Different dimensional and structural variations in coordination polymers of d10 metal ions constructed from a benzimidazole based carboxylate linker

Six new coordination polymers, {[Zn(L)2]·(DMF)·(H2O)}n (1), [Zn(L)2]n (2), [Cd2(L)4]n (3), {[Cd(L)(HL)Cl]·(H2O)}n (4), {[Cd(L)(Cl)(DMF)]·(DMF)}n (5) and [Cd(L)2(H2O)2]n (6), where HL = 4-benzimidazole-1-yl-benzoic acid and DMF = N,N’-dimethylformamide, have been synthesized with d10 metal ions under different hydro/solvothermal conditions. The polymers have been characterized by IR spectroscopy, elemental, thermogravimetric analyses (TGA) and powder X-ray diffraction (PXRD), and their structures have been determined by single-crystal X-ray diffraction analyses. Structural studies reveal that both 1 and 2 are 2D coordination polymers. The structure of 1 shows a 2-fold interpenetrated (4,4) net topology, while that of 2 is composed of infinite carboxylate-bridged Zn(II) chains running along the crystallographic a-axis. When the ligand HL is treated with cadmium nitrate, 3 and 6 are formed under hydrothermal and solvothermal conditions respectively. Compound 3 has a 3D structure having infinite carboxylate-bridged Cd(II) chains while 6 is a 1D coordination polymer. However, when a chloride salt of Cd(II) is used, compounds 4 and 5 are obtained, which contain chloride-bridged Cd(II) dimers which are further bonded to the ligand to form 1D chains. Thus, depending upon the nature of the counter-anion or the reaction conditions, a variety of 1D, 2D and 3D coordination polymers of Zn(II) and Cd(II) are formed.

Graphical abstractA series of 1D, 2D and 3D coordination polymers of d10 metal ions have been synthesized under different hydro/solvothermal conditions. Due to the variety of conformations of the ligand HL and the flexibility of the metal ions, different supramolecular architectures have been obtained.Figure optionsDownload full-size imageDownload as PowerPoint slide