A Nitrogen-Containing Graphenic Buckybowl for Photocatalysis and Assembly With Fullerenes

A nitrogen-containing graphenic buckybowl (3N-HBC) has been synthesized through pentagonal cyclization at the bay positions of hexa-peri-hexabenzocoronene (p-HBC) using a Pd-catalyzed dehydrogenative cycloamination as a key step. The incorporation of three pyrrole rings to the periphery of the bowl endows it with strong electron-rich character, showing three reversible oxidations in cyclic voltammetry (CV), and thus could be progressively oxidized into cationic radical and high-charged species upon gradual addition of the oxidant. Interestingly, the cationic radical was also generated by acids, which could be significantly accelerated by light, whether under an air or inert atmosphere. 3N-HBC exhibits interesting properties that arise from its electron-rich character and the unique curved geometry. 3N-HBC proved to be a superior organic photocatalyst for the conversion of 2-isocyanobiphenyl to phenanthridine derivatives at 1.0 mol% catalytic loading under blue LEDs irradiation. Furthermore, the electron-donating nature and curved π-surface of 3N-HBC enable its association with fullerenes (C₆₀ and C₇₀) in solution and solid states. This work also demonstrates that nanographene sheets can be bent to π-bowls through the introduction of a few pentagons containing small-sized heteroatoms to their bay regions.