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In this study, an antibacterial complex based on the quinolone antibacterial drug ciprofloxacin (CF) and a polyoxometalate was synthesized, Mo2O5(CF)2(CFd)2(β-Mo8O26)·5H2O (1). Complex 1 was characterized by elemental analysis and X-ray single-crystal diffraction. Single-crystal structural analysis revealed that 1 was made of β-Mo8 clusters, binuclear molybdenum clusters Mo2O5(CF)2(CFd)2, and water molecules. The antibacterial activity of 1 has been tested against three microorganisms (Staphylococcus aureus, Escherichia coli, and Bacillus subtilis strains); the antibacterial activities of 1 were higher than those of free CF at the same mass amounts. The interaction between 1 and calf thymus DNA (CT-DNA) was investigated using Uv-vis spectroscopy to determine the binding constants. The results indicated that intercalation is the probable mode of action, with 1 demonstrating higher binding constants (Kb) to CT-DNA (1.8 × 105 M−1) compared to pure CF (4.9 × 104 M−1). These findings show that the implementation of molybdate for ciprofloxacin modification resulted in the formation of a metal complex with enhanced antibacterial activity over CF and significantly improving its binding affinity to DNA. [ABSTRACT FROM AUTHOR]

Dye adsorption and photocatalytic properties of the phosphotungstate-hexamine hybrid were examined by studying the decolourisation of model dyes methyl orange (MO) and methylene blue (MB) under ultraviolet and sunlight irradiation. Next, the effect of different factors including the initial concentration, pH, catalyst dosage, and H2O2 dosage, on decolourisation was investigated. The results show that the hybrid is a good heterogeneous photocatalyst for the degradation of MO and MB. For 10 mg/L MO, a degradation efficiency of about 90% was achieved in 35 min and 150 min under UV and solar light irradiation in the presence of 0.3 and 0.5 g/L hybrids at pH of 2.5, respectively. The degradation proceeded through photo-excitation of hybrid and dye, followed by decomposition or oxidation of dye by radicals. Quantum chemical calculations based on density functional theory (DFT) were carried out to obtain more information about the details of the electronic structures of the compounds and the interaction of hybrid with MO and MB dye molecules. The results show good agreement between calculated and experimental data. [ABSTRACT FROM AUTHOR]

Giant polyoxomolybdate Na48[H496Mo368O1464S48]·ca.1000 H2O (Mo368) is a strong candidate in materials due to its electrical properties. However, the drawbacks as instability in water and agglomeration in solid are detrimental to their readily integration into functional devices. Surface modification of Mo368 by surfactant can protect Mo368 in chloroform, and disperse Mo368 clusters avoiding to direct contact with each other, further promote the self-assembly of surfactant-encapsulated Mo368 hybrids into ordered porous honeycomb films. A water breath figure acts as good template for the self-assembly into porous honeycomb film at air/water interface. Varying the length of surfactant carbon chains, surfactant concentration, and supporting solution can influence the film morphology. Attributing to the embedded functional inorganic Mo368 clusters and the pore adsorption, as-prepared porous honeycomb film is active to detect hydroquinone with the detection limit of 3.53 µM by an amperometric response method. [ABSTRACT FROM AUTHOR]

Organic-inorganic nanohybrid ionic liquid based on polyoxometalate [H2 [MIMBS]4 [P2W18O62].11H2O] (MIMB-P2W18) has been synthesized and characterized by elemental analysis technique, Fourier transform infrared (FT-IR), 1H, 13C, and 15P nuclear magnetic resonance (NMR), powder X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The catalytic activity of this nanohybrid ionic liquid has been studied in multi-component reactions to generate pyran and spiro indoline derivatives. Tetrahydrobenzo[b]pyrans have been successfully synthesized by one-pot three-component condensation of aldehyde, malononitrile and dimedone (or cyclohexane-1,3-dione/3-methyl-2-pyrazoline-5-one) using MIMB-P2W18 as a heterogeneous nano-catalyst. Furthermore, a set of multi-substituted spiro[indoline-3,4׳-pyrano[2,3-c]pyrazole] has been synthesized from isatin, hydrazinehydrate/phenylhydrazine, ethyl acetoacetate and malononitrile/ethyl cyanoacetate in the presence of the same catalyst via one-pot four-component method at room temperature. These procedures have several advantages such as high yields of product, easy work-up procedure, short reaction time and stability, non-toxicity, cheapness and reusability of the catalyst. [ABSTRACT FROM AUTHOR]

Polyoxometalate-based composite materials have recently attracted extensive attention due to their unique structural characteristics and physicochemical properties. In the present work, a flexible anti-UV blocker compatible with cotton fabric was prepared by simple covalent bond self-assembly of carboxyl group (−COOH) and phosphomolybdate. The resultant cotton fabrics were investigated and confirmed by FT-IR, PXRD and SEM-EDS, demonstrating the successful preparation of polyoxometalate-based composite fabric. The UV spectrum of as-designed composite fabric imparts excellent UV absorption capacity and the UPF value reaches 397.19, which is far superior to original cotton (7.09). Furthermore, the blocker was tested on the photosensitive material in direct UV irradiation, which proved its outstanding performance as a flexible, wearable, and visualized UV blocker. In addition, the experimental results confirmed that the prepared composite material exhibited an excellent and stable UV resistant performance (UPF: 100+) after 5 days UV aging irradiation and five times washing. The proposed fabrication strategy could promisingly endow polyoxometalate-based fiber materials with extensive applicability potential. [ABSTRACT FROM AUTHOR]

In this study, we attempted to intercalate the Keggin polyoxometalate (POM) anion SiW12O404− with NiAl-layered double hydroxide using a facile ion-exchange technique under a N2 atmosphere. The obtained solids were characterized via X-ray diffraction analysis, Fourier-transform infrared spectroscopy, N2 adsorption-desorption isotherms, scanning and transmission electron microscopes to evaluate their surface morphology. Furthermore, the synthesized materials were employed as novel adsorbents for the removal of malachite green (MG) dye from aqueous solutions. The intercalation was successful. The synthesized material as an adsorbent for the removal of MG can be used for the removal of cationic dyes from aqueous solutions. The adsorption kinetics study showed that the adsorption of MG onto NiAl-POM best fitted the pseudo-second-order model, which indicated that the adsorption process was conducted chemically. Moreover, the adsorption isotherm revealed that the adsorption occurred in a monolayer system. The regeneration process showed that the high effectivity adsorption process after fifth cycles adsorption for NiAl-POM. [ABSTRACT FROM AUTHOR]

