Search results for "Polyoxometalate"

Self-assembly and alterable relaxivity of an organic cation-encapsulated gadolinium-containing polyoxometalate

2012

A new amphiphilic molecule bearing poly(ethylene oxide) (PEO) and quaternary ammonium group, was designed and synthesized to encapsulate paramagnetic Gd(III)-containing polyoxometalate (Gd-POM) through electrostatic interaction for obtaining a water-soluble organic-inorganic hybrid building block based on POM. The yielding organic cation-encapsulated Gd-POM (OCEP-Gd) complex exhibited water-solubility and amphiphility, leading to the spontaneous self-assembly into a regular vesicular structure with PEO chains towards water phase and POM units locating at the middle. The vesicular aggregate which has a regular monolayer structure, was further studied by means of dynamic light scattering, tra…

High nuclearity magnetic clusters: Magnetic properties of a nine cobalt cluster encapsulated in a polyoxometalate, [Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]16⊕

1994

Supramolecular Design of Low-dimensional Carbon Nano-hybrids encoding a Polyoxometalate-bis-Pyrene Tweezer

2014

A novel bis-pyrene tweezer anchored on a rigid polyoxometalate scaffold fosters a unique interplay of hydrophobic and electrostatic supramolecular interactions, to shape carbon nanostructures (CNSs)-based extended architectures.

Heterogeneous photo-assisted catalytic hydration/dehydration reactions based on Keggin and Wells-Dawson type heteropolytungstates

2021

Polyoxometalates (POMs) are a wide class of metal-oxygen clusters that can be applied in acid and oxidation catalysis, medicine, electrochemistry, materials design, or models for self-assembling nanoscale systems as long as green and cheap photocatalysts. Heteropolyacids (HPAs) are a POM subclass extensively used as homogeneous photocatalysts for the oxidation of organic substrates. Dispersing HPAs onto solid supports with a high surface area increases their specific surface area and hence (photo)catalytic activity. This chapter reports the use of selected HPAs, heteropolytungstates, immobilized on different supports as heterogeneous photocatalysts.

Polyoxometalate-based metal-organic frameworks for boosting electrochemical capacitor performance

2019

Abstract Polyoxometalate-based metal-organic frameworks (POMOFs) possess promising applications as capacitors. Herein, we report the syntheses, structures and electrochemical properties of five copper-containing POMOFs: [CuI4H2(btx)5(PW12O40)2]·2H2O (1), [CuIICuI3(H2O)2(btx)5(PWVI10WV2O40)]·2H2O (2), [CuI6(btx)6(PWVI9WV3O40)]·2H2O (3), [CuI4H2(btx)5(PMo12O40)2]·2H2O (4) and [CuIICuI3(btx)5(SiMoVI11MoVO40)]·4H2O (5) (btx = 1,4-bis(triazol-1-ylmethyl) benzene) with potential applications as capacitors. Compounds 1–3 contain the same Keggin-type polyoxometalate (POM) although with different oxidation states, allowing the analysis of the effect of the electronic population on the capacitance pe…

Fragmenting gadolinium: Mononuclear polyoxometalate-based magnetic coolers for ultra-low temperatures

2012

The polyoxometalate clusters with formula [Gd(W 5O 18) 2] 9- and [Gd(P 5W 30O 110)] 12- each carry a single magnetic ion of gadolinium, which is the most widespread element among magnetic refrigerant materials. In an adiabatic demagnetization, the lowest attainable temperature is limited by the presence of magnetic interactions that bring about magnetic order below a critical temperature. We demonstrate that this limitation can be overcome by chemically engineering the molecules in such a way to effectively screen all magnetic interactions, suggesting their use as ultra-low-temperature coolers. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Smart High-κ Nanodielectrics Using Solid Supported Polyoxometalate-Rich Nanostructures

2011

Utilizing Langmuir-Blodgett deposition and scanning probe microscopy, we have investigated the extent to which cations alter the self-assembly processes of hybrid polyoxometalates (POMs) on surfaces. The well-defined 2D hexagonal nanostructures obtained were extensively characterized and their properties were studied, and this has revealed fascinating dielectric behavior and reversible capacitive properties. The nanostructures are extremely stable under ambient conditions, and yet exhibit fascinating self-patterning upon heating. These findings present POMs as effective smart nanodielectrics and open up a new field for future POM applications. (c) 2011 American Chemical Society.

Heteropolyacid-Based Heterogeneous Photocatalysts for Environmental Application

2015

Polyoxometalates (POMs) are a wide class of discrete nanosized transition metal–oxygen clusters. The synthesis of POMs has received great interest not only because they present intriguing architectures but also because they have potential applications in catalysis, medicine, electrochemistry, materials design or models for self-assembling nanoscale systems. Recently, POMs have also been studied as green and cheap photocatalysts. The potentialities of POMs are attributed to their unique structural features; indeed, POMs are photostable and non-toxic, have oxygen-rich surfaces and excellent redox properties and possess photochemical characteristics similar to those of the semiconductor photoc…

Programmable Surface Architectures Derived from Hybrid Polyoxometalate-Based Clusters

2011

The exploration of the self-organization of a range of the polyoxometalate-based molecular structures reveals a diverse range of surface patterns and morphologies on solid substrates of technological interest, including methylated and hydroxylated silicon surfaces (namely, SiCH3 and SiOH). By exploiting the interplay between the intrinsic molecular properties and the surface chemistry as well as dynamic spatiotemporal phenomena (e.g., dewetting), we show that these systems can yield 0D, 2D, and 3D architectures via solution deposition at the solid surface, including nanodots, discs, lamellas, porous networks, and layer-by-layer assemblies. In general, we observed that layer-by-layer growth …

Bimetallic MnIII–FeII hybrid complexes formed by a functionalized MnIII Anderson polyoxometalate coordinated to FeII: observation of a field-induced …

2015

The synthesis and crystal structure of an Anderson POM functionalized with two 2,6-di(pyrazol-1-yl)-pyridine (1-bpp) ligands are reported (compound 1). High-frequency electron paramagnetic resonance (HF-EPR) and magnetic measurements show that it presents a significant negative axial zero-field splitting and field-induced slow relaxation of magnetization due to the presence of isolated MnIII anisotropic magnetic ions. Complexation of 1 with FeII gives rise to a 2D cationic network formed by Anderson POMs coordinated to two FeII ions through the two tridentate 1-bpp ligands and to other two FeII ions through two oxo ligands in compound 2, and to an anionic polymeric network formed by Anderso…