Two novel coordination polymers with different molecular tectonics based on zinc nitrate and bisimidazole ligand

Two new coordination polymers, [Zn(2-mBIM)2(NO3)2(H2O)2]n (1) and [Zn(BIM)2(NO3)2(H2O)2]n (2) (2-mBIM = bis(2-methylimidazol-1-yl)methane, BIM = bis(imidazol-1-yl)-methane), were synthesized by the reactions of Zn(NO3)2 with 2-mBIM and BIM ligands. They were characterized by elemental analyses, IR, TGA and X-ray single-crystal diffraction techniques. Each of metal centers in 1 and 2 is coordinated in a slightly distorted tetrahedral geometry by four aromatic nitrogen atoms from four distinct 2-mBIM or BIM ligands, respectively. In compound 1, each pair of neighboring ZnII centers is bridged by two 2-mBIM ligands to form a 16-membered macrometallacyclic structural motif. Each 2-mBIM ligand is coordinated to two ZnII cations and acts as a bridged ligand to form a one-dimensional polymeric cationic chain structure. Compound 2 has a 2D network structure containing 1D channel, thereby each BIM ligand is coordinated to two ZnII cations and thus acts as a bridging ligand. Moreover, each group of four BIM ligands is linked alternatively to each other by four ZnII cations, resulting in a 32-membered macrometallacycle.