Anderson Structure Research Articles

Conversion Reaction of Polyoxometalates from Anderson Structure to Keggin Structure

Conversion Reaction of Polyoxometalates from Anderson Structure to Keggin Structure

Novel colloidal materials from functionalized polyoxometalates

Polyoxometalate (POM)-based colloidal materials were prepared for the first time from the organo-functionalized Anderson structure polyoxometalate species [NaV IV 6 O 6 {(OCH 2 CH 2 ) 2 N(CH 2 CH 2 OH)} 6 ]Cl·H 2 O and the mixed-addenda Keggin structure polyoxometalate, K 4 (PVW 11 O 40 ). • Two POM-based colloidal materials prepared • Isolable and redistributable • Inherently thin-film forming

Mechanochemical synthesis of nanocrystalline nickel-molybdenum compounds and their morphology and application in catalysis: III. Catalytic properties of massive Ni-Mo sulfide catalysts synthesized using mechanochemical activation

The precursors of massive Ni-Mo catalysts for hydrotreating processes, which were synthesized by the mechanochemical activation of a mixture of nickel hydroxocarbonate NiCO3·2Ni(OH)2·nH2O and ammonium paramolybdate (NH4)6Mo7O24 · 4H2O, were sulfidized. Their structure was studied by X-ray diffraction analysis and high-resolution electron microscopy. It was found that MoS2 packets, which are characterized by the presence of structural defects and geometric curvature, are the constituents of the massive catalysts. The catalyst also includes a phase of Ni3S2 and regions containing a complex Ni-Mo-S phase. The catalytic tests of the synthesized catalysts in the model reactions of 1-methylnaphthalene and dibenzothiophene conversions showed that the catalyst whose precursor was a heteropoly compound with the Anderson structure after the stage of mechanochemical activation exhibited the highest activity.

Mechanochemical synthesis of nanocrystalline nickel-molybdenum compounds and their morphology and application in catalysis: II. Effect of mechanochemical activation parameters—process power density and exposure time—on the composition and structure of nickel-molybdenum compounds

The effect of mechanochemical activation parameters-process power density and the time of treatment of a mixture of nickel hydroxocarbonate NiCO3 · 2Ni(OH)2 · nH2O and ammonium paramolybdate (NH4)6Mo7O24 · 4H2O -on the phase composition, specific surface area, and morphology of mechanically activated products at different Ni: Mo atomic ratios was studied. It was found that, at a mechanochemical activation process power density of 6.2 W/g, layered transition metal molybdates (LTM compounds) with different amounts of crystal water were the constituents of the products, whereas the products mechanically activated at a power density of 28.0 W/g contained a mixture of LTM compounds and heteropoly compounds with the Anderson structure regardless of activation time.

On the effect of a variation of the force field, spatial boundary condition and size of the QM region in QM/MM MD simulations

During the past years, the use of combined quantum-classical, QM/MM, methods for the study of complex biomolecular processes, such as enzymatic reactions and photocycles, has increased considerably. The quality of the results obtained from QM/MM calculations is largely dependent on five aspects to be considered when setting up a molecular model: the QM Hamiltonian, the MM Hamiltonian or force field, the boundary and coupling between the QM and MM regions, the size of the QM region and the boundary condition for the MM region. In this study, we systematically investigate the influence of a variation of the molecular mechanics force field and the size of the QM region in QM/MM MD simulations on properties of the photoactive part of the blue light photoreceptor protein AppA. For comparison, we additionally performed classical MD simulations and studied the effect of a variation of the type of spatial boundary condition. The classical boundary conditions and the force field used in a QM/MM MD simulation are shown to have non-neglegible effects upon the structural and energetic properties of the protein which makes it advisable to minimize computational artifacts in QM/MM MD simulations by application of periodic boundary conditions and a thermodynamically calibrated force field. A comparison of the structural and energetic properties of MD simulations starting from two alternative, different X-ray structures for the blue light utilizing flavin protein in its dark state indicates a slight preference of the two force fields used for the so-called Anderson structure over the Jung structure.

ChemInform Abstract: Insertion‐Release of Guest Species and Ionic Conduction in Polyoxometalate Solids with a Layer‐Like Anderson Structure.

AbstractCompounds (IV) and (VII) are isomorphous and exhibit a layer‐like Anderson type structure, consisting of [SbW6O24]7‐‐containing layers and interstitial Na+, K+, NO3‐ or Cl‐, and water O atoms.

