Efficient synthesis and redox behavior of a series of 6-alkyl-2-phenylazulenes

Three new members of 6-alkyl-2-phenylazulene (nPA with n being the number of carbon atoms in the 6-alkyl chain) homologous series, 3a (n=4), 3b (n=6), and 3d (n=10), expected to show smectic E (SmE) phase as a mesophase below fusion, has been synthesized by Pd(PPh3)4 catalyzed Suzuki–Miyaura cross-coupling reaction of the corresponding 6-alkyl-2-bromoazulenes. The redox behavior of 3a, 3b, and 3d including that of their 6-octyl and 6-hexadecyl derivatives 3c (n=8) and 3e (n=16), the synthesis was reported previously, was studied in detail by voltammetric and electrochromic analyses. As the results, amphoteric redox properties with a significant color change were revealed by the nPA homologous series 3a–e, which would be attracted to the application for the device fabrication of the molecular materials.

Graphical abstractAmphoteric redox behavior of 6-alkyl-2-phenylazulenes with a significant color change under electrochemical conditions was revealed by voltammetric and electrochromic analyses.Figure optionsDownload full-size imageDownload as PowerPoint slide