Influence of protonation on the reactions of triplet-state sulfonated chloro-aluminium(III) phthalocyanine with dioxygen

Abstract

The kinetics of the reactions of sulfonated chloro-aluminium(III) phthalocyanine (AISPC) in the excited state have been studied by laser flash photolysis. Two different protonated forms of this substance were identified in the triplet state ³ππ*, AISPC and AISPCH⁺, differing in their lifetimes, τ≈ 290 and 90 µs, respectively, and rate of quenching by dioxygen [k_o2^f=(1.6 ± 0.2)× 10⁹ dm³ mol^–1 s^–1, k_o2^s=(6.6 ± 0.7)× 10⁷ dm³ mol^–1 s^–1, respectively]. It follows from the reaction kinetics that the establishment of equilibrium between the two forms AISPC and AISPCH⁺ in the ³ππ* state is insufficiently mobile compared with the rate of quenching by dioxygen.