda, H. (2.1) 33; ( 4 ) 184; ( 5 ) 27 Kuroda, K. ( 3 . 5 ) 7 3 Kuroda, R. ( 1 ) 452 Kuroda, S. ( 3 . 5 ) 112 Kurokawa, H. ( 1 ) 388 Kurokawa, K. ( 1 ) 164 Kurtenbach, K. ( 1 ) 371 K u r t z , I. ( 1 ) 402 Kurucsev, T. ( 1 ) 202, 393 Kururnada, T. ( 4 ) 388, 396 Kurz, M. ( 3 . 3 ) 145; ( 3 . 7 ) 151 Kushida, T. ( 1 ) 29; ( 3 . 2 ) 31 Kushner, A.S. ( 3 . 4 ) 40 Kusumoto, Y. (1) 308 K u t a l , C. ( 2 . 1 ) 12; ( 2 . 2 ) 6 5 , 127, 129; ( 3 . 3 ) 103; ( 5 ) 7 , 4 0 , 4 5 , 48 Kuwabara, A. ( 2 . 1 ) 235; ( 5 ) 150 Kuwabara, H. ( 2 . 3 ) 27 Kuwano, A. ( 4 ) 112 Kuz'min, M.G. ( 1 ) 148; (3.4) 2 Kuzmin, V . A . ( 1 ) 471, 489 Kuz'min, V . G . ( 5 ) 227 Kuz'mina, N.A. ( 2 . 2 ) 61 Kuzmoney, H. ( 4 ) 189 Kuznetsov, E . I . (5) 107 Kuznetsova, I . M . ( 1 ) 338 K v i t k o , I.Ya. ( 3 . 6 ) 216 Kwon, I . C . ( 4 ) 6 1

573

Author Index Launikonis, A. ( 2 . 1 ) 110, 114, 141; ( 5 ) 9 7 , 98 L a u p r e t r e , F. ( 4 ) 195 Laurenson, P. ( 4 ) 305 L a u r e n t , A. (3.1) 55; ( 3 . 7 ) 107 L a u r e n t , C. ( 4 ) 291 Lavabre, D. ( 5 ) 21 L a v a l l e e , D.K. (2.1) 8 L a v i a l l e , F. (1) 399 L a v i e r i , F.P. ( 3 . 2 ) 8 7 , 106 Lavrikova, T.I. ( 3 . 7 ) 93 Lawrance, G.A. ( 2 . 1 ) 47 Laws, W.R. (1) 333, 334 Lawton, G. (3.7) 77 Lawton, J.B. ( 4 ) 227 Lay, P.A. ( 2 . 1 ) 110, 141; (5) 97, 98 L a z a r e , S. (3.4) 133; ( 4 ) 364 Lazarenko, E.T. ( 4 ) 80 Lazarev, L.N. ( 2 . 1 ) 227 L e a v i s , P.C. (1) 363, 364 LeBlanc, B.F. (3.1) 56; (3.7) 21 Lechner, J . A . ( 4 ) 328 Ledwith, A. ( 4 ) 166 Lee, C.Y. ( 2 . 2 ) 78, 8 6 Lee, F.L. ( 3 . 1 ) 39; (3.4) 151; (3.5) 11 Lee, H.W.H. ( 1 ) 438 Lee, J. ( 1 ) 183 Lee, J.L. ( 4 ) 20, 101, 241 Lee, K.D. (3.4) 144 Lee, K.H. ( 2 . 1 ) 146 Lee, K.W. (2.2) 64 Lee, L. (2.1) 155 Lee, L.Y.C. ( 1 ) 220; (3.5) 118; (5) 70 Lee, M. ( 1 ) 235; (3.2) 26 Lee, M.L. (3.4) 120, 121, 145; (3.6) 161 Lee, 0. ( 4 ) 246 Lee, S.W. (2.2) 6 2 Lee, Y.T. ( 3 . 3 ) 38 Leeming, S.A. ( 3 . 2 ) 10 Lees, A.J. (2.2) 18-20 Lefkowitz, S.M. ( 1 ) 448 Legros, B. ( 5 ) 39 Lehn, J . M . (2.1) 1 2 4 , 150 Lehr, G.F. (1) 304; ( 3 . 7 ) 2 L e i , X. ( 1 ) 492; ( 3 . 1 ) 6, 27; (3.4) 187 Leigh, W . J . ( 1 ) 451, 484 L e i g h t o n , P. (2.1) 241; (5) 130 Leihkauf, P. (3.7) 3 7 , 38 Leinwand, D.A. ( 1 ) 448 L e i s e r o w i t z , L. ( 3 . 1 ) 10,

11 Leismann, H. ( 3 . 1 ) 1; (3.4) 26 Leland, B.A. ( 5 ) 131 Lemaire, F. (3.6) 174 Lemaire, J . (2.1) 53, 54; ( 3 . 4 ) 12; ( 4 ) 298, 305, 310, 312, 330, 331, 348 Lemmetyinen, H. (1) 89; (3.4) 65 Lempereur, F. (3.5) 142 Lempers, E.L.M. ( 3 . 4 ) 28 Lenka, S. ( 4 ) 43, 110 Lenoble, C. (1) 508-510 L e n t s n e r , B.I. ( 5 ) 227 L e n t z , B.R. (1) 275, 277 Leonard, C. (4) 195 Leonova, G.V. ( 4 ) 274 Lerebours, B. (5) 141 Le ROUX, D. (2.1) 234; ( 5 ) 138 Le ROUX, P. ( 1 ) 299 Lesclaux, R. ( 3 . 5 ) 89 L e s h i n a , T.V. (3.5) 6 Leska, J. ( 3 . 6 ) 2 Lesma, G. (3.2) 6 4 L'Esperance, R.P. (3.5) 6 6 , 67 L e t a , S. ( 2 . 2 ) 93 L e t c h e r , R.M. (3.4) 113 Letokhov, V.S. (1) 392 Leung, H. (3.5) 88 Leung, M.S. (4) 376 L e v e n t i s , N, ( 2 . 2 ) 4 3 Lever, A.B.P. (2.1) 2, 131; ( 5 ) 6 Levin, V.S. ( 4 ) 431 Levin, Ya.A. (3.7) 1 Levine, A. ( 1 ) 182 L e v i t z , P. ( 1 ) 309 Levy, A. ( 1 ) 311 Levy, D.H. (1) 327 Levy, R.L. ( 4 ) 192, 1 9 3 Lewin, M . J . (2.2) 110 Lewis, D.M. ( 4 ) 456 Lewis, F.D. (3.3) -64 L e w i s , J.W. ( 2 . 1 ) 8 2 Lewis, P.N. ( 1 ) 396 Leyendecker, M. (2.2) 53 L i , G. ( 4 ) 4 9 , 50 L i , J. ( 4 ) 421 L i , M. ( 4 ) 85, 88, 89 L i , Q. (3.5) 57 L i , S. ( 4 ) 373 L i , X. ( 2 . 1 ) 161; (5) 64 L i , Y. ( 4 ) 373; ( 5 ) 177 L i , Z . ( 4 ) 217, 223 L i a n g , D. (3.2) 46 Liang, T.-Y. ( 3 . 7 ) 9 1 Liang, X. (3.5) 38 Liang, Z. ( 4 ) 89 Liauw, S. (5) 132

L i b e r t i n i , L.J. ( 1 ) 361 L i c i n i , G. (3.6) 1 7 1 L i c k i s s , P.D. ( 2 . 3 ) 19; (3.3) 4 ; (3.6) 199 Lieberman, R.A. ( 4 ) 139 L i g h t , J.R.C. (2.2) 79 L i j t e n , F.A.T. ( 3 . 3 ) 8 7 ; (3.4) 135 Limy B.T. (1) 151 Limy E.C. ( 1 ) 113, 151 L i n , C. ( 3 . 6 ) 170 L i n , C.H. ( 2 . 2 ) 78 L i n , 1,s. ( 4 ) 127 L i n , S.B. ( 4 ) 137 L i n , T.H. ( 1 ) 283 L i n , Z. (2.2) 74 Lindberg, B. ( 4 ) 36 Lindeman, T.G. (2.3) 2 Lindenberg, K. (1) 245, 246 L i n d q v i s t , L. ( 1 ) 323 L i p p i t s , G.J.M. ( 4 ) 132 L i s , S. ( 2 . 1 ) 202 Lisko, J . R . ( 2 . 2 ) 9 0 L i s s i , E.A. ( 1 ) 147, 288, 291, 458; ( 3 . 5 ) 9 ; ( 4 ) 82 L i t s o v , N.I. ( 4 ) 153; 315 L i t t l e , R.D. ( 3 . 7 ) 15 L i u , C.F. ( 3 . 2 ) 42 L i u , C.S. (2.2) 7 8 L i u , D. ( 4 ) 4 9 , 50 Liu, H.J. (3.2) 18 L i u , J.H. (3.4) 6 6 , 6 7 L i u , M.T.H. ( 3 . 7 ) 4 , 8, 9 , 11, 1 2 L i u , P. ( 4 ) 6 0 L i u , W. (2.1) 204; (3.6) 7 L i u , Y.C. (2.1) 27; ( 5 ) 191 L i u , Y.S. ( 1 ) 51 Lodder, G. ( 1 ) 180; ( 3 . 4 ) 27 Loder, J . W . ( 2 . 1 ) 114 Loeb, S.E.S. ( 3 . 4 ) 111 L o f r o t h , J.-E. ( 1 ) 46 Loffelman, F.F. ( 4 ) 405, 416 Loginov, A.V. (2.2) 108 Lohray, B.B. ( 3 . 2 ) 63 Lohse, F. ( A ) 359 Lohse, V. (3.7) 37, 38 Lombardo, D . A . ( 3 . 5 ) 20 London, S.J. ( 4 ) 4 8 Lopez, L. ( 3 . 5 ) 108 Lopez-Aparicio, F.J. (3.5) 101 Lopez-Arbeloa, F. ( 1 ) 330 Lopez-Campillo, A . ( 1 ) 169 Lopez-Espinoza, M.T.P.

Author Index

574 (3.5) 101

Lorch, E. (3.6) 51 Lorenzoni, E. (2.2) 80 Lougnot, D.J. (1) 461, 462

Louis, C. (5) 168 Lowry, R.E. (4) 237, 243, 252

Lozoskaya, E.L. (4) 430 Lu, H. (4) 60 Lu, s. (4) 373 Lu, x. (2.2) 74 Lu, Z.X. (1) 366 Lucchini, V. (3.6) 158 Luc-Gardette, J. (4) 298 Luciano, A3 (5) 20 Lucki, J. (4) 406, 407, 427

Luduena, R.F. (1) 345, 354

Ludwick, A.G. (4) 142 Luettke, W. (1) 206 Lugtenburg, J. (3.2) 72 Lukac, I. (4) 354 Lukomskaya, I.S. (4) 332 Luk'yanenko, L.V. (4) 78 Luk'yanov, B.S. (3.6) 41 Lunak, S. (3.5) 111 Lunt, E. (3.4) 126 Luss, H.R. (3.4) 189;

McCown, L.B. (1) 25, 40 McCullough, J.J. (1) 150 Macda, T. (4) 25 McDerrnott, G.A. (2.2) 46 MacDonald, P. (4) 405, 416

MacDonald, S.A. (4) 98 McEvoy, A.J. (2.1) 16; (5) 220

McGirnpsey, W.G. (3.2) 158; (3.7) 54, 58, 59

McGrath, W.D. (2.3) 32 McGuigan, C. (3.4) 57; (3.6) 127

McGuire, M. (1) 155; (5) 160

Machado, R. (3.1) 44, 45; (3.4) 46; (3.5) 13, 14

Machida, K. (2.2) 56 Machida, L. (3.6) 186 Machida, M. (3.2) 145-

147, 151; (3.6) 80, 114, 116, 179, 181, 183, 184 Macielag, M. (3.2) 106 Macinnis, W.K. (1) 150; (3.4) 152; (3.5) 17 McIntosh, A.R. (4) 226; (5) 126 Mackay, R.A. (5) 224 (3.6) 167 McKenna, G.B. (4) 237 Lutz, P. (4) 237 McKenna, W.P. (2.2) 60 Lux, B. (1) 335 Mackor, A. (3.3) 94; (5) Ly, C. (3.4) 24 43 Lyashenko, L.V. (2.1) 19; McLendon, G. (1) 155; (5) (5) 207 160 Lydon, J.D. (2.1) 110; McMahon, R.J. (3.7) 43, 50 (5) 98 Lyle, T.A. (1) 100 McMillin, D.R. (2.1) 11 Lytle, F.E. (1) 33, 409 McMorrow, D. (1) 243 McMullan, R.K. (3.1) 11 MacNeil, P.A. (2.2) 121 Ma, 2 . ( 4 ) 107, 398 Macrov, S.B. (4) 136 Maassen, J.A. (1) 404 Madge, D. (2.1) 40 McAllister, W.A. (2.1) Maekawa, Y. (1) 142 203 Miirkl, G. (3.6) 212 MacAlpine, D.K. (3.6) 144 Maertin, R. (4) 41 McArdle, P . J . (3.2) 8; Maestri, M, (2.1) 93, (3.4) 43 175; (5) 123 McAuliffe, C.A. (2.1) 66 Maglione, R. (3.5) 41; McCaffery, A.J. (1) 15 (3.6) 61 MacCallurn, J.R. (4) 296 Maguire, J.A. (2.2) 67 McCarthy, M.G. (2.1) 110; Mah, S. (4) 19 Mahaguchi, H. (1) 95 (5) 98 McCarthy, N.J. (4) 104 Mahgoub, S . A . (3.4) 79 McClanahan, S.F. (2.1) Mahieu, B. (2.1) 158; (5) 88; (5) 56 74, 104 McCleland, C.W. (3.5) Mahler, W. (3.1) 7 100; (3.7) 100 Maidan, R. (3.3) 143 McClelland, B.J. (1) 4 Maier, G. (3.2) 159; McClure, C.K. (3.7) 121 (3.3) 74, 76; (3.7) 68 Maier, V.E. (5) 103 Maccoll, R. (1) 261

Maiya, G.B. (1) 177; (5) 129

Majoral, J.P. (3.7) 87 Makarov, S.P. (3.4) 127; (3.6) 28, 36

Makhmadrnurodov, A. (5) 210

Makhonina, E.V. (5) 114 Maki, A.H. (1) 488, 496 Maki, Y. (3.6) 62 Makowska, B. (2.1) 202 Makunchi, K. (4) 272 Malati, M.A. (5) 188 Malba, G. (5) 88 Malba, V . (2.1) 99; (3.5) 39, 143; (5) 137

Maldotti, A. (2.1) 71 Malet, P. (5) 166 Maliaiah, B.V. (3.4) 140 Maliwal, B.P. (1) 38 Malkhasian, A.Y.S. (2.1) 140

Malkin, Ya.N. (3.6) 36 Malliaris, A. (1) 282, 284, 287

Mallory, C.W. (1) 229; (3.4) 111

Mallory, F.B. (1) 229; (3.4) 111

Maloney, V.M. (3.7) 54 Mal'tsev, A.K. (3.7) 5 Maltthys, E.F. ( 4 ) 300 Mamantov, A. (3.4) 90, 91 Marniche-Afara, S. (5) 230 Man, A.W.-H. (1) 297; (4) 280

Manabe, 0. (2.1) 189; (3.6) 11, 15

Mandal, K. (2.1) 94; (5) 92

Manfrin, M.F. (2.1) 150 Manh, D.D.H. (3.1) 18 Mani, J. (3.4) 38, 39 Manigand, C. (3.3) 90; (3.4) 132

Manning, L.E. (1) 187 Mansour, A.F. (5) 240, 204

Manuel, G. (3.7) 87 Marcandalli, B. (4) 113 Marcantonatos, M.D. (2.1) 207

Marchaj, A. (2.1) 50 Marchand, G.R. (3.3) 9 Marchant, M.J. ( 3 . 4 ) 110 Marchioro, C. (3.6) 158 Marciniec, B. (3.6) 151, 152

Marcinkowska, K. (2.1) 63 Marconi, G. (1) 90 Marden, M.C. (1) 365 Mardian, J.K.W. (1) 394

575

Author Index Mazzu, A. (3.4) 131 Mardirosyan, Z. (3.5) 139 Masuda, K. (3.1) 41; Mazzucato,, U. (1) 227 (3.6) 75 Margareth, J.C.M. (3.2) Meador, M.A. (1) 484; Masuda, T. (3.2) 15; 69 (3.1) 40 (3.4) 81; (3.6) 10; (4) Margaretha, P. (3.2) 6, Meallier, P. (1) 383; 123 17, 66; (3.6) 172, 173 (2.1) 246 Masude, H. (2.2) 56 Margerum, L.D. (5) 157 Meares, C.F. (1) 395 Masuhara, H. (1) 85 Margolin, A.L. (4) 431 Mechkovskii, S.A. (2.1) Masumo, K. (1) 485 Margrave, J.L. (2.2) 82 143 Mariano, P.S. (3.3) 140; Masumoto, Y. (3.7) 10 Meech, S.R. (1) 319 Mataga, N, (1) 85, 146, (3.6) 137, 138 Mehrotra, A. (3.1) 54; 259; (5) 121 Marignier, J.L. (5) 106 (3.7) 101 Mathews, R.W. (5) 36, 37 Mariotti, S. (1) 355 Mehrotra, K. (3.1) 54; Mathies, P. (3.1) 35; Markert, J. (3.3) 105, 106; (3.6) 100

Markovits, D. (1) 280 Marples, B.A. (3.3) 137; (3.6) 66

Marquet, J. (3.4) 73 Marrero, J.J. (3.7) 186 Marsau, P. (3.4) 173 Marsh, K.L. (5) 126 Marshall, J.L. (2.1) 134 Marsman, H.J.B. (1) 75 Martin, C.N. (4) 185, 206 Martin, C.R. (1) 293 Martin, G.F. (3.2) 37 Martin, J.W. (4) 328 Martin, L.L. (2.1) 47 Martin, R.H. (3.4) 110, 114, 115

Martinelli, M. (4) 76 Martinez-Lozano, C. (3.5) 126

Martinho, J.M.G. (1) 158, 257

Martinotti, F. (4) 314, 393

Martonosi, A. (1) 372 Marty, A. (1) 159 Marutani, M. (3.6) 33 Maruya, K. (5) 25 Maruyama, K. (3.2) 136, 143, 144, 148, 161-163; (3.6) 108, 111, 113 Maruyama, Y. (1) 105 Marx, J. (4) 196 Marynovski, S. (3.1) 46; (3.4) 155; (3.5) 15 Masaji, 0. (2.3) 6 Masamune, S. (2.3) 29; (3.6) 196 Masanet, J. (3.5) 142 Mashirov, L.G. (2.1) 219 Mashraqui, S.H. (3.5) 51 Mashyuk, A.F. (4) 74 Maslov, A.V. (2.1) 148; (5) 78 Masnovi, J.M. (1) 1 7 2 , 182; (3.4) 56, 165; (3.6) 140 Mason, J.D. (3.3) 1 Masotti, L. (1) 390

