Organic Photochromic andThermochromic CompoundsVolume 2: Physicochemical Studies,Biological Applications, andThermochromism

TOPICS IN APPLIED CHEMISTRYSeries Editors: Alan R. Katritzky, FRS

University of FloridaGainesville, Florida

3M CompanySt. Paul, Minnesota

Current volumes in the series:ANALYSIS AND DEFORMULATION OFPOLYMERIC MATERIALSPaints, Plastics, Adhesives, and InksJan W. GoochCHEMISTRY AND APPLICATIONS OF LEUCO DYESEdited by Ramaiah MuthyalaFROM CHEMICAL TOPOLOGY TO THREE-DIMENSIONALGEOMETRYEdited by Alexandru T. BalabanLEAD-BASED PAINT HANDBOOKJan W. GoochORGANIC PHOTOCHROMIC AND THERMOCHROMICCOMPOUNDSVolume 1: Main Photochromic FamiliesVolume 2: Physicochemical Studies, Biological Applications,and ThermochromismEdited by John C. Crano and Robert J. GuglielmettiORGANOFLUORINE CHEMISTRYPrinciples and Commercial ApplicationsEdited by R. E. Banks, B. E. Smart, and J. C. TatlowPHOSPHATE FIBERSEdward J. GriffithPOLY(ETHYLENE GLYCOL) CHEMISTRYBiotechnical and Biomedical ApplicationsEdited by J. Milton HarrisRESORCINOLIts Uses and DerivativesHans DresslerA Continuation Order Plan is available for this series. A continuation order will bring delivery of each newvolume immediately upon publication. Volumes are billed only upon actual shipment. For further informa-tion please contact the publisher.

Gebran J. Sabongi

Organic Photochromic andThermochromic CompoundsVolume 2: Physicochemical Studies,Biological Applications, andThermochromism

Edited by

John C. CranoLate of PPG Industries, Inc.Monroeville, Pennsylvania

and

Robert J. GuglielmettiUniversity of Aix-Marseille IIMarseille, France

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In Memoriam

DR. JOHN C. CRANO

On January 10, 1998, Dr. John C. Crano, 62, one of the co-editors of thisbook, and his wife Dorothy were killed instantly in an automobile accident inFlorida. In this tragic death the world of photochromism has lost the person chieflyresponsible for the success of the largest commercial application of organicphotochromics.

Dr. Crano received a B.S. degree in Chemistry in 1957 from Notre Dame andM.S. and Ph.D degrees from Case Western Reserve University in 1959 and 1962,respectively. He joined PPG Industries in 1961, and spent his entire career withthat firm, at first in various roles in the Chemical Research and Development area.In 1974 PPG began research, upon means to impart photochromic properties toophthalmic lenses made from plastics, in particular from poly(allyl diglycolcarbonate), CR-39®. Plastic lenses command over 85% of the total ophthalmicmarket in the US, principally because a lightweight plastic product is morecomfortable to wear and permits more attractive fashion designs.

Comparative testing of all classes of photochromics, including inorganiccompounds, indolinospirobenzopyrans and naphthoxazines, occupied the first fewyears. In the early 1980s expanding research and development efforts focusedupon the indolinospirobenzoxazines and quinolinooxazines and their close struc-tural relatives. In 1986 Dr. Crano became leader of a constantly enlarging team oforganic, physical, polymer, and photo-chemists, and engineers. The first genera-tion plastic photochromic ophthalmic lenses, the Transitions® Comfort Lens,were manufactured in Ohio and test-marketed in June of 1989. TransitionsOptical, Inc., a joint venture between PPG and the French lens manufacturerEssilor, was formed in 1990 and began manufacturing lenses early in 1991 in anew plant in Florida.

A second generation lens, the Transitions® Plus lens, was introduced inNovember 1992. In the years since, Transitions Optical has marketed a successionof new lenses. In September 1994 the EuroBrown™ lens appeared, formulated togive when activated a brown color, especially favored in the European market. Themid-index Transitions® III lenses were launched in the United States and inEurope during 1996, and the Transitions XTRActive™ lenses were introduced in

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vi In Memoriam

the US in January 1997. The most recently introduced lenses are Transitions® IIIlenses in a standard index matrix. These use the latest technology in organicphotochromic dyestuffs and polymer science and engineering, and maintain thecompany’s position of technical leadership in the field of plastic ophthalmicphotochromic lenses. Transitions Optical now sells its various lenses in over 50countries.

