Search

A case of organic–inorganic hybridized phosphotungstate modified using aromatic organophosphonic acid, K4Na4H11[KCo2(H2O)10P4W24O92{(PhPO)2}]·48H2O (1), was successfully synthesized in conventional aqueous solution. The prominent structural feature is that the total structure of [KP4W24O92{(PhPO)2}]23− resembles a V-shaped structure, which was stabilized by two [Co(H2O)5]2+ ions. Furthermore, it can be connected into a three-dimensional mesh structure using K+ ions. Surprisingly, 1 possesses a remarkably high proton conductivity of 1.59 × 10−2 S cm−1 at 95% RH and 318 K probably due to the fact that its structure contains large amounts of lattice water molecules, coordination water molecules and counter cations. [ABSTRACT FROM AUTHOR]

Nucleic acid aptamers are oligonucleotide chains with molecular recognition properties. Compared with antibodies, aptamers show advantages given that they are readily produced via chemical synthesis and elicit minimal immunogenicity in biomedicine applications. Notably, aptamer-encoded nucleic acid assemblies further improve the binding affinity of aptamers with the targets due to their multivalent synergistic interactions. Specially, aptamers can be engineered with special topological arrangements in nucleic acid assemblies, which demonstrate spatial and valence matching towards antigens on viruses, thus showing potential in the detection and therapeutic applications of viruses. This review presents the recent progress on the aptamers explored for SARS-CoV-2 detection and infection treatment, wherein applications of aptamer-based assembly systems are introduced in detail. Screening methods and chemical modification strategies for aptamers are comprehensively summarized, and the types of aptamers employed against different target domains of SARS-CoV-2 are illustrated. The evolution of aptamer-based assembly systems for the detection and neutralization of SARS-CoV-2, as well as the construction principle and characteristics of aptamer-based DNA assemblies are demonstrated. The typically representative works are presented to demonstrate how to assemble aptamers rationally and elaborately for specific applications in SARS-CoV-2 diagnosis and neutralization. Finally, we provide deep insights into the current challenges and future perspectives towards aptamer-based nucleic acid assemblies for virus detection and neutralization in nanomedicine. [ABSTRACT FROM AUTHOR]

Two Ni-inserted polyoxotantalates, K5.5Na2H0.5[Ni(H2O)2{NiTa10O30(OH)2}]·21H2O (1) and K6Na4[Ni(en){NiTa10O32}]·22H2O (2, en = ethanediamine), were synthesized in this work. Crystallographic data analyses reveal that 1 and 2 have similar configurations. A minor difference between these two structures is that the {Ni(H2O)2} unit in 1 is replaced by {Ni(en)} unit in 2. Notably, the other Ni in 1 and 2 is located as a heteroatom at the center of the {Ta10} unit, which is reported in POTas for the first time. Moreover, 2 exhibits excellent catalytic performance in transesterification reactions in a preliminary exploration of the catalytic ability of the synthesized POTas. [ABSTRACT FROM AUTHOR]

A wheel-shaped Zr-substituted phosphotungstate, [N(CH3)4]2K16Na10.5H10.5[{Zr(C2O4)2}3(PO4)(P6W39O150)]·45H2O (1), was synthesised from a hexavacant Dawson-type precursor [H2P2W12O48]12−via a conventional solution method. Compound 1 features a wheel-shaped polyanion comprising an annular [P6W39O150]36− cluster supported by a turbine-shaped [{Zr(C2O4)2}3(PO4)]3− fragment, with three oxalate groups covalently anchored to W atoms. Compound 1 was systematically characterized by IR, UV, PXRD, TGA and 31P NMR spectra. The 31P NMR spectra over time were monitored to verify the stability of 1 in aqueous solution. This compound possesses remarkable proton conductive behavior with a high conductivity of 1.18 × 10−2 S cm−1 at 368 K. [ABSTRACT FROM AUTHOR]

Cationic exchange resins are used in nuclear power circuits to remove the nuclide ions to maintain the safe and efficient operation of nuclear power plants. Meanwhile, the production of spent resins is expanding significantly due to the rapid technological advancements in the nuclear industry, causing the study of resin treatment to be of great significance. This study reveals the catalytic behavior of Mn from cation exchange resins during molten salt oxidation. Mn has many isotopic ions and a catalytic effect on the treatment process. Kinetic analysis reveals that the introduction of Mn decreases the activation energy of the styrene–divinylbenzene skeleton from 48.164 kJ mol−1 to 41.696 kJ mol−1 and decreases the degradation temperature of the resin by 78 °C. Compared to the original resin, the destruction and removal efficiency of Mn-doped cation exchange resin increased from 75.07% to 85.28% during molten salt oxidation at 650 °C. According to the scanning electron microscope analysis and characterization studies, Mn promotes a 55.71% reduction in the average particle diameter of resin structural fragments. Fourier-transform infrared spectroscopy analysis of the resin residues demonstrates that Mn doping influences the catalytic decomposition of –SO2– and S–O within sulfonic acid groups. This catalytic effect induces destabilization and subsequent ring-opening of the benzene ring. These results imply that Mn doping can facilitate molten carbonate oxidation destruction of cation exchange resins. The X-ray diffraction analysis of waste salt reveals that with increasing oxidation time, the transformation of Mn proceeds as (Mn2O6)6− → (MnO3)2− → (MnO2)− at 750 °C. [ABSTRACT FROM AUTHOR]

