Syntheses, structures and magnetic properties of cobalt(ii) and nickel(ii) complexes based on 5-methylisophthalate and different dipyridyl-containing ligands

Abstract

Four new Co^II and Ni^II coordination polymers, {[Co(mip)(bpa)]}_n (1), {[Co(mip)(bpp)]}_n (2), {[Ni(mip)(bpa)]}_n (3), {[Ni(mip)(bpp)(H₂O)]}_n (4) (H₂mip = 5-methylisophthalic acid, bpa = 1,2-bi(4-pyridyl)-ethane, bpp = 1,3-di(4-pyridyl)-propane), were prepared viahydrothermal reactions based on H₂mip and two bridging dipyridyl ligands. Their crystal structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses and IR spectra. Complexes 1 and 3 are structurally similar with an infinite bilayer spanning two different directions except for the different central metal ions. The structure of 2 shows a 1D polymeric ribbon due to the GG conformation of the bpp ligand, which is further extended to a 2D supramolecular layer by the C–H⋯π interactions. Complex 4 possesses a two-fold interpenetrating (3,5)-connected hms network constructed from supramolecular interactions. The structural and topological differences of the four complexes demonstrate that the central metal ions and the characteristics of the N-donor auxiliary ligands play significant roles in constructing the novel architectures of coordination polymers. The magnetic properties of 1–4 were studied in the 2–300 K region at 2000 G.