Photolysis of FeOH²⁺ and FeCl²⁺ in Aqueous Solution. Photodissociation Kinetics and Quantum Yields

Photodissociation of FeOH 2+ and FeCl 2+ complexes has been studied by pulsed laser spectroscopy (λ = 347 nm) techniques. Transient bleaching of FeOH 2+ was observed due to the dissociation FeOH + → Fe 2+ + OH • (at λ = 347 nm). The observed bleaching involved the photoreduction of the species FeOH 2+ to iron(II) complexes. These latter species showed a much lower absorption. Concomitant formation of the Cl 2 • - anion radical was observed due to the reactions FeCl 2+ → Fe 2+ + Cl • (at λ = 347 nm) and Cl • + Cl - → Cl 2 • - . The experimental findings allowed us to suggest a reaction sequence involving Cl •, Cl 2 • -, ClOH • - and OH • radicals. The quantum yields found by laser kinetic spectroscopy for FeOH 2+ and FeCl 2+ photodissociation were 0.21 ± 0.04 and 0.5 ± 0.1, respectively.