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 degrees. This electron-rich pi-system showed four reversible oxidation peaks. Despite the nonplanar structure, the Huckel aromaticity owing to a peripheral pi-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.