Search

Six arsenic(III)-capped 12-tungsto-2-arsenates(III) of the type [M2(AsIIIW6O25)2(AsIIIOH)x]n- (M = CrIII, 1; FeIII, 2; ScIII, 3; InIII, 4; TiIV, 5; MnII, 6) have been synthesized in aqueous medium by direct reaction of the elements using a one-pot strategy and structurally characterized by FT-IR spectroscopy, single-crystal XRD, and elemental analysis. Polyanions 1-6 are comprised of two octahedrally coordinated guest metal ions M sandwiched between two {AsW6} units, resulting in a structure with C2h point-group symmetry. Polyanions 1-5 contain tri- and tetravalent metal ion guests M (M = CrIII, FeIII, ScIII, InIII, and TiIV, respectively), and they have one {AsIIIOH} group grafted on each {AsW6} unit, whereas the divalent MnII-containing derivative 6 has two such {AsIIIOH} groups grafted on each {AsW6} unit. Magnetic studies on polyanions 3-5 over the temperature range 1.8-295 K and magnetic fields of 0-7 T confirmed that they are diamagnetic. On the other hand, polyanions 1, 2, and 6 are strongly magnetic and follow the Curie-Weiss law above 30 K. The susceptibility plots of 1 and 6 exhibit broad peaks suggesting short-range antiferromagnetic ordering, while the very weak antiferromagnetic ordering of 2 is overshadowed by traces of a paramagnetic impurity. The magnetization data of 1, 2, and 6 at 1.8 K over 0-7 T were analyzed by using the Heisenberg exchange procedure. Small (negative) values of the obtained J values help in understanding the absence of long-range antiferromagnetic ordering.

We report on the synthesis and structural characterization of four arylarsonate- and phosphonate-capped polyoxomolybdates that exhibit different organic substituents in the para position of the phenyl group. The reaction of arylarsonates (RAsO3, wherein R = 4-BrC6H4 or 4-N3C6H4) with molybdate in aqueous pH 3.5 media resulted in the cyclic hexamolybdates [(BrC6H4As)2Mo6O24]4- (Mo6As2La) and [(N3C6H4As)2Mo6O24]4- (Mo6As2Lb), whereas the reaction of arylphosphonates (R'PO3, wherein R' = 4-O2CC6H4 or 4-O2CC6H4CH2) with molybdate in aqueous pH 3 media resulted in the cyclic pentamolybdates [(O2CC6H4P)2Mo5O21]6- (Mo5P2Lc) and [(HO2CC6H4CH2P)2Mo5O21]4- (Mo5P2Ld), respectively. Polyanions Mo6As2La and Mo6As2Lb comprise a ring of six MoO6 octahedra that is capped on either side by an organoarsonate group, whereas Mo5P2Lc and Mo5P2Ld consist of a ring of five MoO6 octahedra that is capped on either side by an organophosphonate group, with the organic arms protruding away from the metal-oxo core of the polyanions. All four polyanions Mo6As2La, Mo6As2Lb, Mo5P2Lc, and Mo5P2Ld have been characterized in the solid state by single-crystal X-ray diffraction, IR spectroscopy, and thermogravimetric and elemental analysis and in solution by multinuclear NMR (31P, 13C, and 1H). The synthetic procedure of (4-bromophenyl)arsonic acid, BrC6H4AsO3H2, is reported here for the first time.

Interaction of the trilacunary 9-tungstosilicate [A-α-SiW9O34]10- with cobalt(ii), nickel(ii) and zinc(ii) ions in pH 9 aqueous medium at room temperature led to the formation of the respective M4-containing heteropolytungstates [M4(OH)3(H2O)2(α-SiW10O36.5)2]13- (M = Co2+ (1), Ni2+ (2), and Zn2+ (3)). Polyanions 1-3 were characterized in the solid state by single-crystal XRD, FT-IR spectroscopy, and thermogravimetric and elemental analyses. Electrochemical studies showed that the Co2+ ions in 1 can be oxidized to Co3+ and the CVs of the WVI centers of the polyanions feature well-defined and chemically reversible reduction waves. Magnetic measurements on 1 and 2 showed paramagnetism with complex ferromagnetic and antiferromagnetic interactions. A model was presented for extracting the exchange constants for the magnetic exchange interaction.

