Hydrothermal assembly and luminescence property of lanthanide-containing Anderson polyoxometalates

Two compounds, {[Sm(H₂O)₅]₂(TeMo₆O₂₄)}·6H₂O (1) and {[Eu(H₂O)₇]₂ (TeMo₆O₂₄)}·5H₂O (2) have been synthesized by hydrothermal reactions and characterized by elemental analyses, IR spectra, thermal stability analyses, X-ray powder diffraction, and single-crystal X-ray diffraction. Compound 1 represents the first example of a 2D layer architecture constructed from Anderson-type polyoxoanions [TeMo₆O₂₄]⁶⁻ and rare-earth ions Ln³⁺. Compound 2 displays a 1D chain structure built up of alternating Anderson-type polyoxoanions [TeMo₆O₂₄]⁶⁻ and rare-earth ions Eu³⁺ along the c-axis. Luminescence measurement of 2 exhibits typical red fluorescent emission of the Eu³⁺ ion at room temperature. Furthermore, the emission is intense enough to be observed macroscopically under UV irradiation (365 nm).     

Computational study of solvent effects and the vibrational spectra of Anderson polyoxometalates

The structures and vibrational frequencies of the type II Anderson heteropolyanions [TeMo6O24]6- and [IMo6O24]5- have been calculated by using density functional theory using a number of common functionals and basis sets. For the first time, Raman intensities have been calculated and the effect of solvent on the modeling has been investigated. The calculated IR and Raman spectral traces are in good agreement with experiment allowing the characteristic group frequencies for this class of polyoxometalate to be identified. The stretching vibrations of the molybdenum-oxygen bonds are predicted to occur at somewhat lower frequencies than in the type I polyoxometalates. Stretching of the heteroatom-oxygen bonds occurs at significantly lower frequencies than in the Keggin anions as a simple consequence of the higher coordination number of the central heteroatom in the Anderson systems. For the [Mo2O7]2- and [Mo6O19]2- ions, the relatively low negative charge leads to small structural changes when solvent is included. In these systems, solvent leads to an increase in the bond polarity and a decrease in the covalent bond orders, resulting in decreases in the calculated frequencies. For the Anderson anions, the higher negative charges leads to greater solvent effects with contraction of the clusters and increases in the frequencies of bands due to stretching of the two, cis-related molybdenum-oxygen bonds.     

Noble metals in polyoxometalates

Polyoxometalates containing noble metal ions, such as ruthenium, osmium, rhodium, palladium, platinum, silver and gold, are a structurally diverse class of compounds. They include both classical heteropolyanions (vanadates, molybdates, tungstates) in which noble metals are present as heteroatoms, as well as the recently discovered class of polyoxometalates with noble metal "addenda" atoms. The focus of this Review is on complexes that should, in principle, exist as discrete molecular species in solution, and which are therefore of interest for their reactivity, their future synthetic utility and potential applications, for example, in catalysis or nanoscience.     

Ionothermal synthesis of polyoxometalates

An emerging approach: In the ionothermal synthesis of transition-metal-oxide clusters an ionic liquid acts as a solvent, structure-directing agent, and charge-compensating species. The method may open new convenient routes for the synthesis of polyoxometalate-based materials.     

The polyoxometalates as precursors in molecular materials

The potentialities of the use of polyoxometalates as precursors for conducting and/or magnetic molecular materials are illustrated with a few examples of their chemical and electrochemical assemblies with organic donors derived from TTF, nitronyl nitroxide radicals and metallocenium radical cations.     

Recent advances in polyoxometalates acid-catalyzed organic reactions

Polyoxometalates (POMs) have conducive properties such as controlled Brønsted and Lewis acidity, high thermal stability, nontoxic nature, tunable solubility, and less corrosiveness. POMs have been extensively applied in catalytic organic reactions and have an exciting prospect for industrial applications. This review summarized recent progress in the application of POMs as acid catalysts for various organic reactions including CC bond formation, CN bond formation, CO bond formation, heterocyclic synthesis reactions, cyanosilylation and hydrolysis reactions. Various POMs catalysts including heteropoly acids (HPAs) and cationic functionalized HPAs with Brønsted acidity, HPAs supported on non-precious metal support with Brønsted acidity (or both Brønsted and Lewis acidity), transition metal substituted POMs with Lewis acidity were applied in above reactions. This review attempts to provide up-to-date information about POMs acid-catalyzed organic reactions and propose future prospects.     

Strandberg-type型多金属氧酸盐的研究进展（英文）

作为多金属氧酸盐材料的重要分支,Strandberg型多金属氧酸盐(例如,[P_2Mo_5O_(23)]~(6-))近些年来由于其独特的与催化、药物、电化学、磁学、荧光相关的结构和性质引起了化学家的广泛关注.Strandberg型多金属氧酸盐有相对小的尺寸,这可能形成不同的架构和稳定的团簇,除了六氧化钼八面体,突出的{PO_4}部分仍然和金属-有机部分配位,这使得它易于构建有机-无机复合材料.本文对Strandberg型多酸的结构特征、合成方法、一系列重要应用和在该领域的应用前景进行了综合的概述.     

Cyclodextrin-induced auto-healing of hybrid polyoxometalates

You'll never walk alone: An auto-healing process of the first host-guest complex involving a polyoxometalate hybrid and a cyclodextrin is reported. Indeed, this inclusion complex allows the complete restoration of the anchored organic moiety released by a basic stress, a process otherwise not fully reversible.     

