handbook of carbon, graphite, diamond and fullerenes

360 Carbon, Graphite, Diamond, and Fullerenes
2.2 Characteristics of the Fullerene Molecules
General Characteristics. The fullerene structure is unique in the
sense that the molecules are edgeless, chargeless, and have no boundaries,
no dangling bonds, and no unpaired electron. These characteristics
set the fullerenes apart from other crystalline structures such as graphite or
diamond which have edges with dangling bonds and electrical charges.! 2 '
Such features allow these molecules, and particularly the C^ which is
the most symmetrical, to spin with essentially no restraint at a very high
rate.! 3 '
The Fullerene Family. Many fullerene structures are theoretically
possible, some with hundreds of atoms. Five have been unambiguously
identified and structurally characterized so far: the C^, C^, G^, C^, and
At one end of the fullerene family is the C20. the simplest
structure, which is composed of twelve pentagons with
no hexagon and with a pyramidization angle of 18°. All
its atoms would have the sp 3 configuration but it is
thermodynamically unstable.! 8 '
The first stable fullerene and the first to be discovered is
the CgQ. It is the dominant molecule with sixty carbon
atoms arranged so that they form twenty hexagons, in
addition to the necessary twelve pentagons, giving it the
appearance of a soccer ball (known as a football outside
the U.S.A. and U.K.). Each hexagon is connected to
alternating pentagon and hexagon, and each carbon
atom is shared by one pentagon and two hexagons. Its
hybridization is partially sp 3 and partially sp 2 , with a
pyramidization angle of 11.6°. It is shown schematically
in Fig. 15.4. The C^ has a calculated diameter of 0.710
+/- 0.007 nm. It is intensely purple in apolar solvents.' 7 '! 8 '
The higher fullerenes are shown schematically in Fig.
1 5.S.! 7 ' The Cy0 is the second most prominent fullerene.
It has a rugby-ball appearance and is has a deep orangered
color in solution. The Cj6 is c/7/ra/with a structure
consisting of a spiraling arrangement of pentagons and
hexagons.' 91 it has a bright yellow-green color in solution