Photochemical synthesis, characterization and X-ray crystal structure of dodecamolybdophosphate tetrabutylammonium heteropoly blue (Bu4N)(4)[PMo12O40]center dot 2DMF center dot H2O

In this paper, we will report the preparation of a mixed-valence polyoxometalate compound (Bu4N)(4)[PMo12O40].2DMF.H2O (TBA = tetrabutylammonium; DMF = N,N-dimethyl formamide). The title compound has been photochemically synthesized and characterized by using elemental analysis, IR, solid diffusion reflectance electronic spectra, ESR spectra, XPS, CV and X-ray single-crystal analysis. The crystal lographic data are as follows: monoclinic, P2(1)/c, a = 14.124(3), b = 17.481(4), c = 22.744(5) Angstrom, beta = 101.66(3)degrees, V = 5500(2) Angstrom(3), C70H160Mo12N6O43P, M-r = 2956.29, Z = 2, D-c = 1.785 g/cm(3), F(000) = 2970 and mu(MoKalpha) = 1.412 mm(-1). The structure has been refined to R = 0.0638 and wR = 0.1975 by full-matrix least-squares methods. The title compound is composed of four tetrabutylammonium cations, one [(PMoMo11O40)-Mo-V](4-) heteropoly anion, two N,N-dimethyl formamide and one H2O molecule.

Photochemical synthesis, properties and X-ray crystal structure of tetrabutylammonium dodecamolybdophosphate heteropoly blue

The title heteropoly blue, (Bu4N)(6)H-10 [(PMo11MoO40)-Mo-VI-O-V](4) . H2O has been photochemically synthesized and characterized with elemental analysis, solid diffusion reflectance electronic spectra, CV, ESR, XPS, IR spectra, conductivity measurement and X-ray single crystal analysis. The crystallographic data for C96H218Mo48N6O169P4 are as follows: M-r = 8889.76, triclinic, P (1) over bar, a = 1.4142 (3) nm, b = 2.6027 (5) nm, c = 2.6403(5) nm, alpha = 113.96(3)degrees, beta = 90.05(3)degrees, gamma = 105.71(3)degrees, V = 8.481 (3) nm(3), Z = 1, D-c = 1.741 g/cm(3), F (000) = 4264, mu = 1.798 mm(-1). The X-ray crystal structure analysis reveals that there Is one independent molecule in the unit cell of the title heteropoly blue which contains four mixed-valence heteropoly anions, six tetrabutylammonium cations and one water molecule. Its molecular structure possesses a centrosymmetrical arrangement in the unit cell. The phosphorus atom is In the crystallographic inversion center of the heteropoly anion and the eight oxygen atoms surrounding central phosphorus atom comprise of a distorted hexahedron. Heteropolyanion has two equal sets of PO4 tetrahedron. The PO4 tetrahedron and the MoO6 octahedron in the polyanion are greatly distorted.

ISOLATION AND PROPERTIES OF MOLYBDENUM SERIES OF HETEROPOLY BLUE WITH KEGGIN STRUCTURE

The present paper reports the methods for preparing and isolating 8 kinds of 1:12 molybdenum series of heteropoly blue complexes KyHzXMo12O40 . nH2O (X=Si, P, As, Ge). The products were characterized by elemental analyses, potential titration, polarograms, cyclic voltammetry, IR spectra, visible-UV spectra, X-ray powder diffraction, XPS and P-31 NMR. The single crystal structure of 4-electron molybdenum-silicon heteropoly blue was measured and the positions of reduced molybdenum atoms were determined, i.e. they were located at Mo(3), Mo(7), Mo(8) and Mo(10). The experimental results show that the heteropoly blue remains Keggin structure. ESR spectra of heteropoly blue solids were first studied, from which it was found that the delocalization extent of 2-electron heteropoly blue and 4-electron heteropoly blue is smaller than that of 1-electron heteropoly blue. The study of thermal properties shows that the thermal stability increases with the increase of the reduction extent of heteropoly blue. The study of redox properties shows that the oxidizing power order of heteropoly blue changes in different mediums, and the polarographic half-wave voltage is found to be dependent on the electronegativity of the hetero atom linearly. It is found that the phosphorus heteropoly blue and arsenic heteropoly blue show a strong anti-acid property.

