Sulfates of the refractory metals: crystal structure and thermal behavior of Nb2O2(SO4)3, MoO2(SO4), WO(SO4)2, and two modifications of Re2O5(SO4)2

The sulfates Nb(2)O(2)(SO(4))(3), MoO(2)(SO(4)), WO(SO(4))(2,) and two modifications of Re(2)O(5)(SO(4))(2) have been synthesized by the solvothermal reaction of NbCl(5), WOCl(4), Re(2)O(7)(H(2)O)(2), and MoO(3) with sulfuric acid/SO(3) mixtures at temperatures between 200 and 300 °C. Besides the X-ray crystal structure determination of all compounds, the thermal behavior was investigated using thermogravimetric studies. WO(SO(4))(2) (monoclinic, P2(1)/n, a = 7.453(1) ?, b = 11.8232(8) ?, c = 7.881(1) ?, β = 107.92(2)°, V = 660.7(1) ?(3), Z = 4) and both modifications of Re(2)O(5)(SO(4))(2) (I: orthorhombic, Pba2, a = 9.649(1) ?, b = 8.4260(8) ?, c = 5.9075(7) ?, V = 480.27(9) ?(3), Z = 2; II: orthorhombic, Pbcm, a = 7.1544(3) ?, b = 7.1619(3) ?, c = 16.8551(7) ?, V = 863.64(6) ?(3), Z = 4) are the first structurally characterized examples of tungsten and rhenium oxide sulfates. Their crystal structure contains layers of sulfate connected [W═O] moieties or [Re(2)O(5)] units, respectively. The cohesion between layers is realized through weak M-O contacts (343-380 pm). Nb(2)O(2)(SO(4))(3) (orthorhombic, Pna2(1), a = 9.9589(7) ?, b = 11.7983(7) ?, c = 8.6065(5) ?, V = 1011.3(1) ?(3), Z = 4) represents a new sulfate-richer niobium oxide sulfate. The crystal structure contains a three-dimensional network of sulfate connected [Nb═O] moieties. In MoO(2)(SO(4)) (monoclinic, I2/a, a = 8.5922(6) ?, b = 12.2951(6) ?, c = 25.671(2) ?, β = 94.567(9)°, V = 2703.4(3) ?(3), Z = 24) [MoO(2)] units are connected through sulfate ions to a three-dimensional network, which is pervaded by channels along [100] accommodating the terminal oxide ligands. In all compounds except WO(SO(4))(2), the metal ions are octahedrally coordinated by monodentate sulfate ions and oxide ligands forming short M═O bonds. In WO(SO(4))(2), the oxide ligand and two monodentate and two bidentate sulfate ions build a pentagonal bipyramid around W. The thermal stability of the sulfates decreases in the order Nb > Mo > W > Re; the residues formed during the decomposition are the corresponding oxides.     

Oxygen/sulfur substitution reactions of tetraoxometalates effected by electrophilic carbon and silicon reagents

Reactions of [MO(4)](2)(-) (M = Mo, W) with certain carbon and silicon electrophiles were investigated in acetonitrile in order to produce species of potential utility in the synthesis of analogues of the sites in the xanthine oxidoreductase enzyme family. Silylation of [MoO(4)](2)(-) affords [MoO(3)(OSiPh(3))](1)(-), which with Ph(3)SiSH is converted to [MoO(2)S(OSiPh(3))](1)(-). Reaction with (Ph(3)C)(PF(6))/HS(-) yields the tetrahedral monosulfido species [MO(3)S](2)(-), previously obtained only from the aqueous system [MO(4)](2)(-)/H(2)S. Dithiolene chelate rings are readily introduced upon reaction with 1,2-C(6)H(4)(SSiMe(3))(2), leading to the square pyramidal trioxo complexes [MO(3)(bdt)](2)(-), a previously unknown dithiolene molecular type. Further ring insertion occurs upon reaction of [WO(3)(bdt)](2)(-) with 1,2-C(6)H(4)(SSiMe(3))(2), giving [WO(2)(bdt)(2)](2)(-). Related reactions occur with [ReO(4)](1)(-). Treatment with 1 equiv of (Me(3)Si)(2)S produces [ReO(3)S](1)(-); with 3 equiv of 1,2-C(6)H(4)(SSiMe(3))(2), [ReO(bdt)(2)](1)(-) is obtained with concomitant Re(VII) --> Re(V) reduction. X-ray structures are reported for [MO(3)S](z)(-) (M = Mo, W, z = 2; M = Re, z = 1), [MO(3)(bdt)](2)(-), and [WO(2)(OSiPh(3))(bdt)](1)(-), a silylation product of [WO(3)(bdt)](2)(-). [MoO(3)(bdt)](2)(-) is related to the site of inactive sulfite oxidase, and [WO(2)(OSiPh(3))(bdt)](1)(-) should closely approximate the metric features of the [(dithiolene)MoO(2)(OH)] site in inactive aldehyde/xanthine oxidoreductase. This work provides convenient syntheses of known and new derivatives of tetraoxometalates, among which is entry to a unique class of oxo-monodithiolene complexes.     

