Highly Strained Electron-Rich Molecular Bowl and Nanographene

Introducing two pyrrole rings at the armchair edges of perylene creates the small, electron-rich molecular bowl 1, which can be viewed as a nitrogen-doped end-cap of C₇₀. Despite numerous attempts since 2008, its synthesis has been hindered by strain and synthetic challenges. In this study, we present the synthesis and property analysis of molecular bowl 1 and its dimer, the wavy-shaped nanographene 2. Substituents on nitrogen atoms significantly affect the bowl depth, intermolecular interactions, and supramolecular behaviors. Consequently, the butyl-substituted molecular bowl 1 a forms unusual polar crystals with all bowls oriented similarly, suggesting potential pyroelectric or ferroelectric applications. Due to the electron-rich nature, compounds 1 exhibit significantly strong binding affinity towards fullerene, with 1 a forming a sandwich structure with C₇₀. Furthermore, neutral bowls 1 display counter-rotating ring currents similar to corannulene, while their dications exhibit global anti-aromaticity. The wavy-structured nanographene 2 demonstrates two continuously reversible oxidation processes, and its dication 2²⁺ shows remarkably high stability under ambient conditions. In summary, this work constructs a small, electron-rich molecular bowl and its nanographene dimer, highlighting their exceptional properties, promising applications, and potential as foundations for future advanced nanostructure fabrication.