Fullerenes
Structure
and Geometry
- Fullerene is a cage like molecule with the geometry of truncated icosahedron.
- Graphite has layers of infinite number of fused hexagonal rings with
sp2 carbons. The C-C bond length is 1.42 A. (In benzene it is 1.39)
The different layers or sheets are spaced 3.4 A apart. There is no covalent
linkages between the two layers.
- Graphite itself is planar, when it is bombarded with high energy
a carbon atom may knocked out thus converting a hexagon to apentagon.
This causes curvature in the system. If more and more carbon atoms are
removed and pentagons created it results in further increase in curvature.
- Corannulene with five hexagons (benzene rings) around a central pentagon
is an example. It is not planar, the curvature makes it look like a
bowl.
- Removal of more carbon atoms create more pentagons and further increase
in curvature. Eventuallclosure of the sphere occurs resulting in Bucky
ball.
- C60 has 60 vertices with a carbon each.
There are 32 faces, 20 hexagons and 12 pentagons.
- No two pentagons are next to each other.
- The crystals are electrically insulating but doping
with alkali metals create varying phases of insulating conducting
and semi conducting properties.
- Doped fullerides are known to exhibit super conductivity
at low temperatures.
- The discovery of fullerenes created great interest in the scientific
community for, they expected a large number of applications including
among others as super conducting materials, as lubricating materials
as pharmaceuticals and as nano materials.
- Current interest is mainly focus towards nano tubes which are tube
like structures with carbon atoms.
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