Decay dynamics of aromatic thione triplet states in fluid solution

Abstract

Phosphorescence emission and excitation spectra, quantum yields, and lifetimes of several aromatic thiones have been measured in fluid solution at room temperature. Excitation to any of the excited electronic states accessible in the near-uv and visible regions of the spectrum results in population of the lowest triplet state with near unit quantum yield. Triplets of relatively inflexible thiones decay non-radiatively with rate constants of the order of 105 s−1 whereas thiones capable of higher amplitude flexion or group rotation exhibit non-radiative decay constants ≥ 107 s−1 at infinite dilution in aprotic solvents. Self-quenching occurs at diffusion-controlled rates.