Modeling the oxygen activation on dinuclear iron mmo mimics, a quantum mechanic study

Methane Mono-Oxygenase (MMO) is a di-iron active site containing enzyme that catalyzes the dissociative binding of molecular oxygen. To mimic the MMO active site we chose to study the heptapodate coordinated binuclear iron (II or III)-complexes of N,N,N′,N′-tetrakis(2-benzimidazolylmethyl)-2-hydroxy-1,3-diamino- propane (HPTB), N,N,N′,N′,-Tetrakis(2-pyridylmethyl)-2-hydroxy-1,3-diamino-propane (HPTP) in experiments and their finite cluster model N,N,N′,N′,-Tetrakis(2-iminomethyl)-2-hydroxy-1,3-diamino-propane (HPTM) in theoretical calculations. These have active sites of the form [Fe₂(HPTL)(μ-OH)]⁴⁺ or ²⁺. Quantum Mechanic structures are compared with experimental EXAFS data. For the O₂ binding on the reduced active site the μ-η¹:η¹-O₂ mode seems to proceed formation of the O=Fe-O-Fe=O bis-ferryl active site that reacts exothermally with methane. The nature of the ferryl groups are these of a reactive two center three electron bond.