{SeO2(OH)} Bridging Lanthanide-Containing Antimono-Seleno-Tungstates.

A series of new trigonal pyramidal {SeO2(OH)} bridging lanthanide-containing antimono-seleno-tungstates [H2N(CH3)2]8Na8Cs4H9[Ln2SeW4O11(OH)(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33)]2·32H2O [Ln = Tb (1), Dy (2), Ho (3), Er (4)] have been prepared by the synthetic strategy of simultaneously using the antimonotungstate precursor and simple material in an acidic aqueous solution and structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR spectrometry, and thermogravimetric analysis. Their molecular structures contain an unprecedented hexameric polyoxoanion [Ln2SeW4O11(OH)(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33)]229- constituted by two equivalent trimeric subunits Ln2W4O9(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33) bridged via two µ2-{SeO2(OH)} linkers. Furthermore, the catalytic oxidation of various aromatic sulfides and sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES) by compound 3 as the heterogeneous catalyst has been investigated, exhibiting high conversion and selectivity as well as good stability and recyclability.

{Ti12} Cluster-Added Poly(polyoxometalate) Containing Mixed Trivacant Keggin and Dawson Fragments.

A new high-nuclear Ti-oxo-cluster-added poly(polyoxometalate) Cs2Na19H12[(Cs@Ti12O18)@{(A-α-SiW9O34) (P2W15O56)3}]·29H2O (1) has been made by reacting two types of trivacant precursors with TiOSO4 under hydrothermal conditions. The polyoxoanion of 1 contains one Keggin-type [A-α-SiW9O34]10- and three Dawson-type [P2W15O56]12- fragments that synergistically induce the Ti4+ ions to aggregate at vacant sites, resulting in a large {Ti12}-oxo-cluster cavity sealing a Cs+ ion. It is worth noting that the {Ti12} cluster is built by three edge-shared Ti3O13 ({Ti3}1) cores and one corner-shared Ti3O15 ({Ti3}2) core bridged via 6 µ2-O, which has never been seen before in polyoxometalate chemistry. Significantly, 1 represents the first example of [A-α-SiW9O34]10- and [P2W15O56]12- simultaneously participating in making poly(polyoxometalate).

A Zr-added Dawson-type poly(polyoxometalate).

A novel Zr-added trimer, [H2N(CH3)2]10H14[(Zr2P2W16O61)3]·7H2O (1), has been made under hydrothermal conditions, and contains the highest number of Zr centers in known Dawson-type poly(POM)s. A remarkable feature of this study is the first discovery of a new type of divacant [α-5,10-P2W16O60]14- fragment, which assembles with Zr4+ ions to form a cyclic trimer. Furthermore, 1 as a heterogeneous catalyst exhibits high activity for the selective oxidative degradation of a sulfur mustard simulant CEES.

High-Nuclear Ni-Substituted Poly(polyoxometalate) Containing an Anderson-like {Cs7} Cluster.

A novel high-nuclear Ni-substituted poly(polyoxometalate) [poly(POM)], [H2N(CH3)2]2Na18Cs2H13[(Cs7(H2O)6)@{(PO4)-@(Ni4(OH)3(WO4))3@(B-α-PW9O34)3}2]·30H2O (1), has been successfully developed and structurally characterized. The polyoxoanion of 1 can be viewed as a unique huge sandwich structure made of an unprecedented Cs7(H2O)6 ({Cs7}) cluster core encapsulated by two trimeric [(PO4)@(Ni4(OH)3(WO4))3@(B-α-PW9O34)3]21- subunits, in which the {Cs7} cluster presents an interesting Anderson-like arrangement and is the first example of a classical POM configuration based on the alkali metal cluster in the POM chemistry. The polyoxoanion can also be described as an unusual [(Cs7(H2O)6)@{(PO4)@(Ni4(OH)3(WO4))3}2]19+ cluster packaged by six {PW9} fragments. Furthermore, investigations on the Knoevenagel condensation reaction reveal that 1 has good catalytic activity for the condensation of various aldehydes and malononitrile into corresponding products with excellent yields.

{Ti6}/{Ti10} Wheel Cluster Substituted Silicotungstate Aggregates.