New chloro,mu-oxo,and alkyl derivatives of dioxomolybdenum(VI) and -tungsten(VI) complexes chelated with N(2)O tridentate ligands: synthesis and catalytic activities toward olefin epoxidation

A new series of cis-dioxomolybdenum(VI) complexes MoO(2)(L(n))Cl (n = 1-5) were prepared by the reaction of MoO(2)Cl(2)(DME) (DME = 1,2-dimethoxyethane) with 2-N-(2-pyridylmethyl)aminophenol (HL(1)) or its N-alkyl derivatives (HL(n)) (n = 2-5) in the presence of triethylamine. The new mu-oxo dimolybdenum compounds [MoO(2)(L(n))](2)O (n = 1, 4, 5, 7) were also prepared by treating the corresponding ligand HL(n) with MoO(2)(acac)(2) (acac = acetylacetonate) in warm methanolic solutions or (NH(4))(6)[Mo(7)O(24)].4H(2)O in the presence of dilute HCl. Treatment of MoO(2)(L(1))Cl or [MoO(2)(L(1))](2)O with the Grignard reagent Me(3)SiCH(2)MgCl gave the alkyl compound MoO(2)(L(1))(CH(2)SiMe(3)), which represents the first example of dioxomolybdenum(VI) alkyl complex supported by a N(2)O-type ancillary ligand. The analogous chloro and mu-oxo tungsten derivatives WO(2)(L(n))Cl (n = 6, 7) and [WO(2)(L(n))](2)O (n = 1, 4, 6, 7) were prepared by the reaction of WO(2)Cl(2)(DME) with HL(n) in the presence of triethylamine. Similar to their molybdenum analogues, the tungsten alkyl complexes WO(2)(L(n))(R) (n = 6, 7; R = Me, Et, CH(2)SiMe(3), C(6)H(4)(t)Bu-4) were synthesized by treating WO(2)(L(n))Cl or [WO(2)(L(n))](2)O (n = 6, 7) with the appropriate Grignard reagents. The catalytic properties of selected dioxo-Mo(VI) and -W(VI) chloro and mu-oxo complexes toward epoxidation of styrene by tert-butyl hydroperoxide (TBHP) were also investigated.     

Acidity of mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2 materials: a combined solid-state NMR and theoretical calculation study

The acidity of mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2 materials was studied in detail by multinuclear solid-state NMR techniques as well as DFT quantum chemical calculations. The 1H MAS NMR experiments clearly revealed the presence of two different types of strong Br?nsted acid sites on both MoO(x)/ZrO2 and WO(x)/ZrO2 mesoporous materials, which were able to prontonate adsorbed pyrine-d5 (resulting in 1H NMR signals at chemical shifts in the range 16-19 ppm) as well as adsorbed trimethylphosphine (giving rise to 31P NMR signal at ca. 0 ppm). The 13C NMR of adsorbed 2-(13)C-acetone indicated that the average Br?nsted acid strength of the two mesoporous materials was stronger than that of zeolite HZSM-5 but still weaker than that of 100% H2SO4, which was in good agreement with theoretical predictions. The quantum chemical calculations revealed the detailed structures of the two distinct types of Br?nsted acid sites formed on the mesoporous MoO(x)/ZrO2 and WO(x)/ZrO2. The existence of both monomer and oligomer Mo (or W) species containing a Mo-OH-Zr (or W-OH-Zr) bridging OH group was confirmed with the former having an acid strength close to zeolite HZSM-5, with the latter having an acid strength similar to sulfated zirconia. On the basis of our NMR experimental and theoretical calculation results, a possible mechanism was proposed for the formation of acid sites on these mesoporous materials.     

