Photoredox reactions of iodo iron(III) complexes containing tetradentate ligands

Photoredox reactions occurring in irradiated methanolic solutions of trans- [Fe-III(R, R'-salen- (CH3OH)I], where R,R'-salenz- are N, N'-ethylenebis(R, R'-salicylideneiminato), tetradentate open-chain N2O2-Schiff bases with R, R' = H, 5-Cl, 5-Br, 3,5-di-Br, 3,5-di-(CH3), 3-OCH3, 5-OCH3, have been inve stigated and their mechanism proposed. The complexes are redox-stable in th e dark. Ultraviolet and/or visible irradiation of methanolic solution of th e complexes induces photoreduction of Fe(III) to Fe(II). Depending on the c omposition of the irradiated solutions, (CH2OH)-C-. radicals or solvated el ectrons were identified by the EPR spin trapping technique. The final produ ct of the photooxidation coupled with the photoreduction of Fe(III) is form aldehyde and the molar ratio of Fe(II) and CH2O is close to 2: 1. The effic iency of the photoredox process is strongly wavelength-dependent and influe nced by the peripheral groups R,R' of the tetradentate ligands.