Two novel Ti-oxo wheel cluster substituted silicotungstates (STs) [H2N(CH3)2]9H9[Ti6O6(SiW10O37)3]·11H2O (1) and [H2N(CH3)2]16H10[Ti10O11(SiW10O37)2(SiW9O35)2]·14H2O (2) have been made by hydrothermal reactions. The polyoxoanion of 1 is a ring-shaped trimer where a Ti6O6 ({Ti6}) wheel cluster is encapsulated by three divacant [SiW10O37]10- (SiW10O37) fragments. However, 2 is built by two divacant SiW10O37 units and two rare trivacant [SiW9O35]12- (SiW9O35) fragments and further installs an unprecedented Ti10O11 ({Ti10}) double-wheel cluster. To the best of our knowledge, 2 is rare in POM chemistry. Studies on the catalytic oxidation properties reveal that 1 exhibits high catalytic activity toward the oxidation of various sulfides using H2O2 as an oxidant. Furthermore, 1 can be facilely recycled and reused for at least five cycles without obvious loss of catalytic activity.

A {Ti6W4}-Cluster-Substituted Polyoxotungstate: Synthesis, Structure, and Catalytic Oxidation Properties.

A novel Ti-W-O-cluster-substituted tungstoantimonate (TA), [H2N(CH3)2]3Na4H9[{Ti6W4O18(OH)(H2O)3}(B-α-SbW9O33)3]·20H2O (1), has been made by hydrothermal reactions of trivacant [B-α-SbW9O33]9- units, Ti4+ cations, and WO42- anions in the presence of [H2N(CH3)2]·Cl and structurally characterized. Intriguingly, the polyoxoanion of 1 is constructed from three [B-α-SbW9O33]9- units and a previously unobserved decanuclear heterometallic Ti-W-O cluster [Ti6W4O18(OH)(H2O)3]11+ ({Ti6W4}) that is comprised of an octahedral [Ti6WO6(H2O)3]18+ cluster and an edge-sharing [W3O12(OH)]7- fragment via six W-O-Ti/W linkers. Furthermore, studies on the catalytic oxidation properties reveal that 1 possesses good catalytic activity toward the oxidation reactions of various sulfides and cyclooctene based on the environmentally friendly oxidant H2O2.

A µ-AsO4-Bridging Hexadecanuclear Ni-Substituted Polyoxotungstate.

A novel tetrahedral µ-AsO4-bridging hexadecanuclear Ni-substituted silicotungstate (ST) Na21H10[(AsO4){Ni8(OH)6(H2O)2(CO3)2(A-α-SiW9O34)2}2]·60H2O (1) was made by the reactions of trivacant [A-α-SiW9O34]10- ({SiW9}) units with Ni2+ cations and Na3AsO4·12H2O and characterized by IR spectrometry, elemental analysis, thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD). 1 contains a novel polyoxoanion [(AsO4){Ni8(OH)6(H2O)2(CO3)2(A-α-SiW9O34)2}2]31- built by four trivacant Keggin [A-α-SiW9O34]10- fragments linked through an unprecedented [(AsO4){Ni8(OH)6(H2O)2(CO3)2}2]9+ cluster, where the tetrahedral AsO4 acts as an exclusively µ2-bridging unit to link multiple Ni centers; such a connection mode appears for the first time in polyoxometalate chemistry. Furthermore, the electrochemical and catalytic oxidation properties of compound 1 have been investigated.

Three Zr(IV)-Substituted Polyoxotungstate Aggregates: Structural Transformation from Tungstoantimonate to Tungstophosphate Induced by pH.

Three novel Zr-substituted polyoxotungstate aggregates [H2N(CH3)2]7NaH2[Zr2Sb2O3(A-α-PW9O34)2]·16H2O (1), [H2N(CH3)2]6H12[ZrSb4(OH)O2(A-α-PW8O32)(A-α-PW9O34)]2·33H2O (2), and [H2N(CH3)2]4Na11.5H4.5[Zr4W8Sb4P5O49(OH)5(B-α-SbW9O33)2]·53H2O (3) have been made in hydrothermal reactions of the [B-α-SbW9O33]9- precursor with Zr4+ cations and PO43- anions in the presence of dimethylamine hydrochloride and sodium acetate buffer (pH = 4.8) and structurally characterized. Different pH values induce structural transformation from tungstoantimonate (TA) to tungstophosphate (TP). 1 is a di-Zr-substituted sandwich-type TP, the tetranuclear heterometallic [Zr2Sb2O3]8+ entity sandwiched by two [A-α-PW9O34]9- moieties. 2 is a double sandwich-type structure, which can be perceived as two equivalent sandwiched [Sb3(PW8O32)(PW9O34)]11- further sandwiching one [Sb2Zr2(OH)2O4]4+ core to form a novel large-size sandwich-type architecture. Different from 1 and 2, 3 is a tetra-Zr-substituted sandwiched configuration, in which two [B-α-SbW9O33]9- fragments sandwich a unique 21-core Sb-P-W-Zr oxo cluster ({Zr4W8Sb4P5}). Furthermore, the catalytic oxidation of aromatic thioethers by 3 as the heterogeneous catalyst has been investigated, showing high conversion and remarkable selectivity as well as excellent recyclability.

