SNIFTIRS and electrochemical analysis of modified polythiophenes showed that the introduction of bipyridyl metal centres into a polythiophene backbone leads to polymers where the redox switching of the conducting polymer films occurs via different moieties. The two functionalities, the thiophene backbone and bipyridyl centres, interact closely, exchanging charges during oxidation and reduction of the films. It was also found that the extent of the interaction was dependent on the nature of the substituents R on the thiophene and the conformation of the heteroaromatic rings. SNIFTIRS analysis also showed that the metal centres function as "electronic gates", allowing charge to be inserted into the polymer at reduced potentials. (C) 2003 Elsevier B.V. All rights reserved.