No abstract

Electrochemical behaviors of selected Dawson-type polytungstates including 2-K10[P2W15Mo2O61box] where the symbol [box] designates a vacant site, alpha2-K7[Fe(OH2)P2W15Mo2O61], alpha2-K8[Cu(OH2)P2W15Mo2O61], alpha1- and alpha2-K8[Cu(OH2)P2W17O61], alpha2-K8[Cu(OH2)P2W13Mo4O61], and alpha2-K8[Cu(OH2)P2W12Mo5O61] were investigated by cyclic voltammetry (CV) coupled with the electrochemical quartz microbalance (EQCM), and the results were completed by atomic force microscopy (AFM) observations of the electrodeposited films. The electrocatalytic abilities of these polyoxometalates (POMs) in the reduction of dioxygen, hydrogen peroxide, and NOx were also assessed by CV and EQCM. It turns out that the remarkable electrocatalysis obtained at the reduction potential of Mo centers within alpha2-K8[Cu(OH2)P2W15Mo2O61], but in a domain where Cu2+ is not deposited, benefits from the assistance of the copper center because such catalysis could not be observed in the absence of Cu2+. EQCM confirms that no copper deposition occurs under the experimental conditions used. Analogous behaviors are encountered in the electrocatalytic reduction of nitrite where assistance by the presence of the Cu2+ center induced the observation of catalysis at the potential location of Mo centers. Finally, the reduction of nitrate is triggered by electrodeposited copper but was remarkably favored by the presence of molybdenum atoms within these polyoxometalates (POMs). All of the results converge to indicate a cooperative effect between the Mo and Cu centers within these POMs. The various results suggest that copper deposition from these POMs should give morphologically different surfaces. AFM studies confirm this expectation, and the observed morphologies and sizes of particles were rationalized by taking into account the role of the POM skeleton and its atomic composition in the electrodeposition process.

No abstract

Preparation of N-acyl sulfonamides (2a-j), (3a-m), (5a-f) and cyclic imides (3n-r)Under nitrogen atmosphere, a mixture of sulfonamide (1 mmol), acylating agent (2 mmol) and Cs 5 HP 2 W 18 O 62 catalyst (5 mmol %) in water (2 mL), was stirred at room temperature to obtain (2a-j), (3a-m), (5a-f) and under reflux for (3n-r). Reaction was monitored by TLC. After completion of the reaction, the catalyst was removed by filtration. The filtrate was washed by water (10 mL) and extracted with EtOAc (3x15 mL). The combined organic layers were dried over anhydrous Na 2 SO 4 , then the solvent was evaporated in vacuum, and the crude compound was purified by flash chromatography (Merck silica gel 60 H, CH 2 Cl 2 /MeOH, 9:1) to afford the corresponding products.. NMR data of N-acyl sulfonamide derivatives (2a-j) N-(N-butylsulfamoyl)acetamide (2a)

The synthesis, IR , 31 P NMR and cyclic voltammetry characterizations of a new Wells-Dawson-type heteropolyanions which contains iron HFe 2.5 P 2 W 18 O 62 , 23H 2 O and HFe 2.5 P 2 W 12 Mo 6 O 62 , 22 H 2 O are reported. The catalytic activity of these compounds was evaluated through the oxidation of methyl violet dye, by hydrogen peroxide. The influence of different parameters such as the initial pH, the initial H 2 O 2 concentration, the catalyst mass, and the initial dye concentration have been studied.

Keywords: Heteropolyanions / Dawson-type structures / Molybdenum / Transition metal cations / Electrocatalysis Stereospecific routes were followed to synthesize five new Fe 3+ and Cu 2+ -substituted Mo-enriched Dawson-type heteropolyanions as aqueous soluble potassium salts: α 2 -K 7 [Fe(OH 2 )P 2 W 12 Mo 5 O 61 ] and α 2 -K 7 [Fe(OH 2 )P 2 W 13 Mo 4 O 61 ], α 1 -and α 2 -K 8 [Cu(OH 2 )P 2 W 12 Mo 5 O 61 ] and α 2 -K 8 [Cu(OH 2 )-P 2 W 13 Mo 4 O 61 ]. The substituted species as well as their immediate lacunary precursors were characterized by IR, UV/

No abstract

No abstract