Search

The RuIII(edta)/H2O2system (edta4−= ethylenediaminetretaacetate) was found to degrade the azo-dye Orange II at remarkably high efficiency under ambient conditions. Catalytic degradation of the dye was studied by using rapid-scan spectrophotometry as a function of [H2O2], [Orange II] and pH. Spectral analyses and kinetic data point towards a catalytic pathway involving the rapid formation of [RuIII(edta)(OOH)]2−followed by the immediate subsequent degradation of Orange II prior to the conversion of [RuIII(edta)(OOH)]2−to [RuIV(edta)(OH)]−and [RuV(edta)(O)]−viahomolysis and heterolysis of the O–O bond, respectively. The higher oxidation state Ru(iv) and Ru(v) complexes react three orders of magnitude slower with Orange II than the Ru(iii)-hydroperoxo complex. In comparison to biological oxygen transfer reactions, the Ru(edta) complexes show the reactivity order Compound 0 Compounds I and II. [ABSTRACT FROM AUTHOR]

The kinetics of reduction of [RuIII(edta)pz]−(edta4−= ethylenediaminetetraacetate; pz = pyrazine) by thioamino acids (RSH = cysteine, glutathione) resulting in the formation of a red [RuII(edta)pz]2−species (λmax= 462 nm) has been studied spectrophotometrically using both conventional mixing and stopped-flow techniques. The time course of the reaction was followed as a function of [RSH], pH, temperature and pressure. Alkali metal ions were found to have a positive influence (K+> Na+> Li+) on the reaction rate. Kinetic data and activation parameters are interpreted in terms of a mechanism involving outer-sphere electron transfer between the reaction partners. A detailed reaction mechanism in agreement with the spectral and kinetic data is presented. [ABSTRACT FROM AUTHOR]

Reported in this paper is the first example of a ruthenium complex, [RuIII(edta)(H2O)]−(edta = ethylenediaminetetra-acetate), that catalyzes the oxidation of hydroxyurea in the presence of H2O2, mimicking the action of peroxidase or catalase and shedding light on their possible mechanism of action. [ABSTRACT FROM AUTHOR]

The reactions of [RuIII(edta)(H2O)]− (1) (edta = ethylenediaminetetraacetate) with tert-butylhydroperoxide (tBuOOH) and potassium hydrogenpersulfate (KHSO5) were studied kinetically as a function of oxidant concentration and temperature (10–30 °C) at a fixed pH of 6.1 using stopped-flow techniques. Kinetic results were analyzed by using global kinetic analysis techniques. The reaction was found to consist of two steps involving the rapid formation of a [RuIII(edta)(OOR)]2− intermediate, which subsequently undergoes heterolytic cleavage to form [(edta)RuVO]−. Since [(edta)RuVO]− was produced almost quantitatively in the reaction of 1 with the hydroperoxides tBuOOH and KHSO5, the common mechanism is one of heterolytic scission of the O–O bond. The water soluble and easy to oxidize substrate 2,2′-azobis(3-ethylbenzithiazoline-6-sulfonate (ABTS), was employed to substantiate the mechanistic proposal. Reactions were carried out under pseudo-first order conditions for [ABTS] ≫ [hydroperoxide] ≫ [1], and were monitored as a function of time for the formation of the one-electron oxidation product ABTS˙+. The detailed suggested mechanism is consistent with the reported rate and activation parameters, and discussed in reference to the results reported for the reaction of [RuII(edta)(H2O)]− with H2O2. [ABSTRACT FROM AUTHOR]

The reaction of [RuIII(edta)(H2O)]− (1) (edta = ethylenediaminetetraacetate) with hydrogen peroxide was studied kinetically as a function of [H2O2], temperature (5–35 °C) and pressure (1–1300 atm) at a fixed pH of 5.1 using stopped-flow techniques. The reaction was found to consist of two steps involving the rapid formation of a [RuIII(edta)(OOH)]2− intermediate which subsequently undergoes parallel heterolytic and homolytic cleavage to produce [(edta)RuV=O]− (45%) and [(edta)RuIV(OH)]− (55%), respectively. The water soluble trap, 2,2′-azobis(3-ethylbenzithiazoline-6-sulfonate) (ABTS), was employed to substantiate the mechanistic proposal. Reactions were carried out under pseudo-first conditions for [ABTS] ≫ [HOBr] ≫ [1], and were monitored as a function of time for the formation of the one-electron oxidation product ABTS˙+. A detailed mechanism in agreement with the rate and activation parameters is presented, and the results are discussed with reference to data reported for the corresponding [FeIII(edta)(H2O)]−/H2O2 system. [ABSTRACT FROM AUTHOR]

[RuIII(edta)(OH2/OH)]1−/2− (edta = ethylenediaminetetraacetate) inhibits protein tyrosine phosphatase (PTP) at physiological pH values in a mechanism that involves binding of the Cys residue of the catalytic domain of the enzyme and similar interactions may be important in the anti-cancer properties of the active forms of many Ru pro-drugs. [ABSTRACT FROM AUTHOR]