Manganese complexes clusters

Manganese represents the epitome of that characteristic property of the transition element namely the variable oxidation state. The aqueous solution chemistry includes all oxidation states from Mn(II) to Mn(VII), although these are of varying stability. Recently attention has been focused on polynuclear manganese complexes as models for the cluster of four manganese atoms which in conjunction with the donor side of Photosystem(II) is believed involved in plant photosynthetic oxidation of water. The Mn4 aggregate cycles between 6 distinct oxidation levels involving Mn(II) to Mn(IV). 

Much of the impetus for the investigation of polynuclear manganese complexes has come from a desire to produce structural and/or functional models of the manganese cluster of the OEC. Many of the results of these studies have been described in Section 5.1.2 and in reviews. ... 

S Padhye, T Kambara, DN Hendrickson and Govindjee (1986) Manganese-histidine clusters as the functional center of the water oxidation complex in photosynthesis. Photosynthesis Res 9 103-112RD... 

The M 114.02 clusters were more active than the Mn30 clusters and the Mn clusters also catalyzed t-butyl hydroperoxide decomposition ( 1%) to acetone and methanol, which prevented reliable analysis of methane activation results. We could not compare the dinuclear manganese complexes to their tri and tetra analogues because of relative solubility differences however, we were able to do this with several iron di and tetra clusters and found that the Fe402 clusters were more active with the hydrocarbons studied. Therefore, higher nuclearity or a variety of ligands may provide the shape selectivity we seek fa ultimate methane activation with Mn and Fe clusters. 

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