Insertion-release of guest species and ionic conduction in polyoxometalate solids with a layer-like Anderson structure

The precipitation of Na + and K + mixed salts of Anderson type [SbW 6O 24] 7− by addition of excess of NaNO 3 and NaCl yielded polycrystalline powders of Na 2.5K 5.3[SbW 6O 24](NO 3) 0.8·12H 2O ( 1) and Na 2K 5.35[SbW 6O 24]Cl 0.35·12H 2O ( 2), respectively. The two compounds are isomorphous and exhibit a layer-like Anderson (LLA) type structure, which consists of [SbW 6O 24] 7−-containing layers and interstitial Na +, K +, NO 3 − or Cl −, and water O atoms. Recrystallization of 1 and 2 from hot water yielded Na 2K 5.4[SbW 6O 24](NO 3) 0.4·12H 2O ( 1-recry) and Na 2K 5.25[SbW 6O 24]Cl 0.25·12H 2O ( 2-recry) as a result of partial release of NO 3 − and Cl − (and Na + and K + for charge compensation). Dehydration of 1 and 2 at 400 and 500 °C ( 1-dehyd400 and 2-dehyd500) caused a shrinkage of lattice, but their the LLA structures retained. Simulation of X-ray diffraction (XRD) patterns for the dehydrated forms allowed to presume that the each [SbW 6O 24] 7− anion had been 30°-rotated within its molecular plane in order to avoid intermolecular repulsion. A compressed powder of 1-dehyd400 exhibited fast alkaline-ion conduction with a bulk conductivity of 1.2×10 −2 Ω −1 cm −1 at 400 °C. The hosting of a sufficient amount of NO 3 − together with Na + for charge compensation into the lattice is crucial for high conduction.

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New advanced inorganic composite materials were prepared by combination of the polycation [AlO4Al12(OH)24(H2O)12]7+ with heteropolyoxomolybdates of Anderson type structure with formula: [XMo6O24H6]3- where X=Al(III), Co(III), and Cr(III). The synthesis of these materials is performed by direct mixture of the isopolycation and heteropolyanions in a pH controlled aqueous solution. These new materials were characterized by X-ray powder diffraction (XRD), 27Al nuclear magnetic resonance (NMR); vibrational (FT-IR and Raman Microprobe) and UV–visible diffuse reflectance (UV–vis-DR) spectroscopies and their stability was studied by thermal analysis (TG-DTA). The NMR and Raman spectroscopies are useful to characterize these materials and to demonstrate that the Anderson structure in the composite lattice is preserved. Likewise, XRD, Raman microprobe and UV–vis-DR spectroscopic techniques achieve the further characterization of thermal residues or intermediates. All results allow us to suggest that the evolution of properties depends on the heteroatom nature in the Anderson structural units of these new materials.

Synthesis and Crystal Structure of the Palladium(IV) Polyoxomolybdate, K0.75Na3.75[PdMo6O24H3.5]·17H2O

AbstractThe first example of a heteropolyoxomolybdate containing palladium(IV) was isolated and characterized by X‐ray crystallography. The palladium(IV) hexamolybdate, K0.75Na3.75[PdMo6O24H3.5]·17H2O, was isolated from an aqueous solution at pH 4.5 in the space group P\bar{1}, a 10.790(2), b 12.244(3), c 14.086(3) Å, α 113.77(1), β 90.41(1),γ 107.86(1)°, and the structure was determined using X‐ray diffraction methods, refining to a residual of 0.0301 for 5334 reflections. A formal “[PdMo6O24H3]5–” subunit exhibits the basic Anderson structure, with two [PdMo6O24H3]5– cluster anions in the structure bridged by a hydrogen atom (formally an H+) situated on a center of symmetry to give a “[Pd2Mo12O48H7]9–” dimeric anion. The palladium(IV) atom occupies a slightly distorted octahedral environment, with Pd–O distances ranging from 1.968 to 2.009 Å.

Methylated molybdoplatinate—its unexpected ability to absorb methanol

Methylated molybdoplatinate of the Anderson structure was obtained as a tetra-n-butylammonium (TBA) salt by reacting MoO(3), H(2)Pt(OH)(6), and aqueous TBAOH in a 6 : 1 : 4 ratio, which absorbed huge amounts of MeOH, more than three times as much as its own weight.