THE SYNTHESIS AND CRYSTAL-STRUCTURE OF MOLYBDENUM-SILICON BLUE

The single crystal of heteropoly blue, HsSiMo12O40.12H2O, the reduced product of molybdenum-silicon heteropoly acid, was prepared by electrochemical reduction and evaporation in nitrogen atmosphere. The Crystal structure of the product was determined. The heteropoly blue H8SiMo12O40.12H2O, Crystallizes space group P1BAR a = 1.3769 (3) nm, b = 1.4346 (4) nm, c = 1.4134 (4) nm, alpha = 120.47 (2)-degrees, beta = 110.70 (2)-degrees, gamma = 66.11 (2)-degrees, Z = 2, R = 0.0608. The heteropoly blue anion was determined to have Keggin Structure and alpha-isomer and it remained the structure of the unreduced heteropoly acid anion. But the distortion of the structure and the changes of bond length and bond angle take place obviously. The four Mo5+ Positions were determined in the structure.

ELECTROCHEMICAL STUDY OF ISOPOLY AND HETEROPOLY OXOMETALLATE FILM MODIFIED MICROELECTRODES .5. PREPARATION AND ELECTROCHEMICAL-BEHAVIOR OF A 2/18-MOLYBDODIPHOSPHATE ANION MONOLAYER MODIFIED ELECTRODE

In this paper a carbon fibre (CF) microelectrode modified with the 2:18-molybdodiphosphate anion by simple adsorption is described and its electrochemical behaviour is reported. The 2:18-molybdodiphosphate anion (alpha-P2Mo18O626-), which is a Dawson structure, undergoes five successive multielectron reductions in acidic solution. The first three redox waves correspond to the two-electron process, and the last two waves are four-electron and six-electron processes respectively. On the basis of the experimental results it is shown that the electrode process of alpha-P2Mo18O626- on the CF electrode in acidic solution is simultaneously controlled by the diffusion and adsorption of alpha-P2Mo18O626- anions. When the concentration of the alpha-P2Mo18O626- in the solution is reduced, the electrode process mainly exhibits non-diffusion-controlled behaviour, and the diffusion-limited process takes over as the concentration of alpha-P2Mo18O626- becomes higher. The CF electrode modified with a thin film of alpha-P2Mo18O626- exhibits very good stability and redox behaviour in aqueous acidic solution. The alpha-P2Mo18O626- is reduced to heteropoly blue, with an accompanying protonation process. The addition of more than six electrons to the alpha-P2Mo18O626- anion in an aqueous solution does not result in its decomposition. The result obtained is not the same as that reported previously.

A chromic molybdenum phosphate with a tunnel structure: hydrothermal synthesis and structure of (NH3CH2CH2NH3)(2) center dot (NH3CH2CH2NH2)(3)center dot[NaCr2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 6H(2)O

A chromic molybdenum phosphate, (NH3CH2CH2NH3)(2).(NH3CH2CH2NH2)(3).[NaCr2Mo12O30(PO4)(HPO4)(3)]. 6H(2)O, involving molybdenum present in V oxidation, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction and IR spectrum. Deep brown-red crystals are formed in the triclinic system, space group P (1) over bar, a = 12.067(2), b = 14.677(3), c = 21.290(2) Angstrom, alpha = 80.940(10)degrees, beta = 82.960(10)degrees, gamma = 76.61(2)degrees. The structure of the title compound may be considered to be two [Mo6O15(HPO4)(H2PO4)(3)](5-) units bonded to a chromic atom, although several P-O groups are not protonated on account of coordination with a Na+ cation. The one-dimensional tunnels were formed in the solid of the title compound. (C) 2000 Elsevier Science B.V. All rights reserved.