We report on the synthesis, structure, and physicochemical characterization of the first three examples of neutral palladium‐oxo clusters (POCs). The 16‐palladium(II)‐oxo cluster [Pd16O24(OH)8((CH3)2As)8] (Pd16) comprises a cyclic palladium‐oxo unit capped by eight dimethylarsinate groups. The chloro‐derivative [Pd16Na2O26(OH)3 Cl3 ((CH3)2 As)8] (Pd16Cl) was also prepared, which forms a highly stable 3D supramolecular lattice via strong intermolecular interactions. The 24‐palladium(II)‐oxo cluster [Pd24O44(OH)8((CH3)2As)16] (Pd24) can be considered as a bicapped derivative of Pd16 with a tetra‐palladium‐oxo unit grafted on either side. The three compounds were fully characterized 1) in the solid state by single‐crystal and powder XRD, IR, TGA, and solid‐state 1H and 13C NMR spectroscopy, 2) in solution by 1H, 13C NMR and 1H DOSY spectroscopic methods, and 3) in the gas phase by electrospray ionization mass spectrometry (ESI‐MS)., The first three examples of neutral palladium‐oxo clusters (POCs), Pd16, Pd16Cl, and Pd24, were prepared by simple open‐pot, room‐temperature reactions of palladium(II) salts in sodium dimethylarsinate aqueous solutions. The dimethylarsinate capping groups act as bidentate, monoanionic ligands for the various palladium‐oxo cores. The three POCs were fully characterized in the solid, solution, and gaseous states by a multitude of physicochemical techniques.

We report on the first example of a peroxouranium-containing {P8W48} wheel, [{(UO2)4(O2)4}2(P8W48O184)]40- (1), which was synthesized by a one-pot reaction of UO2(NO3)2·6H2O with the 48-tungsto-8-phosphate wheel [H7P8W48O184]33- and aqueous hydrogen peroxide in a pH 6 lithium acetate solution at 50 °C. Polyanion 1 comprises two tetrauranyl squares with side-on peroxo bridging ligands in the cavity of the {P8W48} wheel, and was isolated as the hydrated potassium-lithium salt K18Li22[{(UO2)4(O2)4}2(P8W48O184)]·133H2O (KLi-1), which was characterized in the solid state by single-crystal X-ray diffraction, as well as thermogravimetric and elemental analyses. A detailed Fourier transform infrared and Raman spectroscopy study was also performed.

We have discovered five bismuth(III)-containing polyoxopalladates (POPs) which were fully characterized by solution and solid-state physicochemical techniques: the cube-shaped [BiPd12O32(AsPh)8]5- (BiPd12AsL), [BiPd12O32(AsC6H4N3)8]5- (BiPd12AsLN), and [BiPd12O32(AsC6H4COO)8]13- (BiPd12AsLC) as well as the star-shaped [BiPd15O40(PO)10H6]11- (BiPd15P) and [BiPd15O40(PPh)10]7- (BiPd15PL), respectively. The organically modified capping groups phenylarsonate, p-azidophenylarsonate, and p-carboxyphenylarsonate were chosen as the azido (-N3) and carboxyl (-COOH) groups open up opportunities to covalently conjugate (via click reaction, amide coupling, etc.) with targeting vectors. The synthesis of p-azidophenylarsonate is reported here for the first time. The effects of the BiIII template and the organoarsonate vs -posphonate capping groups on the resulting POP shape (cube vs star) are discussed. The 209Bi NMR (I = 9/2) spectra of BiPd12AsL, BiPd12AsLN, and BiPd12AsLC revealed narrow peaks (ν1/2 ∼ 200 Hz) at 5470 ppm with a longitudinal relaxation time in the millisecond range (at 8.46 T). The absence of a quadrupolar relaxation contribution could be attributed to the allocation of BiIII in the highly symmetrical cuboid POP host cage. Similar peaks were absent in the 209Bi-NMR spectra of the star-shaped POPs BiPd15P and BiPd15PL due to the less symmetric coordination environment around the central BiIII ion. Further, 205/206Bi-radiolabeled POPs have been synthesized by incorporating a 205/206BiIII ion in the center of the POP structures. Carrier-free 205/206Bi radioisotopes (as surrogates of α-emitting 213Bi) were incorporated into the POP host-cage for the preparation of 205/206BiPd12AsL, 205/206BiPd12AsLN, 205/206BiPd12AsLC, and 205/206BiPd15PL, respectively. The radiometal incorporation was complete (>99% radiochemical yield) in 10 min according to radio-thin-layer chromatography. The 205/206BiPd12AsL polyanion was purified by solid-phase extraction. The incubation in rat serum showed the formation of a 205/206BiPd12AsL-protein aggregate.

The 48‐FeIII‐containing 96‐tungsto‐16‐phosphate, [FeIII 48(OH)76(H2O)16(HP2W12O48)8]36− (Fe48), has been synthesized and structurally characterized. This polyanion comprises eight equivalent {FeIII 6P2W12} units that are linked in an end‐on fashion forming a macrocyclic assembly that contains more iron centers than any other polyoxometalate (POM) known to date. The novel Fe48 was synthesized by a simple one‐pot reaction of an {Fe22} coordination complex with the hexalacunary {P2W12} POM precursor in water. The title polyanion was characterized by single‐crystal XRD, FTIR, TGA, magnetic and electrochemical studies., A very large, discrete 96‐tungsto‐16‐phosphate containing 48 FeIII centers, [FeIII 48(OH)76(H2O)16(HP2W12O48)8]36− (Fe48), has been synthesized and structurally characterized. Polyanion Fe48 comprises eight equivalent {Fe6P2W12} units which are linked end‐on to form a macrocyclic assembly containing more iron centers than any other polyoxometalate known to date (see figure).

