Liquid crystal perylene diimide films characterized by electrochemical, spectroelectrochemical, and conductivity versus potential measurements

Electrochemical techniques are used to characterize thin polycrystalline films of a liquid crystal perylene diimide. Cyclic voltammograms show evidence for strong attractive interactions between the perylene diimide molecules and suggest that the film undergoes two structural rearrangements to accommodate reduction to the anionic and dianionic states. Spectroelectrochemical measurements support this interpretation. The redox conductivity of the film as a function of electrochemical potential was measured with the use of interdigitated array electrodes. The conductivity reaches the semiconducting level before the occurrence of the first noticeable reduction wave. The maximum conductivity, 4.4 x 10(-2) Slcm, occurs when the film is reduced by 1 equiv of electrons, in contrast to the expectation that this state should be a Mott insulator.