Solute re-encounter probabilities from dissociative oxciplex relaxation

Abstract

Measurements of the quantum yield of self-sensitized 1,3-diphenylisobenzofuran peroxidation as a function of dissolved oxygen of added azulene concentrations indicate that oxygen quenching of the sensitizer singlet state produces both triplet and ground states of the sensitizer in addition to O 2( 1Δ g) and O 2( 3Σ − g). This partitioning of quenching products may be due to the competitive relaxation of the initially formed complex (oxciplex), or to sequential relaxation of different oxciplex states in which symmetry and spin barriers are negotiated by complex dissociation and re-encounter of the solute pair in the required configuration. The latter interpretation provides re-encounter probabilities for the processes M(T 1) + O 2( 1Δ g) → M(T 1) + O 2( 3Σ − g) and M(T 1) + O 2( 3Σ − g) → M(S o) + O 2( 1Δ g) from which estimated rate constants are compatible with theoretical expectation.