EFFECTS OF COMPLEXATION OF OPPOSITELY CHARGED WATER-SOLUBLE COBALTPHTHALOCYANINES ON THE CATALYTIC MERCAPTOETHANOL AUTOXIDATION

In order to elucidate the different promoting effects polycations have on the cobalt (II) phthalocyanine catalyzed autoxidation of 2 -mercap toethanol, the properties of mixtures of oppositely charged water-solu ble cobalt (II) phthalocyanines were studied. The contribution of poly cation induced dimerization of the catalyst was investigated by means of combinations of cobalt (II) phthalocyanine-tetra(trimethylammonium) iodide (CoPc[N(CH3)3I]4) and cobalt (II) phthalocyanine-tetrasodium s ulphonate (CoPc(NaSO3)4). A mixture of equimolar amounts of both phtha locyanines shows an increase in reaction rate for the 2-mercaptoethano l autoxidation as compared with an equal amount of one of the catalyst species separately. The highest activities are achieved when the posi tive charges of the positive phthalocyanine just match the charges of the negative CoPc(NaSO3)4. A mixture of cobalt (II) phthalocyanine-oct acarboxylic acid (CoPc(COOH)8) and CoPc[N(CH3)3I]4 exhibits its maximu m activity at a ratio of 1:2, indicating the formation of a trimeric c atalyst species. Visible light spectroscopy showed that these effects can be ascribed to the formation of aggregates of the phthalocyanines. Addition of a poly (quaternary ammonium) salt, a so-called ionene, to a stoichiometric complex of oppositely charged phthalocyanines result s in an increase in the catalytic activity due to substrate enrichment . The activities of an ionene containing equimolar CoPc[N(CH3)3I]4/CoP c (NaSO3)4 system were never as high as those achieved for a conventio nal CoPc(NaSO3)4/2,4-ionene system, probably as a result of the strong bonding between the two oppositely charged molecules, which prevents a break-up of the dimeric species. Conclusively, in order to achieve a high catalytic activity it is favourable to enhance the formation of aggregates of CoPc(NaSO3)4, which probably will break up after the fir st reaction step.