PHOTOINDUCED ELECTRON-TRANSFER IN ION-PAIRS OF CATION-ANION POLYMETHINE DYES

Photoinduced electron transfer in ion pairs of cation-anion polymethin e dyes was studied by flash photolysis. The formation of radicals, whi ch are the products of photoinduced transfer of an electron from an an ion to a cation in the ion pairs, was observed during photoexcitation of a number of cation-anion dyes in nonpolar and some weakly polar sol vents (in particular, in toluene and chloroform). Photoinduced electro n transfer is also observed during triplet sensitization of ion pairs of the cation-anion dyes. The redox potentials of the cations and anio ns constituting the dyes were measured; the radical yields were compar ed with the free energies of photoinduced electron transfer. Photoindu ced electron transfer in the systems under study was compared with sim ilar process in cyanineborate ion pairs.