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The electronic structure and magnetic property of metal-oxo, porphyrin manganese-oxo, and μ-oxo-bridged manganese porphyrin dimer

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Abstract

Hybrid density functional theory (HDFT) and post Hartree–Fock CCSD(T) methods are applied to elucidate the binding energies and the optimized M[BOND]O distances of transition metal oxides: MO (M = Cr, Mn, Fe, Co, Ni, Cu). The HDFT method can reproduce the CCSD(T) results, in agreement with the experimental ones. The nature of the manganese–oxygen bonds in the Mn(VI)[BOND]O, Mn(IV)[BOND]O porphyrin (PP), and Mn(V)[BOND]O PP systems are examined in relation to possible mechanisms of oxygen evolution from H2O2 and H2O in native and non-native manganese complexes. It is found that the radical character of the high-valent (PP)Mn(V)[BOND]O bond is remarkable, showing the strong potential to generate molecular oxygen because of its high reactivity. The electronic structure and magnetic property of μ-oxo-bridged manganese porphyrin dimer (PPMn(III)OMn(III)PP) are investigated for further discussion of structure and reactivity of PPMn(X)O (X = II–IV). The potential curve for release of molecular oxygen from PPMn(II)O2 is also examined to show weak affinity of O2 in the Mn complex where the oxidation number (X) of Mn is low. Implications of the computational results are also discussed in relation to oxygen evolution reactions. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004

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