This study introduces coloured titanium dioxide nanotubes by phosphotungstate hybrid as an activated photocatalyst for the degradation of organic pollutants under visible and solar light irradiation. The prepared coloured TiO2 nanotubes are characterised by Fourier transform infrared spectroscopy, powder X-ray diffraction, diffuse reflectance spectrometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy and N2 adsorption–desorption isotherms. Then, performance of this catalyst is evaluated using decolourisation of model dyes methylene blue (MB), methyl orange (MO) and mixtures of MB and MO solutions. It is confirmed that the presence of coloured hybrid in the context of white TiO2 enables photocatalytic activity in the visible and solar light. Also, its noticeable efficiency is verified in the photodegradation of organic dyes and its reusability without any significant loss of activity. Removal is via combination of adsorption and then photocatalytic degradation through oxidation by •OH radicals or reduction by reduced polyoxometalate. While the visible light is not able to degrade alone MO solution in the presence of composite, it degrades the MO mixed with MB solution. [ABSTRACT FROM AUTHOR]

Unfavorable electron recombination, which hinders the efficiency of dye-sensitized solar cells (DSSCs), usually occurs at the TiO2/dye/electrolyte interface on a photoanode. Polyoxometalates (POMs), as good electron acceptors, can be used as electron-transfer materials in DSSCs to improve electron transport in TiO2 and reduce electron recombining on the interface of a photoanode. In this paper, the pure inorganic sandwich-type POM Na9[Na3(H2O)6Cu3(H2O)3(SbW9O33)2]·40H2O (Cu3Na3POM) was mixed with TiO2 to form nanocomposites by simple sol-gel method. X-ray photoelectron spectroscopy (XPS) proved that Cu3Na3POM and TiO2 combined. Then the nanocomposite was doped with P25 to form Cu3Na3POM@TiO2/P25 photoanodes which were applied to the DSSCs. The Cu3Na3POM improved the transfer and recombination of electrons in the photoanode, proved by open circuit voltage decay (OCVD) and electrochemical impedance spectroscopy (EIS). Scanning electron microscopy (SEM) and ultraviolet-visible (UV-vis) absorption spectra showed that Cu3Na3POM optimized the morphology of the photoanode and the adsorption capacity of dye. The electrochemical test showed that the photoelectric conversion efficiency of DSSCs with Cu3Na3POM@TiO2/P25 photoanodes was enhanced to 6.91%, which was 13.66% higher than the DSSCs without Cu3Na3POM. [ABSTRACT FROM AUTHOR]

In this manuscript, a new hybrid nanocatalyst (PMo10Ni2/ZnS@CS) based on di-substituted heteropolyanion (PMo10Ni2) and ZnS quantum dot was synthesized via the hydrothermal method. PMo10Ni2/ZnS@CS is a candidate for removal of environmental pollutants. The synthesized hybrid nanocatalyst was analyzed by TEM, UV-vis, FT-IR, XRD, and EDX techniques. The results of XRD analysis showed the average crystallite size of the PMo10Ni2/ZnS@CS nanocomposite particles is about 33 nm, which was consistent with the TEM results. The nano-catalytic activity of PMo10Ni2/ZnS@CS hybrid nanocomposite was investigated in photocatalytic decolorization of organic dyes. The experimental results showed that the inorganic-organic hybrid nanocomposite (PMo10Ni2/ZnS@CS) had excellent photocatalytic efficiency with 98% dye removal. The recovery of the photocatalyst in the decolorization process was investigated and the results indicate a reduction of photocatalytic power after the second and third stage recovery, respectively. In the present study, PMo10Ni2/ZnS@CS was proposed as a heterogeneous nanocatalyst with broad nanocatalytic applications of dye removal. [ABSTRACT FROM AUTHOR]

By using different transition metal ions three isostructural Anderson based compounds were obtained, [M2II(H3bdpm)2TeMo6O24(H2O)6] (M = Co (1); Cd (2); Zn (3)). Compounds 1-3 can act as photoelectric sensors for detecting inorganic ions. As electrochemical sensors, 1 and 2 can detect nitrite with excellent sensitivity and wide concentration range; 2 exhibits better electrochemical properties than 1, with response time of 2.16 s, sensitivity of 43.10375 μA mM−1 and detection limit of 5.11 × 10−5 M. As fluorescent sensors, 1-3 can detect Cr2O72– with low concentration. Furthermore, the capacitor performances of 1-3 were explored, in which 3 shows the highest specific capacitance (409 F g−1 at 1 A g−1 with 80% of cycle efficiency after 1000 cycles). [ABSTRACT FROM AUTHOR]

Polyoxometalate-based crystalline materials as electro-active medium have exhibited excellent performances as bio/chemical sensors, particularly when synergy is reached upon combining with conductive materials. In this study, a catenane Keggin-type phosphomolybdic acid-based Ag-triazole framework and reduced graphene oxide (PMo12[6]catenane/rGO) was synthesized and employed to fabricate a modified electrode to detect the neurotransmitter dopamine (DA). Results show that PMo12[6]catenane and rGO composite modified electrode had strong catalytic activity for oxidation of DA and exhibited wide linear detection range from 1 to 90 μM with the limit of detection (LOD) of 0.890 μM and 1–44 μM with LOD 0.065 μM (S/N = 3). No interference from uric acid (UA) and ascorbic acid (AA) demonstrates that PMo12[6]catenane and rGO composite modified electrode possesses good selectivity to DA detection. The work can promote the further development of POMOFs with different structures in sensing applications. [ABSTRACT FROM AUTHOR]

A series of Lindqvist-type polyoxometalate (POM) compounds [Cat][Cp*2M5VO17] (M = Mo (1), W (2)) were obtained from Cp*2M2O5 and NaVO3 in a 1:10 molar ratio in an acidic aqueous-methanol medium ([Cat]: Bu4P+ (1a, 2a), Bu4N+ (1b, 2b), Ph4P+ (1c, 2c), and BuNC5H5+ (1d, 2d)). They have been structurally characterized by 1H and 31P NMR, FT-IR, TGA, ESI, and elemental analysis techniques which support the proposed structures. In antibacterial studies, Ph4P[Cp*2Mo5VO17] (1c) is the compound that shows the highest antimicrobial activity against both gram-positive and gram-negativebacteria. [ABSTRACT FROM AUTHOR]

