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.

A diruthenium-substituted polyoxometalate as an electrocatalyst for oxygen generation.

Abstract: Transition metal heteropolyanions have been used to catalyze a variety of organic oxidations but have not previously been used for O2 generation, despite sharing some structural similarities with dioxoruthenium water-oxidation catalysts. In this study, we report that the di-Ru-substituted polyoxometalate (POM) [Ru2Zn2(H2O)2(ZnW9O34)2]14- can be used to catalyze the electrochemical generation of O2. By comparing the behavior of this compound to that observed using a mono-Ru-substituted POM catalyst, we show that adjacent Ru sites are necessary to observe O2 generation. These observations suggest a reaction pathway involving two Ru-bound oxygen species combining to form O2 and are consistent with the accepted mechanism of electrochemical oxygen evolution. Finally, analysis of the observed electrode kinetics yields a Tafel slope of roughly 120 mV, which is similar to values reported previously for perovskite anodes.

Unprecedented Application of Flexible Bis(pyridyl-tetrazole) Ligands To Construct Helix/Loop Subunits To Modify Polyoxometalate Anions

Abstract: By introducing the unprecedented and flexible isomeric bis(pyridyl-tetrazole) ligands into a polyoxometalates (POMs) system, three POM-based compounds, {Ag2(4-bptzb)2(H2O)2[H2PMo12O40]2}·4-bptzb·5H2O (1), [Ag4(3-bptzb)2(PMoVMoVI11O40)]·2H2O (2), and Ag3(3-bptzb)2.5(H2O)2[H3P2W18O62] (3) [4-bptzb = 1,4-bis(5-(4-pyridyl)tetrazolyl)butane and 3-bptzb =1,4-bis(5-(3-pyridyl)tetrazolyl)butane], were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses. Compound 1 exhibits a dimeric structure constructed from two Keggin [PMo12O40]3– anions and a binuclear [Ag2(trans-4-bptzb)2]2+ subunit in which the trans-4-bptzb acts as a bidentate bridging ligand with one tetrazolyl group. In 2, the 3-bptzb acts as a tetradentate bridging ligand with the tetrazolyl and pyridyl groups linking AgI ions to generate a 3D metal–organic framework (MOF), which contains charming meso-helix chains. The Keggin anions acting as bidentate inorganic ligands reside in the dist...

Lanthanide-organic cation frameworks with zeolite gismondine topology and large cavities from intersected channels templated by polyoxometalate counterions.

Abstract: A family of organic−inorganic hybrid frameworks, {[Ln(H2O)4(pdc)]4} [XMo12O40]·2H2O (Ln = La, Ce, and Nd; X = Si and Ge; H2pdc = pyridine-2,6-dicarboxylate), have been prepared under hydrothermal conditions and characterized by single crystal X-ray diffraction analyses, elemental analyses, IR, and thermal gravimetric analyses. Single crystal X-ray diffraction reveals that all six compounds are isostructural, and each consists of a zeolite-like four-connected three-dimensional cationic framework {[Ln(H2O)4(pdc)]4}4+ and ball-shaped Keggin type [XMo12O40]4− as templates. Interesting channels exist in the cationic framework with the gismondine topology, and these channels intersect each other to form large cavities, which array in a zigzag fashion and are occupied by nanosized [XMo12O40]4− counterions. Moreover, these compounds display strong photoluminescent properties in the solid state at room temperature.

Aqueous Speciation Studies of Europium(III) Phosphotungstate

Abstract: The incorporation of lanthanide ions into polyoxometalates may be a unique approach to generate new luminescent, magnetic, and catalytic functional materials. To realize these new applications of lanthanide polyoxometalates, it is imperative to understand the solution speciation chemistry and its impact on solid-state materials. In this study we find that the aqueous speciation of europium(III) and the trivacant polyoxometalate, PW9O349-, is a function of pH, countercation, and stoichiometry. For example, at low pH, the lacunary (PW11O39)7- predominates and the 1:1 Eu(PW11O39)4-, 2, forms. As the pH is increased, the 1:2 complex, Eu(PW11O39)211- species, 3, and (NH4)22{(Eu2PW10O38)4(W3O8(H2O)2(OH)4}·44H2O, a Eu8 hydroxo/oxo cluster, 1, form. Countercations modulate this effect; large countercations, such as K+ and Cs+, promote the formation of species 3 and 1. Addition of Al(III) as a counterion results in low pH and formation of {Eu(H2O)3(α-2-P2W17O61)}2, 4, with Al(III) counterions bound to terminal W−O...

First Structurally Characterized Palladium(II)-Substituted Polyoxoanion: [Cs2Na(H2O)10Pd3(α-SbIIIW9O33)2]9-

Abstract: The palladium-substituted tungstoantimonate(III) [Cs2Na(H2O)10Pd3(α-SbW9O33)2]9- (1) has been synthesized and characterized by IR, elemental analysis, and electrochemistry. Single-crystal X-ray analysis was carried out on Cs3KNa5[Cs2Na(H2O)10Pd3(SbW9O33)2]·16.5H2O, which crystallizes in the monoclinic system, space group P21/m, with a = 13.3963(13) A, b = 19.5970(19) A, c = 18.1723(17) A, β = 100.416(2)°, and Z = 2. Polyanion 1 represents the first structurally characterized palladium(II)-substituted polyoxometalate. The title polyoxoanion consists of two (α-SbIIIW9O33) Keggin moieties linked via three Pd2+ ions leading to a sandwich-type structure. The palladium centers are equivalent, and they are coordinated in a square-planar fashion. The central belt of 1 contains also one sodium and two cesium ions which reduces the symmetry of the polyanion to C2v. Polyanion 1 was synthesized in good yield by reaction of Pd(CH3COO)2 with Na9[SbW9O33] in aqueous acidic medium (pH 4.8). A cyclic voltammetry study of ...