New luminescent solids in the Ln-W(Mo)-Te-O-(Cl) systems

Solid-state reactions of lanthanide(III) oxide (and/or lanthanide(III) oxychloride), MoO3 (or WO3), and TeO2 at high temperature lead to eight new luminescent compounds with four different types of structures, namely, Ln2(MoO4)(Te4O10) (Ln = Pr, Nd), La2(WO4)(Te3O7)2, Nd2W2Te2O13, and Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W). The structures of Ln2(MoO4)(Te4O10) (Ln = Pr, Nd) feature a 3D network in which the MoO4 tetrahedra serve as bridges between two lanthanide(III) tellurite layers. La2(WO4)(Te3O7)2 features a triple-layer structure built of a [La2WO4]4+ layer sandwiched between two Te3O72- anionic layers. The structure of Nd2W2Te2O13 is a 3D network in which the W2O108- dimers were inserted in the large tunnels of the neodymium(III) tellurites. The structures of Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W) feature a 3D network structure built of lanthanide(III) ions interconnected by bridging TeO32-, Te5O136-, and Cl- anions with the MO4 (M = Mo, W) tetrahedra capping on both sides of the Ln4 (Ln = Pr, Nd) clusters and the isolated Cl- anions occupying the large apertures of the structure. Luminescent studies indicate that Pr2(MoO4)(Te4O10) and Pr5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) are able to emit blue, green, and red light, whereas Nd2(MoO4)(Te4O10), Nd2W2Te2O13, and Nd5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) exhibit strong emission bands in the near-IR region.     

K2M(III)2(M(VI)O4)(PO4)2 (M(III) = Fe, Sc; M(VI) = Mo, W), novel members of the lagbeinite-related family: synthesis, structure, and magnetic properties

The possibility of PO(4)(3-) for MoO(4)(2-) partial substitution in the langbeinite framework has been studied by exploration of the K-Fe(Sc)-Mo(W)-P-O systems using the high-temperature solution method. It was shown that 1/3PO(4)(3-) for MoO(4)(2-) substitution leads to formation of three novel compounds K(2)Fe(MoO(4))(PO(4))(2), K(2)Sc(MoO(4))(PO(4))(2), and K(2)Sc(WO(4))(PO(4))(2) with slightly increased lattice parameters and significant distortion of the anion tetrahedra without structure changes. In contrast, the antiferromagnetic structure is modified by substitution in the low-temperature region. The structural peculiarities are discussed in light of bond-valence sums calculations.     

Structure of Mg2.56V1.12W0.88O8 and vibrational raman spectra of Mg2.5VWO8 and Mg2.5VMoO8

Mg(2.56)V(1.12)W(0.88)O(8) crystals were grown from a MgO/V(2)O(5)/WO(3) melt. X-ray single-crystal diffraction studies revealed that it is orthorhombic with space group Pnma, a = 5.0658(5) A, b = 10.333(1) A, c = 17.421(2) A, Z = 6, and is isostructural with Mg(2.5)VMoO(8). Raman spectra are reported, and the assignment of the Raman bands is made by comparing the metal-oxygen vibrations of VO(4)/WO(4) tetrahedra in Mg(2.5)VWO(8) with the metal-oxygen vibrations of VO(4)/MoO(4) tetrahedra in Mg(2.5)VMoO(8). The stretching vibrations appearing at 1016 and 1035 cm(-)(1) are assigned to Mo=O and W=O double bonds, respectively, associated with the Mg(2+) cation vacancies.     