(3.3) 70; (3.7) 135

Matko, J. (1) 347 Matsuda, H. (4) 409 Matsuda, M. (4) 231 Matsuda, Y. (2.1) 39 Matsueda, S. (3.5) 86 Matsuhara, H. (4) 176 Matsumoto, M. (3.5) 73 Matsumoto, T. (3.4) 55; (3.6) 131

Matsuo, T. (5) 139, 156 Matsushima, R. (3.2) 51, 93; (3.4) 154; (3.6) 16 Matsushita, T. (5) 118 Matsuura, T. (1) 239; (3.1) 47; (3.2) 90; (3.3) 29; (3.4) 150; (3.5) 131; (3.6) 147 Matsuzawa, H. (4) 151 Matsuzawa, S. (2.3) 26; (3.4) 157; (3.6) 200 Mattauch, B. (3.7) 22 Mattay, J. (3.1) 12; (3.4) 23-26, 31 Mattei, P.L. (3.1) 17; (3.2) 65 Matthews, J.W.A. (4) 452 Matthews, R.S. (3.4) 42 Mattice, W.L. (1) 283 Mau, A.W.H. (2.1) 47, 110, 114, 141; (5) 71, 97, 98 Maukai, T. (3.3) 131 Maunnig, D. (3.6) 217 Maurizi, M.R. (1) 360 Mauzerall, D. ( 1 ) 32 Mayake, H. (5) 80 Mayer, E. (5) 62 Mayer, H. (3.3) 125 Mayer, J. (4) 290 Mayer, M. (3.7) 167 Mayer, W.J.W. (5) 38 Mayoux, C. (4) 291 Mayr, A. (2.2) 46 Mazur, D.J. (3.7) 121 Mazura, J. (4) 133 Mazzariello, R.G. (4) 26 Mazzocchi, P.H. (3.2) 137-139; (3.6) 107, 112

(3.7) 101

Mehta, G. (3.2) 84 Meier, K. (4) 359 Meijs, G.F. (3.7) 162 Meisel, D. (1) 140; (3.5) 134

Meissner, D. (5) 219 Melcher, R.L. (4) 365 Melikyan, V.V. (5) 229 Mel'nikov, M.Ya. (4) 51 Memarian, H.R. (3.4) 47; (3.6) 120

Memming, R. (5) 219 Mendenhall, G.D. (1) 503; (4) 273

Meng, L. (4) 50 Menghini, M. (2.1) 226 Mentha, Y. (3.6) 119 Menzel, R. (1) 205 Merola, F. (4) 253 Mes, G.F. (1) 176; (5) 125

Meseguer, F. (5) 235, 236 Meshkova, S.B. (2.1) 214 Messmer, C.H. (1) 342 Metui, H. (1) 315 Meunier-Piret, J. (2.1) 158; (5) 74

Mews, R. (3.7) 182 Meyer, T.J. (2.1) 13, 134; (2.2) 102; (5) 157

Meyer, V. (3.4) 38 Meyers, A . I . (3.2) 20; (3.6) 91

Meyerstein, D. (2.1) 166 Mialocq, J.C. (1) 299; (2.1) 234; (5) 135, 138

Michael, B.D. (1) 18 Michael, M.N. (4) 436 Michalczyk, M.J. (2.3) 2 1 Micheau, J.C. (5) 21 Michel-Beyerle, M.E. (5) 133

Michels, E. (2.2) 26 Michelsen, H.A. (1) 128; (3.6) 67

Michl, J. (2.3) 13, 21; (3.7) 88

Miehg, J.A. (1) 157, 158

576 Migita, Y. (3.2) 142 Miguel, M.G.M. (1) 296; ( 2 . 1 ) 216 Mihailov, S. (1) 198 Mihammad, M. (2.3) 39 Mihashi, S. (3.1) 48 Mikawa, H. (4) 17 Milazzani, Q.G. (5) 99 Milder, S.J. (2.1) 82, 151, 152; (3.2) 96 Miler, R . J . (1) 502 Miles, W.H. (2.2) 94 Milgrom, L.R. (5) 127 Mil'khiker, P.P. (4) 437 Milkie, T.H. (4) 337 Millar, D.P. (1) 226 Millard, R.R. (1) 219, 236 Miller, G.C. (3.5) 55 Miller, M.E. (2.2) 88 Miller, R.D. (3.7) 73; (4) 371 Miller, S.S. (2.1) 95 Millers, D. (4) 286 Milone, L. (2.2) 99 Milosavljevic, B.H. (2.1) 115, 116; (5) 161 Minaev, B.F. (3.5) 61 Minai, Y. (2.2) 71 Minamikawa, S. (3.2) 137, 139; (3.6) 107 Minana, M. (5) 106 Minemater, Y. (4) 302 Ming, Y. (3.3) 11; (3.5) 87, 109 Minkin, V . I . (3.6) 41 Minnesgern, H. (3.6) 191 Minsker, K.S. (4) 282, 4 29 Minto, F. (4) 355 Minton, K.W. (1) 337 Miranda, M.A. (3.4) 148, 180 Mirbach, M.F. (2.2) 16 Mirbach, M.J. (2.2) 16, 89 Miroshnichenko, I . V . (2.1) 133 Misawa, H. (3.5) 2 7 , 36 Mishakov, G.V. (2.3) 46 Mishin, K.Ya. (2.1) 227 Mishra, A . K . (1) 127, 136 Mishra, S.P. (1) 380 Miskowski, V.M. (2.1) 149 Mislavskii, B.V. (4) 119 Misumi, S. (3.4) 158, 166, 167 Mita, I. (1) 96, 211, 270; (4) 175, 198, 214, 236 Mitchel. E. (3.7) 166 Mitchell, G. (3.7) 32

Author Index Mitchell, S. (2.2) 110 Mitina, V.G. (3.2) 44 Mitra, S.B. (4) 343 Mitsuzuka, M. (1) 493; (3.5) 35 Miwa, T. (3.3) 50 Miyagawa, K. (1) 460 Miyajima, M. (4) 439 Miyake, S. (3.7) 177 Miyake, Y. (3.4) 146 Miyama, H. (2.1) 235; (4) 112; (5) 150, 197 Miyama, Y . (3.5) 128 Miyamoto, T. (3.6) 150 Miyasaka, H. (1) 85 Miyashita, A. (3.3) 118 Miyata, 0. (3.6) 31, 32 Miyauchi, Y. (2.1) 126 Miyaura, N . (3.7) 185 Miyazaki, K. (3.6) 11 Mizera, F.P. (4) 376 Mizoguchi, T. (3.2) 142; (3.6) 82 Mizumoto, K. (3.5) 53 Mizuno, K. (2.3) 10; (3.1) 41; (3.3) 126; (3.4) 74, 75; (3.5) 103, 106, 107; (3.6) 75, 209; (5) 47 Mizutani, T. (3.3) 23 Mlynek, C. (3.4) 108 Moan, J. (1) 415 Mochida, K . (2.3) 55 Modak, S.K. (4) 93 Modena, G. (3.6) 158 Modinos, A . (1) 4 Mobius, K. (2.1) 41 Moeller, W. (1) 404 Moger, G. (3.5) 63 Moggi, L. (2.1) 3, 142, 150; (5) 54, 99 Mohanty, I . B . (4) 43 Mohri, T. (1) 375 Molla, A.H. (2.2) 76 Molla, M.E. (2.2) 76, 77 Momose, Y. (3.2) 41 Monnerie, L. (4) 160, 168, 195, 212, 253, 257, 270 Monnier, E. (1) 305 Monnoret, J. (4) 205 Montavon, F. (3.6) 52 Montoro, T. (1) 169 Moody, C.J. (3.6) 166; (3.7) 33, 34, 77, 98, 99 Mooney, W. (2.1) 221 Moore, D.E. (3.5) 7 Moore, R.A. (1) 183 Moore, W.M. (2.2) 135; ( 3 . 3 ) 102; ( 5 ) 44 Mooring, A.M. (3.7) 50

Moorman, A.r. (3.6) 168 Morabito, P. (3.6) 141 Morales, P. (2.1) 226 Moralev, V.M. (2.3) 54 Morantz, D.J. (4) 197 Morawetz, H. (4) 180, 223, 271 Moreno-Manas, M. (3.4) 73 Morgan, B.P. (3.4) 189; (3.6) 167 Mori, A. (3.2) 160 Mori, Y. (1) 142, 442 Morii, M. (1) 376 Morinaka, A . (3.6) 39 Morisaki, M. (3.7) 67 Morishima, Y. (1) 269; (4) 225; (5) 148 Morishita, K. (4) 198 Morita, M. (1) 83 Morita, S. (3.3) 34 Moriyama, H. (5) 80 Morizur, J.P. (3.1) 15 Morley, C.P. (2.2) 48 Moroi, R. (3.2) 41 Moroni, M. (3.4) 188: (3.6) 65 Morrison, C.L. (2.1) 23; (5) 172, 206 Morrow, T. (2.3) 32 Morse, D.L. (2.2) 42 Morse, K.W. (2.2) 135; (3.3) 102; (5) 44 Mortezaei, R. (3.1) 4 3 ; (3.2) 62 Morton, C.E. (2.2) 40 Morton, G.H. (3.2) 25 Morton, J.R. (2.2) 123 Mos, G.H.M. (3.3) 8 2 Mosetti, F. (1) 227 Moshenberg, R. (3.6) 86 Moskovkin, A.S. (2.1) 133 Motherwell, W.B. (3.1) 24; (3.4) 129 Motohashi, K. (4) 375 Motyka, L.A. (3.3) 49; (3.4) 14 Mourmamode, A. (3.4) 132 Mozzanega, M.N. (5) 175 Msayib, K . J . (4) 318 Muller, E.P. (3.2) 58; (3.6) 53 Muller, H.K, (4) 387, 392 Muller, U. (3.6) 4; (4) 24 Muller, W. (1) 407 Muller-Remmers, P.L. (3.7) 3 Mugmer, J. (1) 260 Mugnier, J. (5) 243 Mujashita, T. (4) 231 Mukai, C. (3.6) 33 Mukai, T. (3.3) 44, 45,

577

Author Index Nagorski, H. (2.2) 16, 89 Naguib, M.A.Y. ( 4 ) 446 Nagy, R. (1) 347 Nahor, G.S. ( 2 . 1 ) 230 Nahr, U. (3.7) 36 Naikenova, G.P. ( 4 ) 350 Nair, P.M. (3.3) 142; ( 3 . 4 ) 149; ( 3 . 7 ) 173 Nair, V. (3.4) 102; (3.7) 170, 171 N a i t o , S. ( 2 . 1 ) 32; (5) 189 N a i t o , T. (3.2) 41; (3.4) 136, 137; ( 3 . 6 ) 31, 32, 34, 9 0 Nakadaira, Y. (3.6) 204 Nakagaki, M. ( 3 . 5 ) 136 Nakagaki, R. (1) 191; ( 3 . 4 ) 59-61, 63, 178; (3.5) 2 3 Nakagawa, H. ( 3 . 5 ) 131 Nakagawa, K. ( 4 ) 115 Nakagawa, Y. ( 3 . 6 ) 145 Nakahima, N. ( 3 . 6 ) 1 2 3 Nakahira, T. (3.5) 25 Nakai, H. (3.2) 142; ( 3 . 6 ) 82 Nakajima, N. ( 3 . 2 ) 53, 54 Nakamura, A. ( 2 . 3 ) 16; ( 3 . 4 ) 172; (3.6) 207 Nakamura, H. (3.3) 6 8 Nakamura, J . ( 2 . 1 ) 163; (3.4) 62 Nakamura, K. ( 3 . 3 ) 109; ( 4 ) 451 Nakamura, S. ( 3 . 4 ) 6 3 ; ( 3 . 6 ) i5 Nakamura , ( 1 ) 83; ( 2 . 2 ) 39 N a k a n i s h i , H. (3.4) 186 Nakanishi, S. ( 4 ) 451 Nakao, R . 2.3) 28; (3.6) 203 Nakashima, M. ( 3 . 6 ) 15 Nadtochenko, V . A . ( 3 . 5 ) Nakashima, N. ( 1 ) 234, 33; ( 5 ) 143 319, 444 ( 3 . 3 ) 28 Nagagawa, K. ( 5 ) 199 Nagai, Y. ( 2 . 3 ) 27; ( 3 . 6 ) Nakashima. Y. ( 4 ) 157 197 Nakashira; T. ( 5 ) 194 Nagakura, S. ( 1 ) 191; Nakayama, T. ( 1 ) 189 , ( 3 . 4 ) 6 2 , 178; (3.5) 23 190; ( 3 . 4 ) 83 Nagamura, T. (5) 139, 156 Nakazawa, N. ( 1 ) 215 Nakazawa, T. ( 1 ) 103, 442 Nagarajan, S. (3.5) 115 Nagarajan, V. (1) 223, N a l l y , J. ( 3 . 2 ) 130; 231, 232 ( 3 . 7 ) 109 Naman, S.A. ( 2 . 1 ) 37; ( 5 ) Nagase, S. ( 2 . 2 ) 29 28, 221 Nagata, A . ( 4 ) 152 Namasivayan, C. ( 2 . 1 ) 45 Nagata, M. ( 3 . 2 ) 92; Nanjundiah, B.S. ( 3 . 3 ) (3.6) 18 Nagata, Y. ( 2 . 3 ) 28 33, 142, 144; ( 3 . 4 ) Nagaya, S. ( 4 ) 303 149; (3.7) 173-175 Nagishiwara Rao, B. (1) Naqvi, M.K. ( 4 ) 385 455 N a i i a n , M. ( 3 . 2 ) 138

124; (3.6) 104 Mukakami, S. (3.6) 196 Mukerjee, S.K. (3.3) 31, 32 Mulazzani, Q.G. ( 2 . 1 ) 104, 142 Mullakhmetov, I . N . ( 4 ) 282 Muller, F.W. ( 4 ) 196, 255 M u l l i n , J.L. ( 4 ) 207 Munro, H.S. ( 4 ) 309 Munuera, G. ( 5 ) 166 Murai, H. ( 1 ) 460 Murakami, S. (2.3) 29 Murakami, Y. ( 2 . 1 ) 39; ( 4 ) 449 Muraki, H. ( 2 . 1 ) 35 Muramatsu, S. (3.6) 147 Murata, I. ( 1 ) 103 Murata, S. (3.7) 92; ( 5 ) 174, 185 Murphy, W.R. (2.1) 129; ( 5 ) 60 Murray, R.W. ( 5 ) 157 Murray, S. (3.6) 7 3 Murtaza, 2. (2.1) 5 9 Murty, B.A.R.C. ( 3 . 2 ) 124 Muruyama, K. ( 3 . 4 ) 50; (4) 388 Musci, G. ( 1 ) 353 Musso, H. ( 3 . 2 ) 128 Mustafeva, S.K. ( 4 ) 423 Mustroph, H. ( 4 ) 443 Mutai, K. ( 1 ) 191; (3.4) 59-63 Mutoh, A. ( 4 ) 281 Muzart, J. ( 2 . 2 ) 128; (2.3) 9 ; (3.1) 43; (3.2) 62 Myasnikov, I.A. ( 5 ) 200, 208

.

N a r i n , T. (3.5) 79 Narula, C.K. (3.6) 217 Nasimento, M.G. ( 4 ) 356 N a t a r a j a n , L.V. (1) 312 N a t a r a j a n , P. (1) 268 Natsukamo, K. ( 4 ) 449 Naumann, A. (3.5) 116 Naumer, R. (2.2) 24 Navarro, J.A. (5) 1 2 Navio, A. (5) 166 Nayak, P.L. ( 4 ) 43, 110 Nayak, U.R. (3.1) 20 Nayaya, H. (5) 190 Nazran, A.S. (3.7) 48, 49 Nazuka, R. ( 4 ) 302 Neckers, D.C. (1) 478, 482; ( 3 . 5 ) 56, 59; ( 4 ) 357, 358 Neef, G. ( 3 . 1 ) 16 Nefedov, O.M. (3.7) 5 Nehrings, A. ( 3 . 1 ) 50 Neier, R . (3.2) 133 Nemeth, E.F. (1) 408 Nenkov, G. ( 4 ) 353 Neta, P. ( 2 . 1 ) 160, 240; ( 5 ) 113, 115 N e t t o - F e r r e i r a , J.C. ( 1 ) 451, 459 N e u r e i t e r , M. (1) 210 Newhouse, E . I . ( 4 ) 199 Ngai, R. ( 2 . 1 ) 169 Ngata, Y. (3.6) 203 Nguyen, M.T. (3.7) 8 4 Nguyen, T.L. ( 4 ) 311 N i c h o l l s , C.H. ( 4 ) 440 N i c k o l ' s k i i , V.G. ( 4 ) 287 N i e l s e n , P.E. ( 3 . 2 ) 101 N i g a z i , F.F. ( 4 ) 428 N i i k u r a , H. ( 4 ) 57 N i i n i s t o , L. ( 2 . 1 ) 215 N i i r a n e n , J . (3.7) 176 Niizuma, S. (3.6) 60 N i k i t a e v , A.T. ( 2 . 2 ) 133 N i k i t i n a , G.N. ( 2 . 1 ) 55 Nikogosyan, D.N. ( 1 ) 392 Nikolaev, V . A . ( 3 . 7 ) 76 Nikolov, P. ( 1 ) 126 Nikol'skii, A.B. (2.1) 193 Niles, W.D. (1) 403 Ninayawa, A. ( 4 ) 409 Ninomiya, I. (3.4) 136, 137; ( 3 . 6 ) 31, 3 2 , 3 4 N i s h i b a t a , Y. ( 3 . 6 ) 183 N i s h i d a , A. ( 3 . 6 ) 1 4 ; ( 3 . 6 ) 154 N i s h i d a , S. ( 2 . 1 ) 101, 105, 1 2 3 N i s h i g u c h i , Y. ( 3 . 4 ) 137 N i s h i j i m a , Y. (1) 263; ( 3 . 3 ) 120; ( 3 . 6 ) 9 2 ; ( 4 ) 234

