A New Steady and Water-insoluble Polytungstate： Synthesis, Structure, Characterizations and Photocatalytic Properties

Polyoxometalate （POM）-based materials universally have some inherent flaws, including low recovery, metastability, solubility, etc., which may restrict their practical applications. Modifying the materials with organic-inorganic hybrid complexes is one of the most effective approaches to overcome these deficiencies. Under hydrothermal conditions, a new Wells- Dawson-type polytungstate modified Cd-complex, [Cd（phen）3]3[W18O54（PO4）2]？3H2O （1, phen = 1,10-phenanthroline （C12N2H8））, has been synthesized by selecting Cd2＋ coordinated phen and employing stepwise self-assembly plans. The compound shows good stability and water- insolubility under normal circumstances. Experiments demonstrate that compound 1 has ideal catalytic activity in the degradation reaction of rhodamine B （RhB） under ultraviolet （UV）-light and oxidant H2O2 conditions. Detailed characterizations including X-ray single-crystal diffraction （XRD）, Powder X-ray diffraction （PXRD）, elemental analysis, energy-dispersive X-ray spectroscopy （EDS） analyses, Fourier transform infrared spectroscopy （FT-IR）, UV-Vis-NIR diffuse reflection spectrum （DRS） and XPS spectrum are presented herein. The electrochemical （cyclic voltammetry （CV）） and photocatalytic properties of 1 have also been studied.

Studies on Organo-Phosphorus, -Arsenic and -Antimony Polytungstates and Polymolybdates(IX )——Preparation and Properties of o-Aminophenylarsenic Polymolybdates

In order to investigate the influence of organic groups on the types of organoarsenic polymolybdates, o-nitrophenylarsonic acid was reduced to o- aminophenylarsonic acid and then it reacted with sodium molybdate at pH = 3;. Three new salts were prepared and characterized:（ 1 ） （CN3H6）4[（o-NH2C6H4As）2Mo6O24], （ 2 ） Cs4[（o-NH2C6H4As）2Mo6O24], （3） [（CH3）4N]4[（o-NH2C6H4As）2Mo6O24].2H2O. The IR, UV spectra, thermal properties and electrochemical behaviors are reported. It is strange enough that when the o-nitro group was reduced to o-amino group, [（RAs）2Mo6O24]4- type of complexes was formed.

Studies on Organo-Phosphorus, -Arsenic and -Antimony Polytungstates and Polymolybdates (Ⅶ)——Preparation and Properties of p-Aminophenylarsenic Polymolybdates

In order to investigate the influence of organic groups on the types of organoarsenic polymolybdates, the reations of p-aminophenylarsonic acid with sodium molybdate were tested at pH=3-5. Six salts were prepared and characterized. (1) (CN3H8)4 [(p-NH3C6H4As)2Mo6O25] · H2O, (2) (CN3H6)4 [(p-, NH3C6H4As )2Mo6O25 ] · 6H20, (3) Cs4 [(p-NH3C6H4As)2Mo6O25] · 4H2O, (4) C(CH3)4N]4[(p-NH3C6H4As)2Mo6O25] · 5H2O, (5) [(n-C4H9)4N]3Na[(p-NH3C6H4As)2Mo6O25] · 2H2O, (6) Ba2 NH3C6H4As)2Mo6O25] · 10H2O. The IR, UV spectra, and electrochemical behavior are reported and discussed. They should belong to the same type as that for phenyl derivative or the nitrophenyl derivatives. But the ammo groups can accept protons, so that the anion' s charge decreases. Very similar to the tungsten congener (CN3H6)4[(p-NH3C,H4As)2W6O25] · 4H2O, [(RAs)2Mo6O25]4- type of complexes are formed.

Ln-substituted polytungstates as efficient hetergeneous catalysts for Knoevenagel condensation reaction

Three isomorphic polytungstates,CsgK_(18)H_(10){[Sm_(2)(H_(2)O)_(4)W_(4)O_(10)(AsW_(9)0_(33))3]_(2)(N(CH_(2)PO_(3))_(2))}:46.5H_(2)O(1),CS_(10)K_(9)H_(18){[Eu_(2)(H_(2)O)_(4)W_(4)O_(10)(AsW_(9)0_(33))_(3)]_(2)(N(CH_(2)PO_(3))_(2))}.41.5H_(2)O(2),Cs_(10)K_(9)H_(18){[Gd_(2)(H_(2)O)_(4)W_(4)O_(10)(AsW_(9)O_(33))_(3)]_(2)(N(CH_(2)PO_(3))_(2))}:46H_(2)O(_(3)),have been successfully synthesized and characterized by routine methods,and demonstrated excellent catalytic activities in Knoevenagel condensation reaction as heterogeneous catalysts.Notably,catalyst 1 achieved higher reaction activity than catalysts 2 and 3,where a satisfactory reaction yield(95%)and high TON value(6380)could be obtained at moderate reaction condition.In addition,in the scale-up experiment,with the help of catalyst 1,7.8g benzaldehyde and 5.7g ethyl cyanoacetate could transform into corresponding condensation product with a satisfactory yield(83%)and impressive TON value(13.883).

