Syntheses And Properties Of Polyoxometalates Modified By Metal/imidazole Derivative Ligands

To investigate the factors of synthetic conditions for inorganic-organic hybrid compounds and broaden the scope of existing knowledge, novel hybrids based on different POMs have been obtained in this thesis, which are modified by transition metals(Cu2+/Cu+, Ag+, Co2+, etc) and imidazole ligands, respectively. Further, some properties of the hybrids have been studied, and the relationships between properties and structures for the hybrids have been also analyzed.In this thesis, twenty-four inorganic-organic hybrid compounds have been obtained by hydrothermal technique. The compounds have been characterized by IR, TG, single crystal X-ray diffractions, PXRD, XPS, etc. The electrochemical properties, photoactivity and luminescent properties for some compounds have been studied.1. Keggin POM modified by metal/imidazole derivative ligands.Compounds 1-4 have been synthesized in Ag/bim and Cu/bim reaction system by introducing different polyoxoanions such as [PW12O40]3-, [GeW12O40]4- and [BW12O40]5-. Compound 5 has been synthesized by altering pH. Compounds 6-14 have been obtained with the similar method by introducing different metal ions and [PMo12O40]3-, or by altering the functional of ligands. When we adopt bimb as imidazole derivative ligand, we get compound 6, which hasthe structure of layer with four fold interdigitated. When adjusting the ligand to itmb, compounds 7-14 were obtained. Compounds 7-11 have the similar structures. A structural feature in compounds 7-11 is that there exists a 1D + 1D â†' 3D interdigitated architecture achieved by molecular zippers, in which overhanging mono-coordinated ligand arms act as teeth. A 2D layer is constructed by Ag complexes and polyoxoanions in compounds 12. A rare 2D + 0D structure is constructed by Ag complexes and polyoxoanions in compounds 13. The 3D framework of compound 14 is constructed from Ag complexes and polyoxoanions.2. Wells-Dawson POM modified by metal/imidazole derivative ligands.Adopting Ag/bim as the reaction system by introducing [P2W18O62]6-, we obtain compound 15 with dinuclear silver cluster {Ag2}. When introducing the second ligand im, we get compound 16 which existing infinite silver chain {Ag∞}. Adjusting the ligand to itmb, we get compound 17. When Ag ion is replaced by Cu ion, compound 18 is obtained, which displays a 1D chain.3. Isopolymolybdate modified by metal/imidazole ligands.Two POM-based hybrids have been synthesized in Cu/bimb reaction system by altering the existing form of molybdenum. Compound 19 shows supramolecular framework, while compound 20 contains the imidazole derivative ligand functionlized octamolybdate polyanion. When altering the ligand, compound 21 shows complicated 3D framework coexisting of both meso-helixes and left/right- helixes. When adopting Co as raw materials, compound 22 constructed by complexes and isopolymolybdate chains is obtained, which shows a 2D layer.4. Molybdenum sulfur cluster modified by metal/imidazole ligands.Taking Waugh type polyoxometalates as raw materials, we selecte bimb as organic ligand to synthesize compounds 23 and 24. There is a new type of inorganic compound building blocks of molybdenum sulfur cluster Mo17S8 in compound 23. Compound 24 is the first molybdenum sulfur cluster with sulfur as center heteroatom and tetracapped vanadium subunits structure.5. The electrocatalytic, photocatalytic and luminescent properties for compounds have been investigated. With the synergistic catalytic effect between the polyoxoanions and metals, compounds 15 and 16 show high activity for photocatalytic degradation of RhB. The compounds 15, 16, 21 and 22 possess solid-state emission spectra, therefore they may be good candidates for potential solid-state luminescent materials. The electrochemical properties of compound 10 show bifunctional electrocatalytic activities toward not only reduction of iodated, but also oxidation of ascorbic acid.