1. Biologically Relevant Heterodinuclear Iron-Manganese Complexes.
- Author
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Carboni, Michaël, Clémancey, Martin, Molton, Florian, Pécaut, Jacques, Lebrun, Colette, Dubois, Lionel, Blondin, Geneviève, and Latour, J.-M
- Subjects
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IRON-manganese alloys , *METAL complexes , *IRON ions , *SYMMETRY (Physics) , *COMPLEX compounds synthesis , *NUCLEAR magnetic resonance spectroscopy , *MAGNETIC susceptibility - Abstract
The heterodinuclear complexes [FeIII,MnII,(L-Bn)(μ-OAc)2](ClO4)2 (1) and [FeIIMnII(L-Bn)(μ<-OAc)2](ClO4) (2) with the unsymmetrical dinucleating ligand HL-Bn {[2-bis[(2-pyridylmethyl)aminomethyl]]-6-[benzyl-2-(pyridylmethyl)-aminomethyl]-4-methylphenol} were synthesized and character-ized as biologically relevant models of the new Fe/Mn class of nonheme enzymes. Crystallographic studies have been completed on compound 1 and reveal an FeIIIMnIIμ-phenoxobis(μ-carbox- ylato) core. A single location of the FeIII ion in 1 and of the FeII ion in 2 was demonstrated by Mossbauer and ¹H NMR spectroscopies, respectively. An investigation of the temperature dependence of the magnetic susceptibility of 1 revealed a moderate antiferromagnetic interaction (J = 20 cm-1) between the high-spin FeIII and MnII ions in 1, which was confirmed by Mossbauer and electron paramagnetic resonance (EPR) studies. The electrochemical properties of complex 1 are described. A quasireversible electron transfer at --40 mV versus Ag/AgCl corresponding to the FeIIIMnII/FeIIMnII couple appears in the cyclic voltammogram. Thorough investigations of the Mossbauer and EPR signatures of complex 2 were performed. The analysis allowed evidencing of a weak antiferromagnetic interaction (J = 5.72 cm-1) within the FeuMn" pair consistent with that deduced from magnetic susceptibility measurements (j = 6.8 cm-1). Owing to the similar value of the Fe11 zero-field splitting (DFe = 3.55 cm-1), the usual treatment within the strong exchange limit was precluded and a full analysis of the electronic structure of the ground state of complex 2 was developed. This situation is reminiscent of that found in many diiron and iron--manganese enzyme active sites. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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