A manganese molybdenum phosphate with a tunnel: hydrothermal synthesis, structure and catalytic properties of (NH3CH2CH2NH3)(10-)H3O)(3)(H5O2)Na-2[MnMo12O24(OH)(6)(PO4)(4)(PO3OH)(4)]-[MnMo12O24(OH)(6)(PO4)(6)(PO3OH)(2)] center dot 9H(2)O

A manganese molybdenum phosphate, (NH3CH2CH2NH3)(10)(H3O)(3)(H5O)Na-2[MnMo12O24(OH)(6) (PO4)(4)(PO3OH)(4)][MnMo12O24 (OH)(6)(PO4)(6)(PO3OH)(2)]. 9H(2)O, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. The structure of this compound may be considered to be two [Mo6O12(OH)(3)(PO4)(2)(HPO4)(2)](7-) units bonded together by a manganese atom, although several P-O groups are not protonated on account of coordination to a Na+ cation. One-dimensional tunnels were formed in the solid. A probe reaction of the oxidation of acetaldehyde with H2O2 using this compound as catalyst was carried out in a liquid-solid system, showing that the manganese molybdenum phosphate has high catalytic activity in the reaction.

A nickel molybdenum phosphate with tunnel: Hydrothermal synthesis and structure of (NH3CH2CH2NH3)(4)center dot(NH3CH2CH2NH2)center dot Na center dot[Ni2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 6H(2)O

A nickel molybdenum phosphate, (NH3CH2CH2NH3)(4).(NH3CH2CH2NH2). Na .[Ni2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]. 6H(2)O, invoicing molybdenum present in V oxidation, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. Deep brown-red crystals are formed in the triclinic system, space group P (1) over bar, a = 12,011(2), b = 14,612(3), c = 21.252(4) Angstrom, alpha = 80.54(2)degrees, beta = 83.10(2)degrees, gamma = 76.29(2)degrees, V = 3561.4(12) Angstrom(3), Z = 2, lambda(MoK alpha) = 0.71073 Angstrom (R(F) = 0.0529 for 9880 reflections), Data mere collected on a Siemens P4 diffractometer at 20 degrees C in the range of 1.75 degrees < theta < 23.02 degrees using the omega-scan technique. The structure was solved by direct methods using the program SHELXTL-93 and refined with the method of fun-matrix least-squares on F-2. The structure of the title compound may be considered to be two [Mo6O15(HPO4)(H2PO4)(3)](5-) units bonded together with a nickel atom, although several P-O groups are not protonated on account of coordination with a Na+ cation, The one-dimensional tunnels were formed in the solid of the title compound. A probe reaction of the oxidation of acetaldehyde with H2O2 using the title compound as catalyst was carried out in a liquid- solid system, showing that the title compound had high catalytic activity in the reaction, (C) 1999 Academic Press.

A ferric molybdenum phosphate with a tunnel: hydrothermal synthesis and structure of (NH3CH2CH2NH3)(2)center dot(NH3CH2CH2NH2)(3)center dot Na center dot[Fe2Mo12O30(PO4)(HPO4)(4)(H2PO4)(3)]center dot 7H(2)O

A new ferric molybdenum phosphate containing a tunnel structure and crystallographically different clusters has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. A probe reaction of the oxidation of acetaldehyde with H2O2 using the tide compound as catalyst was carried out in a liquid-solid system, showing that the title compound had high catalytic activity in the reaction. (C) 1998 Elsevier Science S.A. All rights reserved.

