Reactions of V-Substituted Polyoxometalates with L-Cysteine |
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Authors: | Bineta Keita Israel Martyr Mbomekalle Pedro de Oliveira Alireza Ranjbari Yves Justum Louis Nadjo Denis Pompon |
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Affiliation: | (1) Laboratoire de Chimie Physique, UMR 8000, CNRS, Université Paris-Sud, Batiment 350, 91405 Orsay Cedex, France;(2) Present address: Department of Chemistry, City College of The City University of New York, New York, NY 10031, USA;(3) Laboratoire d’Ingénierie des Proteines Membranaires, Centre de Génétique Moléculaire du CNRS, UPR 9061, 91198 Gif-sur-Yvette Cedex, France |
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Abstract: | Three polyoxometalates (POMs), (X=P or As) and, in their oxidized and reduced forms, were selected for direct reaction or electrocatalytic reaction with L-cysteine, because they have the most negative formal potentials among those POMs active for the desired reaction. The good linearity of the UV–Visible calibration curve obtained for the reaction of α2-[P2VVW17O62]7− with L-cysteine indicates both a simple 1:1 stoichiometry for the process and the possibility to select a wavelength domain in which the one-electron reduced forms of this POM is the only strongly absorbing species in the mixture. Another general result among the three selected POMs is the existence, in each example, of a sharp isosbestic point during the recording of individual spectrakinetics using a photodiode array system. The kinetics could be fitted accuretely to a mono-exponential rate equation and the rate constants were determined. Electrocatalysis of the oxidation of L-cysteine was carried out in the presence of α2-[H4P VIVW17O62]9− as an example. The rate constant measured by chronocoulometry for this system compares favourably with that extracted from stopped flow experiments.Dedicated in honor of Professor Michael T. Pope on the occasion of his retirement. |
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Keywords: | Polyoxometalates vanadium cysteine stopped flow electrochemistry electrocatalysis |
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