New insight into photochemistry of ferrioxalate

Optical spectroscopy and nanosecond flash photolysis (Nd:YAG laser, 355 nm, pulse duration 5 ns, mean energy 5 mJ/pulse) were used to study the photochemistry of Fe-III(C2O4)(3)(3-) complex in aqueous solutions. The main photochemical process was found to be intramolecular electron transfer from the ligand to Fe(III) ion with formation of a primary radical complex [(C2O4)(2) Fe-II(C2O4 center dot)](3-). The yield of radical species (i.e.,) CO2 center dot- and C2O4 center dot- was found to be less than 6% of FeIII(C2O4)(3)(3-) disappeared after flash. [C2O4)Fe-2(II)(C2O4 center dot)](3-) dissociates reversibly into oxalate ion and a secondary radical complex, [(C2O4)Fe-II(C2O4 center dot)]. The latter reacts with the initial complex and dissociates to Fe-II(C2O4) and oxalate radical. In this framework, the absorption spectra and rate constants of the reactions of all intermediates were determined.