Photolysis of Fe(III) complex with ethylenediamine-N,N'-disuccinic acid and its efficiency in generation of •OH radical.

The mechanism of photolysis of the Fe(III) complex with ethylenediamine-N,N'-disuccinic acid ([FeEDDS]-) was revealed using a combination of time resolved and stationary photochemical methods. Using laser flash photolysis (λex = 355 nm), the formation of the primary intermediate, the radical complex of Fe(II) with quantum yield (φ0 = 0.21) was detected for the first time. The lifetime (1.8 ms) and the spectral characteristics (λmax = 520 nm, ε520 nm = 160 M-1cm-1) of this intermediate were also determined. The dependence of the quantum yield of photolysis of the [FeEDDS]- complex (φFeEDDS) and the hydroxyl radical quantum yield (φOH) on the excitation wavelength, pH, and concentrations of the ligand and iron ions were obtained for the first time. It has been established that under optimal conditions at neutral pH, the value of φFeEDDS is about 0.8, and φOH is about 0.15. It was found that φFeEDDS does not depend on the initial concentrations of Fe(III), EDDS, but depends on pH, the excitation wavelength and the presence of oxygen. φOH does not depend on the initial concentrations of Fe(III), EDDS, but depends on pH and the excitation wavelength. The high φOH values make the [FeEDDS]- complex a suitable system for the generation of •OH radical at neutral pH under UV radiation.