Showing papers by "Debabrata Chatterjee published in 2013"

Selective oxidation of thiourea with H2O2 catalyzed by [RuIII(edta)(H2O)]−: kinetic and mechanistic studies

Abstract: Reported here is the first example of a ruthenium complex, [RuIII(edta)(H2O)]− (edta4− = ethylenediaminetetraacetate), that catalyzes the oxidation of thiourea (TU) in the presence of H2O2. The kinetics and mechanism of this reaction were investigated in detail by using rapid-scan spectrophotometry as a function of both the hydrogen peroxide and thiourea concentrations at pH 4.9 and 25 °C. Spectral analyses and kinetic data clearly support a catalytic process in which hydrogen peroxide reacts directly with thiourea coordinated to the RuIII(edta) complex. HPLC product analyses revealed the formation of formamidine disulfide (TU2) as a major product at the end of the catalytic process, however, formation of other products like thiourea dioxide (TUO2), thiourea dioxide (TUO3) and sulfate was also observed after longer reaction times. Catalytic intermediates such as [RuIII(edta)(OOH)]2− and [RuV(edta)(O)]− were evidently found to be non-reactive in catalyzing the oxidation of thiourea by H2O2 under the specified conditions.

Oxidation of thiocyanate with H2O2 catalyzed by [RuIII(edta)(H2O)]−

Abstract: The [RuIII(edta)(H2O)]− (edta4− = ethylenediaminetetraacetate) complex is shown to catalyze the oxidation of thiocyanate (SCN−) with H2O2 mimicking the action of peroxidases. The kinetics of the catalytic oxidation process was studied by using stopped-flow and rapid scan spectrophotometry as a function of [RuIII(edta)], [H2O2], [SCN−], pH (3.2–9.1) and temperature (15–30 °C). Spectral analyses and kinetic data are suggestive of a catalytic pathway in which hydrogen peroxide reacts directly with thiocyanate coordinated to the RuIII(edta) complex. Catalytic intermediates such as [RuIII(edta)(OOH)]2− and [RuV(edta)(O)]− were found to be non-reactive in the oxidation process under the specified conditions. Formation of SO42− and OCN− was identified as oxidation products in ESI-MS experiments. A detailed mechanism in agreement with the spectral and kinetic data is presented.

Substrate versus oxidant activation in RuIII(edta) catalyzed dye degradation

Abstract: The [RuIII(edta)(H2O)]− (edta4− = ethylenediaminetetraacetate) catalyzed oxidative degradation of methylene blue (MB) in the presence of H2O2 has been achieved. Complete degradation of 0.05 mM MB was noticed within 300 s in the presence of 5.0 μM of Ru(edta) catalyst under ambient conditions. Catalytic degradation of the dye was investigated by using rapid-scan spectrophotometry as a function of [Ru(edta)], [H2O2], [MB] and pH at 25 °C. Spectral analyses and kinetic data point towards a catalytic pathway that involves the rapid coordination of MB to the RuIII(edta) complex to yield [RuIII(edta)(MB)]− species that react directly with hydrogen peroxide. The catalytic-active intermediate [RuIII(edta)(OOH)]2− was also found to be operative at high H2O2 concentration over the Ru(edta) catalyst in effecting MB degradation under the specified conditions.

Actuation and Sensing Studies of a Miniaturized Five Fingered Robotic Hand Made with Ion Polymeric Metal Composite (IPMC)

Abstract: Nafion based IPMC (Ion Polymeric Metal Composites) has been prepared by using a tetraaquaplatinum (II) complex, [Pt (H2O)4])ClO4)2. Fabrication of a robotic mini-hand comprising five micro-fingers of 5 mm length, 400 μm width at a pitch of 600 μm has been achieved by adopting mechanical micro milling' technique. The micro-fingers prepared from the IPMC material were found to actuate successfully under operating voltage of 2.5 V.