Two-dimensional ZnIIand one-dimensional CoIIcoordination polymers based on benzene-1,4-dicarboxylate and pyridine ligands

Abstract

Coordination polymers constructed from metal ions and organic ligands have attracted considerable attention owing to their diverse structural topologies and potential applications. Ligands containing carboxylate groups are among the most extensively studied because of their versatile coordination modes. Reactions of benzene-1,4-dicarboxylic acid (H2BDC) and pyridine (py) with ZnIIor CoIIyielded two new coordination polymers, namely, poly[(μ4-benzene-1,4-dicarboxylato-κ4O:O′:O′′:O′′′)(pyridine-κN)zinc(II)], [Zn(C8H4O2)(C5H5N)]n, (I), andcatena-poly[aqua(μ3-benzene-1,4-dicarboxylato-κ3O:O′:O′′)bis(pyridine-κN)cobalt(II)], [Co(C8H4O2)(C5H5N)2(H2O)]n, (II). In compound (I), the ZnIIcation is five-coordinated by four carboxylate O atoms from four BDC2−ligands and one pyridine N atom in a distorted square-pyramidal coordination geometry. Four carboxylate groups bridge two ZnIIions to form centrosymmetric paddle-wheel-like Zn2(μ2-COO)4units, which are linked by the benzene rings of the BDC2−ligands to generate a two-dimensional layered structure. The two-dimensional layer is extended into a three-dimensional supramolecular structure with the help of π–π stacking interactions between the aromatic rings. Compound (II) has a one-dimensional double-chain structure based on Co2(μ2-COO)2units. The CoIIcations are bridged by BDC2−ligands and are octahedrally coordinated by three carboxylate O atoms from three BDC2−ligands, one water O atom and two pyridine N atoms. Interchain O—H...O hydrogen-bonding interactions link these chains to form a three-dimensional supramolecular architecture.