A heteropolytungstate cluster [{Ru2O(bpy)2}2{Bi2W32O110}]10− (bpy = C10H8N2) was incorporated into a 2 : 1 type layered porous framework by interweaving the Na+ bridged cluster chains through the hydrogen bonding ability of the bpy ligands. It features multiple pore channels rich in hydrogen-bond network, contributing high conductivities > 10−2 S cm−1 at 298–358 K and 85% RH. [ABSTRACT FROM AUTHOR]

The first Fe-implanted polyoxotantalate (POTa), K12Na14H7.4[Fe10.7Ta1.3O8(OH)8(H2O)2(Ta6O19)6]·114.5H2O (1), has been obtained by self-assembly in alkaline solution. The polyanion consists of six Lindqvist-type {Ta6} units linked together by {Fe10.7Ta1.3}. The compound not only possesses the highest nuclearity transition metal–oxygen cluster, but also has the highest degree of polymerization in the POTa field to date. And 1 possesses remarkable proton conduction. [ABSTRACT FROM AUTHOR]

Limited studies have been reported due to the difficulty of synthesizing multifunctional catalysts to realize the redox reaction path cycle. Herein, two multifunctional Ru-containing polyoxometalate-based photocatalysts were prepared via a controllable synthesis strategy. In particular, the catalyst Cs2Na4H7[(SbW9O33)6{Ru(H2O)5}(RuCl3)(RuO6)2{W(H2O)}6(WO)4{WO2(H2O)}2{WO2(H2O)2}2{WO5(H2O)}]·43H2O exhibited superior catalytic performance compared to the Ru-free isomorphic catalyst. The results demonstrated excellent reaction selectivity obtained by fine-tuning solvent polarity and additives during the catalytic oxidation phase and high catalyst robustness in the photocatalytic reduction phase. The introduction of more ruthenium increases the charge separation efficiency, which is responsible for photocatalysis. For the first time, the closed redox conversion cycle was achieved by a single multifunctional catalyst, where aniline was oxidized into nitrobenzene through a series of separable intermediates (azoxybenzene, azobenzene, and nitrosobenzene), and eventually photoreduced back to aniline. This paper also discusses the relationship between catalytic active site composition and catalytic efficacy, and the underlying reaction mechanisms. [ABSTRACT FROM AUTHOR]

Flexible energy storage systems have become attractive alternatives for applications in wearable energy storage and sensor devices. This study reports a simple electro-polymerization method for the fabrication of PPy films coated on PPy nanotubes (PPy NTs), which are binding-free, self-standing, and could be used as a flexible electrode for supercapacitors. With optimized kinetics for ion transportation, the mass specific capacitance of the flexible porous PPy films can be elevated to 1.36 F cm−2 at a charging/discharging rate of 2 mA cm−2 (0.45 A g−1). The mass specific capacitance of the flexible porous PPy films reaches 6.5 times as large as that of compact PPy films at a scan rate of 20 mV s−1. Furthermore, due to the large free space for volume change, the capacitance fading of the flexible porous PPy films is less than 3% after 10 000 cycles. This novel design provides an efficient method to synthesize high-performance, flexible and low-cost materials used in supercapacitors. [ABSTRACT FROM AUTHOR]

Since the famous Swedish chemist Scheele described molybdenum blue for the first time in 1778, polyoxometalate (POM) chemistry has made significant progress in its more than 200-year history. Compared with the POM chemistry of Mo, W and V, significant improvement of polyoxotantalates (POTas) occurred mainly during the last few years. In this paper, complexes with different structures, including isopolyoxotantalates (IPOTas), organic–inorganic hybrid POTas, Ta/W mixed POMs and heteropolyoxotantalates (HPOTas) with their derivatives, are reviewed, aiming at providing some useful guidance for further exploration and discovery of more exciting POTas with innovative architectures and excellent performances. Herein, we highlight and discuss the structural features of POTas according to various structural types. In addition, the synthesis strategies and related applications, especially in photocatalysis, are reviewed. [ABSTRACT FROM AUTHOR]

Employing the urea oxidation reaction (UOR) instead of the water oxidation reaction can not only decrease the theoretic hydrogen generation cell voltage in sustainable energy conversion but also eliminate urea pollution in water. Herein, we used a facile in situ trapping and pre-modification strategy to synthesize MoC@C and hybrid Ni/WC@C nanoparticles and employed the two materials as hydrogen evolution reaction and UOR catalysts, respectively, in an electrolytic cell. The resultant setup can achieve a catalytic current density of 20 mA cm−2 at a cell voltage of 1.5 V in alkaline solutions and maintain stability for at least 12 h in the same conditions. [ABSTRACT FROM AUTHOR]

