Synthesis, Structure And Properties Of The Coordination Polymers Of Fiexible Bis(Benzimidazole) Ligands

In this paper, eight novel coordination complexes containing flexible bis(benzimidazole) ligands which have never been reported previously were synthesized. This article represents a systematical examination of their synthesis and structures. In order to survey the influence of anions on the formation of the final structures of coordination complexes, one flexible ligands, 1,1'-(1, 4-butanediyl)bis(2-methylbenzimidazole) (bbmi), and eight kinds of acid, (L1 = benzoic acid , L2 = salicylic acid, L3 = p-Nitrobenzoic acid , L4 = Nicotinic acid, L5 = 3,5-Dinitrobenzoic acid, L6 = o-phthalic acid, L7 = m-Phthalic acid , L8 = Butane diacid) are selected for study, and eight novel compounds have been synthesized: namely [Zn(L1)2(bbmi)] (1), [Zn(L2)2(bbmi)] (2), [Zn(L3)2(bbmi)] (3), [Zn(L4)2(bbmi)(H2O)2] (4),[Zn(L5)2(bbmi)] (5), [Zn(L6)(bbmi)] (6),[Zn(L7)(bbmi)0.5 H2O] (7) and [Zn(bbmi)0.5(L8)(H2O)] (8). The crystal structures have been determined by single-crystal X-ray diffraction. Compounds 1–5 display one-dimensional (1D) chain structures, compounds 1,2,3 and 5 display an infinite helical chain and in compounds 1 and 5π-πinteractions extend the chains to the 2D supramolecular layers. In compound 4, the adjacent polymeric chains are bridged by the hydrogen-bonding interactions to form a 2D supramolecular layer. Furthermore,π-πstacking interactions extends the 2D network into a 3D supramolecular assembly. In compound 6, the L6-Zn chains are connected bbmi ligand to generate a 3D framework with a distorted 66 topology. It is also noteworthy that compound 3 and 6 exhibit 1D chain structures, and these chains were packed as an–ABAB- layered structure. Compound 7 shows a 2D net structure which comprises a [Zn2(CO2)2] unit that is built from two Zn ions and two L7 anions. The structure of 8 is built by bbmi ligands connecting L10-Zn 2D(4,4) networks to a 3D network with a 41263 topology. The structural differences described indicate the importance of carboxylate ligands in framework formation of the coordination complexes. Thermogravimetric analyses (TGA) for compounds(1, 3-7) are discussed.