Low oxidation potential conducting polymers based on 1,4-bis[2-(3,4-ethylenedioxy)thienyl]-2,5-dialkoxybenzenes

Palladium-catalyzed coupling techniques have been used to prepare series of 1,4-bis[2-(3,4-ethylenedioxy)thienyl]-2, which can be polymerized chemical ly or electrochemically. The polymers have been characterized by electroche mistry, spectroelectrochemistry, in situ EPR electrochemistry, and in situ conductivity. The highly electron rich nature of these polymers leads to ex tremely low oxidation potentials (E-1/2p = -0.15 to -0.35V vs. Ag/Ag+). Mil d polymerization conditions can be used, resulting in fewer side reactions and more stable polymers; e.g. only a 25% loss in electroactivity occurs ov er 3000 redox cycles when switching polymer 2c. These polymers are stable o ver a broad potential range, allowing them to be used as modified electrode materials; for example, ferrocene can be repeatedly oxidized and reduced o n the polymer surface. In situ EPR electrochemistry and in situ conductivit y were used to better understand the polymer redox processes, which are sol vent-dependent, Maximum conductivity is attained in the bipolaronic state, but stable polarons can be formed in certain solvents. The polymers are ele ctrochromic, reversibly switching from red to blue upon oxidation with elec tronic bandgaps at ca. 1.9 eV.