Figure-of-Eight Helicene Carbon Nanohoop with Möbius Topology

We present design and synthesis of a new class of chiral figure-of-eight carbon nanohoops by integrating [6]helicene into [7]cycloparaphenylene. The stereogenic [6]helicene unit endows the helicene carbon nanohoop with chiroptical properties and configurational stability typical for higher helicenes, while the presence of radially conjugated oligo-p-phenylene moiety provides the optoelectronic properties similar to meta[8]cycloparaphenylene, such as emission of visible light with a high quantum yield. We discovered that the synthesized helicene carbon nanohoop possesses a Mobius topology in solution and confirmed this hypothesis by variable-temperature ¹H NMR spectroscopy and DFT calculations. Our results suggest that a single helicene stereogenic unit and high molecular strain are sufficient to induce Mobius topology in molecular nanocarbon systems.