Depending on the in situ ligand transformation of 3,5-di(1,2,4-triazol-1-yl)benzonitrile (DTCN) to 3,5-di(1,2,4-triazol-1-yl)benzoic acid (DTCA) under hydrothermal condition, three polyoxometalate-based copper complexes, [CuI4CuII2(OH)2(H2O)4(DTCA)4(HPMoVI10MoV2O39)] (1), [Cu4(OH)2(H2O)4(DTCA)2(SiW12O40)]·11H2O (2), and {Cu2Cl(H2O)(HDTCA)2[CrMo6(OH)6O18)]}·4H2O (3), have been isolated through changing the polyoxoanions. Introducing Keggin-type polyoxoanions [PMo12O40]3− or [SiW12O40]4− to reaction systems, both 1 and 2 display 3-D framework structures containing Cu/DTCA metal-organic belts, and a kind of poly-Keggin chain derived from [PMo12O40]3− polyoxoanions exist in 1. When the Anderson-type polyoxoanion [CrMo6(OH)6O18)]3− is utilized, a 2-D grid-like layer resulted in 3, in which the DTCA ligands are embedded, revealing that the polyoxoanions have key roles in regulating the structures of complexes. The investigations on electrochemical properties and photocatalytic activities for the degradation of organic dyes of 1–3 have been carried out. [ABSTRACT FROM AUTHOR]

A Keggin-type polyoxometalate (POM)-based supramolecular complex with the formula of [Co(H2O)3]2(ttb)2[HBW12O40]·2H2O (1) (ttb = 1,3,5-tri(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene) was synthesized via hydrothermal method and characterized by single-crystal X-ray diffraction, IR and powder X-ray diffraction analyses. In 1, [Co(H2O)3]2+ cations are connected with the adjacent ttb ligands to form a porous two-dimensional (2-D) cationic layered network, and the [HBW12O40]4− polyoxoanions are encapsulated between the layers through intermolecular interactions, generating a POM-capsulated 3-D supramolecular network. Integrating the advantage of Co2+ with [HBW12O40]4−, 1 as a heterogeneous catalyst displays a synergistically improved catalytic performance for oxidation of styrene. It can achieve almost 98% conversion of styrene in 4 h with about 99% selectivity of benzaldehyde product, which is about five times more than the catalytic activities of the single components (Co(OAc)2·4H2O or K5BW12O40). A series of comparative analyses showed that the high catalytic performance of 1 is mainly attributed to the synergistic effect of unsaturated metal sites and polyoxoanions. This work provides an approach for developing highly efficient POM-based heterogeneous catalysts toward the selective oxidation of styrene. [ABSTRACT FROM AUTHOR]

P2W16Mo2/PVA/TiO2 composite films were prepared by doping TiO2 nanoparticles (P25) into P2W16Mo2/PVA. Irradiated with UV light, composite films changed from light yellow to blue. P2W16Mo2/PVA and P2W16Mo2/PVA/TiO2 composite films (before and after UV irradiation) were characterized by IR spectroscopy, which verified that the basic structure of H6P2W16Mo2O62 and PVA were not destroyed in the composite films. The photochromism performance of P2W16Mo2/PVA and P2W16Mo2/PVA/TiO2 composite films were explored by UV–vis absorption spectra. Compared with P2W16Mo2/PVA composite films, photochromism response time of composite films doped in TiO2 was more sensitive and the UV–vis adsorption spectra absorbance increased significantly. With time, P2W16Mo2/PVA/TiO2 composite films had a circulation ability of rising-fading color. The composition of the composite film with the best photochromism performance was obtained. [ABSTRACT FROM AUTHOR]

Synthesis of catalysts with high activity for hydrogen evolution reaction (HER) has been a hot topic in electrocatalysis. In this paper, using MIL-88A(Fe) metal-organic complex, polyoxometalate (POM) and H2PtCl6 as starting materials, hierarchic and low Pt0-loading micro-rods (denoted as Pt-POMFe, i.e. Pt-PW12Fe or Pt-PMo12Fe) have been synthesized, in which the Pt0 nanoparticles can be stabilized by POM. The Pt-PW12Fe micro-rod containing [PW12O40]3- polyoxoanion component (0.30% Pt0-loading) which retains the spindle structure of its parent MIL-88A(Fe) exhibits a low overpotential of 28 mV at current density of 10 mA·cm−2 for HER that is close to the electrocatalytic effect of commercial Pt/C (ca. 20% Pt0-loading). Such high electrocatalytic reactivity is mainly caused by the synergistic effect of the three components of POM, Pt0, and Fe3O4@C. The structure effectively increases the active sites of the catalyst and improves its conductivity and stability. The Pt-POMFe catalyst extends a new family of MOF-POM functional materials and provides a new concept to the design and synthesis of highly-efficient and low-cost electrocatalyst for hydrogen production. [ABSTRACT FROM AUTHOR]

Three new Krebs-type polyoxometalate-based crystalline materials (H2en)4{[M(Hen)(H2O)]2(WO2)2(B-β-SbW9O33)2}·12H2O (M = Ni2+ in 1, M = Co2+ in 2, M = Mn2+ in 3) (en = ethylenediamine) have been synthesized via hydrothermal method and characterized by single crystal X-ray diffraction, IR spectroscopy, X-ray powder diffraction and thermogravimetric analysis. Compounds 1-3 display isomorphic structures and contain similar disubstituted Krebs-type {[M(Hen)(H2O)]2(WO2)2(B-β-SbW9O33)2}8- polyoxoanions, in which sandwich-type {(WO2)2(B-β-SbW9O33)2} subunits are linked by [M(Hen)(H2O)]3+ fragments to form two-dimensional layer structures. By employing K3[Fe(CN)6]-Na2S2O3 reaction as the redox model, the influence of metal linkers on the catalytic electron transfer properties of POMs have also been investigated. A series of control experiments demonstrated that the Co-disubstituted compound 2 had better catalytic performance for reducing K3[Fe(CN)6] into K4[Fe(CN)6] among 1-3. While Ni- or Mn-disubstituted compounds 1 and 3 only presented weak effect. Such differences in catalytic properties may arise from their different φѳ of linked heterometal atoms. The current work may provide guidance for the design of Krebs-type polyoxometalate-based heterogeneous catalysts and the exploration of catalytic redox reaction mechanism at the molecular level. [ABSTRACT FROM AUTHOR]

