Mechanism of triplet exiplex quenching by molecular oxygen. Singlet-triplet splitting for the charge transfer state

Abstract

Quenching rate constants of triplet exciplexes with partial or complete charge transfer formed by electron donors (methyl-, methoxy-benzenes and aromatic amines) with triplet state quinones by O 2 were measured in non-polar solvents by means of laser photolysis. The mechanism proposed to explain high values of quenching constants ( 1 3 of diffusion limit) includes transition between triplet and singlet charge transfer states (the latter should have lower energy) caused by exchange interaction with paramagnetic species. Triplet exciplexes with inverse order of triplet and singlet states and low quenching constants were also observed.