Flexible Phenanthracene Nanotubes for Explosive Detection

Phenanthracene
nanotubes with arylene-ethynylene-butadiynylene
rims and phenanthracene walls are synthesized in a modular bottom-up
approach. One of the rims carries hexadecyloxy side chains, mediating
the affinity to highly oriented pyrolytic graphite. Molecular dynamics
simulations show that the nanotubes are much more flexible than their
structural formulas suggest: In 12, the phenanthracene units act as hinges that flip the two macrocycles
relative to each other to one of two possible sites, as quantum mechanical
models suggest and scanning tunneling microscopy investigations prove.
Unexpectedly, both theory and experiment show for 13 that the three phenanthracene hinges are deflected
from the upright position, accompanied by a deformation of both macrocycles
from their idealized sturdy macroporous geometry. This flexibility
together with their affinity to carbon-rich substrates allows for
an efficient host–guest chemistry at the solid/gas interface
opening the potential for applications in single-walled carbon nanotube-based
sensing, and the applicability to build new sensors for the detection
of 2,4,6-trinitrotoluene via nitroaromatic markers is shown.