We have synthesized and structurally characterized the 4-palladium(II)-containing 30-tungsto-4-arsenate(V), [Pd4(As2W15O56)2]16- (1), which represents the first palladium(II)-containing tungstoarsenate(V). The title polyanion 1 was prepared by a simple one-pot procedure in aqueous medium and characterized by single-crystal X-ray diffraction (XRD), thermogravimetric analysis (TGA), cyclic voltammetry, elemental analysis, and 183W nuclear magnetic resonance (NMR), infrared (IR), and ultraviolet-visible (UV-vis) spectroscopies. Polyanion 1 consists of four Pd2+ ions that are coordinated in a square-planar geometry to two trilacunary [As2W15O56]12- Wells-Dawson fragments resulting in a sandwich-type assembly. Catalytic studies on 1 revealed that it is an efficient catalyst precursor for the Suzuki-Miyaura cross-coupling reactions of various aryl halides in aqueous and nonaqueous media.

Polyoxometalates (POMs) have emerged as potential anode materials for lithium-ion batteries (LIBs) owing to their ability to transfer multiple electrons. Although POM anode materials exhibit notable results in LIBs, their energy-storage mechanisms have not been well-investigated. Here, we utilize various in operando and ex situ techniques to verify the charge-storage mechanisms of a Keplerate-type POM Na2K23{[(MoVI)MoVI5O21(H2O)3(KSO4)]12 [(VIVO)30(H2O)20(SO4)0.5]}·ca200H2O ({Mo72V30}) anode in LIBs. The {Mo72V30} anode provides a high reversible capacity of up to ∼1300 mA h g-1 without capacity fading for up to 100 cycles. The lithium-ion storage mechanism was studied systematically through in operando synchrotron X-ray absorption near-edge structure, ex situ X-ray diffraction, ex situ extended X-ray absorption fine structure, ex situ transmission electron microscopy, in operando synchrotron transmission X-ray microscopy, and in operando Raman spectroscopy. Based on the abovementioned results, we propose that the open hollow-ball structure of the {Mo72V30} molecular cluster serves as an electron/ion sponge that can store a large number of lithium ions and electrons reversibly via multiple and reversible redox reactions (Mo6+ ↔ Mo1+ and V5+/V4+↔ V1+) with fast lithium diffusion kinetics (DLi+: 10-9-10-10 cm2 s-1). No obvious volumetric expansion of the microsized {Mo72V30} particle is observed during the lithiation/delithiation process, which leads to high cycling stability. This study provides comprehensive analytical methods for understanding the lithium-ion storage mechanism of such complicated POMs, which is important for further studies of POM electrodes in energy-storage applications.

Reaction of the mixed-valent Mn12-acetato complex [MnIII8MnIV4O12(CH3COO)16(H2O)4] with the trilacunary Wells-Dawson-type heteropolytungstate [P2W15O56]12- in acidic acetate solution (pH 1.1) resulted in the tetra-MnIII-containing polyanion [MnIII4(H2O)2(P2W15O56)2]12- (1). Single-crystal XRD on Na12[MnIII4(H2O)2(P2W15O56)2]·84H2O (1a) revealed that four MnIII ions form a rhombic Mn4O16 core encapsulated by two [P2W15O56]12- units. X-ray photoelectron spectroscopy (XPS) data confirm the +3 oxidation state of the four manganese ions in 1. Magnetic measurements from 1.8-300 K in a 100 Oe magnetic field allowed for the extraction of full fitting parameters from the susceptibility data for 1. The negative Ja value (Ja = -2.16 ± 0.08 K, Jb = 3.24 ± 1.73 K, g = 2.35 ± 0.040, and ρ = 0.34 ± 0.03) suggests a dominant antiferromagnetic spin exchange interaction between the four MnIII ions, with the positive Jb being an accompanying result of Ja. Electrochemical studies revealed a reversible MnIV/MnIII redox couple in 1 at the +0.80 to +1.1 V potential region with E1/2 = +0.907 V.

Macroions, as soluble ions with a size on the nanometer scale, show unique solution behavior different from those of simple ions and large colloidal suspensions. In macroionic solutions, the counterions are known to be important and well-explored. However, the role of co-ions (ions carrying the same type of charge as the macroions) is often ignored. Here, through experimental and simulation studies, we demonstrate the role of co-ions as a function of co-ion size on their interaction with the macroions (using {Mo72Fe30} and {SrPd12} as models) and the related self-assembly into blackberry-type structures in dilute solutions. Several regimes of unique co-ion effects are clearly identified: small ions (halides, oxoacid ions), subnanometer-scaled bulky ions (lacunary Keggin and dodecaborate ions), and those with sizes comparable to the macroions. Small co-ions have no observable effect on the self-assembly of fully hydrophilic {Mo72Fe30}, while due to hydrophobic interaction and intermolecular hydrogen bonds, the small co-ions show influences on the self-assembly of hydrophobic {SrPd12}. Subnanometer ions, a.k.a. "superchaotropic ions", are still too small to assemble into a blackberry by themselves, but they can coassemble with the macroions, showing a strong interaction with the macroionic system. When the co-ion size is comparable to that of the macroions, they assemble independently instead of assembling with the macroions, leading to the previously reported unique self-recognition phenomenon for macroions.

