Organic Photochromic and Thermochromic Compounds

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1 Organic Photochromic and Thermochromic Compounds Volume 2: Physicochemical Studies, Biological Applications, and Thermochromism Edited by John C. Crano Late of PPG Industries, Inc. Monroeville, Pennsylvania and Robert J. Guglielmetti University of Aix-Marseille II Marseille, France Kluwer Academic / Plenum Publishers New York, Boston, Dordrecht, London, Moscow

2 Introduction 1. Aim and Organization of the Book 1 2. Brief Historical Survey of Photochromism 2 3. Definitions of Photochromism 2 4. Brief Overview of the Chapters in the Book 4 5. Conclusion and Future Developments 7 References 8 1. Photochromic Polymers Kunihuro Ichimura 1.1. Introduction Photochromism in Polymer Matrices Synthesis Matrix Effect on Photochromism Spiropyrans and Related Compounds Azobenzenes Viologens Fulgides Photochromism in Sol-Gel Inorganic Matrices Polarization Photochromism in Polymer Solids Background Polymers Doped with Photochromic Compounds Polymers with Covalently Bound Photochromic Units Photochromic Liquid-Crystalline Polymers Photochromism in Polymeric Mesophases Nematic and Smectic Phases Cholesteric Phases Polarization Photochromism of Liquid-Crystalline Polymers 35 xv

3 xvi 1.4. Surface Photochromism for Regulation of Liquid-Crystal Alignment Surface-Assisted Liquid-Crystal Alignment Control Out-of-Plane Alignment Photocontrol Spin-Coated Films Polymeric Langmuir-Blodgett Films In-Plane Alignment Photocontrol Concluding Remarks 50 Appendix. Preparation of Photochromic Polymers 52 A.l. Polymethacrylates Substituted with Spiroindolinebenzothiopyrans (5) 52 A.2. Polymethacrylates with Spirofluorenylindolizines 53 A.3. Poly[4'-[[2-acryloyloxyethyl]ethylamino]-4-nitroazobenzene] (12) 53 A.4. An Ionene Polymer Incorporating Viologen Units (17) 53 References Photodegradation of Organic Photochromes V. Malatesta 2.1. Introduction Properties and Reaction Mechanism(s) of Spiropyrans and Spirooxazines Multiplicity of the Photoreactive State The cis-cisoid X Isomer Nitro-Substituted Spiropyrans, SP N Unsubstituted Spiropyrans and Spirooxazines Colorability and Photostability (Photocoloration Quantum Yields) Photo- and Thermal Degradation of Photochromes Degradation of Spiropyrans: General Approach Photodegradation: Dependence on the Nature and Position 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 Monosubstituted Compounds Disubstituted Compounds C3-Substituted Spiropyrans Substituents on N and C3' Photodegradation of Benzothiazolinospiropyrans Saturated Five-Membered Ring Azaheterocyclic Spiropyrans Pyrrolidine Series (X=C(CH 3 ) 2 ) 97

4 XVÜ Thiazolidine Series (X=S) Oxazolidine Series (X=0) Saturated Six-Membered Ring Azaheterocyclic Spiropyrans Spiropyran Degradation: A Quantitative Approach Non-Azaheterocyclic Spiropyrans and 8-Substituted Spirobenzodithiolane and Spirobenzoxathiolane Benzopyran Series Ill Spiro[bibenzopyrans] Dithiole Series Photodegradation of Spirooxazines 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 Irradiation Source Analysis Setup Signal-Conditioning Circuits (SCC) Operating Modes Photostability of Fulgides Commercial Spirooxazines and Chromenes: Relevant Properties and Behavior 153 References Photokinetics under Continuous Irradiation M. H. Deniel, D. Lavabre, and J. C. Micheau 3.1. Introduction Dynamic Analysis of the Isolated Photochemical Step: А-»-В(1ф) Establishment of the Photochemical Rate Equation Photochemical Reactor Uniformly Stirred and Equipped with a System for UV/Visible Spectroscopic Analysis Experimental Verification of the Validity of the Photochemical Kinetic Equations under Continuous Irradiation AB Systems Involving Two Species Establishment of the General Kinetic Equation under Continuous Irradiation 175

5 XV Properties of the Photostationary State of the AB, 2ф, Ik System AB, 1ф, Ik Systems AB, 2ф, Systems Photostationary Methods Dynamical Method ABC Photochromic Systems Involving Three Species General Comments Examples Systems with Two Photoisomers Photodegradation of a Spiro[indoline-benzopyran] ABC Systems Exhibiting Nonlinear Behavior Ideal ABC System Giving Rise to Bistability Photochromism and Photodegradation of TPID Conclusion 194 Appendix 1. Flash Photolysis versus Continuous Irradiation: Influence on the Accumulation of Reaction Intermediates 195 Appendix 2. Photostationary Methods 195 A2.1. AB, 2ф, 1А: Systems 195 A2.2. AB, 1ф, ljt Systems 197 A2.3. AB, 2ф Systems 198 Appendix 3. Thermal Relaxation of an ABC System 199 Appendix 4. Localization of an Elementary Relaxation Process in ABC Systems 202 Appendix 5. Localization of a Photodegradation Process 203 References EPR and Radical Processes Angela Alberti 4.1. Introduction Viologens Radical Cations from the Reduction of Viologens Some Particular Viologens EPR of Viologens in Micellar Systems ß-Tetrachloro-oc-Ketonaphthalene Spiroindolinic Photochromes Paramagnetic Species in Photochromism and Photodegradation Radical Ions from Spiro Compounds Spin Probes and Spin Traps with a Spiroindolinic Structure References 236