Nonanuclear Heterometal Five-Layer Sandwich-Type Polyoxometalate.

A new nonanuclear heterometal five-layer sandwich silicotungstate [H2N(CH3)2]6H5NaK{[NaMn8O6(OAc)6][A-α-SiW9O34]2}·34H2O (1) has been made under hydrothermal reactions of MnCl2·4H2O, KMnO4, trivacant [A-α-SiW9O34]10- {SiW9} fragment, and [H2N(CH3)2]·Cl in NaOAc-HOAc buffer (pH = 4.8). The polyoxoanion of 1 is a sandwich architecture, in which the nonanuclear heterometal cluster [NaMn8O6(OAc)6]7+ made of two triangular pyramid clusters [Mn4O3(OAc)3]3+ {Mn4} via a hexacoordinate antitrigonal prism Na+ linkage is encapsulated by two trivacant fragments of {SiW9}. Furthermore, magnetic measurements of compound 1 reveal the existence of antiferromagnetic exchange interactions between the metal centers.

A new octa-Mn-substituted poly(polyoxotungstate).

A novel octa-Mn-substituted silicotungstate (ST) [H2N(CH3)2]8H19Na4{[K(H2O)4WO4][SiMnW10O38]3}[SiMnW10O38]·27H2O (1) has been made by the hydrothermal reaction of the trivacant [A-α-SiW9O34]10- ({SiW9}) building block with Mn2+ and Mn7+ cations in the presence of dimethylamine hydrochloride and systematically characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction. 1 is a tetrameric cluster formed by a hexa-MnII substituted cyclic trimeric {[K(H2O)4WO4][SiMnW10O38]3} unit and a {SiMnW10O38} fragment via two W-O-MnIII linkers. Furthermore, its electrochemistry, thermal stability and magnetic properties have been studied.

Two Ce3+-Substituted Selenotungstates Regulated by N, N-Dimethylethanolamine and Dimethylamine Hydrochloride.

Two multi-Ce3+-substituted selenotungstates (STs), [HDMEA][H2N(CH3)2]4H3Na4[Ce2(H2O)6(DMEA)W4O9(α-SeW9O33)3]·26H2O (1) and [H2N(CH3)2]10H4Na10[Ce2W4O9(H2O)7(α-SeW9O33)3]2·63H2O (2), were prepared by the one-pot approach of sodium tungstate, sodium selenite, and lanthanide nitrate in an acidic water solution in the presence of N, N-dimethylethanolamine (DMEA) or dimethylamine hydrochloride (DMAHC). 1 was obained in the presence of DMEA, whereas 2 was synthesized in the presence of DMAHC. The trimeric polyoxoanion of 1 contains an unusual V-shaped [Se3W29O103]20- group embracing a prominent heterometal oxide fragment, [Ce2(H2O)6(DMEA)W2O5]8+, and the hexameric polyoxoanion of 2 is constructed from two equivalent trimeric [Ce2W4O9(H2O)7(SeW9O33)3]224- subunits through two -O-W-O-Ce-O- linkages. The most worthy of attention is that the polyoxoanion of 1 can be approximatively viewed as a half of the polyoxoanion of 2 because of the coordination and blocking effect of DMEA. The stability of 1 and 2 in different water pH values was studied by electrospray ionization mass spectroscopy (ESI-MS), and the results manifest that 1 and 2 are stable in pH = 3.5-7.5 and 3.5-7.0, respectively. The oxidation reactions of aromatic sulfides catalyzed by H2O2 were studied when 1 or 2 worked as a catalyst, and experimental results reveal that 1 or 2 can serve as available catalysts for the oxidation of aromatic sulfides under mild conditions.

Syntheses, Structures, and Electrochemical Properties of Three New Acetate-Functionalized Zirconium-Substituted Germanotungstates: From Dimer to Tetramer.