578 Nishikubo, T. ( 4 ) 57, 146, 148 Nishimoto, S. (3.5) 44; ( 4 ) 372; ( 5 ) 181, 182 Nishimura, N. ( 1 ) 83; (3.3) 7 ; (3.6) 9 Nishio, T. (3.2) 53, 54; (3.6) 123, 182 Nittono, T. ( 3 . 3 ) 45 Nivorozhkin, L.E. (3.6) 41 Nixdorf, M. ( 3 . 3 ) 74 Nixon, E.R. (2.1) 69 Nizova, G.V. (2.2) 132, 133 Nobbs, J.H. ( 4 ) 164 Nobudsada, N. (3.3) 7 Nobuhara, H. (3.3) 34; (3.6) 136 Noda, H. (2.2) 49-51, 59 Noda, K. ( 3 . 3 ) 10 Noda, M. ( 4 ) 451 Noe, L.J. ( 1 ) 233 Noel, C. ( 4 ) 195 Noel, S. ( 4 ) 291 Noerdin, H. (3.3) 39; (3.7) 142 Noeth, H. (3.6) 217 Noguchi, K. (3.5) 127 Nohara, M. ( 3 . 2 ) 13 Nohira, H. ( 3 . 3 ) 118 Nomura, M. ( 4 ) 432 Nonaka, T. ( 4 ) 122 Noomen, A . ( 4 ) 140 Norden, B. ( 3 . 2 ) 101 Norin, T. (3.3) 84; (3.4) 10 Norinder, U. (3.3) 30 N o r r i s , R.K. (3.7) 156 N o r t h c o t t , D.J. (3.7) 49 Nosaka, Y. (2.1) 235; ( 5 ) 150 Noth, D. (1) 133 Nouchi, G. (1) 162 Nourmamode, A. (3.3) 90 Nowaezyk, K. ( 1 ) 456 Nowakowska, M. ( 4 ) 338340, 415 Nozakura, S. ( 1 ) 269; ( 4 ) 225, 233; ( 5 ) 148, 152 Nunn, D.S. ( 3 . 2 ) 37 Nurmukhametov, R.N. ( 4 ) 437 NUSS, M.C. (1) 378 Oba, K. (1) 35 Obata, K. (3.5) 131 O'Connor, D.V. ( 1 ) 26 O'Connor, L.H. (2.1) 213 Oda, G. ( 4 ) 450 Oda, K. (3.2) 145, 151;

Author Index (3.6) 114, 179, 181, 183, 184, 186 Oda, M. (3.2) 29-31; (3.6) 218 Odaira, Y. (3.2) 23; (3.4) 3 O'Donnell, J.H. ( 4 ) 361 O'Donnell, P.S. (1) 343 Oertel, U. ( 4 ) 40, 47 O e s t e r h e l t , D. ( 1 ) 378 Oevering, H. (5) 134 Offen, H.W. (1) 294; ( 2 . 1 ) 83 Ogasawara, H. (3.4) 147; ( 3 . 7 ) 143 Ogata, K. (3.2) 8 3 Ogawa, T. (3.2) 136, 143; (3.6) 113, 117 Ogiwara, T. (1) 131; ( 4 ) 42 Ogneva, T.M. ( 4 ) 414 Ogoshi, H. (2.2) 117 Ogura, K. ( 5 ) 233 Ohama, Y. (2.2) 104 Ohashi, M. (3.4) 1 5 ; (3.6) 106, 145; ( 3 . 7 ) 127 Ohashi, Y. (2.1) 163 Ohga, K. (3.3) 34; (3.6) 136 Ohgo, Y. (2.2) 111 Ohjura, K. (3.7) 147 Ohkawa, K. (2.1) 25; ( 5 ) 116 Ohkubo, K. ( 2 . 1 ) 144, 145, 186 Ohkura, K . ( 3 . 2 ) 91; (3.4) 95, 96; (3.7) 148, 152 Ohno, K. (3.6) 179 Ohno, M. ( 1 ) 388 Ohno, 0. (2.1) 228 Ohno, T. (2.1) 156, 157; ( 5 ) 148 Ohnota, M. (3.2) 134; (3.6) 77 Ohsaku, M. (3.3) 121 Ohsawa, H. ( 4 ) 396 Ohsawa, K. ( 4 ) 281 Ohsawa, M. ( 4 ) 231 Ohta, K . ( 4 ) 1, 2 , 6 , 7 Ohta, N. ( 1 ) 300 Ohtani, B. ( 4 ) 372; (5) 181, 182 Ohtani, H. ( 1 ) 164; (2.2) 49-51, 59 Ohtsuki, T. (3.3) 130 Ohyashiki, T. ( 1 ) 375 Oikawa, T. (3.5) 76 Oka, K. (2.3) 28; (3.6) 203 Oka, M. (3.2) 121

Okada, K. (2.3) 6; (3.4) 164; (3.6) 218 Okada, Y. (2.1) 181 Okagawa, I. ( 4 ) 451 Okai, M. (5) 199 O k a i s h i , K. (3.2) 16 Okajima, H. (3.2) 135; ( 3 . 6 ) 83 Okajima, S. ( 1 ) 151 Okamoto, K. ( 5 ) 165 Okamoto, M. ( 1 ) 171, 436 Okamoto, T. ( 1 ) 211 Okamoto', Y. (3.3) 10 Okarma, P . J . (3.3) 7 3 Okawa, T. ( 2 . 3 ) 27 Okazaki, H. (3.4) 77 Okazaki, K. (3.6) 197 Okazaki, M. (3.5) 24 Okeda, Y. ( 3 . 7 ) 127 Okubo, T. (4) 115 Okuda, T. (3.3) 117 Okuno, Y. (3.5) 54 Okura, I . (2.1) 231-233; ( 3 . 5 ) 34; (5) 6 6 , 68, 8 9 , 90, 94, 95, 140 Olah, G.A. (3.7) 41 Olaj, O.F. ( 4 ) 67 Olba, A. ( 1 ) 318 O l b r i c h , G. ( 1 ) 126 Olea, A. ( 1 ) 291, 458 Olenin, A.V. ( 4 ) 118, 119 O l i n s , D.E. ( 1 ) 394 Olken, M.M. (2.1) 217 O l l i n o , M. (2.1) 8 4 , 86 O l l i v o n , M. ( 1 ) 399 Olsen, R.J. (3.4) 112 Omata, M. (2.2) 83; (5) 77 Omata, Y. ( 1 ) 357 Omishi, Y. ( 4 ) 37 Omkaram, N. (3.1) 32, 34, 36 Omote, Y. (3.1) 37; (3.2) 53, 5 4 , 123, 134; (3.3) 3 ; ( 3 . 6 ) 77, 78, 123, 182, 187, 188 Ondrias, M.R. (1) 367 O n i s h i , M. ( 2 . 2 ) 104 Onishi, T. ( 2 . 1 ) 33; ( 5 ) 25, 27, 190 O n i s h i , Y. ( 4 ) 126 Onuki, S. ( 1 ) 270 Ooms, P.H.J. ( 3 . 6 ) 178 Op den Brouw, P.M. (3.3) 88 O p i t z , R . J . (3.3) 147, 148; (3.4) 18, 19; (3.7) 179, 180 Opnya, V . Y a . ( 4 ) 370 Oppenlander , T. (3.3) 128, 129; ( 3 . 7 ) 17, 27 O r , Y.S. ( 3 . 3 ) 108

579

Author Index Oraevsky, A.A. ( 1 ) 392 Orahovats, A.S. ( 3 . 2 ) 6 8 ;

Pac, C . ( 2 . 1 ) 126; ( 3 . 3 )

130; ( 3 . 4 ) 5 5 ; ( 3 . 5 ) 53; ( 3 . 6 ) 131 ( 3 . 4 ) 182 Paci, M. ( 4 ) 215 Ordsmith, N.H.R. ( 3 . 2 ) Packard, B.S. ( 1 ) 276 130; ( 3 . 7 ) 109 Paczkowski, B. ( 4 ) 358 Orekhovskii, V.S. ( 2 . 1 ) Paczkowski, J. ( 1 ) 482; 188 ( 3 . 5 ) 5 6 , 59; ( 4 ) 144, Orger, B.H. ( 3 . 4 ) 21, 22 357, 358 Orikata, T. ( 4 ) 30, 99 Paczkowski, M.A. ( 3 . 5 ) 22 Orito, K. ( 3 . 7 ) 185 Paddon-Row, M.N. ( 5 ) 134 Orlandi, G. ( 1 ) 81 Orlic-Nuber, M. ( 3 . 4 ) 143 Padmanabhan, K. ( 3 . 4 ) 153 Padwa, A. ( 3 . 4 ) 131; Orlowska, B. ( 3 . 1 ) 5 5 ; ( 3 . 7 ) 29, 40 ( 3 . 7 ) 107 Paik, Y.H. ( 5 ) 149 Orpen, A.G. ( 2 . 2 ) 40 Paillous, N. ( 3 . 4 ) 9 3 ; Ors, J . A . ( 1 ) 262 ( 3 . 6 ) 103 Ortega, A. ( 3 . 2 ) 49 Ortega, J.J. ( 4 ) 321, 424 Pak, C.S. ( 4 ) 279 Palmer, T.F. ( 1 ) 102, 428 Ortigosa, K. ( 2 . 2 ) 109 Palmisano, G. ( 3 . 2 ) 64 Ortiz, J . V . ( 2 . 3 ) 40 Ortiz, M.J. ( 3 . 2 ) 7 7 , 7 8 ; Palomino, E. ( 3 . 5 ) 113 Pan, J. ( 4 ) 107, 398, 421 ( 3 . 3 ) 7 2 ; ( 3 . 6 ) 27, 47 Panattoni, M. ( 4 ) 213 Ortmann, W. ( 3 . 7 ) 82 Pancatelli, G. ( 3 . 4 ) 97 Osa, T. ( 4 ) 170 Pancry, P.J. ( 4 ) 361 Osawa, Z. ( 4 ) 184, 422 P m d e y , B. ( 3 . 2 ) 88 Osborne, J . H . ( 2 . 1 ) 165 Panicheva, M.V. ( 2 . 2 ) Osella, D. ( 2 . 2 ) 99 Panse, M.D. ( 3 . 3 ) 33, Oshima, S. ( 1 ) 491 144 Oshima, T. ( 3 . 1 ) 48 Panse, M.D. ( 3 . 3 ) 3 3 ; Oskam, A. ( 2 . 2 ) 4 5 , 5 7 , ( 3 . 7 ) 174, 175 58 Pantar, A.V. (1) 336 Osman, A.H. ( 2 . 1 ) 5 Panzone, G. ' ( 3 . 5 ) 119 Osselton, E.M. ( 3 . 4 ) 2 8 , Paoli, M.A. ( 4 ) 114 31, 34 Paonessa, R.S. ( 2 . 2 ) Osterhoff, P. ( 4 ) 77 Papaconstantinou, E. Ostrikova, V.N. ( 2 . 2 ) 37 ( 2 . 1 ) 6 5 ; ( 5 ) 108 Osuka, A. ( 3 . 2 ) 161, 162 Paparian, S. (3.1) 46 O'Sullivan, A. ( 3 . 2 ) 5 6 ; ( 3 . 4 ) 155; ( 3 . 5 ) 15 ( 3 . 7 ) 137 Papendicik, U. ( 4 ) 196 Otsu, T. ( 4 ) 5 8 , 62 Papier, E. ( 5 ) 204 Otsubo, T. ( 3 . 4 ) 166 Papkov, S.P. ( 4 ) 414 Otsuji, Y. ( 2 . 3 ) 1 0 ; Papp, S . ( 1 ) 347; 372; ( 3 . 3 ) 126; ( 3 . 4 ) 7 4 , ( 2 . 1 ) 187, 190; ( 5 ) 31 7 5 ; ( 3 . 5 ) 103, 106, Pappas, S.P. ( 4 ) 33 107; ( 3 . 6 ) 209; ( 5 ) 47 Paquette, L.A. ( 3 . 3 ) 4 7 , Otsuki, N. ( 3 . 5 ) 44 91, 109, 110; ( 3 . 6 ) 50 Otsuki, T. ( 3 . 2 ) 163 Pardee, J . D . ( 1 ) 406 Ottenbrite, R.M. ( 4 ) 65 Parenti, R.A. ( 1 ) 277 Otterburn, M.S. ( 4 ) 124, Paris, J. ( 5 ) 222 125 Parish, R.V. ( 2 . 1 ) 66 Ottolenghi, M. ( 1 ) 310, Park, C.-H. ( 1 ) 100 31 1 Park, J.M. ( 3 . 7 ) 49 Otvos, J.W. ( 5 ) 145 Park, J.W. ( 5 ) 149 Oucharenko, V.V. ( 4 ) 369 Park, K.K. ( 2 . 1 ) 208 Ounsworth, J. ( 3 . 1 ) 38 Park, S.K. ( 3 . 3 ) 35; Overum, T. ( 4 ) 77 ( 3 . 6 ) 89 Owen, E.D. ( 4 ) 318 Park, S.-M. (1) 100, 387 Owens, P.A. ( 2 . 2 ) 110 Park, Y.T. ( 1 ) 327; ( 3 . 4 ) Owers, R . J . ( 3 . 4 ) 54 144, 183; ( 3 . 6 ) 45 Oxman, J . D . ( 3 . 4 ) 6 4 ; Parkinson, A. ( 4 ) 416 ( 3 . 6 ) 74 Parmar, S . S . ( 1 ) 428 Ozaki, Y. ( 3 . 7 ) 53

Parmon, V.N. Parris, P.E. Parshin, G.S. Parsons, B . J .

( 5 ) 107, 210 ( 1 ) 247 ( 2 . 1 ) 249 ( 3 . 5 ) 130;

( 3 . 7 ) 172

Pasman, P. ( 1 ) 176; ( 5 ) 125

Pasquato, L. ( 3 . 6 ) 171 Pasynskii, A.A. ( 2 . 2 ) 37 Paszyc, S. ( 1 ) 384 Patel, D . I . ( 3 . 7 ) 95 Patharakorn, S . ( 3 . 2 ) 126; ( 3 . 4 ) 141

Patonay, G. ( 1 ) 62 Patterson, F.G. ( 1 ) 438 Patterson, L.K. ( 1 ) 31, 38 1

Paulsen, H. ( 1 ) 397 Paulus, E.F. ( 3 . 2 ) 103 Pavker, F. ( 1 ) 37 Pavlik, J.W. ( 3 . 3 ) 8 3 ; (3.4) 9

Pavlopoulos, T.G. ( 1 ) 431 Pavlov, N.N. ( 4 ) 350 Pavlovski, V . I . ( 2 . 1 ) 139 Peacock, J . A . ( 3 . 6 ) 144 Peak, D. ( 1 ) 331 Pearce, E.M. ( 4 ) 360 Pearson, C.J. ( 3 . 7 ) 77 Pearson, K.H. ( 2 . 1 ) 213 Pedulli, G . F . ( 2 . 3 ) 1 8 ; ( 3 . 2 ) 158

Peirigua, A. ( 1 ) 162 Pekcan, 0. ( 4 ) 248 Pelizzetti, E. ( 2 . 1 ) 2 2 , 178; ( 5 ) 9 , 211, 212

Pelizzi, G. ( 3 . 5 ) 119 Pellerean, B. ( 4 ) 310 Penenory, A.B. ( 3 . 7 ) 161 Penico, A. ( 4 ) 267 Penigault, E. ( 2 . 1 ) 180 Pereira,, V.R. ( 1 ) 257 Pereira, L.C. ( 1 ) 145 Peretti, J. ( 2 . 1 ) 77 Perez-Ossorio, R. ( 3 . 2 ) 75-78; ( 3 . 3 ) 4 1 , 4 2 , 7 2 ; ( 3 . 4 ) 1 3 ; ( 3 . 6 ) 27, 46-48, 79 Perez-Ruiz, T. ( 3 . 5 ) 126 Perichet, G. ( 1 ) 383; ( 2 . 1 ) 246 Perry, D.A. ( 3 . 7 ) 121 Perry, D.L. ( 2 . 1 ) 215 Persy, G. ( 1 ) 103 Perumattarn, J. ( 3 . 2 ) 35 Perutz, R.N. ( 1 ) 7 8 ; ( 2 . 2 ) 8 , 17 Peruyenlova, D.G. ( 4 ) 455 Pestanov, V.Yu. ( 2 . 3 ) 36 Pete, J.-P. ( 2 . 2 ) 128; ( 2 . 3 ) 9 ; ( 3 . 1 ) 43; ( 3 . 2 ) 55, 6 2 ; ( 3 . 5 ) 46-

580 256 Rao, D.N. ( 1 ) 483 Rao, K.K. (5) 187 Rao, M.V.R. ( 1 ) 336 Rao, V.B. ( 3 . 2 ) 2 , 1 7 Rao, V.P. ( 1 ) 473; (3.5) 150; ( 3 . 6 ) 177; (3.7) 128 Rapley, P.A. ( 3 . 2 ) 149, 150; (3.6) 180, 185, 189 Rappan, M. ( 4 ) 341 Rappoldt, P.M. ( 3 . 3 ) 8 2 Rau, H. ( 2 . 1 ) 113; ( 5 ) 142 Raabe, G. ( 2 . 3 ) 13; ( 3 . 7 ) Raucher, S. ( 3 . 7 ) 145 88 Rabani, J. ( 2 . 1 ) 117-119, Rauhut, M. ( 4 ) 405, 416 166, 167, 230; ( 5 ) 146, Rausch, M.D. ( 2 . 2 ) 9, 54 R a w a l , V.H. ( 3 . 4 ) 122147 124; ( 3 . 6 ) 25 Rabek, J.F. ( 4 ) 11, 181, Razuvaev, G.A. ( 3 . 5 ) 28 316, 319, 406, 427 Reber, J.F. ( 5 ) 213 Raby, P. ( 1 ) 420 Raghuraman, T.S. ( 3 . 2 ) Reddoch, A.H. ( 3 . 7 ) 49 Reddy, A.R. (1) 199 71; ( 3 . 4 ) 179 Redmond, R.W. (1) 480 Rahrnan, A.N. ( 5 ) 240 Redpath, A.E. ( 3 . 4 ) 152; R a i n e s , D.E. ( 2 . 1 ) 112 (3.5) 17 Rakunov, Yu.P. ( 4 ) 129 Redwine, O.D. ( 1 ) 502 Raldugin, V.A. ( 3 . 5 ) 85 Ram, A. ( 4 ) 349 Reed, J.L. ( 2 . 1 ) 169 Ramachandran, P.V. ( 3 . 7 ) Reedich, D.E. ( 3 . 4 ) 3 3 ; ( 3 . 7 ) 20, 103 108 Ramaiah, D. (3.3) 135; R e e n t s , W.D. ( 2 . 2 ) 10 Rees, C.W. ( 3 . 6 ) 166; (3.7) 136 ( 3 . 7 ) 32-34, 9 8 , 99 Ramakrishna, V.T. ( 3 . 4 ) R e g i t z , M. ( 3 . 6 ) 21 181 Rehak, V. ( 1 ) 303 Ramamurthy, V. (1) 301, Rehm, D. ( 3 . 2 ) 103 455, 473; ( 3 . 1 ) 4 ; Rehms, A.A. ( 1 ) 324 (3.2) 43, 45; (3.4) Rehorek, D. ( 2 . 1 ) 245 153; ( 3 . 5 ) 1, 3 , 150; Reichenbaecher, M. ( 3 . 3 ) (3.6) 176, 177, 190, 191; ( 3 . 7 ) 128; ( 5 ) 10 79 Reimann, B. ( 2 . 3 ) 8 Ramanan, S.V. ( 1 ) 410 Ramaraj, R. (1) 268 R e i n h a r d t , G. ( 3 . 3 ) 139; Ramasubbu, N . ( 3 . 2 ) 4 3 , ( 4 ) 413 R e i n i s c h , G. ( 4 ) 208 45 Reinking, M.K. (2.2) 125 Ramazemova, M.R. ( 4 ) 249 R e i s e n a u e r , H.P. ( 3 . 2 ) Ramesh, V . ( 1 ) 301; ( 5 ) 159 10 R e i s f e l d , R. ( 2 . 1 ) 199; Ramey, C.E. ( 4 ) 400 (5) 241, 242 Ramnath, N. ( 1 ) 301; Rejnek, J. ( 2 . 3 ) 45 (3.1) 32; (5) 10 Rembold, M. ( 4 ) 402 Ramos, A. ( 3 . 6 ) 79 Rempp, P. ( 4 ) 237 Ramos, E.L. ( 3 . 7 ) 56 Remuson, R. ( 3 . 5 ) 141 Rampi, M.A. (2.1) 92 R e n d a l l , W.A. ( 3 . 4 ) 4-6; Ramsay, P.J. ( 4 ) 224 Ranade, A.C. (2.2) 136 ( 3 . 6 ) 164; ( 4 ) 251 Renge, I . V . ( 1 ) 471 Ranby, B. ( 4 ) 38, 316, 319, 406, 427 Renneke, R.F. (5) 111 Rentsch, S.K. ( 1 ) 241; Randolph, C.L. ( 2 . 2 ) 92 ( 4 ) 441 Raneeze, D. ( 4 ) 420 Ranganathan, D. ( 3 . 7 ) 108 R e n t z e p i s , P.H. ( 1 ) 14, Rangel-Zamudia, L . I . ( 1 ) 9 8 , 9 9 , 120, 138, 156,

