A Mossbauer and electrochemical study of mononuclear iron(III) complexes with benzimidazole-based flexible bidentate ligands

A series of Fe-III complexes of stoichiometry [FeLX3].nH(2)O have been synt hesized, where X = Cl-, HCO2- and L is a flexible bidentate ligand, 1,3(bis -benzimidazolyl) propane and 1,4(bis-benzimidazolyl)butane. Mossbauer data reveals that the isomer shift values lie in the range typically observed fo r high spill Fe-III complexes, while the slightly large quadrupole splittin g parameter indicates a rhombically distorted Fe-III centre. Cyclic voltamm etric studies reveal that the E-1/2 for the Fe-III/Fe-II couple for the for mate complex shifts more cathodically than for the chloride complex; implyi ng that HCO2- is more effective at lowering the Lewis acidity of the Fe-III centre.