- First Synthesis of a Binuclear [MnII(bipy)-FeIII(porphyrin)] Complex: Spectroscopic Characterization and First Evidence of Reversible Formation of Manganese(III) as Manganese Peroxidase
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A [(P)FeIII-MnII] bimetallic complex, mimicking the active site of manganese peroxidase, has been synthesized. A modified highly fluorinated porphyrin, 5,10,15-tris(pentafluorophenyl)-20-(o-aminophenyl)porphyrin, has been used to introduce, through a short spacer linked to the amino function, a manganese auxiliary ligand, 6-aminomethyl-2,2′-bipyridine. Two successive metalations by FeCl2 and MnCl2 afforded the [(P)FeIII-MnII] bimetallic complex that has been characterized by elemental analysis and FAB+ mass spectrometry. X-band EPR spectroscopy and magnetic susceptibility measurements were in agreement with two high spin Fe(III) and Mn(II) centers without magnetic exchange interaction. Moreover, there is no higher intermolecular association through μ-chloro bridging as observed by EPR with a simpler chloromanganese complex, Mn(bipy)2Cl2, at high concentration. Addition of pentafluoroiodosobenzene in methanol at 0 °C led to the progressive and complete disappearance of the EPR Mn(II) signals, that were recovered after addition of a phenol. This result is consistent with Mn(III) formation. This production of Mn(III) requires the presence of the iron porphyrin and is proposed to occur through the intermediate formation of a Fe(IV) dimethoxide species which can be related to the oxidation of Mn(II) catalyzed by manganese peroxidase compound II.
- Policar, Clotilde,Artaud, Isabelle,Mansuy, Daniel
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p. 210 - 216
(2008/10/09)
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