Theoretical investigation on the mechanism of oxygen atom transfer between two non-heme iron centres

Density functional theory calculations are presented on the oxygen atom transfer reaction between two non-heme iron centres: One contains Bn-tpen [N-benzyl-N,N′,N′-tris(2-pyridylmethyl) ethane-1,2-diamine], whereas the other contains N4Py [N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine]. The calculations show that the (Bn-tpen)Fe-O-Fe(N4Py) complex is a stable entity but considerably higher in energy than isolated species. However, a mechanism of oxygen atom transfer from one non-heme iron centre to the other will proceed via this oxido-bridged intermediate. This oxido-bridged complex has both iron atoms in oxidation state III so that in the process of the formation of the complex, an electron transfer from the FeII centre to the FeIV(O) centre has taken place. Nevertheless, both metal atoms have different orbital and spin-density occupation. A large solvent effect on the reaction barriers is obtained, indicating that the reaction proceeds only in very polar environments. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.