6 xix 5. Molecular Modeling Calculations Shinichiro Nakamura 5.1. Introduction Absorption Wavelength and Intensity Thermal Stability Photon-Heat Mode Photon-Photon Mode Reaction Mechanism Spiropyran Derivatives Fulgide Derivatives Other Photochromic Systems Quantum Yield 255 References The Enantiomers of 2-Donor-Substituted Benzopyrans and Benzo-l,4-oxazines and Their Thermal Racemization Albrecht Mannschreck, Klaus Lorenz, and Michael Schinabeck 6.1. Introduction Methods of Investigation Remarks Pertaining to All Methods Preparative Enrichment of Enantiomers by Enantioselective Liquid Chromatography Determination of Enantiomeric Purities Assignment of Relative Configurations Measurement of Barriers by Thermal Racemization Results of the Thermal Racemizations Transition State of C(sp3)-0 Bond Cleavage Remarks Pertaining to All Types of Benzopyrans and Benzo-l,4-Oxazines Aryl-2-methylbenzopyrans Alkoxybenzopyrans Spirobibenzopyrans Spirofoxaindane-benzopyrans] Spirofindoline-benzoxazines] Spiro[indoline-benzopyrans] Conclusion 290 References 292

7 XX 7. Structural Studies by X-Ray Diffraction Serguei Aldoshin 7.1. Introduction Spiropyrans Indolinospiropyrans Structural Features of SP Molecules The Nature of Structural Changes in SP Molecules upon Photoexcitation Effect of the Nature and Position of Substiruents in SP Molecules on the Length of the C spiro -0 Bond The Structure of Permanent Merocyanines Models of the Open Forms of Indolinospiropyrans Molecular Structure of Merocyanines Geometric Isomers of Merocyanine Forms Nature of the Molecular Packing and Energy of Intermolecular Interactions in Merocyanine Crystals Effect of the Nature of Heteroatoms in the Spiro Center on the Structure and Photochemical Properties of Spiropyrans Structural Features of Indoline Spirothiopyrans Containing S and N Heteroatoms in the Spiro Center Structure of "Symmetrical" Spiropyrans Consisting of Two Benzopyran Fragments Structure of the First Representative of Spiro-2tf- Naphtho[l,8-6c]oxepins (SPNO) Oxaindan Spiropyrans with Polycondensed Chromene Fragments Structure of 2-Oxaindan Spiropyrans Thermal Valence Isomerization of SPs Photochromism of 2-Oxaindan Spiropyrans Spirooxazines Photochromic [2#]-Chromenes Spirans of the Perimidine Series Fulgides Arylidene Derivatives of Fulgides (ArF) Fulgides of the Indole Series Conclusion 350 References 350

8 xxi 8. New Trends in Raman Studies of Organic Photochromes Jean Aubard 8.1. Introduction Survey of Vibrational Studies on Spiropyran and Spirooxazine Photochromes Dynamics and Structure of Transient Species Involved in the Photochromic Process of Spiro Compounds as Probed by Time-Resolved Raman Techniques Instrumentation Survey of Recent Time-Resolved Raman Studies of Spiro Compounds Time-Resolved Resonance Raman Spectroscopy of Indolinospironaphthoxazines: Experimental Evidence for a TTC Resonant transoid Open Form in Different Solvents Surface-Enhanced Raman Spectroscopy of Spiro Compounds: A Route for Direct Detection and Identification of Their Photodegradation Products SERS Detection of Spirooxazines and Spiropyrans at Trace Levels in Silver Colloidal Solutions Brief Description of the SERS Effect Analysis of SERS Spectra of Some Spiro Compounds Detection by SERS of Degradation Products from UV-Irradiated Solutions of 8-Methoxy-6-Nitro-BIPS Assignments of SERS Spectra of 8-Methoxy-6- Nitro-BIPS SERS Analysis of UV-Irradiated Solutions of Photochromes 386 References Biological Applications Supramolecular Chemistry Masahiko Inouye 9.1. Introduction Photocontrol of Peptide and Protein Characteristics by Spiropyrans Photomodulation of Polypeptide Conformation Photoregulation of Protein Characteristics Photoregulated Binding of Spiropyran-Modified Receptor Proteins 397

9 XXÜ Photoregulation of Enzyme Activity by Use of Spiropyrans Photocontrol of Antigen-Antibody Reactions Spiropyran Derivatives Possessing a Molecular Recognition Site Spiropyran Derivatives as Artificial Signaling Receptors Crowned Spiropyrans as Alkali (Alkaline-Earth) Metal Cation Receptors Spiropyridopyrans as Nucleobase Receptors Photoregulation of Polymer Characteristics by Crowned Spiropyrans Other Applications Utilizing Spiropyran Derivatives 410 References Thermochromism of Organic Compounds Andre Samat and Vladimir Lokshin Introduction Spiroheterocyclic and Related Compounds Compound Families Spiropyrans and Spirooxazines [2//]-pyrans Other Spiroheterocyclic Compounds Mechanism of Thermal Isomerization Theoretical Studies Activation Parameters of the Isomerization Reactions Evaluation of Equilibrium Constants Schiff Bases and Related Nitrogen-Containing Compounds Thermochromism of Salicyl-Schiff Bases Structural, Spectroscopic, and Theoretical Studies of Intramolecular Hydrogen Bonding Biathrones and Other Overcrowded Ethenes Miscellaneous Compounds Conclusion 459 References 460 Index 467