Functional metallomacrocycles and their polymers. 25. Kinetics and mechanism of the biomimetic oxidation of thiol by oxygen catalyzed by homogeneous polycarboxyphthalocyaninato metals

Abstract

The oxidation of 2-mercaptoethanol (RSH) catalyzed by (polycarboxyphthalocyaninato) metal acid (M-papc, M=Fe(III), Co(II), Ni(II), Cu(II), pa=−(COOH) 2 , −(COOH) 4 , −(COOH) 8 ) in the presence of molecular oxygen has been studied in aqueous homogeneous solution at pH 7.0 and at 25 o C. The catalytic effects of M-papc have been determined the oxygen consumption in the reaction mixture with a Warburg respirometer. The central metal ions and the number of carboxylate ions on M-papc affected the catalytic activities for the aerobic oxidation of RSH. (Octacarboxyphthalocyaninato) iron (III) and -cobalt (II) are remarkably effective catalysts. (Dicarboxyphthalocyaninato) metals and Ni(II) ― as well as Cu(II) ― phthalocyanine derivatives are less effective catalysts. The kinetics of the aerobic oxidation catalyzed by (octacarboxyphthalocyaninato) iron (III) and -cobalt (II) have been characterized in terms of a bisubstrate Michaelis-Menten rate law (k 5 =600-800 min −1 , at pH 7.0, 25 o C