Electro- and Photoinduced Formation and Transformation of Oxido-Bridged Multinuclear Mn Complexes

The extensive chemistry of oxido-bridged multinuclear manganese complexes arises to a large extent from their relevance to redox-active metalloenzymes such as manganese catalases and the oxygen-evolving complex of photosystem II containing, as active centres, oxido- and carboxylato-bridged dinuclear and tetranuclear Mn complexes, respectively. During the enzymatic catalytic cycles the oxidation state changes of the Mn ions induce some structural changes of these active centres such as the formation of oxido bridges. In this area, this review is focused on examples from the literature of the formation and transformation of oxido-bridged multinuclear manganese complexes that are induced by electrochemical or photochemical means. Representative examples of such transformations are provided by polypyridyl Mn complexes, with interconversion between mononuclear, dinuclear and tetranuclear cores accompanied by the concomitant formation or breaking of p-oxido bridges. Other important examples are furnished by dinuclear Mn complexes having multipodal amino-pyridyl ligands, some of which contain phenolic units, for which a clean interconversion between mu-oxido and p-acetato bridges are observed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)