Electrochromically and Photochromically Controllable Multifunctional OligoEDOT Derivatives

Multifunctional conjugated co‐oligomers with electrochromic and photochromic properties are synthesized by a cross‐coupling polycondensation reaction between bis(trialkylstannyl)‐3,4‐ethylenedioxythiophene and a phenylene or thienylene derivative bearing a photoresponsive dithienylethene (DE) moiety. The oligomer exhibits a reversible change between the neutral and oxidized states of the main chain upon electrochemical doping and dedoping. Furthermore, the oligomer shows reversible photoisomerization between the open and closed forms of the DE group in the side chain upon irradiation with ultraviolet and visible light. As a consequence, the oligomers possess various electronic structures that show cyclically reversible changes via the electrochemical doping and dedoping, and photoisomerization, producing four types of colored films in an oligomer system. Among the four types of electronic structures, only the dopant‐free oligomer film with the open form of the DE group shows visible fluorescence. To the best of our knowledge, the present conjugated oligomers are the first to exhibit both electrochromic and photochromic functions with cyclical reversibility.