Synthesis, structure, and magnetic properties of the stable triangular (Mn sup IV sub 3 O sub 4 ) sup 4+ core

The structure of the oxygen evolving center (OEC) in photosystem II of plants and the mechanism of water oxidation are still unknown. Recent biological results have been reviewed in ref 1. Chemists can contribute to this study by synthesizing new manganese clusters and studying the electronic properties of those complexes; then useful comparisons can be made with the spectroscopic properties of the natural system. This approach led, for instance, to the synthesis of (Mn{sub 4}O{sub 3}Cl){sup 6+} cores and of adamantane-like (Mn{sub 4}O{sub 6}){sup 4+} cores. Chemical results have been reviewed in ref 6. The authors report here the synthesis and magnetic studies of a new type of manganese cluster made of a triangular (Mn{sub 3}O{sub 4}){sup 4+} core with two mono-{mu}-oxo bridges and one di-{mu}-oxo bridge.