Study On Synthesis And Performance Of Coordination Polymers Based On 2,6-pyridinedicarboxylic Acid Derivatives

In recent years,based on the excellent properties of transition and rare earth metal coordination polymers,their research has received extensive attention,and they are often used in fields such as luminescence,magnetism,catalysis,sensing and bioimaging.After the transition metal reacts with the organic ligand,it can enhance the luminescence performance of the ligand by enhancing the conjugation effect and rigidity of the system to further develop its potential in fluorescent luminescence sensors,while rare earth ions have sharp emission bands,longer luminescence lifetime,larger Stokes shift and high quantum yield,etc.At the same time,rare earth coordination polymers have excellent properties in terms of light,electricity and magnetism.Multi-branched pyridine carboxylic acid ligands have the advantages of abundant coordination sites and high absorption coefficient.When it reacts with metal ions,they can construct coordination polymers with novel structures through the coordination mode of chelating or bridging.In this paper,with the goal of function orientation,a new ligand of multi-branched pyridinecarboxylic acid with benzene ring as the central skeleton and 2,6-pyridinedicarboxylic acid as the terminal group was designed and synthesized,and it was obtained by reacting with rare earth or transition metal.Coordination polymers with novel structures,and their structure and luminescence properties have been systematically studied.Taking into account the high stability of the structure and luminescence of the obtained coordination polymers in water,the luminescence response to metal ions and nitro aromatic explosives in water systems were further explored.The main content of this paper is divided into the following four parts:1.Summarized the research status of transition metals and rare earth coordination polymers and the topic and significance of this paper;2.The polydentate ligand H₄L with benzene ring as the central skeleton and 2,6-pyridinedicarboxylic acid as the terminal group was synthesized with leucoidine as the starting reactant.The ligand H₄L and Zn(NO₃).6H₂O and Cu(NO₃)₂.3H₂O were obtained by solvothermal method to obtain a series of transition metal coordination polymers of the ligands,which were characterized by infrared,thermogravimetric,and X-ray diffraction.The analysis of structure shows that the while the Zn coordination polymer is one-dimensional chain structure and the Cu coordination polymer is two-dimensional network structure.The 3D supramolecular structure of Cu coordination polymer is formed by hydrogen bond between the uncoordinated carboxylic acid group in the Cu coordination polymer and the coordinated water molecule in the adjacent layer.The fluorescence properties of zinc coordination polymers have been studied:Zn²⁺can enhance the luminescence properties of ligand H₄L.This coordination polymer has high water stability and can selectively identify picric acid in water and it also can be used as a excellent fluorescence sensor for medium picric acid in water.3.The ligand H₄L and Ln(NO₃)₂.6H₂O(Ln=Eu,Tb)were used to obtain a series of rare earth coordination polymers by solvothermal method.They were characterized by infrared,thermogravimetric,X-ray diffraction.The structural analysis shows that the series of rare earth coordination polymers are isomorphic,and they all have two sizes of one-dimensional pores and novel topological symbols.The fluorescence properties of two rare earth coordination polymers were studied:the ligand H₄L showed complete sensitization to Tb³⁺and Eu³⁺.Based on the purpose of expanding the luminescence application of this type of coordination polymers,the luminescence performance of the series of rare earth coordination polymers were studied firstly,and the results show that they owning to high water stability and thermal stability.They also can detect Cu²⁺and 4-nitrophenol with high selectivity and high sensitivity in aqueous media.It is a promising luminescence sensor for detecting Cu²⁺and 4-nitrophenol in a water system.4.Summary and prospects:In this paper,a series of new pyridinecarboxylic acid transition metal and lanthanide coordination polymers have been synthesized,and the relationship between their structure and fluorescence sensing properties has been discussed.The results laid the foundation for the development of 3d-4f heterometallic coordination polymers with better structure and performance.