A new organic‐inorganic molybdenum arsenate complex based on [(CuO6)(As3O3)2Mo6O18]4‐ cluster as secondary building units

AbstractA new molybdenum arsenate, [Cu(imi)2]2[(CuO6)(As3O3)2Mo6O18][Cu(imi)2]2 (1) (imi = C3N2H4), has been synthesized under mild hydrothermal conditions, and characterized by elemental analysis, IR, thermogravimetric analyses, and single‐crystal X‐ray diffraction analysis. The polyanion framework derives from the Anderson structure in which the central octahedron is filled up by a copper (II), and is capped on both sides by two cyclic As3O6 groups. The countercations contain bisupported [Cu(imi)2]+ complex cations and two free [Cu(imi)2]+ complex cations. The electrochemical behavior of 1‐modified carbon paste electrode (1‐CPE) has been studied in detail. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Use of (NH4)4[Ni(OH)6Mo6O18]·nH2O heteropoly compound in fabrication of sulfide catalysts for hydropurification of diesel fractions

NiMo(S)/γ-Al2O3 hydropurification catalysts were synthesized using as a precursor the active sulfide phase of a heteropoly compound with Anderson structure, ammonium 6-molybdonickelate, and, for comparison, ammonium paramolybdate. The heteropoly compound synthesized was identified using X-ray phase analysis and IR spectroscopy and its thermal stability was analyzed with DTA. The hydrodesulfurizing and hydrogenating activity of catalysts synthesized from ammonium 6-molybdonickelate was examined in hydropurification of two diesel fractions with different contents of polycyclic aromatic hydrocarbons and close contents of sulfur.

Trisodium bis{1-[iminio(morpholino)methyl]guanidinium} bis[hexahydrogenhexamolybdoaluminate(III)] chloride icosahydrate

In the title compound, Na3(C6H15N5O)2[Al(OH)6Mo6O18]2Cl·20H2O, the [Al(OH)6Mo6O18]3− polyoxo­anion has a B-type Anderson structure exhibiting approximate D 3d symmetry. There are two types of sodium cations: the Na+ cations of type I have a distorted octa­hedral coordination geometry formed by six O atoms and are statistically distributed over two positions with equal occupancies, while the coordination polyhedra of the two Na+ cations of type II share one Cl anion located on an inversion center. The latter fragment, containing a Cl anion and two sodium cations, links two polyoxoanions into centrosymmetric blocks. The diprotonated 1-[imino­(morpholino)meth­yl]guanidinium cations and uncordinated water mol­ecules contribute to extensive N—H⋯O and O—H⋯O hydrogen bonding, resulting in the formation a three-dimensional supra­molecular structure.

Synthesis and Characterization of Cu(II) Substituted Hexa Tungstate and Molybdate of the Anderson Type Anion [Xn+M6O24]-(12-n)

Sodium salts of copper substituted heteropoly compounds having molecular formula Na10[CuIIWVI6O24].22H2O(1) and Na10[CuIIMoVI6O24]. 19H2O(2) analogous to the Anderson type anion [Xn+M6O24]─(12-n)were synthesized according to the literature method. Compound(1) was synthesized from aqueous acidic solution containing sodium tungstate and copper chloride and compound(2) from sodium molybdate and copper chloride solution. The elemental analyses show 1:6 atomic ratio of the heteroatom to the addenda in both the compounds. The IR spectra for both the compounds are in good agreement with the reported formulae. A small deviation in IR spectra are observed than that established for Keggin anions. CuO6acts as hetero group which replaces MO6(M=W or Mo) from the Anderson structure. The thermal analyses of the compounds show the loss of the peripheral water molecules. The molecular weight of the compound (1) and (2) have been found as 2212.5 and 1600.5 respectively.

Synthesis and spectroscopic 27Al NMR and Raman characterization of new materials based on the assembly of [formula omitted] isopolycation and Co–Cr and [formula omitted] Anderson heteropolyanions

New advanced inorganic composite materials were prepared by combination of the polycation [ AlO 4 Al 12 ( OH ) 24 ( H 2 O ) 12 ] 7 + with heteropolyoxomolybdates of Anderson type structure with formula: [ XMo 6 O 24 H 6 ] 3 - where X = Al ( III ) , Co(III), and Cr(III). The synthesis of these materials is performed by direct mixture of the isopolycation and heteropolyanions in a pH controlled aqueous solution. These new materials were characterized by X-ray powder diffraction (XRD), 27Al nuclear magnetic resonance (NMR); vibrational (FT-IR and Raman Microprobe) and UV–visible diffuse reflectance (UV–vis-DR) spectroscopies and their stability was studied by thermal analysis (TG-DTA). The NMR and Raman spectroscopies are useful to characterize these materials and to demonstrate that the Anderson structure in the composite lattice is preserved. Likewise, XRD, Raman microprobe and UV–vis-DR spectroscopic techniques achieve the further characterization of thermal residues or intermediates. All results allow us to suggest that the evolution of properties depends on the heteroatom nature in the Anderson structural units of these new materials.

