Syntheses, structures, and photoluminescence of three cadmium(II) coordination polymers with flexible bis(benzimidazole) ligands

Three cadmium(II) coordination polymers, [CdBr2(L-1)](n) (1), [CdI2(L-2)](n) (2), and Cd2Br4(L-3)(2) (3), where L-1 = 1,3-bis(5,6-dimethylbenzimidazole)propane, L-2 = 1,4-bis(5,6-dimethylbenzimidazole)butane, and L-3 = 1,6-bis(5,6-dimethylbenzimidazole)hexane, have been synthesized by hydrothermal methods and characterized by elemental analyses, IR spectra, TGA, PXRD, and X-ray crystallographic diffraction. Complex 1 contains a 1-D helical chain in which CdBr2 units are linked by L-1. For 2, each CdI2 is connected by two different conformations of L-2 to form a 1-D zigzag chain. For 3, each CdBr2 is linked by L-3 bridges to afford a binuclear structure. These results indicate that the spacer length of the ligands play important roles in assembly of Cd(II) coordination polymers. Thermogravimetric analyses and solid-state luminescent properties of the complexes have also been investigated.