Precision Nanotube Mimics via Self-Assembly of Programmed Carbon Nanohoops

The
scalable production of homogeneous, uniform carbon nanomaterials
represents a key synthetic challenge for contemporary organic synthesis
as nearly all current fabrication methods provide heterogeneous mixtures
of various carbonized products. For carbon nanotubes (CNTs) in particular,
the inability to access structures with specific diameters or chiralities
severely limits their potential applications. Here, we present a general
approach to access solid-state CNT mimic structures via the self-assembly
of fluorinated nanohoops, which can be synthesized in a scalable,
size-selective fashion. X-ray crystallography reveals that these CNT
mimics exhibit uniform channel diameters that are precisely defined
by the diameter of their nanohoop constituents, which self-assemble
in a tubular fashion via a combination of arene-pefluoroarene and
C–HF interactions. The nanotube-like assembly of these
systems results in capabilities such as linear guest alignment and
accessible channels, both of which are observed in CNTs but not in
the analogous all-hydrocarbon nanohoop systems. Calculations suggest
that the organofluorine interactions observed in the crystal structure
are indeed critical in the self-assembly and robustness of the CNT
mimic systems. This work establishes the self-assembly of carbon nanohoops
via weak interactions as an attractive means to generate solid-state
materials that mimic carbon nanotubes, importantly with the unparalleled
tunability enabled by organic synthesis.