A Synthetic Model of the Mn_3Ca Subsite of the Oxygen-Evolving Complex in Photosystem II

摘要

Within photosynthetic organisms, the oxygen-evolving complex (OEC) of photosystem II generates dioxygen from water using a catalytic Mn_4Ca0_n cluster (n varies with the mechanism and nature of the intermediate). We report here the rational synthesis of a [AAn_3CaO_4]~(6+) cubane that structurally models the trimanganese-calcium-cubane subsite of the OEC. Structural and electrochemical comparison between Mn_3Ca0_4 and a related Mn_40_4 cubane alongside characterization of an intermediate calcium-manganese multinuclear complex reveals potential roles of calcium in facilitating high oxidation states at manganese and in the assembly of the biological cluster.