ELECTROCHEMICAL STUDY OF ISOPOLY-OXOMETALLATES AND HETEROPOLY-OXOMETALLATES FILM MODIFIED MICROELECTRODES .3. FURTHER STUDY OF ELECTRODE PROCESS OF ISOPOLYMOLYBDIC ANION DOPED IN POLYANILINE FILM

The isopolymolybdic anion-polyaniline film modified carbon fiber (CF) microelectrode with high stability and electroactivity in aqueous acid solution has been successfully prepared by cycling the potential between -0.15 V and +0.85 V vs. sce at 100 mV s-1 or applying constant potential (+0.85 V) for electropolymerization in a 0.5 M H2SO4 solution containing 5.0 x 10(-2) M aniline and 5.0 x 10(-3) M H4Mo8O26. The electrochemical behaviour of the isopolymolybdic anion entrapped in the polyaniline film is strongly influenced by the sweep-potential range besides the acidity of electrolyte solution. In some acidic electrolyte solution (eg 0.5 M H2SO4), the change of the sweep-potential range causes the structure alternation of the isopolymolybdic anion and resulting in a new electrode process. The cyclic voltammogram of Mo8O264- in 0.5 M H2SO4 solution exhibits three two-electron reversible waves between +0.70 and -0.20 V. However, when the potential sweeps to the lower-limit of -0.3 V, where the fourth four-electron cathodic wave appears, the redoxidation process of the reduction product of Mo8O264- becomes relatively complicated. The 10-electron reduction product seems to change into other isopolyanion (this unknown structure isopolyanions are simply called [Mo-O]), which can be reoxidized to Mo8O264- by five successive two-electron oxidation steps from -0.30 to +0.70 V. However, when the lower-limit of the cycling potential is maintained at -0.30 V and the upper-limit reduces to +0.40 V from +0.70 V, the [Mo-O] in the film exhibits four two-electron reversible waves. We have presented a novel explanation about its electrode reaction mechanism on the basis of our experimental results.

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Synthesis, characterization of palygorskite supported zero-valent iron and its application for methylene blue adsorption

In this work, natural palygorskite impregnated with zero-valent iron (ZVI) was prepared and characterised. The combination of ZVI particles on surface of fibrous palygorskite can help to overcome the disadvantage of ultra-fine powders which may have strong tendency to agglomerate into larger particles, resulting in an adverse effect on both effective surface area and catalyst performance. There is a significant increase of methylene blue (MB) decolourized efficiency on acid treated palygorskite with ZVI grafted, within 5 mins, the concentration of MB in the solution was decreased from 94 mg/L to around 20 mg/L and the equilibration was reached at about 30 to 60 mins with only around 10 mg/L MB remained in solution. Changes in the surface and structure of prepared materials were characterized using X-ray diffraction (XRD), infrared (IR) spectroscopy, surface analysing and scanning electron microscopy (SEM) with element analysis and mapping. Comparing with zero-valent iron and palygorskite, the presence of zero-valent iron reactive species on the palygorskite surface strongly increases the decolourization capacity for methylene blue, and it is significant for providing novel modified clay catalyst materials for the removal of organic contaminants from waste water.

Synchronous fluorescence and UV–vis spectroscopic studies of interactions between the tetracycline antibiotic, aluminium ions and DNA with the aid of the Methylene Blue dye probe

Synchronous fluorescence spectroscopy (SFS) was applied for the investigation of interactions of the antibiotic, tetracycline (TC), with DNA in the presence of aluminium ions (Al3+). The study was facilitated by the use of the Methylene Blue (MB) dye probe, and the interpretation of the spectral data with the aid of the chemometrics method, parallel factor analysis (PARAFAC). Three-way synchronous fluorescence analysis extracted the important optimum constant wavelength differences, Δλ, and showed that for the TC–Al3+–DNA, TC–Al3+ and MB dye systems, the associated Δλ values were different (Δλ = 80, 75 and 30 nm, respectively). Subsequent PARAFAC analysis demonstrated the extraction of the equilibrium concentration profiles for the TC–Al3+, TC–Al3+–DNA and MB probe systems. This information is unobtainable by conventional means of data interpretation. The results indicated that the MB dye interacted with the TC–Al3+–DNA surface complex, presumably via a reaction intermediate, TC–Al3+–DNA–MB, leading to the displacement of the TC–Al3+ by the incoming MB dye probe.