Novel conducting polymers incorporating covalently bound metal–tetraazamacrocycle complexes

Abstract

The syntheses of a tetraazamacrocycle functionalized at nitrogen with a pendant 3-thiophene, 1-[2-(3-thienyl)ethyl]-1,4,8,11-tetraazacyclotetradecane (cyclamN-CH₂CH₂-thiophene), and its complexes with Ni^II and Cu^II, are described. Electro-oxidation of the pure Ni^II complex in acetonitrile electrolytes afforded only soluble oligomers. Novel conducting polymer-modified electrodes were fabricated, however, by electro-copolymerization of the Ni^II complex with 3-methylthiophene. These are unusual in that both the metal centre [Ni^II–Ni^III at + 1.15 V (saturated calomel electrode)] and the conducting polymer backbone show stable, reversible redox behaviour, with no apparent oxidative degradation of the poly(thiophene) backbone. The Ni^II–Ni^III redox behaviour appears unaffected by incorporation into the conducting polymer matrix. However, the Ni^II–Ni^I wave, observed at – 1.40 V in solution, is entirely suppressed in the polymer, which at that potential is an electronic insulator.