A high-nuclearity nickel-substituted polyoxotungstate, Na6K5.5H4.5 {[Ni8(OH)6(H2O)2](CO3)3(SiW9O34)2}·22H2O (1), has been obtained by the reaction of Na10[α-SiW9O34]·18H2O, Ni(NO3)2·6H2O and K2CO3 in aqueous solution and characterized by IR spectroscopy, single crystal X-ray diffraction, thermal gravimetric analysis and elemental analysis. Carbonate is not only used to adjust the pH of the solution, but also is a structure-stabilizing agent. The polyoxoanion {[Ni8(OH)6(H2O)2](CO3)3(SiW9O34)2}16- (1a) can be regarded as two {[Ni4(OH)3(H2O)](SiW9O34)} subunits connected by three carbonate groups, which represents the first polyanion containing an octanuclear nickel cluster based on trivacant Keggin-type polyoxotungstate {XW9} (X = heteroatom). The subunit {[Ni4(OH)3(H2O)](SiW9O34)} can be viewed as a tetranuclear nickel cluster linked to a trivacant Keggin-type polyoxotungstate {SiW9O34}. Furthermore, magnetic measurements show that 1 exhibits antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]

A {CaCo3}-containing sandwich-type polyoxometalate, Li2Na2Ca3(H2O)16{Co3(H2O)[Ca(H2O)5PW8O31](PW9O34)}·16.5H2O (1), was synthesized by using a trivacant phosphotungstate to react with Co2+ and Ca2+ by a conventional aqueous solution method. 1 was characterized by single crystal X-ray diffraction, powder X-ray diffraction, IR spectra, elemental analyses and TG analyses. Structural analysis reveals that 1 is composed of trivacant and a tetravacant phosphotungstates to trap a {Co3} cluster and a Ca2+ cation. The obtained sandwich-type polyoxoanion was further connected to form a two-dimensional expanded structure via the Ca2+ linkers. This work highlights an efficient method to simultaneously introduce both alkaline-earth and transition-metal cations into polyoxotungstates. [ABSTRACT FROM AUTHOR]

Solid phosphotungstate nanospheres PW12/CeF3:Tb3+ have been successfully synthesized using chemical precipitation method by introducing CeF3:Tb3+ nanocrystals as dopants. This material exhibits multi-emission in the photoluminescence spectrum, with peaks centered at 467, 489, 542, 585, and 622 nm, corresponding to the [PW12O40]3– polyanions and Tb3+ ions-related fluorescence, respectively. Moreover, the emission of CeF3 is disappeared, indicating the establishment of energy transfer system. It is worth pointing out that these fluorescent phenomena are rarely found in polyoxometalates-based nanomaterials. Thus, this method demonstrated in this work could provide a potential strategy to obtain multi-emissive polyoxometalates-based nanomaterials for fluorescent chemical sensors, bioimaging, or optoelectronic devices. [ABSTRACT FROM AUTHOR]

The new molybdenyl acetylacetonate Schiff base complex with mono-lacunary polyoxometalate (1) was synthesized in the reaction of [PMo11O39]7-, molybdenum acetylacetonate (MoO2(acac)2), and ethylenediamine. The catalyst was characterized by elemental analysis and various routine techniques like FT-IR, XRD, FESEM, EDX, UV–Vis, and TGA. The catalytic activities of this nanocatalyst were examined for epoxidation of linear, cyclic and phenyl-substituted olefins using tert-butyl hydroperoxide (tert-BuOOH) as oxidant. [ABSTRACT FROM AUTHOR]

By using the Keggin anion [SiMo12O40]4− as a template and bis(triazole) derivatives as organic ligands, three compounds were synthesized, [Zn2(bte)4(SiMo12O40)]·H2O (1), [Zn4(btb)8(SiMo12O40)2] (2) and [Zn2(bth)4(SiMo12O40)] (3) (bte = 1,2-bis(1,2,4-triazol-1-yl)ethane, btb = 1,2-bis(1,2,4-triazol-1-yl)butane and bth = 1,2-bis(1,2,4-triazol-1-yl)hexane). Compound 1 has a cross-shaped cycle-connecting-cycle chain, with two Keggin anions locating above and below for each cycle. By increasing the spacer length of the ligands, a 2D double-layer is formed in 2. The Keggin anions are embedded in the grids of the double-layer. Compound 3 exhibits a wave-like 2D layer with large grids. The two layers penetrate in the form of crests to crests. The anions are covered by these two penetrated layers. The Keggin anions induce distinct metal-organic subunits in 1–3 as the templates. We found that these compounds show electrocatalytic activity for ascorbic acid, bromate and nitrite. All these compounds can be used as electrochemical sensors for nitrite and show good selectivity for NO2− ions. [ABSTRACT FROM AUTHOR]

In the study, the polyoxometalate-based ionic liquid (POM-IL) was prepared. The prepared nanomaterial was immobilized onto a stainless steel wire for fabrication of the solid phase microextraction (SPME) fiber. The applicability of this coating was assessed employing a laboratory-made SPME device and gas chromatography with mass spectrometry (GC–MS) for the extraction of six triazole pesticides (penconazole, hexaconazole, diniconazole, tebuconazole, triticonazole, and difenconazole) from the headspace of aqueous samples. A series of parameters that affect the performance of microextraction, such as fiber coating, extraction time, stirring rate, ionic strength, pH, desorption temperature, and desorption time, were thoroughly investigated. In optimum conditions, the repeatability for one fiber (n = 3), expressed as relative standard deviation, was between 4.3% and 8.3% for the test compounds. The detection limits for the studied compounds were between 7 and 40 pgmL−1. [ABSTRACT FROM AUTHOR]

A new polyoxometalate (POM)-templated 3-D copper(II)-triazole framework [Cu10(trz)10(OH)6(Cl)4][H3PW12O40]·2H2O (trz = 1,2,3-triazole) has been synthesized and characterized by single crystal X-ray diffraction and other routine methods. The 3-D POM/copper(II)-triazole hybrid framework with a 1-D channel possesses a pcu topology under the template of bulk Keggin-type phosphotungstate. As a new kind of peroxidase mimetic, the new compound effectively catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2. The electrostatic interactions and hydrogen bonds/π-π stacking interactions among TMB, trz, and phosphotungstate are responsible for the enhancement of peroxidase-like activity. In addition, application for colorimetric sensing of H2O2 is also explored; the new compound exhibits a wide linear range (1–80 μM), low detection limit (0.21 μM), and fast response (2 min). [ABSTRACT FROM AUTHOR]

