Doubly Linked Azulene Dimer: A Novel Non‐benzenoid Isomer of Perylene
Ryoji Hatakenaka, Kazuma Urabe, So Ueno, Mitsuaki Yamauchi, Yoshiyuki Mizuhata, Hiroko Yamada, Yuji Mikata, Shin Kamijo, Fumito Tani, Toshihiro Murafuji
Abstract
We report herein the synthesis of an unprecedented isomer of perylene, dicyclohepta[cd,fg]-as-indacene bearing two phenyl groups (1-Ph) by the nickel-mediated intramolecular homocoupling of a 4,4'-biazulene derivative (2). The X-ray crystallographic analysis and theoretical calculations revealed that 1-Ph adopts a unique helically twisted geometry although the local aromaticity of azulene moieties was preserved. The double covalent linkage of the two azulene skeletons imparts significant orbital interaction, which affords near-infrared (NIR) absorption (up to 1720 nm) and remarkable redox behaviors despite its closed-shell electronic structure. The optical band gap of 1-Ph is calculated to be 0.72 eV from its absorption onset, which is one of the narrowest values among the hitherto reported air-stable non-benzenoid PAHs. Furthermore, the thin-film of 1-Ph serves as a p-type semiconductor. Our study offers fundamental insights into not only the aromaticity with the nonalternant topologies of 1-Ph but also its potential application in novel organic electronics.