Synthesis And Properties Of Metal-organic Frameworks Based On Five-membered Heterocyclic Bridging Ligands And Fluorescein Ligands

The chemistry of organic-inorganic coordination polymers and supramolecular complexes 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, and catalytic materials. In this thesis, a series of bent ligands bridging by the 1, 3, 4-oxadiazole, 1, 2, 4-triazole and fluorescein ligands were synthesized. The coordination chemistry based on these new ligands and metal ions was investigated. Totally 48 new coordination 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, electron spin resonance spectroscopy, non-linear optical property and thermal stability were investigated.I. Coordination supramolecule assembly Cd(L6)2 generated from the 1, 2, 4-triazole bridged ligands and d-block metals Cadmium (II) center has been synthesized. It can retain single crystallinity up to 300℃. More interesting, it can effectively recognize and separate C6-C8 methyl- or halide-substituted aromatics, which is demonstrated by X-ray single crystal analysis and 1H NMR spectra. Additionally, the different aromatic-Cd(L6)2 host-guest systems exhibit guest-dependent luminescent properties. This research developed tunable emissions by controlling the type of guest moieties.II. A series of reactive group functionalized aromatics can be absorbed and completely separated by porous framework in both vapor- and liquid-phases under mild conditions by Cd(L6)2 framework. All adsorption and separation experiments are directly performed on the single crystals of Cd(L6)2. This research developed application of metal-organic frameworks as molecular separation materials. In addition, the Cd(L6)2 framework can be a shield to protect the active functional groups substituted guests from reaction with the outside medium containing their reaction partners. More interestingly, these reactive group-substituted aromatics readily transform to the corresponding radicals within Cd(L6)2 host upon ambient light or UV light (355 nm) irradiation. Furthermore, the generated organic radicals are alive for a month within the interior cavity in air under ambient conditions. Simple organic radicals are highly reactive short-lived species, and they can not be isolated and conserved under ambient conditions. So Cd(L6)2 host herein could be considered as a radical generator and storage vessel.III. Single crystallinity of Coordination supramolecule assembly Cd(L6)2 can effectively recognize and separate Chloroform, Dichloromethane and Carbon tetrachloride, which is demonstrated by X-ray single crystal analysis and 1H NMR spectra. IV. The high iodine enrichment based on Coordination supramolecule assembly Cd(L6)2 in both liquid- and vapor-phases, and also their guest-driven tunable luminescent property. The iodine-driven emission spectra herein might be a useful tool to monitor the encapsulated iodine-species content during the enrichment process.V. Three coordination polymers with one-dimensional helical structure have been successfully prepared by the reaction of 1, 3, 4-oxadiazole bridged ligand with Hg(II) halides. Moreover, these three new complexes exhibit interesting anion-dependent NLO and luminescent properties.VI. 16 coordination compounds generated from the 1, 3, 4-oxadiazole and 1, 2, 4-triazole bridging ligands and d-block metals have been synthesized. The results demonstrated that the length and bend angle of the ligands, anion and solvent significantly influenced the structures of the resulted compounds. VII. Coordination chemistry of fluorescein ligands was investigated, two Cd(II) coordination compounds were obtained under different conditions. Two coordination compounds based on 1, 2, 4-triazole-bridged ligands and lanthanide metals were synthesized, and the luminescent properties were investigated.This study demonstrated that the use of bent ligands bridged by 1, 3, 4-oxadiazole, 1, 2, 4-triazole and fluorescein ligands as precursors to bind transition metals and lanthanide metals, is in fact an efficient approach for syntheses of novel supramolecular systems with interesting chemical and physical properties.