Methanesulfonates of high-valent metals: syntheses and structural features of MoO2(CH3SO3)2, UO2(CH3SO3)2, ReO3(CH3SO3), VO(CH3SO3)2, and V2O3(CH3SO3)4 and their thermal decomposition under N2 and O2 atmosphere

Oxide methanesulfonates of Mo, U, Re, and V have been prepared by reaction of MoO(3), UO(2)(CH(3)COO)(2)·2H(2)O, Re(2)O(7)(H(2)O)(2), and V(2)O(5) with CH(3)SO(3)H or mixtures thereof with its anhydride. These compounds are the first examples of solvent-free oxide methanesulfonates of these elements. MoO(2)(CH(3)SO(3))(2) (Pbca, a=1487.05(4), b=752.55(2), c=1549.61(5) pm, V=1.73414(9) nm(3), Z=8) contains [MoO(2)] moieties connected by [CH(3)SO(3)] ions to form layers parallel to (100). UO(2)(CH(3)SO(3))(2) (P2(1)/c, a=1320.4(1), b=1014.41(6), c=1533.7(1) pm, β=112.80(1)°, V=1.8937(3) nm(3), Z=8) consists of linear UO(2)(2+) ions coordinated by five [CH(3)SO(3)] ions, forming a layer structure. VO(CH(3)SO(3))(2) (P2(1)/c, a=1136.5(1), b=869.87(7), c=915.5(1) pm, β=113.66(1)°, V=0.8290(2) nm(3), Z=4) contains [VO] units connected by methanesulfonate anions to form corrugated layers parallel to (100). In ReO(3)(CH(3)SO(3)) (P1, a=574.0(1), b=1279.6(3), c=1641.9(3) pm, α=102.08(2), β=96.11(2), γ=99.04(2)°, V=1.1523(4) nm(3), Z=8) a chain structure exhibiting infinite O-[ReO(2)]-O-[ReO(2)]-O chains is formed. Each [ReO(2)]-O-[ReO(2)] unit is coordinated by two bidentate [CH(3)SO(3)] ions. V(2)O(3)(CH(3)SO(3))(4) (I2/a, a=1645.2(3), b=583.1(1), c=1670.2(3) pm, β=102.58(3), V=1.5637(5) pm(3), Z=4) adopts a chain structure, too, but contains discrete [VO]-O-[VO] moieties, each coordinated by two bidentate [CH(3)SO(3)] ligands. Additional methanesulfonate ions connect the [V(2)O(3)] groups along [001]. Thermal decomposition of the compounds was monitored under N(2) and O(2) atmosphere by thermogravimetric/differential thermal analysis and XRD measurements. Under N(2) the decomposition proceeds with reduction of the metal leading to the oxides MoO(2), U(3)O(7), V(4)O(7), and VO(2); for MoO(2)(CH(3)SO(3))(2), a small amount of MoS(2) is formed. If the thermal decomposition is carried out in a atmosphere of O(2) the oxides MoO(3) and V(2)O(5) are formed.     

Opening the paddlewheel: unusual coordination of [Mo2] dumbbells in the chain structures of A[Mo2(CF3SO3)5]·2CF3SO3H (A = Na, Rb, Cs)

The reaction of Mo(II)acetate, concentrated triflic acid and the alkaline metal triflates A(CF(3)SO(3)) (A = Na, Rb, Cs) in sealed glass ampoules at 110 °C yielded red single crystals of A[Mo(2)(CF(3)SO(3))(5)]·2CF(3)SO(3)H (A = Na: triclinic, P-1, Z = 4, a = 13.714(1) ?, b = 14.339(1) ?, c = 21.340(2) ?, α = 81.78(1)°, β = 75.21(1)°, γ = 62.65(1)°; A = Rb/Cs: monoclinic, P2(1)/m, Z = 2, a = 11.561(1)/11.584(1) ?, b = 14.817(1)/14.9472(8) ?, c = 11.6208(1)/11.744(1) ?, β = 112.38(1)/113.48(1)°). The crystal structures contain dumbbell shaped [Mo(2)] moieties surrounded by three chelating and four monodentate triflate anions leading to an opening of the typical paddlewheel fragment at one of its edges. The monodentate triflate anions are connected to further [Mo(2)] dumbbells leading to infinite anionic chains according to (∞)(1)[Mo(2)(CF(3)SO(3))(3/1)(CF(3)SO(3))(4/2)](-). The charge balance is achieved by the alkaline metal ions that are additionally coordinated by triflic acid molecules. Theoretical investigations were preformed on the open paddlewheel fragment and are in good agreement with the experimental findings. According to DTA/TG measurements and the XRD investigations the decomposition of the compounds occurs in multiple steps and leads to MoO(2) and A(2)MoO(4).     

