Carboxylate-bridged dinuclear manganese systems - From catalases to oxidation catalysis

Dinuclear manganese based enzymes engage in processes as diverse as amino acid hydrolysis and hydrogen peroxide disproportionation. Despite the mechanistic diversity displayed by this class of enzymes, a common feature is the presence of carboxylate residues, which serve to bridge the manganese centres and of hemi-labile oxo-, hydroxyl- and aqua-bridge, which shows considerable redox state dependence on their lability. The role of carboxylate-bridged dinuclear manganese complexes in the disproportionation of hydrogen peroxide is reviewed both in enzymatic and biomimetic systems. The lability of the carboxylate bridge and bridging oxo, hydroxyl and aqua ligands during the catalase cycle is discussed in relation to the redox cycle, which the dinuclear manganese centres undergo. The relationship between catalase activity and catalytic oxidation is discussed briefly with regard to understanding the nature of catalytically active species present during oxidation catalysis.