Remarkably high catalytic activity of the RuIII(edta)/H2O2 system towards degradation of the azo-dye Orange II

Abstract

The Ru(III)(edta)/H(2)O(2) system (edta(4-) = 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 [H(2)O(2)], [Orange II] and pH. Spectral analyses and kinetic data point towards a catalytic pathway involving the rapid formation of [Ru(III)(edta)(OOH)](2-) followed by the immediate subsequent degradation of Orange II prior to the conversion of [Ru(III)(edta)(OOH)](2-) to [Ru(IV)(edta)(OH)](-) and [Ru(V)(edta)(O)](-)via homolysis 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.

Predominant role of grafted iron(III) Schiff-base complex in oxidation of gaseous and aqueous reactants: A visible light responsive photocatalyst

“…In this case, the distinct applications, especially as a heterogeneous catalyst, is a consequence of their unique textural properties such as great porosity, crystallinity and thermal stability [7]. Moreover, this group of materials has been exploited in many of organic transformation reactions as homogeneous catalysts [8,9]. However, in a homogeneous mixture, the recyclability of the catalysts from the reaction mixture is a very demanding task, which, in the case of heterogeneous catalysts, a simple filtration can prevail on this obstacle [10].…”

RuIII(edta) mediated oxidation of azide in the presence of hydrogen peroxide. Azide versus peroxide activation

“…Based on the above experimental facts and by analogy with the reported mechanism [6][7][8] that follows the oxidation of the azide anion under the specified conditions. In the case of oxidation as a function of the azide concentration shown in Fig.…”

“…2,3 The 'edta 4− ' ligand is somewhat comparable in its donor character to many metallo-enzymes, which make use of carboxylate and amine donors from amino acids to bind to the metal centre. Further, Ru III (edta) type complexes not only afford a range of accessible oxidation states, but also they are remarkably labile towards aqua-substitution reactions, 1 7 are not responsible for effecting the oxidation of these thiocompounds. [4][5][6] Oxidation of the mentioned thio-compounds occurs through the direct attack of the oxidant H 2 O 2 on the coordinated S-atom of the substrate.…”

“…It is noteworthy that the rate of formation of [Ru V (edta)- the efficiency of the overall catalytic process, 7 and it should be pH dependent as the substitution behavior of the Ru(edta) catalyst complex is highly pH controlled. 7 We have performed the above stated oxidation in a broad pH range to assess the effect of pH on the catalytic oxidation reaction.…”

“…7 We have performed the above stated oxidation in a broad pH range to assess the effect of pH on the catalytic oxidation reaction. A much longer induction period was observed at pH 1.6 as compared to that observed at pH 4.9.…”