A study on the stability of O2 on oxometalloporphyrins by the first principles calculations

The authors investigated the interaction of oxometalloporphyrins (MO(por))--specifically, MoO(por), WO(por), TiO(por), VO(por), and CrO(por)--with O(2) by using first principles calculations. MoO(por) and WO(por) undergo reactions with O(2); on the other hand, TiO(por), VO(por), and CrO(por) do not. Next, they compared the interaction of MoO(por) and WO(por) with O(2). Activation barriers for the reactions of MoO(por) and WO(por) with a side-on O(2) are small. For MoO(por)(O(2)), the activation barrier for the reverse reaction that liberates O(2) is also small; however, that for WO(por)(O(2)) is large. The experimental results that photoirradiation with visible light or heating of Mo (VI)O(tmp)(O(2)) regenerates Mo (VI)O(tmp) by liberating O(2) while W (VI)O(tmp)(O(2)) does not [J. Tachibana, T. Imamura, and Y. Sasaki, Bull. Chem. Soc. Jpn. 71, 363 (1998)] are explained by the difference in activation barriers of the reverse reactions. This means that bonds formed between the W atom and O(2) are stronger than those between the Mo atom and O(2). The bond strengths can be explained by differences in the energy levels between the highest occupied molecular orbital of MoO(por) and WO(por), which are mainly formed from the a orbitals of the central metal atom and pi(*) orbitals of O(2).     

Sulfate separation by selective crystallization of a urea-functionalized metal-organic framework

Encapsulation of SO(4)(2-) into a Ni coordination framework functionalized with urea anion-binding groups allows selective separation of this strongly hydrophilic anion from a highly competitive aqueous environment.     

Fe(3+) coordinated to amino-functionalized MCM-41: an adsorbent for the toxic oxyanions with high capacity, resistibility to inhibiting anions, and reusability after a simple treatment

Fe(3+) coordinated to amino ligands fixed on MCM-41 mesoporous silica works as a strong adsorbent for toxic oxyanions. The maximum adsorption amounts were 1.56, 0.99, 0.81, and 1.29 mmol g(-1) for arsenate, chromate, selenate, and molybdate, respectively. When the initial concentrations of oxyanions were less than 1 mmol l(-1), they were removed completely by adsorption and the distribution coefficients K(d) were found to be more than 200000. Inhibition of oxyanion adsorption by abundant competing anions found in nature, NO(3)(-), SO(4)(-), PO(4)(3)(-) and Cl(-), was evaluated at adsorption saturation. Among these anions, the adsorption of the oxyanions was inhibited most in the presence of PO(4)(3)(-) , with which the selectivities for the target oxyanions were still more than 80%. The other coexisting anions, NO(3)(-), SO(4)(-), PO(4)(3)(-) and Cl(-), had little influence on adsorption of the oxyanions except in the case of selenate removal from sulfate solution. The high ability and selectivity to the target oxyanions are attributed to specific interactions between Fe(3+) and the oxyanions. The acid treatment and re-coordination of Fe(3+) lead to a reactivation of the used adsorbent, in which 87-90% of the original adsorption capacity was obtained and the oxyanion/Fe stoichiometries were not changed.     

