A new three-dimensional zinc(II) coordination polymer involving 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-benzimidazole and benzene-1,4-dicarboxylate ligands

摘要

Metal-organic frameworks (MOFs) based on multidentate N-heterocyclic ligands involving imidazole, triazole, tetrazole, benzimidazole, benzotriazole or pyridine present intriguing molecular topologies and have potential applications in ion exchange, magnetism, gas sorption and storage, catalysis, optics and biomedicine. The 2-[(1H-1,2,4-triazol-1-yl)methyl]-1H-benzimidazole (tmb) ligand has four potential N-atom donors and can act in monodentate, chelating, bridging and tridentate coordination modes in the construction of complexes, and can also act as both a hydrogen-bond donor and acceptor. In addition, the tmb ligand can adopt different coordination conformations, resulting in complexes with helical structures due to the presence of the flexible methylene spacer. A new three-dimensional coordination polymer, poly[[bis(μ_2-benzene-1,4-dicarboxylato)-κ~4O~1,O~1':O~4,O~4'; κ~2O~1:O~4-bis{μ_2-2-[(1H-1,2,4-triazol-1-yl)methyl-κN~4]-1H-benzimidazole-κN3}dizinc(II)] trihydrate], {[Zn(C_8H_4O_4)-(C_10H_9N_5)]-1.5H_2O}_n, has been synthesized by the reaction of ZnCl_2 with tmb and benzene-1,4-dicarboxylic acid (H_2bdic) under solvothermal conditions. There are two crystallographically distinct bdic~2- ligands [bdic~2-(A) and bdic~2-(B)] in the structure which adopt different coordination modes. The Zn~II ions are bridged by tmb ligands, leading to one-dimensional helical chains with different handedness, and adjacent helices are linked by bdic~2-(A) ligands, forming a two-dimensional network structure. The two-dimensional layers are further connected by bdic~2-(B) ligands, resulting in a three-dimensional framework with the topological notation 6~6. The IR spectra and thermogravi-metric curves are consistent with the results of the X-ray crystal structure analysis and the title polymer exhibits good fluorescence in the solid state at room temperature.