PEROXIDE DECOLORATION OF AZO DYES CATALYZED BY POLYETHYLENE GLYCOL-LINKED MANGANESE HALOGENATED PORPHYRINS

Polyethylene glycol (PEG)-linked manganese halogenated porphyrins (Cha rt 1) catalyzed oxidation of azo dyes (Chart 2) by H2O2 under mild con ditions such as pH 8.0 at 25 degrees C especially when imidazole was p resent, causing the decoloration of azo dyes. The decoloration of azo dyes by synthetic manganese porphyrins under mild conditions was first reported. The decoloration rate depended on the structures of the por phyrins, in which the largest rate was observed in the presence of PEG -MnDCPP. The decoloration may be contributed by radical species rather than electrophilic species, consistent with the side-chain oxidation of toluene. Kinetics on polyethylene glycol-linked manganese porphyrin -catalyzed decoloration of C.I. Acid Orange 7 by hydrogen peroxide rev ealed that the decoloration was contributed at the oxidation process b y manganese porphyrins with hydrogen peroxide in the polymer domain ra ther than the complex-formation process between manganese porphyrins a nd azo dyes.