Crystal structure of catena-poly[[(dimethyl sulfoxide-κO)(pyridine-2,6-di­carboxyl­ato-κ(3) O,N,O′)nickel(II)]-μ-pyrazine-κ(2) N:N′]

The title coordination polymer, [Ni(C(7)H(3)NO(4))(C(4)H(4)N(2))(C(2)H(6)OS)](n), consists of [010] chains composed of Ni(II) ions linked by bis-monodentate-bridging pyrazine mol­ecules. 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-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.