Study On The Synthesis, Structure And Property Of Metal-Organic Coordination Polymers Based On Polyoxovanadates

Through selecting the transition metal cations as templating andmultidentate organic ligands and polyoxometalates(POMs) as building blocks,inorganic-organic hybrid material was synthesized based on the principles ofmolecular design and crystal engineering. Polyoxovanadate has become a veryimportant inorganic building block ascribing to their structural diversity. It isreceiving increasing attention for their interesting properties.Two novel organic-inorganic hybrid compounds were hydrothermal--ly synthesized in this research. The reaction of NiCl₂·6H₂O, bpp, andNH₄VO₃ yields compound [Ni₃(bpp)₄(H₂O)₄V₆O₁₈]·2H₂O (â… ); the reaction ofNH₄VO₃, CuSO₄·5H₂O and 1,3-bis(4-pyridyl)propane(bpp) yields compound[Cu(bpp)(H₂O)V₂O₆]2·H₂O (â…¡)X-ray single crystal structure determination reveals that: compoundâ… isa three-dimensional covalent structure. Its single crystal structure belong to monoclinic crystal system, space group P2₁/n with the crystal dataα=13.061(3) (?), b=16.385(3) (?), c=15.426(3) (?),β=102.25(?)V=5960.2(17) (?)³,Z=8. The structure of compoundâ… is constructed from three componentsubstructures: two-dimensional {Ni(bpp)₂}_n²ⁿ⁺ networks, one-dimensional{Ni(bpp)(H₂O)₂}_n²ⁿ⁺ chains and vanadate sprials. Each vanadate chain linkstwo adjacent networks, while vanadate and {Ni(bpp)(H₂O)₂}_n²ⁿ⁺ interlink toform a three-dimensional framework; Compoundâ…¡is a three-dimensionalcovalent structure. Crystal data for compoundâ…¡: Tetragonal crystal system,space groupâ… -42d,α=b=15.062(2) (?), c=32.935(7) (?), V=7471(2) (?)³, Z=8.It consists of two component substructures: {Cu(bpp)}_n²ⁿ⁺ helical chains and{V₂O₆}_n^2n- vanadate helical chains. {Cu(bpp)}_n²ⁿ⁺ helical chains down the aaxis are connected by vanadate helical chains down the a axis and b axis toform a three-dimensional covalent framework. Besides, {Cu(bpp)}_n²ⁿ⁺helical chains down the b axis would thread left and rightthrough{Cu(bpp)}_n²ⁿ⁺ helical chains down the a axis. Every three{Cu(bpp)}_n²ⁿ⁺ helical chains are interconnected by two vanadate tetrahedraleach other to form the triple helical chains.From UV-Vis-NIR reflectance spectra, it's found that compoundâ… ,â…¡have optical energy gap of 2.7eV and 2.6eV, respectively, and both belong tosemiconductor.To the purpose of synethesising controlablely inorganic-organic hybridmaterial based on polyoxovanadate, the reaction conditions that influence structure of compoundâ… were discussed through comparing with other threesimilar compounds.