Lewis acidic redox-inactive metal ions affect many chemical transformations of metal oxo compounds, including electron transfer, hydrogen atom transfer, and oxygen atom transfer processes. Redox-inactive metals also play essential roles in both heterogeneous and biological metal oxide catalysts such as the oxygen-evolving complex (OEC) of photosystem II, which contains a CaMn4Ox cluster.  A series of structurally related high oxidation state heterometallic trimanganese dioxido clusters and a related series of trimanganese tetraoxido cubane clusters containing redox-inactive metals of various charge were prepared and structurally characterized. Electrochemical studies demonstrated that the reduction potentials of the clusters are linearly correlated to the Lewis acidity of the incorporated redox-inactive metal. Reactivity studies show that varying the redox-inactive metals in isostructural compounds also affects the rates of oxygen atom transfer from the clusters as well as hydrogen atom transfer to the clusters. These studies suggest that the Ca2+ ion plays a role in modulating the reduction potential and oxygen atom transfer activity of the OEC during catalysis.

Effects of redox-inactive metals on heterometallic manganese-oxido complexes

248th National Meeting (2014)

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