A d-Methionine-Bonded Nanosized Heteropolyoxotungstate with Photocoloration

A d-methionine-bonded nanosized arsenotungstate, Ba9K10H6[{As2W19O67(H2O)}2{AsW9O33}2{W3O6(H2O)(d-Met)}2{W2O4(OH)(d-Met)}]·60H2O [1; d-Met = d-methionine (C5H11NO2S)], is constructed without the use of lanthanide ions. The polyanion of 1 contains two {As2W19O67(H2O)}14- building blocks and two {B-β-AsW9O33}9- subunits, integrated together with a {W2O4(OH)(d-Met)}2+ and two {W3O6(H2O)(d-Met)}5+ subclusters. Interestingly, 1 displays a highly reversible photocoloration property with a half-life (t1/2) time measured as about 0.793 min.

Discovery and Isolation of Two Arsenotungastate Species: [As4W48O168]36- and [As2W21O77(H2O)3]22

Two novel arsenotungstate species, [As₄W₄₈O₁₆₈]^36- (1a) and [As₂W₂₁O₇₇(H₂O)₃]^22- (2a), have been successfully isolated under a one-pot synthetic method. 1a is the second largest arsenotungstate cluster and is constructed from four {AsW₁₂} clusters combined together. 2a can be described as lacunary sites of {As₂W₁₉} filled by {W₂O₈} units. Compounds 1 and 2 exhibit proton conductivity properties, and the conductivity value of 1 is 5.0 × 10^-3 S cm^-1 at 98% relative humidity and 75 °C. This work proves that the lattice water molecules and polyoxoanions can participate in the formation of a hydrogen bond, acting as effective pathway for intermolecular proton conduction.

Synthesis, Structure, and Catalytic Activities of Two Multi-Rh-Decorated Polyoxometalates

Two multi-Rh-incorporated polyoxometalates [NH₂(CH₃)₂]₁₀[Na₄(H₂O)₈]H₃[As₄W₄₂O₁₄₂(OH)₄(CH₃COO)₂Rh₃(H₂O)₄]·13H₂O·4[NH(CH₃)₂] (1) and [K₄Na(H₂O)₆]KH₁₀[As₄W₄₀O₁₄₀Rh₄(H₂O)₄]·34H₂O (2) have been synthesized in acetate buffer solution. Polyanion 1a is built up atop of an acetate-modified rectangular framework [As₄W₄₂O₁₄₂(OH)₄(CH₃COO)₂]^26-, while polyanion 2a contains a pure inorganic cryptand [As₄W₄₀O₁₄₀]^28-. All Rh atoms of these two compounds share the same hexa-coordinate distorted-octahedral geometry and are embedded into their cavities through As-Rh bonding with a bond length around 2.304(4)-2.436(5) Å. Besides, they not only represent structural novelty but also demonstrate controllable proton conduction properties. Catalysts 1 and 2 can catalyze cycloaddition of epoxides with CO₂ in a solvent-free system in conjunction with 1-ethyl-1-methylpyrrolidinium bromide.

Luminescent Dimeric Oxalate-Bridged Eu3+/Tb3+-Implanted Arsenotungstates: Tunable Emission, Energy Transfer, and Detection of Ba2+ Ion in Aqueous Solution

