This work reports on the syntheses of new thiophene tetra substituted cobalt, manganese and zinc phthalocyanine (CoTETPc, (CI)MnTETPc and ZnTETPc) complexes. The redox processes due to the thiophene substituent on the ring of the metallophthalocyanines (MPcs) were observed, in addition to Pc ring and metal (for Co and Mn complexes) based redox activity. The electrocatalylic activity of the CoTETPc complex adsorbed on glassy carbon electrode (GCE) by drop/dry-thennal annealing was investigated using L-Cysteine. The modified electrode was stable to repetitive use without any signs of deactivation by oxidation products and was used to determine L-cysteine at concentrations between 0.0015 and 1 mM in pH 4 aqueous conditions. (C) 2005 Elsevier Ltd. All rights reserved.