Directing the Crystallization of Dehydro[24]annulenes into Supramolecular Nanotubular Scaffolds

The self-assembly of a series of
dehydro[24]­annulene derivatives
into columnar stacks has been examined for its latent ability to form
π-conjugated carbon-rich nanotubular structures through topochemical
polymerizations. We have studied the parameters affecting self-assembly,
including the nature of the substituent and crystallization conditions,
using 10 different dehydro[24]­annulene derivatives. In particular,
hydrogen-bonding interactions through carbamate groups were found
to be especially useful at directing the formation of nanotubular
supramolecular assemblies. We have also evaluated the electronic coupling
between neighboring dehydro­annulene molecules within these supramolecular
assemblies. Density functional calculations on the stacked supramolecular
nanotube assemblies show that transfer integrals vary considerably
between the three columnar assemblies, ranging from moderate to high
(59–98 meV for the highest occupied molecular orbitals, 63–97
meV for the lowest unoccupied molecular orbitals), depending on the
local molecular topology. In addition, the dehydro[24]­annulene derivatives
afforded distinct architectures in the crystal, including nanochannel
arrays, sheets with solvent-filled pores, and lamellae. This work
is an essential step toward a controlled formation of covalently linked
carbon-rich nanostructures generated from molecular precursors with
a latent diacetylene reactivity.