Functionalized Poly(azulenes) and Their Electrochromic Properties

In this work, five 2‐ or 6‐ functionalized azulenes are electropolymerized to form azulene homopolymers. All five poly(azulenes) films exhibited electrochromism, with a two‐stage oxidation corresponding to the formation of the azulenium cation and the polaron, respectively. Electron‐donating groups at the 2‐position of azulene were found to greatly increase the poly(azulenes) film stability, with retention of optical contrast about four times as much as the 6‐alkylazulene analogue. This result demonstrates the potential of azulene functionalization as a strategy to improve the long‐term stability of electropolymerized azulenes, enabling applications in both optoelectronics as well as in ion selective electrodes. 2‐Functionalized azulenes were prepared using a C−H activation method, and subsequently electropolymerized to form electrochromic devices. Spectroelectrochemical analysis revealed that the poly(azulenes) with electron donating groups at the 2‐position exhibited superior cycling stability compared to those prepared from 6‐alkyl azulenes.