ELECTROCATALYTIC OXIDATION OF CYSTEINE BY MOLYBDENUM(V) PHTHALOCYANINE COMPLEXES

Chemically modified electrodes, constructed by incorporating oxomolybd enum(V) phthalocyanine (OMo(V)(OH)Pc, Pc = phthalocyanine dianion) int o graphite powder were used to catalyse the oxidation of cysteine. Sol ution catalysis of cysteine by oxomolybdenum(V) tetrasulfophthalocyani ne, [OMo(V)(OH)TSPc](4-), was also investigated. A considerable reduct ion in overpotential for cysteine oxidation was observed. Cysteine oxi dation occurred at 0.26 and 0.28 V vs. Ag\AgCl for catalysis by OMo(V) (OH)Pc and [OMo(V)(OH)TSPc](4-) respectively as opposed to 0.77 V vs. Ag\AgCl observed on CoPc chemically modified electrodes. The anodic pe ak currents vary linearly with cysteine concentration in the range 0.0 2 to 0.08 mol dm(-3) and 0.008 to 0.02 mol dm(-3) for [OMo(V)(OH)TSPc] (4-) and OMo(V)Pc respectively.