Synthesis, crystal structure and physical properties of a novel cadmium(II) supramolecular 3D framework

A new inorganic-organic hybrid cadmium(II) complex [Cd₂(H_1/2C₄BIm)₂(CH₃COO)]n has been prepared by a hydrothermal reaction, and characterized by fluorescence, IR, TGA, and single-crystal X-ray diffraction analysis. In its crystal structure, there are two kinds of coordinating forms for those Cd(II) ions. One is that the Cd(II) ion is coordinated by one carboxylate oxygen atom from one acetate oxygen ligand and three benzimidazole nitrogen atoms from three 2,2'-(1,4-butanediyl)bis (1H-benzimidazole) (H₂C₄BIm) ligands, and the other is that the Cd(II) ion is coordinated by four benzimidazole nitrogen atoms from four H2C4BIm ligands to furnish two distorted tetrahedral coordination geometries. It exhibits a beautiful structure for a 2D layer and a 3D network, with its four-connecting nodes provided by the H2C4BIm ligands. Furthermore, this complex shows intense luminescent property at room temperature. In [Cd₂(H₂C₂BIm)₂(C₉H₆O₄)₂]_n, the H₂C₂BIm ligand lost the role as a bridging ligand because of the shorter alkyl chain compared with that of H₂C₄BIm ligand.