In his position as Associate Director of Research and Development, OpticalProducts, Dr. Crano managed the entire photochromics research program. He ledthe team of scientists that synthesized and evaluated hundreds of candidatephotochromic dyestuffs, and directed all of the product and process developmentinvolved in the various Transitions® lenses. In addition, his responsibilitiesincluded R&D on non-ophthalmic photochromic applications, and on otheroptical coatings and resins.

He has a number of US patents in various areas of technology, including threeduring 1990–1992 that cover the basic compositions and methods for producingthe first generation of Transitions® lenses. These were important in establishing astrong proprietary position in photochromic plastic ophthalmic lenses. In addition,he had published several reviews and invited lectures on photochromism andphotochromic polymers.

In 1985 he was General Chairman of the Central Regional Meeting of theAmerican Chemical Society, and in September 1996 he was Co-Chairman of the2nd International Symposium on Photochromism. This Symposium, whichincluded participants from 16 countries, owed much of its success to Dr. Crano’sexcellent organization.

Recent Publications andPresentations of J. C. CranoPhotochromic Systems for Plastic Ophthalmic Lenses, J. C. Crano, 1997 GordonConference on Organic Photochemistry.

Photochromic Compounds: Chemistry and Application in Ophthalmic Lenses, J.C. Crano, T. Flood, D. Knowles, A. Kumar, and B. Van Gemert, Pure Appl. Chem,68(7), 1395–1398 (1996).

Photochromic Materials, John C. Crano, in “Kirk-Othmer Encyclopedia ofChemical Technology,” 4th Edn., 1993, J. Wiley & Sons, New York.

Photchromic Organic Compounds in Polymer Matrices, J. C. Crano, C. N. Welch,B. Van Gemert, D. Knowles and B. Anderson, in “Photochemistry and PoymericSystems” J. M. Kelly, C. B. McArdle and M. J. de F. Maunder, Eds., 1993, RoyalSociety of Chemistry, Cambridge.

Spirooxazines and Their Use in Photochromic Lenses, J. C. Crano, W. S. Kwakand C. N. Welch, in “Applied Photochromic Polymer Systems” C. B. McAedle,Ed., 1992, Blackie ans Sons.

R. Guglielmetti and R. Bertelson

viii

ContributorsAngelo Alberti, I.Co.C.E.A.—CNR, 40129 Bologna, Italy

Serguei Aldoshin, Institute of Chemical Physics, Russian Academy of Sciences,142432 Chernogolovka, Russia

Jean Aubard, Institut de Topologie et de Dynamique des Systèmes, UniversitéDenis Diderot, Paris, France

M. H. Deniel, Lab. I.M.C.R.P., UMR 5623 au CNRS, Paul Sabatier University,F-31062 Toulouse, France

Kunihiro Ichimura, Research Laboratory of Resources Utilization, TokyoInstitute of Technology, Yokohama 226-8503, Japan

Masahiko Inouye, Department of Applied Materials Science, Osaka PrefectureUniversity, Sakai, Osaka 593, Japan

D. Lavabre, Lab. I.M.C.R.P., UMR 5623 au CNRS, Paul Sabatier University,F-31062 Toulouse, France

Vladimir Lokshin, Université de la Méditerranée, Faculté des Sciences Luminy,ESA 6114 CNRS, 13288 Marseille Cedex 9, France

Klaus Lorenz, Department of Organic Chemistry, University of Regensburg,D-93040 Regensburg, Germany

V. Malatesta, Great Lakes Chemical Italia, Via Maritano 26, 20097 S. Donato(MI), Italy

Albrecht Mannschreck, Department of Organic Chemistry, University ofRegensburg, D-93040 Regensburg, Germany

J. C. Micheau, Lab. I.M.C.R.P., UMR 5623 au CNRS, Paul Sabatier University,F-31062 Toulouse, France

ix

x Contributors

Shinichiro Nakamura, Yokohama Research Center, Mitsubishi ChemicalCorporation, Yokohama 227, Japan

André Samat, Université de Méditerranée, Faculté des Sciences Luminy, ESA6114 CNRS, 13288 Marseille Cedex 9, France

Michael Schinabeck, Department of Organic Chemistry, University of Regens-burg, D-93040 Regensburg, Germany

ForewordExperiments showing a rapid and reversible change of color seem like magic andare always fascinating. The process involved, photochromism, has a few real andmany potential applications. Photochromic glasses that darken in the sunlight(protecting eyes from excessive light intensity) and bleach in dim light are today apart of everyday life. Organic photochromic compounds in plastic ophthalmiclenses, more comfortable to wear, are now competing with silver salts in glasses,despite the longer lifetime of the inorganic system. This successful commercialapplication has given a new impetus to research in the general field of photo-chromism, which had its most recent revival in the early eighties.

