Yael Albo

Polyoxometalates entrapped in sol–gel matrices for reducing electron exchange column applications

Abstract Electron exchange columns were developed by utilizing the redox properties of polyoxometalates (POMs) entrapped in silica matrices via the sol–gel route. The properties of the columns strongly depend on the composition of the precursors used to prepare the matrices. The columns exhibit good reversibility and are the first ‘reducing’ electron exchange columns ever prepared. They are also the first columns where both the matrix and the entrapped redox agent are inorganic compounds. This increases their stability. However, the redox properties of the entrapped POMs in the matrices are affected by the composition of the matrices.

Polyoxometalates entrapped in sol-gel matrices as electron exchange columns and catalysts for the reductive de-halogenation of halo-organic acids in water

Abstract Halo-organic acids in aqueous solutions are widespread pollutants. An enormous number of technologies have been proposed for their elimination. In this context, reducing electron exchange columns seem to be an optimal solution for their degradation, as they do not introduce any new chemical into the solution to be purified. The electron exchange columns used in this study consist of entrapped polyoxometalates (POMs) in silica sol-gel matrices that were used as the reducing medium for the reductive de-halogenation of Br3CCO2−, Cl3CCO2−, BrCH2CO2− and ClCH2CO2−. The same matrices were also applied as catalysts for the reduction of the investigated halo-acetates by BH4−. Surprisingly, the results indicate that the mechanisms of de-halogenation of Br3CCO2−, Cl3CCO2−, BrCH2CO2− and ClCH2CO2− differ from each other.

Copper(II) catalyses the reduction of perchlorate by both formaldehyde and by dihydrogen in aqueous solutions

Abstract During an effort to synthesize the trans-III-copper(II) complex with 1,4,8,11-tetramethyl-pyro-phosphonate-1,4,8,11-tetra-aza-cyclo-tetradecane, using only perchlorate salts, it was noted that the perchlorate is reduced to chloride. Analysis of the reactions leading to this surprising result points out that Cu(H2O)42+ catalyzes the reduction of perchlorate by H2 and by CH2O. These reactions are slow at room temperature and ambient pressures. A plausible mechanism, supported by DFT calculations, is proposed pointing out that the role of CuH+ under mild conditions cannot be ignored.

Design of a ligand suitable for sensitive uranyl analysis in aqueous solutions

Several ligands were designed as plausible reagents for the spectrophotometric analysis of uranyl in aqueous solutions. The ligand = 3,3′-(ethane-1,2-diylbis(methylazanediyl))bis(methylene)bis(4-hydroxybenzenesulfonate) was found to fit best the requirements. The results point out that carboxylate substituents compete with the phenolate substituents as binding sites to the central uranium cation and therefore decrease the usefulness of ligands containing both carboxylate and phenolate substituents as analytical spectrophotometric reagents.