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Azo dye oxidation with hydrogen peroxide catalysed by manganese 1,4,7-triazacyclononane complexes in aqueous solution

Gilbert, B.C., Lindsay Smith, J.R., Newton, M.S., Oakes, J. and Pons i Prats, R. (2003) Azo dye oxidation with hydrogen peroxide catalysed by manganese 1,4,7-triazacyclononane complexes in aqueous solution. Organic and Biomolecular Chemistry, 1 (1). pp. 1568-1577. ISSN 1477-0520

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Abstract

A kinetic and mechanistic study is reported of the oxidation of a number of azonaphthol dyes with hydrogen peroxide in aqueous solution, catalysed by some mono and dinuclear manganese(IV) complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3TACN). The results of UV-Vis investigations, augmented by EPR and ESI-MS studies, are described for a series of experiments in which concentrations, pH and ionic strength have been varied. The reactions are characterised by an induction period followed by a relatively rapid oxidation. For the dinuclear manganese complex 2, these are consistent with an initial perhydrolysis of the manganese complex involving both the dye anion and HO2–, to give mononuclear manganese species and the operation of a catalytic cycle incorporating MnIIIL(OH)3, OMnVL(OH)2 and MnIVL(OH)3(L = Me3TACN)(cf. the reactions of peroxidase enzymes). ESI-MS results provide evidence for the formation and reaction (with the dye) of MnIVL(OH)3. With the mononuclear manganese complex MnIVL(OMe)3, there is a short lag-phase attributed to perhydrolysis by HO2– followed by the same catalytic cycle.

Item Type: Article
Institution: The University of York
Academic Units: The University of York > Chemistry (York)
Depositing User: York RAE Import
Date Deposited: 12 Mar 2009 11:57
Last Modified: 12 Mar 2009 11:57
Published Version: http://dx.doi.org/10.1039/b301026k
Status: Published
Publisher: Royal Society Chemistry
Identification Number: 10.1039/b301026k
URI: http://eprints.whiterose.ac.uk/id/eprint/7130

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