Halo-organic acids in aqueous solutions are widespread pollutants. An enormous number of technologies have been proposed for their elimination. In this context, reducing electron exchange columns seem to be an optimal solution for their degradation, as they do not introduce any new chemical into the solution to be purified. The electron exchange columns used in this study consist of entrapped polyoxometalates (POMs) in silica sol-gel matrices that were used as the reducing medium for the reductive de-halogenation of Br3CCO2−, Cl3CCO2−, BrCH2CO2− and ClCH2CO2−. The same matrices were also applied as catalysts for the reduction of the investigated halo-acetates by BH4−. Surprisingly, the results indicate that the mechanisms of de-halogenation of Br3CCO2−, Cl3CCO2−, BrCH2CO2− and ClCH2CO2− differ from each other. [ABSTRACT FROM AUTHOR]

A stable hamburger-like polyoxometalate (POM)-pillared coordination polymer (CP) [Ag15(trz)10][SiW12O40] (Ag15SiW12) (trz = 1,2,3-triazole) has been synthesized and characterized. Single crystal X-ray diffraction (SCXRD) analysis indicates that SiW12 polyanions are sandwiched between adjacent Ag-trz sheets with two distinct types of pores, giving a three-dimensional POM-pillared sheet framework. Inspired by the reported horseradish peroxidase (HRP) and other enzyme mimics, the peroxidase-like activity of Ag15SiW12 was investigated to catalyze oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2. Compared with other POM-involved enzyme mimics, Ag15SiW12 exhibits excellent peroxidase-like activity. Detection of H2O2 was also studied in buffer solution, and the result shows broader application range (1-100 μM), faster response time (1 min) and lower detection limit (0.27 μM), which may be ascribed to the distinct structure and maximized synergistic effect of individual components. [ABSTRACT FROM AUTHOR]

A new Strandberg-type polyoxometalate compound [Co(L)2(H2O)2]2H2[P2Mo5O23]·2H2O (1), (L = pyridine-2-carboxamide) has been synthesized and structurally characterized by elemental analysis, spectroscopic methods (IR, UV-Vis) and X-ray powder diffraction (XRD), as well as single crystal X-ray diffraction. Compound 1 consists of one [P2Mo5O23]6–, two [Co(L)2(H2O)2]2+ and two dissociative water molecules. Biological studies indicated that compound 1 exhibited effective activities against both HepG2 (human hepatocellular carcinoma) cells and HCT-116 (human colorectal cancer) cells and lower toxicity against normal HL-7702 (human normal hepatocyte) cells. A synergistic effect involving L, metal ions and P2Mo5 cluster could probably explain the improved growth-inhibiting properties. [ABSTRACT FROM AUTHOR]

A novel neodymium(III) complex containing tungstogermanate and 5-fluorouracil, K11(C4H4FN2O2)2Nd(GeW11O39)2·15H2O (FNdGeW), was synthesized and its structure was characterized by 1H NMR, IR, XRD, and TG-DSC. The results indicated that FNdGeW had Keggin structure of hetereopolyanion and structure of 5-fluorouracil. The thermal analysis showed that FNdGeW decomposed at 255.3 °C. MTT tests were performed to study the anticancer activities against SGC-7901 and HepG2 cells. The results showed that FNdGeW and FGeW possessed higher anticancer activities than 5-fluorouracil. FNdGeW exhibited the highest anticancer activities against SGC-7901 cells (IC50 = 0.79 μmol•L-1) and HepG2 cells (IC50 = 0.37 μmol•L-1). [ABSTRACT FROM AUTHOR]

Polyoxometalate (POM) cluster anions form monolayers on metal(0) nanoparticles (NPs) in water, serve as protecting ligands for binary-salt nanocrystals (such as AgCl), and as covalently attached ligands on anatase TiO2 nanocrystals. We now show that the lacunary-Keggin ion [α-AlW11O39]9− (1) binds strongly to Cd2+ in water, providing control over the growth and stability of CdS nanoparticles (NPs) that form upon addition of sulfide. When reduced by a single electron, the already highly negatively charged POM, 1 is protonated by water, and 1-protected CdS NPs were used as visible-light driven electron donors to assess whether combined reduction and protonation of 1 occurred via sequential electron- and proton-transfer steps (an ETPT mechanism), or simultaneously, via concerted proton-electron transfer (CPET). Comparison of the kinetic profiles for reduction of 1 in D2O and in H2O showed the absence of a kinetic isotopic effect (KIE), characteristic of ETPT mechanisms. [ABSTRACT FROM AUTHOR]

Two new inorganic-organic hybrids, [Co3(bpdo)6(H2O)4Cl2][SiW12O40]·H2O (Co-SiW) and [Ni3(bpdo)6(H2O)4Cl2][SiW12O40]·H2O (Ni-SiW) (bpdo = 4,4′-bis(pyridine-N-oxide)), were synthesized from the Keggin-type [SiW12O40] anion and Co(II) and Ni(II) under hydrothermal conditions, respectively, and characterized by elemental analyses, powder XRD, IR spectra, and single-crystal X-ray diffraction. The structural analysis indicates that the 1D chain is constructed from a POM-based half-cage as a secondary building block linked by bridging bpdo ligands. The zigzag chains further stack into a three-dimensional body with channels. The 3D network structure with amphiphilic cavities is shaped by electrostatic interactions through the planes, which has potential to allow molecules such as styrene and H2O2 ingress and egress. Both of the hybrids demonstrated catalytic activity for epoxidation of olefins, which was examined using styrene and aqueous hydrogen peroxide (30%) as oxidant in acetonitrile, along with Co-SiW and Ni-SiW in a heterogeneous manner at 60 °C. Moreover, the conversion of epoxidation reaction in a heterogeneous manner is close to that of homogeneous catalysis, while being conveniently recovered and steadily reused without change of catalyst structure after epoxidation reactions. [ABSTRACT FROM AUTHOR]

A new CoW11Mn/PANI/TiO2 ternary composite was synthesized with K8[Co(H2O)MnW11O39] (CoW11Mn) and PANI/TiO2 by electrostatic self-assembly. These catalysts were characterized using infrared (IR) spectroscopy, X-ray diffraction, scanning electron microscopy, ultraviolet-visible spectroscopy, and N2 adsorption-desorption. CoW11Mn/PANI/TiO2 was used to photodegradate the example contaminant, gentian violet (GV). Under the optimum photodegradation conditions, 92.63% degradation was achieved, indicating that the introduction of polyoxometalate and polyaniline greatly enhanced the photocatalytic performance of the catalyst. Moreover, CoW11Mn/PANI/TiO2 exhibits stable performance with little loss in activity after three successive runs. Thus, CoW11Mn/PANI/TiO2 ternary composite could be a promising photocatalyst in photodegradation of organic pollutants. [ABSTRACT FROM AUTHOR]