We report on the synthesis and structural characterization of two series of lanthanide-containing 22-tungsto-2-germanates. The first series corresponds to a family of polyanions with the formula [Ln(β2-GeW11O39)2]13- (LnIII = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Gd (6), Dy (7)), and the second series corresponds to a family with the formula [Ln(β2-GeW11O39)(α-GeW11O39)]13- (LnIII = Ho (8), Er (9), Tm (10)). All compounds were characterized in the solid state by single-crystal and powder XRD, IR, TGA, and SQUID magnetometry. The polyanions were synthesized in aqueous medium by direct reaction of the monolacunary [β2-GeW11O39]8- POM precursor with the corresponding lanthanide salts. The structure of the polyanions consists of an 8-coordinated lanthanide ion in a square-antiprismatic geometry, which is sandwiched either between two [β2-GeW11O39]8- units for 1-7 or between a [β2-GeW11O39]8- and a [α-GeW11O39]8- unit for 8-10. Furthermore, the effect of the central paramagnetic lanthanide ion on the magnetic behavior of the polyanions was investigated, with the erbium-derivative [Er(β2-GeW11O39)(α-GeW11O39)]13- (9) showing single-molecule magnet (SMM) behavior.

We have synthesized and structurally characterized three tetra-(p-tolyl)antimony(III)-containing heteropolytungstates, [{(p-tolyl)SbIII}4(A-α-XW9O34)2]n- [X = PV (1-P), AsV (1-As), or GeIV (1-Ge)], in aqueous solution using conventional, one-pot procedures. The polyanions 1-P, 1-As, and 1-Ge were fully characterized in the solid state and in solution and were shown to be soluble and stable in aqueous medium at pH 7. Biological studies demonstrated that all three polyanions possess significant antibacterial and antitumor activities. The minimum inhibitory concentrations of 1-P, 1-As, and 1-Ge were determined against four kinds of bacteria, including the two pathogenic bacteria strains, Vibrio parahaemolyticus and Vibrio vulnificus. The three novel polyanions also showed high cytotoxic potency in the human cell lines A549 (non-small cell lung cancer), CH1/PA-1 (ovarian teratocarcinoma), and SW480 (colon carcinoma).

We report on the disparity in the assembly behavior of four types of nano-sized macroions induced by isotopic substitution of protium (H) to deuterium (D) in solvents. Macroions with modest charge density can self-assemble into single-layer, hollow, spherical "blackberry"-type structures, with larger assembly sizes representing stronger attractions among the macroions. Kinetically, all assembly processes become slower in D2 O than in H2 O. Thermodynamically, the polyoxometalate {SrPd12 }, the uranium cage {U60 } with alkali metal counterions, and the metal-organic cationic cage {Pd12 L24 } demonstrate similar assembly sizes in both H2 O and D2 O, whereas the metal oxide cluster {Mo72 Fe30 } as a weak acid shows an unusually large assembly size in H2 O-suggesting a stronger contribution from the hydrogen bonding in the last case.

We have prepared the indium(III)-centered, all-acetate-capped polyoxopalladate(II) nanocube [InPd12O8(OAc)16]5– (InPd12Ac16), which can be further used as precursor to form the phosphate-capped (i)...

The class of peroxo-cerium-containing polyoxometalates has been discovered via the synthesis of the 9-peroxo-6-cerium(IV)-containing 30-tungsto-3-germanate, [CeIV6(O2)9(GeW10O37)3]24– (1). Polyanio...

The first two examples of polyoxopalladates(II) (POPs) containing tetravalent metal ion guests, [MO8Pd12(PO4)8]12- (M = SnIV, PbIV), have been prepared and structurally characterized in the solid state, solution, and gas phase. The interactions of the metal ion guests and the palladium-oxo shell were studied by theoretical calculations. The POPs were shown to possess anticancer activity by causing oxidative stress inducing caspase activation and consecutive apoptosis of leukemic cells.

Metallacarboranes are a class of inorganic boron clusters that have recently been recognized as biologically active compounds. Herein, we report on the host-guest complexation of several cobalt bis(1,2-dicarbollide) anions (COSANs) with cyclodextrins (CDs) in aqueous solution. The binding affinities reach micromolar values, which are among the highest known values for native CDs, and exceed those for neutral hydrophobic organic guest molecules. The entrapment of the COSANs inside the cavity of CDs was confirmed using NMR and UV-visible spectroscopy, mass spectrometry, cyclic voltammetry, and isothermal titration calorimetry. Complexation by CDs greatly influences the photophysical and electrochemical properties of COSANs. In combination with indicator displacement assays, a label-free fluorescence-based method was developed to allow real-time monitoring of the translocation of COSANs through lipid bilayer membranes.