An organic–inorganic hybrid polyoxometalate Na5H5.68 [Na0.17Rh0.83III(C6H8N2)2Cl2]2(C8H8N2)2[As4W40O140Rh4IV(C6H4N2S)2]·nH2O (1) containing 5.66 Rh atoms is prepared; to our knowledge, it owns the largest number of Rh atoms in the Rh-POM family. Compound 1 demonstrates good catalytic performance in the reduction of nitrobenzene to aniline and the oxidation of aniline to azobenzene under mild conditions. Moreover, catalyst 1 exhibits high activity, excellent stability and recyclability. [ABSTRACT FROM AUTHOR]

Oxalate bridged Nd-based arsenotungstate, K14Na6H4[{(As2W19O67(H2O))Nd(H2O)2}2(C2O4)]·64H2O (1), was obtained from the reaction of K14[As2W19O67(H2O)], oxalic acid, and NdCl3·6H2O in mildly acidic aqueous solution. The polyanion exhibits a dimeric structure in which the fully deprotonated oxalate ligands bridge two NdIII cations and the arsenotungstate anions act as blocking ligands. The photoluminescence (PL) spectrum of 1 shows the characteristic emission peak of NdIII in the near-infrared (NIR) region. However, the O → W charge-transfer transitions of arsenotungstate cannot effectively sensitize the emission of NdIII cations as confirmed by the emission spectrum, due to the mismatch of the energy gap between 3T1u → 1A1g (21.57 × 103 cm−1) of arsenotungstate components and 4F3/2 → 4I9/2 (11.43 × 103 cm−1) of NdIII cations. Magnetic studies of 1 demonstrate its field-induced single-molecule magnet (SMM) behavior. Direct current magnetic susceptibility studies imply the weak ferromagnetic couplings present between the two neighboring NdIII cations. In addition, the synergy between the coordination configuration of NdIII cations and the intramolecular magnetic interaction was discussed. [ABSTRACT FROM AUTHOR]

Five novel lanthanide-substituted polyoxomolybdates (NH4)5Na3H2[{Ln(H2O)7}2{Mo5O15(1,4-O3PCH2C6H4CH2PO3)}4]·nH2O [Ln = Tb3+ (1), Ho3+ (2), Er3+ (3), Tm3+ (4), Yb3+ (5); n = 33, 32, 41, 30, 47] have been prepared in a conventional aqueous solution reaction of ammonium molybdate with Ln3+ ions and p-xylyenediphosphonic acid. Crystal structure analyses reveal that 1–5 are isomorphic. The prominent architecture characteristic is that their structural units consist of a tetrameric cyclic-shaped [{Mo5O15(1,4-O3PCH2C6H4CH2PO3)}4]16− segment stabilized by two [Ln(H2O)7]3+ cations, which are connected to propagate one-dimensional chain by Ln3+ ions. As is known, compounds 1–5 stand for the first Ln-substituted aromatic-bisphosphonate-functionalized polyoxomolybdates. The solid-state photoluminescence measurement of 1 has been performed at ambient temperature, and it displayed the characteristic emissions of Tb ions based on its 4f–4f transitions. In addition, the magnetic properties of 1–5 compounds show that they all exhibit anti-ferromagnetic interactions. [ABSTRACT FROM AUTHOR]

Ultrafine ternary carbide Co6W6C@C nanoparticles (NPs) were successfully synthesized and these NPs exhibited high catalytic activities for the hydrazine oxidation reaction (HzOR) under alkaline conditions. In a practical O2–hydrazine fuel cell test, its peak power density reached 203 mW cm−2, a value superior to that of the state-of-the-art commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

The first example of Rh-substituted organic–inorganic hybrid arsenotungstate [H2N(CH3)2]8{[Na(H2O)4]NaAs2W22(CH3COO)2O76 Rh2(N(CH3)2)2}·H2O (1) synthesised in an aqueous solution by the conventional method is reported. Two [Rh(N(CH3)2)]3+ fragments are imbedded into the vacancy of the [NaAs2W22(CH3COO)2O76]15− unit by Rh–As bonds [2.439(1) Å], which are observed in POM chemistry for the first time. [ABSTRACT FROM AUTHOR]

