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Issue 9, 2003
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Azo dye oxidation with hydrogen peroxide catalysed by manganese 1,4,7-triazacyclononane complexes in aqueous solution

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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, O[double bond, length as m-dash]MnVL(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.

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

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Publication details

The article was received on 28 Jan 2003, accepted on 10 Mar 2003 and first published on 03 Apr 2003


Article type: Paper
DOI: 10.1039/B301026K
Org. Biomol. Chem., 2003,1, 1568-1577

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

    B. C. Gilbert, J. R. Lindsay Smith, M. S. Newton, J. Oakes and R. Pons i Prats, Org. Biomol. Chem., 2003, 1, 1568
    DOI: 10.1039/B301026K

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