Contribution of Triplet-Triplet Annihilation to the Deactivation Kinetics of the Triplet State of Etioporphyrin in Liquid Solutions

摘要

Kinetics of the triplet state deactivation is studied for etioporphyrin in toluene by detecting the trip-let-triplet T-T absorption and delayed ￡-type fluorescence. It is found that, for low porphynn concentrations, the kinetics of the delayed fluorescence decay differs from that of the T-T absorption at both the initial and final stages of the decay. These distinctions are explained based on the mechanism of the triplet-triplet annihilation (TTA) involving the reversible formation of complexes of two molecules in the triplet state. In these cases, TTA results in a substantial decrease in the calculated rate constant of the triplet state quenching by molecules in the ground state compared to the situation when the influence of TTA on kinetics is weaker. The experimental data were analyzed by separately considering the cases when the contribution of one of the bimolecular processes of the triplet state quenching (TTA or quenching by molecules in the ground state) dominated. The calculated rate constants of the concentration quenching of the triplet state and of quenching caused by the TTA greatly exceed those calculated from kinetics influenced by both TTA and concentration quenching.