Tetranuclear complexes as precursors for the rational design of pentanuclear oxido clusters reminiscent of the oxygen evolving complex in photosystem II

Abstract

The oxygen evolving complex in Photosystem II contains a multimetallic [Mn_4CaO_5] active site. Previously, a pseudo-C_3 sym. tris(dipyridyl alkoxide) ligand based on a 1,3,5- triarylbenzene framework was used for the synthesis of trimetallic clusters. Here, substitution of a single dipyridyl alkoxide moiety for a carboxylate moiety leads to the formation of tetrametallic complexes [M_4(μ^3-OH)] (M = Mn, Fe, Co). Starting from [Mn_4(μ^3-OH)], pentametallic Mn oxido cluster complexes [M'Mn_4O_2] incorporating redox inactive metals (M' = Ca^+, Sr^(2+), Y^(3+), La^(3+)) have been prepd. Structure, redox properties, and spectroscopy of such complexes will be discussed.