Preparation And Properties Of Coordination Polymers Based On Bipyridine Ligands And Polycarboxylic Acids

In recent years,as a large number of coordination polymers with special spatial structures and excellent properties have been synthesized,such inorganic-organic hybrid crystalline materials have attracted more and more attention.A large number of functional materials with unique regular pores,regular spatial topologies and periodic network structures can be formed by the self-assembly of metal ions and multidentate organic ligands.Functional crystalline material of network structure.At present,coordination polymers have shown good application prospects in many fields such as photoluminescence,catalysis,adsorption,separation,magnetism and electrochemistry.The choice of organic ligands usually has a decisive influence on the structure of a coordination polymer.Among the commonly used organic ligands,the nitrogen heterocyclic organic ligand and the multidentate carboxylate ligands are a very bright combination.As one of the multidentate O-type donor ligands,multidentate carboxylic acids are good candidates for building coordination polymers.Multidentate carboxylic acid ligands can balance the positive charge of metal ions and significantly enhance the stabilities of the products.In addition,multidentate carboxylates can adopt multiple coordination modes to form various metal carboxylate units,and thus provide unlimited possibilities for synthesizing coordination polymers with multiple spatial structures.In this thesis,we selected multidentate carboxylic acids,transition metal ions and bispyridyl ligands to construct eight coordination polymers with unique spatial topologies through hydrothermal reactions.The coordination polymers have been characterized and their spatial structures were determined by single crystal X-ray diffraction.The main contents of the thesis are described as follows:1.Select the bispyridine ligand trans-1-（2-amino-pyridin-3-yl）-2（pyridin-4-yl）ethene（2-NH₂-3,4-bpe）.Two similar dicarboxylic acids,5-methylisophthalic acid（5-Me-H₂ip）,5-hydroxyisophthalic acid（5-HO-H₂ip）and Cd（NO₃）₂·4H₂O,two coordination polymers Cd（5-Me-ip）（2-NH₂-3,4-bpe）]_n（1）,[Cd（5-HO-ip）（2-NH₂-3,4-bpe）]_n（2）with different structures were constructed by hydrothermal reactions.Single crystal X-ray diffraction analysis showed that the coordination polymer1 is a three-dimensional supramolecular network structure,and the coordinatio n polymer 2 is a thick two-dimensional planar network structure.As the other reactants and reaction conditions are same,the structural difference between 1and 2 is mainly determined by the different substituents at the 5-position of is ophthalic acid.Fluorescence spectra and thermogravimetric analysis show that t hese two coordination polymers show good thermal stabilities and photolumines cence properties.2.Select the bipyridine ligand 2-NH₂-3,4’-bpe,the transition metal ion Co（II）,the polydentate carboxylic acid 1,2,4,5-benzenetetracarboxylic acid（1,2,4,5-H₄BTC）and1,4-naphthalenedicarboxylic acid（1,4-H₂NDC）.The coordination polymer was constructed by hydrothermal synthesis,and finally two new coordination polymers with periodic topology were obtained:[Co（1,2,4,5-BTC）（2-NH₂-3,4’-Hbpe）₂]_n（3）,[Co（1,4-NDC）（2-NH₂-3,4’-bpe）]_n（4）.3 is a one-dimensional chain structure,and 4forms a four-dimensional three-dimensional interspersed adamantane-like network coordination polymer through self-assembly.Because both coordination polymers are prepared under the same synthetic conditions,their final structural differences can be attributed to the different carboxylic acid ligands that have a critical effect on the polymerization during self-assembly.3.Select the bipyridine ligand 2-NH₂-3,4’-bpe,the transition metal ion Zn（II）and four carboxylic acids:1,3,5-pyrimellitic acid（1,3,5-H₃BTC）,2,6-naphth alenedicarboxylic acid（2,6-H₂NDC）,5-methylisophthalic acid（5-Me-1,3-H₂BDC）,5-chloroisophthalic acid（5-Cl-1,3-H₂BDC）to build four coordination polymers:[Zn（1,3,5-BTC）（2-NH₂-3,4’-Hbpe）]_n（5）[Zn（2,6-NDC）（2-NH₂-3,4’-bpe）]_n（6）[Zn（5-Me-1,3-BDC）（2-NH₂-3,4’-bpe）]_n（7）[Zn（5-Cl-1,3-BDC）（2-NH₂-3,4’-bpe）]_n（8）Coordination polymer 5 forms a two-dimensional（4,4）grid structure.In 6,due to its two-dimensional structure with larger channels,a three-dimensional structure with 2D→3D interspersion is finally formed.In 7 and 8,both pyridyl groups of2-NH₂-3,4’-bpe participate are coordinated with metal ions,and both coordination polymers eventually form a similar two-dimensional（4,4）grid.The results indicate that the structures of the coordination polymers can be regulated by selecting different carboxylate ligands.