Qin, Q. ( 2 . 1 ) 225 Quanten, E. (1) 201 Quast, H. ( 3 . 7 ) 36, 86 Quay, S.C. ( 1 ) 337, 341 Q u e s l e l , J . P . ( 4 ) 270 Qui, L. ( 2 . 1 ) 223 Quinga, E.M.Y. ( 1 ) 503 Q u i n k e r t , G. ( 3 . 2 ) 103, 104 Quintero-Cortes, L. ( 3 . 7 ) 168 Q u i t e v i s , E.L. ( 1 ) 123

Author Index 172 Rest, A.J. (2.2) 70 R e t t i g , S . J . ( 2 . 2 ) 121 R e t t i g , W. (1) 93, 174, 184, 265; (2.1) 81 R e v e r t e , J.M.A. (1) 317 R e v i n s k i i , Yu.V. ( 2 . 1 ) 188 Rey, P. ( 2 . 2 ) 75 Reynolds, D.W. (3.3) 67 R i a h i , A. ( 2 . 2 ) 128; (2.3) 9 R i c a r d , R. ( 3 . 2 ) 59; (3.5) 12 Ricci, A . ( 2 . 3 ) 18 Rice, J . A . ( 2 . 3 ) 53 R i c e v u t o , V. ( 2 . 2 ) 126 Richardson, F.S. (1) 59 R i c h e r t , R. (1) 449 Richman, R.M. ( 2 . 1 ) 76 Richoux, M.C. ( 2 . 1 ) 240, 247; ( 5 ) 113, 115 R i c h t e r , P. ( 4 ) 453 R i d e r , E.S. ( 4 ) 56 Ridge, D.P. (2.2) 10 R i e d e , J . ( 2 . 2 ) 22 R i e g e r , P.T. (2.1) 112 R i e g l e r , M. ( 4 ) 189 K i e h l , J.P. ( 1 ) 59, 250 R i e k e r , J. ( 1 ) 210 Riepponen, P. ( 3 . 7 ) 102 R i f f a u d , M.-H. (3.4) 173 R i g h e t t o , L. ( 4 ) 113 R i g l e r , R. (1) 30 R i h s , G. ( 3 . 7 ) 2 5 R i m a , J. ( 1 ) 106 R i n g s d o r f , H. ( 3 . 6 ) 70 Rinke, M. ( I ) 194, 195 R i v a s , C. ( 3 . 1 ) 45; ( 3 . 4 46; (3.5) 14 R i v a t o n , A. ( 4 ) 298, 348 R i v e r a , S. ( 2 . 1 ) 210 R i v e r s , D.S. ( 2 . 1 ) 76 Rives-Arnau, V. (2.1) 36 (5) 166 Rizzo, T.R. ( ) 327 Robbins, D . J . ( 1 ) 344 Roberge, P.C. (2.1) 6 3 Robert, B. ( 2 1 ) 53, 54 Robert-Nicoud M. ( 1 ) 7 3 R o b e r t s , A . J. ( 4 ) 165 R o b e r t s , S.M. (3.1) 30 Robins, M.J. 3 . 4 ) 57; ( 3 . 6 ) 127 Robinson, G.W. ( 1 ) 183, 222 Robles Diaz, R. (3.5) 101 Robson, N.S. (3.4) 42 ROCCO, V.P. ( 3 . 2 ) 3 Roche, G. ( 4 ) 305 Rodewald, H. (3.3) 76 Rodewald, W.J. ( 3 . 3 ) 80

58 1

Author Index

48 Peteanu, L.A. (1) 327 Peteres, K. (3.1) 14 Peters, A.W. (4) 229 Peters, E.-M. (3.1) 14; (3.2) 86; (3.3) 43, 92; (3.5) 77; (3.7) 18, 24 Peters, K. (3.2) 86; (3.3) 43, 92; (3.5) 77; (3.7) 18, 24 Peters, K.S. (1) 152, 187, 501 Petersen, J.D. (2.1) 129, 155; (5) 60 Petersen, J . L . (2.2) 6 Peterson, D.B. (5) 17 Peterson, J.R. (2.1) 177 Peterson, K . A , (4) 222 Peterson, L.K. (2.2) 34 Peterson, M.W. (2.1) 76 Petit, J. (1) 399 Petit-Ramel, M. (1) 383; (2.1) 246 Petrak, K.L. (4) 29 Petrenko, N.I. (3.5) 120 Petrich, J . W . (1) 20 Petrin, M. (1) 488 Petrov, G. (4) 109 Petter, W. (3.1) 35; (3.7) 135 Pettit, T.L. (2.1) 96 Pfeifer, D. (3.7) 83 Pfleiderer, G.P. (1) 349 Pfleiderer, W. (3.6) 192, 193 Pfoertner, K.-H. (3.6) 51, 52 Phaff, R. (3.1) 35; (3.7) 135 Phifer, J . E . (2.1) 46 Philipart, J.L. (4) 331, 346 Phillips, D. (1) 26, 319; (4) 159, 161 Phillips, G.O. (3.5) 40, 130 Phillips, P. (4) 190 Phillips, R.B. (3.3) 77 Phillips, S.D. (2.1) 162 Phillips, T. (3.3) 138 Phillpot, S.R. (4) 188 Piancatelli, G. (3.4) 98; (3.7) 149, 150 Pichat, P. (5) 162, 175, 204 Pickett, J.E. (4) 368 Pienta, N . J . (3.3) 66; (3.6) 132 Pierini, A.B. (3.7) 161 Pieroni, 0. (3.6) 12, 13 Piers, E. (3.2) 22 Pietra, F.'(3.2) 19

Pietra, S. (3.4) 188; (3.6) 65 Piggott, R.D. (3.2) 126; (3.4) 141 Pileni, M. (5) 141 Pill Soon Song, (1) 413 Pin, N.E. (1) 196 Pina, F. (2.1) 142; (2.2) 35; (5) 99 Pincock, J . A . (3.4) 104 Pinhey, J.T. (3.5) 18 Pinther, P. ( 4 ) 108 Pipe, E. (3.7) 141 Pirogova, N . A . (3.2) 166 Pirrung, M. (3.1) 29 Piserchio, M. (2.3) 11 Pisulina, L.P. (3.2) 168 Piszezek, L. (1) 87 Plachenov, B.T. (2.1) 195 Plato, M. (2.1) 41 Platz, M.S. (3.7) 47, 51, 54, 55, 90 Pleskov, Yu.V. (5) 227 Plyusnin, V.F. (2.1) 191 Podoplelov, A.V. (2.3) 54 Pohl, S. (2.3) 23; (3.6) 195 Polansky, O.E. (1) 126 Polewski, K. (3.5) 68 Poliakoff, M. (2.2) 14, 95, 98 Polinski, A.S. (4) 204 Politi, M.J. (1) 292 Polo, J.S. (3.7) 110 Polokoff, M.A. (1) 401 Poluektov, N.S. (2.1) 214 Polyakov, N.E. (3.5) 6 Polyanina, N . A . (4) 429 Pommier, B. (2.1) 26 Ponder, M. (1) 168 Ponomarev, O.A. (3.2) 44 Ponticelli, F. (3.2) 39; (3.6) 56, 88, 125 Popisil, J. (4) 289 Popovitz-Biro, R. (3.1) 10, 11 Porai-Koshits, M.A. (2.2) 37 Port, H. (1) 115, 255 Porte, A.L. (3.6) 144 Portella, C. (3.2) 55; (3.5) 45-48 Postnikov, L.M. (4) 332, 333, 401, 431 Potapov, I . A . (5) 114 Potier, P. (3.7) 113, 117 Potocnak, J. (4) 443 Pottel, H. (1) 48 Pottier, R. (1) 417 Potziger, P. ( 2 . 3 ) 8 Pouaet. - . J. (5) 243 Pouligny, B; (1) 286

Pouliquen, J. (1) 94; (4) 444 Pouyet, B. (1) 383; (2.1) 246 Povazzaneova, M. (4) 403 Powell, M.H.A (2.2) 8 Poznyak, A. L. (2.1) 139, 143 Pradervand, .G 0. (2.1) 196 Pramauro, E. 2.1) 22 Prasad, A.R.S (1) 345, 354 Prasad, D.R. 1) 199; (2.1) 94, 1 2; (5) 85, 86, 92 Prasad, G. (3.5) 113 Prasad, P.N. (1) 483 Pratapan, S. (3.2) 124 Pratt, J.E. (1) 475; (3.5) 105; (4) 261 Pravednikov, A . N (5) 158 Prementine, G.S. (4) 53 Preses, J.M. (1) 82 Presser, D.W. (3 5) 42; (5) 223 Preston, K.F. (2 2) 123 PrevitaLI, C.M. 1) 154, 188, 423, 424, 445 ; (3.4) 85 Prewo, R. (3.2) 68; (3.4) 182 Price, J.D. (3.3) 58 Prieto,,A. (5) 201 Prieto, N.E. (1) 293; ( 4 ) 185, 206 Prignano, A.L. (2.2) 131 Prince, R.C. (5) 15 Prinzbach, H. (3.3) 105, 106, 112, 113; (3.4) 159, 160; (3.6) 100, 105; (3.7) 25 Priola, A . (4) 141 Pritchard, R.B. (4) 435 Pritze, B. (2.3) 48, 49 Procter, G . (3.2) 130; (3.7) 109 Prout, K. (3.2) 10 Pruett, S.R. (3.4) 112 Pshenichnyi, V . N . (3.5) 117 Puaux, J.-P. (1) 192 Puig, S. (3.2) 108 Pulst, M. (4) 442 Purbrick, M.D. (4) 29 Purich, D.L. (1) 355 Pushpa, S . (5) 26 Puthraya, K.H. (2.1) 172 Putnins, E. (5) 229 Pyshchev, A.I. (3.4) 128; (3.6) 29 Pyun, C.-H. (1) 387

Author Index

582 Rodgers, J. ( 1 ) 114 Rodgers, M. (3.3) 145; ( 3 . 7 ) 151 Rodgers, M.A.J. ( 1 ) 74, 474; ( 3 . 5 ) 60 R o d i g h i e r o , G. ( 3 . 2 ) 48 Rodrigo, L. ( 2 . 1 ) 6 3 Rodriguez, F. ( 4 ) 45 Rodriguez, M.S. ( 3 . 7 ) 186 Rodriguez-Hahn, L. (3.2) 49 Rodwell, P.W. ( 3 . 4 ) 45 Roe, D.C. ( 2 . 2 ) 72 R o e l a n d t s , R . ( 1 ) 201 Roesle, A. (3.3) 81 Roewkamp, M. ( 4 ) 329 Roffey, C.G. ( 4 ) 22 Roger, A . ( 4 ) 330 Rogers, E.C. ( 4 ) 311 Rohatgi-Mukerjee, K.K. (1) 463 Rohde, R. (3.1) 16 R o j a s , G.E. (2.1) 4 0 R o j a s , N. ( 4 ) 356 Rol, C. (3.5) 110 R o l i a , P.A. ( 4 ) 76 Roman, E. (2.2) 8 5 Roman Ceba, M. ( 1 ) 124 Romano, S. ( 3 . 3 ) 72; ( 3 . 6 ) 27 Romkina, J. ( 4 ) 77 Roncel, M. (5) 1 2 Rondelez, F. ( 4 ) 228 R o n d i n e l l a , M.A. ( 4 ) 45 ROOS, G. ( 4 ) 128 Rosenberg, A. (1) 347 Rosenfeld, R.N. ( 2 . 2 ) 11 Ross, J.B.A. ( 1 ) 333, 334 Rossbroich, G. ( 1 ) 479 R o s s e t t i , R . (1) 316 R o s s i , R . A . ( 3 . 7 ) 161, 164 Rostch, C . J . ( 4 ) 400 Roth, H.D. ( 1 ) 156; ( 3 . 3 ) 62; ( 5 ) 46 R o u l e t , R. ( 2 . 2 ) 80 R o u n d h i l l , D.M. ( 2 . 2 ) 130 R o u s s e l , P. ( 3 . 5 ) 8 9 R o u s s i , G. (3.7) 168 Rozenkevich, M.B. (5) 100, 114 Rozploch, F. ( 4 ) 322 R t i s h c h e v , N . I . ( 3 . 3 ) 12; (3.6) 216 Rubin, H.D. ( 2 . 2 ) 46 Rubin, M.B. (3.2) 115 Rubtsov, I . V . ( 3 . 5 ) 33; ( 5 ) 143 Rudinskaya, G.V. ( 4 ) 414 Rufs, A . M . ( 3 . 5 ) 9 Ruggeri, R. (3.7) 121 Rughooputh, S.D.D.V. ( 4 )

190 Ruiz-Hitzky, E. ( 2 . 1 ) 137; ( 5 ) 117 Rumbach, T. (3.4) 24 Runkasova, J. ( 1 ) 303 Runov, V.K. (2.1) 136 Runsink, J. ( 3 . 1 ) 50; ( 3 . 4 ) 24 Rusek, M. ( 5 ) 213 R u s h f o r t h , D.S. ( 1 ) 256 R u s l i n g , J.F. (5) 232 R u s s e l l , G.A. ( 3 . 7 ) 159, 160 R u s s e l l , J . C . ( 1 ) 285, 295; ( 3 . 3 ) 23 R u s s e l l , P.M. ( 4 ) 343 R u t t e n s , F. ( 1 ) 330 R u t t e r , A. ( 3 . 2 ) 164 Ruziewicz, Z. ( 1 ) 446 Rychla, L. ( 1 ) 494 S a a , J . M . ( 3 . 4 ) 116 Saad, A.D. (1) 406 S a b i , Z.S. ( 4 ) 9 4 S a c k s , S.L. ( 3 . 2 ) 131; ( 3 . 6 ) 99 S a d o v s k i i , N.A. (1) 148 S a d r i d d i n o v , B.B., ( 4 ) 9 4 Sadvakasova, S.K. ( 2 . 1 ) 136 S a e k i , Y. ( 5 ) 148 Saeva, F.D. ( 3 . 4 ) 189; ( 3 . 6 ) 167 S a f a , K.D. ( 2 . 3 ) 1 9 ; ( 3 . 3 ) 4 ; (3.6) 199 Safarazadeh-Amisi, A. ( 1 ) 160 Sagdeev, R.Z. ( 2 . 3 ) 54; (3.5) 6 Saha, S. ( 3 . 2 ) 113 Sahn, G. ( 4 ) 110 Sahota, R.I.K. (3.5) 43 S a i g o , K . ( 3 . 2 ) 13 S a i t o , I. ( 3 . 2 ) 90; ( 3 . 5 ) 131; ( 3 . 6 ) 147 S a i t o , K. ( 2 . 1 ) 58, 147 S a i t o , Y. ( 2 . 1 ) 5 7 , 161; ( 2 . 2 ) 118, 119; ( 5 ) 6 4 , 75, 80, 81 S a i t o h , K. ( 3 . 6 ) 33 S a i t o v i t c h , E.M.B. ( 2 . 2 ) 69 S a j i , T. ( 2 . 1 ) 35 Sakaguchi, Y. ( 2 . 1 ) 198; ( 2 . 3 ) 55 S a k a i , H. (3.6) 57 S a k a i , M. ( 3 . 5 ) 136 S a k a i t a n i , M. ( 3 . 2 ) 30 S a k a k i , S. ( 2 . 1 ) 186 Sakamoto, K. ( 2 . 3 ) 16; ( 3 . 4 ) 172; ( 3 . 6 ) 207

Sakamoto, M. (3.1) 37; ( 3 . 2 ) 1 2 3 , 134; (3.3) 134; (3.6) 77, 187, 188; (3.7) 132 Sakamoto, S: ( 2 . 1 ) 39 Sakamoto, T. (5) 156 Sakane, F. ( 4 ) 451 S a k a t a , S. (3.5) 24 S a k a t a , Y. ( 3 . 4 ) 158, 166 S a k h a r o v s k i i , Yu.A. ( 5 ) 100, 114 Sakhnovskaya, E.B. ( 4 ) 423 S a k i , H. ( 5 ) 182 Sako, M. ( 3 . 6 ) 62 S a k o t a , N. ( 4 ) 52 S a k u r a g i , H. ( 1 ) 486; ( 3 . 3 ) 13; (3.5) 27, 36 S a k u r a i , H. (2.3) 15, 1 6 ; ( 3 . 3 ) 130; (3.4) 172, 190; ( 3 . 6 ) 201, 202, 204, 207 S a k u r a i , K. ( 2 . 2 ) 117 S a k u r a i , T. (3.4) 184, 185; ( 3 . 6 ) 44, 149 Sakurovs, R. ( 1 ) 52 Salamon, Z. ( 1 ) 272 S a l a z a r , J . A . (3.7) 187 S a l l e t , D. ( 4 ) 330, 348 Salmeen, I. ( 1 ) 411 Salomon, R.G. (3.3) 115, 116 S a l t , W.G. ( 3 . 7 ) 1 6 3 S a l t i e l , J. ( 1 ) 229; ( 3 . 3 ) 9; ( 3 . 4 ) 51 S a l v a d o r i , P. ( 4 ) 220 S a l v e r i d e s , C. ( 4 ) 227 S a l ' v i t o k a y a , L.N. ( 4 ) 455 Samanta, A. ( 1 ) 133 Samat, A. (3.7) 167 Samol, S. ( 4 ) 110 Samotus, A. ( 2 . 1 ) 60 Samuel. E. (2.2) 5 Sanchez, I . Z . (1) 317 Sandarova, S.A. ( 4 ) 410 S a n d e r , W. ( 3 . 7 ) 6 2 , 6 3 S a n d e r s , J.K.M. ( 2 . 1 ) 241; (5) 130 S a n d i s o n , M. ( 3 . 5 ) 113 S a n d r i n i , D. (2.1) 93, 175; ( 5 ) 123 Sandros, K. ( 3 . 3 ) 30; ( 3 . 4 ) 163, 168 S a n f e l i u , E. ( 3 . 4 ) 148 Sano, K. ( 3 . 5 ) 1 2 3 San Roman, E. ( 2 . 3 ) 56 S a n t a m a r i a , J. ( 3 . 5 ) 97 Santhanam, M. ( 2 . 2 ) 129 Sanz, J. ( 5 ) 166 S a r a v a r i , 0. ( 1 ) 506 S a r g e s o n , A.M. (2.1) 4 7 ,

