Preparation, Crystal Structure And Properties Of Metal-Organic Coordination Compounds Based On N And O-containing Ligands

Metalorganic coordination polymers are formed by the coordination bonds between organic ligands and metal ions. Diversified structures of the coordination polymers resulted in unusual properties of the novel materials.In this thesis, seven metal-organic coordination polymers with novel structures were hydrothermally synthesized. Structures and thermal stabilization of these coordination polymers were characterized by infrared spectra, elemental analysis, X-ray single crystal diffraction and thermal gravity methods. The main contents are as follows:1. 2,2'-bipyridine was used to synthesize one simple metal-organic coordination polymerâ… :[Cu₄(bpy)₄(OH)₄]Cl₄·6H₂O. Benzendicaiboxylic acids were then added to synthesize coordination polymersâ…¡:[Cu₂(C₁₀H₈N₂)₂(C₈H₄O₅)₂(H₂O)₂] andâ…¢:{[Cu₂(bpy)(tpa)₂(bpy)]·H₂O}_n. Among them,â… is tetra-nuclears structure which contains abundant inter-molecular hydrogen bonds O-H…Cl and O-H…O. These hydrogen bonds alternatively formed six-member and eight-member rings along b direction.â…¡has a novel three-dimensional network with a kind of binuclear-centered structure. In the process of synthesizingâ…¡, isophthalic acid underwent in-situ oxidative hydroxylation before coordinating with Cu (â…¡) ion, proving that coordination compounds with novel structures are easily achieved by hydrothermal synthesis. The three-dimensional network ofâ…¢is constructed by inter-molecular hydrogen bonds andÏ€-Ï€stacking interactions existing between two parallel "zigzag" chains in two different directions.2. Nicotinic acid was chosen as the ligand which contains N and O as the coordination atoms. Coordination polymersâ…£:[Cu(NcA)₂]_∞andâ…¤:[Cu(NcA)₂(H₂O)₄] were synthesized. Due to the different bond abilities of N and O with Cu(â…¡), the structures ofâ…£andâ…¤are different from each other. Inâ…£, both N and O were bonded with Cu(â…¡) while only N did so inâ…¤. Besides, the structure ofâ…£is three-dimensional which was constructed by covalent bonds and coordinated bonds whileâ…¤has a two-dimensional face structure extended by O-H…O hydrogen bonds andÏ€-Ï€stacking interactions.3. On the basis of the synthesis ofâ…¤, rare earth metal ions were added which have stronger bond abilities with O compared with N. One heteronuclear coordination polymerâ…¥[LaCu₃(C₈H₃O₅)₃(H₂O)₃]_n and one rare earth metal-organic coordination polymerâ…¦[Nd₂(C₈H₆O₄)₄(H₂O)]·H₂O were synthesized. Inâ…¥, isophthalic acid was also in-situ oxidative hydroxylated like that inâ…¡. While inâ…¦which was produced by liquid diffusion isophthalic acid was directly coordinated with Nd(â…¢). Because the coordination number of rare earth metal ions is usually high, so a plenty of coordinated water molecules existed inâ…¥andâ…¦, which further formed abundant hydrogen bonds. These hydrogen bonds helped to stabilize the structures ofâ…¥andâ…¦while at the same time extended them into three-dimensional networks.