Syntheses, crystal structures, and properties of complexes constructed with polybenzoate and 2,2′-bibenzimidazole

Abstract

Six new complexes constructed with polybenzoate and 2,2′-bibenzimidazole, namely, [Co(H2bibzim)(1,4-bdc)] (1), [Ni(H2bibzim)(1,4-bdc)] (2), [Co(H2bibzim)2(1,3-bdc)]·H2O (3), [Co4(H2bibzim)3(Hbibzim)2(1,3,5-btc)2·2H2O]·5H2O (4), [Co2(H2bibzim)4(1,2,4,5-btec)] (5), and [Ni(H2bibzim)3](1,4-bdc)·3H2O (6) (bdc = benzenedicarboxylate, H2bibzim = 2,2′-bibenzimidazole, btc = benzenetricarboxylate, btec = benzenetetracarboxylate) have been synthesized by hydrothermal methods and characterized by single crystal X-ray diffraction. Complexes 1 and 2 are isomorphous. Both crystallize in the monoclinic space group P21/c and feature 1-D “zigzag” chains, which can be further arranged into undulating sheets in a zipper-like fashion through π-π and hydrogen bonding interactions. Complex 3 belongs to the P21/c space group. Each Co(II) atom coordinates to one 1,3-bdc and two H2bibzim ligands. With the help of strong N–H⋯O hydrogen bonding interactions between H2bibzim and neighboring 1,3-bdc, a 2-D network with windows of about 14.8 × 18.2 Å can be formed with [Co(H2bibzim)2(1,3-bdc)] dimers as building blocks. Complex 4 belongs to the Cc space group and features a 3-D framework. Interestingly, two of the five H2bibzim are deprotonated into Hbibzim− and act as bridging ligands. Complex 5 crystallizes in P-1, the dinuclear units are connected into a 2-D sheet through π–π and hydrogen bonding interactions, forming a molecular zipper synchronously. Complex 6 crystallizes in P21/n, the nickel atom is six coordinated by three H2bibzim ligands, and the terephthalate (tp) groups act as counterions, connecting the coordination cations into a 3-D framework through N–H⋯O hydrogen bonding interactions. The thermal stabilities of complexes 1–6 were examined. The temperature-dependent magnetic susceptibilities of complexes 1, 2 and 4 were also studied.