A novel ruthenium-containing polyoxometalate-based organic–inorganic hybrid, K4Na9H7.4[(AsW9O33)4(WO2)4{Ru3.2(C3H3N2)2}]·42H2O (1), was successfully synthesized by a one-step hydrothermal method under acidic conditions, which applied a self-assembly strategy between inorganic polyoxometalate based on trivacant [B-α-AsW9O33]9− {AsW9} fragments and an organic ligand, imidazole (C3H4N2). Compound 1 was further characterized by single-crystal X-ray diffraction, PXRD, IR spectroscopy, UV-Vis spectroscopy, ESI-MS, elemental analysis and TGA. Single-crystal X-ray diffraction data reveal that the polyanion consists of four trivacant Keggin-type polyanion {AsW9} building blocks bridged by four {WO6} units, leading to a crown-shaped tetrameric structure [(AsW9O33)4(WO2)4{Ru3.2(C3H3N2)2}]20.4−. The ESI-MS result reveals that the polyanion unit has excellent structural integrity in water. Moreover, the catalysis study of 1 was also further investigated, and the experimental results indicate heterogeneous catalyst 1 presents high efficiency (yield = 98%), excellent selectivity (>99%), and good recyclability for the oxidation of 1-(4-chlorophenyl)ethanol to 4′-chloroacetophenone with commercially available 70% aqueous tert-butyl hydroperoxide {TBHP (aq.)} as the oxidant at room temperature. [ABSTRACT FROM AUTHOR]

Three structurally intriguing polyoxoniobates (PONbs) based on the trivacant B-type α-Keggin ion {TeNb9O33}, H4K(CN3H6)2{[Cu4(2,2′-bipy)4(H2O)2][TeNb9V2O37]}·29H2O (1, 2,2′-bipy = 2,2′-bipyridine), H0.5K5Na2.5{[Cu(en)H2O]3[TeNb9V3O39]}·10H2O (2, en = ethylenediamine), and K3Na5{[Cu(1,3-dap)H2O]3[TeNb9V3O39]}·11H2O (3, 1,3-dap = 1,3-diaminopropane), are assembled by the conventional aqueous solution methods using a series of N-containing organic ligands. In 1, each of the two {VO4} units is attached to two coplanar NbO6 octahedra on the {Nb3O13} cluster of the {TeNb9O33} unit. Differently, three {VO4} units in 2 and 3 are linked to two edge-sharing NbO6 octahedra, respectively. Compounds 1–3 represent the first oxo NbTeV clusters and also the first vanadoniobates based on the trivacant Keggin PONb units. All three compounds were characterised by single-crystal X-ray structural analysis, TGA and IR, ESI-MS and 51V NMR spectroscopy. Furthermore, the magnetic properties of compounds 1 and 2 were also studied. [ABSTRACT FROM AUTHOR]

A 72-nuclearity niobium cluster was synthesized, in which two {CuNb26O76} clusters and one {Nb20O59} cluster are fused in a triangular fashion, resulting in a {Nb12} cavity. Further, the simple nature of the species allowed its investigation by ESI-MS analysis, yielding two subunits with time. [ABSTRACT FROM AUTHOR]

Two new members of highly charged Silverton archetype [NaM12O42]11− were demonstrated in the 3D POM-based frameworks Na3[NaM12O42(Ru(DMSO)3)4]·13H2O (M = Mo (1), W (2)), where the unusual icosahedron coordination of a Na+ ion incubated as a heteroatom is reported for the first time in topical POMs. Furthermore, 23Na NMR was applied to certify the interpretation of X-ray diffraction data concerning Na localization. Additionally, the porous nature of the frameworks 1 and 2 has also been investigated. [ABSTRACT FROM AUTHOR]

A novel 2D nanoscale polyoxometalate based on penta-coordinated Ag+ substituted [P2Mo5O23]6− was successfully designed and synthesized. It can inhibit the growth of E. coli without disturbing the balance of reactive oxygen species in an aqueous solution system. [ABSTRACT FROM AUTHOR]

Three oxalate-bridging lanthanide-based polyoxometalates (Ln-POMs) K17Na2H5[{(As2W19O67(H2O))Ln(H2O)2}2(C2O4)]·50H2O. [Ln = Sm3+ (1), Pr3+ (2), and Ce3+ (3)] were successfully synthesized. The structures were further characterized by single-crystal X-ray diffraction analyses, Raman spectroscopy, elemental analyses, powder X-ray diffraction (PXRD), IR spectra, UV/vis diffuse reflectance spectroscopy, and thermogravimetric analysis (TGA). The structural characterization study reveals that Ln-POMs 1–3 crystallize in the form of the triclinic space group P1¯ and consist of an oxalate bridging di-Ln3+-incorporated H-shaped dimer, which can also be viewed as a combination of two half-units {Ln(As2W19O67(H2O))(H2O)2}222− related by an inversion center. It is worth noting that the opening angle (33.01°) from the [As2W19O67(H2O)]14− fragment in 1–3 is less than that of the [As2W19O67(H2O)]14− precursor (40.99°). Furthermore, the stability of 1–3 in aqueous solution and their solid-state photoluminescence properties have also been investigated in this work. [ABSTRACT FROM AUTHOR]

