Synthesis, Structures, and Properties of Core-Expanded Azacoronene Analogue: A Twisted π‑System with Two N‑Doped Heptagons

A core-expanded,
pyrrole-fused azacoronene analogue containing
two unusual N-doped heptagons was obtained from commercially available
octafluoronaphthalene and 3,4-diethylpyrrole in two steps as a heteroatom-doped
nonplanar nanographene. Full fusion with the formation of the tetraazadipleiadiene
framework and the longitudinally twisted structure was unambiguously
confirmed by single-crystal X-ray diffraction analysis. The edge-to-edge
dihedral angle along the acene moiety was 63°. This electron-rich π-system
showed four reversible oxidation peaks. Despite the nonplanar structure,
the Hückel aromaticity owing to a peripheral π-conjugation
in the dicationic state was concluded from the bond-length alternation
and nucleus-independent chemical shift (NICS) and anisotropy of the
induced current density (ACID) calculations.