Under hydrothermal conditions, three new acetate-functionalized zirconium-substituted polyoxometalates, H4Na2[Na6(H2O)22][Zr4(µ3-O)2(OH)2(OAc)2(α-GeW10O37)2]·32H2O (1), H8K3Na5[Zr6(µ3-O)3(OH)3(OAc)(H2O)(ß-GeW10O37)3]·20H2O (2), H6K4Na12[{Zr5(µ3-OH)4(OH)2}@{Zr2(OAc)2(α-GeW10O38)2}2]·22H2O (3), were synthesized and characterized. In 1, the sandwiched dimer [Zr4(µ3-O)2(OH)2(OAc)2(α-GeW10O37)2]12- was linked to a hexameric [Na6(H2O)22]6+ cluster to form a 1D chain. In 2, the trimer was constructed from three [ß2-GeW10O37]10- units and a new [Zr6O3(OH)3(OAc)(H2O)]14+ cluster. In 3, the tetramer was built by two novel sandwich-type dimers [Zr2(OAc)2(α2-GeW10O38)2]18- and one unique [Zr5(µ3-OH)4(OH)2]14+ core in an approximately orthogonal fashion, showing a staggered tetrahedral polyanion. Also, the electrochemistry and electrocatalytic properties of 3 were studied, exhibiting good catalytic activities toward the reduction of H2O2, BrO3-, and NO2-.

A new tetra-Zr(iv)-substituted polyoxotungstate aggregate.

A new tetra-Zr-substituted tungstophosphate (TP), [H2N(CH3)2]6Na6H8{Zr2[SbP2W4(OH)2O21][α2-PW10O38]}2·50H2O (1), has been made by the hydrothermal reaction of the [B-α-SbW9O33]9- building block with Zr4+ cations and PO43- anions in the presence of dimethylamine hydrochloride and NaOAc-HOAc (pH = 4.8), and further characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), 31P NMR spectroscopy and single-crystal X-ray diffraction. 1 is a toroidal structure formed by two divacant [α2-PW10O38]11- units and two [SbP2W4(OH)2O21]7- fragments linked by four Zr4+ cations. Note that the TP is reassembled with tetrahedral PO4 replacing the triangular pyramidal SbO3 in the [B-α-SbW9O33]9- precursor. In addition, the pendant SbO3 derives from the dissociation of the [B-α-SbW9O33]9- precursor. Furthermore, the electrochemical properties of 1 have been studied in Na2SO4 + H2SO4 supporting electrolyte (0.5 mol L-1), and indicate that 1 exhibits apparent catalytic activity toward H2O2 and BrO3- reduction. The 31P NMR spectrum of 1 exhibits three signals with approximately proportional intensities, which is consistent with the solid-state structure.

Unprecedented Selenium and Lanthanide Simultaneously Bridging Selenotungstate Aggregates Stabilized by Four Tetra-vacant Dawson-like {Se2 W14 } Units.

In the presence of the larger [H2 N(CH3 )2 ]+ and K+ counter cations as structure-stabilizing agents, a class of unprecedented selenium and lanthanide (Ln) simultaneously bridging tetra-vacant Dawson-like selenotungstate aggregates [H2 N(CH3 )2 ]2 Na9 K2 H19 {[Ln4 W4 Se4 O22 (H2 O)5 ](Se2 W14 O52 )2 }2 ⋅60 H2 O [Ln=TbIII (1), DyIII (2), HoIII (3), ErIII (4), TmIII (5), YbIII (6)] have been obtained by the one-pot assembly reaction of Na2 WO4 ⋅2 H2 O, Ln(NO3 )3 ⋅6 H2 O, and Na2 SeO3 under moderately acidic aqueous conditions and the complexes were structurally characterized by elemental analyses, IR spectra, single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. It should be noted that the appropriate molar ratio of Se/W is extremely important in the formation of 1-6 and can effectively ameliorate the yield of 1-6. Moreover, dimethylamine hydrochloride is also indispensable and plays a considerably important role in improving the solubility of Ln ions and stabilizing the structures of 1-6. The main polyoxoanion skeletons of 1-6 are constructed from two sandwich-type tetra-vacant Dawson-like {[Ln4 W4 Se4 O22 (H2 O)5 ](Se2 W14 O52 )2 }16- half-units linked through two W-O-Ln bridges. The sandwich-type half-unit comprises two tetra-vacant Dawson-like [Se2 W14 O52 ]12- fragments encapsulating a unique dodecanuclear Se-Ln-W [Ln4 W4 Se4 O22 (H2 O)5 ]8+ oxo cluster. Their solid-state visible and NIR fluorescent properties and lifetime decay behaviors were measured and their solid-state luminescent spectra mainly demonstrate the characteristic emission bands of Ln3+ ions. Moreover, the dominant wavelengths, the color purity, and correlated color temperatures of 1-5 have been also calculated. In addition, the luminous flux values of 1-5 are 2031, 6992, 3071, 921, and 477 lumen, respectively.

