Electrochemistry and spectroelectrochemistry of regioregular oligooctylthiophenes

In this work we report on the electrochemical and spectroelectrochemical characterization of the series of α-monochloro substituted regioregular 3-alkylthiophene consisting of 4-8 units of (3-octylthiophene) in solution. The shortest in the series tetramer molecules undergo a fast dimerization process, whereas longer oligomers are not subject to consecutive reactions when oxidized to form the radical cation. Each oxidation stage corresponds to one-electron process; single radical cation and dication are initially produced, which in turn are doubled within each oligomer molecule. Studies of these compounds in solution species were carried out in the thin layer cell on optically transparent electrodes. Clear tendencies are observed with increasing number of thiophene units for the peak potential of the redox reactions and positions of maximum absorbance. Formation of additional electronic bands within the band gap, shifted to the lower energies, has been also observed.