Isomer transformation and photoluminescence in novel coordination polymers constructed from 1,4-cyclohexanedicarboxylic acid and imidazole

Three novel coordination polymers [M(chdc)(imi)]_n (chdc=1,4-cyclohexanedicarboxylic dianion, imi=imidazole, M=Ni 1, Co 2 and Zn 3) have been synthesized by solvothermal technique and characterized by elemental analysis, IR and single-crystal X-ray diffraction. The trans-chdc have been partially transformed into cis-chdc and the cis-chdc have been separated from the mixture of cis- and trans-chdc in the synthetic reactions of the three compounds. The three compounds exhibit similar one dimension chain-like architecture constructed by their M(II) dimers interconnected via double strands of cis-chdc-bridge. M(II) atom of the dimer exhibits a square-pyramidal geometry and interaction happens within two metal centers. Both compounds 1 and 2 do not exhibit emission spectra whereas compound 3 shows intense photoluminescence property at room temperature.