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1. In the pulsed photoexcitation of a solution of a copolymer of indolinospiropyran with styrene, various stereoisomers of the merocyanine form are formed. 2. The proposed scheme of photoconversions of the copolymer includes a step of formation of a cis-cisoid isomer (∼490 nm), which is rapidly converted to three interconvertible stereoisomers with maximum of the absorption bands at ∼560, ∼600, and ∼640 nm. 3. The kinetics of dark bleaching at a time >0.1 sec is determined by the decrease in the optical density of the most stable isomer with λmax ≈ 600 nm.

The spectroscopic characteristics and the mechanism of the motion of solvated electrons in polar organic liquids are examined. It is shown that the part of the spectrum where solvated electrons absorb is determined by the polarity of microregions in the liquid. The intensity and half-width of the absorption band depend on the region of the spectrum in which absorption occurs. The theoretical concepts concerning the nature of the solvated electron and the mechanism of its motion are considered. The bibliography includes 65 references.

Pulse radiolysis methods (50 nsec and 2.5 μs pulse durations) with simultaneous optical and electrical registration have been used in a study of temperature influence on mobility and reactions of the solvated electrons in hexamethylphosphortriamide (HMPA). Transient optical absorption spectra in HMPA were studied. A spectrum of e − solv in pure HMPA was observed up to 2000 nm. Activation energies of e − solv mobility, salt ions mobility (NaBr) and diffusion-controlled reaction between e − solv and induced acceptor (Cu2+) in HMPA were determined (1.6; 5 and 1.8 kcal/mole respectively). The reaction mechanism and migration process of e − solv are discussed on the basis of obtained results.

CONTENTS I. Introduction 736 II. Procedure 737 III. Electrical properties 737 IV. Electron spin resonance 739 V. Influence of impurities on the electrical properties 741 VI. Conduction mechanism 742 VII. Nature of the paramagnetism 744

Pulse radiolysis methods with simultaneous optical and electrical registration have been used in a study of transient charged species in pure hexamethylphosphortriamide (HMPA) and its solutions of alkaline metal salts. A number of transient optical absorption bands were observed, including the solvated electron (es ) spectrum. The experimental technique allowed one to establish some primary reactions in the radiolysis mechanism of HMPA and to determine mobility values of charged species. In case of salt solutions an increase of G(es ) up to the value of total ionization as a result of salt concentration increase (10−3−3:10−1 M) was observed. The possibility of thermalized electron stabilization by cations of alkaline metals is discussed. The concentration dependence of G(es ) is described by an analytical formula if one assumes that es is stabilized by metal cations in the form of a complex [M + …e − 2]. The transient absorption band observed in the near IR is ascribed to this complex. The time o...

1. Acceptor impurities on the surface of anthracene and in the presurface layer lead to the formation of regions with a high concentration of holes. 2. When an electrochemical reaction, which injects holes into anthracene, proceeds at the phase boundary, the existence of regions on the surface with a high concentration of holes leads to a pitting character of the corrosion, which indicates its autocatalytic character. 3. In the case where anthracene, excited by the pulses of low-energy electrons, exhibits a nonequilibrium conductivity, the existence of regions with a high concentration of holes is manifested in the appearance of the slow component of the hole conductivity and an increase in the efficiency of generating current carriers in the surface layer.

A large number of investigations has been devoted to the mechanism of conduction in organic semiconductors.The first step in the study of the mechanism of conduction is generally the determination of n and µ appearing in the expression for conductivity σ = enµ. In inorganic semiconductors, this is done by measuring the Hall effect. Then, by studying the dependence of µ and n on the temperature and other parameters, the mechanism of conduction in the material investigated is deduced.

At the present time, hundreds of new organic semiconducting materials have been obtained [1–3]. In this chapter we shall consider those characteristics of these materials that can be used in various branches of power engineering and radioelectronics [4].

A study has been made of the spectral characteristics and photoelectric sensitivity of many organic polymers with conjugated double bonds. In spite of the considerable number of papers devoted to photoelectric sensitivity, so far there has been no sufficiently well-founded theory of the mechanism of the photoexcitation of the current carriers and their transfer in the polymeric structure. Nevertheless, the characteristics of the photoconductivity of several polymers with conjugated bonds give grounds for considering these polymers as promising materials for practical use.

The question of the possibility of applying to biopolymers the ideas developed in the physics of the solid state has a fairly long history. In 1938 Jordan [1] and in 1941 Szent-Gyorgyi [2] suggested that proteins may possess the nature of semiconductors. Subsequent biophysical investigations of biopolymers at the molecular level led to the conviction that the phenomena taking place in ordered biological structures cannot be interpreted unless in some cases the biopolymer is considered as a solid body. This is explained, in the first place, by the fact that proteins consist of very large molecules with molecular weights reckoned in millions and, in the second place, by the fact that the enormous role played by the medium (for example, a solvent) in which the various processes take place is becoming ever clearer to chemists and biologists.

At the present time, numerous polymers have been synthesized which are stable at high temperatures and possess very diverse electrical and magnetic properties. Their catalytic activity in heterogeneous catalysis has been studied for the cases of the decomposition of hydrogen peroxide [1] and formic acid [2, 3], de-hydrogenation and dehydration reactions [3, 5, 6], and the decomposition of hydrazine and nitric oxide [6, 8].

There is no doubt that the surface properties of organic semiconductors are extremely important both for understanding the processes taking place at the boundary of separation of two phases and for more complete understanding of the processes taking place in the bulk of the semiconductor. The influence of the state of the surface and the processes taking place at the surface on the bulk properties is particularly strong when the semiconductors have a low intrinsic conductivity [1]. In the adsorption of gases on the surface of a semiconductor it has been found experimentally that some molecules are capable of increasing the concentration of electrons in the surface layer and others of decreasing it. The process of adsorption may be considered in two ways: either as a creation of donor (acceptor) impurities at the surface [2, 3] or as the formation of charge-transfer complexes [4].

One of the most important problems of present-day chemistry is the creation of new substances and materials possessing a series of valuable properties. Particularly great prospects have been opened up in the synthesis and study of organic compounds possessing delocalized electrons because of the presence in them of conjugated bonds or the formation of charge-transfer complexes. Such compounds have acquired the name of organic semiconductors. Starting in 1960, the volume of investigations on the chemistry and physics of these materials has risen to such an extent that the possibility has appeared of generalizing some basic achievements in this field [1, 2]. At the present time organic semiconductors include both low-molecular-weight compounds and polymers with a large number of conjugated bonds, charge-transfer complexes in which, owing to a definite structure, conditions are created for the delocalization of an electron, stable free radicals, and also some biopolymers (including proteins) the conductivity of which can be explained by a nonionic mechanism.