We have used discrete polyoxopalladates(II) (POPs) of the MPd12X8 nanocube- and Pd15X10 nanostar-types (M = central metal ion, X = capping group) as molecular precursors (diameter ca. 1 nm) for the formation of supported (SBA-15) metallic nanoparticles. These materials proved to be highly active in the hydrogenation of o-xylene. The characterization of such hydrogenation catalysts revealed that the average size of the resulting alloy particles is quite uniform with diameters ranging from 1 to 3 nm (indicating little to no agglomeration). The central transition-metal ion M n+ (MnII, FeIII, CoII, NiII, CuII, ZnII, PdII) in the POP structure and also the nature of the capping group (AsO43-, SeO32-, PO43-, phenyl-AsO32-) influence the resulting catalytic performance.

Here we report on the synthesis, structure, and characterization of the first example of a polyoxopalladate (POP)-based metal-organic framework (MOF). This novel class of materials comprises discrete polyoxo-13-palladate(II) nanocubes [Pd13O8(AsO4)8H6]8– decorated by four Ba2+ ions on each of two opposite faces. These secondary building units (SBUs) are linked to each other via rigid linear organic groups, resulting in a stable 3D POP-MOF framework, which exhibits interesting sorption as well as catalytic properties.

Despite their attractive properties, internal targeted alpha therapies using 223/224Ra are limited to bone-seeking applications. As there is no suitable chelator available, the search for new carriers to stably bind Ra2+ and to connect it to biological target molecules is necessary. Polyoxopalladates represent a class of compounds where Ra2+ can be easily introduced into the Pd-POM core during a facile one-pot preparation. Due to the formation of a protein corona, the connection to other targeting (bio)macromolecules is possible.

Hypothesis: The layer-by-layer deposition of films including polyoxometalates (POMs) results in a very interesting range of applications in various fields such as electrochemical devices and as photochromic coatings. However, the fundamental knowledge of the parameters responsible for tuning the properties of the film (i.e. relation between the structure and composition of the POM and the properties of the final film) is still lacking. Experiments: The current work establishes the relationship between the film thickness, the quantity of POM incorporated in each layer and the electrochemical response of the (PAH-POM)x coatings, where PAH is poly(allylamine hydrochloride). Findings: The results presented in this work show that the film thickness, composition and electrochemical activity scale proportionally with the number of W atoms in a series of heteropolytungstates ranging from 5 to 48 (P2W5, PW12, P2V3W15, P2W18, P5W30, P8W48). The obtained results allow us to establish a method to predict the behavior as well as the properties of the film based on the nature of the POM used. Keywords: Comparative study; Cyclic voltammetry; Polyelectrolyte multilayers; Polyoxometalates.

International audience; We report on the synthesis and structural characterization of the giant discrete and neutral molecular disk, [Pd40O24(OH)16{(CH3)2AsO2}16] (Pd40), comprising a 40-palladium-oxo core that is capped by 16 dimethylarsinate moieties, resulting in a palladium-oxo cluster (POC) with a diameter of ~2 nm. Pd40, which is the largest neutral Pd-based oxo-cluster, can be isolated either as a discrete species or constituting a 3D H-bonded organic-inorganic framework (HOIF) with a 12-tungstate Keggin ion [SiW12O40] 4or [GeW12O40] 4-. 1 H and 13 C NMR as well as 1H-DOSY NMR studies indicate that Pd40 is stable in aqueous solution, which is also confirmed by ESI-MS studies. Pd40 was also immobilized on a mesoporous support (SBA15) followed by the generation of size-controlled Pd-nanoparticles (diameter ~2-6 nm, as based on HR-TEM), leading to an effective heterogeneous hydrogenation catalyst for the transformation of various arenes to saturated carbocycles.

The 36‐NiII‐containing 54‐tungsto‐6‐silicate, [Ni36(OH)18(H2O)36(SiW9O34)6]6− (Ni36 ) was synthesized by a simple one‐pot reaction of the Ni2‐pivalate complex [Ni2(μ‐OH2)(O2CCMe3)4(HO2CCMe3)4] with the trilacunary [SiW9O34]10− polyanion precursor in water and structurally characterized by a multitude of physicochemical techniques including single‐crystal XRD, FTIR, TGA, elemental analysis, magnetic and electrochemical studies. Polyanion Ni36 comprises six equivalent {NiII 6SiW9} units which are linked by Ni−O−W bridges forming a macrocyclic assembly. Magnetic studies demonstrate that the {Ni6} building blocks in Ni36 remain magnetically intact while forming a hexagonal ring with antiferromagnetic exchange interactions between adjacent {Ni6} units. Electrochemical studies indicate that the first reduction is reversible and associated with the WVI/V couple, whereas the second reduction is irreversible attributed to the NiII/0 couple., The 36‐NiII‐containing 54‐tungsto‐6‐silicate, [Ni36(OH)18(H2O)36(SiW9O34)6]6− (Ni36 ) was discovered and shown to contain more nickel centers than any other polyoxometalate (POMs) known to date. Polyanion Ni36 comprises six equivalent {NiII 6SiW9} units which are linked by Ni−O−W bridges forming a macrocyclic assembly. Magnetic studies indicate antiferromagnetic communication between the six {Ni6} subunits. Electrochemical studies indicate that the first reduction is reversible and associated to the WVI/V couple while the second reduction is irreversible and associated to the NiII/0 couple.