The story of organic photochromism with its ups and downs, from thebreakthroughs of the pioneering period in the fifties, through the hard times due tothe drawbacks of photodegradation, to the recent successes is in many ways asaga. The upsurges in this domain were marked by an increasing flow of articles inscientific journals and the publication of several books (in 1971, 1990, and 1992)that have collected the important accumulated knowledge. Over this period, aconsiderable number of patents have been issued. International meetings haveaccompanied this activity, the most recent being held in 1993 (ISOP-93 at LesEmbiez Island, France) and in 1996 (ISOP-96 in Clearwater, Florida). Remark-ably, these meetings had good representation from both academia and industry.The next ISOP is planned for 1999 in Fukuoka, Japan.

Since publication of the most recent books, new areas have been explored anda large number of new results have been obtained, and it seemed, therefore, timelyto publish them. This was the endeavor of the chairmen of ISOP-93 and ISOP-96,Robert Guglielmetti and John Crano, respectively, who have acted as coeditors.R. Guglielmetti, a professor at the University of Marseilles, is a recognized leaderin the field, and the late Dr. J. Crano Associate Director of Research andDevelopment for optical products at PPG Industries since 1986, led research inthe development of plastic ophthalmic eyewear. The efficient cooperation of ascholar and an industrial scientist has led to the publication of Organic Photo-chromic and Thermochromic Compounds in two volumes of about 400 pages each.

Volume 2 includes ten chapters, of which six are devoted to physicochemicalmethods applied to the investigation of photochromism and four address somespecific topics selected for their wide interest. Nine out of the ten main authorshave not written chapters for previous books, and two are from companies. Theliterature has been reviewed to 1995–1997.

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xii Foreword

Physicochemical methods have been referred to in preceding books, but, inthis volume, systematic studies have been carried out with the same method ondifferent classes of photochromic compounds: kinetics under continuous irradia-tion, electronic paramagnetic resonance (EPR), molecular modeling, X-raydiffraction, Raman studies [particularly surface-enhanced resonance Raman spec-troscopy (SERRS)], and chirality and photochromism (contributing to a betterunderstanding of the ring opening of spiro compounds). The authors are amongthe leading specialists in their respective fields.

The other specific topics are: (i) the influence of various types of matrices(polymer, liquid crystal, Langmuir–Blodgett (LB) films, sol-gel) on the behaviorof photochromic systems (spiropyrans, azobenzenes, viologens, and fulgides);(ii) the study of photodegradation mechanisms, an important topic—given that theso-called “fatigue” is the genetic disease of all organic materials—that has onlyrecently been methodically tackled; (iii) the application of photochromic mole-cules to the reversible control of peptide and protein conformation, antigen–antibody reactions, and the cation-binding affinity of complexing agents that differfrom the photochromic biological systems (e.g., rhodopsins, phytochromes) whichare not dealt with in this book; and (iv) last but not least, thermochromism oforganic compounds, stressing its structural and mechanistic aspects.

It is clear that this volume is truly different from the preceding accounts.Photochemists will appreciate Volume 2 as a nice complement to Volume 1,although it can be read independently. Organic photochromic systems are knownfor their applications in variable-transmission optical materials, ophthalmic lenses,authentification devices (photochromic inks), and novelty items, but they alsohave great potential in any domain where reversible physical properties are desired(optical memories, gradation masking, optoelectronic systems, nonlinear opticaldevices, etc.). This book is thus strongly recommended to anyone interested inmaterials science.

Henri Bouas-LaurentUniversity Bordeaux 1

PrefaceOrganic Photochromic and Thermochromic Compounds, of which this book is thesecond volume, is the fourth major treatise on photochromism involving organicmolecules and derived systems. The first such book, edited by G. H. Brown, waspublished in 1971 as a volume in the Weissberger series, and the second, edited byH. Dürr and H. Bouas-Laurent, was published in 1990 in the Elsevier series.2 Tothis list should be added a third book, edited by C. B. McArdle,3 which focuses onthe very important topic of the behavior of photochromic systems in polymermatrices.

The two volumes of this new treatise are an outgrowth of the large increase inthe number of publications and patents concerning photochromic compounds andtheir use in various applications (e.g., ophthalmic lenses, security printing, etc.)during the past 10 years. As a result of this increased interest, two successfulInternational Symposia on Photochromism (ISOP) have been held: ISOP-93, heldin France on Les Embiez Island near Bandol (September 12–16, 1993), and ISOP-96, held in the United States in Clearwater, Florida (September 8–12, 1996). Thenumber of countries represented at each of these symposia (17 and 16, respec-tively) attests to the international scope of the photochromic research community.This global interest is also exemplified by the authors of the chapters within thisbook.

