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Only a small part of the numerous photochemical reactions in organic compounds result in reversible structural changes. The latter are accom panied by a change in physical properties, in particular, of electronic spectra. It is tempting to try to use this photochromic effect in various systems for controlling and regulating light fluxes and for data recording. Eventually an independent trend emerged in photochemistry - the study of the photochromism of organic compounds to establish relationships between structure and photochemical behavior, the theoretical analysis of these relationships to predict structures with pre-set photochromic parameters, and, finally, the identification of suitable areas for the application of photochromism. This monograph summarizes the results of recent studies carried out by a number of research institutions in the USSR and the GDR. Devoted to an important aspect of applied photochemistry, this monograph contains a detailed exposition of the chemical photochromes referred to briefly in the earlier editions of "Introduction to the Photochemistry of Organic Compounds" (Khimiya Press, Moscow, 1976) and "Photochemical Proces ses in Layers" (Khimiya Press, Moscow, 1978).
List of contents
1 Theoretical Studies of the Photochromism of Organic Compounds.- The Use of Qualitative Models and the Woodward-Hoffmann Rules for Describing Photochromic Systems.- Quantum-Chemical Calculations of the Spectra of Photochromic System Components and Statistical and Dynamic Indices for Estimating Their Reactivity.- Photochromic Spiropyrans.- Discussion of the Mechanisms of Photochromism using Current Ideas on Potential Energy Surfaces.- The Influence of Solvent on Photochromism.- References.- 2 Photochromic Thioindigoid Dyes.- The Structure and Spectra of Thioindigoids.- Production, Thermal Stability, and Spectra of Z-Isomers of the Thioindigoids.- On the Mechanism of the Photoisomerization of Indigoid Dyes.- The Effect of the Heteroatom of an Indigoid Dye on ?E?R. The Reasons for the Absence of Photochromism in Indigo.- The Influence of Substituents and Environmental Parameters on ?E?R.- Addendum.- References.- 3 Photochromic Compounds with N=N and C=N Chromophores.- The Principal Paths of Photochemical and Thermal E/Z-Isomerization.- Photochromic Azo Compounds.- Photochromic Aryldiazo Compounds.- The Photochromism of Compounds Containing the C=N Chromophore.- References.- 4 Photochromic Tautomeric Systems.- Photochromism of (Nitroaryl) (hetaryl) alkanes.- Photochromic peri-Aryloxy-p-quinones.- Reversible Photoacylotropic Regroupings.- References.- 5 Organic Photochromes for Solar Energy Storage.- The Principle of Accumulating Light Energy as the Energy of Strained Metastable Structures.- Efficiency Criteria.- Various Photochromic Systems for Solar Energy Accumulation and Their Mechanisms.- A Basic Scheme of the Engineering Solution to the Problem of Solar Energy Storage and Release in the Form of Thermal Energy.- Acylotropic Azomethine Systems - A New Type ofSolar Energy Storage Battery.- References.- 6 Luminescence of Photochromic Compounds.- Polyacenes and Their Analogs.- Diarylethylenes.- Thioindigoids.- Arylmethane Derivatives.- Spiropyrans.- Azomethineimines.- Compounds with an Intramolecular Hydrogen Bond.- Conclusion.- References.