Two cases of lanthanide (Ln)-implanted arsenotungstates, K₁₇Na₂H₅[{(As₂W₁₉O₆₇(H₂O))Ln(H₂O)₂}₂(C₂O₄)]·87H₂O (Ln = Eu (1), Ln = Tb (2)) and their codoped derivatives Eu_xTb_1-x-POM (x = 0.01 (3), x = 0.04 (4), x = 0.1 (5), x = 0.2 (6)) were prepared and further characterized by powder X-ray diffraction, infrared spectra, and thermogravimetric analyses. An X-ray structural analysis of 1 and 2 indicates that they both present a dimeric oxalate-bridged Ln³⁺-implanted lanthanide arsenotungstate polyanion structure. Under the O → W LMCT excitation at 265 nm of arsenotungstate polyanions, the emissions of Ln³⁺ ions in 1 and 2 are sensitized and the lifetimes are prolonged. Codoped compounds 3-6 demonstrate a color-tunable emission from green to red by adjusting the Eu³⁺/Tb³⁺ ratio. Emission spectra and time-resolved emission spectroscopic studies were performed for 3 to further authenticate the energy transfer processes from excited arsenotungstates to the Eu³⁺ and Tb³⁺ metal ions and also between the Eu³⁺ and Tb³⁺ centers. More interestingly, 1 is an effective fluorescent probe for the recognition and detection of Ba²⁺ ions in aqueous solution. The optical properties of the Ln-implanted arsenotungstate compounds not only expressly reveal distinctive energy transfer processes in those compounds but also broaden the application of POM-based materials in the fluorescence sensing field.

Utilizing the adaptive precursor [As2W19O67(H2O)]14– to support three hexanuclear lanthanoid-based tungstoarsenate dimers

The photoluminescence properties and polyanionic structures of hexanuclear lanthanoid-based tungstoarsenate dimers.

Pyrazine dicarboxylate-bridged arsenotungstate: synthesis, characterization, and catalytic activities in epoxidation of olefins and oxidation of alcohols

The catalytic properties and polyanionic structure of pyrazine dicarboxylate-bridged arsenotungstate are reported.

Synergistic Effect between Different Coordination Geometries of Lanthanides and Various Coordination Modes of 2-Picolinic Acid Ligands Tuning Three Types of Rare 3d-4f Heterometallic Tungstoantimonates

Three types of N-heterocyclic aromatic acid decorated 3d-4f heterometallic Keggin-type tungstoantimonates: Na₄[Ln(H₂O)₅]₂[Fe₄(H₂O)₂(pic)₄(B-β-SbW₉O₃₃)₂]·26H₂O [Ln³⁺ = La³⁺ (1), Pr³⁺ (2), Nd³⁺ (3), Sm³⁺ (4), Eu³⁺ (5)], Na₆H₄[Fe₂W₄O₉(H₂O)₂(Hpic)₄ (B-β-SbW₉O₃₃)₂][Ln(H₂O)₈]₂[Fe₄W₂O₇(H₂O)₄(pic)₂(Hpic)₂(B-β-SbW₉O₃₃)₂]·38H₂O [Ln³⁺ = Gd³⁺ (6), Dy³⁺ (7)], and Na₂H₂{[Ln(H₂O)₆]₂[Fe₄(H₂O)₂(Hpic)₂(pic)₂(B-β-SbW₉O₃₃)₂]}₂·44H₂O [Ln³⁺ = Ho³⁺ (8), Er³⁺ (9), Hpic = 2-picolinic acid] have been prepared. 1-5 comprise a quadripic-inserted Krebs-type [Fe₄(H₂O)₂(pic)₄(B-β-SbW₉O₃₃)₂]^10- moiety supported by two [Ln(H₂O)₅]³⁺ groups on both sides where it can be considered that four pic ligands replace eight aqua ligands located on the original Krebs-type [Fe₄(H₂O)₁₀(B-β-SbW₉O₃₃)₂]^10- fragment to form the [Fe₄(H₂O)₂(pic)₄(B-β-SbW₉O₃₃)₂]^10- moiety. Remarkably, the quadripic-inserted subunits are further concatenated through the coordination role of the pic ligands to create a 3-D heterometallic framework. In contrast, the molecular units of 6-7 contain two kinds of non-Krebs-type quadripic-inserted [Fe₂W₄O₉(H₂O)₂(Hpic)₄(B-β-SbW₉O₃₃)₂]^6- and {[Ln(H₂O)₈]₂[Fe₄W₂O₇(H₂O)₄(pic)₂(Hpic)₂(B-β-SbW₉O₃₃)₂]}^4- moieties. The molecular units of 8-9 contain two identical quadripic-inserted Krebs-type {[Ln(H₂O)₆]₂[Fe₄(H₂O)₂(Hpic)₂(pic)₂(B-β-SbW₉O₃₃)₂]}^2- moieties, and both display a 1-D heterometallic double chain. For all we know, 1-9 stand for the first 3d-4f heterometallic tungstoantimonate hybrids functionalized by pic ligands. Particularly, the solid-state NIR photoluminescence (PL) spectrum in the range of 800-1450 nm of 3 and the solid-state visible PL spectra in the range of 500-750 nm of 4, 5, 7, and 8 at room temperature display the featured fluorescence emission bands stemming from Ln³⁺ cations. In the PL emission procedures of 5 and 7, energy transfer from [B-β-SbW₉O₃₃]^9- fragments and pic ligands to Ln³⁺ ions has been observed. Additionally, the correlated color temperatures of 4, 5, 7, and 8 are indexed to 2731, 2020, 4557, and 1685 K, respectively.

