Photo- and Electrochemical Properties of Linked Ferrocene and Viologen Donor−Acceptor-Type Molecules and Their Application to Electrochromic Devices

Abstract

This is a report on the electrochemical and optical properties of a new type of linked system of ferrocene (Fc) and viologen (V 2+ ) units, Fc−(CH 2 ) 4 −V 2+ −R (Fc−V 2+ ). The cyclic voltammogram and absorption spectra have revealed that Fc and V 2+ units are little effected by the nonconjugated bridge, −(CH 2 ) 4 −, since differences in electrochemical and optical properties between linked and nonlinked Fc and V 2+ systems are not observed, in that both systems have similar redox and absorption characteristics. The linked Fc−V 2+ system, however, showed higher UV resistance. Using Fc−V 2+ dye and a polymeric solid electrolyte (PSE), we succeeded in fabricating a large-area quasi-solid-state electrochromic cell (EC cell). This cell has shown excellent homogeneous coloration, and its EC properties can be explained in a simple graphical way based on the diffusion of redox species Fc−V •+ and Fc + −V 2+ . Further, the EC cell fabricated with Fc−V 2+ has shown excellent durability and was shown to be well-suited for all outdoor applications.