Various hexabenzocoronenes have been investigated in
supramolecular electronics. They are known to
self-assemble into a
columnar phase. One derivative in particular forms
carbon nanotubes with interesting electrical properties. The columnar phase in this compound further organises itself into sheets, which ultimately roll up like a carpet to form multi-walled nanotubes with an outer diameter of 20
nanometers and a wall thickness of 3 nm. In this geometry, the stacks of coronene disks are aligned with the length of the tube. The nanotubes have sufficient length to fit between two
platinum nanogap
electrodes produced by
scanning probe nanofabrication and are 180 nm apart. The nanotubes as such are insulating, but, after one-electron
oxidation with
nitrosonium tetrafluoroborate (), they conduct electricity.
Synthesis Organic synthesis of a hexabenzocoronene starts with an
Aldol condensation reaction of
dibenzyl ketone with a
benzil derivative to give a substituted
cyclopentadienone. A
Diels–Alder reaction with
alkyne and subsequent expulsion of
carbon monoxide gives a
hexaphenylbenzene. The adjacent pairs of benzene rings undergo oxidative
electrocyclic reactions and aromatization by oxidation by
iron(III) chloride in
nitromethane. : ==References==