Catalytic oxidation of erythrosine by cobalt phthalocyanines

Abstract

Particle and solubilized cobalt(II) phthalocyanines (PCs) have been investigated for their catalytic activity on the oxidative erythrosine decomposition with hydrogen peroxide. Particle PCs show much higher activity than solubilized PCs as a result of a reaction of particle PCs with oxygen molecules that cannot take place with monomeric PCs in solution where a slower reaction with hydrogen peroxide dominates erythrosine decomposition. The high activity of particle PCs seems to be that particle PCs provide a surface where both an oxygen molecule and an erythrosine molecule can coordinate to neighboring cobalt(II) ions, and then the multinuclear cobalt(II) phthalocyanine particle can trigger the decomposition reaction by helping electron transfer from the dye to oxygen. Erythrosine decomposition with particle PCs obeyed Michaelis—Menten kinetics. The activation energies for the catalysis obtained from Arrhenius plots were significantly smaller than those without PCs, that is, particle PCs can be good catalysts for erythrosine oxidation.