Catalytic activity of iron and cobalt phthalocyanines wrapped in poly(peptide) for autoxidation of thiol

Abstract

The autoxidation of 2-mercaptoethanol was studied by using poly(peptide)-wrapped unsubstituted metal phthalocyanine as a polymer catalyst, where the poly(peptide)s consisted of L-lysine, L-glutamic acid and β-alanine and the metal was iron or cobalt. In spite of the lack of catalytic activity of poly(peptide) or metal phthalocyanine alone, the poly(peptide)-wrapped metal phthalocyanine possessed catalytic activity for the autoxidation of 2-mercaptoethanol. In particular, higher catalytic activity was observed in the polymer catalyst with the higher content of L-lysine residue. The catalytic system was found to obey Michaelis-Menten kinetics with respect to substrate concentration. The rate constant k 2 and the Michaelis-Menten constant K m were determined from a Lineweaver-Burk plot. The overall activation energy E a for the autoxidation was also determined from an Arrhenius plot over the temperature range 10–40°C. Overall, the present polymer catalysts exhibited enzyme-like behavior for the autoxidation of 2-mercaptoethanol.