Recent advances of mixed-transition-metal-substituted polyoxometalates

Polyoxometalates(POMs) have been emerging as one of the most widely-studied interdisciplinary research fields of inorganic chemistry due to their structural diversities and versatile physicochemical properties. The incorporation of transition metals into lacunary POM ligands can lead to the formation of various transition-metal-substituted POMs(TMSPs) with wide potential applications in research areas including medicine, magnetism, functional materials, catalysis, and energy storage. In this rev...     

Current trends in the computational modelling of polyoxometalates

Computational chemistry applied to the study of polyoxometalates has achieved its maturity in the last years. During two decades, important advances have been made using theoretical tools in the comprehension and interpretation of many relevant issues. In the present mini-review, we want to stress that different techniques have been incorporated to the routine of computation: from the very first Hartree?CFock LCAO-SCF calculation on the decavanadate anion, followed by numerous density functional theory?Cbased studies on increasingly complex systems, also applying correlated ab initio techniques for magnetism and, more recently, using molecular dynamics to analyse properties in liquid media, the information provided by computational chemistry gets more and more relevant.     

Layer-by-layer assembly of polyoxometalates into microcapsules

The polyoxometalate (POM) chemistry world has been experiencing an unparalleled development of rapid synthesis of new compounds and slow development of POM-based functional materials and devices. Meanwhile, researchers in the microcapsule world, encouraged by the introduction of the layer-by-layer method, are pursuing good components for constructing functional capsule devices. Here, in view of the versatile properties that POM-based microcapsules may possess, various types of POM-polyelectrolyte composite microcapsules were constructed using the layer-by-layer method. Microscopy reveals that polyoxometalates form nanoparticles on the shell in the presence of cationic polyelectrolytes. These nanoparticles connected with polyelectrolytes constitute the shell and support the microcapsule from collapse after drying, and this is an interesting characteristic different from those of common composite and polyelectrolyte capsules. Fourier transform infrared (FTIR), UV-vis absorption, and X-ray photoelectron spectroscopy (XPS) were used to examine the properties of the POMs in the microcapsules. The obtained microcapsules exhibit higher thermal stability than polyelectrolyte microcapsules. Furthermore, the functions of POMs were maintained when they were assembled into microcapsules. It is proved that microcapsules bearing POMs with redox activity can provide a reduction environment, which can lead to the realization of in situ synthesis of materials, and that microcapsules with photoluminescent POMs as a component can also have a photoluminescent property, providing a way to develop functional capsule devices. This work may provide an opportunity to enrich both the polyoxometalate chemistry and the capsule field.     

多金属氧酸盐催化烯烃环氧化研究进展

综述了以过氧化氢为氧源,多金属氧酸盐催化烯烃环氧化的研究进展,尤其是针对基于多金属氧酸盐的反应控制相转移催化体系近年来的研究进展进行了详细阐述.     

Interaction of polyoxometalates with linear polyamines

Polyoxometalates (POMs) are inorganic metal oxoanions with a negative charge, stabilized in the solid state by the corresponding number of countercations and possibly protons. In aqueous solution, the dissociation of all ion pairs is not necessarily quantitative because this would result in strong electrostatic repulsion among the polyanions. In the present communication, we show that the effective charge of the donut-shaped 30-tungsto-5-phosphate [NaP₅W₃₀O₁₁₀]^14? (P₅W₃₀) is close to its “structural charge” of 14 elementary negative charges in the presence of linear polyamines, namely, poly(allylamine hydrobromide) and poly(l-lysine hydrobromide) in a 10-mM NaBr electrolyte. When phase separation occurs, leading to a precipitate (rich in polyanion) and an almost clear supernatant, the charge ratio of the number of moles of cationic groups to polyanion is close to 14, showing that the effective charge in a solution of P₅W₃₀ is indeed equal to ?14e in the presence of polycations.     

Synthesis and characterization of noble-metal-substituted Dawson-type polyoxometalates

Polyoxometalates substituted by noble metal cations (PdII, RuIII, IrIV) of general formula (Bu4N)n[P2W17M(OH2)O61] are prepared by refilling the vacant site of the lacunary precursor 2-K10P2W17O61. Both 31P- and 183W-n.m.r. studies provide convincing evidence for the above structural assignment. The u.v.-vis and i.r. spectra are consistent with the first row transition metal substituted homologues. Electrochemical investigations by cyclic voltammetry in MeCN revealed four reversible one-electron redox couples, which are ascribed to the tungsten(VIV) process of the tungsten-oxo framework.     

Inorganic crown ethers: sulfate-based Preyssler polyoxometalates

A tungsten crown: The {SO(4)} units were introduced into the {W(30)} crown, resulting in a new Preyssler polyoxoanion {S(5)W(30)} with position-specific, guest, K(+) or Na(+) ions in its geometrical center. The as-prepared polyoxoanion exhibits an interesting ion-selective encapsulation of K(+) and Na(+) (see figure).     

Supramolecular architectures assembled from amphiphilic hybrid polyoxometalates

Polyoxometalate (POM)-based inorganic-organic molecular hybrid clusters have been recently recognized as good candidates to design novel multi-functional materials. Tremendous efforts have been invested in synthesizing many interesting hybrid structures with exceptional chemical and physical properties. Grafting organic ligands to the POM clusters render these functional clusters amphiphilic properties. Here we summarize the current progresses and provide some perspectives, from colloidal chemists' point of view, on the self-assembly of the amphiphilic POM-organic hybrids in solution and at interfaces, as well as the related consequent novel features such as enhanced fluorescent properties.