A Theoretical Study of Electrochemical and Electrochromic Properties of Novel Viologen Derivatives: Effects of Donors and π-Conjugation.

We propose a linkage approach by merging ambipolar electrochromic (EC) materials in both pi-accept-or-pi (pi-A-pi) and donor-acceptor-donor (D-A-D) configurations and investigated their electrochemical and spectroelectrochemical properties using density functional theory calculations. Here, we considered anthracene, toluene, and pyrene as pi-conjugated molecules, triphenylamine (TPA) as a donor, and viologen as an acceptor moiety for pi-A-pi and D-A-D configurations. We have also explored the substitutional effects in the donor moiety on the overall electrochromism during both oxidation and reduction processes. Here, we mainly focused on the relationship between the structure, substitution of functional groups, electronic and spectral properties, as well as redox potential of the designed monomers. Our calculations indicate that the designed monomers have attractive absorption properties and show clear color switching upon the redox process. We find that the substitution of stronger electron-donating and pi-spacer groups create new absorption peaks in the oxidation states. These designed viologen derivatives will be potential candidates, which can be used in both oxidation and reduction processes for upcoming EC devices.