Tellurotungstate-Based Organotin-Rare-Earth Heterometallic Hybrids with Four Organic Components

A family of unprecedented tellurotungstate-based organotin-rare-earth (RE) heterometallic hybrids [H₂N(CH₃)₂]₆H₁₂Na₂ {[Sn(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}₂·25H₂O [RE = Ce^III (1), Pr^III (2), Nd^III (3), Sm^III (4), Eu^III (5), Gd^III (6), Tb^III (7); HIN = isonicotinic acid, HAc = acetic acid] were synthesized and characterized by elemental analyses, IR spectra, UV spectra, thermogravimetric analyses, powder X-ray diffraction, and single-crystal X-ray diffraction. The polyoxoanionic skeletons {[Sn(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}₂^20- of 1-7 are constructed from two symmetrical units {[Sn(CH₃)W₂O₄(IN)][(B-α-TeW₈O₃₁)RE(H₂O) (Ac)]₂}^10- linked by two acetate connectors, which not only represent the first inorganic-organic hybrid RE-substituted tellurotungstates involving three different organic ligands, but also stand for the first samples of organotin-RE heterometallic polyoxometalate derivatives. The solid-state luminescent emission properties of 2-5 mainly display the characteristic emission bands of RE^III cations, whereas during the emission procedure of 7, [B-α-TeW₈O₃₁]^10- segments make a nonignorable contribution to the PL behavior of 7 accompanying by the occurrence of the intramolecular energy transfer from O→W LMCT energy to Tb³⁺ centers. Furthermore, 4@CTAB composites with peanutlike and honeycombed morphologies were prepared by a surfactant cetyltrimethylammonium bromide (CTAB). The time-resolved emission spectra of the 4@CTAB composite with CTAB/4 = 0.033/0.05 consolidate the energy transfer from CTAB to RE^III centers. Variable-temperature magnetic susceptibility measurements for 2, 3, and 4 were performed.

Coding the Assembly of Polyoxotungstates with a Programmable Reaction System

Chemical transformations are normally conducted in batch or flow mode, thereby allowing the chemistry to be temporally or spatially controlled, but these approaches are not normally combined dynamically. However, the investigation of the underlying chemistry masked by the self-assembly processes that often occur in one-pot reactions and exploitation of the potential of complex chemical systems requires control in both time and space. Additionally, maintaining the intermediate constituents of a self-assembled system “off equilibrium” and utilizing them dynamically at specific time intervals provide access to building blocks that cannot coexist under one-pot conditions and ultimately to the formation of new clusters. Herein, we implement the concept of a programmable networked reaction system, allowing us to connect discrete “one-pot” reactions that produce the building block{W₁₁O₃₈} ≡ {W₁₁} under different conditions and control, in real time, the assembly of a series of polyoxometalate clusters {W₁₂O₄₂} ≡ {W₁₂}, {W₂₂O₇₄} ≡ {W₂₂} 1a, {W₃₄O₁₁₆} ≡ {W₃₄} 2a, and {W₃₆O₁₂₀} ≡ {W₃₆} 3a, using pH and ultraviolet–visible monitoring. The programmable networked reaction system reveals that is possible to assemble a range of different clusters using {W₁₁}-based building blocks, demonstrating the relationship between the clusters within the family of iso-polyoxotungstates, with the final structural motif being entirely dependent on the building block libraries generated in each separate reaction space within the network. In total, this approach led to the isolation of five distinct inorganic clusters using a “fixed” set of reagents and using a fully automated sequence code, rather than five entirely different reaction protocols. As such, this approach allows us to discover, record, and implement complex one-pot reaction syntheses in a more general way, increasing the yield and reproducibility and potentially giving access to nonspecialists.

