TRIPLET-ENERGY TRANSFER TO STYRYLPYRIDINES

Radiationless energy transfer has been studied in the photosensitized cistrans isomerization of styrylpyridines. Two sensitizers, biacetyl and carbazole, have been examined and proved to transfer the excitation energy by way of triplet to the acceptor molecule, in particular the eis 3-styrylpyridine. Quenching of the room temperature phosphorescence of biacetyl has been measured at increasing acceptor concentrations. The high kq obtained and the comparison with stilbene, point out that triplet levels of styrylpyridines are lower than those of stilbenes. Experiments in rigid glasses using carbazole as a donor again proved the triplet-triplet intermolecular interaction, since, due to the additional energy dissipation process, the lifetime of triplet carbazole is shortened, giving a transfer constant kt= 0.81·mole-1 sec-1, in agreement with a short distance interaction. © 1969, Walter de Gruyter. All rights reserved.