Primary photoprocesses for Fe(III) complexes with citric and glycolic acids in aqueous solutions

• The high quantum yield of photolysis of the studied complexes should be noted. • The predominant formation of corresponding long-lived radical complexes was observed. • All radical complexes (RC) exhibit a low-intensity absorption band in the visible region. • The decomposition of RC leads to the appearance of corresponding organic radicals. The mechanism of UV photolysis of Fe(III) complexes with citric ([FeCit] and [Fe(OH)Cit] - ) and glycolic ([FeGlyc] + ) acids was revealed. The excitation of the complexes leads to the predominant formation of corresponding long-lived radical complexes exhibiting a low-intensity absorption band in the visible region (λ max = 600, 550 and 660 nm for ([FeCit], [Fe(OH)Cit] - and [FeGlyc] + complexes, accordingly). The primary quantum yields of photolysis at 355 nm are 0.17, 0.28 and 0.12 for these complexes, accordingly. The decomposition of radical complexes leads to the appearance of corresponding organic radicals in solution, which are further oxidized in competitive processes by the initial complexes and dissolved oxygen. This enhances quantum yields of generation of ferrous ions in steady-state conditions and can also lead to a good yield of hydroxyl radicals in subsequent Fenton-like reactions in the presence of dissolved oxygen. The further study of the efficiency of • OH radical generation upon excitation of these systems are urgently needed in order to estimate their role in environmental aqueous chemistry and to assess their potential use in advanced oxidation processes.