Syntheses and characterization of nickel(II) and cobalt(II) coordination polymers based on 5-bromoisophthalate anion and bis(imidazole) ligands

Four new Ni-II and Co-II complexes, [Ni(5-Br-ip)(bip)(H2O)](n) (1), [Ni(5-Br-ip)(bib)](n) (2), [Co(5-Br-ip) (bip)](n) (3) and [Co(5-Br-ip)(bip)](n) (4) (5-Br-H(2)ip = 5-bromoisophthalic acid, bip = 1,3-bis(imidazol) propane, bib = 1,4-bis(imidazol)butane), have been synthesized and structurally characterized by elemental analysis, IR and single-crystal X-ray diffraction. Complex 1 features a 2D double layer extended by the intermolecular hydrogen bonds between 2D layers. Complex 2 shows a 2-fold interpenetrating 3D -> 3D network based on the dinuclear Ni(II) units. Complexes 3 and 4 can be regarded as supramolecular structural isomers. Isomer 3 possesses a 1D chain structure with binuclear Co units as subunits. Isomer 4 shows a 3D network and can be reduced to a 4-connected net with the (6(5).8) topology. The structural differences indicate that the backbone of the organic N-donor ligands and the nature of the metal ions play important roles in governing the structures of such metal-organic coordination architectures. Moreover, the magnetic properties of complexes 2 and 3 were also studied in 2-300 K.