N-Doped Zigzag-Type Aromatic Truncated Cone Belts

Zigzag aromatic hydrocarbon belts, ultrashort segments of zigzag carbon nanotubes, have been fascinating in the chemistry community for more than a half century because of their aesthetically appealing molecular nanostructures and tantalizing applications. Precise introduction of heteroatoms of distinct electronegativity and electronic configuration can create various heterocyclic aromatic nanobelts with novel physical and chemical properties. Here, we report the synthesis of unprecedented N-doped zigzag-type aromatic belts, belt[n]pyrrole[n]pyridines (n = 6-8), from multiple intramolecular C_aryl-C_aryl homocoupling reactions of readily available azacalix[n](3,5-dibromopyridine)s. These compounds adopt globally π-conjugated belt structures and display unique photophysical and electrochemical properties. The truncated cone cavity of belt[8]pyrrole[8]pyridine was used as the outstanding host to form very stable 2:1 encapsulation complexes with fullerenes. This work opens a new avenue to the rational design and efficient synthesis of aromatic belts of distinct topological structures and tailor-made properties, which are invaluable in applications in materials and supramolecular chemistry.