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

Abstract

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-H₂ip = 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 (6⁵.8) 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.