Syntheses, Structures And Properties Of Tungsten-oxygen Clusters

It has been widely recognized that polyoxometalates (POMs) exhibit a variety of structures and properties that make them useful in catalysis, sorption, material science and medicine, etc. As the applications of hydrothermal technique on the syntheses, various organic-inorganic hybrid materials of particular properties emerges constantly and much attention has been caused on the performances studies of various materials.Based on the mechanism, we have synthesized some non-classical metal-oxygen clusters based on tungsten-oxygen clusters by hydrothermal technique. On the bases of X-ray structural analyses, the compounds have been characterized by IR, XPS, UV spectra, XRD and thermal analyses.I. Discontinuous tungsten-oxygen clustersApplying in hydrothermal synthesis reactions, we synthesized eight discontinuous tungsten-oxygen clusters:Compound1contains a novel2-D supramolecular layer structure constructed from [Cu(Phen)2]+copper coordination complexes through Ï€%Ï€ interactions. The packing motif of the [Cu(bpy)2]+copper coordination complexes in compound2exhibits a supramolecular channel. Crystal structure analysis reveals that3is the first Keggin polyoxoanion supported cadmium coordination complex. Another unusual feature of3is that adjacent [(BW12O40)Cd(2,2’-bpy)2(H20)]3-units interact with each other into a novel dimmer through hydrogen bonds. Compound4contains Pseudo-Keggin polyoxoanions [HPW12O40]2-and novel metal-chloride-ligand coordination complexes [Cd2(Phen)4C12]2+. An unusual feature of compound5is that two different types of silver coordination complexes([Ag(2,2’-bpy)3]+octahedra (â… ) and [Ag(2,2’-bpy)2(H2O)]+octahedra (â…¡)) are successfully introduced to be combined with POMs into a hybrid compound. The POM in compound6is [P2W18O62]6-, which has a Wells-Dawson structure, in compound6two different types of silver TMCs ([Ag(2,2’-bpy)3]+octahedra (â… )å'Œ[Ag(1)(2,2’-bpy)2]+tetrahedra (â… ))are successfully introduced to be combined with Wells-Dawson POMs into a hybrid compound. There exist two types of silver TMCs in compound7, octahedra (â… )[Ag(2,2’-bpy)3]+TMC and tetrahedra (â… )[Ag(2,2’-bpy)2]+TMC.compound7is based on POMs, two different types of TMCs and dissociated organic ligands. compound8is based on POMs, two different types of TMCs and dissociated organic ligands. There are two crystallographically different [Ag(2,2’-bpy)2]+TMCs in compound8, both of which are supported by the [BW12O40]5-anion, forming a novel bi-supported TMC. X-ray single crystal analyses, IR, UV, XPS and XRD etc., have been performed on the compounds.â…¡. Extended tungsten-oxygen clustersApplying in hydrothermal synthesis reactions, we synthesized four2-D tungsten-oxygen clusters and two1-D tungsten-oxygen clusters:Crystal structure analyses reveal that9exhibit a novel2-D framework structure constructed from tungsten polyoxoanion, metal ions and4,4’-bpy units. The compound10,11and12are isomorphous. There are two main differences among them. The first difference of the three is the central atom of the Keggin ions:it is B atom for compound10, and Si atom for compound11and12. The second difference of the three is the monodentate ligand coordinating to the Ni ions:it is water molecule for compound10, chloride ion for compound11and bromide ion for compound12. The compound13and14are isomorphous. The difference for compound13and14is the transition metal centre of the frameworks. In addition, the compound13and14are the first examples of compounds containing both Keggin ion and Pseudo-Keggin ion. X-ray single crystal analyses, IR, UV, XPS, TG and XRD etc., have been performed on the compounds. â…¢. Metal-substituted tungsten-oxygen clustersApplying in hydrothermal synthesis reactions, we synthesized three mono-substituted tungsten-oxygen clusters:in contrast to the classic mono-substituted [PW11NiO39]5-ion, an unusual feature of15is the novel octahedral coordination environment of the substituted Ni centre in the ion [PWnNiO39]5-of15, which is completed by not only five oxygen atoms from the vacant site but also a nitrogen atom from a4,4’-bpy ligand. The packing motif of the [Cu(bpy)2]+copper coordination complexes in compound16exhibits square supramolecular channels running along the a axis, which are then filled by the [PW11CuO39]5-ions. compound17contains a number of C-H…O hydrogen bonding interactions, which link POMs and TMCs into a supramolecular structure. X-ray single crystal analyses, IR, UV, XPS, TG and XRD etc., have been performed on the compounds.