Structural Proposals for the Manganese Centers of the Oxygen Evolving Complex: an Inorganic Chemist's Perspective*

This contribution provides an analysis of the basic coordination tendencies of manganese with specific emphasis on the biological chemistry of this element. The review is broken into four parts. First, a discussion of the basic coordination chemistry o f manganese is mononuclear and multinuclear environments is prescnted. Second, the biophysical data essential to the development of models for the active center of the photosystem is examined. Third, recently reported mononuclear and cluster manganese compounds are profiled with an emphasis on relating the physical parameters of the models to the structure and function of the enzymatic system. Finally, a comparison is made between the OEC and other known manganoenzymes which metabolize the 0; moiety.