The second volume of this new treatise is focused on the physicochemicalproperties and photochromic behavior of the best known systems. We haveincluded chapters on the most appropriate physicochemical methods by whichphotochromic substances can be studied (spectrokinetic studies on photostationarystates, Raman spectroscopy, electron paramagnetic resonance, chemical computa-tions and molecular modeling, and X-ray diffraction analysis). In addition, specialtopics such as interactions between photochromic compounds and polymermatrices, photodegradation mechanisms, and potential biological applicationshave been treated. A final chapter on thermochromic materials is included toemphasize the chemical similarities between photochromic and thermochromicmaterials. In general, the literature cited within the chapters covers publicationsthrough 1995. However, in several cases, publications from as late as 1997 areincluded.

Our thanks go to all the colleagues who volunteered to collaborate on thisbook and who had the patience and perseverance to undertake all the steps

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xiv Preface

required to prepare the final manuscripts. In addition to the chapter authors,several other people have contributed their time and talent. Dr. A. Samat and Dr. V.Lokshin (Laboratory of Organic Chemistry and Materials, Marseille) must beacknowledged for many fruitful discussions throughout the process of puttingtogether the book. We are deeply indebted to Diana Gronholm, PPG Industries,Inc., whose help in the revision and copying of manuscripts, communication withcontributors and the publisher, and a variety of other tasks during the preparationof the book was invaluable. Dr. Anil Kumar, also with PPG, helped with theconversion of files into usable program formats and provided technical assistancein the preparation of files for the final manuscripts. Finally, we express ourappreciation to Audrey Anderson, Denise Callihan, and Beverly Weston at PPGIndustries for obtaining missing titles of several references and providing generalassistance when it was needed to verify details of references.

1. G. H. Brown (ed.), Photochromism (Techniques of Chemistry. Vol. III), Wiley-Inter-science, New York (1971).

2. H. Dürr and H. Bouas-Laurent (eds.), Photochromism: Molecules and Systems, Elsevier,Amsterdam (1990).

3. C. B. McArdle (ed.) Applied Photochromic Polymer Systems, Blackie, New York (1992).

J. C. Crano and R. Guglielmetti

Contents

Introduction

1.2.3.4.5.

Aim and Organization of the Book. . . . . . . . . . . . . . . . . . . . . . . .Brief Historical Survey of Photochromism. . . . . . . . . . . . . . . . . . .Definitions of Photochromism . . . . . . . . . . . . . . . . . . . . . . . . . . .Brief Overview of the Chapters in the Book. . . . . . . . . . . . . . . . . .Conclusion and Future Developments . . . . . . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Photochromic Polymers

Kunihuro Ichimura

1.1.1.2.

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Photochromism in Polymer Matrices . . . . . . . . . . . . . . . . . . . . .1.2.1.1.2.2.

Synthesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Matrix Effect on Photochromism . . . . . . . . . . . . . . . . . . .1.2.2.1.1.2.2.2.1.2.2.3.1.2.2.4.1.2.2.5.

Spiropyrans and Related Compounds. . . . . . . . . .Azobenzenes. . . . . . . . . . . . . . . . . . . . . . . . . .Viologens. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fulgides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Photochromism in Sol-Gel Inorganic Matrices . . . .

1.2.3. Polarization Photochromism in Polymer Solids. . . . . . . . . .1.2.3.1.1.2.3.2.1.2.3.3.

Background . . . . . . . . . . . . . . . . . . . . . . . . . . .Polymers Doped with Photochromic Compounds. . .Polymers with Covalently BoundPhotochromic Units . . . . . . . . . . . . . . . . . . . . . .

1.3 Photochromic Liquid-Crystalline Polymers . . . . . . . . . . . . . . . . .1.3.1. Photochromism in Polymeric Mesophases . . . . . . . . . . . . .

1.3.1.1.1.3.1.2.

Nematic and Smectic Phases . . . . . . . . . . . . . . . .Cholesteric Phases . . . . . . . . . . . . . . . . . . . . . . .

1.3.2 Polarization Photochromism of Liquid-CrystallinePolymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

122478

91111151516182021242424

2631313134

35

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xvi Contents

1.4. Surface Photochromism for Regulation of Liquid-CrystalAlignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.4.1.1.4.2.

1.4.3.

Surface-Assisted Liquid-Crystal Alignment Control . . . . . . .Out-of-Plane Alignment Photocontrol . . . . . . . . . . . . . . . .1.4.2.1.1.4.2.2.

