A Non-Heme Iron Photocatalyst for Light-Driven Aerobic Oxidation of Methanol

Non-heme (L)FeIIIand (L)FeIII-O-FeIII(L) complexes (L=1,1-di(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)ethan-1-amine) underwent reduction under irradiation to the FeIIstate with concomitant oxidation of methanol to methanal, without the need for a secondary photosensitizer. Spectroscopic and DFT studies support a mechanism in which irradiation results in charge-transfer excitation of a FeIII-μ-O-FeIIIcomplex to generate [(L)FeIV=O]2+(observed transiently during irradiation in acetonitrile), and an equivalent of (L)FeII. Under aerobic conditions, irradiation accelerates reoxidation from the FeIIto the FeIIIstate with O2, thus closing the cycle of methanol oxidation to methanal.