Poly[([mu]4-2,5-dimethoxybenzene-1,4-dicarboxylato)manganese(II)] and its zinc(II) analogue: three-dimensional coordination polymers containing unusually coordinated metal centres

The title compounds, [Mn(C10H8O6)]n and [Zn(C10H8O6)]n, are isomorphous coordination polymers prepared from 2,5-dimethoxyterephthalic acid (H2dmt) and the respective metal(II) salts. Both complexes form three-dimensional metal-organic frameworks with each MII centre bridged by four 2,5-dimethoxyterephthalate (dmt2-) anions, resulting in the same type of network topology. The asymmetric unit consists of one MII cation on a twofold axis and one half of a dmt2- anion (located on a centre of inversion). In the crystal structure, the MII centres are coordinated in a rather unusual way, as there is a distorted tetrahedral inner coordination sphere formed by four carboxylate O atoms of four different dmt2- anions, and an additional outer coordination sphere formed by two methoxy and two carboxylate O atoms, with each of the O atoms belonging to one of the four different dmt2- anions forming the inner coordination sphere. Consideration of both coordination spheres results in a super-dodecahedral coordination geometry for the MII centres. Besides the numerous MII...O interactions, both structures are further stabilized by weak C--H...O contacts. [PUBLICATION ABSTRACT]