Mercury(I) molybdates and tungstates: Hg2WO4 and two modifications of Hg2MoO4

The high-temperature (beta-) modification of Hg2MoO4 was prepared by solid-state reaction of HgO with MoO2 at 400 degrees C. Well-crystallized samples of the low-temperature (alpha-) modification of Hg2MoO4 and isotypic Hg2WO4 were obtained by hydrothermal recrystallization of the microcrystalline powders at 180 degrees C. The crystal structures of these transparent yellow compounds were determined by single-crystal X-ray diffractometry. beta-Hg2MoO4: P2(1)/c, Z = 4, a = 511.31(6) pm, b = 901.83(7) pm, c = 1086.0(1) pm, beta = 101.01(3) degrees. alpha-Hg2MoO4 and Hg2WO4: C2/c, Z = 4, a = 873.52(6) and 873.0(1) pm, b = 1155.19(7) and 1147.6(3) pm, c = 493.05(3) and 493.24(6) pm, beta = 115.196(5) degrees and 114.86(1) degrees, respectively. In beta-Hg2MoO4 the molybdenum atoms are tetrahedrally coordinated by oxygen atoms and the MoO4 tetrahedra are linked via Hg2 dumb-bells, thus forming infinite zigzag chains. The low-temperature (alpha-)modification of Hg2MoO4 contains MoO6 octahedra, which are linked via common edges to form zigzag chains, which are further linked via Hg2 dumb-bells, resulting in puckered two-dimensionally infinite sheets. Bonding between adjacent sheets is achieved only via weak (secondary) Hg-O bonds of 254.8 pm, while the strong Hg-O bonds of the nearly linear O-Hg-Hg-O groups within the sheets have a length of 214.8 pm. The Hg-Hg bond lengths are practically the same in the three compounds with 252.3(1), 253.49(7), and 253.3(1) pm in beta-Hg2MoO4, alpha-Hg2MoO4, and Hg2WO4, respectively. The average Mo-O distances within the MoO4 tetrahedra and the MoO6 octahedra are 176.2, and 196.5 pm, respectively. The structural chemistry of these compounds is discussed together with that of previously reported mercury I and II molybdates and tungstates.     

Electrochemical performance of carbon paper supercapacitor using sodium molybdate gel polymer electrolyte and nickel molybdate electrode

Journal of Solid State Electrochemistry - Graphene oxide–modified poly (vinyl alcohol)/sodium sulfate-sodium molybdate (GO/PVA-Na2SO4-Na2MoO4, GPSS) gel polymer electrolyte and nickel...     

Ab initio investigation on ion-associated species and association process in aqueous Na2SO4 and Na2SO4/MgSO4 solutions

In the present paper, the possible ion associated species in pure Na(2)SO(4) and mixed Na(2)SO(4)/MgSO(4) aqueous solutions are investigated via the ab initio method at the HF/6-31+G? level. The vibrational v(1)-SO(4)(2-) band is analyzed. For the unhydrated species, when the number of metal ions around the SO(4)(2-) ion is less than 3, the dominating effect to the v(1)-SO(4)(2-) band is the polarization of the cations, while the M-O bonding will be dominating as the number is equal to or more than 3. For the hydrated species, the coordinated structures of the Na(+) ion in all ion pairs are not stable due to the strong effect of the SO(4)(2-) ion but relatively stable in the triple ion (TI) clusters since there are fewer vacant hydration sites around the SO(4)(2-). The v(1)-SO(4)(2-) frequencies are close to that of the hydrated SO(4)(2-) ion in the ion pairs and larger in both Na(2)SO(4) and Na(2)SO(4)/MgSO(4) TI clusters. On the basis of our calculated results, the evolvement of Raman spectra in the Na(2)SO(4)/MgSO(4) droplet with the molar ratio of 1:1 is explained.     

