Substituted manganese phthalocyanines as bleach catalysts: synthesis, characterization and the investigation of de-aggregation behavior with LiCl in solutions

Abstract

This study reported the oxidative degradation of morin dye with hydrogen peroxide catalyzed by manganese phthalocyanines as low temperature bleaching catalysts for laundry applications. A novel series of manganese phthalocyanines (MnPcs) have been synthesized starting with tetrakis[4-(1,3-dioxolan-2-yl)phenoxy)]phthalocyaninatomanganese(III) (2) prepared by the cyclotetramerization of 4-[4-(1,3-dioxolan-2-yl)phenoxy]-phthalonitrile (1). De-protection of acetal groups of 2 to the aldehyde group in an acetic acid/FeCl3 system yielded the tetrakis(4-formylphenoxy)phthalocyaninatomanganese(III) (3). The condensation of 3 with 3-(dimethylamino)-1-propylamine gave Schiff base-substituted Mn(III)Pc 4. Finally, quaternization of the dimethylamino functional groups with the reaction of methyl iodide produced cationic manganese(III) phthalocyanine 5 which was soluble in both DMSO and water. These new MnPcs were characterized by the combination of spectroscopic methods (FT-IR, UV–Vis and mass spectroscopy). The effects of structural variables of the prepared compounds (2–5) on their dissolution in the solvent system LiCl/DMAc-DMF-DMSO and THF were also investigated. Degradation of morin at 25 and 40 °C in the presence of catalysts (2–5)/H2O2 combination in basic medium was examined by online spectrophotometric method, and the bleaching activities of the prepared compounds have been evaluated comparatively. It was found that the prepared catalysts have more effective bleaching performance at 25 °C than tetraacetylethylenediamine (TAED) which is a bleach activator commercially used in powder detergent formulations.