Synthesis, crystal structures, and magnetic properties of three nickel (II) coordination polymers based on a rigid pyrazine carboxylic acid containing different N ligands

Three novel nickel (II) coordination polymers [Ni3(L)2(4,4′-bipy)2(NO3)2(H2O)4]n (1), [Ni(L)(4,4′-bipy)0.5]n (2), and [Ni(L)(dib)0.5(H2O)2]n (3) have been successfully constructed using the hydrothermal reactions of Ni(NO3)2·6H2O with 2,4-[6-(4-carboxyphenyl)pyrazin-2-yl]benzoic acid (H2L) and corresponding N-donor ligands, namely, 4,4′-bipyridine (4,4′-bipy) and 1,4-di(1H-imidazole-1-yl) benzene (dib), respectively. Single crystal X-ray analysis reveals that compound 1 exhibits a 3D supramolecular architecture linked by the L2− and 4,4′-bipy ligands, compound 2 possesses a 3D 2-fold interpenetrating framework, and compound 3 displays an infinite 2D framework formed by the L2− and dib ligands. The phase purity, IR spectra, thermal stabilities, and Hirshfeld surface analyses of 1–3 have been investigated. Additionally, the magnetic behaviors for 2–3 have also been studied, revealing weak antiferromagnetic interactions between Ni (II) centers in them.