Electrochromic hysteresis performance of a prussian blue film arising from electron-transfer control by a tris(2,2'-bipyridine)ruthenium(II)-doped WO(3) film as studied by a spectrocyclic voltammetry technique

A [Ru(bpy)(3)](2+) (bpy=2,2'-bipyridine)-doped WO(3) film was prepared as a base layer on a substrate by cathodic electrodeposition from a colloidal triad solution containing peroxotungstic acid (PTA), [Ru(bpy)(3)](2+), and poly(sodium 4-styrenesulfonate) (PSS). A Prussian blue (PB; Fe(II)-Fe(III)) film was cathodically electrodeposited on the [Ru(bpy)(3)](2+)-doped WO(3) film or neat WO(3) film from an aqueous Berlin brown (BB; Fe(III)-Fe(III)) colloid solution to yield a [Ru(bpy)(3)](2+)-doped WO(3)/PB bilayer film or WO(3)/PB bilayer film. For the spectrocyclic voltammogram (SCV) of the WO(3)/PB film, a redox response of Prussian white (PW; Fe(II)-Fe(II))/PB was observed at 0.11 V, however, further oxidation of PB to BB was not allowed by the interfacial n-type Schottky barrier between the WO(3) and PB layers. For the [Ru(bpy)(3)](2+)-doped WO(3)/PB film, any electrochemical response assigned to the redox of PB was not observed in the cyclic voltammogram, however, the in situ absorption spectral change recorded simultaneously showed the significant redox reactions based on PB. The SCV revealed that PW on the [Ru(bpy)(3)](2+)-doped WO(3) film is completely oxidized to PB by a geared reaction of Ru(II)/Ru(III) at 1.05 V, and that 32 % of PB formed is further oxidized to BB by the same geared reaction in the potential scan to 1.5 V. PB was completely re-reduced to PW by a geared reaction of H(x)WO(3)/WO(3) at -0.5 V in the reductive potential scan. These geared electrochemical reactions produced an electrochromic hysteresis performance of the PB film layered on the [Ru(bpy)(3)](2+)-doped WO(3) film.     

Simple procedures for assessing and exploiting the selectivity of anion extraction and transport

The strength and selectivity of anion-binding by metal salt extractants have been assessed by defining the pH-dependence of anion uptake into a water-immiscible solution of the "metal-only" complexes; high Cl-/SO4(2-) selectivity of transport has been developed.     

Oxygen-17 NMR study of aqueous peroxotungstates

Aqueous peroxotungstates have been studied from pH 0.5 to 9.0, over a range of peroxide concentrations. Although equilibria are not always established, many anions can be identified by 17O NMR because the ratio of deltaO(W anion)/deltaO(known Mo anion) is consistently 79 +/- 3%. They are [WO3(HO2)]-; [WO(OH)(O2)2]-; [WO(OH2)(O2)2]0; [W2O3(O2)4]2-; [W2O3(OH)(O2)4]3-; [W4O12(O2)2]4-; [W7O23(O2)]6- and [W7O22(O2)2]6-. Their pKa values, where measurable, are about 2 units lower than the corresponding peroxomolybdates, e.g. 0.0 for [WO(OH2)(O2)2]0 and 8.0 for [W2O3(O2)4]2-. Other peroxotungstate species are also present but can only be broadly identified. These include Keggin structures with relatively low peroxo content, and a very unsymmetrical anion appearing at pH ca. 7 that bears no obvious structural relationship to any species previously reported. The main product from the reaction of powdered W metal with 30% aqueous peroxide is provisionally identified as the symmetrical anion [W6O13(OH)2(OH2)2(O2)5]2-, although other minor species are also formed, probably having fewer peroxo substituents.     

C5H14N2][(MoO3)3(SO4)].H2O: sulfated alpha-molybdena chains

Recent work in the preparation of organically templated metal sulfates under hydrothermal conditions has been extended to include the sulfation of alpha-molybdena through the synthesis of [C(5)H(14)N(2)][(MoO(3))(3)(SO(4))].H(2)O. Single crystals were grown under hydrothermal conditions from molybdenum oxide, water, sulfuric acid, and an enantiomerically pure (R)-2-methylpiperazine source and characterized using both single-crystal X-ray diffraction and infrared spectroscopy. One-dimensional [(MoO(3))(3)(SO(4))](n)(2n-) chains, based on a neutral alpha-molybdena backbone, are connected through an extensive hydrogen-bonding network containing [C(5)H(14)N(2)](2+) cations and occluded water molecules. The direction of the hydrogen bonding is primarily dictated by the nucleophilicity of the respective oxide ligands, as determined using bond valence sums.