Polyoxometalate

About: Polyoxometalate is a research topic. Over the lifetime, 3493 publications have been published within this topic receiving 94123 citations. The topic is also known as: POM.

Polyoxometalate-Based Metal-Organic Frameworks as Visible-Light-Induced Photocatalysts.

Abstract: Two stable 3D polyoxometalate-based metal–organic frameworks (PMOFs), [CuI12(trz)8(H2O)2][α-SiW12O40]·2H2O (1) and [CuI12(trz)8Cl][α-PW12O40] (2) (Htrz = 1-H-1,2,4-triazole) based on Keggin-type POMs were successfully obtained and fully characterized. The basic building units of the two PMOFs are [CuI12(trz)8], but polyoxoanion (POA) template effect leads to different structures and properties: 1 represents an interesting example that [α-SiW12O40]4– locate in the nine-membered Cu-trz rings through Cu···O weak interactions to form a 3D framework, whereas 2 shows a 3D structure constructed from 2D bilayer cationic network [CuI12(trz)8Cl]3+ and [α-PW12O40]3– lying in the adjacent layers via Cu···O weak interactions. PMOF 1 as unusual visible-light photocatalyst exhibit significantly enhanced photocatalytic activity under visible-light and excellent stability during the photocatalysis process for recovering and recycling, as well as photocatalytic hydrogen evolution activity.

Nanocomposite Multilayer Film of a Ruthenium Metallodendrimer and a Dawson-Type Polyoxometalate as a Bifunctional Electrocatalyst

Abstract: A pentaerythiritol-based metallodendrimer with four ruthenium(II) terpyridine units (RuDen) and a Dawson-type phosphotungstate, P2W18O626- (P2W18) are immobilized on a glassy carbon electrode to form multilayered self-assemblies by layer-by-layer deposition based on electrostatic interaction. The (P2W18|RuDen) multilayer films have been investigated with UV−visible spectrometry, cyclic voltammetry, and TappingMode atomic force microscopy. They showed a bifunctional electrocatalytic capability, namely, iodate reduction and arsenite oxidation.

Polyoxometalate, Cationic Cluster, and γ-Cyclodextrin: From Primary Interactions to Supramolecular Hybrid Materials

Abstract: Herein, we report on a three-component supramolecular hybrid system built from specific recognition processes involving a Dawson-type polyoxometalate (POM), [P2W18O62]6-, a cationic electron-rich cluster [Ta6Br12(H2O)6]2+, and γ-cyclodextrin (γ-CD). Such materials have been investigated using a bottom-up approach by studying the specific interactions between γ-CD and both types of inorganic units. Their ability to interact has been investigated in the solid state by single-crystal X-ray diffraction (XRD) and in solution using multinuclear NMR methods (including DOSY, EXSY, and COSY), electrospray ionization mass and UV-vis spectroscopies, electrochemistry, and isothermal titration calorimetry experiments. Single-crystal XRD analysis reveals that POM:γ-CD constitutes a highly versatile system which gives aggregates with 1:1, 1:2, and 1:3 stoichiometry. Surprisingly, these arrangements exhibit a common feature wherein the γ-CD moiety interacts with the Dawson-type POMs through its primary face. We present also the first structural model involving an octahedral-type metallic cluster with γ-CD. XRD study reveals that the cationic [Ta6Br12(H2O)6]2+ ion is closely embedded within two γ-CD units to give a supramolecular ditopic cation, suitable to be used as a linker within extended structure. Solution study demonstrates clearly that pre-associations exist in solution, for which binding constants and thermodynamic parameters have been determined, giving preliminary arguments about the chaotropic nature of the inorganic ions. Finally, both building blocks, i.e., the ditopic supramolecular cation {[Ta6Br12(H2O)6]@2CD}2+ and the Dawson-type anion, react together to give a three-component, well-ordered hybrid material derived either as a supramolecular hydrogel or single crystals. The solid-state structure shows an unprecedented helicoidal tubular chain resulting from the periodic alternation of POM and supramolecular cation, featuring short hydrogen-bonding contacts between the electron-poor POM and electron-rich cluster. The 1D tubular ionic polymer observed in the single crystals should make it possible to understand the long-range ordering observed within the hydrogel hybrid material. The supramolecular chemical complementarities between the γ-CD-based ditopic cation and POM open a wide scope for the design of hybrid materials that accumulate synergistic functionalities.

Colloidal organization and clusters: self-assembly of polyoxometalate-surfactant complexes towards three-dimensional organized structures.

Abstract: Increased hydrophobicity of well-defined polyoxometalate clusters is possible through complexation with cationic surfactants in a one-pot reaction. The clusters, of toroid and spherical shape and colloidal dimensions, then organized into ordered, supramolecular assemblies, as shown schematically, are similar to classical liquid crystals. The increased solubility in organic media opens the door to new polyoxometalate-polymer hybrid materials.