TRIPLET-STATE DEACTIVATION AND PHOTOCHEMISTRY OF AROMATIC THIOKETONES IN SOLUTION - XANTHIONE

The decay of triplet xanthione has been studied by means of the phosphorescence decay kinetics and the photodecomposition quantum yields φx measured in a variety of solvents at room temperature. Both the triplet decay and φx are strongly dependent not only on the solvent but also on the xanthione concentration. Based on these results a mechanism for the photochemical transformation of xanthione is proposed which features a primary photochemical step involving hydrogen abstraction from the solvent and the formation of a solvent-caged radical pair. Following these steps there is a competition between the recombination of the caged radicals and the reaction of the thioketyl radical with a xanthione ground state molecule. The reaction scheme is supported by quantitative calculation of the yields. © 1979.