PHOTOREDOX CHEMISTRY OF IRON(III) OXALATO COMPLEXES WITH N,N’-1,1-R2-ETHYLENEBIS(R’-SALICYLIDENEIMINATO) LIGANDS
Mário Izakovič and Jozef
Department of Inorganic Chemistry, Slovak Technical University ,
Radlinského 9, 81237 Bratislava, Slovakia ; E-mail: email@example.com
The complexes Na[Fe(R’-sal-R2-en)(C2O4)], where R’-sal-R2-en2- are tetradentate open-chain N,N'-1,1-R2-ethylenebis(R’-salicylideneiminato) N2O2-ligands (R = H or CH3; R’ = H, 5-Cl, 5-Br, 3,5-Br2, 3-OCH3 or 4-OCH3), are redox stable in methanolic solutions in the dark. Continuous irradiation of such solutions by ultraviolet and/or visible light leads to photophysical and photochemical deactivation processes yielding Fe(II), CO2 and CH2O as final products. Using EPR spin trapping technique, carbon dioxide anion radicals CO2·- were identified in methanolic solutions of the complexes irradiated at lirr > 300 nm. Tetradentate ligands behave as innocent moiety not participating in redox processes of the complexes. The efficiency of the photoredox processes, expressed by the quantum yield of Fe(II) formation, FFe(II), slightly decreases with increased wavelength of the incident radiation, and is influenced by the peripheral groups R and R’ of the tetradentate ligands. A mechanism of the primary photochemical and subsequent thermal reactions is proposed.
Key words: Iron(III) complexes, photochemistry, mechanism