Comparison of photocatalytic activities of 3d transition metal ions for hydrogen peroxide photolysis and photoinitiated hydroxylation of 2-hydroxybenzoic acid

Abstract

Quantum yields of hydrogen peroxide photolysis and photoinitiated hydroxylation of 2-hydroxybenzoic acid in the presence of 3d transition metal ions have been measured. Marked photocatalytic effects were only observed for Cu(II) in hydrogen peroxide photolysis, and for Fe(III) in photoinitiated hydroxylation of 2-hydroxybenzoic acid. No photocatalytic activity was detected for the other 3d transition metal ions investigated. Fe(III) and Cu(II) differ in their photocatalytic activities, suggesting that the simple concept of free OH. radical formation cannot explain the mechanisms of their action.