Preparation and Properties of the Heteropolyoxometalates of Large Organic Cation with Molybdotungstosilicic Acids

Some new heteropolyoxometalates of large organic cations with molybdotungstosilicic acids （general formula： （CTMA）4SiMoxW12-xO40·mH2O·nDMF, x=0,2,4,6,8,10,12） were prepared by the reaction of cetyltrimethylammonium bromide （CTMAB,C16H33N（CH3）3Br） with H4SiMoxW12-xO40（x=0,2,4,6,8,10,12） in aqueous solution and recrystallization in DMF, and characterized by elemental analysis, IR spectra,TG- DTA and XRD techniques. The IR spectrum confirms the presence of Keggin structure and organic cations in these compounds, and it is indicated that the stretching vibration of the M-Od, M-Ob-M and Si-Oa becomes more red-shifted when molybdenum is gradually substituted for the tungsten atom. In particular, the thermal decomposition of the heteropolyoxometalates was studied in nitrogen atmosphere. The TG-DTA curves show that their thermal behaviors not only contain the release of water molecule, DMF molecule, CTMA and its fragments but also contains simultaneous collapse of Keggin anion. Their end products of the thermal decomposition are the mixture of WO3, MoO3 and SiO2. And from the final decomposition temperature of view, it is found that the thermal stability of these compounds gradually is decreased when the number of molybdenum atoms is increased.

Orientations of Rare-earth-containing Heteropolyoxometalates with Different Sizes in the Interlayer of Synthetic Multibilayer Films

Three rare-earth-containing heteropolyoxometalates with different sizes, Na9[Eu(W5 O18)2], K13[Eu(SiW11O39)2], and K17[Eu(P2W17O61)2], have been incorporated by self-assembly into the interlayer of synthetic multibilayer films of dimethyldioctadecylammonium chloride and exhibited different orientations.

Magnetic properties of heteropolyoxometalates

The progress of the study on the magnetic properties of heteropolyoxometalates during the late decade is reviewed. Some anions of heteropolyoxometalates containing magnetic atoms, such as [M4（H2O）4(PW9O342]10- and [M4（H2O）4(P2W15O562]16-[M= Co（ Ⅱ ）, Zn（ Ⅱ ）, Cu（ Ⅱ ）, Mn（ Ⅱ ）,Ni（ Ⅱ ）], and [GaW9O37M3（H2O）3]n-[M= Fe（ Ⅲ ）, Cu（ Ⅱ ）, Co（ Ⅱ ）], showed ferromagnetic and antiferromagnetic properties. The combination of heteropoly anions and organic π-donor of TTF+ （tetrathiofulvalene cation） results in a variety of magnetic properties. Furthermore, there is an interaction between the inorganic and organic components. The electrocrystallization technique can prepare the organic-inorganic salts of this kind, which will become the new member of molecular magnetic materials.Heteropoly blue is a kind of the mixed-valence complexes and its reduction electrons can be delocalized over anionic framework. The further study on the magnetic properties of heteropolyoxometalates

Selective oxidation of primary substituted aromatic amines to azoxy products using lacunary catalyses

Some of the substituted anilines were selectively converted in to the corresponding azoxy and azobenzenes by oxidation with 30%aqueous hydrogen peroxide.The reactions were catalyzed by various heteropolyoxometalates,at boiling point of the used solvents.An improvement in the product yield and selectivity towards azoxybenzens was also observed.Azobenzenes was obtained as by-product.In the all similar cases,the highest yield of azoxy compounds was observed using K_5PW_(11) ZnO_(39) as catalyst in N,N-dimethyl...

STM Study on the Rectifying Performance of Molibdo-Vanadophosphate Polyanions

Scanning tunneling spectroscopy (STS) was used for investigation of rectification properties of molecules with spatial asymmetry. The molecules of cetyltrimethylammonium derivatives of 10-molibdo-2-vanadophosphate-anions [PMo10V2O40]﹣5 (CTMVA) were adsorbed on a surface of pyrolytic graphite (HOPG). Consequently, both good diode properties and J(V)-curves reproducibility of the film were revealed. The validity of the single-level model for the evaluation of the system parameters is discussed.

乳液催化剂存在下空气辅助甲酸氧化法使油品脱硫(英文)

Catalytic oxidative desulfurization(ODS) of model oil and commercial oil samples was investigated using an air-assisted performic acid oxidation system with a phase transfer or emulsion catalyst comprising a quaternary ammonium salt-based heteropolyoxometalate.Different emulsion catalysts with a Keggin type heteroployoxometalate anion(containing W,Mo,and V) and cetyltrimethylammonium bromide cation were prepared and characterized by X-ray fluorescence,Fourier transform infrared spectroscopy,and scanning electron microscopy.[C16H33N(CH3)3]3[PW9Mo3O40] was the most effective catalyst in the current oxidation system,which reduced the sulfur content of the model oil from 1275 μg/g to 57 μg/g.The reactivity order of different model sulfur compounds was thiophene < dibenzothiophene < 4,6-dimethyldibenzothiophene. The ODS of model sulfur compounds followed first order kinetics with apparent activation energy from 29 to 27 kJ/mol.The catalysts also performed efficiently in the ODS of the industrial oil samples,including untreated naphtha,light gas oil,heavy gas oil,and Athabasca oil sands derived bitumen,for which sulfur removal rates were 83%,85%,68% and 64%,respectively.

Preparation and Photochromic Properties of Hybrid Thin Films Based on Heteropolyoxometallate and Polyacrylamide

A series of photochromic hybrid films were prepared through entrapping Dawson type tungsten heteropolyoxomet-allates (P2W18C626-) and molybdenum heteropolyoxometallate (P2Mo18O626-) into polyacrylamide matrix. FTIR results showed that the Dawson geometry of heteropolyoxometallates is still preserved inside the composites and strong coulombic interaction is built between heteropolyoxometallates and polyacrylamide via hydrogen bonding. Irradiated with ultraviolet light, the transparent films change from colorless to blue and show reversible photochromism. The bleaching process occurs when the films are in contact with air or O2 in the dark. The molybdenum heteropolyoxometallate hybrid film has higher photochromic efficiency and slower bleaching reaction than tungsten heteropolyoxometallate hybrid film. ESR results indicated that polyacrylamide is a hydrogen donor and the photoreduced process is in accordance with the radical mechanism.