Ag-modified polyoxometalate [Na(H2O)]2[Ag(bpf)]3[PW12O40] (1) (bpf = 2,4-di(4-pyridyl)furan) was synthesized through a hydrothermal reaction. Single-crystal X-ray diffraction analysis revealed that1consists of a hybrid 3D MOF constructed from Keggin-type polyanionic [PW12O40]3-and cationic Ag-bpf units. Ligand bpf in1wasin situtransferred from 1,3-bis(4-pyridyl)propane under the higher temperature and pressure of hydrothermal conditions. Catalytic performance of1as a heterogeneous catalyst for degradation of organic dye Rhodamine B (RhB) was investigated. Experimental results showed that hybrid1was especially active to catalytically degrade RhB under room temperature and natural light. RhB-containing solution (5.0 mg·L−1) could be quickly bleached in a short time, and the high removal efficiency (97%) could be reached in a mere 30 min. The degradation mechanism of RhB was discussed. [ABSTRACT FROM PUBLISHER]

To rich the coordination polymer and polyoxometalate (POM) chemistry, two new hybrid compounds based on Keggin POMs with antifungal medicine fluconazole (Hfkz = [1-(2,4-difluorophenyl)-1,1-bis [(1H-1,2,4-triazol-1-yl)-methyl]methanol]), [Ag4(Hfkz)2][PW12O40] (AgFkzPW12) and [Ag4(Hfkz)2][SiW12O40] (AgFkzSiW12), have been successfully synthesized and structurally characterized. Moreover, to improve the photogenerated electron-hole pair separation properties, the surface of hybrid compounds was loaded by polypyrrole (PPy) through a chemical oxidation polymerization processin situfabricating hybrid nanocomposites AgFkzPW12@PPy and AgFkzSiW12@PPy. As a result, the Hfkz molecules were successfully grafted onto the surface of the Keggin polyoxoanions, and their nanocomposites exhibit better photocatalytic activity than the respective matrix compounds under the irradiation of visible light. [ABSTRACT FROM PUBLISHER]

The nature of [(C7H7N2)3(NH4)]2[Mo8O26]2·4H2O intermolecular interactions has been analysed through Hirshfeld surfaces and 2D fingerprint plots. So it is explicit that presence of amine groups and water molecules reveals that O···H/H···O intermolecular interactions are the most abundant contacts in the crystal packing. Semi-empirical calculation has been done to study the theoretical properties of this polyoxometalate compound. In this study, we have investigated several properties such as frontier molecular orbital, molecular electrostatic potential, electron density, thermodynamic properties, dipole moment, QSAR properties and local ionization potential. This work provided helpful information for the study of electronic structure and molecular properties. [ABSTRACT FROM PUBLISHER]

A new rod-like nanostructured Keggin-type amino acid-polyoxometalate hybrid material, (His)3PMo12O40 (His = histidine), was synthesized using nonionic microemulsion method. The water pools in the microemulsion system acted as nanoreactors for the reaction of histidinium hydrochloride and phosphomolybdic acid to produce nanostructured (His)3PMo12O40 hybrid material. A stoichiometric amount of histidinium ion as an organic species was substituted in the Keggin-type heteropoly acid, while its primary structure remained intact. The structural characterizations indicated the nanosized rod-like morphology of the product with the average diameter size of about 100 nm. [ABSTRACT FROM AUTHOR]

Under hydrothermal conditions two compounds based on Keggin and β-octamolybdate, respectively, [Cu2(bbtz)4(SiMo12O40)] (1) and [Cu2(bbtz)4(Mo8O26)]1/2·H2O (2) (bbtz = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene), were synthesized in one-pot and characterized by single-crystal X-ray diffraction, elemental analyses, and IR spectroscopy. In compound 1, two adjacent wave-like CuII-bbtz lines are connected by SiMo12 anions and bbtz to generate a ladder-like chain. Adjacent chains share the same CuII ions to build a three-dimensional (3-D) framework. In compound 2, the β-Mo8 anions link Cu3(bbtz)2 subunits alternately to form a one-dimensional (1-D) chain. These chains connect each other through sharing CuII ions and a 3-D network is constructed. Moreover, we studied the electrocatalytic and photocatalytic activities of these two compounds. The results indicate that 1 and 2 show good electrocatalytic performance for the reduction of nitrite and bromate; they also exhibit photocatalytic properties for degradation of MB and RhB. [ABSTRACT FROM AUTHOR]

Two new hybrid compounds with chemical formulas [Co(L1)2(H2O)2]2[SiW12O40]·6H2O (1) and [Cu2(C9H22 N)2(L2)2][SiW12O40]·2H2O (2) (L1 = 3,3′-diamino-5,5′-bis(1H-1,2,4-triazole), L2 = 1,2-bis(3-(2-pyridyl)pyrazole-1-ylmethyl)benzene, C9H22 N = tripropylamine) were prepared in a hydrothermal reaction system containing Keggin-type polyoxometalates (POMs), transition metal (TM) salts (cobalt salts and copper salts), and chelate L1/L2 ligands. X-ray structural analysis reveals that 1 and 2 possess 3-D supramolecular host frameworks with large cavities and the polyoxoanions SiW12 reside in these cavities as the guest templates. The photocatalytic activities of 1 and 2 were investigated. Both compounds show efficient catalytic activity for degradation of RhB with 1 > 2. The loading amount of the POM units and the structural features of these POM-based organic-inorganic hybrid compounds may be necessary factors that affect the activity of catalysts in the photocatalytic degradation. [ABSTRACT FROM AUTHOR]

Two new organic–inorganic hybrid compounds, [Cu(phen)(prz)]2[PMoV1MoVI7VIV2VV4O42]·4H2O (1) and [Ag2(phen)4]2[PMoV1MoVI7VIV2VV4O42] (2) (phen = 1,10-phenanthroline, prz = pyrazine), have been synthesized and characterized by IR, XPS, XRD, UV–vis, fluorescent spectra analyses, elemental analyses, X-ray diffraction analyses, TG analyses, and cyclic voltammetric measurements. Both compounds are formed by Keggin POM cores and transition metal fragments. Compound1exhibits an unprecedented 1-D chain structure constructed from [PMoV1MoVI7VIV2VV4O42]4−and [Cu(phen)(prz)]2+in the –A–B↑–C–B↓– linking mode. Compound2shows a supramolecular structure formed by [PMoV1MoVI7VIV2VV4O42]4−and [Ag2(phen)4]2+. [ABSTRACT FROM PUBLISHER]

