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

Abstract

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.