Том 52, № 6 (2018)

It has been shown that dyes (eosin, erythrosine, Rose Bengal, fluorescein, Rhodamine C, Rhodamine 6G, 2,7-dichlorofluorescein, Methylene Blue, and Acridine Orange) sensitize the decomposition of 2-mercaptobenzothiazole in aqueous solutions. The quantum yields of photosensitized decomposition of 2-mercaptobenzothiazole depend linearly on the quantum yields of dye triplets. As shown by pulse photolysis, the triplet state of the dyes (eosin, erythrosine, and Rose Bengal) is quenched by 2-mercaptobenzothiazole. A mechanism has been suggested for the photosensitization of 2-mercaptobenzothiazole decomposition by irradiation of the dyes.

The effect of the composition and dielectric characteristics of binary solvent mixtures on the photoreduction rate constant (k_H) of 3,6-di-tert-butyl-o-benzoquinone and its 4-cyano derivative in the presence of three N,N-dimethylanilines has been studied. It has been found that for the pair 3,6-di-tert-butyl-o-benzoquinone–N,N-dimethylaniline, the free energy electron transfer of which is ΔG_e = +0.11 eV, ln k_H is proportional to the difference of the reciprocals of experimentally determined optical and static permittivities for the toluene–acetonitrile and benzene–N,N-dimethylformamide blends. For quinone–amine pairs, which have ΔG_e ≠ +0.11 eV, k_H is maximal in toluene and benzene and decreases with the increasing amount of the polar component in the solvent mixture, with lnk_H being inversely proportional to the permittivity of the medium.

Spectral, luminescent, and kinetic properties of 2,5-bis(4-diethylaminobenzylidene)cyclopentanone (ketocyanine, A) in air-saturated and oxygen-free acetonitrile have been studied. The ns-Laser and continuous photoexcitation of A results in a product B undergoing in the oxygen-free solution the intersystem crossing into the triplet state with the lifetime of 1 µs. The photoinduced conversion of A into B occurs within a time shorter than 1 µs and is manifested in a decrease in both the fluorescence intensity of A and absorbance at 457 nm and in the appearance of a new absorption at λ > 535 nm. The product B undergoes photoinduced conversion to the parent A via both the excited singlet and triplet states of B.

A spectral-luminescent study of the oxidizing transformations of 5-hydroxy-6-methyluracil in aqueous alkali solutions has been carried out for the first time. It has been established that 5,5,6-trihydroxy-6-methylpyrimidine-2,4-dione is formed in the reaction.

The effect of γ-irradiation of cotton cellulose on the molecular-weight distribution (MWD) of the nitro esters prepared from the irradiated cellulose has been studied. It has been established that the degradation of cellulose during the sulfuric acid–free nitration in fuming nitric acid occurs according to a random law with the most probable MWD, whereas the esters obtained in a sulfuric acid–nitric acid nitration mixture are almost uniform in terms of MWD. The rate constants of degradation by nitration increase with the absorbed dose. An increase in the uniformity of the nitro esters as a result of the washing out of the low-molecular-weight fraction improves their physicomechanical characteristics. An equation is proposed for describing the kinetics of degradation of irradiated cotton cellulose during its nitration in fuming nitric acid.

Fast exciton quenching by methyl viologen (MV²⁺), an electron acceptor, on the CdSe quantum dot surface impulsively induces acoustic vibration via the mechanism of inverse piezoelectric effect, thereby causing an increase in the amplitude of the coherent acoustic phonon in the CdSe/MV²⁺ system compared to pure CdSe.