Synthesis, Crystal Structure And Properties Of Metal Complexes Based On Carboxylic Acid Ligands

Due to the intriguing network topologies and potential applications of metal-organic frameworks(MOFs) in the fields of light,electricity, magnetism, catalysis,gas adsorption, etc. They have become one of the hot research realms in coordination chemistry and functional materials. The choices of organic ligands are important for the structures and properties of the MOFs.In addition to the aromatic carboxylic acid ligands have attracted much attention for many researchers because of the special aromatic skeleton structure and extensive coordination mode. Herein, in the thesis, we choose 2,5- dihydroxybenzoic acid and benzenetetracarboxylic acid as organic ligands with various metal ions to synthesize the MOFs and hope to obtain some functional materials.Based on previous work, this thesis selects the 2,5-dihydroxyterephthalic acid(H4-DHBDC) and benzenetetracarboxylic acid(H4bta) as organic ligands with various metal ions to synthesize 11 metal complexes under the conditions of hydrothermal.The composition, crystal structure and thermal stability were analyzed by single crystal X-ray diffraction(SCXRD), elemental analysis(EA), Fourier transform infrared spectrum(FTIR) and thermogravimetry(TG-DTG).In addition, powder diffraction(PXRD),UV-Vis spectrophotometer(UV-Vis) and fluorescence spectroscopy(FS) analysis were performed to characterize some other complexes.The specific contents are as follows:1. The combination of 2,5- dihydroxyterephthalic acid(H4-DHBDC) ligand with rare earth metal ions(Tb3+, Dy3+, Eu3+, Sm3+, La3+) under solvothermal conditions produced five metal organic coordination polymers: {[Ln2(H2-DHBDC)3(H2O)4](H2O)2}n(Ln=Tb(1)、Dy(2)); {[Ln2(H2-DHBDC)3(H2O)4](H2O)}n(Ln=Eu(3)、Sm(4)); {[La2(H2-DHBDC)2(DHBDC)(H2O)6](H2O)2}n(5)。 Complexes 1 and 2, 3 and 4 are isostructural and with different structural types ranging from 1D chain, 2D layer to 3D networks, the structure of complex 5 is a 2D layer.The thermogravimetric analysis exhibited that the complexes have high stability. At last, the UV-Vis spectrophotometer(UV-Vis) and fluorescence spectroscopy(FS) for partial complexes are carried out and the results show that the complexes have better fluorescence properties, where the fluorescence of La(5) is the strongest. It is regarded as a potential fluorescent material.2. Two metal metal-organic complexes {[Nd2(H2-DHBDC)(DHBDC)Cl(H2O)2](phen)0.5(H2O)2}n(6) and {[Nd(H2-DHBDC)(DHBDC)0.5Cl(H2O)2](4,4′-bpy)0.5}n(7) were synthesized with 2,5-dihydroxybenzoic acid ligand and auxiliary ligands under hydrothermal conditions. The complex 6 is Orthorhombic, Fddd space group and the central ion is nine-coordinated tricapped prism configuration. The complex 7 is Triclinic, P-1 space group and the central ion is eight-coordinated dodecahedron configuration. The powder diffraction experiments prove that complex has high purity.3. Three transition metal-organic complexes [Ni(H4bta)0.5(phen)(H2O)]n(8) 、[Co(H4bta)0.5(phen)(H2O)]n(9) 、 [Mn(H4bta)0.5phen]n(10) were synthesized with benzenetetracarboxylic acid ligand and auxiliary ligand Phen under hydrothermal conditions. One rare earth metal-organic complex [Eu((H4bta)(H2O)2]n(11) was synthesized with benzenetetracarboxylic acid ligand under room temperature. Compounds Ni(8) and Co(9) are isomorphism and exhibit 2D layer. The structure of complex Mn(10) is extended to 3D supramolecular frameworks through extensive π…π interactions and that complex Eu(11) is a 3D framework with 1D open channels. Thermal gravimetric analysis shows that complexes have good thermal stability and luminescence measuremet proves that the complex Eu(11) has fluorescent property.