Structural Transformation from Dimerization to Tetramerization of Serine-Decorated Rare-Earth-Incorporated Arsenotungstates Induced by the Usage of Rare-Earth Salts.

Three types of serine-decorated rare- earth-containing arsenotungstate [H2 N(CH3 )2 ]6 NaH[RE2 W4 O10 (H2 O)8 (Ser)2 (B-α-AsW9 O33 )2 ]⋅30 H2 O (RE3+ =Eu3+ , Gd3+ , Tb3+ , Dy3+ , Ho3+ , Er3+ , Tm3+ , Yb3+ , and Y3+ ; 1), [H2 N(CH3 )2 ]6 Na6-x REx H4-2 x [RE4 W8 O19 (H2 O)10+y (OH)2 (Ser)2 (B-α-AsW9 O33 )4 ]⋅n H2 O (RE3+ =Tb3+ , x=1, y=2, n=36; RE3+ =Dy3+ , Ho3+ , Er3+ , Yb3+ , Y3+ , x=0, y=0, n=38; RE3+ = Tm3+ , x=1, y=0, n=38; Ser=serine; 2), and [H2 N(CH3 )2 ]6-2 x Na2+3 x REx H10-6 x+y [RE4 W8 O19 (H2 O)8 (OH)2 (Ser)4 (B-α-AsW9 O33 )4 ]⋅Cly ⋅n H2 O (RE3+ =Ce3+ , Pr3+ , x=1, y=0, n=65; RE3+ =Nd3+ , Sm3+ , x=0, y=0, n=65; RE3+ =Eu3+ , Gd3+ , x=1, y=2, n=45; 3) were synthesized with the participation of the organic solubilizers dimethylamine hydrochloride and l-serine and were structurally characterized. The use of different amounts of rare-earth salts results in the structural transformation from dimerization to tetramerization of types 1-3. Type 1 is a dimeric sandwich-type assembly of a dual-Ser-participating [RE2 W4 O10 (H2 O)8 (Ser)2 ]10+ entity sandwiched by two [B-α-AsW9 O33 ]9- moieties, whereas types 2 and 3 have a tetrameric square structure formed by four [B-α-AsW9 O33 ]9- moieties that anchor a dual/tetra- Ser-participating [RE4 W8 O19 (H2 O)10+y (OH)2 (Ser)2 ]20+ or [RE4 W8 O19 (H2 O)8 (OH)2 (Ser)4 ]20+ core. The solid-state luminescence properties and lifetime-decay behaviors of these compounds were investigated. The chromaticity coordinates, dominant wavelengths, color purities, and correlated color temperatures were also calculated.

Lanthanide-Connecting and Lone-Electron-Pair Active Trigonal-Pyramidal-AsO3 Inducing Nanosized Poly(polyoxotungstate) Aggregates and Their Anticancer Activities.

By virtue of the stereochemical effect of the lone-electron pair located on the trigonal-pyramidal-AsO3 groups and the one-pot self-assembly strategy in the conventional aqueous solution, a series of novel lanthanide-bridging and lone-electron-pair active trigonal-pyramidal-AsO3 inducing nanosized poly(polyoxotungstate) aggregates [H2N(CH3)2]6 Na24H16{[Ln10W16(H2O)30O50](B-α-AsW9O33)8}·97H2O [Ln = Eu(III) (1), Sm(III) (2), Gd(III) (3), Tb(III) (4), Dy(III) (5), Ho(III) (6), Er(III) (7), Tm(III) (8)] were prepared and further characterized by elemental analyses, IR spectra, UV spectra, thermogravimetric (TG) analyses and single-crystal X-ray diffraction. The most remarkable structural feature is that the polyanionic skeleton of {[Ln10W16(H2O)30O50](B-α-AsW9O33)8}(46-) is constructed from eight trivacant Keggin [B-α-AsW9O33](9-) fragments through ten Ln centers and sixteen bridging W atoms in the participation of fifty extraneous oxygen atoms. Notably, 4 and 8 can be stable in the aqueous solution not only for eight days but also in the range of pH = 3.9-7.5. Moreover, the cytotoxicity tests of 4 and 8 toward human cervical cancer (HeLa) cells, human breast cancer (MCF-7) cells and mouse fibroblast (L929) cells were performed by the 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and the cell apoptosis processes were characterized by calcein AM/PI staining experiments, annexin V-FITC/PI staining experiments and morphological changes.