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

Abstract

Palladium-catalyzed coupling techniques have been used to prepare a series of 1,4-bis[2-(3,4-ethylenedioxy)thienyl]-2,5-dialkoxybenzenes which can be polymerized chemically or electrochemically. The polymers have been characterized by electrochemistry, spectroelectrochemistry, in situ EPR electrochemistry, and in situ conductivity. The highly electron rich nature of these polymers leads to extremely low oxidation potentials (E 1/2.p= −0.15 to −0.35V vs. Ag/Ag +). Mild polymerization conditions can be used, resulting in fewer side reactions and more stable polymers; e.g. only a 25% loss in electro activity occurs over 3000 redox cycles when switching polymer 2c. These polymers are stable over a broad potential range, allowing them to be used as modified electrode materials; for example, ferrocene can be repeatedly oxidized and reduced on the polymer surface. In situ EPR electrochemistry and in situ conductivity were used to better understand the polymer redox processes, which are solvent-dependent. Maximum conductivity is attained in the bipolaronic state, but stable polarons can be formed in certain solvents. The polymers are electrochromic, reversibly switching from red to blue upon oxidation with electronic bandgaps at ca. 1.9 eV.