Synthesis and Redox Behavior of Bis(3‐methylthio‐1‐azulenyl)methyl Cations and Dications Connected by 2‐Thienyl and 2,5‐Thiophenediyl Spacers

Abstract

AbstractNovel bis(3‐methylthio‐1‐azulenyl)methyl cations 3a+ and 3b+ and dications 4a2+ and 4b2+ were synthesized by thehydride abstraction reaction of the corresponding hydride derivatives 7a, 7b, 8a, and 8b, which were readily prepared by the acid‐catalyzed condensation reaction of 6a and 6b with the corresponding aldehyde and dialdehyde with DDQ. The pKR+ values of novel cations 3a+ and 3b+ and dications 4a2+ and 4b2+ were determined spectrophotometrically to examine the thermodynamic stability of these carbocations. The redox behavior of the mono‐ and dications was also examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their reversible electrochemical reduction properties, except for the case of dication 4b2+. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions. Dications 4a2+ and 4b2+ were also chemically reduced by Zn powder to afford thienoquinoid compounds 9a and 9b, respectively.