We present a single molecular polyoxometalate cluster (K41[(P2W12Nb6O62)6{Mn3(OH)3(H2O)6}4{Mn3Na(H2O)16}]·26H2O) with controllable release of a large number of protons (∼40 per molecule) in its aqueous solution upon addition of a base. The deprotonation/protonation process is reversible with the clusters remaining intact. This molecule can also absorb up to 11 protons per cluster when an acid, HCl, was added to its original aqueous solution. To the best of our knowledge, such large proton absorption/release capacity along with excellent stability is unprecedented. [ABSTRACT FROM AUTHOR]

A triangular {Er3} cluster containing polyoxometalate (POM), [Er3(μ3-OH)(H2O)8(AsW9O33)(AsW10O35(DL -mal))]222− (1) (mal = malate), has been obtained via one-pot reactions. Structural analyses demonstrate that three Er3+ ions bridged one μ3-OH to generate a rare μ3-OH-capped triangular {Er3} cluster, which connects two different vacant polyanions to form an unsymmetrical sandwich-type subunit, and adjacent sandwiched subunits are linked through mal ligands to give the targeted dimer. When the Er3+ ions are substituted in whole or in part with Y3+ ions, the diamagnetic yttrium analogue [Y3(μ3-OH)(H2O)8(AsW9O33)(AsW10O35(DL -mal))]222− (2) and diluted sample [Er0.15Y2.85(μ3-OH)(H2O)8(AsW9O33)(AsW10O35(DL -mal))]222− (Er@2) have also been synthesized. Magnetic studies reveal that 1 exhibits field-induced two-step magnetic relaxation processes; the slow relaxation process may arise from intramolecular magnetic interactions, whereas the fast one is likely to originate from the intermolecular dipole–dipole interactions supported by the magnetic results of Er@2. From ab initio calculations, it is found that although the magnetic anisotropies of 1 mainly originate from individual Er3+ fragments, the Er3+–Er3+ interactions have a considerable influence on their slow magnetic relaxation processes. [ABSTRACT FROM AUTHOR]

Three sandwich-type TM-containing (TM = transition metal) organophosphonate-based polyoxotungstate clusters, [TM(H2O)4(SeW6O21)2{Co(OOCCH2NCH2PO3)2}3]12− (TM = Co, Ni), have been successfully synthesized, which are the first reported TM-containing organophosphonate-based selenotungstates. They were structurally characterized by PXRD analyses, IR spectroscopy, TGA analyses, etc. Magnetic measurements show that all three compounds exhibit antiferromagnetic interactions. Besides, Co1 can be used as an efficient heterogeneous catalyst in the Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate under mild conditions (60 °C), and exhibits satisfactory conversion (93%) and high selectivity (99%). [ABSTRACT FROM AUTHOR]

Recently, we demonstrated that the in situ formation of a building block is an attractive synthesis strategy for creating novel clusters with controllable structures. Herein, we present the design and synthesis of the first tantaloselenite polyoxoanion [Se4(TaO2)6(OH)4O17]4− (1) and a series of lanthanide derivatives (RE3+ = Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+). In total, we report seven clusters that vary in both composition and structure but which share the same {Se4(TaO2)6} building block. The compounds are fully characterized by single-crystal X-ray diffraction, IR spectra, TG, and PXRD and their decolorization properties for RhB have also been investigated. Compound 1 exhibits good photocatalytic activity for the decolorization of RhB while the introduction of lanthanide into the framework can also maintain this activity. [ABSTRACT FROM AUTHOR]

Two ruthenium-containing polyoxometalate-based hybrids (Ru-POMs), KH8[Ru3O(Trz)6Cl3]2[(NaO6)W6(H2O)6(AsW9O33)4]·28H2O (1) and H3[Ru3O(Trz)6Cl3]2[(WO)2W(OH)(AsW9O33)2]·6H2O (2), (Trz = 1,2,4-triazole), were successfully isolated by a one-step hydrothermal method under different acidic conditions and further characterized by single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), IR spectroscopy, electrospray ionization and mass spectrometry (ESI-MS), thermogravimetric (TG) analyses and elemental analyses. Single-crystal X-ray diffraction analyses reveal two polyanions comprised of four/two identical trivacant Keggin-type polyanion building blocks, leading to the formation of tetrameric/dimeric assembly stabilized by additional metal–oxo cores, respectively. ESI-MS shows that the polyanion units [(NaO6)W6(H2O)6(AsW9O33)4]11− and [(WO)2W(OH)(AsW9O33)2]5− are intact in mixed solvent. Moreover, the two heterogeneous catalysts with trinuclear ruthenium cations were further investigated, and 1 was found to exhibit much higher yield (94.1%)/conversion (95.1%) and better selectivity (>99%) towards the oxidation of thioanisole to sulfoxide than 2. [ABSTRACT FROM AUTHOR]

