Formation and quenching of the photoexcited triplet state of tetrasulfonated zinc phthalocyanine, ZnPcS 44− by azaferrocene and ferrocene

Abstract

A nanosecond laser flash photolysis study with excitation at 532 nm showed that azaferrocene (AF) quenches the S 1 state of ZnPcS 4 4− in DMSO solutions giving its T 1 state, which is then quenched itself by the same solute with the rate constant 2.4×10 8 M −1 s −1. Ferrocene (Fc) quenches only the phthalocyanine T 1 state (and not the S 1 state) with the rate constant 4.4×10 8 M −1 s −1. 2,5-DimethylAF does not quench the S 1 state of ZnPcS 4 4−. These differences cannot be accounted for by thermodynamic considerations, but are discussed in terms of the possible oxidation of AF at the nitrogen atom.