Redox-State Dependent Ligand Exchange in Manganese-Based Oxidation Catalysis

Abstract

Manganese-based oxidation catalysis plays a central role both in nature, in the oxidation of water in photosystem II (PSII) and the control of reactive oxygen species, as well as in chemical processes, in the oxidation of organic substrates and bleaching applications. The focus of this review is on efforts made to explore and elucidate the redox-dependent coordination chemistry of these manganese-based systems in solution and the mechanisms by which their catalytic redox reactions proceed. We also examine the behaviour and activity of complexes that have been developed and used as models for the active sites of the corresponding enzymes, or used as catalysts in the oxidation of organic substrates. Given the current concern over the environmental and economic impact of chemical processes, manganese catalysts that use H2O2 as oxidant are the primary focus of this review. The role played by Mn-based complexes in controlling reactive oxygen species and in the water oxidation complex of photosystem II has inspired the design of catalysts for chemical processes such as the oxidation of organic substrates and bleaching applications. Here, the redox and pH dependence of the coordination chemistry of Mn complexes applied in oxidations with H2O2 is reviewed.