Spin-Coated Films.. . . . . . . . . . . . . . . . . . . . . . .Polymeric Langmuir–Blodgett Films.. . . . . . . . . . .

In-Plane Alignment Photocontrol.. . . . . . . . . . . . . . . . . . .1.5. Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Appendix. Preparation of Photochromic Polymers . . . . . . . . . . . . . . . .

A.1.

A.2.A.3.A.4.

Polymethacrylates Substituted withSpiroindolinebenzothiopyrans (5) . . . . . . . . . . . . . . . . . . . .Polymethacrylates with Spirofluorenylindolizines ... . . . . . . . . .Poly[4´-[[2-acryloyloxyethyl]ethylamino]-4-nitroazobenzene] (12)An Ionene Polymer Incorporating Viologen Units (17) . . . . . .

References.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3939404044475052

5253535354

65

6667686870747575

77

81828484848489939697

2. Photodegradation of Organic Photochromes

V. Malatesta

2.1.2.2.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Properties and Reaction Mechanism(s) of Spiropyrans andSpirooxazines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2.1.2.2.2.2.2.3.2.2.4.

Multiplicity of the Photoreactive State . . . . . . . . . . . . . . . .The cis-cisoïd X Isomer . . . . . . . . . . . . . . . . . . . . . . . . .Nitro-Substituted Spiropyrans, . . . . . . . . . . . . . . . . .Unsubstituted Spiropyrans and Spirooxazines . . . . . . . . . . .

2.3.2.4.

Colorability and Photostability (Photocoloration Quantum Yields) . .Photo- and Thermal Degradation of Photochromes . . . . . . . . . . . .2.4.1.2.4.2.

2.4.3.

2.4.4.2.4.5.

Degradation of Spiropyrans: General Approach . . . . . . . . . .Photodegradation: Dependence on the Nature andPosition of the Substituent . . . . . . . . . . . . . . . . . . . . . . . .Substituents on the Indoline Moiety of Spiropyrans:Inductive and Mesomeric Effects . . . . . . . . . . . . . . . . . . .Substituents on the Indoline Moiety. . . . . . . . . . . . . . . . . .Substituents on the Chromene Moiety of Spirobenzopyrans. .2.4.5.1.2.4.5.2.2.4.5.3.2.4.5.4.

Monosubstituted Compounds . . . . . . . . . . . . . . . .Disubstituted Compounds. . . . . . . . . . . . . . . . . . .C3-Substituted Spiropyrans. . . . . . . . . . . . . . . . . .Substituents on N and C3´ . . . . . . . . . . . . . . . . . .

2.5.2.6.

Photodegradation of Benzothiazolinospiropyrans . . . . . . . . . . . . . .Saturated Five-Membered Ring Azaheterocyclic Spiropyrans. . . . .2.6.1. Pyrrolidine Series . . . . . . . . . . . . . . . . . . .

Contents xvii

2.6.2.2.6.3.

Thiazolidine Series (X=S). . . . . . . . . . . . . . . . . . . . . . . .Oxazolidine Series (X=O). . . . . . . . . . . . . . . . . . . . . . . .

99999999

111

111115115115119119

124136141143143147147148151

153164

167

170170

172

173174

175

2.7.2.8.2.9.

Saturated Six-Membered Ring Azaheterocyclic Spiropyrans . . . . . .Spiropyran Degradation: A Quantitative Approach . . . . . . . . . . . .Non-Azaheterocyclic Spiropyrans. . . . . . . . . . . . . . . . . . . . . . . .2.9.1.

2.9.2.2.9.3

6- and 8-Substituted Spirobenzodithiolane andSpirobenzoxathiolane Benzopyran Series. . . . . . . . . . . . . .Spiro[bibenzopyrans] . . . . . . . . . . . . . . . . . . . . . . . . . . .Dithiole Series. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.10.

2.11.

2.12.2.13.

Photodegradation of Spirooxazines. . . . . . . . . . . . . . . . . . . . . .2.10.1.2.10.2.2.10.3.

2.10.4.2.10.5.

Solvent Polarity and Photodegradation. . . . . . . . . . . . . .Structure and Photodegradation . . . . . . . . . . . . . . . . . .Mechanism of Photooxidation of Spirooxazines:Singlet-Oxygen Reactivity. . . . . . . . . . . . . . . . . . . . . .Oxidation in Dark Reactions of Spirooxazines . . . . . . . .Reaction of Merocyanines with Free Radicals . . . . . . . . .

