Linkage isomerism for 4-methylimidazole and a new coordination mode of pyrazine-2,3-dicarboxylate ligand in {[Cd(pzdc)(4-mim)(5-mim)2]·½H2O}n coordination polymer

A novel one dimensional coordination polymer of Cd(II)-pyrazine-2,3-dicarboxylate with a new coordination mode of pyrazine-2,3-dicarboxylate ligand (pzdc), {[Cd(pzdc)(4-mim)(5-mim)2]·½H2O}n (1) (4(5)-methylimidazole = 4(5)-mim), has been synthesized and characterized by elemental, thermal analysis, IR spectrum and single crystal X-ray diffraction technique. In complex 1, the Cd(II) ion has a distorted octahedral geometry, in which the pzdc moiety acts as a bridging ligand. Linkage isomerism of the coordinated 4(5)-methylimidazole ligand was observed in 1. The two adjacent one-dimensional chains connected by interchain hydrogen bonds among the N-H groups of methylimidazoles and carboxylate oxygens of pzdc, leading to a three-dimensional framework. The hydrogen bonds account for the coexistence of two unique coordination forms of methylimidazoles in the same coordination sphere.