We report on the synthesis and characterization of the first polyoxo-noble-metalate-containing metal-organic framework (MOF) material, wherein the preformed MIL-101 has been impregnated with the discrete, cuboid-shaped polyoxopalladate [Pd13Se8O32]6- (Pd13Se8), leading to the composite Pd13Se8@MIL-101. This material was characterized by FTIR, TGA, elemental analysis, powder-XRD, N2 sorption (BET), SEM-EDX, and XPS. Furthermore, the Pd13Se8@MIL-101 composite was shown to be an effective, stable, and recyclable heterogeneous precatalyst for the Suzuki-Miyaura cross-coupling reaction at room temperature utilizing environmentally benign solvents, such as water and methanol.

Background: Polyoxometalates (POMs) are negatively charged metal-oxo clusters of early transition metal ions in high oxidation states (e.g., WVI, MoVI, VV). POMs are of interest in the fields of catalysis, electronics, magnetic materials and nanotechnology. Moreover, POMs were shown to exhibit biological activities in vitro and in vivo, such as antitumor, antimicrobial, and antidiabetic. Methods: The literature search for this peer-reviewed article was performed using PubMed and Scopus databases with the help of appropriate keywords. Results: This review gives a comprehensive overview of recent studies regarding biological activities of polyoxometalates, and their biomedical applications as promising anti-viral, anti-bacterial, anti-tumor, and anti-diabetic agents. Additionally, their putative mechanisms of action and molecular targets are particularly considered. Conclusion: Although a wide range of biological activities of Polyoxometalates (POMs) has been reported, they are to the best of our knowledge not close to a clinical trial or a final application in the treatment of diabetes or infectious and malignant diseases. Accordingly, further studies should be directed towards determining the mechanism of POM biological actions, which would enable fine-tuning at the molecular level, and consequently efficient action towards biological targets and as low toxicity as possible. Furthermore, biomedical studies should be performed on solutionstable POMs employing physiological conditions and concentrations.

In this study, the in vivo hypoglycemic effect of a donut-shaped polyanion salt (NH4)14[Na@P5W30O110]·31H2O {NaP5W30} and its Ag-containing derivative K14[Ag@P5W30O110]·22H2O·6KCl {AgP5W30}, as well as their hepatotoxicity and nephrotoxicity, was evaluated. In the screening hypoglycemic study, Wistar albino rats with streptozotocin induced diabetes were treated intraperitoneally with three single doses (5, 10, and 20 mg per kg per b.w.) of both investigated polyoxotungstates. The blood glucose levels, measured before and after 2, 4 and 6 h polyoxotungstate application, showed that both studied compounds induced the most pronounced and time dependent glucose lowering effects at the doses of 20 mg kg−1. Thus, daily doses of 20 mg kg−1 were administered to Wistar albino rats orally for 14 days in further toxicity examinations. The serum glucose concentration and biochemical parameters of kidney and liver function, as well as a histopathological analysis of kidney and liver tissues were evaluated 14 days after the polyoxotungstate administration. Both investigated compounds did not induce statistically significant alterations of the serum glucose and uric acid concentrations, as well as some of the liver function markers (serum alanine and aspartate aminotransferases, and alkaline phosphatase activities). However, the significant decrease in serum total protein and albumin concentrations and the increase in biochemical parameters of renal function – serum urea (up to 63.1%) and creatinine concentrations (up to 23.3%) were observed for both polyoxotungstates. In addition, the detected biochemical changes were in accordance with kidney and liver histhopathological analysis. Accordingly, the hepatotoxic and nephrotoxic effects of these potential antidiabetic polyoxotungstates could be considered as mild.

Interaction of the mixed-valent 12-manganese coordination complex [MnIII 8MnIV 4O12(CH3COO)16(H2O)4] with the lacunary 9-tungstoarsenate(V) [A-α-AsW9O34]9− resulted in the 10-manganese(III/IV)-containing 36-tungsto-4-arsenate(V), [MnIII 6MnIV 4O4(OH)12(H2O)12(A-β-AsW9O34)4]22− (1). Polyanion 1 was isolated as a hydrated mixed potassium–sodium salt, K14Na8[MnIII 6MnIV 4O4(OH)12(H2O)12(A-β-AsW9O34)4]·104H2O, which crystallizes in the orthorhombic space group Pbcn and was characterized by FT–IR spectroscopy and single-crystal X-ray diffraction, as well as elemental and thermogravimetric analyses. The title polyanion contains a unique [MnIII 6MnIV 4O4(OH)12(H2O)12]14+ core stabilized within the 36-tungsto-4-arsenate(V) framework.

