DECAY DYNAMICS OF THE TRIPLET-STATE OF 2,6-DIMETHYL-4H-1-BENZOTHIOPYRAN-4-THIONE IN SOLUTION

The phosphorescence decay kinetics and transient triplet-triplet absor ption of 2,6-dimethyl-4H-1-benzothiopyran-4-thione (DMBTPT) were recor ded in deoxygenated n-hexane, n-hexadecane and 3-methylpentane solutio ns. The measurements of DMBTPT in the triplet state were performed usi ng a flash photolysis system with an excimer laser as excitation sourc e. The triplet state decay constant at infinite dilution (k(o)) and th e self-quenching rate constant (k(sq)) for DMBTPT at room temperature were determined from the Stem-Volmer equation. The results obtained co nfirm an essential contribution of the self-quenching process to the d eactivation of the DMBTPT triplet state. The k(sq) values suggest that this process is diffusion controlled, similar to other thioketones. M oreover, an analysis of the temperature dependence of tau(-1) at diffe rent concentrations of DMBTPT in 3-methylpentane provides further evid ence for a viscosity-controlled deactivation process.