Synthsis, structures and magnetic properties of three new coordination polymers constructed by mixed-linker strategy

Abstract

By the reaction of a rigid π-conjugated linker of H4L (5,5′-(1,3,6,8-tetraoxobenzo [lmn] [3,8] phenanthroline-2–7- diyl) bis-1,3-benzenedicarboxylic acid), nickel nitrate and N-donor auxiliary linkers under solvothermal conditions, three new Ni-based coordination polymers (CPs), namely {[Ni(L)0.5(1,4-bib)(H2O)2]·2·5H2O·DMA}n (1), {[Ni(H2L)(4,4′-bibp)(H2O)2]}n (2) and {[Ni(L)0.5(4,4′-bimb)(H2O)2]·3·5H2O·2DMA}n (3) {1,4-bib = 1,4-bis(1-imidazoly)benzene, 4,4′-bibp = 4,4′-bis(imidazolyl)biphenyl, 4,4′-bimb = 4,4′-bis(imidazol-1-ylmethyl) biphenyl} have been synthesized and characterized by EA, TG, IR, PXRD and magnetic properties. The structural analysis indicates both 1 and 2 are 2D layer structures, which are further extended to 3D supramolecular structures by H-bonding and intermolecular π…π interactions. While 3 exhibits a complicated 3D structure with the topology symbol of {64.82}. The difference of the structures in CPs 1–3 is mainly attributed to different auxiliary linkers used. Meanwhile, magnetic properties of CPs 1–3 show that the descent of χMT values is attributed to zero-field splitting (ZFS) effects of Ni2+ ions. In addition, on account of large Ni2+ Ni2+ separations within these frameworks, magnetic interactions between adjacent Ni2+ ions can be neglected.