Poly[(μ4-2,5-dimethoxybenzene-1,4-dicarboxylato)manganese(II)] and its zinc(II) analogue: three-dimensional coordination polymers containing unusually coordinated metal centres

Abstract

The title compounds, [Mn(C(10)H(8)O(6))](n) and [Zn(C(10)H(8)O(6))](n), are isomorphous coordination polymers prepared from 2,5-dimethoxyterephthalic acid (H(2)dmt) and the respective metal(II) salts. Both complexes form three-dimensional metal-organic frameworks with each M(II) centre bridged by four 2,5-dimethoxyterephthalate (dmt(2-)) anions, resulting in the same type of network topology. The asymmetric unit consists of one M(II) cation on a twofold axis and one half of a dmt(2-) anion (located on a centre of inversion). In the crystal structure, the M(II) 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 dmt(2-) 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 dmt(2-) anions forming the inner coordination sphere. Consideration of both coordination spheres results in a super-dodecahedral coordination geometry for the M(II) centres. Besides the numerous M(II)···O interactions, both structures are further stabilized by weak C-H···O contacts.