Dror Shamir

The reaction between the peroxide VO(η2-O2)(pyridine-2-carboxylate)·2H2O and FeIIaq is not a Fenton-like reaction

Abstract The reduction of VO(η2-O2)(pyridine-2-carboxylate) by Fe(H2O)62+ proceeds via formation of the transient complex (pyridine-2-carboxylate)(O)VV(μ-η2 : η2-O2)FeII(H2O)32+ that is transformed via intramolecular electron transfer into (pyridine-2-carboxylate)(O)VIV(μ-η2 : η2-O2)FeIII(H2O)32+. The latter transient reacts with another Fe(H2O)62+ to yield 2Fe(H2O)63+ + VVO(OH)(pyridine-2-carboxylate)+. These results point out that: (1) VV does not activate the η2 bound peroxide toward the Fenton-like reaction. In this aspect, VV differs from FeIII in (H2O)5Fe–OOH2+ and (2) transients of the type LmMn(μ-η2 : η2-O2)M′L″l have to be considered in the reductions of complexes of η2-bound peroxides.

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.

ions do not catalyze the decomposition of peroxomonosulfate

According to literature reports, the spontaneous decomposition of peroxomonosulfate is catalyzed by transition metal ions, e.g. by Co(II), Fe(II), Fe(III), and Ni(II). The present study demonstrates that this is not the case for at pH ~ 1.9. This observation is of importance as peroxomonosulfate is used as an oxidant in a variety of important processes. The reasons for this exception are discussed.

Acceleration of the corrosion reaction of magnesium by Fenton reagents

Abstract Magnesium alloys have attracted increased attention for a variety of applications, chief among which are alternative energy and medical implants. The use of biodegradable implants in the complex system of the human body, in which myriad reactions occur, must consider the potential effects of the body’s natural chemical reactions on implant corrosion rates. The aim of this study was to elucidate the synergistic effects of pure Mg and Mg alloys on the Mg corrosion reaction with reagents that participate in the Fenton reaction. We corroborated our results with six different measurement methods (hydrogen evolution rate [HER], gas chromatography [GC], potentiodynamic polarization, inductively coupled plasma [ICP] spectrometry, Auger electron spectroscopy [AES], and scanning electron microscope [SEM]). The results point out that the corrosion and hydrogen evaluation rates of Mg were elevated by the addition of Fenton reagents, divalent iron and hydrogen peroxide, to a saline solution. In the context of Mg-based alloy medical implant development and use, this observation is significant. Graphical Abstract

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.