Here, an organic–inorganic hybrid lanthanide-based polyoxometalate (Ln-POM) [N(CH3)4]3K2Sm(C7H5O2)(H2O)2(α-PW11O39)·11H2O (1) was successfully synthesized and characterized well by several physicochemical techniques. In the polyanion of 1, the benzoic acid ligand directly binds a Sm3+ ion for the formation of an organic–inorganic hybrid polyanion. This organic–inorganic hybrid structure can effectively sensitize the emissions of the Sm3+ ion, which was confirmed by the photoluminescence and time-resolved emission spectroscopy of 1. The photoluminescence study demonstrates that the Sm3+ ion possesses a relatively high-symmetry coordination geometry, which is consistent with the structural analysis of Sm3+ in 1. Furthermore, the polyanion of 1 can form a 3D 4,8-topology framework through the linkage of K1 and K2 ions. In addition, the photoluminescence properties of 1 have been explored, revealing that 1 shows reversible color-tunable photoluminescence based on the excitation from 260 nm to 350 nm, and emitting colors from blue to pink. [ABSTRACT FROM AUTHOR]

Self-assembly reactions of the Lindqvist-ion salt K7HNb6O19·13H2O, SeO2, and [Cu(2,2′-bipy)]2+ give, depending on different routes, two isopolyoxoniobates based on {Nb16} and {Nb20}, respectively, which, as new members of the very limited isopolyoxoniobate family, are observed for the first time. Furthermore, the solution behavior was investigated to determine the stability of the {Nb16} cluster in water. [ABSTRACT FROM AUTHOR]

A monomeric phosphotungstate-supported rhenium carbonyl derivative, [N(CH3)4]6H4[P2W17O62{Re(CO)3}2]·25H2O (1), has been synthesized in a conventional solution system and structurally characterized by single crystal X-ray diffraction crystallography, IR spectroscopy, thermogravimetric (TG) analyses, X-ray powder diffraction (XRPD), and electrospray ionization mass spectrometry (ESI-MS). To our knowledge, this is the first time that the {Re2} fragment existing in the polyoxoanion has been observed in polyoxometalate-supported metal carbonyl derivatives. Moreover, UV-vis spectroscopy was employed to elucidate the stability of the polyoxoanion, and its electrochemical properties were also investigated. In particular, complex 1 could act as an efficient homogeneous catalyst for selective oxidation of thiophenes. For example, dibenzothiophene (DBT) undergoes up to 99% conversion and 99% sulfone selectivity in acetonitrile with 30% H2O2 as an oxidant. [ABSTRACT FROM AUTHOR]

Three [α2-P2W17O61]10−-based lanthanide-containing polyoxometalates (LCPs) [N(CH3)4]3H8{Ln(H2O)7[Ln(H2O)3Ln(H2O)4(α2-P2W17O61)2]}·48H2O [Ln = La3+ (1), Ce3+ (2), and Pr3+ (3)] were successfully obtained by the reaction of a trivacant Dawson-type precursor [P2W15O56]12− and lanthanide ions under hydrothermal conditions. The compounds 1–3 were fully characterized by single-crystal X-ray diffraction and a series of analytical methods, including elemental analyses, powder X-ray diffraction (PXRD), IR spectroscopy, Raman spectroscopy, UV/vis diffuse reflectance spectroscopy, and thermogravimetric analysis (TGA). Single-crystal X-ray diffraction analyses indicated that 1–3 were isostructural and exhibited a 2D network architecture through the alternative connection of [α2-P2W17O61]10− and lanthanide ions. The photoluminescence properties of 1–3 were investigated at room temperature, and 3 displayed the characteristic emissions of a Pr3+ emitting center, indicating that POMs can transfer energy and sensitize Pr3+ emissions. The reason for the weak emission intensity of Pr3+ emitting ions was because the radiationless losses via a charge-transfer Pr → W state negatively affected the emission of the Pr3+ ions in LCPs. [ABSTRACT FROM AUTHOR]

A novel hetero selenato–phosphato–peroxopolyoxoniobate with the formula Cs4H4[P2Se2Nb6(O2)6O22]·10H2O has been successfully isolated in an acidified aqueous hydrogen peroxide solution. The synthesized cluster represents the first example of a selenium-containing polyoxoniobate. Furthermore, the ESI-MS spectra show that the polyoxoanion structural unit [P2Se2Nb6(O2)6O22]8− remains intact in aqueous solution. [ABSTRACT FROM AUTHOR]

A praseodymium(III)-containing arsenotungstate K16H15Li7[Pr2(H2O)3(pzdc)As3W29O103]2·38H2O (1) (pzdc = pyrazine-2,3-dicarboxylic acid) was synthesized by a conventional aqueous solution method and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and single crystal X-ray diffraction. Structural analysis revealed that compound 1 was constructed by two identical subunits {Pr2(H2O)3(AsW9O33)3W2O4} bridged together by two pzdc ligands. In addition, compound 1 could act as an efficient catalyst for the epoxidation of olefins and oxidation of alcohols with hydrogen peroxide (H2O2) as the oxidant. In particular, the turnover frequency (TOF) in the oxidation of 1-phenylethanol reached up to 10 170 h−1, which is higher than that of previously reported catalysts. [ABSTRACT FROM AUTHOR]

