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A series of three-ring heteroaromatic compounds consisting of a pyridine central ring and thiophene, selenophene, or N-methylpyrrole outer rings, and their polymers have been investigated. Differences in redox potentials and electronic absorbance spectra of the threering monomers have been interpreted with the aid of HOMO and LUMO energies from ab initio calculations. Both p-and n-doping of the polymers were investigated electrochemically in acetonitrile. In all cases, the p-doped states were not stable, and measured conductivities were well below intrinsic values. In most cases, the n-doped states were more stable, but conductivities were very low.

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Bithiazole-containing polymers prepared by electrochemical polymerization of 5,5'-bis(2-thienyl)-4,4'-dimethyl-2,2,-bithiazole (la) and 5,5'-bis(3-methoxy-2-thienyl)-4,4,-dimethyl-2,2'-bithiazole (lb) exhibit good conductivities and stable electrochemistry. The redox potential of poly-la (co. 0.8 V vs SCE) is between the values reported for polythiophene and poly(a-bithiophene). The methoxy substituents on the thiophenes of lb increase its solubility and lower the redox potential of the resulting polymer. The morphology, redox potential, and conductivity of poly-lb are strongly influenced by the electrolyte used in the polymerization. The maximum conductivity of poly-lb is co. 0.01 S cm-1, comparable to that of poly(a-terthiophene). It therefore appears that the nitrogen atoms in the conduction pathway have little influence on the redox potential and conductivity of thiophene/thiazole copolymers.