The palladium(II)-containing 40-tungsto-4-arsenate(III) [Pd2Na2KAs4W40O140(H2O)](21-) (1a) was synthesized by reaction of PdSO4 with the cryptate heteropolyanion [As4W40O140](28-) in potassium acetate buffer. The title compound was characterized by single-crystal XRD, IR, TGA, and elemental analysis.

ConspectusNoble metal catalysts, in particular palladium-containing materials, are of prime commercial interest, because of their role as oxidation catalysts in automobile emission-control systems and reforming catalysts for the production of high-octane gasoline. However, despite almost two centuries of research, the precise structure of such materials is still ill-defined on the sub-nanometer scale, which severely limits the understanding of the underlying catalytic mechanisms. As a burgeoning class of structurally well-defined noble metal oxide nanoclusters, polyoxopalladates (POPs) have been highly rated as ideal models to fully decipher the molecular mechanism of noble metal-based catalysis. Being at the frontier of polyoxometalates (POMs), the chemistry of POPs, which are based exclusively on PdII centers as addenda is currently progressing rapidly, owing to their structural and compositional novelty, high solution stability, combined with promising applications especially as noble metal-based catal...

Here we report on the synthesis and structural characterization of the dithallium(III)-containing 30-tungsto -4-phosphate [Tl2Na2(H2O)2{P2W15O56}2]16- (1) by a multitude of solid-state and solution techniques. Polyanion 1 comprises two octahedrally coordinated Tl3+ ions sandwiched between two trilacunary {P2W15} Wells-Dawson fragments and represents only the second structurally characterized, discrete thallium-containing polyoxometalate to date. The two outer positions of the central rhombus are occupied by sodium ions. The title polyanion is solution-stable as shown by 31P and 203/205Tl NMR. This was also supported by Tl NMR spectra simulations including several spin systems of isotopologues with half-spin nuclei (203Tl, 205Tl, 31P, 183W). 23Na NMR showed a time-averaged signal of the Na+ counter cations and the structurally bonded Na+ ions. 203/205Tl NMR spectra also showed a minor signal tentatively attributed to the trithallium-containing derivative [Tl3Na(H2O)2(P2W15O56)2]14-, which could also be identified in the solid state by single-crystal X-ray diffraction. The bioactivity of polyanion 1 was also tested against bacteria and Leishmania.

International audience

Three types of macroanion-countercation interactions in dilute solution, decided by the strength of electrostatic attraction and the change of hydration shells are reported: minor interaction between macroanions [MO8 Pd12 (SeO3 )8 ]6- (M=Zn2+ or Ni2+ ) and monovalent cations (Na+ , K+ , Rb+ , Cs+ ), leaving their hydration shells intact (solvent-separated ion-pairs); strong binding between macroanions and divalent cations (Sr2+ , Ba2+ ) to form solvent-shared ion-pairs with partial dehydration; very strong electrostatic attraction between macroanions and Y3+ ion with contact ion-pairs formation by severely breaking their original hydration shells and forming new ones. In addition, divalent cations can help the macroanions self-assemble into hollow spherical blackberry structures through counterion-mediated attraction, whereas macroanions with mono- or trivalent cations only stay as discrete ions due to either weak interaction or a small number of bound countercations.

The 15-copper(ii)-containing 36-tungsto-4-silicates [Cu15O2(OH)10X(A-α-SiW9O34)4]25- (X = Cl, 1; Br, 2) have been prepared in 70% yield by reaction of the trilacunary 9-tungstosilicate precursor [A-α-SiW9O34]10- with Cu2+ ions in aqueous pH 8 medium. Both polyanions 1 and 2 were isolated as hydrated mixed potassium/sodium salts and characterized in the solid state by FT-IR, TGA, single-crystal XRD, and elemental analysis. DC magnetic susceptibility measurements from 1.8-300 K established the ground state to be paramagnetic with a magnetic moment corresponding to 15 uncoupled Cu2+ (S = 1/2) ions. EPR measurements and simulations were consistent with this analysis. Electrochemical studies were performed for polyanions 1 and 2 dissolved in solution to elucidate the electroactivity of both copper and tungstate sites. Using 2 as a representative example, the electrocatalytic activity towards CO2 reduction upon deposition on a glassy carbon electrode surface, while retaining selectivity relative to hydrogen evolution, was demonstrated.