A trimeric ruthenium-substituted isopolyoxotungstate compound Rb10K3H6[SeO3(H9RuIV5.5W30.5O114)]Cl3·48H2O (1) was synthesised using the hydrothermal method. The synthesized compound was thoroughly characterized by elemental analysis, single-crystal X-ray diffraction, and electrospray ionization and mass spectrometry (ESI-MS). Compound 1 comprised three identical Keggin-like {Ru1.83W10.17} building blocks, leading to the formation of rare {Ru5.5W30.5} trimeric assembly stabilized by a capping pyramidal selenite group; it represents the first example of inorganic ruthenium-containing polyoxometalates based on isopolytungstates. Cyclic voltammetry results revealed that compound 1 also showed electrochemical catalytic activity towards the nitrite oxidation reaction in an aqueous solution. [ABSTRACT FROM AUTHOR]

Two isomorphic compounds {[Ln2(H2O)10](Mo8O27)}·8H2O (Ln = Tm (1), Er (2)) were obtained by microwave irradiation, in which β-{Mo8O28} building units are linked via bridge oxygen and lanthanide ions coordinated with {MoO6} octahedra. The synthesis chemical processes have a short reaction time (15 min) with high yields (exceeding 85%). The solid-state photochromic properties of these two compounds were studied, and their color change process and the photochromic mechanism were analyzed. Furthermore, the solid-state photoluminescence properties of these two compounds were investigated and the stability of the luminescence was verified. Finally, variable temperature magnetic susceptibilities indicate that both compounds have anti-ferromagnetic interaction properties and 1/χM values are linear with temperature. [ABSTRACT FROM AUTHOR]

Three tartrate-bridging lanthanide-based tungstoarsenate dimers K11H13[Ln3(H2O)8(OH)2(AsW9O33)(AsW10O35(C4O6H3))]2·nH2O (Ln3+ = Eu3+ (1Eu), n = 50; Tb3+ (2Tb), n = 34; C4O6H6 = tartaric acid) and K15H9[Dy3(H2O)15(OH)2(AsW9O33)(AsW10O35(C4O6H3))]2·21H2O (3Dy) have been synthesized and further characterized by elemental analyses, X-ray powder diffraction, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction. Structural analyses indicate that all the polyanions of 1Eu–3Dy are isostructural, and are composed of two identical asymmetric sandwiched subunits [Ln3(H2O)8(OH)2(AsW9O33)(AsW10O35(C4O6H3))]12– interlinked by two tartrate ligands. Furthermore, the photoluminescence and variable-temperature magnetic properties of 1Eu, 2Tb and 3Dy have also been investigated. [ABSTRACT FROM AUTHOR]

A novel 1-D phosphomolybdate based on a dinuclear copper-substituted Strandberg structure was successfully designed and synthesized. It not only possesses reactive oxygen species (ROS) catalytic ability in aqueous solution, by synergizing the Cu clusters with the building blocks, but also shows good antimicrobial activity. [ABSTRACT FROM AUTHOR]

A monomeric tellurotungstate(iv)-supported rhenium carbonyl derivative: Na2H2[(CH3)4N]6[Te2W20O70{Re(CO)3}2]·20H2O (1) has been successfully isolated and structurally characterized by single crystal X-ray diffraction crystallography, IR and UV-Vis spectroscopy, thermogravimetric analysis, etc. In particular, complex 1 could act as a efficient and reusable heterogeneous catalyst for selective epoxidation of various alkenes including different cycloalkenes, styrene derivatives, internal and long-chain alkenes. For example, cis-cyclooctene undergoes up to 98.2% conversion and ＞99% selectivity at 75 °C in acetonitrile with 30% H2O2 as an oxidant. Additionally, the electrocatalytic property of 1 for NO2− reduction was also investigated. [ABSTRACT FROM AUTHOR]

