Assembly of Supramolecular Nanotubes from Molecular Triangles and 1,2-Dihalohydrocarbons

Precise control of molecular assembly
is a challenging goal facing
supramolecular chemists. Herein, we report the highly specific assembly
of a range of supramolecular nanotubes from the enantiomeric triangular
naphthalene­di­imide-based macrocycles (RRRRRR)- and (SSSSSS)-NDI‑Δ and a class of
similar solvents, namely, the 1,2-dihalo-ethanes and -ethenes (DXEs).
Three kinds of supramolecular nanotubes are formed from the columnar
stacking of NDI‑Δ units with a 60° mutual rotation
angle as a result of cooperative [C–H···O] interactions,
directing interactions of the [X···X]-bonded DXE chains
inside the nanotubes and lateral [X···π] or [π···π]
interactions. They include (i) semiflexible infinite nanotubes formed
in the gel state from NDI‑Δ and (E)-1,2-dichloroethene,
(ii) rigid infinite nonhelical nanotubes produced in the solid state
from NDI‑Δ and BrCH2CH2Br, ClCH2CH2Br, and ClCH2CH2I, and
(iii) a pair of rigid tetrameric, enantiomeric single-handed (P)- and (M)-helical nanotubes formed in
the solid state from the corresponding (RRRRRR)-
and (SSSSSS)-NDI‑Δ with ClCH2CH2Cl. In case (i), only the electron-rich CC
double bond of (E)-1,2-dichloroethene facilitates
the gelation of NDI‑Δ. In cases (ii) and (iii), the lengths
of anti-DXEs determine the translation of the chirality
of NDI‑Δ into the helicity of nanotubes. Only ClCH2CH2Cl induces single-handed helicity into the nanotubes.
The subtle interplay of noncovalent bonding interactions, resulting
from the tiny structural variations involving the DXE guests, is responsible
for the diverse and highly specific assembly of NDI‑Δ.
This research highlights the critical role that guests play in constructing
assembled superstructures of hosts and offers a novel approach to
creating supramolecular nanotubes.