Multicolored Electrochromism of a Poly{1,4-bis[2-(3,4-ethylenedioxy)thienyl]benzene} Derivative Bearing Viologen Functional Groups

1,4‐Bis[2‐(3,4‐ethylenedioxy)thienyl]‐2,5‐bis[6‐(1′‐butyl‐4,4′‐bipyridyl)hexyloxy]benzene tetrahexafluorophosphate (BEDOTPh‐2V) was synthesized and electropolymerized to form a viologen‐bearing conductive polymer [P(BEDOTPh‐2V)] film on an electrode surface. This polymer exhibits multicolor electrochromic behavior: it is highly transparent light‐blue P(BEDOTPh1.7+‐2V2+) at 1.0 V (vs. Ag/Ag+), pale‐bisque P(BEDOTPh0.6+‐2V2+) at 0.1 V, magenta P(BEDOTPh0‐2V2+) at –0.5 V, purple P(BEDOTPh0‐2V •+) at –0.9 V, and crimson P(BEDOT0‐2V0) at –1.4 V. Since both the viologen pendant and the polymer backbone have cathodic coloring characteristics and their redox‐potential ranges do not overlap each other, the dual electrochromic action provides more plentiful electrochromic colors compared to simple poly{1,4‐bis[2‐(3,4‐ethylenedioxy)thienyl]‐2,5‐dialkoxybenzene}. Chemical incorporation of viologen into poly{1,4‐bis[2‐(3,4‐ethylenedioxy)thienyl]benzene} provides plentiful multicolor electrochromism ranging from highly transparent light blue to four other colors, since both the pendant and the backbone have cathodic coloring characteristics and their redox‐potential ranges do not overlap.