handbook of carbon, graphite, diamond and fullerenes

The Fullerene Molecules 359
Unlike the sp 3 or sp 2 hybridizations, the fullerene hybridization is not
fixed but has variable characteristics depending on the number of carbon
atoms in the molecule. This number varies from twenty for the smallest
geometrically (but not thermodynamically) feasible fullerene, the C 20 - to
infinity for graphite (which could be considered as the extreme case of all
the possible fullerene structures). It determines the size of the molecule as
well as the angle 0 of the basic pyramid of the structure (the common angle
to the three o-bonds). The number of carbon atoms, the pyramidization
angle (0 - 90°), and the nature of the hybridization are related and this
relationship (in this case the s character in the n-orbital) is given in Fig.
15.3J 5 ]
The bond lengths of the fullerenes are reported as 0.145 +/-0.0015 nm
for the bonds between five- and six-membered rings, and 0.140 +/- 0.0015
nm for the bond between the six-membered rings.! 6 )
5 10 15
Pyramidalization Angle (6ajI-90)°
Figure 15.3. Hybridization of fullerene molecules as a function of pyramidization
angle (©CTJT; - 90°). Scwi is the common angle of the three a bonds.! 5 '