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

作者：Gilbert BC^*; Smith JRL; Newton MS; Oakes J; Prats RPI

来源：Organic and Biomolecular Chemistry, 2003, 1(9): 1568-1577.

DOI：10.1039/b301026k

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 (Me(3)TACN). 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 (MnL)-L-III(OH)(3), O=(MnL)-L-v(OH)(2) and (MnL)-L-IV(OH)(3) (L = Me(3)TACN) (cf. the reactions of peroxidase enzymes). ESI-MS results provide evidence for the formation and reaction (with the dye) of (MnL)-L-IV(OH)(3). With the mononuclear manganese complex (MnL)-L-IV(OMe)(3), there is a short lag-phase attributed to perhydrolysis by HO2- followed by the same catalytic cycle.

• 出版日期2003-5-7