Research On Synthesis Of Metal Organic Frameworks Based On The 4,5-dicyanoimidazole Ligand

Metal-organic frameworks, also known as coordination polymers, are a type of self-assembly coordination compounds formed by organic ligands and metal ions. Due to the wide applications of coordination complexes in photoelectricity, magnetic material, redox catalysis, ion exchange, gas adsorption, separation and molecular recognition etc., much attention has been devoted to the design and synthesis of novel kinds of structural topologies and compounds with special properties.Nitrogen-Containing Heterocyclic Ligands have been widely studied because of their strong coordination ability and varieties of coordination modes. As is known, the ligand conformation and coordination geometries of the metal ion have signifinant influence on the final structures of a MOF, and a little change of the ligand may result in new topological complexes. In this paper, organic compounds containing N-donors were chosen as ligands or coligands to react with transition metal ions and rare-earth metal ions. Nitrogen-Containing Heterocyclic Ligands contain 2H-imidazole-4,5-dicarbonitrile, 4,4'-pyridine and phenanthroline. Seven kinds of metal-organic frameworks with novel structures were obtained by the method of solvothermal (hydrothermal) or diffusion.The structures and thermal stabilizations of the coordination polymers were characterized by many kinds of analysis methods, such as X-ray single crystal diffraction, elementary analysis and thermal gravity analysis. The formulas of the compounds are as follows: Zn(HDTIM)·1.5H₂O(1) [H₂N(CH₃)₂]₄[Zn₈O(HIMDC)6](2) ZnPr(HIMDC)(bpy)(OH)5·(bpy)·4H₂O(3) Pr(HDTIM)(phen)(NO3)(H₂O)·H₂O(4) Mn(HDTIM)(H₂O)₂(5) Ag₂(HIMDC)(H₂O)₂(6) Co(bpy)₂(HIMDN)₂(H₂O)₂·(H₂O)₂·15H₂O(7)All complexes have been determined by single-crystal X-ray diffraction. Complexes 1 and 2 are three-dimensional porous frameworks; Complex 3 belongs to three-dimensional framework; Complex 4 is one-dimensional chain structure; Complexes 5 and 6 are zerodimensional, which generate to three-dimensional networks by hydrogen-bond andÏ€-Ï€stacking interaction; Complex 7 is two-dimensional layers.The results reported herein demonstrated that the use of 2H-imidazole-4,5-dicarbonitrile ligands as precursors to bind transition metal or lanthanide metal ions is a new approach for the formation of novel supramolecular networks with interesting physical properties.