Photodegradation Measurements: Experimental Apparatus . . . . . .2.11.1.2.11.2.2.11.3.2.11.4.

Irradiation Source.. . . . . . . . . . . . . . . . . . . . . . . . . . .Analysis Setup.. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Signal-Conditioning Circuits (SCC).. . . . . . . . . . . . . . .Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Photostability of Fulgides . . . . . . . . . . . . . . . . . . . . . . . . . . . .Commercial Spirooxazines and Chromenes: Relevant Propertiesand Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3. Photokinetics under Continuous Irradiation

M. H. Deniel, D. Lavabre, and J. C. Micheau

3.1.3.2.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Dynamic Analysis of the Isolated Photochemical Step:

3.2.1.3.2.2.

3.2.3.

Establishment of the Photochemical Rate Equation . . . . . . .Photochemical Reactor Uniformly Stirred and Equippedwith a System for UV/Visible Spectroscopic Analysis . . . . .Experimental Verification of the Validity of thePhotochemical Kinetic Equations under ContinuousIrradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.3. AB Systems Involving Two Species . . . . . . . . . . . . . . . . . . . . . .3.3.1. Establishment of the General Kinetic Equation under

Continuous Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xviii Contents

3.3.2.

3.3.3.3.3.4.

Properties of the Photostationary State of the AB, 1kSystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3.2.1.3.3.2.2.

AB, 1k Systems . . . . . . . . . . . . . . . . . . . . . .AB, Systems . . . . . . . . . . . . . . . . . . . . . . . .

Photostationary Methods . . . . . . . . . . . . . . . . . . . . . . . . .Dynamical Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

175176177177177182182183183186190190191194

195195195197198199

202203205

211212212219220224226

226229234236

3.4. ABC Photochromic Systems Involving Three Species . . . . . . . . . .3.4.1.3.4.2.

General Comments. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.4.2.1.3.4.2.2.

Systems with Two Photoisomers . . . . . . . . . . . . . .Photodegradation of a Spiro[indoline-benzopyran] . .

3.5. ABC Systems Exhibiting Nonlinear Behavior. . . . . . . . . . . . . . . .3.5.1.3.5.2.

Ideal ABC System Giving Rise to Bistability . . . . . . . . . . .Photochromism and Photodegradation of TPID . . . . . . . . . .

3.6. Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Appendix 1. Flash Photolysis versus Continuous Irradiation: Influence

on the Accumulation of Reaction Intermediates. . . . . . . . .Appendix 2. Photostationary Methods . . . . . . . . . . . . . . . . . . . . . . . .

A2.1. AB, , 1k Systems . . . . . . . . . . . . . . . . . . . . . .A2.2. AB, 1k Systems . . . . . . . . . . . . . . . . . . . . . .A2.3. AB, Systems . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix 3.Appendix 4.

Appendix 5.

Thermal Relaxation of an ABC System . . . . . . . . . . . . . .Localization of an Elementary Relaxation Process in ABCSystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Localization of a Photodegradation Process . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4. EPR and Radical ProcessesAngelo Alberti

4.1.4.2.

4.3.4.4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Viologens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.2.1.4.2.2.4.2.3.

Radical Cations from the Reduction of Viologens . . . . . . . .Some Particular Viologens. . . . . . . . . . . . . . . . . . . . . . . .EPR of Viologens in Micellar Systems. . . . . . . . . . . . . . . .

Spiroindolinic Photochromes . . . . . . . . . . . . . . . . . . . . . . . . . . .4.4.1.

4.4.2.4.4.3.

Paramagnetic Species in Photochromism andPhotodegradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Radical Ions from Spiro Compounds . . . . . . . . . . . . . . . . .Spin Probes and Spin Traps with a Spiroindolinic Structure. .

References.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents xix

5. Molecular Modeling Calculations

Shinichiro Nakamura

5.1.5.2.5.3.

5.4.

5.5.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Absorption Wavelength and Intensity . . . . . . . . . . . . . . . . . . . . .Thermal Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.3.1.5.3.2.

Photon–Heat Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .Photon–Photon Mode. . . . . . . . . . . . . . . . . . . . . . . . . . .

Reaction Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5.4.1.5.4.2.5.4.3.

Spiropyran Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . .Fulgide Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . .Other Photochromic Systems. . . . . . . . . . . . . . . . . . . . . .

Quantum Yield. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

241241247247249251251253253255256

261263263

263265267269271271

273274274280283284288290292

6. The Enantiomers of 2-Donor-Substituted Benzopyrans andBenzo-1,4-oxazines and Their Thermal Racemization

Albrecht Mannschreck, Klaus Lorenz, and Michael Schinabeck

6.1.6.2.

