Syntheses, Structures And Performances Of Polyoxometalates

Polyoxometalates（POMs） form a distinctive class of inorganic metal-oxygen cluster compounds which is unique in its topological and electronic versatility and useful in fields as diverse as catalysis, analysis, biochemistry, materials science and medicine. 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. In this field, an important advance is to decorate well-known polyoxoanions with various organic and/or transition metal complex moieties and then to link them up into supramolecular, supported and extended solid materials in appropriate ways.Based on this mechanism, we synthesized some non-classical metal-oxygen clusters of containing carboxylic acids, based on tungsten and molybdenum oxygen clusters. On the bases of X-ray structural analyses, all the compounds have been characterized by IR, UV-Vis, XRD, cyclic voltammetric measurements and photodegradation properties. In terms of synthesis, the main research is the complexing of carboxylic acid ligands with the metal ions, and the change of coordination pattern of carboxylic acid ligands which influence the structure of the compounds.â… .Polyoxometalate constructed by Cu and 2- pyridine carboxylic acidApplying in hydrothermal synthesis reactions, we synthesized six new organicinorganic hybrid compounds containing deprotonated picolinic acid as a ligand. And these six compounds have been characterized by IR, UV-Vis, XRD, cyclic voltammetric measurements. Single crystal X-ray analysis reveals that compounds 1-3are isomorphous and isostructural, in which each is based on [H₂XM₁₂O₄0]^2- and[Cu（Hpic）2]2+. Compounds 4 and 5 are also isomorphous and isostructural, of which the structures are more interesting and complex than those of compounds 1-3. Both structures are constructed from [XM12O40]4- and transition metal mixed-organic-ligand complexes [Cu（Phen）（H2O）]2[Cu（pic）2]4-. Compound 6 is also constructed from Keggin ions [Ge W₁₂O₄0]^4- and transition metal mixed-organic-ligand complexes[Cu3（phen）2（pic）2（H2O）2]4+, which is, however, thoroughly different from those of compounds 4 and 5. The photodegradation properties of compounds 1-6 have been analyzed. Compounds 1-3 also exhibit rapid absorption properties for Rh B（Rhodamine B）. Detailed analysis of photodegradation properties of compounds 1-5reveals that the molybdate POM has stronger degradation ability for Rh B than the tungstate one.â…¡.Polyoxometalate containing isonicotinic acid or nicotinic acidApplying in hydrothermal synthesis reactions, we synthesized five new organicinorganic hybrid compounds containing nicotinic acid or isonicotinic acid as a ligand.And these five compounds have been synthesized and characterized by IR, UV-Vis,XRD, cyclic voltammetric measurements and single crystal x-ray diffraction analysis.Crystal analysis reveals that compound 7 exhibits a 2-D double layered framework structure constructed from [Ge W₁₂O₄0]^4- and copper-aqua-2,2′-bpy-hydroxylisonicotinate complexes. Compound 8 is a supramolecular structure constructed from polyoxoanions and transition metal mixed-organic-ligand complexes. Compound 9 is a novel polyoxoanion bi-supported transition metal mixed-organic-ligand complex.Compound 10 is a 1-D chain structure constructed from polyoxoanions and transition metal mixed-organic-ligand complexes. Most interestingly, compound 11 is based on the Dawson POM [H3As2W18O62]3-, exhibiting a novel structure in which the Dawson POM supports two different TMMCs. The photodegradation properties of compounds7-11 have been analyzed.â…¢. By Cd or Co and containing carboxylic ligands to construct polyoxometalateApplying in hydrothermal synthesis reactions, we synthesized five new organicinorganic hybrid compounds, based on different polyoxoanions and transition metal mixed-organic-ligand complexes（TMMCs） which contain Co2+ or Cd2+ coordinating with nicotinic acid or isonicotinic acid. And these five compounds have been synthesized and characterized by IR, UV-Vis, XRD, cyclic voltammetric measurements and single crystal x-ray diffraction analysis. Single crystal X-ray analysis reveals that compounds 12-14 are isostructural and isomorphous with one another, of which compounds 12 and 13 are constructed from Keggin POMs and TMMCs of inic ligands, but interestingly, compound 14 is formed by Keggin POMs and TMMCs of nic ligands. Compound 15 is constructed from Keggin POMs and supported cadmium-nic-phen complexes, forming a novel POM bi-supported TMMC.Compound 16 is based on Keggin POMs and cobalt mixed-organic-ligand complexes,in which 2-hydroxyl-inic is in-situ synthesized from inic hydrothermally. The photodegradation properties of compounds 1-5 have been analyzed.