Author Index 110, 141; (5) 97, 98 S a r i y a r , G. (3.2) 109; (3.6) 84 S a r k i s o v , O.M. (2.3) 35, 36 S a r k i s y a n , A.G. (5) 229 S a s a k i , T. (3.6) 37; (4) 272 S a s a k i , Y. (2.1) 57, 58, 147 S a s h i d a , H. (3.7) 94 S a s s e , W.H.F. (1) 297; (2.1) 47, 110, 114, 141; (5) 71, 97, 98 Sassoon, R.E. (1) 10; (2.1) 117-119; (5) 146, 147 S a t a k e , I. (1) 308; (4) 449 S a t o , E. (3.6) 128 S a t o , F. (2.1) 186 S a t o , H. (1) 96; (2.2) 71 S a t o , K. (3.3) 114; (5) 197 S a t o , M. (3.2) 50; (4) 218 S a t o , R. (3.5) 128, 129 S a t o , S. (2.1) 31; (3.4) 15; (5) 183, 184, 192 S a t o , T. (3.4) 77; (3.5) 76; (4) 62 S a t o , Y. (3.2) 142; (3.6) 82, 183 S a t y a n a r a y a n a , N. (3.1) 20 S a u c i e r , A.C. (1) 355 S a u e r , G. (3.1) 16 S a u e r , J. (3.3) 125 Sauvage, J.P. (2.1) 128; (5) 59 Sauvage, P. (3.2) 59; (3.5) 12 S a v i n o , T.G. (3.7) 47, 51 Savinov, E.N. (5) 107, 210 Savinova, E.R. (5) 107 Savory, B. (1) 322 S a v v i n , N.N. (5) 200 Sawada, K. (3.4) 83 Sawaki, Y. (2.1) 21; (3.5) 91 S a w a n i s h i , H . (3.7) 94, 96 Sawyer, W.H. (1) 351 S c a i a n o , J . C . (1 80 419, 451, 459, 461, 465, 484, 498, 499 ; (3.1) 8, 9, 24 26, 39, 40; (3.4) 129, 130, 151; (3.5) 11; (3.7) 54, 58, 59 S c a n d o l a , F. ( 2 . 1 92,

583 178 S c a r l a t t a , S.F. (1) 262 S c a r p a , A. (1) 408 S c e t t r i , A. (3.4) 97, 98; (3.7) 149, 150 Schaap, A.P. (3.5) 113 S c h a d t , M.J. (2.2) 19, 20 S c h a f e r , A. (2.3) 23; (3.6) 195 S c h a f e r , H.J. (3.7) 104106 S c h a e f f e r , C.D. (2.2) 32 S c h a f f n e r , K. (2.2) 15, 73; (3.2) 88 Schanze, K.S. (1) 220; (2.2) 102; (3.4) 51; (5) 70 S c h a r f , G. (1) 425 S c h a r f , H.-D. (3.1) 1, 22, 33, 50; (3.4) 26 Schaumann, E. (3.6) 191 S c h e f f e r , J . R . (3.1) 32, 34, 36, 38; (3.2) 131; (3.6) 99 S c h e l l e r , M.E. (3.3) 70 Schenk, K.-H. (3.2) 112; (3.6) 19 S c h i a v e l l o , M. (5) 5 S c h i e b e r l e , P. (3.7) 140 S c h i r s a , R. (1) 207 S c h i s a n o , M.I. (2.1) 226 S c h i s s e l , D.N. (3.3) 40 Schlimper, R. (4) 154 Schmehl, R . H . (2.1) 80, 84; (5) 57, 136 Schmid, A.A. (1) 119 Schmidt, F. (2.2) 68 Schmidt, J. (1) 422 Schmidt, J.A. (5) 128 Schmidt, K.H. (3.5) 134 Schmidt, R. (3.5) 98 Schmidtberg, G. (3.3) 52, 54, 55 Schmieder, K.R. (3.2) 103 S c h m i t t , U. (3.6) 42 S c h n a b e l , W. (1) 427; (3.6) 213, 214; (3.7) 31, 96, 122, 147 S c h n a t t e r e r , A. (1) 481; (3.5) 102 Schneck, R. (1) 72 Schneckenburger, H. (1) 37 Schoenecker, B. (3.3) 79 S c h o l e s , G. (3.2) 95 S c h o l l , B. (3.6) 101 S c h o l l e r , D. (3.5) 47 S c h o n h i l z e r , P. (3.3) 86 Schoonheydt, R.A. (2.1) 89 Schreckenbach, J. (2.2) 31, 33

Schrock, A.K. (3.7) 46 S c h r o d e r , C. (3.2) 17 Schroeder, F. (1) 320 S c h r o f , W. (1) 115 S c h r o t h , G. (2.2) 4 S c h u b e r t , U. (2.2) 55 Schuchmann, H.P. (3.7) 130 Schuda, A.D. (3.6) 112 S c h u e t z , H. (3.2) 125 Schulman, P.M. (2.2) 44 S c h u l t e - F r o h l i n d e , D. (1) 443; (3.3) 25 S c h u l t e n , K. (1) 57 S c h u l t z , A.G. (3.1) 28; (3.2) 87, 106, 108; (3.6) 43; (3.7) 23 Schumacher, H.J. (2.3) 41 Schumacher, L.C. (5) 230 Schumann, D. (3.5) 116 S c h u s t e , G.B. (3.7) 46, 91 S c h u s t e r , D . I . (1) 500; (3.2) 79, 105, 107 S c h u s t e r , F. (3.3) 125 S c h u s t e r , G.B. (3.4) 76; (3.6) 219; (3.7) 44, 45 Schwan, L.O. (2.1) 8 1 Schwartz, E. (3.7) 121 S c l a f a n i , A. (5) 5 Scopes, D.I.C. (3.7) 95 S c o t t , C.H. (1) 71 S c o t t , G. (4) 381, 408 S c o t t , G.W. (1) 121 S c o t t , T.L. (1) 368 S c o t t , T.W. (1) 367 Scrimgeour, C.M. (3.5) 74 S c r i v e n , E.F.V. (3.7) 95 Scyfong, R. (1) 115 S c y p i n s k i , S. (1) 200 S c z o s t a k , A. (3.3) 92 S e a r s , D.F. (1) 229 S e b a s t i a n i , G.V. (3.5) 110 S e d e l m e i e r , G. (3.3) 112; (3.4) 159 Sedlacek, B. (4) 239 S e d l a k , P. (3.5) 111 S e e g e r , D.E. (4) 363 S e h r o f , W. (1) 255 S e i d l e r , P.F. (2.2) 52 S e i f e r l i n g , B. (3.7) 86 S e i j a s , J . A . (3.4) 116 S e i t z , R.W. (4) 207 S e k i , H. (2.2) 116 S e k i , K. (3.2) 9:; (3.4) 95, 96; (3.7) 147, 148, 152 S e k i , Y. (3.7) 185 S e k i g u c h i , A. (2.3) 20, 22 S e k i n e , T. (2.1) 38

Author Index

584 Sekutowski, J . C . ( 3 . 3 ) 106; ( 3 . 6 ) 100 S e l l i , E. ( 4 ) 105, 113 Semchishen, V . A . ( 2 . 3 ) 46 Semenishin, D . I . ( 2 . 1 ) 6 1 Semerak, S.N. ( 1 ) 266; ( 4 ) 247 Sendyurev, M.V. ( 3 . 6 ) 215 Sengupta, P.K. ( 4 ) 9 3 Sennikov, P . G . ( 2 . 2 ) 27 S e n t a , M. ( 3 . 6 ) 171 S e n t h i l n a t h a n , V.P. ( 1 ) 426; (3.7) 51 S e r a , A. ( 3 . 7 ) 183 Serdobov, M.V. ( 2 . 2 ) 132 Serdyukova, T . I . ( 2 . 1 ) 62 Sergeev, A.D. ( 4 ) 275, 277 S e r i e s , I . ( 1 ) 347 Serpone, N. ( 2 . 1 ) 22, 104, 132; ( 5 ) 211, 212 S e r v a a s , P.C. ( 2 . 2 ) 45 S e s h a d r i , S. ( 4 ) 447 S e s i l e t s , D . J . ( 1 ) 33 S e t o , J . ( 3 . 6 ) 162 S e t s e r , D.W. ( 2 . 3 ) 30 S e t s u n e , J. ( 5 ) 69 S e x t o n , D.A. ( 2 . 1 ) 40 Seymour, P. ( 2 . 1 ) 131 Seymour, R.B. ( 4 ) 391 Shade, J.E. ( 2 . 2 ) 32 S h a f i r o v i c h , V.Ya. ( 5 ) 103, 144 Shagisultanova, G . A . (2.1) 9 1 , 148, 182, 183; ( 2 . 2 ) 108, 109; ( 5 ) 78 Shah; A ( 3 . 2 ) 152; ( 3 . 7 ) 123 S h a k r a , s. ( 4 ) 434 Shamma, M. ( 3 . 2 ) 109, 111; 3.6) 8 4 , 85 Shankar B.K.R. ( 3 . 3 ) 108 Shannon P . J . ( 3 . 6 ) 4 3 Shaphel L. ( 5 ) 170 ShaDiro G. (3.2) 3 S h a i i h a n , H. ' ( 1 ) ~387 Sharma, D.K. (3.5) 10; ( 3 . 6 ) 72 Sharma, P.K. ( 3 . 4 ) 177 Sharma, T.C. ( 3 . 5 ) 9 4 , 95 Sharma, V . K . ( 3 . 5 ) 4 3 S h c h e r b a t s k a , N . V . (1) 278 S h e c h t e r , H . ( 3 . 7 ) 66 S h e l d r i c k , W.S. (2.2) 26 Shelekhov, M.G. (3.4) 174; ( 4 ) 79 Shen, C.C. ( 2 . 2 ) 137 Shen, S. ( 2 . 1 ) 236, 238; ( 3 . 5 ) 19; ( 5 ) 6 7 Shen, W. ( 4 ) 131

Shen, X.A. ( 4 ) 288 S h e p e l i n , E.V. (5) 217 Sheradsky, T. ( 3 . 6 ) 86 S h e r i d a n , R.S. ( 3 . 1 ) 56; ( 3 . 4 ) 32, 33; (3.7) 4 , 6 , 7 , 20, 21, 103 S h e r s t y u k , V.P. (2.1) 55; ( 4 ) 80 Sherwood, A . G . ( 2 . 3 ) 1 2 S h i , H. ( 2 . 1 ) 204 S h i , Q.-L. ( 1 ) 366 S h i e l d s , C . J . ( 3 . 7 ) 42 S h i g a , A . (1) 486 S h i g a , T. ( 3 . 5 ) 24 Shigematsu, K . ( 2 . 1 ) 189 S h i l l i n g , R.D. ( 1 ) 148 S h i l o v , A.E. ( 5 ) 144 S h i l o v , S.A. ( 3 . 6 ) 215 Shim, H.K. ( 3 . 2 ) 100; ( 3 . 6 ) 139 Shim, S.C. ( 1 ) 234, 444; ( 2 . 1 ) 146; ( 3 . 2 ) 1 2 , 9 4 , 9 8 , 100; ( 3 . 3 ) 28, 35; ( 3 . 4 ) 139; ( 3 . 5 ) 104; ( 3 . 6 ) 23, 24, 8 9 , 93, 139 Shima, K . ( 3 . 4 ) 55; ( 3 . 6 ) 131 Shima, T. ( 5 ) 169 Shimada, K. ( 3 . 6 ) 62 Shimazaki, I . ( 3 . 6 ) 150 Shimizu, K. ( 2 . 2 ) 8 4 Shimizu, Y. ( 2 . 1 ) 173 Shimo, T. ( 3 . 2 ) 50 Shimoda, E. ( 1 ) 388 Shimomura, N. ( 3 . 2 ) 41 S h i n , E.J. ( 3 . 2 ) 94; ( 3 . 4 ) 139; ( 3 . 6 ) 23, 24 S h i n k a i , S. ( 2 . 1 ) 189; ( 3 . 6 ) 11, 15 Shinoda, S. ( 2 . 1 ) 161; ( 2 . 2 ) 118, 119; ( 5 ) 6 4 , 75, 80, 81 Shinoda, T. ( 2 . 1 ) 25; ( 5 ) 116 S h i n o h a r a , I. ( 4 ) 171 S h i n o z a k i , A . ( 5 ) 25 S h i n s a k a , K . ( 1 ) 83 Shiokawa, J . ( 2 . 1 ) 200 S h i o z a k i , H. ( 4 ) 449 S h i r a i , H. ( 4 ) 372; ( 5 ) 181 S h i r a i , M. ( 4 ) 9 9 , 100, 123, 145 Shiraawa, M. ( 5 ) 203 S h i r o t a , V. ( 4 ) 1 7 Shizuka, H. (1) 129, 131, ( 1 ) 308, 457; (3.6) 197 S h l y a p i n t o k h , V.Ya. ( 4 ) 430, 431 Shono. T. (5) 118 s h u , X. ( 4 j $0

Shudo, K. ( 1 ) 388 Shudok, C. (3.2) 103 Shugar, D. ( 3 . 2 ) 9 7 S h u k l a , S.S. ( 5 ) 232 Shukun, L. ( 3 . 6 ) 6 4 Shulman, P.M. ( 4 ) 4 8 S h u l ' p i n , G.B. ( 2 . 2 ) 132, 133 S h u l t z , A.R. ( 4 ) 326 S h v e t s , D . I . ( 2 . 1 ) 67 Sicard, G. (3.7) 78 S i c i n s k i , R.R. (3.3) 80 S i d d i q u i , S. (3.5) 113 Sidebottom, H.W. ( 2 . 3 ) 53 S i d h u , K.S. (1) 467 S i d k y , M.M. ( 3 . 5 ) 132 S i d r a c h d e Cardona, M. ( 5 ) 235, 236 S i e g e l , J . A . ( 1 ) 61 Siegmund, M. ( 3 . 7 ) 37 Siemiarczuk, A . ( 5 ) 126, 128, 132 S i e n i c k i , K . ( 4 ) 238, 240 S i e r o c k a , M. ( 4 ) 144 S i h l e r , R. ( 3 . 3 ) 51 S i m i c , M.G. (1) 18 Simoff, D.A. ( 4 ) 352 Simon, F.R. ( 1 ) 401 Simon, R.C. ( 2 . 2 ) 42 Simon, T.J. ( 1 ) 401 Simpson, A . F . ( 2 . 2 ) 1 4 Simpson, M.B. (2.2) 1 4 S i n c l a i r , A.M. ( 1 ) 264; ( 4 ) 235 Sindew, E.I. ( 4 ) 78 S i n d o , Y. ( 4 ) 236 S i n g a l , K . K . ( 3 . 6 ) 30 S i n g e r , L.A. ( 1 ) 489 Singh, A . K . ( 3 . 2 ) 71; ( 3 . 4 ) 179 Singh, B. (3.6) 30 S i n g h , S. ( 3 . 5 ) 43; (3.6) 190, 191 S i n g h , S.K. ( 3 . 4 ) 36 S i n h a , H.K. ( 1 ) 137 S i n i t s y n , N.M. ( 2 . 1 ) 133 S i n i t s y n a , Z.A. ( 5 ) 217 S i p , B. ( 1 ) 253 S i r e r a , Y. ( 3 . 4 ) 7 3 S i r o t a , V.G. (2.3) 42 S i r o t k i n , N . I . ( 2 . 2 ) 27 S i s i d o , M. ( 4 ) 256 Sivyakova, L.N. ( 3 . 6 ) 22 S k a l s k i , B. ( 1 ) 384 Skeean, R.W. ( 3 . 2 ) 61 S k e l t o n , B.W. ( 1 ) 110 S k e t , B. (3.4) 41; ( 3 . 7 ) 118 S k i b s t e d , L.H. ( 2 . 1 ) 15, 153, 154 S k i l t o n , P.F. ( 1 ) 53. 228 S k i n n e r ; I . A . (315) 20

Author Index

585

Skorina, J . ( 5 ) 34 Skorokhodov, S.S. ( 3 . 4 ) 174; ( 4 ) 79

Skowronski, T.A.