Evidence and Characterization of a New Decamolybdocobaltate Cobalt Salt: An Efficient Precursor for Hydrotreatment Catalyst Preparation

Heteropolyanions (HPAs) based on molybdenum and cobalt could be used as an alternative to the conventional ammonium heptamolybdate and cobalt nitrate precursors for the preparation of Co−Mo/Al2O3 hydrotreating catalysts. With this objective in mind, a cobalt salt of decamolybdocobaltate anion has been synthesized. This salt allows us to prepare catalyst with a Co/Mo atomic ratio of 0.5 corresponding to the optimum value encountered with classical catalyst preparation. The crystal structure refinement has been performed and reveals the formation of a new heteropolyoxomolybdate related to the well-known Anderson structure. Its structural, spectroscopic, and thermal properties have been investigated by physical techniques such as thermogravimetric analysis mass spectroscopy, X-ray diffraction, X-ray absorption spectroscopy, and vibrational spectroscopy. With the use of this new HPA precursor, initial catalytic results show a significant improvement of hydrodesulfurization catalytic performance.

In vitro inhibitory effect of polyoxometalates on human tumor cells

H7[NiV13O38] was synthesized from K7[NiV13O38] using an ion exchange method. Then Pr2H[NiV13O38] was obtained by double decomposition of H7[NiV13O38] with Pr2(CO3)3. The actual amount of praseodymium measured by elemental analysis coincides with the designed amount of praseodymium in Pr2H[NiV13O38]. The i.r. spectra suggested that the [NiV13O38]7− anion did not collapse after the ion exchange and double decomposition. The 51V n.m.r. spectrum of Pr2H[NiV13O38] showed four peaks and their ratio of the relative intensity was 4:4:4:1. This result agrees with the chemical environment of V atoms in the [NiV13O38]7− anion. In vitro antitumor activities of polyoxometalates on several human tumor cells have been investigated using the MTT method. Pr2H[NiV13O38] is the most effective polyoxometalate tested in this study for inhibiting KB cell. Pr2H[NiV13O38] also showed remarkable inhibitory effect on some other tumor cells: HCT, Bel, B16, BCAP and ESCL cells. These results indicate that Pr2H[NiV13O38] is a potent broad spectrum antitumor agent. The structure type of polyoxometalates greatly influences their antitumor activity: the order of structure type for inhibiting KB cell is: [NiV13O38]7− > [Mo␣7O24]6− > Anderson structure ≫ Keggin structure ≫ Dawson structure. Moreover, the nature of the polyatom in the polyoxometalates also greatly influences their antitumor activity: the polyatom order for inhibiting KB cell is: V > Mo ≫ W. On the other hand, the nature of the counter cation and the heteroatom in the polyoxometalates exerted a relatively small influence on the inhibitory effect against the KB cell, although the praseodymium salt of [NiV13O38]7− showed a higher antitumor activity than its potassium salt.

Preparation and Characterization of 6‐Molybdocobaltate and 6‐Molybdoaluminate Cobalt Salts. Evidence of a New Heteropolymolybdate Structure.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Preparation and characterization of 6-molybdocobaltate and 6-molybdoaluminate cobalt salts. Evidence of a new heteropolymolybdate structure.

Molybdenum and cobalt based heteropolyanions (HPAs) could be used as an alternative to the conventional ammonium heptamolybdate and cobalt nitrate starting materials for friendly environmental preparation of Co-Mo/Al2O3 hydrotreating catalysts. In this aim, cobalt salts of molybdocobaltate and molydboaluminate Anderson HPAs have been synthesized and characterized by TGA, XRD, XAS, and vibrational spectroscopies. The crystal structure refinement provided evidence for the formation of a new heteropolyoxomolybdate derived from the well-known Anderson structure.

A novel cationic heteropolyoxovanadium(IV) cluster functionalized with organic ligands: synthesis and characterization of the fully reduced species [Mn(II)V(IV)6O6[(OCH2CH2)2N(CH2CH2OH)]6]Cl2.

The solvothermal reaction of (HOCH2CH2)3N with [(n-C4H9)4N]3[H3V10O28] and MnCl2 x 4H2O in CH3CN and CH3OH yields a novel cationic heteropolyoxovanadium(IV) cluster, [Mn(II)V(IV)6O6[(OCH2CH2)2N(CH2CH2OH)]6]2+, containing a fully reduced new cyclic [MnV6N6O18] core with the Anderson structure.