Kinetics of the (photo)oxidation of the thionine leuco base with uranyl nitrate

Spectrophotometry and lamp and laser flash photolysis have been used to investigate the kinetics of the formation and decay of thionine and semithionine, obtained in the photooxidation of the thionine leuco base with uranyl nitrate. It has been shown that after the light flash a certain amount of thionine is formed in the cage oxidation of semithionine with uranoyl UO₂ ⁺ (concentration ratio of thionine and semithionine leaving the cage 595). A kinetic scheme of the reaction has been proposed, which describes satisfactorily the experimental data. The equilibrium constant K=1.2±0.3)·10^–4 has been obtained for the dark oxidation of the thionine leuco base with uranyl nitrate in aqueous sulfuric acid (pH 1.0) which is close to the calculated value.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 13–18, January, 1990.     

Effect of polymer additives on magnetic modulation of the yield of products of recombination of triplet radical ion pairs in electron phototransfer between N,N-dimethylaniline and pyrene. 1. Polyacrylamide in ethylene glycol

The effect of a magnetic field on the yield of products of recombination of triplet radical ion pairs in phototransfer of an electron between N,N-dimethylaniline and pyrene in ethylene glycol was investigated by laser strobe fluorometry. It was found that addition of a flexible-chain, linear polymer, polyacrylamide (PAAm), to the solution decreases the magnetic field effect (MFE) for concentrations higher than 130–140 g/liter. A linear correlation was established between the MFE and translational mobility of the reagents. A similar correlation was obtained for MFE in a viscous homogeneous liquid. A conclusion was drawn concerning the absence of a specific effect of PAAm on the cage effect based on the agreement of these correlations.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117334 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2053–2058, September, 1992.     

Femtosecond dynamics of relaxation of photoexcited meso-tetraferrocenylporphyrin in the nonprotonated and diprotonated forms (Fc4PH2 and Fc4PH42+)

The relaxation of the Q¹(—*) excited state of the nonprotonated Fc₄PH₂ and diprotonated Fc₄PH₄ ²⁺ forms of meso-tetraferrocenylporphyrin was studied by femtosecond laser absorption spectroscopy. Transition from the Q¹(—*) state to the charge-transfer state was shown to occur within 208±10 fs for Fc₄PH₂ and 9±3 ps for Fc₄PH₄ ²⁺. A fast vibrational relaxation with a characteristic time of 120—140 fs was found for both forms. The relaxation time of Fc⁺—P^– charge-transfer state for Fc₄PH₂ was 17±4 ps.     

Luminescence of Eu3+ Ions in a Matrix of a Fluorinated Yttrium–Aluminum Composition

Physics of the Solid State - We studied the optical spectra of fluorinated yttrium–aluminum compositions activated by Eu3+ ions. The compositions were synthesized by thermal decomposition at...     

Conformational Composition of Stereoisomers of 2,4,5-Trisubstituted 1,3,2-Dioxaborinanes

¹H NMR spectroscopy and MM+ and AM1 calculations were used for configurational assessment of stereoisomers of 4-methyl-2,5-disubstituted 1,3,2-dioxaborinanes (differing in the configuration of the ring C⁴ atom). The molecules are conformationally inhomogeneous; this is due to the internal rotation of the substituent at the C⁵ atom, while in the cis isomers, in addition, by the equilibrium between the S-4e5a and S-4a5e sofa conformations, shifted to the latter form.