Zigzag-type N-Heterocyclic Aromatic Belts

Zigzag aromatic hydrocarbon belts, ultrashort segments of zigzag carbon nanotubes, have been fascinating 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 zigzag-type N-heterocyclic aromatic belts, belt[n]pyrrole[n]pyridines (n = 6 - 8), from multiple intramolecular Caryl-Caryl homocoupling reactions of readily available azacalix[n](3,5-dibromopyridine)s. These compounds adopt globally -conjugated belt structures and displayed unique photophysical and electrochemical properties. The spherical frustum cavity of belt[8]pyrrole[8]pyridine was used as the outstanding host to form a very stable 2:1 encapsulation complex with buckminsterfullerene. 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.