Crystal structure ofcatena-poly[[(dimethyl sulfoxide-κO)(pyridine-2,6-dicarboxylato-κ3O,N,O′)nickel(II)]-μ-pyrazine-κ2N:N′]

Abstract

The title coordination polymer, [Ni(C7H3NO4)(C4H4N2)(C2H6OS)]n, consists of [010] chains composed of NiIIions linked by bis-monodentate-bridging pyrazine molecules. Each of the two crystallographically distinct NiIIions is located on a mirror plane and is additionally coordinated by a dimethyl sulfoxide (DMSO) ligand through the oxygen atom and by a tridentate 2,6-pyridine-dicarboxylic acid dianion through one of each of the carboxylate oxygen atoms and the pyridine nitrogen atom, leading to a distorted octahedral coordination environment. The title structure exhibits an interesting complementarity between coordinative bonding and π–π stacking where the Ni—Ni distance of 7.0296 (4) Å across bridging pyrazine ligands allows the pyridine moieties on two adjacent chains to interdigitate at halfway of the Ni—Ni distance, resulting in π–π stacking between pyridine moieties with a centroid-to-plane distance of 3.5148 (2) Å. The double-chain thus formed also exhibits C—H...π interactions between pyridine C—H groups on one chain and pyrazine molecules on the other chain. As a result, the interior of the double-chain structure is dominated by π–π stacking and C—H... π interactions, while the space between the double-chains is occupied by a C—H...O hydrogen-bonding network involving DMSO ligands and carboxylate groups located on the exterior of the double-chains. This separation of dissimilar interactions in the interior and exterior of the double-chains further stabilizes the crystal structure.