Photo-induced oxidation of [FeII(N4Py)CH3CN] and related complexes

The photochemistry of the complexes [Fe(N4Py)(CH3CN)](ClO4)(2) (1), where N4Py is 1,1-di(pyridin-2-yl)-N, N-bis(pyridin-2-ylmethyl) methanamine and [Fe(MeN4Py)(CH3CN)](ClO4)(2) (2), where MeN4Py is 1,1-di(pyridin-2-yl)-N, N-bis(pyridin-2-ylmethyl)ethanamine, in water, dichloromethane and methanol is described. Under UV or visible irradiation both 1 and 2 undergo enhancement of the rate of outer sphere electron transfer to O-3(2) to yield the superoxide radical anion and the complexes in the Fe(III) redox state. Addition of ascorbic acid to the photoproduct leads to a recovery of the initial UV/Vis spectrum of 1 and 2, indicating that ligand oxidation does not occur. The results are discussed within the context of the recent report of the enhancement of the oxidative DNA cleavage activity of 1 under UV and visible irradiation (Inorg. Chem. 2010, 49, 11009).