( 4 ) 316,

319

Skripkin, Yu.V. ( 2 . 2 ) 37 Skurat, V.E. ( 4 ) 327 Slama-Schwok, A. ( 2 . 1 ) 1 6 6 , 167

I

Slifkin, M.A. ( 1 ) 41 Small, E.W. ( 1 ) 361 Smalley, R.K. ( 3 . 7 ) 95 Smart, J . C . ( 2 . 2 ) 112 Smedarchina, Z. ( 1 ) 3 ; ( 3 . 3 ) 18

Smets, G. ( 4 ) 3 4 , 66 Smirnov, R . F . ( 4 ) 428 Smirnova, E.I. ( 4 ) 183 Smirnova, N.B. ( 4 ) 287 Smit, K . J . ( 1 ) 237 Smith, C.M. ( 3 . 2 ) 11 Smith, D.E. ( 3 . 2 ) 52 Smith, G.F.H. ( 3 . 3 ) 1 Smits, J.M.M. ( 3 . 3 ) 8 7 ; ( 3 . 4 ) 135

Soutar, I. ( 4 ) 165 Southgate, R. ( 3 . 7 ) 172 Sowa, T. ( 2 . 2 ) 56 Spada, A.P. ( 3 . 3 ) 8 3 ; (3.4) 9 Spadaro, G.S. ( 4 ) 306 Spahni, W. ( 5 ) 209 Spajer, M. ( 4 ) 205 Spanhel, L. ( 2 . 1 ) 18 Spaulding, L. ( 2 . 1 ) 2 1-

Stibranyi, L. ( 3 . 6 ) 58 Stiegman, A.E. ( 2 . 2 ) 1 Stierman, T . J . ( 3 . 3 ) 5 7 , 5 8 ; ( 3 . 4 ) 29

Still, I . W . J . ( 3 . 6 ) 157 Stillman, M . J . ( 2 . 1 ) 239 Stiver, S . ( 3 . 1 ) 2 1 , 23 Stochel, G . ( 2 . 1 ) 73-75 Stoesser, R. ( 2 . 3 ) 4 8 , 49 Stohler, F . R . ( 4 ) 383 Stoiljkovic, D. ( 4 ) 64 213 Spears, K.G. ( 1 ) 1 8 5 , 203 Stone, G.B. ( 3 . 7 ) 7 1 Storp, S . ( 4 ) 301 Speckhardt, T.A. ( 4 ) 37 Spikes, J . D . ( 1 ) 414 Stothers, J . B . ( 3 . 2 ) 21 Stramel, R.D. ( 5 ) 205 Spiro, T.G. ( 1 ) 469 Spreti, S . ( 3 . 5 ) 72 Strandjord, A.J.G. ( 1 ) 1 3 4 ; ( 3 . 2 ) 52 Sprinkle, C.R. ( 2 . 1 ) 165 Spurlin, S . R . ( 2 . 1 ) 1 2 9 ; Strat, G . ( 4 ) 425 Strausz, O.P. ( 3 . 4 ) 4-6; (5) 60 ( 3 . 6 ) 1 6 4 ; ( 4 ) 201 Spurr, O.K. ( 4 ) 104 Streith, J. ( 3 . 4 ) 1 0 1 ; Spurr, P.R. ( 3 . 3 ) 1 1 2 ; ( 3 . 6 ) 17

( 3 . 4 ) 159

Spyroudis, S.P. ( 3 . 7 ) 181 Streith, S . ( 3 . 7 ) 141 Stretzkowski-Marden, F. Srimannarayana, G. ( 3 . 4 ) ( 1 ) 365

140

Smolenski, I . N . ( 4 ) 401 Snead, T.E. ( 3 . 2 ) 8 7 ;

Srinivasan, R . ( 4 ) 363-

(3.3) 83; (3.4) 9 Snow, J . T . ( 2 . 3 ) 2 9 ; ( 3 . 6 ) 196 Snow, M.R. ( 2 . 1 ) 47 Snyder, R. ( 1 ) 8 4 Snyder, S.W. ( 2 . 1 ) 112 Sobczynski, A. ( 5 ) 196 Sobukawa, M. ( 3 . 7 ) 125 Soga, 0 . ( 3 . 2 ) 1 6 1 , 162 Sokolov, V.N. ( 4 ) 325, 429 Sokolova, B.T. ( 2 . 1 ) 195 Sokolyuk, N.T. ( 3 . 2 ) 168 Solaro, R. ( 4 ) 1 6 6 , 215 Solomitz, K.S. ( 4 ) 224 Solozhenkin, P.M. ( 5 ) 210 Somekawa, K. ( 3 . 2 ) 50 Somersall, A.C. ( 4 ) 299 Somogyi, B. ( 1 ) 347 Sonawane, H.R. ( 3 . 3 ) 3 3 , 142, 144; ( 3 . 4 ) 149; ( 3 . 7 ) 173-175 Song, J.S. ( 3 . 5 ) 104 Song, X. ( 2 . 1 ) 204; ( 3 . 6 ) 7 Sonnichsen, F. ( 3 . 3 ) 92 Soria, J. ( 5 ) 166 Soriano-Garcia, M. ( 3 . 1 ) 3 1 ; ( 3 . 2 ) 49 Sorita, K. ( 2 . 1 ) 200 Sorokina, A.V. ( 4 ) 431 Sorrell, T.N. ( 2 . 2 ) 137 Sostero, S. ( 2 . 2 ) 3 Soto-Garrido, G. ( 2 . 3 ) 12 Soumillion, J.P. ( 5 ) 39

Srivastava, T.S. ( 2 . 1 )

366 172

Staab, H.A. ( 3 . 7 ) 126 Stadler, K.H. ( 2 . 1 ) 2 8 ; ( 5 ) 178

Staerk, H. (5) 124 Stahl, W. ( 5 ) 2 3 4 , 238 Stamm, E. ( 3 . 4 ) 38 Standen, M.C. ( 1 ) 420 Stanforth, S . ( 3 . 1 ) 2 4 ;

Stricker, R. ( 1 ) 75 Stringate, R. ( 3 . 6 ) 174 Strobel, F. ( 2 . 2 ) 10 Strub, H. ( 3 . 4 ) 101 Struckler, S.J. ( 5 ) 13 Struve, W.S. ( 1 ) 2 5 8 , 313 Stuart, J . G . ( 3 . 4 ) 120 Studzinskii, O.P. ( 2 . 1 ) 195

Stueben, K.C. ( 4 ) 135 Stufkens, D . J . ( 2 . 2 ) 4 5 , 57,

58

Stuhl, F. ( 2 . 3 ) 31 Stults, J.S. ( 3 . 7 ) 121 Stanovik, B. ( 3 . 7 ) 30 Stunnenberg, F. ( 3 . 2 ) 6 9 Starczewski, I. ( 4 ) 144 Staryi, V.P. ( 1 ) 472 Su, S.C. ( 2 . 3 ) 54 Stasicka, 2. ( 2 . 1 ) 7 3 , 75 Su, S.Y. ( 1 ) 66 Susrez, E. ( 3 . 7 ) 1 8 6 , 187 Staskun, B. ( 3 . 5 ) 125 Suau, R. ( 3 . 4 ) 116 Statman, D. ( 1 ) 222 Subrahmanyam, D. ( 3 . 2 ) 8 4 Steel, C. ( 4 ) 446 Subramanian, G.B.V. ( 3 . 1 ) Steer, R . P . ( 1 ) 339 5 4 ; ( 3 . 7 ) 101 Steinberg, H. ( 3 . 5 ) 7 0 Subramanian, R . ( 3 . 7 ) 9 , Steinmetz, K.M. ( 1 ) 185 1 1 , 12 Steinmetzer, H.-C. ( 3 . 2 ) Suckling, I . D . ( 3 . 2 ) 22 103 Suddaby, B.R. ( 1 ) 2 9 5 ; Steinmueller, F. ( 2 . 1 ) ( 3 . 4 ) 129

( 3 . 3 ) 2 2 , 23

1 1 3 ; ( 5 ) 142

Stel'mashok, V.E.

(2.1)

143

Stelzer, E.H.K. ( 1 ) 75 Stemple, T.W. ( 4 ) 377 Stenstrom, Y. ( 2 . 2 ) 91 Stepanek, P. ( 4 ) 239 Stepanenko, V . I . ( 2 . 1 ) 1 9 Stewart, G.M. ( 2 . 2 ) 12 Stevart. D.W. ( 1 ) 156 Steiowski, J.JI ( 1 ) 210

Sudhakar, A. ( 3 . 4 ) 109 Sueishi, Y. ( 3 . 3 ) 7 ; (3.6) 9

Suetinov, A.P. ( 2 . 3 ) 44 Sugawara, T. ( 3 . 7 ) 92 Sugihara, Y. ( 1 ) 103 Sugimori, A . ( 2 . 2 ) 8 3 ; (2.2) 84, 97; (3.4) 99, 100; ( 3 . 5 ) 122; ( 3 . 6 ) 1 3 0 ; (5) 77

Author Index

586 Suginome, H. ( 3 . 2 ) 4 0 , 4 2 ; ( 3 . 7 ) 1 8 4 , 185 Sugisawa, H. ( 2 . 3 ) 2 6 ; ( 3 . 4 ) 157; ( 3 . 6 ) 200 Sugiura, M . ( 3 . 6 ) 6 8 Sugiura, T. ( 3 . 7 ) 10 Sugiyama, H. ( 3 . 6 ) 147 Sugiyama, T. ( 3 . 4 ) 9 9 ; ( 3 . 5 ) 122 Suglobov, D.N. (2.1) 219 Suguira, K. ( 1 ) 190 Suguwara, Y. ( 3 . 7 ) 65 Suh, I.S. ( 2 . 1 ) 208 Suijker, J . L . G . (1) 88 Sukale, R. ( 3 . 1 ) 4 2 ; ( 3 . 6 ) 76 Sukegawa, H. ( 3 . 4 ) 1 8 5 ; ( 3 . 6 ) 149 Sullivan, B.P. ( 2 . 1 ) 134 Suluimanov, B.A. ( 4 ) 294 Sumi, K. ( 5 ) 152 Sumiyesgu, T. ( 4 ) 96 Sumiyoshi, T. ( 1 ) 4 2 7 ; ( 3 . 6 ) 213, 214; ( 3 . 7 ) 1 2 2 ; ( 4 ) 31 Sundahl, M. ( 3 . 3 ) 30 Sundberg, R.J. ( 3 . 7 ) 80 Sundermeyer, W. ( 3 . 7 ) 129 Sundstrom, V. ( 1 ) 214, 242; ( 3 . 3 ) 1 6 ; ( 4 ) 438 Sung, C.S.P. ( 4 ) 232 Suppan, P. ( 1 ) 5 , 9 1 , 1 7 0 , 173 Surya Prakash, G.K. ( 3 . 7 ) 41 Suschitzky, H. ( 3 . 7 ) 95 Susi, P.V. ( 4 ) 4 0 5 , 416 Suter, G.W. ( 1 ) 437, 446, 453 Sutherland, J.C. ( 1 ) 333, 334 Sutherland, R.G. ( 2 . 2 ) 86 Sutin, N. ( 2 . 1 ) 1 4 , 109 Suto, M. ( 3 . 2 ) 1 5 3 , 1 5 7 ; ( 3 . 4 ) 4 8 ; ( 3 . 6 ) 110 Suzuki, J. ( 3 . 4 ) 77 Suzuki, K. ( 4 ) 422 Suzuki, N. ( 3 . 5 ) 7 5 , 123 Suzuki, S . ( 3 . 6 ) 145; ( 4 ) 3 7 , 126 Suzuki, S.S. ( 3 . 4 ) 77 Suzuki, T. ( 2 . 1 ) 6 8 ; ( 3 . 5 ) 37 Svenberg, C.E. ( 1 ) 382 Svorcik, V. ( 4 ) 417, 418 Swayambunathan, V. ( 1 ) 113 Sweany, R.L. ( 2 . 2 ) 1 3 , 36 Syassen, K. ( 1 ) 112 Sydnes, L.K. ( 3 . 7 ) 138 Symons, M.C.R. ( 3 . 7 ) 158 Szabo, A.G. ( 1 ) 390

Szeimies, G. ( 3 . 7 ) 31 Szentirmay, M.N. ( 1 ) 293; ( 4 ) 1 8 5 , 206

Szezepanski, J. ( 1 ) 107 Szyclinski, J. ( 1 ) 87 Tabankia, M.H. ( 4 ) 346 Tabata, Y. ( 1 ) 9 6 , 1 9 0 , 211

Tabayashi, K. ( 3 . 7 ) 6 0 Taber, A.M. ( 3 . 6 ) 215 Tabuchi, K. ( 4 ) 5 2 , 115 Tada, M. ( 3 . 6 ) 146 Tada, Y. ( 3 . 4 ) 137 Taen, S . ( 1 ) 440 Taga, T. ( 2 . 2 ) 56 Tagawa, S . ( 1 ) 9 6 , 1 9 0 , 211

Taghizadeh, N. ( 1 ) 192 Tajima, E. ( 4 ) 422 Taka, M. (1) 375 Takagi, H. ( 3 . 5 ) 6 9 Takagi, K. ( 2 . 1 ) 21 Takagi, M. ( 5 ) 233 Takahara, S. ( 1 ) 486 Takahashi, A. ( 3 . 4 ) 1 4 7 ; ( 3 . 7 ) 143

Takahashi, E. ( 4 ) 5 7 , 1 4 6 , 148

Takahashi, M. ( 3 . 6 ) 9 6 Takahashi,.T. ( 1 ) 208; (2.2) 119; ( 3 . 2 ) 9 2 ; (3.5) 49; ( 3 . 6 ) 18; ( 5 ) 8 1 , 1 0 1 , 102 Takahashi, Y. ( 4 ) 226 Takakubo, M. ( 1 ) 2 9 9 ; ( 2 . 1 ) 234; ( 5 ) 138 Takamuku, S. ( 2 . 1 ) 2 0 1 ; ( 3 . 3 ) 3 6 ; ( 3 . 6 ) 129 Takao, N. ( 3 . 6 ) 6 8 Takarik, Z.G. ( 4 ) 80 Takase, I. ( 4 ) 73 Takashima, M. ( 1 ) 1 3 5 ; ( 3 . 5 ) 23 Takata, T. ( 3 . 5 ) 2 , 1 5 1 ; ( 3 . 7 ) 69 Takayama, K. ( 3 . 6 ) 7 1 , Takayama, M. ( 4 ) 8 Takechi, H. ( 3 . 2 ) 1 4 6 , 1 4 7 ; ( 3 . 6 ) 8 0 , 116 Takei, M. ( 3 . 4 ) 8 1 ; ( 3 . 6 ) 10 Takemura, F. ( 4 ) 7 2 , 233 Takenaka, S . ( 3 . 4 ) 9 9 ; ( 3 . 5 ) 122 Takenchi, A . ( 4 ) 303 Takeshita, H. ( 3 . 2 ) 141 6 , 1 6 0 ; ( 3 . 5 ) 75 Takeuchi, S . ( 2 . 2 ) 111 Takibsev, Zh.S. ( 5 ) 23 Takizawa, A. ( 4 ) .218

Takubo, Y. ( 1 ) 211 Takui, T. ( 3 . 7 ) 6 4 Takuwa, A. ( 3 . 2 ) 1 6 1 , 162 Talapatra, G.B. ( 1 ) 483 Tale, I.A. ( 4 ) 289 Taleb, A.M. ( 5 ) 239 Taljaard, B. ( 3 . 5 ) 100 Tal'roze, V.L. ( 4 ) 327 Tamai, N. ( 1 ) 259 Tamaki, T. ( 3 . 4 ) 161 Tamazaka, T. ( 1 ) 142 Tames, J. ( 2 . 1 ) 6 6 Tamiaka, H. ( 3 . 2 ) 163 Tamilarsan, R. ( 1 ) 268; ( 2 . 1 ) 111

Tamminga, J.J. ( 3 . 4 ) 71 Tamura, N. ( 4 ) 272 Tamura, Y. ( 3 . 5 ) 1 5 1 ; ( 3 . 6 ) 96

Tan, P. ( 3 . 6 ) 63 Tan, S.L. ( 3 . 2 ) 28 Tanaka, A. ( 5 ) 25 Tanaka, F. ( 1 ) 1 7 1 , 436; ( 4 ) 266

Tanaka, H. ( 3 . 6 ) 1 9 7 ; ( 5 ) 165

Tanaka, H.K. ( 2 . 1 ) 5 7 , 58 Tanaka, I. ( 1 ) 215 Tanaka, J. ( 1 ) 326 Tanaka, K. ( 5 ) 1 7 4 , 185 Tanaka, M. ( 1 ) 215; (2.1) 181; ( 3 . 2 ) 5 ; ( 3 . 3 ) 117; ( 4 ) 9 9 , 100, 122, 1 2 3 , 145; ( 5 ) 165 Tanaka, N. ( 3 . 3 ) 45 Tanaka, S . ( 4 ) 5 , 122 Tanaka, T. ( 3 . 5 ) 1 1 2 ; (3.6) 9 Tanaka, Y. ( 1 ) 9 6 ; ( 2 . 1 ) 1 7 3 , 174 Tanemura, H. ( 5 ) 198 Tang, C.P. ( 3 . 1 ) 1 0 , 11 Tang, Z. ( 4 ) 155 Tanida, H. ( 3 . 3 ) 4 7 ; ( 3 . 6 ) 50 Taniguchi, H. ( 3 . 7 ) 177 Taniguchi, Y. ( 4 ) 221 Tanirnoto, Y. ( 3 . 4 ) 1 7 8 ; ( 3 . 5 ) 23 Tanner, M. ( 1 ) 498 Tantravaki, V. ( 1 ) 7 2 Tao, T. ( 1 ) 363 Taoda, H. ( 3 . 3 ) 9 5 ; ( 5 ) 53 Tarasevich, M.R. ( 5 ) 227 Tarasov, V.F. ( 3 . 1 ) 25

Tardieu de Maleissye, J. ( 3 . 5 ) 142

Tarzia, G. ( 3 . 5 ) 119 Tasayco, M.L. ( 3 . 4 ) 46 Tasumi, M. ( 1 ) 9 5 . 439 Tatikolov, A.H. (1) 489

Author Index Tauer, E. (3.1) 53; (3.6) 38, 42 Taylor, D.G. (1) 431 Taylor, J . R . (1) 212 Taylor, P. (1) 356 Taylor, R.S. ( 1 ) 198 Tazuke, S. (1) 506; (2.1) 90, 127; (4) 245; (5) 61, 122 Teashima, M. (3.7) 148 Tedeschi, P. (3.6) 56 Tedjamulia, M.L. (3.4) 120, 121 Teh, C.E. (3.6) 99 Teh, C.Z. (3.2) 131 Teichner, S.J. (2.1) 26; (5) 3 Teki, Y. (3.7) 64 Tempczyck, A. ( 1 ) 384 Tennakone, K. (2.1) 34; (5) 24 Tera, F.M. (4) 436 Terada, K. (3.2) 93; (3.6) 16 Teranishi, H. ( 1 ) 171, 189, 190, 436; (3.4) 83 Terasaka, K . (3.4) 75; (3.6) 209 Terashima, M. (3.4) 96; (3.7) 147 Teratani, S. (2.2) 51 Terazima, M. ( 1 ) 122, 441 Ternansky, R.J. (3.4) 35 Terner, J. (1) 58, 469 Tero-Kubota, S. (2.2) 139 Tersawa, T. (3.7) 67 Teruel, J.A. ( 1 ) 369 Teufel, E. (3.4) 52 Theis, W. (3.7) 73 Thewalt, U. (2.2) 22 Thiel, W. (3.3) 89 Thielen, A.P.G.M. ( 1 ) 404 Thierry, J. (3.7) 117 Thirunamachandran, T. (1)