Studies on organo-phosphorus, -arsenic and -antimony polytungstates and polymolybdates——II. Degradation method for preparing arylarsenic polytungstates

Six guanidinium salts of arylarsenic po1ytungstates have been prepared by the 'degradation method' using sodium metatungstate as a starting material instead of sodium tungstate, They belong to three types of complexes: [(RAs)_2W_6O_(25)H]^(5-) where R=C_6H_5(1),o-NO_2C_6H_4(2),m-NO_2C_6H_4(3), p-NO_2C_6H_4(4),[(RAs)_2W_6O_(25)]^(4-) where R=p-NH_2C_6H_4(5), and[(RAs)_2W_6O(25)]^(6-)where R=3,4,-C_6H_3 (NO_2)(OH)(6). Complex 1 is a known compound, prepared by the acidification building up method, i.e. conversion of sodium tungstate to polytungstate. Complex 1 and 6 prepared by the degradation method, i.e. from sodium metatungstate to lower polytungstate, are briefly reported in our previous re- port of this investigation. Complexes 2-5 are new compounds. Molecular structures of complexes 5 and 6 have been determined by means of single-crystal X-ray diffraction studies. It is especially em- phasized that the degradation method starting with metatungstate has the advantage in the simplification of reaction products. thus leading to their higher yields.

Studies on organo-phosphorus,-arsenic,and-antimony polytungstates and polymolybdates Ⅴ.Syntheses and structures of benzylarsonic polymolybdates

In order to investigate the influence of organic groups on the structural types of organoa- rsenic polymolybdates,benzylarsonic acid has been selected to react with sodium molybdate.Three new complexes have been synthesized and characterized:[C(NH_2)_3]_4 [(C_6H_5CH_2As)_2Mo_6O_(24)](1), Cs_4[(C_6H_5CH_2As)_2Mo_6O_(24)]·5H_2O(2)and[(n-C_4H_9)_4N]_3Na[(C_6H_5CH_2As)_2Mo_6O_(24)].6H_2O(3).Molecular structure of compound 1 has been determined by means of single-crystal X-ray diffraction studies.It is monoclinic,space group P2_1/n with cell dimensions of a=12.342(2),b=18.621(2),c=10.042(2), β=105.80(1)°,V=2220.5~3,z=2,μ=15.854cm^(-1),R=0.023.It is demonstrated that the structural types of benzylarsonic polymolybdates are the same as those for alkylarsonic polymolybdates but different from those for arylarsonic polymolybdates.Their elemental analyses,IR and UV spectra and electrochemical behaviors in aqueous solution have been reported.It is suggested that the arsenic- carbon bond has great influence on the structural types of organoarsenic polymolybdates.

Does Particulate Organic Matter Fraction Meet the Criteria for a Model Soil Organic Matter Pool?

There is a well-recognized need for improved fractionation methods to partition soil organic matter into functional pools. Physical separation based on particle size is widely used, yielding particulate organic matter(POM, i.e., free or "uncomplexed" organic matter> 50 μm) as the most labile fraction. To evaluate whether POM meets criteria for an ideal model pool, we examined whether it is:1) unique, i.e., found only in the > 50 μm fraction and 2) homogeneous, rather than a composite of different subfractions. Following ultrasonic dispersion, sand(> 50 μm) along with coarse(20–50 μm) and fine(5–20 μm) silt fractions were isolated from a silt loam soil under long-term pasture at Lincoln, New Zealand. The sand and silt fractions contained 20% and 21% of total soil C, respectively.We adopted a sequential density separation procedure using sodium polytungstate with density increasing step-wise from 1.7 to 2.4 g cm^(-3) to recover organic matter(light fractions) from the sand and silt fractions. Almost all(ca. 90%) the organic matter in the sand fraction and a large proportion(ca. 60%–70%) in the silt fractions was recovered by sequential density separation. The results suggested that POM is a composite of organo-mineral complexes with varying proportions of organic and mineral materials. Part of the organic matter associated with the silt fractions shared features in common with POM. In a laboratory bio-assay, biodegradability of POM varied depending on land use(pasture > arable cropping). We concluded that POM is neither homogeneous nor unique.