Synthesis And Characterization Of A Few New Hybrid POMs Characterization

The polyoxometalates (POMs) have the rich composition and diversity of structure, endowing them a potential application in magnetism, catalysis, medicine, environmental protection and materials science. The discovery and synthesis of novel POMs with unique property have been the driving force for the development of POM chemistry. In this paper, we synthesize five new heteropolyoxometalates, especially with V and Se as certral heteroatoms, all of which have been characterized by IR, elemental analysis, X-ray single crystal diffraction and high resolution electrospray mass spectrometry, part of compounds were characterized by TG, fluorescence spectrum, UV-vis spectra and magnetic measurement.1. Two novel inorganic-organic hybrids based on Na(N(C2H4OH)3)n+bridging units and Keggin polyoxometalates with V5+as central heteroatom have been synthesized:NaH2[N(C2H4OH)3]4[VW12O40]·4H2O (1)Na[N(C2H5OH)3]8H5(VMo12O40)2·6H2O (2)In compound (1), Keggin ion [VW12O40]3-as a bidentate ligand using its two terminal oxygens coordinates to Na(N(C2H4OH)3)n+bridging units to form a one-dimension chain with21symmetry, and the coordination octahedral configuration of the Na+ion was accomplished by four oxygens of the two bidentate bib molecules and two terminal oxygens of two [VW12O40]3-polyanions. In compound (2), the Na(N(C2H4OH)3)4+ion as a bridging unit connects two Keggin [VMo12O40]3-to form a dimer, and the coordination octahedral configuration of the Na+ion was accomplished by four oxygens of the four monodentate bib molecules and two terminal oxygens of two [VM012O40]3-polyanions. The electrochemical experiment shows that both of compounds exhibit good electroacatalytic activity towards the reduction of nitrite, chlorate and bromate.2. By conventional solution method, a pure inorganic two-dimensional framework based on sandwich tungstoselenite was synthesised:Na7H[Cu3(H20)Na2(H2O)3(SeW9O33)2]·15H2O (3)Unique characteristic of3is that two of the three Cu atoms in central belt have not coordinated water molecules, instead coordinated by terminal oxygens of neighbouring polyanion by Cu-O-W bonds to lead to a two-dimensional structure. The lattice of3can be described as double polyanion layers, the polyanions in one layer are arranged vertically, whereas the polyanions in the other layer are arranged horizontally, and all polyanions in the "vertical layer" are completely offset with respect to those in the "horizontal layer". Magnetic measurements comfirmed that the interaction among Cu2+ions in compound3is antiferromagnetic.3. At ambient temperature, a Dowson-like tungstoselenite was isolated in aqueous solution with diethylamine as counter cation:(C4H12N)6[H2SeW18060](4)The polyanion consists of two equivalent trivacant SeW9O33half units, derived from the pseudomorphic Keggin type (SeW12O40) structure by removal of an edge-shared W3O13moiety. The whole molecule has approximate D3d symmetry and one Se atom disordered between two possible sites with50%occupancy and the distant of Se…Se of2.638A. The high-resolution ESI-MS confirmed the existence of HbSeW18O605-, H2SeW18O594-, H3SeW18O593-and H6SeW18O602-in gas-phase fragmentation.4. A new two-dimensional inorganic-organic hybrids based on wavelike{Cu1-bib}n polymer chains bridged by tetradentate [SiW12O40]4-polyanions was synthesized under hydrothermal condition:Cu4(C12H10N2)4SiW12O40·2H2O (5)In compound5, the bib ligand acts as a bidentate ligand to Cu1ions to form wave like {Cu-bib}n polymer chains, which are further connected by terminal/bridging O atoms from the quadridentate [SiW12O40]4-polyanions to a two-dimensional (2D)(3,4)-binodal layer with a Schlafli symbol of (83)-(62-84).