Synthesis of a Carbon Nanocone by Cascade Annulation

More than 50 years
have passed since the first observation of graphitic
cones in the pyrolysis of carbon. However, to date there has been
no report in the literature on the synthesis of such carbon allotropes.
Here we present the first synthesis of a carbon nanocone, which comprises
a pentagon encircled by 30 hexagons, by means of a palladium-catalyzed
cross-coupling reaction. In this synthetic approach, 15 C–C
bonds were constructed from a cone-shaped aromatic scaffold, corannulene,
and five naphthalene dicarboximide moieties through a cascade of [3
+ 3] and [4 + 2] annulations. The conical geometry of the first synthetic
carbon nanocone was confirmed by X-ray crystallography. The optical
and electronic properties of this graphitic cone were elucidated by
UV/vis and fluorescence spectroscopy and cyclic voltammetry.