Three polyoxovanadate-based hybrids {[Ru(phen)3]2[V4O12]}·13H2O (1), [Ru(phen)3]2[V10O28]·15H2O (2), and [Ru(phen)3]2[V6O17]Cl·11H2O (3) (phen = 1,10-phenanthroline) were prepared under hydrothermal conditions and characterized by electron paramagnetic resonance (EPR) spectroscopy, infrared spectroscopy (IR), powder X-ray diffraction (PXRD), thermogravimetric (TG) analysis, X-ray photoelectron spectroscopy (XPS), and single crystal X-ray diffraction analysis. Although the structures of both the cyclic vanadate [V4O12]4− and the [V10O28]6− anions are well-known, interestingly, a novel 1-dimensional (1-D) coordination polymer [V6O17]n4n− anion was constructed from tetranuclear [V4O12]4− and dinuclear [V2O7]4− building blocks, which were linked alternately through corner-shared oxygen atoms. Furthermore, the negative charges of polyoxovanadate [V4O12]4−, [V10O28]6− and [V6O17]4− anions were balanced by two [Ru(phen)3]2+/3+ complex cations. The catalytic properties of compounds 1–3 for the oxidation of 1-phenyl ethanol by tert-butyl hydroperoxide (TBHP) were investigated, and the results demonstrated that 1 and 3 exhibited excellent catalytic activities for the oxidation of 1-phenyl ethanol under mild catalytic conditions. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) are highly versatile materials if paired with various conducting supports. We here present a new prospective approach for obtaining advanced electrocatalytic systems via POMs (1 and 2) nanostructured on Ni foam (NF) to give bimetallic nanohybrid composite materials M0.4Ni0.6/WO3 (M = Rh (3) or Ir (4)). By this pathway, two rare isopolyoctatungstate-based organometallic clusters [Hx(MCp*)4W8O32]·yH2O (in 1, M = Rh, x = 8, y = 23; in 2, M = Ir, x = 4, y = 17.33) have been synthesized via one-pot reactions using [Cp*MCl2]2 (Cp* = pentamethylcyclopentadienyl, M = Rh or Ir) and Na2WO4·2H2O in basic conditions. Compounds 1 and 2 were successfully nanostructured on the surface of commercially available NF and were thermally reduced to M0.4Ni0.6/WO3 (M = Rh (3) or Ir (4)) after annealing at 400 °C for 8 h in a 15% H2/N2 atmosphere. Electrodes modified with the POMs 3 and 4 exhibited remarkable HER activities in a 1 M KOH solution and achieved a current density of 10 mA cm−2 at low overpotentials of about 67 and 35 mV versus RHE, with Tafel slopes of 56 and 34 mV dec−1, respectively. [ABSTRACT FROM AUTHOR]

The double-tartaric bridging Tm-substituted POM derivative [N(CH3)4]6K3H7[Tm(C4H2O6)(α-PW11O39)]2·27H2O (1) was successfully synthesized and well characterized by various physico-chemical analyses. Furthermore, the mixed Dy3+/Tm3+ ion-based POM derivatives [N(CH3)4]6K3H7[DyxTm1−x(C4H2O6)(α-PW11O39)]2·27H2O (3–8) were first synthesized and confirmed by PXRD and IR spectra, indicating compounds 3–8 are isomorphic with 1. The detailed analyses of Ln–O–W bond angle and coordinated aqua ligands around emitting Ln3+ ions have revealed that the mentioned negative factors do not effectively affect the luminescence of emitting Ln3+ ions in 1–8. Investigations of PL emissions reveal that 3–8 can display color-tunable PL properties, emitting color from blue to white to yellow. The study of time-resolved emission spectroscopy of 6 indicates the energy can transfer from the LMCT excited state of POM fragments to Tm3+ and/or Dy3+ ions. Furthermore, the decreased luminescent lifetime of Tm3+ ions in 3–8 reasonably verifies the energy transfer from Tm3+ to Dy3+ ions to efficiently facilitate emissions of the Dy3+ centre. [ABSTRACT FROM AUTHOR]

A new polytungstoarsenate, K6LiH6[Ce4(H2O)14(pzdc)(H2pzdc)As3W29O103]·22H2O (1) (H2pzdc = 2,3-pyrazinedicarboxylic acid), was synthesized via a conventional aqueous solution method. In this synthetic approach, the organic ligand pyrazine dicarboxylate acid was introduced into the arsenotungstate system. The synthesized compound 1 was well characterized using elemental analysis, IR spectroscopy, UV-vis spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. The catalytic activity of compound 1 was tested in acetonitrile to oxidize organosulfur compounds (benzothiophene (BT) and dibenzothiophene (DBT)) with hydrogen peroxide as an oxidant at room temperature. Two substrates were oxidized to their corresponding sulfones with high conversion and selectivity. Taking advantage of this remarkable catalytic move, the 1/H2O2/CH3CN system was further utilized in the oxidation of model fuels (MF) including a mixture of BT and DBT in octane. As a result, the organosulfur compounds in the model fuels were fully converted into their corresponding sulfones. Furthermore, the fluorescence properties of 1 were also investigated. [ABSTRACT FROM AUTHOR]

Two monomeric non-classical tellurium-containing heteropolymolybdate-supported metal carbonyl derivatives (NH4)5H3{[Te2Mo12(OH)O44][Mn(CO)3]}·18H2O (1) and (NH4)8{[Te2Mo12(OH)O44][Re(CO)3]}·13H2O (2) have been successfully isolated in good yields. Compounds 1 and 2 are the first two examples of metal carbonyl derivatives of heteromolybdate with tellurium as the central atom. These two compounds have been thoroughly characterized by single-crystal X-ray diffraction, elemental analyses, X-ray powder diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and UV-Vis spectroscopy. The electrochemical catalytic activities of 1 and 2 including cyclic voltammetry and catalytic oxidation of nitrite have also been investigated. [ABSTRACT FROM AUTHOR]