Crystal structure of catena-poly[[(dimethyl sulfoxide-κO)(pyridine-2,6-di­carboxyl­ato-κ3 O,N,O′)nickel(II)]-μ-pyrazine-κ2 N:N′]

The title coordination polymer, [Ni(C7H3NO4)(C4H4N2)(C2H6OS)] n , consists of [010] chains composed of Ni(II) ions linked by bis-monodentate-bridging pyrazine mol-ecules. Each of the two crystallographically distinct Ni(II) ions 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-di-carb-oxy-lic acid dianion through one of each of the carboxyl-ate oxygen atoms and the pyridine nitro-gen atom, leading to a distorted octa-hedral coordination environment. The title structure exhibits an inter-esting 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 inter-digitate 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 inter-actions between pyridine C-H groups on one chain and pyrazine mol-ecules on the other chain. As a result, the inter-ior of the double-chain structure is dominated by π-π stacking and C-H⋯ π inter-actions, while the space between the double-chains is occupied by a C-H⋯O hydrogen-bonding network involving DMSO ligands and carboxyl-ate groups located on the exterior of the double-chains. This separation of dissimilar inter-actions in the inter-ior and exterior of the double-chains further stabilizes the crystal structure.