Study Of Polyoxometalate-based Host-guest Hybrid Compounds

The object of this thesis is the design and synthesis of new polyoxometalate-based inorganic-organic host-guest hybrid compounds, in which three types of polyoxometalates like Anderson, Keggin, Polyoxomolybdate were used as inorganic templates, N-donor ligands and transition-metal ions were employed to construct organic-metal host frameworks. The study on synthetic conditions owing to different polyoxometalates and the analysis of relationships between structures and properties were also performed.Five polyoxometalate-based host-guest hybrid compounds have been obtained on the basis of low temperature co-solvothermal synthesis method and hydrothermal technique, using pre-design organic molecular as ligands, which have been characterized by elemental analysis, IR spectroscopy, UV spectroscopy, TG analysis and single crystal X-ray diffraction. The magnetic property and photocatalytic property of partial compounds have also been investigated.Compounds H[(bitdc)2Ni2(H2O)6][IMo6O24]·6H2O(1) and H[(bitdc)Cu (H2O)3]2[IMo6O24][DMF](2) were synthesized by low temperature co-solvothermal strategy. Both of them are constructed based on Anderson-type{IMo6O24} anions. And the bridging bis(pyridyl) ligand N,N’-bis(isonicotinoyl)-trans-1,2-diaminocyclohexane (bitdc) and transition-metal ions were used as original materials to achieve metal-organic subunits in the structures of1and2. Compound1represents the first example of Anderson-anion-templated host-guest species with3D supramolecular framework, the structure of compound2is a1D supramolecular chain. Experiments show that1not only has anti-ferromagnetism property, but also shows good photocatalytic activity for the degradation of RhB.Compounds [(H2O)4(bitdc)Ni]2[SiW12O40]·2H2O (3) and [(H2O)3(bitdc)2Ni][H2SiW12O40]·3H2O(4) were prepared under hydrothermal conditions, both of them are constructed based on Keggin-type{SiW12O40} anions. By adjusting pH of reaction mixtures, we obtained two different compounds3and4. In the structure of3, organic ligands bitdc coordinated with Ni2+ions to form square host framework, but in the compound4, organic ligands bitdc were distorted when they coordinated with Ni+ions, resulting in the shape of host framework looking like windmill. Compound3shows2D supramolecular layer architecture, whereas complex4shows3D supramolecular network. The studies show that both3and4possess anti-ferromagnetism properties, and complex4shows a certain photocatalytic activity for the degradation of RhB. Compound [{Cu2(triazolate)2(H2O)2}Mo4O13](5) was hydrothermally synthesized on basis of in situ fabrication. It is a3D host-guest architecture based on molybdate oxide chains. In the structure of compound5, the organic moiety adopts the anionic triazolate form in a three connect ligation mode. As guest, molybdate oxide chain is constructed from edge-and peak-sharing molybdenum octahedra and hexahedra. Experiments show that compound5has ferromagnetic property, and it also can embarrass the degradation of RhB.