Effects of complexation of oppositely charged water-soluble cobaltphthalocyanines on catalytic mercaptoethanol autoxidation

In order to elucidate the different promoting effects polycations have on cobalt(II) phthalocyanine-catalyzed autoxidn. of 2-mercaptoethanol, the properties of mixts. of oppositely charged water-sol. cobalt(II) phthalocyanines were studied. The contribution of polycation-induced dimerization of the catalyst was investigated with combinations of cobalt(II) phthalocyanine-tetrakis(trimethylammonium) iodide (CoPc[N(CH3)3I]4) and cobalt(II) phthalocyanine-tetrasodium sulfonate [CoPc(NaSO3)4]. A mixt. of equimolar amts. of both phthalocyanines shows an increase in reaction rate for 2-mercaptoethanol autoxidn. as compared with an equal amt. of one of the catalyst species sep. The highest activities are achieved when the pos. charges of the pos. phthalocyanine just match the charges of the neg. CoPc(NaSO3)4. A mixt. of cobalt(II) phthalocyanineoctacarboxylic acid (CoPc(COOH)8) and CoPc[N(CH3)3I]4 exhibits its max. activity at a ratio of 1:2, indicating the formation of a trimeric catalyst species. Visible light spectroscopy showed that these effects can be ascribed to the formation of aggregates of the phthalocyanines. Addn. of a poly(quaternary ammonium) salt, a so-called ionene, to a stoichiometric complex of oppositely charged phthalocyanines results in an increase in the catalytic activity due to substrate enrichment. The activities of an ionene-contg. equimolar CoPc[N(CH3)3I]4/CoPc(NaSO3)4 system were never as high as those achieved for a conventional CoPc(NaSO3)4/2,4-ionene system, probably as a result of the strong bonding between the two oppositely charged mols., which prevents a break-up of the dimeric species. In order to achieve a high catalytic activity, one should enhance the formation of aggregates of CoPc(NaSO3)4, which probably will break up after the first reaction step