DEACTIVATION OF THE LOWEST TRIPLET-STATE OF 4-H-1-BENZOPYRAN-4-THIONEIN DIFFERENT SOLVENTS

Investigation of 4-H-1-benzopyran-4-thione (BPT) in its triplet state was performed in a flash photolysis system. The kinetics of phosphores cence and transient triplet-triplet absorption decay of BPT were measu red in deoxygenated solutions. The studies were made with both protic and aprotic solutions of different polarity (ethanol, benzene, acetoni trile, n-hexane, n-hexadecane and 3-methylpentane). The rate constants of intramolecular decay k0 as well as the self-quenching rate constan ts k(sq) for BPT at room temperature were determined. The results conf irmed the essential nature of the contribution from the self-quenching process in the deactivation of the BPT triplet state. The k(sq) value s suggest that this process is near diffusion controlled, as is the ca se for other thioketones.