The deactivation of singlet excited all-trans-1,6-diphenylhexa-1,3,5-triene by intermolecular charge transfer processes. 1. Mechanisms of fluorescence quenching and of triplet and cation formation Original Research Article

The photophysical and fluorescence quenching properties of all-trans-1,6-diphenulhexa-1,3,5-triene (DPH) were investigated in toluene and acetonitrile solution and the influences of the external heavy-atom effect (HAE) and of charge transfer (CT) processes on the fluorescence quenching mechanism were characterized. Particular emphasis was placed upon the elucidation of the electron transfer reactions in the quenching of DPH fluorescence by p-dicyanobenzene (p-DCB) in acetonitrile. It was shown that the combination of stationary and time-resolved fluorescence measurements, laser flash photolysis and CIDNP experiments allows a comprehensive description of the primary and secondary electron transfer reactions in the fluorescence quenching process. In particular, the characterization of the kinetics of genuine charge recombination (CR) reactions of the DPHp-DCB singlet and triplet ion pairs, of the spin evolution process and of the degenerate electron transfer between neutral and cationic DPH was achieved.