Plausible Mechanisms of the Fenton-Like Reactions, M = Fe(II) and Co(II), in the Presence of RCO₂^– Substrates: Are OH^• Radicals Formed in the Process?

DFT calculations concerning the plausible mechanism of Fenton-like reactions catalyzed by Fe­(II) and Co­(II) cations in the presence of carboxylate ligands suggest that hydroxyl radicals are not formed in these reactions. This conclusion suggests that the commonly accepted mechanisms of Fenton-like reactions induced oxidative stress and advanced oxidation processes have to be reconsidered

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

<div><p>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.</p></div

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

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

Manganese Carbonate (Mn₂(CO₃)₃) as an Efficient, Stable Heterogeneous Electrocatalyst for the Oxygen Evolution Reaction

With the growing population and energy demand, there is an urgent need for the production and storage of clean energy obtained from renewable resources. Water splitting electrocatalytically is a major approach to obtain clean H2. The efficiency, stability, and slow kinetics of anode materials developed so far do not fit the commercial application of the water oxidation reaction. To develop an efficient energy conversion catalyst, particularly for the oxygen evolution reaction (OER) herewith, Mn2(CO3)3 was electrodeposited on a Ni foam (NF) electrode surface by the chronoamperometric technique. The deposited Mn2(CO3)3/NF was characterized using various surface characterization techniques. The electrochemical behavior of the Mn2(CO3)3/NF-deposited electrode toward the OER was studied using electrochemical methods in KOH (pH 14) and NaHCO3 (pH 8.3) electrolytes. The Mn2(CO3)3/NF electrode showed a lower overpotential than CO3/NF and NF electrodes in the KOH/NaHCO3 media. The Mn2(CO3)3/NF electrode performs high electrocatalytic water oxidation with an overpotential of 360 mV at a current density of 10 mA·cm–2. This overpotential is much lower than those of CO3/NF (460 mV) and bare NF (520 mV), with good long-term stability in the KOH medium without any catalytic degradation after 100 CV cycles and 15 h chronoamperometric studies. The stability of the electrodeposited Mn2(CO3)3 on the NF electrode was determined by X-ray photoelectron spectroscopy. Thus, the Mn2(CO3)3/NF catalyst is suitable for the oxygen evolution reaction

Different oxidation mechanisms of Mn^II(polyphosphate)_n by the radicals and

<p>The kinetics and mechanisms of the oxidation of and of by the biological relevant radicals and were studied. The rate constants of the oxidations by both radicals are faster for the complexes than for the complexes, though the redox potentials predict the reverse order of reactivity. Surprisingly, the results point out that these two radicals react via different mechanisms. Thus, the increase in the concentration of the ligands decreases the rate constants of the oxidations by , whereas it increases the rate constants of the oxidation by . These results point out that these radicals behave differently though both are inner-sphere oxidants. The plausible mechanisms of reaction of these radicals are discussed.</p

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

<p>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.</p