6.3.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Methods of Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6.2.1.6.2.2.

6.2.3.6.2.4.6.2.5.

Remarks Pertaining to All Methods . . . . . . . . . . . . . . . . .Preparative Enrichment of Enantiomers by EnantioselectiveLiquid Chromatography . . . . . . . . . . . . . . . . . . . . . . . . .Determination of Enantiomeric Purities . . . . . . . . . . . . . . .Assignment of Relative Configurations . . . . . . . . . . . . . . .Measurement of Barriers by Thermal Racemization.. . . . . .

Results of the Thermal Racemizations . . . . . . . . . . . . . . . . . . . .6.3.1.6.3.2.

6.3.3.6.3.4.6.3.5.6.3.6.6.3.7.6.3.8.

Transition State of C(sp3)–O Bond Cleavage. . . . . . . . . . .Remarks Pertaining to All Types of Benzopyrans andBenzo-l,4-Oxazines.. . . . . . . . . . . . . . . . . . . . . . . . . . .2-Aryl-2-methylbenzopyrans . . . . . . . . . . . . . . . . . . . . . .2-Alkoxybenzopyrans.. . . . . . . . . . . . . . . . . . . . . . . . . .Spirobibenzopyrans . . . . . . . . . . . . . . . . . . . . . . . . . . . .Spiro[oxaindane-benzopyrans] . . . . . . . . . . . . . . . . . . . . .Spiro[indoline-benzoxazines]. . . . . . . . . . . . . . . . . . . . . .Spiro[indoline-benzopyrans] . . . . . . . . . . . . . . . . . . . . . .

6.4. Conclusion.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

XX Contents

7. Structural Studies by X-Ray Diffraction

Serguei Aldoshin

7.1.7.2.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Spiropyrans.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

297298298298

303

304

306307312

314

315

315

317

318

320320323324324330333338339343350350

7.2.1.

7.2.2.

7.2.3.

7.2.4.

Indolinospiropyrans. . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.2.1.1.7.2.1.2.

7.2.1.3.

Structural Features of SP Molecules. . . . . . . . . . . .The Nature of Structural Changes in SP Moleculesupon Photoexcitation. . . . . . . . . . . . . . . . . . . . . .Effect of the Nature and Position of Substituentsin SP Molecules on the Length of the Cspiro–OBond . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Structure of Permanent Merocyanines—Models of theOpen Forms of Indolinospiropyrans. . . . . . . . . . . . . . . . . .7.2.2.1.7.2.2.2.7.2.2.3.

Molecular Structure of Merocyanines . . . . . . . . . . .Geometric Isomers of Merocyanine Forms . . . . . . .Nature of the Molecular Packing and Energy ofIntermolecular Interactions in MerocyanineCrystals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Effect of the Nature of Heteroatoms in the Spiro Centeron the Structure and Photochemical Properties ofSpiropyrans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.2.3.1.

7.2.3.2.

7.2.3.3.

Structural Features of Indoline SpirothiopyransContaining S and N Heteroatoms in the SpiroCenter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Structure of “Symmetrical” Spiropyrans Consistingof Two Benzopyran Fragments . . . . . . . . . . . . . . .Structure of the First Representative of Spiro-2H-Naphtho[l,8-bc]oxepins (SPNO) . . . . . . . . . . . . . .

2-Oxaindan Spiropyrans with Polycondensed ChromeneFragments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.2.4.1.7.2.4.2.7.2.4.3.

Structure of 2-Oxaindan Spiropyrans . . . . . . . . . . .Thermal Valence Isomerization of SPs . . . . . . . . . .Photochromism of 2-Oxaindan Spiropyrans . . . . . . .

7.3.7.4.7.5.7.6.

7.7.

Spirooxazines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Photochromic [2H]-Chromenes.. . . . . . . . . . . . . . . . . . . . . . . . .Spirans of the Perimidine Series . . . . . . . . . . . . . . . . . . . . . . . . .Fulgides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7.6.1.7.6.2.

Arylidene Derivatives of Fulgides (ArF). . . . . . . . . . . . . . .Fulgides of the Indole Series . . . . . . . . . . . . . . . . . . . . . .

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .References.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contents xxi

8. New Trends in Raman Studies of Organic Photochromes

Jean Aubard

8.1.8.2.

8.3.

8.4.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Survey of Vibrational Studies on Spiropyran and SpirooxazinePhotochromes.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Dynamics and Structure of Transient Species Involved in thePhotochromic Process of Spiro Compounds as Probed byTime-Resolved Raman Techniques.. . . . . . . . . . . . . . . . . . . . . .