(5) 223 Thomson, A. (3.4) 69 Thorel, P.J. (3.6) 119 Ticke, B. ( 4 ) 18 Tietze, L.-F. (3.2) 38; (3.6) 94 Tikhomirov, V.V. (2.1) 133 Tiltina, I. ( 4 ) 286 Timofeeva, T.V. (5) 158 Timpe, H.-J. ( 1 ) 303: (3.6) 4, 58; (3.7) 83; (4) 24, 39, 40, 47, 51, 154 Tinnemans, A.H.A. (3.3) 94; (5) 43 Tirrell, D.A. ( 4 ) 53 Titov, A . A . (2.3) 35, 36 Tiwari, L.B. ( 1 ) 380 Tkachenko, Z.A. (2.1) 67 Tobe, Y. (3.2) 23; (3.4) 3 Tobita, S. (1) 442 Tochtermann, W. (3.3) 92 Toda, R. (3.2) 153, 156; (3.4) 49; (3.6) 109 Toda, T. (4) 388, 396 Todesco, R.V. ( 4 ) 263 Togo, H. (3.7) 115, 116 Toi, K. (5) 203 Toivonen, J. (2.1) 215 Tojo, G. (3.4) 116 Tojo, S. (3.2) 153, 157; (3.4) 48; (3.6) 110 Toki, S. (2.1) 201; (3.3) 36; (3.6) 129 Tokuda, T. (5) 203 Tokumaru, K. (1) 141, 188, 439, 486; (3.3) 13; (3.5) 27, 36 Tol, A . J . W . (3.4) 119 Tolbert, L.M. (3.3) 149; (3.7) 57 Tolman, C.A. (3.7) 2 Tolstikov, G.A. (2.1) 1 106; (2.3) 57 Thistlethwaite, P. (1) Tomai, N. (1) 35 53, 273 Tho, N.D. (3.2) 36 Tomas, V. (3.5) 126 Tomaschewski, G. (3.7) Thomas, A.C. (2.2) 138 37, 38 Thomas, B. (3.5) 130 Thomas, E.W. (1) 145, 166 Tomasik, P. (3.7) 97 Thomas, J.K. (1) 92, 298, Tombari, E. (4) 76 Tominaga, T. (2.2) 7 1 307; (2.1) 115, 116, Tomioka, H. (3.7) 10, 39, 121; (4) 229; ( 5 ) 161, 193, 205 53, 60 Thomas, J.W. ( 4 ) 262 Tomioka, K. (3.2) 5 Thomas, P. (2.2) 31, 33 Tomita, H. (3.2) 121 Thomas, W.R.L. (5) 237 Tomokiyo, K. (2.1) 200 Thomas-David, G. ( 1 ) 383; Toms, M. (3.7) 40 Toncheva, V. (4) 102 (2.1) 246 Thompson, N.L. (1) 412 Tondello, E. (2.2) 81 Thompson, R.L. (3.5) 42; Toney, C.G. (2.1) 46

587 Tooburg Jenson, J.P. (4) 386 Toppet, S. (3.7) 35; (4) 260 Toptygin, D.Ya. (3.7) 81 Toribio, F. (1) 130 Torikai, A. (4) 303, 304 Toriumi, M. (1) 83 Torkelson, J.M. (4) 254 Torrent, A.O. (1) 317 Torres, M. (3.4) 4-6; (3.6) 164; (3.7) 90 Toscano, A. (3.2) 49 Toscano, R.A. (3.1) 31 Toscano, V. (4) 444 Toshima, N. (3.5) 49; (5) 101, 102 Totrajada, J. (3.1) 15 Townsend, D.E. (3.4) 51 Toyoda, T. (3.4) 167 Trammell, G.L. (3.2) 61 Tran-Thi, T.H. (5) 135 Traverso, 0. (2.1) 71; (2.2) 3 Treacy, J.J. (2.3) 53 Trebert, Y. (3.7) 140 Trefonas, P. ( 4 ) 371 Treichel, r. (5) 124 Triandos, P. ( 1 ) 273 Tricot, Y.-M. (1) 297; (5) 215 Trifinov, L.S. (3.2) 68; (3.4) 182 Tripathi, G.N.R. ( 1 ) 97 Tritthart, H.A. (1) 407 Trkula, M. (1) 68 Troe, J. (3.3) 19 Trogler, W.C. (2.2) 131 Trojan, D. (3.4) 51 Trotter, J. (3.1) 34, 36 Truscott, T.G. ( 1 ) 477, 480 Tsao, L. (2.1) 215 Tsay, S.Y. ( 4 ) 137 Tsay, Y.-H. (2.2) 5; (3.4) 47; (3.6) 120 Tschamber, T. (3.6) 17; (3.7) 141 Tse, A. (3.2) 131; (3.6) 99 Tseung, A.C. ( 5 ) 206 Tsivenko, V . I . (5) 208 Tsnooka, M. (4) 122, 1 2 3 Tsoi, S.C. (3.6) 166 Tsuchida, A. (3.3) 120; (3.6) 92; (4) 234 Tsuchiya, J. (3.7) 125 Tsuchiya, T. (1) 35; (3.6) 57, 71; (3.7) 94, 96 Tsujimoto, K. (3.6) 106; (3.7) 127

Author Index

588

Tsujita, Y. ( 4 ) 218 Tsukamoto, M. ( 4 ) 1 9 8 , 214

Tsuzuki, K. ( 3 . 6 ) 146 Tuckerman, R.T. ( 2 . 3 ) 50 Tueling, M.B. ( 4 ) 376 Tung, C.H. ( 1 ) 306 Turkenburg, L.A.M. ( 3 . 4 ) 3

Turley, W.D. ( 1 ) 294 Turnbull, J.H. ( 1 ) 322 Turner, D.H. ( 1 ) 391 Turner, J.J. ( 2 . 2 ) 1 4 , 9 5 , 98

Urabe, S. ( 4 ) 439 Urachem, M.N. ( 4 ) 91 Ushiki, H. ( 1 ) 270; ( 4 )

Van Stappen, P. ( 3 . 7 ) 35 Van Steenwinkel, R. ( 2 . 1 )

2 3 6 , 266 Usui, M. ( 1 ) 388 Usui, Y. ( 1 ) 4 9 3 ; ( 3 . 5 ) 35 Uyehara, T. ( 3 . 2 ) 81-83, 85

van Tol, M.W. ( 1 ) 88 Vanucci, C. ( 2 . 3 ) 1 7 ;

Vaida, V. ( 2 . 2 ) 2 Vaillet, P. ( 1 ) 159 Vainshtein, A.B. ( 4 ) 286,

Turoverov, K.K. ( 1 ) 338 344 Turro, N.J. ( 1 ) 1 4 3 , 1 4 4 , Valat, P. ( 1 ) 9 4 ( 1 ) 2 7 1 , 289, 2 9 0 , 3 0 4 , Valeeva, T.G. ( 3 . 7 ) 1 386, 464, 4 9 2 ; ( 3 . 1 ) 6 , Valeur, B. ( 1 ) 260, 305 7 , 2 7 ; ( 3 . 4 ) 1 8 7 ; ( 3 . 5 ) Valiev, K.A. ( 4 ) 327 5 , 8 , 2 2 ; ( 3 . 7 ) 4 0 , 5 2 ; van Arkel, B. ( 3 . 4 ) 34 Van Audenhove, M. ( 3 . 2 ) ( 4 ) 44 2 7 ; ( 3 . 6 ) 205 Tverskoi, V.A. ( 5 ) 158 Tyler, D.R. ( 2 . 2 ) 1 , 4 7 , VanEik, H. ( 2 . 3 ) 1 3 ; 1 0 0 , 101

( 3 . 7 ) 88

Tyler, P.C. ( 3 . 2 ) 6 0 Tymyanskii, Ya.R. ( 3 . 4 )

Van Damme, H. ( 1 ) 3 0 9 ;

126-128; ( 3 . 6 ) 2 8 , 29 Tyrrell, H.M. ( 3 . 4 ) 22

Vandendriessche, J. ( 4 )

( 2 . 1 ) 1 3 7 ; ( 5 ) 3 0 , 117 244

Van den Heuvel, C.J.M. ( 3 . 5 ) 70

Uasugi, M. ( 4 ) 72 Uchida, K. ( 4 ) 152 Uchido, J. ( 4 ) 148 Uchino, T. ( 3 . 6 ) 96 Uchiyama, K. ( 3 . 6 ) 9 7 ; ( 4 ) 281 Uda, H. ( 3 . 2 ) 8 0 ; ( 3 . 3 ) 114 Udagawa, M. (1) 141 Udaykumar, M. ( 3 . 3 ) 3 3 ; ( 3 . 7 ) 174 Ueda, A. ( 4 ) 1 0 0 , 145 Ueda, H. ( 2 . 1 ) 38 Ueda, K. ( 3 . 2 ) 23 Ueda, T. ( 5 ) 171 Uehara, M. ( 3 . 5 ) 23 Ueno, F.B. ( 2 . 1 ) 147 Ueno, Y. ( 1 ) 357; ( 3 . 5 ) 82 Ueyama, T. ( 3 . 5 ) 123 Ukdova, E.M. ( 4 ) 118 Ullah, S.S. ( 2 . 2 ) 7 6 , 77 Umezawa, B. ( 3 . 4 ) 1 4 7 ; ( 3 . 7 ) 143 Umrigar, P.P. ( 3 . 5 ) 78 Unsoeld, E. ( 1 ) 37 Uosaki, K. ( 2 . 1 ) 2 9 ; ( 5 ) 176 Uozo, Y. ( 1 ) 239; ( 3 . 3 ) 29 Upadhyaya, V. ( 1 ) 380 Upmacis, R.K. ( 2 . 2 ) 14

van den Zegel, M. ( 1 ) 36 van der Auweraer, M. ( 1 ) 213, 346

Van der Kelen, G.P. ( 2 . 3 ) 52

van der Loop, E.A.R.M. (3.2) 7

van der Meer, B.W. ( 1 ) 48 van der Veen, J.M. ( 3 . 2 ) 7 9 , 107

Van der Werf, S. ( 4 ) 77 Van der Wielen, F.W.M. ( 3 . 4 ) 87

van der Zegel, M. ( 1 ) 213 van der Zwan, G. ( 1 ) 7 Vandewalle, M. ( 3 . 2 ) 2 7 ; ( 3 . 6 ) 205

Van Dijk, H.K. ( 2 . 2 ) 45 Van Duyne, R.P. ( 1 ) 256 van Eijk, L.M.J. ( 1 ) 1 8 1 ; ( 3 . 4 ) 72

Van Eldik, R. ( 2 . 1 ) 184 van Ginkel, F.I.M. ( 1 ) 180

Van Hemelryck, B. ( 3 . 1 ) 15

Van Hiftje, L. ( 3 . 2 ) 2 7 ; ( 3 . 6 ) 2 0 5 ; ( 3 . 7 ) 15

Van Himbergen, J.E. (1) 1 2 , 279

Van Hoek, A. ( 1 ) 67 Vannikov, A.V. ( 4 ) 173

77 ( 3 . 4 ) 169

van Zeijl, P.H.M. ( 1 ) 1 8 1 ; ( 3 . 4 ) 72

Varani, G. ( 2 . 1 ) 92 Vareux, J. ( 4 ) 128 Varfolomeev, S.D. ( 5 ) 14 Varie, D.L. ( 3 . 7 ) 121 Varkhede, R.S. ( 1 ) 504 Varma, C.A.G.O. ( 1 ) 8 8 , 8 9 , 1 0 9 , 179-181; ( 3 . 4 ) 6 5 , 7 1 , 72 Varma, I.K. ( 4 ) 3 0 8 , 404 Varshovski, L. ( 1 ) 362 Vasina, E.R. ( 3 . 2 ) 44 Vauthey, E. ( 1 ) 173 Vaz, C. ( 3 . 5 ) 7 8 Vechkanov, G.N. ( 4 ) 183 Vedejs, E. ( 3 . 7 ) 121 Veillard, A. ( 2 . 2 ) 103 Velichkov, V.A. ( 4 ) 431 Velichkova, R. ( 4 ) 102 Velikov, C.V. ( 4 ) 327 Velthorst, N . H . ( 1 ) 116 Venema, R.C. ( 1 ) 495 Venkataraman, V.R. ( 3 . 5 ) 115 Venkatesan, K. ( 3 . 2 ) 4 3 , 4 5 ; ( 3 . 4 ) 153 Venturi, M. ( 2 . 1 ) 1 0 4 , 142; ( 5 ) 99 Veprek-Siska, J. ( 3 . 5 ) 111 Verbovaya, S.N. ( 4 ) 75 Verdonck, L. ( 2 . 3 ) 52 Verdu, J. ( 4 ) 420 Verhoeven, J.W. ( 1 ) 1 7 6 ; ( 5 ) 1 2 5 , 134 Verjovski-Almeida, S . ( 1 ) 37 1 Verral, R.E. ( 1 ) 339 Verschoor, C.M. ( 2 . 1 ) 217 Vershal, V.V. ( 4 ) 2 7 6 , 278 Vert, F.T. ( 1 ) 317 Vettermann, S . ( 3 . 5 ) 149 Veyret, B. ( 3 . 5 ) 89 Vichutinskaya, E.V. ( 4 ) 3 3 2 , 401 Vidal, C.J. ( 1 ) 369 Vieira Ferreira, L.F. ( 1 ) 254 VSg, A . ( 4 ) 454 Villalain, J. ( 1 ) 369 Vinogradov, I.P. ( 2 . 3 ) 43 Vinogradov, S.A. ( 2 . 1 ) 183 Viovy, J.L. ( 1 ) 1 0 8 ; ( 4 )

Author Index 168, 212, 253, 257 Virag, L. (3.4) 92 Virgili, A. (5) 151 Visser, A.J.W.G. (1) 23, 67; (4) 255

Visser, P.C. (3.2) 102 Visser, R.-J. (1) 109; 179, 180

Vliers, D.P. (2.1) 89 Vo-Dinh, T. (1) 118, 437 VVogel, E. (3.3) 111 Vogel, F.R. (3.5) 100 Vogel, P. (2.2) 5 Vogl, 0. (4) 382, 411, 412

Vogler, A. (2.1) 5, 135 Voightman, E. (1) 2 1 Voituriez, L. (3.2) 99; (3.6) 87

Volkov, O.G. (2.2) 37 Vollhardt, K.P.C. (2.2) 107

Voltz, R. (1) 253 Von der Linde, D. (4) 329 Von Gustorf, E.A.K. (2.2) 17

Vonhoene, P. (4) 453 von Kan, P.J.H. (1) 109 von Schnering, H.G. (3.1) 14; (3.2) 86; (3.3) 43, 92; (3.5) 77; (3.7) 18, 24 Von Sonntag, C. (3.7) 130 von Wartburg, B. (3.2) 57 Vonwiller, S.C. (3.5) 83 Von Zelewsky, A. (2.1) 78, 79, 93, 130, 175, 176; (5) 55, 58, 123 Vorotnikov, A.P. (3.7) 81 Vos, J.G. (5) 228 Voyakin, I . V . (2.2) 109 Vrachnou-Astra, E. (2.1) 170; (5) 76 Vretsena, N.B. (2.1) 61 Vuilleumier, J.J. (2.1) 207 Vymazal, Z. (4) 417, 418 Vymazalova, Z. (4) 417 Vysotskii, Yu.B. (3.6) 22

Wacholtz, W.F. (2.1) 80, 84: (5) 57

Wachs, I.E. (2.1) 27; (5) 191

Wada, I. (1) 270 Wada, M. (3.2) 142; (3.6) 82; (4) 37, 126

Wagner, G.S. (2.3) 3 Wagner, J. ( 3 . 4 ) 175, 176; (3.6) 124

589

Wagner, P.J. (1) 484; (2.2) 43; (3.1) 39, 40; (3.4) 151; (3.5) 11 Wagner, R. (4) 24, 154 Wahiduzzaman, S.M. (2.2)

Wayner, K. (4) 45 Webber, S.E. (1) 267; (4)

258, 259, 261; (5) 162, 178, 194 Weber, M.A. (2.2) 65 Weber, R.H. (3.3) 86 77 Weber, W. (2.1) 184; Wahl, P. (1) 56 (3.7) 122 Wakabayashi, S. (1) 103 Webster, G.R.B. (3.4) 86, Wakao, S. (3.6) 179 87; (3.5) 50 Wakashima, Y. (4) 130 59; (3.5) 1 2 , 20; (5) Wakefield, B.J. (3.1) 30 Wakisaka, A. (3.5) 27, 36 126, 128, 132 Weers, J.G. (1) 496 Waksman, D. ( 4 ) 328 Weetall, H.H. (5) 225, Wallace, J. (1) 408 226 Wallace, S.C. (1) 79 Wehry, E.L. (1) 22 Walsh, E.J. (3.7) 7 1 Weidenbruch, M. (2.3) 23; Walters, E.A. (2.3) 40 (3.6) 195 Waltz, W. (2.1) 180 Weider, R. (3.3) 111 Wamhoff, H. (3.5) 132 Weill, G. (4) 265 Wan, C.S.K. (3.2) 59; Weir, D. (1) 419, 498 (3.5) 12; (5) 132 Weir, N.A. ( 4 ) 334, 337 Wan, J.K.S. (3.2) 158, Weisenborn, P.C.M. (1) 164; (3.5) 22 109, 179 Wan, P. (3.4) 105-107; Wan, P. (3.5) 8 , 52, 135 Weiss, R.G. (3.4) 66, 67 Weissenfels, M. (4) 442 Wandelt, B. (4) 307 Weitz, E. (3.3) 64 Wang, D. (3.5) 57 Weixelbaumer, D.W. ( 4 ) Wang, E. (49 85, 88 269 Wang, F.W. (4) 230, 237, Welch, G.R. (1) 347 252 Wang, H. (2.2) 105; (3.6) Weller, A. (5) 124 Weller, H. (3.6) 42 63 Wang, L. (3.2) 79; (4) 89 Wellner, E. (1) 310 Welzel, P. (3.7) 75 Wang, T. (2.1) 223 Wen, Z. (4) 399 Wang, X. (3.5) 38 Wender, P.A. (3.4) 35-37 Wang, Y. (1) 178; (2.2) 63; (3.2) 108; (3.6) 7; Weng, Y. (2.1) 1 7 Wennerstroem, 0. (3.3) 30 (4) 60, 217 Wannamaker, M.W. (3.7) 29 Wensel, T.G. (1) 395 Wenska, G. (3.6) 98 Ward, D.L. (3.1) 39; Werner, T.C. (1) 114, 331 (3.4) 151; (3.5) 11 Wessely, H.-J. (3.4) 156; Ward, I . M . (4) 164 (3.6) 198 Ware, W.R. (1) 49-51, West, B.J. (1) 245, 246 312, 325, 329 West, P.R. (3.7) 50 Warman, J.M. (1) 109 West, R. (2.3) 13, 21; Warner, I . M . (1) 62 (3.7) 88; (4) 371 Warren, S. (3.3) 2 Weston, R.E. (1) 82 Wasgestian, F. (2.1) 50 Weyerstahl, P. (3.1) 51 Washida, N. (3.5) 69 Weyna, I. (1) 209 Washio, M. (1) 96, 190, White, A.H. (1) 110 211 Wasielewski, M.R. (1) 175 White, D.A. (1) 118 Wasserman, H.H. (3.5) 96 White, J.D. (3.2) 61 Whitharn, G.H. (2.3) 14 Watabiki, 0. (3.6) 145 Whiting, M.C. (2.2) 79 Watanabe, H. (2.3) 27; Whittaker, A.K. (4) 361 (3.6) 197 Whittall, J. (3.2) 126; Watanabe, T. (3.4) 178; (3.4) 141 (3.5) 23 Whitten, D.G. (1) 220, Waterfeld, A. (3.7) 182 285, 295; (2.1) 248; Watkins, D.A.M. (3.4) 94 (3.3) 2 2 , 23; (3.5) Watts, R.J. (2.2) 112

