A proposal for the mechanism of the photooxidation of kinetically labile transition metal complexes. Interpretation of photoprocesses of FeSO4, FeClO4, FeCl2 in aqueous acidic solutions.

A comprehensive mechanism is proposed for the photolysis of transition meta l complexes in equilibrium solutions. This involves the photooxidation, a p ossibility of energy transfer, and several secondary thermal reactions, e.g . forward and back reactions with photochemically formed H-. radicals. The scheme includes the individual quantum yield (IQY) of each species. The pho tooxidation of FeSO4, FeClO4, FeCl2 in aqueous acidic solutions was studied by continuous irradiation. The IQYs of Fe2+ (0.2), FeSO4 (0.3), FeHSO4+ (0 .67), FeClO4+ (0.06-0.2), FeCl+ (0.8), FeCl2 (0.3) were determined. The IQY was found to be dependent on H+ concentration, due to competition with gem inal recombination within the solvent cage. This dependence, and the effici ency of energy transfer between excited iron(III) species and iron(II) in g round state, are discussed.