Conversion of (µ-OH)2Mn2(II,II) complex to (µ-O)2Mn2(III,III) core supported by a quinoxaline-based tetranitrogen ligand

Abstract

Quinoxaline-based tetranitrogen ligand, N,N’-bis(2-quinoxalylmethyl)-N,N’-dimethylethylenediamine (L9), stabilizes the bis(µ-hydroxo) dinuclear manganese(II,II) core. Oxidation of the complex with hydrogen peroxide in methanol suspension affords the bis(µ-oxo) dinuclear manganese(III,III) complex. The quinoxaline-based tripod ligand, tris(2-quinoxalylmethyl)amine (L11), did not afford corresponding bis(hydroxo) dimanganese(II,II) complex due to the subsequent atmospheric oxygen-promoted oxidation in the reaction solution similar to its quinoline counterpart, tris(2-quinolylmethyl)amine (L10). The solid state structures of [Mn(II)Cl2(L9)], [(µ-OH)2Mn2(II,II)(L9)2]2+, [(µ-O)2Mn2(III,III)(L9)2]2+, [(µ-O)2Mn2(III,III)(L11)2]2+, and [(µ-O)2Mn2(III,III)(L10)2]2+ complexes were determined by X-ray crystallography. The magnetic susceptibility measurement of (µ-OH)2Mn2(II,II) complex and electrochemical oxidation of (µ-O)2Mn2(III,III) complexes were performed to evaluate the tetramine ligand effect stabilizing the low oxidation states of dinuclear metal center supported by two oxygen atom bridges.