In the current study, electrostatically-driven pH responsive, supramolecular hydrogels of the trilacunary Wells-Dawson-type 15-tungsto-2-phosphate polyanion (P2W15) and chitosan hydrochloride (ChCl) were prepared, using methacrylic acid as pH responsive agent using benzoyl peroxide (BPO) as initiator. The prepared hydrogels were characterized by FT-IR, SEM, XRD and thermal analyses (TGA-DSC). The swelling and pH based P2W15 release profile of the hydrogels showed maximum swellability and release at pH 7.4. Different mathematical models were applied, showing that P2W15 release followed supercase transport-II mechanism and zero-order kinetics. The cytotoxicity results showed that free and embedded P2W15 exhibited dose-dependent cytotoxicity against cancer cell lines (MCF-7; HeLa) with minimal effects on normal cells (Vero). The developed hydrogels were administered to the rabbits for determining the pharmacokinetic behavior of the polyanion. Moreover, the developed hydrogel system as well as polyanion concentration used were also checked for its oral tolerability and safety evaluation in rabbits. The histopathological studies, serum chemistry (except blood glucose level) and hematological investigations exhibited that administered hydrogel suspension at maximal tolerable dose (4000mg/kg body weight) and polyanion concentration used (20mg) were safe from in-vivo point of view. The developed hydrogels exhibited desirable qualities of a drug delivery system that can be used for the delivery of the embedded polyanion.

A toxicity evaluation of two Keggin-type heteropolytungstates, K-7[Ti2PW10O40].6H(2)O and K6H [SiV3W9O40].3H(2)O, with different inhibitory potencies toward acetylcholinesterase activity (IC50 values of 1.04 x 10(-6) and 4.80 x 10(-4) mol/L, respectively) was performed. Wistar albino rats were orally treated with single doses (5 and 50 mg/kg) of both investigated compounds. The biochemical parameters of renal (serum urea and creatinine) and liver function (direct and total bilirubin, alanine transaminase, and aspartate aminotransferase) were determined after 24 h and 14 days. A histopathological analysis of liver tissue was carried out 14 days after the polyoxotungstate administration. Both applied doses of the investigated compounds did not induce statistically significant alterations of the renal function markers. However, the polyoxotungstate treatment caused an increase in the activities of serum alanine transaminase and aspartate aminotransferase in a time- and concentration -dependent manner, although statistically significant changes in bilirubin concentrations were not observed. Furthermore, the detected hepatotoxic effect was confirmed by histhopathological analysis that suggested some reversible liver tissue damage two weeks after the treatment, especially in the case of K6H [SiV3W9O40]-3H(2)O. Accordingly, the toxicity of these two polyoxotungstates with anti-acetylcholinesterase effect cannot be considered as a severe one, but their potential clinical application would require a more complex toxicological study.

In the present study electrostatically-driven pH responsive supramolecular, self-assembled hydrogels of the trilacunary Wells-Dawson-type 15-tungsto-2-phosphate polyanion [P2W15O56]12− (P2W15) and polyethyleneimine were prepared. Crosslinking was achieved through electrostatic interactions between cationic polyethyleneimine and P2W15. The pH responsiveness was induced by acrylic acid. Benzoyl peroxide was used as an initiator, for initiating the polymerization reaction, anchoring polyacrylic acid on the polyethyleneimine skeleton. The prepared sea-green color hydrogels were characterized by FT-IR, SEM, XRD and thermal analysis (TGA-DSC). The swelling index, P2W15 release studies and pH responsive properties of the developed supramolecular hydrogels were evaluated at pH 1.2 and 7.4, showing maximum swellability and release characteristics at pH 7.4. For determining the P2W15 release mechanism different mathematical models such as zero order, first order, Higuchi model and Krosmeyer-Peppas models were applied and the results showed that embedded P2W15 release follows zero-order kinetics. The cytotoxicity results showed that naked and embedded P2W15 exhibited dose-dependent cytotoxicity against cancer cell lines (MCF-7; Hela) with minimal effects on normal cells (Vero). The hydrogels developed through electrostatic interactions exhibited desirable qualities of a drug delivery system that can be used for the delivery of the embedded polyanion.

Polyoxometalates (POMs) have been reported as promising electrode materials for energy storage applications due to their ability to undergo fast redox reactions with multiple transferred electrons per polyanion. Here we employ a polyoxovanadate salt, Na6[V10O28], as an electrode material in a lithium-ion containing electrolyte and investigate the electron transfer properties of Na6[V10O28] on long and short timescales. Looking at equilibrated systems, in situ V K-edge X-ray absorption near edge structure (XANES) studies show that all 10 V5+ ions in Na6[V10O28] can be reversibly reduced to V4+ in a potential range of 4–1.75 V vs. Li/Li+. Focusing on the dynamic response of the electrode to potential pulses, the kinetics of Na6[V10O28] electrodes and the dependence of the fundamental electron transfer rate k0 on temperature are investigated. From these measurements we calculate the reorganization energy and compare it with theoretical predictions. The experimentally determined reorganization energy of λ = 184 meV is in line with the theoretical estimate and confirms the hypothesis of small values of λ for POMs due to electrostatic shielding of the redox center from the solvent.

We report on a fast microwave-assisted synthetic procedure of the Wells-Dawson-type 18-tungsto-2-phosphate [P2W18O62]6− with a 35% yield in 24 h, rather than a week using conventional heating.