Photophysical triplet state processes of 4-H-1-benzopyrane-4-thione in a perfluoroalkane. Part 2.—Delayed S2→ S0 fluorescence due to triplet–triplet annihilation

Abstract

With 4-H-1-benzopyrane-4-thione (BPT) in perfluoro-1,3-dimethylcyclohexane a delayed monomer fluorescence S₂→ S₀ due to triplet–triplet annihilation (TTA) is observable. The probability of generating an S₂ state by the annihilation of two triplet states is ca. 0.03. The generation of S₂ by TTA can be interpreted as a special case of Förster energy transfer. There is no indication of a delayed fluorescence from an upper excimer state.