Synthesis,Characterization And Properties Of Transition Metal Coordination Polymers Based On Carboxylic Acids And Nitrogen Heterocyclic Ligands Qian-Kun Zhou (Inorganic Chemistry)

Coordination polymers is a class of important inorganic-organic hybrid material that composed of inorganic metal ions and organic ligands.The self-assembly of N-heterocyclic ligands,carboxylic acids and transition metal ions is an effective method to form infinite periodic crystal materials with desired structures.Due to the abundant coordination sites of N-heterocyclic ligands and multi-dentate carboxylates,coordination polymers with novel structure,stable skeleton and special functions can be constructed more easily with transition metal ions through coordination bonds and other weak interactions.In this thesis,five novel coordination polymers were successfully prepared based on N-heterocyclic ligands and multi-dentate carboxylates and transition metal ions.The structures and properties of these coordination polymers were characterized by single-crystal X-ray diffraction,powder x-ray diffraction,fluorescence spectra,elemental analyses,IR spectroscopy and thermogravimetry.The main research results are summarized as follows:1.A three-dimensional coordination polymer{[Cd₂?1,3,5-HBTC?₂?1,4-btbe?·2H₂O]}_n?1?has been synthesized by the hydrothermal reaction between Cd?NO₃?₂·4H₂O,1,3,5-benzenetricarboxylic acid?1,3,5-H₃BTC?and 1,4-bis?1,2,4-triazol-1-yl?but-2-ene?1,4-btbe?.Single-crystal X-ray diffraction analysis showed that each Cd^II center is located in a distorted trigonal-bipyramidal coordination environment,coordinated by three O atom from three different 1,3,5-H₂BTC^2-ligands and two N atoms from two different 1,4-btbe ligands,forming a three-dimensional framework.From a topological viewpoint,each dinuclear Cd₂ unit can be regarded as a 6-connected node and each tetradentate 1,4-btbe ligand can be considered as a 4-connected node.Therefore,the whole architecture of 1 can be simplified as a complicated three-dimensional?4,6?-connected framework.2.A new supramolecular compound{?1,4-H₂bpbd?[Cd?1,2,4,5-btc?]}_n?2?has beenpreparedbytheself-assemblyofCd?NO₃?₂·4H₂O,1,2,4,5-benzenetetracarboxylic acid?1,2,4,5-H₄btc?and 1,4bis?pyridine-4-yl?buta-1,3-diene?1,4-bpbd?under hydrothermal conditions.Single-crystal X-ray analysis reveals that each Cd^II centre coordinated with six carboxylate O atoms from four different 1,2,4,5-btc^4-tetraanions,forming an infinite three-dimensional coordination network of[Cd?1,2,4,5-btc?]^2-with tubular channels.To balance the negative charge of the metal-carboxylate coordination network,the protonated 1,4-H₂bpbd²⁺cations connected the anionic coordination network through strong hydrogen bonding interactions,giving a stable three-dimensional supramolecular framework.3.A new supramolecular compound[Zn?1,4-ndc??3,3'-bphte?]_n?3?has been prepared by the self-assembly of Zn?NO₃?₂·6H₂O,1,4-naphthalenedicarboxylic acid?1,4-H₂ndc?and1,6-bis?pyridine-3-yl?-1,3,5hexatriene?3,3'-bphte?under hydrothermal conditions.Single-crystal X-ray analysis reveals that each Zn^II ion is located in an octahedral coordination environment,coordinated by four carboxylate O atom from three different 1,4-ndc^2-ligands and pyridyl N atoms from two 3,3'-bphte molecules.Each pair of Zn^II ion is interconnected through 1,4-ndc^2-ligands to generate a two-dimensional square lattice layer of[Zn?1,4-ndc?]_n extending in ab plane.Then the 3,3'-bphte ligands connect adjoining[Zn?1,4-ndc?]_n layers to form an infinite three-dimensional coordination network.4.A one-dimensional comb-like photoreactive coordination polymer{[Zn?OH₂??5-Cl-1,3-bdc??2,3'-bpe?]·H₂O}_n?4?has been prepared by the self-assembly of Zn?NO₃?₂·6H₂O,5-chlorine-1,3-benzenedicarboxylic acid?5-Cl-1,3-H₂bdc?and trans-1-?2-pyridyl?-2-?3-pyridyl?-ethylene?2,3'-bpe?under hydrothermal conditions.Such a coordination polymer could undergo[2+2]photodimerization reaction through single-crystal-to-single-crystal?SCSC?transformation upon UV irradiation.Finally,a novel ladder-like compound{[Zn?OH₂??5-Cl-1,3-bdc??HT-bpbpcb?_0.5]·H₂O}_n?5?was obtained.Accompanied by the SCSC transformation,the 2,3'-bpe molecules in the coordination polymer were dimerized into the 1,3-bis?2-pyridyl?-2,4-bis?3-pyridyl?cyclobutane?HT-bpbpcb?molecules.