Author Index

5 90 118; ( 5 ) 70

( 3 . 6 ) 126

Witkowski, K. ( 4 ) 336 Whittle, E. ( 2 . 3 ) 50 Wittenberger, S . ( 3 . 7 ) Whyman, R. ( 2 . 2 ) 14 121 Wiberg, K.B. ( 3 . 3 ) 73 Wickramaaratchi, M.A. ( 1 ) Wittwer, V. ( 5 ) 238 Wi Wang, F. ( 4 ) 243 82 Wickramanayake , S . ( 2 . 1 ) Wodtke, A.M. f 3 . 3 ) 38 Woehrle, D . ( 2 . 1 ) 233, 3 4 ; ( 5 ) 24 Wiechert, R. ( 3 . 1 ) 16 ( 5 ) 66 Woessner, G. ( 1 ) 210 Wietelmann, U. ( 3 . 6 ) 217 Wolf, B. ( 3 . 7 ) 68 Wietfeld, B. ( 3 . 2 ) 88 Wolf, C . J . ( 4 ) 351 Wigley, J.W. ( 4 ) 197 Wijnaundts van Resandt, Wolf, D.E. ( 1 ) 276 Wolf, H.C. ( 1 ) 1 1 5 , 255 R.W. ( 1 ) 75 Wolf, H.R. ( 3 . 2 ) 57 Wilbrandt, R. ( 1 ) 421 Wolff, C.R. ( 2 . 2 ) 46 Wild, U.P. ( 1 ) 2 8 , 9 4 , 1 1 9 , 2 8 5 , 4 3 7 , 4 4 6 , 453 Wolff, S. ( 3 . 2 ) 1 , 2 , 1 7 , Wilda, J. ( 3 . 7 ) 38 6 7 ; ( 3 . 6 ) 206 Wilde, R.G. ( 3 . 7 ) 121 Wolinski, L. ( 4 ) 336 Wiles, D.M. ( 4 ) 3 7 9 , 386 Wong, D . F . ( 3 . 2 ) 5 9 ; Wilkinson, F. ( 1 ) 4 6 5 ; ( 3 . 5 ) 12 Wong, K.-M. ( 3 . 4 ) 113 ( 3 . 1 ) 9 ; ( 4 ) 435 Wong, K.S. ( 4 ) 190 Williams, A.C. ( 1 ) 352 Williams, D . J . ( 4 ) 211 Wong, S.K. ( 3 . 4 ) 164 Williams, J . R . ( 3 . 1 ) 1 7 ; Wong, W.K. ( 5 ) 188 Wong, Y.-F. ( 3 . 1 ) 32 ( 3 . 2 ) 6 5 ; ( 3 . 6 ) 170 Williams, P.J.K. ( 4 ) 186 Woodin, R.L. ( 2 . 2 ) 52 Woods, J. ( 4 ) 1 2 4 , 125 Willig, F. ( 1 ) 213 Wooler, J. ( 4 ) 317 Willner, I. ( 1 ) 302; Worman, H.J. ( 1 ) 400 ( 2 . 1 ) 125; ( 3 . 3 ) 143; Wostratzky, D.' ( 4 ) 13 ( 3 . 5 ) 2 6 ; ( 5 ) 1 0 9 , 110 Wright, T . A . ( 3 . 7 ) 156 Willsher, C . J . ( 1 ) 4 6 5 ; Wrighton, M.S. ( 2 . 2 ) 8 7 , ( 3 . 1 ) 9 ; ( 4 ) 435 9 2 , 106 Willson, C.G. ( 4 ) 98 Willson, J.M. ( 3 . 4 ) 7 8 ; Wroblenski, J. ( 1 ) 240; ( 3 . 6 ) 155

Wilson, B.A. ( 2 . 2 ) 92 Wilson, J.R.H. ( 3 . 2 ) 33 Wilson, P. ( 3 . 2 ) 1 , 1 3 7 ; ( 3 . 6 ) 107, 206 (3.7) 13, 1 4 , 24 Wilson, W.L. ( 1 ) 438 Wilzbach, K.E. ( 3 . 4 ) 21 Winders, J . A . ( 3 . 1 ) 30 Windisch. H. ( 1 ) 407 Windsor, M.W. ( 1 ) 205 Winefordner, J.D. ( 1 ) 2 1 , 425 Wink, D.A. ( 2 . 2 ) 122 Winnik, M.A. ( 1 ) 264; ( 4 ) 202, 235, 248 Winscom, C.J. ( 2 . 1 ) 41 Winslow, F . H . ( 4 ) 352 Wintermeyer, W. ( 1 ) 397 Wintgens, V. ( 1 ) 9 4 ; ( 4 ) 444 Wirth, M . J . ( 1 ) 17 Wirz, J. ( 1 ) 1 0 3 ; ( 3 . 2 ) 1 2 9 ; ( 3 . 7 ) 25 Withnall, R. ( 2 . 3 ) 51 Witkop, B. ( 3 . 2 ) 140;

Wilson, R.M.

Yablonskaya, E.E. ( 5 ) 144 Yabuta, M. ( 2 . 1 ) 244; ( 5 ) 202

Yaegashi, H. ( 3 . 3 ) 131 Yaghmour, H. ( 4 ) 408 Yagi, M. ( 1 ) 430 Yakota, N. ( 3 . 3 ) 117 Yakovlev, V.N. ( 2 . 3 ) 57 Yakshin, V.V. ( 2 . 1 ) 222 Yakunichev, M.V. ( 5 ) 208 Yamabe, T. ( 2 . 2 ) 56 Yamada, A. ( 2 . 1 ) 1 2 0 , 231; ( 5 ) 9 0 , 1 5 3 , 154

Yamada, J. ( 3 . 2 ) 8 3 , 85 Yamada, S . ( 3 . 4 ) 1 5 , 1 8 4 ;

(3.6) 44, 145; ( 3 . 7 ) 1 8 4 , 185 Yamada, T. ( 3 . 5 ) 8 2 ; ( 3 . 6 ) 97 Yamada, Y. ( 2 . 1 ) 1 8 1 ; ( 2 . 2 ) 71 Yamaguchi, K. ( 3 . 5 ) 65 Yamaguti, K. ( 2 . 1 ) 3 1 ; ( 5 ) 1 8 3 , 184 Yamakawa, T, ( 5 ) 80 Yamakita, H. ( 3 . 3 ) 9 5 ; ( 5 ) 53 Yamamoto, A. ( 3 . 6 ) 147 Yamamoto, H. ( 2 . 2 ) 1 1 8 ; (3.4) 184; (3.6) 1 4 , 4 4 ; ( 5 ) 75 Yamamoto, I. ( 3 . 6 ) 150 Yamamoto, K. ( 3 . 3 ) 10; ( 4 ) 2 3 3 , 449 Yamamoto, M. ( 1 ) 2 6 3 ; (3.3) 120; (3.6) 92; ( 3 . 3 ) 26 ( 4 ) 234 Wronka, J. ( 2 . 2 ) 10 Yamamoto, R. ( 4 ) 449 Wu, E.S. ( 4 ) 2 3 0 , 237 Wu, G. ( 3 . 1 ) 5 ; ( 3 . 3 ) 127 Yamamoto, S . ( 3 . 2 ) 1 1 6 , 117; (3.6) 9 Wu, S . ( 3 . 5 ) 80, 1 4 7 , 1 4 8 ; ( 4 ) 106 Yamamoto, Y. ( 2 . 1 ) 2 4 , 171; ( 4 ) 1 9 ; ( 5 ) 165, wu, ( 3 . 3 ) 11 WU, Z.-Z. ( 1 ) 8 6 ; ( 3 . 4 ) 173 Yamane, K. ( 3 . 2 ) 1 5 6 ; 5 8 ; ( 3 . 6 ) 1 4 2 , 143 Wubbels, G.G. ( 3 . 4 ) 6 2 , ( 3 . 4 ) 4 9 ; ( 3 . 6 ) 109 Yamanouchi, K . ( 3 . 2 ) 110 6 4 ; (3.6) 74 Wyssbrod, H.R. ( 1 ) 3 3 3 , Yamaoka, M. ( 4 ) 284 Yamaoka, T. ( 4 ) 4 , 9 334 Yamashita, K. ( 1 ) 2 6 3 ; ( 2 . 1 ) 145 Yamashita, M. ( 2 . 1 ) 123 Xiao, X. ( 2 . 1 ) 2 3 7 ; ( 3 . 5 ) Yamashita, S . ( 1 ) 4 3 6 ; 5 7 ; ( 5 ) 65 ( 4 ) 209; ( 5 ) 159 Xie, X. ( 4 ) 155 Yamashita, T. ( 3 . 4 ) 5 5 ; Xu, B. ( 3 . 5 ) 1 4 7 , 148 ( 3 . 6 ) 131 Xu, D. ( 3 . 5 ) 1 4 7 , 148 Yamashita, Y. ( 3 . 3 ) 1 3 1 ; XU, H. ( 2 . 1 ) 2 2 0 , 236( 3 . 4 ) 8 2 ; ( 3 . 6 ) 134 238; ( 3 . 5 ) 1 9 ; ( 5 ) 6 5 , Yamashito, H. ( 1 ) 215 67 Yamauchi, R. ( 3 . 5 ) 82 Xu, H . J . ( 1 ) 306 Yamauchi, S . ( 1 ) 1 2 2 , 441 Xu, J. ( 3 . 1 ) 5 Yamauchi, T. ( 3 . 2 ) 29 Xue, F. ( 3 . 6 ) 63 Yamazaki, H. ( 2 . 1 ) 1 7 1 ;

w.

Author Index ( 2 . 2 ) 5 1 , 116, 129; ( 3 . 3 ) 103; ( 5 ) 48 Yamazaki, I . ( 1 ) 3 5 , 259 Yamazaki, T. ( 3 . 2 ) 9 2 ; ( 3 . 6 ) 18 Yamazaki, Y. ( 1 ) 259 Yan, R. ( 2 . 2 ) 105; ( 3 . 6 ) 63 Yanagida, S . ( 3 . 3 ) 130; ( 3 . 5 ) 53 Yanagisawa, T. ( 4 ) 422 Yang, C . S . ( 2 . 2 ) 6 2 , 63 Yang, F. ( 4 ) 116 Yang, N.C. ( 1 ) 175; ( 3 . 3 ) 107; ( 3 . 4 ) 44 Yang, Y, ( 4 ) 106 Yanuck, M.D. ( 5 ) 136 Yarmolenko, N.S. ( 3 . 2 ) 44 Yaroshenko, N.I. ( 3 . 5 ) 85 Yarrazaki, M. ( 4 ) 302 Yartsev, V.P. ( 4 ) 426 Yashioka, T. ( 4 ) 396 Yashirin, A.V. (49 429 Yasuda, M. ( 3 . 4 ) 55; ( 3 . 6 ) 131 Yasuda, S . ( 3 . 5 ) 140; ( 3 . 6 ) 156 Yasufuku, K. ( 2 . 2 ) 49-51, 5 9 , 113, 115, 116; ( 5 ) 48 Yates, K. ( 3 . 4 ) 106; ( 3 . 5 ) 52 Yates, P. ( 3 . 1 ) 2 1 , 23 Yau, H.J. ( 4 ) 360 Ye, D. ( 4 ) 4 9 , 50 Yeates, S . ( 1 ) 420 Yersin, H. ( 2 . 1 ) 81 Yesaka, H. ( 2 . 2 ) 49 Ygge, B. ( 3 . 2 ) 101 Yguerabide, J. ( 1 ) 356 Yi, H. ( 4 ) 116 Yijun, C. ( 2 . 2 ) 25 Yip, R.W. (1) 1 3 , 8 6 ; ( 3 . 5 ) 10; ( 3 . 6 ) 7 2 , 142 Yo, A. ( 4 ) 131 Yokoyama, K. ( 3 . 2 ) 110; ( 3 . 4 ) 6 2 , 83 Yoneda, R. ( 2 . 1 ) 29; ( 5 ) 176 Yonemitsu, 0. ( 3 . 5 ) 54; ( 3 . 6 ) 154 Yonemura, M. ( 2 . 1 ) 38 Yonezawa, T. ( 2 . 2 ) 56 Yonezawa, Y. ( 5 ) 198, 199 Yoon, S . K . ( 3 . 2 ) 1 2 ; ( 3 . 6 ) 93 Yoshi, F. ( 4 ) 272 Yoshida, A . ( 3 . 2 ) 41 Yoshida, C. ( 3 . 4 ) 9 6 ; ( 3 . 7 ) 147 Yoshida, E. ( 3 . 6 ) 179, 181

591 Yoshida, H. ( 2 . 3 ) 1 5 ; ( 3 . 4 ) 1 9 0 ; ( 3 . 6 ) 201, 202 Yoshida, K. ( 3 . 4 ) 8 2 ; ( 3 . 6 ) 134 Yoshida, M. ( 3 . 1 ) 4 7 ; ( 3 . 4 ) 150 Yoshida, N. ( 1 ) 135 Yoshida, T. ( 2 . 2 ) 117; ( 3 . 6 ) 39 Yoshida, Z. ( 5 ) 41 Yoshifuji, M. ( 2 . 2 ) 29 Yoshihara, K. ( 1 ) 234, 444; ( 3 . 3 ) 28 Yoshihara, N. ( 3 . 1 ) 4 1 ; ( 3 . 6 ) 75 Yoshimi, Y. (1) 83 Yoshino, K. ( 3 . 5 ) 53 Yoshioka, K. ( 3 . 5 ) 107 Yoshioka, M. ( 3 . 2 ) 121, 122 Yosufuku, K. ( 3 . 3 ) 103 Young, A.L. ( 4 ) 326 Young, D.W. ( 3 . 6 ) 169 Youngs, W.J. ( 3 . 3 ) 116 Yu, H.S. ( 4 ) 254 Yu, W.C. ( 4 ) 232 Yuan, L.C. ( 2 . 1 ) 52 Yuasa, S. ( 3 . 5 ) 25 Yue, P.L. ( 5 ) 18 Yughakova, O.A. ( 4 ) 56 Yukitani, M. ( 4 ) 390 Yumoto, T. ( 3 . 3 ) 9 5 ; ( 3 . 6 ) 150; ( 5 ) 53 Yun, H.C. ( 3 . 4 ) 183; ( 3 . 6 ) 45 Yun, S.S. ( 2 . 1 ) 208 Yurek, E. ( 3 . 4 ) 8 4 ; ( 3 . 6 ) 208 Yutani, Y. ( 4 ) 62

17

Zarate, E.A. ( 3 . 3 ) 116 Zard, S.Z. (3.7) 114-116 Zastrow, A. ( 5 ) 234 Zavoduik, V.E. ( 4 ) 56 Zawadzki, Z. ( 3 . 2 ) 97 Zayas, J. ( 3 . 7 ) 5 5 , 90 Zayed, M.F. ( 3 . 5 ) 132 Zeiri, L. ( 1 ) 104 Zelent, B . ( 3 . 5 ) 138 Zellweger, D. ( 3 . 7 ) 70 Zengerle, K. ( 5 ) 62 Zerilli, L. ( 3 . 5 ) 119 Zet, Y.Z. ( 1 ) 192 Zeug, N. ( 2 . 1 ) 242; ( 5 ) 73

Zewail, A.H. ( 3 . 3 ) 2 0 ; ( 5 ) 131

Zhang, B. ( 3 . 3 ) 1 1 ; ( 3 . 5 ) 8 0 , 8 7 , 109

Zhang, C. ( 4 ) 107, 398 Zhang, F. ( 2 . 1 ) 204 Zhang, J. ( 4 ) 217; ( 5 ) 177

Zhang, L. ( 2 . 2 ) 7 4 ; ( 3 . 5 ) 57; ( 4 ) 116

Zhang, P. ( 4 ) 12 Zhang, R. ( 2 . 1 ) 220 Zhang, S. ( 2 . 1 ) 223 Zhang, X. ( 2 . 1 ) 220 Zhang, Y. ( 4 ) 85 Zhang, Z. ( 4 ) 60; ( 5 ) 177 Zhao, R. ( 3 . 6 ) 63 Zhen, Z. ( 1 ) 306 Zhi, L. ( 3 . 5 ) 80 Zhil'tsova, E.E. ( 2 . 2 ) 27 Zhon, X. ( 4 ) 399 Zhou, B. ( 1 ) 274; ( 3 . 7 ) 131

Zhou, Q. ( 2 . 1 ) 236, 238; ( 5 ) 67

Zabala, F.T.I. ( 1 ) 318 Zabara, M.Ya. ( 4 ) 431, 455

Zachariasse, K . A . (1) 149, 310

Zacmanidis, P. ( 1 ) 411 Zahir, K. ( 2 . 1 ) 95 Zahn, K. ( 2 . 1 ) 108 Zai, L. ( 4 ) 116 Zaitsev, V.N. ( 1 ) 338 Zakov, A . N . ( 4 ) 274 Zakrzewski, A. ( 4 ) 144 Zamaraev, K . I . ( 5 ) 1 , 2 Zamotaev, P.V. ( 4 ) 153, 315

Zamzam, S.A. ( 4 ) 250 Zana, R. ( 1 ) 282, 284, 287

Zander, M. ( 1 ) 432, 433 Zang, G. ( 3 . 3 ) 128; ( 3 . 7 )

Zhou, Q.F. ( 4 ) 260 Zhou, Y. ( 3 . 6 ) 122 Zhou, Z. ( 2 . 1 ) 220 Zhu, C. ( 3 . 5 ) 88 Zhu, J. ( 3 : 2 ) 46 Zhu, L. ( 4 ) 399 Zhu, P. ( 2 . 3 ) 11 Zhu, Q. ( 2 . 3 ) 47 Zhu, Y. ( 2 . 1 ) 237; ( 5 ) 65 Zhuravlev, M.A. ( 4 ) 324 Ziada, B . A . ( 5 ) 239 Zielenkiewicz, W. ( 1 ) 435 Zielinski, S . (5) 196 Ziessel, R. ( 2 . 1 ) 124 Zilber, 0. ( 4 ) 349 Zilinskas, B.A. ( 1 ) 382 Zimmermann, G. ( 3 . 2 ) 103 Zimmermann, H.E. ( 3 . 1 ) 52; (3.2) 73, 74; (3.3 4 0 , 6 0 , 61 Zimmt, M.B. ( 1 ) 143, 144

Author Index

592 304, 464, 492; ( 3 . 1 ) 7 , 27; ( 3 . 4 ) 1 8 7 ; ( 3 . 5 ) 22 Zimnyakov, A . M . ( 2 . 1 ) 91 Zinth, W. ( 1 ) 378 Zisk, M.B. ( 3 . 5 ) 30; (5) 87 Zlatkevich, L. ( 4 ) 283

ZU, Q.-Y. ( 1 ) 366 Zubanev, V.E. ( 4 ) 51 Zubov, V.P. ( 4 ) 1 1 8 , 119 Zuchowcz, I. ( 4 ) 290 Zuev, P.s. ( 3 . 7 ) 5 Zumbrunnen, H.R. ( 5 ) 228

Zumofen, G. ( 1 ) 249 Zupan, M. ( 3 . 4 ) 4 1 ; ( 3 . 7 ) 118 Zupancic, J.J. ( 3 . 7 ) 44 Zupancic, N. ( 3 . 4 ) 4 1 ; ( 3 . 7 ) 118 Zwanenburg, B. ( 3 . 2 ) 7

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