Synthesis And Properties Of Metal-Organic Frameworks Based On β-Diketone Ligands And Five-Membered Heterocycle Bridging Ligands

The organic-inorganic supramolecular chemistry driven by coordination interaction has recently become an active area of increasing interest internationally. The study of coordination-driven self-assembled discrete and polymeric metal-organic frameworks (MOFs) is a very active interdisciplinary research area. These metal-organic assemblies have intriguing structures and potential applications as smart optoelectronic, magnetic, catalytic materials, selective molecular adsorption and separation. In this thesis, a series ofβ-diketone ligands and the bent ligands bridging by 1, 3, 4-oxadiazole, 1, 2, 4-triazole were synthesized. The coordination chemistry based on these new ligands and metal ions was investigated. Totally 40 new coordinated compounds were prepared and fully characterized by IR, elemental analysis, X-ray single-crystal diffraction and powdered X-ray diffraction. The luminescent properties, molecular adsorption and separation, reversible solid-state anion exchange and thermal stability were investigated.I. 2D-Net Cu(L1)(CH3OH) and 3D-NbO MOF [Cu3(L1)6]?7H2O have been prepared by the combination ofβ-diketone ligand L1 and Cu(II) cation under different pH conditions, respectively. [Cu3(L1)6]?7H2O displays the function of molecular sieve. It can effectively desorb and re-adsorb of water molecules in a single-crystal-to-single-crystal fashion.II. The coordination chemistry based on longerβ-diketone ligand L3 and Zn(II) center in different aromatic templates was investigated. A series of 2D-Net and 3D-NbO MOFs were generated. The results demonstrated that the size and substituted groups of these aromatic solvent molecules are key factors in affecting the structures of the supramolecular aggregates. (1) Small aromatic molecules (< C8 arenes) as the solvent contributes to 2D-Net complexes while large aromatic molecules (> C8 arene) contributes to 3D-NbO-MOFs. (2) Fluorobenzene, chlorobenzene as solvent facilitates 2D-Net complexes while bromobenzene, iodobenzene and m-bromotoluene facilitate 3D-NbO-MOFs. (3) CN, OH and NH2-substituted aromatic molecules (< C8 arenes) as the solvent contribute to 2D-Net complexes, such as benzonitrile, m-toluidine, o-cresol and m-cresol. (4) C9-aromatic solvent molecules (such as 1, 3, 5-triethylbenzene, nitrobenzene and acetophenone) favor 3D-NbO-MOFs. These patterns provide us an efficient approach in the construction of novel topology structures of MOFs by the templating effect of solvent, and potential application in the adsorption and separation of organic homologues and isomers.III. Three Cu(II)-bimetallic macrocycles based on 1, 3, 4-oxadiazole bridging double Schiff-base ligands were synthesized. Cu2(L4)2-macrocycle is a highly selective host cage capable of discerning between pyrazine and its different methyl-substituted derivatives based on reversible intracage metal-ligand binding. Additiontly, Cu2(L4)2-macrocycle exhibits guest-dependent"breathing"behavior in reversible adsorption and desolvation. Such materials may find applications in the fields of recognition and separation, sensors, and purification of aromatics.IV. Some nanotube-like mixed-metal polymers based on metal-containing ligand Cu2(L4)2 in two-step method were synthesized. This study demonstrated that the metal-containing ligand Cu2(L4)2 with uncoordinated donors is a versatile connector in the construction of mixed-metal polymers. And this research developed an efficient approach for synthesis of novel nanotube-like mixed-metal hybrid materials.V. Six Ag(I)-MOFs with nanoscale channels based on 1, 2, 4-triazole heterocycle bridging ligand L15 were synthesized. Reversible solid-state anion exchange between ClO4-,BF4- anions and SO3CF3- anions was investigated primarily. Interestingly, the luminescent intensity of Ag(I)-MOFs can be tuned on the basis of the solid-state anion exchange, which might provide an alternative approach to tuning the luminescence.VI. Eleven coordination compounds generated from the 1, 3, 4-oxadiazole and 1, 2, 4-triazole heterocycle bridging ligands and d-block metals have been synthesized. The results demonstrated that the ligand isomerism and the templating effect of anions significantly influenced the structures of the resulted compounds.VII. Two unusual Cu6 and Cu8 core complexes were prepared by one-pot solution and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. VIII. Twelve new crown ether-containing ligands and twelve 1, 3, 4-oxadiazole and 1, 2, 4-triazole heterocycle bridging ligands were designed and synthesized.This study demonstrated that the use ofβ-diketone ligands and the bent ligands bridged by 1, 3, 4-oxadiazole and 1, 2, 4-triazole as precursors to bind transition metals, is in fact an efficient approach for synthesis of novel supramolecular systems with interesting chemical and physical properties.