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.

Novel isopolyoxotungstate [H2W11O38]8- based metal organic framework: as Lewis acid catalyst for cyanosilylation of aromatic aldehydes.

Abstract: A novel polyoxometalate-based metal organic framework (POMOF) constructed from isolated isopolyoxotungstate [H2W11O38]8– cluster, {[Cu2(bpy)(H2O)5.5]2[H2W11O38]·3H2O·0.5CH3CN} (1, where bpy = 4,4′-bpydine), has been synthesized under solvothermal conditions and charaterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray diffraction. In 1, {W11} clusters are alternately linked by two [Cu(2)(H2O)1.5(Ot)3(N)]2+ cations in an unexpected end-to-end fashion leading to a one-dimensional (1D) chain. Adjacent 1D chains are linked through Cu(1)–bpy–Cu(2) in an opposite direction to form a two-dimensional (2D) wavelike sheet along the ab plane. These 2D sheets are further stacked in a parallel fashion giving rise to the 1D channels with copper(II) cations aligned in the channels. The resulting POMOF acted as a Lewis acid catalyst through a heterogeneous manner to prompt cyanosilylation with excellent efficiency.

Sensitization of photo-reduction of the polyoxometalate anions [S2M18O62]4− (M = Mo, W) in the visible spectral region by the [Ru(bpy)3]2+ cation

Abstract: Voltammetric, photo-physical and photo-electrochemical properties of the Dawson polyoxometalate anions α-[S2M18O62]4− (M = Mo, W) are presented, both in the presence and absence of a series of [RuIILn]+/2+ cations [Ln = (bpy)3, (bpy)2(Im)2, (bpy)2(dpq), (bpy)2(box) and (biq)2(box)]. Electrochemical processes for both the anion and RuII/III couples were detected in solutions of the salts [RuIILn]2[S2M18O62] in dimethylformamide (0.1 M Bu4NPF6) by both cyclic and hydrodynamic voltammetries. Responses were also detected when the solid salts were adhered to the surface of a glassy carbon electrode in contact with an electrolyte in which they are insoluble (CH3CN; 0.1M Bu4NPF6). Photolysis experiments were performed on solutions of the salts [R4N]4[S2M18O62] (R = n-butyl or n-hexyl) and [RuIILn]2[S2M18O62] at 355 and 420 nm in dimethylformamide and acetonitrile in the presence and absence of benzyl alcohol (10% v/v). When associated with [Ru(bpy)3]2+, the molybdate anion exhibited a large increase in the quantum yield for photo-reduction at 420 nm. The quantum yield for the tungstate analogue was lower but the experiments again provided clear evidence for sensitization of the photo-reduction reaction in the visible spectral region. The origin of this sensitization is ascribed to the new optical transition observed around 480 nm in static ion clusters {[Ru(bpy)3][S2M18O62]}2− and {[Ru(bpy)3]2[S2M18O62]} present in solution. Measurable photocurrents resulted from irradiation of solutions of the anions with white light in the presence of the electron donor dimethylformamide. Evidence is also presented for possible quencher–fluorophore interactions in the presence of certain [RuIILn]+ cations.

Visible-Light-Driven “On”/“Off” Photochromism of a Polyoxometalate Diarylethene Coordination Complex

Abstract: Herein we report the first photochromic polyoxometalate (POM)-based diarylethene (DAE) coordination complex, prepared by ligation of two cobalt(III)-incorporated borotungstates [BIIIWVI11O39CoIII]6– with the ditopic pyridyl-containing diarylethene (C25H16N2F6S2). The solution-state composition, structure, and stability of the assembly were probed using 1H and 19F nuclear magnetic resonance spectroscopy (NMR), electrospray ionization quadrupolar time-of-flight mass spectrometry (ESI-QTOF-MS), ultraviolet–visible spectroscopy (UV–vis), and small-angle X-ray scattering (SAXS), revealing that the complex self-organizes to adopt a molecular dumbbell structure due to electrostatic and steric considerations. This conformation is a prerequisite for the photocyclization reaction. The assembly was found to be switchable between two states using visible light due to the perturbation of the DAE electronic structure on coordination to the POM. We present photophysical data, including the reaction quantum efficiency of...

Secondary spacer modulated assembly of polyoxometalate based metal–organic frameworks

Abstract: To investigate the influence of a secondary spacer on the resulting structures of POMOFs containing pytz, five new compounds with different dimensionalities, [Cu5(2-pytz)6(H2O)4][SiMo12O40]·3H2O (1), [Cu3(2-pytz)4bipy][H2SiMo12O40]·bipy (2), [Cu3(2-pytz)2(bipy)4(H2O)6][H4SiW12O40]2·6H2O (3), [Cu2(2-pytz)(phen)(OH)]2[SiW12O40]·H2O (4), [Cu3(4-pytz)4(H2O)4][H2SiW12O40]·2H2O (5), were synthesized. When only 2-pytz was employed, compound 1 with a 3D framework was obtained, whereas when the secondary spacers (4,4′-bipy, phen and 4-pytz) were introduced into the reaction system of 1, compounds 2–5 were obtained and exhibit a broad range of structures, including 0D, 1D, 2D and 3D frameworks. It can be observed from the architectures of compounds 1–5 that the secondary spacers have a great effect on the structures of the MOFs, which results in the formation of various dimensional POMOF compounds. Additionally, photocatalytic experiments of 1–5 for the photocatalytic degradation of RhB under UV irradiation were also investigated.

Metastable structures and isotope exchange reactions in polyoxometalate ions provide a molecular view of oxide dissolution

Abstract: Dissolution processes affect the performance of oxides in applications ranging from power generation to catalysis. A study on polyoxometalate ions, which are thought to model oxide surfaces, now suggests that dissolution is controlled by the stability of transient oxygen-stuffed structures.