Electronic structure of dimanganese(II,III) and dimanganese(III,IV) complexes and dimanganese catalase enzyme: a general EPR spectral simulation approach

Abstract

A general approach for simulation of APR spectra of mixed-valence dimanganese complexes and proteins is presented, based on the theory of Sage et al. (J. Am. Chem. Soc. 1989, 111, 7239-7247), which overcomes limitations inherent in the theory of strongly coupled ions. This enables explanation of «anomalous» spectral parameters and extraction of accurate g tensors and 55 Mn magnetic hyperfine tensors from which the spatial distribution of the unpaired spin density, the electronic configuration, and ligand field parameters have been obtained. This is used to analyze highly accurate simulations of the APR spectra, obtained by least-squares fits of two mixed valence oxidation states, from a series of dimanganese(II,III) and dimanganese(III,IV) complexes and from the dimanganese catalase enzyme, MnCat(II,III) and MnCat(III,IV), from Thermus thermophilus