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past feature
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Bucky Balls Take A New
Twist
A new family of
bucky balls that break the
isolated-pentagon rule have been
discovered after the detection of an
unexplained peak in the mass spectrum of
metallofullerenes.
Scientists at Virginia Tech and several
other institutions have discovered a
family of fullerene molecules that differ
from those previously reported where even
numbers of carbon atoms link to form
pentagons each isolated by hexagons to
form a spherical cage. The new fullerene
contains pentagons that share one side and
resemble an angular figure eight.
The new molecule is possible due to an
earlier discovery by the university's
researchers to place four metal atoms
inside a fullerene of 80 carbon atoms
(C80), creating endohedral
metallofullerenes. The new structure has
only 68 carbon atoms, which are stabilized
by the three metal atoms. The three metal
atoms have a nitrogen atom core.
The researchers discovered that they had
created the rule-breaking metallofullerene
when they conducted a detailed study of
the same mixtures that yielded the first
metallofullerenes. Having already
discovered that nitrogen will allow metal
atoms to be inserted into fullerenes, an
unexplained peak was noticed in the mass
spectum of the metallofullerenes. The
component was isolated and studied by NMR
spectoscopy. Although the NMR data
suggested a new structure, it wasn't
sufficient proof for publication.
So Virginia Tech undergraduate student
Greg Rice and visiting scholar Jim Duchamp
were able to make about a half of a
milligram of the material. When attempts
to get a crystal structure failed, the
team turned to Patrick Fowler of the
University of Exeter. He used computer
modeling to determine that of 6,332 ways
to assemble fullerenes, only 11 structures
agreed with the data and only one
structure was stable.
Once the structure had been identified,
the new fullerene was isolated to contain
scandium that would aid its
characterization by NMR studies. The
Virginia Tech researchers have since
created a family of C68 endohedral
metallofullerenes by inserting other
metals.
The study appears in the November 23rd
issue of Nature.
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