Synthesis, structure and electrochemical characterization of the isopolytungstate (W4O16) held by MnII anchors within a superlacunary crown heteropolyanion {P8W48}

An isopolyanion {W4O16} within archetypal {P8W48} heteropolyanion assembly [(P8W48O184)(W4O16)K10Li4Mn10Na(H2O)50Cl2] 15- (Mn10W4-P8W48) has been synthesized by the reaction of the cyclic superlacunary anion [H7P8W48O184] 33− and Mn(ClO4)2.6H2O in I M LiCl soultion medium at pH 8. The isolated compound has been characterized by single crystal X-ray crystallography, powder X-ray diffraction (PXRD), Fourier-transform infrared (FTIR) spectroscopy, elemental analysis and thermogravimetric analysis. Electrochemical studies were also performed on Mn10W4-P8W48 confirmed the presence of Mn centres bonded to the tunsgtic framework. The novel polyanion [(P8W48O184)(W4O16)K10Li4Mn10Na(H2O)50Cl2] 15- is the first example of macrocyclic complex where an isopolyanion (W4O16) 8- is embedded within in the inner cavity of the {P8W48} and is placed in position by six MnII cations as anchors. Whereas, the exocyclic coordination of the four MnII atoms to {P8W48} yields extended structure by linking neighbouring polyanions through {W−O−Mn−O−W} bridges. Further, the polyanion Mn10W4-P8W48 is the first derivative of {P8W48} with six MnII ions (largest) coordinated to the inner side the crown ring as anchors

Synthesis, Characterization, Electrochemistry, Photoluminescence and Magnetic Properties of a Dinuclear Erbium(III)-Containing Monolacunary Dawson-Type Tungstophosphate: [{Er(H2O)(CH3COO)(P2W17O61)}2]16−

Reaction of the trilacunary Wells−Dawson anion {α-P$_{2}$W$_{15}$O$_{56}$$^{12-}$ with ErIII ion in a 1 M LiOAc/HOAc buffer (pH 4.8) solution produces a dinuclear erbium(III) substituted sandwich-type structure [{Er(H$_{2}$O)(CH$_{3}$COO)(P$_{2}$W$_{17}$O$_{61}$)}$_{2}$]$^{16-}$ (1). The isolated compound was structurally characterized using single crystal and powder X-ray diffraction, FTIR spectroscopy, mass spectrometry and thermogravimetric analysis. The electrochemical, electrocatalytic, photoluminescence and magnetic properties of 1 were investigated

Syntheses, Crystal Structure, Electrocatalytic, and Magnetic Properties of the Monolanthanide-Containing Germanotungstates [Ln(H2_{2}O)n_{n}GeW11_{11}O39_{39}]5−^{5-} (Ln = Dy, Er, n = 4,3)

Two monolanthanide-containing polyanions based on monolacunary Keggin germanotungstates [Ln(H2O)nGeW11O39]5− (Ln = Dy, Er, n = 4,3) have been synthesized in simple one-pot synthetic procedure and compositionally characterized in solid state by single-crystal X-ray diffraction, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis. Electronic absorption and emission spectra of the title compounds in solution were also studied. The [DyIII(H2O)4GeW11O39]5− Keggin POM exhibits a slow relaxation of magnetization. The cyclic voltammetry measurements and mass spectrometry were carried out to check the stability of the compounds in solution. Both polyanions prove efficient in the electrocatalytic reduction of nitrite. To our knowledge, this observation establishes the first example of electrocatalysis of nitrite reduction by all inorganic monolanthanidecontaining germanotungstates family

Directed self-assembly, symmetry breaking, and electronic modulation of metal oxide clusters by pyramidal heteroanions

Mixed valence/metal polyoxometalate (POM) clusters are one of the most interesting host species showing the ability to incorporate a wide range of heteroatoms of various charges and geometries. We report herein, the incorporation of different pyramidal EO32- heteroanions (E = PH, S, Se, Te) which are responsible not only for directing the templated assembly of a family of mixed-metal POMs but also for the symmetry-breaking of the traditional Dawson architecture and modulation of the electronic characteristics of the cluster's shell. The isolated family of POMs consists of four members: (Me2NH2)5Na2[Mo11V7O52(HPO3)]·MeOH·5H2O (1), (NH4)7[Mo11V7O52(SO3)]·12H2O (2), K7[Mo11V7O52(SeO3)]·31H2O (3), (Me2NH2)6Na[Mo11V7O52(TeO3)]·15H2O (4), and were characterized by X-ray structural analysis, electrospray ionization mass spectrometry (ESI-MS), thermogravimetric analysis (TGA), UV-vis, IR, elemental and flame atomic absorption spectroscopy (FAAS) analysis, and inductively coupled plasma optical emission spectroscopy (ICP-OES). Cyclic voltammetry (CV) and electron paramagnetic resonance (EPR) spectroscopic studies in concert with density functional theoretical (DFT) calculations elucidate the effect of the heteroatom on the electronic properties of the cluster

Effet de la force ionique et du pH sur la réponse électrochimique de polyoxométallates de type Keggin sur films de silice mesoporeuse orientés verticalement

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Permeability of Dawson–type polyoxometalates through vertically oriented nanoporous silica membranes on electrode: Effect of pore size and probe charge

International audienceThe voltammetric behavior of bulky heteropolyanions belonging to the Dawson family of polyoxometalates, [P2VmW18-mO62] n-(m = 0, 3, 6), has been investigated at electrodes coated with vertically-aligned mesoporous silica thin films with pore openings in the 2-3 nm range. The experiments have been carried out in acidic medium (pH 0.3-1), where the silica surface is positively charged and thus likely to interact with the negatively charged redox probes, and at various ionic strengths of the medium. Better permeability of the films was clearly observed at lower pH values, corresponding to higher densities of positive charges onto the silica walls, and of films with a larger mesopore size, favoring the mass transport rates through the nanoporous membrane. Diffusion of such bulky anionic redox probes was dramatically influenced by the ionic strength of the medium, being especially restricted at low electrolyte concentrations where the thickness of the electrical double layer became of the same order of magnitude or larger than the mesopore radius, giving rise to very low voltammetric signals. The overall negative charge on POMs had few effects on their mass transport through the film, except at low ionic strength where the most highly charged redox probes gave rise to the lowest current responses

pH-modulated ion transport and amplified redox response of Keggin-type polyoxometalates through vertically-oriented mesoporous silica nanochannels

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Etude du comportement électrochimique des POMs de type Wells-Dawson en solution

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