357

359

366367

369

372

378

378378

380

382

382

386389

393

394394397

397

8.3.1.8.3.2.

8.3.3.

Instrumentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Survey of Recent Time-Resolved Raman Studies ofSpiro Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Time-Resolved Resonance Raman Spectroscopy ofIndolinospironaphthoxazines: Experimental Evidence for aTTC Resonant transoid Open Form in Different Solvents. . .

Surface-Enhanced Raman Spectroscopy of Spiro Compounds: ARoute for Direct Detection and Identification of TheirPhotodegradation Products . . . . . . . . . . . . . . . . . . . . . . . . . . . .8.4.1.

8.4.2.

SERS Detection of Spirooxazines and Spiropyrans at TraceLevels in Silver Colloidal Solutions . . . . . . . . . . . . . . . . .8.4.1.1.8.4.1.2.

Brief Description of the SERS Effect . . . . . . . . . .Analysis of SERS Spectra of Some SpiroCompounds.. . . . . . . . . . . . . . . . . . . . . . . . . . .

Detection by SERS of Degradation Products fromUV-Irradiated Solutions of 8-Methoxy-6-Nitro-BIPS . . . . . .8.4.2.1.

8.4.2.2.

Assignments of SERS Spectra of 8-Methoxy-6-Nitro-BIPS . . . . . . . . . . . . . . . . . . . . . . . . . . . .SERS Analysis of UV-Irradiated Solutions ofPhotochromes . . . . . . . . . . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9. Biological Applications—Supramolecular Chemistry

Masahiko Inouye

9.1.9.2.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Photocontrol of Peptide and Protein Characteristics bySpiropyrans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9.2.1.9.2.2.

Photomodulation of Polypeptide Conformation. . . . . . . . . .Photoregulation of Protein Characteristics . . . . . . . . . . . . .9.2.2.1. Photoregulated Binding of Spiropyran-Modified

Receptor Proteins. . . . . . . . . . . . . . . . . . . . . . . .

xxii Contents

9.2.2.2.

9.2.2.3.

Photoregulation of Enzyme Activity by Use ofSpiropyrans . . . . . . . . . . . . . . . . . . . . . . . . . . . .Photocontrol of Antigen–Antibody Reactions.. . . . .

398401402402

402406

408410412

415416416416421421422422

425431436436

445451457459460

467

9.3. Spiropyran Derivatives Possessing a Molecular Recognition Site . . . .9.3.1.

9.3.2.

9.3.3.

Spiropyran Derivatives as Artificial Signaling Receptors . . . .9.3.1.1.

9.3.1.2.

Crowned Spiropyrans as Alkali (Alkaline-Earth)Metal Cation Receptors . . . . . . . . . . . . . . . . . . . .Spiropyridopyrans as Nucleobase Receptors. . . . . . .

Photoregulation of Polymer Characteristics by CrownedSpiropyrans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Other Applications Utilizing Spiropyran Derivatives. . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10. Thermochromism of Organic Compounds

André Samat and Vladimir Lokshin

10.1.10.2.

10.3.

10.4.10.5.10.6.

Introduction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Spiroheterocyclic and Related Compounds. . . . . . . . . . . . . . . . .10.2.1.

10.2.2.

10.2.3.

Compound Families. . . . . . . . . . . . . . . . . . . . . . . . . . .10.2.1.1.10.2.1.2.10.2.1.3.

Spiropyrans and Spirooxazines. . . . . . . . . . . . .[2H]-pyrans.. . . . . . . . . . . . . . . . . . . . . . . . .Other Spiroheterocyclic Compounds . . . . . . . . .

Mechanism of Thermal Isomerization . . . . . . . . . . . . . . .10.2.2.1.10.2.2.2.

Theoretical Studies. . . . . . . . . . . . . . . . . . . . .Activation Parameters of the IsomerizationReactions . . . . . . . . . . . . . . . . . . . . . . . . . . .

Evaluation of Equilibrium Constants. . . . . . . . . . . . . . . .Schiff Bases and Related Nitrogen-Containing Compounds . . . . . .10.3.1.10.3.2.

Thermochromism of Salicyl-Schiff Bases.. . . . . . . . . . . .Structural, Spectroscopic, and Theoretical Studies ofIntramolecular Hydrogen Bonding . . . . . . . . . . . . . . . . .

Biathrones and Other Overcrowded Ethenes . . . . . . . . . . . . . . . .Miscellaneous Compounds.. . . . . . . . . . . . . . . . . . . . . . . . . . .Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .