Synthesis, Structure And Characterization Of Coordination Polymer Bridging By Ligand Of Carboxylato And Nitrogen-containing Heterocycle

Metal-organic frameworks (MOFs) is self-assembled coordination polymer of metal ions with multidentate organic ligands. MOFs have attracted much attention owing to their intriguing molecular topologies and potential applications as functional materials, such as gas absorption, molecular magnetism, catalysis, ion exchange and nonlinear optics. Now, many research works are focused on design and synthesis of novel ligands to construct supramolecular architectures. There are two aspects about our research work as follow:One aspect is about selection, design and synthesis of organic ligands. Tetrachloroterephthalate acid is selected as a key ligand due to its rigid aromatic multi-carboxylic structure. 1,1′-(1,4-Butanediyl) bis-imidazole (bbi) was chosen as a flexible ligands, synthesized through reaction of imidazole with 1,4-dibromobutane in the yield of 45.15%. p-Bromopyridine hydrochloride was prepared through oxidation, nitration, bromination, reduction, and acidification reaction from pyridine as the starting material. Benzene-1,3-dicarboxylic-5-boronic triacid was obtained through Grignard reaction and oxidation reaction of 1,3-dimethyl-5-bromobenzene. The ligand, 4-(4-pyridinyl)-3,5-benzenedicarboxylic acid, was achieved by Suzuki coupling reaction of 1,3-dimethyl-5-bromobenzene with p-bromopyridine hydrochloride with the yield of 24.91%.Another aspect is about synthesis, structure and properties of coordination polymer: With 2,3,5,6-tetrachloro-1,4-benzenedicarboxylic acid or bimb as ligand, [Ni(C₈Cl₄O₄)(C₅H₅N)₃ (H₂O)]·2C₅H₅N 1 and [Co(C₈Cl₄O₄)(C₅H₅N)₃(H₂O)]·2C₅H₅N 2 were gained by diffusion method. [Cu(C₈Cl₄O₄)(bbi)₄]·3H₂O 3 were also gained by evaporation method. Their structure and property were investgated by IR, elemental analysis, thermogravimetric analysis and X-ray diffraction. The result shows that both complex 1 and 2 show the same 1D chains. Complex 3 adopts a 3-D supramolecular structure, with the unprecedented topology of 44611 net.