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

Abstract

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.

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…The same research group also reported the DDQ‐mediated synthesis of compounds 180 and 181 , expanded derivatives of 177 containing one or two methylene bridges in the outer hexapyrrole rim . Another spectacular case of multiple intramolecular oxidative aromatic coupling involving eight pyrrole units to form a twisted aza‐PAH containing two unusual N‐doped heptagons was revealed by Uno and co‐workers …”

“…[186] Another spectacular case of multiple intramolecular oxidative aromatic coupling involving eight pyrrole units to form at wisted aza-PAH containing two unusual N-doped heptagons was revealed by Uno and coworkers. [187] Osuka and co-workers reported yet another example of an efficient intramolecular oxidative coupling of pyrrole rings (Figure 14). Tetrapyrrole [8]circulene analogue 182 was prepared by employing aso-called "fold-in" strategy, [188] which is am ethod developed earlier by Stępień and co-workers to construct strained macrocycles by contraction of the larger, less-strained precursors.…”

Excited‐State Symmetry Breaking in an Aza‐Nanographene Dye

“…With the growing number of unprecedented curved aza‐nanographenes published within the last five years, this study offers both general understanding of their optical behavior and guidelines for designing solvatofluorochromic dyes possessing large fluorescence quantum yield across the solvent polarity scale.…”

Stereocontrolled Synthesis of Chiral Heteroaromatic Propellers with Small Optical Bandgaps

“…[14][15][16][17][18][19][20][21][22][23][24][25][26][27] Inclusion of heteroatoms or nonbenzenoid rings in such systems can have ap rofound effect on their electronic and chiroptical characteristics.H owever,s uch modifications are synthetically challenging and thus rarely attempted. Hexapyrrolohexaazacoronene [HPHAC(1); Figure 1] [28,29] and its analogues [30][31][32][33][34] are attractive heteroaromatic cores for helical expansion because of their tunable optical and electrochemical signatures and the variety of functionalization methods now available. Additionally,H PHACs ystems are obtained by oxidative annulation of hexapyrrolylbenzene (HPB), which is inher-ently ap ropeller-shaped molecule,a nd adopts ac hiral (though non-rigid) conformation with D 6 symmetry.…”