Here we describe a programmable networked reaction system connecting reactors that produce the building block{W₁₁O₃₈} ≡ {W₁₁} under different conditions and control the assembly of a series of polyoxometalate clusters {W₁₂O₄₂} ≡ {W₁₂}, {W₂₂O₇₄} ≡ {W₂₂} 1a, {W₃₄O₁₁₆} ≡ {W₃₄} 2a, and {W₃₆O₁₂₀} ≡ {W₃₆} 3a, using pH and ultraviolet−visible monitoring. This approach led to the isolation of five clusters using a fully automated sequence code, rather than five entirely different reaction protocols.

A wheel-shaped Dy(iii) single-molecule magnet supported by polyoxotungstates

A wheel-shaped Dy(iii) single-molecule magnet with an idealized S₆ symmetry is supported by polyoxotungstates. The anisotropic barrier is extracted from AC susceptibilities and the emission spectrum offers insight into the magneto-optical correlation.

First quadruple-glycine bridging mono-lanthanide-substituted borotungstate hybrids

A class of novel organic–inorganic hybrid quadruple-glycine lanthanide-substituted Keggin-type borotungstates have been synthesized and characterized.

Research progress on polyoxometalate-based transition-metal–rare-earth heterometallic derived materials: synthetic strategies, structural overview and functional applications

This review summarizes the structural types of reported polyoxometalate-based transition-metal–rare-earth heterometallic derived materials (PTRHDMs) together with synthetic strategies, structural motifs and relevant functional applications.

Double-malate bridging tri-lanthanoid cluster encapsulated arsenotungstates: syntheses, structures, luminescence and magnetic properties

Five members of a new family of POM-ligated double-malate bridging tri-lanthanoid clusters have been synthesized and characterized.

Significant developments in rare-earth-containing polyoxometalate chemistry: synthetic strategies, structural diversities and correlative properties

In this article, the major progress in rare-earth containing polyoxometalates made in the past decade involving synthetic strategies, structural characteristics and some significant properties related to optics, catalysis and magnetism is highlighted and discussed.

Construction of polyoxometalates from dynamic lacunary polyoxotungstate building blocks and lanthanide linkers

New polyoxometalates have been constructed from the dynamic building block {B-α-Sb^IIIW₉O₃₃} and lanthanide (Ln) linkers via a stepwise synthetic strategy, exhibiting luminescent properties with their Tb- and Dy-derivatives.

Synthesis and characterization of organotriphosphonate-functionalized TM-containing polyoxotungstates

A new family of organotriphosphonate-functionalized TM-containing polyoxotungstates, K₄H₆[H₄{(AsW₉O₃₃)TM(H₂O)W₅O₁₁(N(CH₂PO₃)₃)}₂(μ₂-O)₂]·24H₂O [TM = Ni (1), Co (2), Mn (3)], have been synthesized from the preformed POM precursor [As₂W₁₉O₆₇(H₂O)]¹⁴⁻.

From a versatile arsenotungstate precursor to a large lanthanide-containing polyoxometalate–carboxylate hybrid

From the versatile precursor [As₂W₁₉O₆₇(H₂O)]¹⁴⁻ through combined disassembly and reassembly processes, the large, POM–carboxylate hybrid K₁₄Li₄H₂₀[As₆W₅₈O₂₀₆Ce₄(pydc)₂(H₂O)₆]·44H₂O was obtained in conventional aqueous solution.