Polyoxometalate, K6TiW11O39Sn·7H2O (TiW11Sn), was synthesized and characterized. TiW11Sn and K6ZrW11O39Sn·12H2O (ZrW11Sn) were evaluated for their photocatalytic degradation of triarylmethane (brilliant green and acid blue 9), bisazo (C.I. reactive black 5), and monoazo dyestuffs (C.I. reactive red 24, C.I. reactive red 194, and C.I. reactive orange 5) with natural sunlight in homogeneous aqueous solutions. TiW11Sn and ZrW11Sn effectively and photocatalytically decolorized the dyestuffs. The TiW11Sn- and ZrW11Sn-mediated photocatalytic degradation of the dyestuffs involved a pseudo-first-order reaction and was modeled by Langmuir–Hinshelwood-type kinetics. The observed pseudo-first-order rate constants (K/) of triarylmethane dyestuffs were generally bigger than that of the azo dyestuffs. Quantitative structure–property relationship models of theK/of the dyestuffs were developed using partial least-square regression. The cumulative variance of the dependent variable explained by the partial least-square components was > 0.753 for each optimal model. This value indicated that the model had good predictive ability and robustness. TheK/values of the dyestuffs were related to the energy of the lowest unoccupied molecular orbital, and the most positive net atomic charges on a sulfur atom of dyestuffs. The linear correlation coefficients between the predicted and experimental values were all > 0.9950. [ABSTRACT FROM AUTHOR]

The purpose of the study was to develop physically cross-linked novel pH-responsive gelatin – Wells–Dawson-type polyoxometalate (POM)-based self-assembled hydrogels using acrylic acid as a pH-responsive monomer. Cross-linking was achieved through electrostatic interactions between the cationic polymer and anionic Wells–Dawson POM [P2W15O56]12−. Ammonium persulfate and sodium hydrogen sulfite were used as initiators. The hydrogels were yellowish in color and exhibited low mechanical strength. Swelling, drug release, and pH sensitivity studies were conducted at pH 1.2 and 7.4. pH-dependent swelling and release of [P2W15O56]12−from the prepared hydrogels were observed, with a maximum at pH 7.4. The hydrogels were characterized by thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, and Fourier transform infrared spectroscopy for evaluation of the surface morphology, hydrogel confirmation, and thermal properties. The results obtained confirmed the development of a gelatin–POM-based self-assembled hydrogel. It can be concluded that as a result of successful physical cross linking, the prepared hydrogels possess desired characteristics of a drug delivery system and can hence be used for a controlled delivery of the encapsulated polyanions. . [ABSTRACT FROM AUTHOR]

By introducing three pyridyl-1H-tetrazole derivatives to Keggin–Ag-(1,10-phenanthroline) system, five new polyoxometalate-based inorganic–organic hybrid compounds with different dimensionalities and structures, [Ag3(4-ptz)2Na(phen)(HPMo12O40)]·2H2O (1), [Ag4(3-ptz)2(phen)2(HPMo12O40)] (2), [Ag4(3-ptz)2(phen)2(HVW12O40)] (3), [Ag3(3-bptzb)(phen)2(PMo12O40)] (4) and [Ag3(3-bptzb)(phen)2(VW12O40)] (5) (phen = 1,10-phenanthroline, x-ptzH = 5-(x-pyridyl)-1H-tetrazole (x = 3, 4), 3-bptzb = 1,4-bis(5-(3-pyridyl)-tetrazolyl)butane), have been synthesized under hydrothermal conditions. Compound1is a 1-D belt architecture constructed from an Ag-4-ptz metal–organic chain and two Ag–PMo12O40–Na–phen inorganic–organic chains. When 3-ptzH was introduced as secondary ligand in2and3instead of 4-ptzH, two isostructural architectures were obtained, which contain a 1-D zigzag Ag-3-ptz chain with phen ligands hanging on both sides of the chain. The Keggin anions connect adjacent Ag-3-ptz chains to construct 2-D networks. When the flexible 3-bptzb was selected, isostructural4and5with 2-D networks were obtained, which were constructed from binuclear subunits and Keggin–Ag inorganic chains. The influence of three pyridyl-1H-tetrazole derivatives as secondary ligands on the dimensionalities and architectures of1–5was discussed. The electrochemical and photocatalytic properties of the compounds were investigated. [ABSTRACT FROM PUBLISHER]

The reaction of polyoxometalate (NH4)6[Mo7O24], transition-metal ions (Cu2+or Ag+), and a bridging ligand (bbtx) in the hydrothermal environment led to two hybrid coordination polymers, [Cu(bbtx)3][Mo6O19] (1) and [Ag2(bbtx)2][Mo6O19] (2). Luminescent measurements suggest that1mainly exhibits luminescent emission of bbtx, but2displays strong emission bands ascribed to the ligand-to-metal charge transfer. Compound2also shows reversible thermochromic luminescence from 300 K–77 K–300 K. Introduction of [Mo6O19]2−into the Ag-bbtx network can lead to luminescent quench of2under irradiation of 300 W Xe light, due to reduction of Ag(I) into Ag(0) with breaking of Ag–N bonds of2. The relevant mechanism was investigated by Powder X-ray diffraction and X-ray photoelectron spectrum , and the irradiated2was used as a catalyst for reduction of p-nitrophenol with good catalytic activity. [ABSTRACT FROM AUTHOR]

The electronic structures, absorption spectra and photovoltaic (PV) performance of four dyes based on triphenylamine and polyoxometalate (POM) organic–inorganic hybrids for p-type dye-sensitised solar cells have been discussed by density functional theory (DFT) and time-dependent DFT calculations. In the four designed dyes, the triarylamine and carbazole take the role of the electron donor and the POMs act as the electron acceptor. It was found that introduction of electron donating groups (diphenylamine group and carbazole) into the triarylamine unit enabled better PV performance. This work is expected to be helpful for designing triarylamine–POM hybrid dyes with target properties. [ABSTRACT FROM AUTHOR]

Two organic–inorganic composite vanadoborates Na2(Hen)4[B18V12O60]·16H2O (1) (en = ethylenediamine) and (H2en)6[B18V12O60]2·2tepa·11H2O (2) (tepa = tetraethylenepentamine) have been hydrothermally synthesized and characterized by elemental analyses, inductively coupled plasma atomic emission spectrometry (ICP-AES) analyses, IR spectra, and X-ray crystallography. Single-crystal structural analyses show that1exhibits a 2-D polyoxovanadium borate sheet architecture with a four-connected topology established by [B18V12O60]6−units via Na+bridges whereas the molecular unit of2consists of two discrete [B18V12O60]6−clusters, six diprotonated [H2en]2+cations, two tepa molecules, and 11 lattice water molecules. [ABSTRACT FROM AUTHOR]

