Syntheses, Structures And Properties Of Coordination Polymers Based On Aromatic Pyridyl-triazole Ligands

Nowadays metal-organic frameworks(MOFs) have been an important subject because of their intriguing topological architectures and their potential applications in gas storage, chiral separation, optical materials, catalysis, ion exchange, fluorescence and so on. The self-assembly of metal-organic coordination polymers can be accomplished based on the designability of organic ligands, and it is important to design and synthesize new materials with specific functions.According to the principles of crystal-engineering, we have adopted two ligands: 3-(5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl) benzoic acid(HL1) and 4-(5-(1H-pyrazol-4-yl)-1H-1,2,4-triazol-3-yl) pyridine(H2L2), and six MOFs with new topological structures have been synthesized hydro(solvo)thermally in this paper, and they have been characterized by single-crystal X-ray diffraction, infrared spectrometry(IR), elemental analysis(EA), powder X-ray diffraction(PXRD) and thermogravimetric analysis(TGA), and so on. The main contents in the thesis are summarized as follows:In the first chapter, the basic concept, research background and progress, synthetic methods and influencing factors of MOFs and their applications and significance have been introduced.In the second chapter, a novel flexible achiral ligand, 3-(5-(pyridine-4-yl)-4H-1,2,4-triazol-3-yl) benzoic acid(HL1), was synthesized according to the literature method. Using HL1 ligand, four metal(II)-complexes formulated as Zn L12·2H2O(1), Cd L12(H2O)2·8H2O(2) and ML12(H2O)·H2O(M = Co 3 and Ni 4) have been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Complexes 1, 3 and 4 all feature a uninodal 2D layer with a 44-sql topology, and two such(4,4) nets interpenetrate in a parallel manner. Complex 2 exhibits a similar 44-sql topology, but no interpenetration is observed in complex 2. Among the four complexes, only complex 1 is a homochiral network, which is evidenced by the CD spectrum. In complex 1, packing of the 2D layers generates a 41 screw axis along the c direction, and two-fold axes along the a and b directions, respectively. In complex 2, the Zn(II) center lies about an inversion center, giving rise to the centrosymmetric structure of complex 2. In complexes 3 and 4, packing of the 2D units generates a 21 screw axis along the c direction in the two complexes, and an inversion center is found between two neighboring 2-fold interpenetrated layers. The work indicates that the chirality of the space group for the homochiral complex 1 comes from the supramolecular packing of the 2D layers.In the third chapter, a N-donating ligand, 4-(5-(1H-pyrazol-4-yl)-1H-1,2,4-triazol-3-yl) pyridine(H2L2), was prepared according to the literature method. Using H2L2 ligand, an acid-stable Zn(II) complex formulated as Zn2(HL2)2(SO4)·H2O(5) and an acid-unstable complex formulated as Zn2L22·12H2O(6) were hydro(solvo)thermally synthesized and structurally characterized by single crystal X-ray diffraction. Complex 5 features a uninodal 6-connected 2-fold interpenetrating three-dimensional(3D) dense architecture with {412·63}-pcu topology, and complex 6 exhibits a 2-nodal(3,6)-connected 3D open architecture with(4·62)2(42·610·83)-rtl topology. The results indicate that the stability of complex 5 in sulfuric acid is probably associated with the coordinated SO42- in the quite dense structure, and complex 5 can also be synthesized via electrodeposition in sulfuric acid; it can improve the discharging characteristics of the zinc-lead dioxide battery at room temperature.