Self-assemble of aqueous solution of the Cu2+/molybdate/glyc-ine system results in {[NaCu6(Gly)8(H2O)2][Mo8O26Cu(Gly)2]2}n·n{NaCu6(Gly)8(H2O)2}·n{Mo8O26[Cu(Gly)(GlyH)(H2O)2]2} 15nH2O1, which exhibits the 0-D + 1-D supramolecular framework and in which the copper atoms show three kinds of coordination models: (1) in quadrilateral geometry, (2) in square-pyramidal geometry, and (3) in distorted octahedral geometry. The space group of the compound is P–1, with the lattice parameters: α = 89.036(5)°, β = 89.384(4)°, γ = 88.337(5) °, a = 12.559(4) Å, b = 14.441 (4)Å, c = 23.063(6) Å, and Z = 1. [ABSTRACT FROM AUTHOR]

Two new isopolymolybdate-based metal–organic complexes, [Cu2(2-ptz)2(Mo4O14)0.5] (1) and [Cu3(OH)2(3-ptz)4(γ-H4Mo8O26)(H2O)4]·10H2O (2) (2-ptzH = 5-(2-pyridyl)-1H-tetrazole, 3-ptzH = 5-(3-pyridyl)-1H-tetrazole), constructed from isomeric ligands with different N-donor sites were synthesized under hydrothermal conditions. In1, each [Mo4O14]4−cluster connected with six neighboring [Mo4O14]4−clusters through six binuclear [Cu2(2-ptz)2]2+subunits to yield a 2-D layer. In2, bidentate inorganic [Mo8O26]4−anions link the trinuclear [Cu3(OH)2(3-ptz)4] clusters to construct a 1-D chain. Adjacent chains connect through Mo–N bonds between the [Mo8O26]4−anions and pyridyl groups from the trinuclear clusters to form a 2-D layer. The effect of the N-donor sites of the rigid isomeric ligands on the structures of1and2was discussed. The electrochemical properties and photocatalytic activities of1and2have also been studied. [ABSTRACT FROM PUBLISHER]

A copper complex modified Mo-oxide hybrid network stabilized by Keggin polyoxoanion, [{Cu(bpy)2}{Mo12O34(bpy)12}][PMo12O40]2(bpy = 2,2ʹ is-bipyridine) (1) has been synthesized via self-assembly of simple starting materials. In1, six [MoO4(bpy)] complexes connect in two different corner-sharing modes to form triangles and linear trimer units, which interconnect alternately to form zigzag chains. {Cu(bpy)2} segments connect the chains into 2-D layers, which are further joined into 3-D supramolecular networks with 1-D channels. The {PMo12PO40} as guest molecules are incorporated into the channels. Compound1exhibits bifunctional electrocatalytic behavior for oxidation of ascorbic acid and reduction of H2O2, as well as high-efficient degradation ability for typical dye methylene blue under UV light. [ABSTRACT FROM PUBLISHER]

A pure inorganic 2-D framework based on paradodecatungstate polyanions and [Mn(H2O)n]2+(n = 2, 3) ions, Na10{[Mn(H2O)3]2[H2W12O42]}{[Mn(H2O)3]2[Mn(H2O)4][H2W12O42]}·56H2O (1), has been synthesized and characterized by IR spectra, UV–vis spectra, thermogravimetric analysis (TGA), single-crystal X-ray diffraction, and magnetic measurements. Single-crystal X-ray diffraction analysis indicates that [H2W12O42]10−in1is a tetradentate ligand and coordinates to four [(Mn(H2O)3]2+cations through terminal oxygens to form manganese doubly bridged 1-D chains, which are further linked through [Mn(H2O)4]2+ions into a 2-D layer. The catalytic activities of1are tested in the selective oxidation of benzyl alcohol to benzaldehyde with 30% aqueous H2O2as oxidant in toluene, exhibiting 90% conversion and 93% selectivity. Magnetic studies indicate that weak antiferromagnetic couplings exist between the Mn(II) ions in1. The pure inorganic–inorganic hybrid represents an extended structure constructed from paradodecatungstate and transition metal ions and shows definite catalytic activities on the probe reaction of benzyl alcohol oxidation to benzaldehyde with H2O2. [ABSTRACT FROM AUTHOR]

A new organic–inorganic hybrid silicotungstate [Cu2(phen)2Cl(H2O)(OH)]2[α-SiW12O40]·8 H2O (1) (phen = 1,10-phenanthroline) with supporting dinuclear copper complexes has been hydrothermally synthesized and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction. The molecular unit of 1 consists of two pendant coordination cations [Cu2(phen)2Cl(H2O)(OH)]2+and one saturated Keggin-type silicotungstate polyoxoanion [α-SiW12O40]4−and eight lattice water molecules. The most intriguing feature is that each bi-copper cation [Cu2(phen)2(μ2-Cl)(H2O)(OH)]2+is constructed from two [Cu(phen)]2+cations linked by one μ2-Cl and one hydroxyl bridges. Magnetic measurements indicate that 1 demonstrates the ferromagnetic exchange interactions within CuIIcenters. [ABSTRACT FROM PUBLISHER]

In the present work, the synthesis and structural characterization of two new polyoxovanadoborate (BVO) frameworks, based on the [V12B18O60H6]10−polyanion, are reported, K(H3O)(enH2)4[V12B18O60H6]·9.60H2O (1) and Li8(NH4)2[V12B18O60H6]·8.02H2O (2). Both compounds are obtained in a mixed valence ratio of 10VIV/2VV. Framework1is characterized by potassium ions coordinated by the BVO cluster and ethylenediammonium and hydronium ions as charge-compensating agents. In framework2, the BVO clusters are coordinating lithium ions and the charge is compensated by ammonium ions. Using the SHAPE 2.1 program, it was possible to calculate the best geometry for the existing lithium and potassium ions. For2, the lithium ions are five-coordinate, best described by a square pyramid (SPY-5), while the coordination sphere around the potassium ions in1are six-coordinate. For1, the coordination sphere of the existing potassium ions in the framework can be described as trigonal prism (TPR-6). Calculations were also done for a previously reported cluster [Na10[(H2O)V12B18O60H6]·18H2O] (3), in which the sodium ions are six-coordinate but in two different geometries, these being octahedral and TPR-6. The influence of the interactions of the alkali ions with the [V12B18O60H6]10−polyanion, on the vanadate and borate absorption bands observed in the infrared spectra, is discussed. [ABSTRACT FROM PUBLISHER]