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Buckminsterfullerene synthesis
Maryam Ebrahimi
Chem 7530
Feb. 7th, 2006
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Outline
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Discovery of C60 & Smalley's apparatus
Natural Sources
Different Techniques for Synthesis of C60
Rational Synthesis of Buckminsterfullerene
Significance of Fullerene yield
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Discovery of C60
For generations diamond and graphite were considered to be the only pure
forms of carbon. In 1985, a group of discoverers (R.F. Curl, R.E.Smalley &
H.W.Kroto) found a third form, C60 which was named Buckminsterfullerene
owing to the structural similarity of C60 to geodesic domes designed by
Buckminster Fuller.
C60, is the exact structure of a soccer ball, having both pentagonal and
hexagonal rings arranged in an alternating fashion .
This 5/6-ring cage provides remarkable stability
In fact, C60 is the smallest fullerene for which all pentagons are isolated.
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Smalley's apparatus for generating
and detecting buckyball
H. W. Kroto, J. R. Heath, S. C. O'Brien, R. F. Curl and R. E. Smalley "C(60)
Buckminsterfullerene" (1985) Nature, 318, 6042, 162-163
http://www.chem.wisc.edu/~newtrad/CurrRef/BDGTopic/BDGtext/BDGBucky.html
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How the apparatus works?
● generate long chain carbon molecules so that their spectroscopic fingerprints
could be measured.
● a laser is aimed at a rotating graphite disk in a helium-filled vacuum chamber.
● lasers deliver short, high energy bursts of energy in the form of light. The
rapid, intense heating of the graphite surface by the laser enables many of the
C-C bonds in the graphite to rupture.
● carbon atoms and small clusters of carbon atoms sputter from the graphite
surface. Thus, the energy of the light produced in the laser is used to break the
bonds between atoms in graphite, a process that involves the conversion of light
energy to chemical energy.
● The high energy C atoms and small clusters of carbon atoms cool and collide in
the He atmosphere yielding new bonding arrangements of C atoms.
● These new materials can be characterized by different instruments like mass
spectrometers & nuclear magnetic resonance spectrometers.
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H. W. Kroto, J. R. Heath, S. C. O'Brien, R. F. Curl and R. E. Smalley "C(60)
Buckminsterfullerene" (1985) Nature, 318, 6042, 162-163
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Do fullerenes form spontaneously
in nature?
● It is believed that fullerenes form in the cosmos due
to evidence that polyynes (such as HC7N) are
produced by ambient starlight photofragmentation of
dust, and the fact that carbon species of 30-100
atoms are formed on carbon photofragmentation
● Fullerenes also appear to form spontaneously on earth
whenever carbon condenses, i.e. any sooting flame
H. W. Kroto, “Space, Stars, C60, and Soot”, Science 242, 1139-1145 (1988)
J. B. Howard, et al., Fullerenes C60 and C70 in flames, Nature 352, 139-141 (1991)
R. E. Smalley, “Self-Assembly of the Fullerenes”, Acc. Chem. Res. 25, 98-105 (1992)
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● This is the first natural example of carbon in the "Bucky
Ball" configuration of C-60 carbon atoms. It is called
"shungite" - which is the Russian name for this type of
graphite. It came from the Shunga River, in Karelia,
Russia. Shungite is a rare Precambrian carbonaceous
rock. This black rock contains small veins of stacked
spheres that are precisely buckminsterfullerene in their
configuration.
http://www.sciencemall-usa.com/c60buc.html
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Different Techniques
for Synthesis of C60
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Graphite vaporization (Smalley's technique)
Resistive heating of graphite
Graphite arching
Pyrolysis of hydrocarbons
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Resistive Heating of Graphite
(K-H method)
● The first macroscopic quantities of C60 were
produced in 1990 by what is now known as the
Kratschmer-Huffman (K-H) method.
● Instead of vaporizing carbon with a laser, a graphite
rod was slowly evaporated using resistive heating.
● This slower, more ‘gentle’ technique allowed for
more control over the conditions that make C60
formation possible.
W. Krätschmer,et al., “Solid C60: a new form of carbon”, Nature 347, 354-357 (1990)
F. Diederich,et al., “The Higher Fullerenes: Isolation and Characterization of C76,
C84, C90, C94, and C70O, an Oxide of D5h-C70”, Science 252, 548-551 (1991)
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Graphite Arching (Haufler et. al.)
● The apparatus for this technique is comprised of
graphite electrodes over which an ac or dc arc is
produced, generating the necessary carbon soot.
● The graphite rod and disk are connected to an
external 60 Hz ac power source. The graphite is
vaporized with a 100-200A current at an rms
voltage of 10-20V.
● Not shown in this diagram is the helium source
that condenses the carbon.
● The graphite arcing technique is currently the
most commonly used technique and is also used
commercially.
R. E. Smalley, “Self-Assembly of the Fullerenes”, Acc. Chem. Res. 25, 98-105 (1992)
R. E. Smalley, et al., “Efficient Production of C60 (Buckminsterfullerene), C60H36, and the
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Solvated Buckide Ion”, J. Phys. Chem. 94, 8634-8636 (1990)
Pyrolysis of Hydrocarbons
Hydrocarbons (mostly PAH) as starting material
mechanism of formation of a partial C60 cage from naphthalene
● The removal of hydrogen, as well as the curling of joined
rings into a cage structure
● Two proposed mechanism by Taylor and Baum
R. Taylor, G. J. Langley, H. W. Kroto, & D. R. M. Walton, “Formation of C60 by pyrolysis
of naphthalene”, Nature 366, 728-731 (1993)
T. Baum, S. Löffler, P. Löffler, P. Weilmünster, K. H. Homann, Ber. Bunsenges. Phys.
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Chem. 96, 841-857 (1992)
Pyrolysis of Hydrocarbons
The decomposition of a hydrocarbon to produce fullerene-containing soot can be
accomplished through a variety of means such as:
● flame combustion flame (combustion of benzene),
● laser,
● a general heat source such as a torch or a tube furnace (pyrolysis of naphthalene).
Typical pyrolysis apparatus
R. Taylor, G. J. Langley, H. W. Kroto, & D. R. M. Walton, “Formation of C60 by
pyrolysis of naphthalene”, Nature 366, 728-731 (1993)
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Separation of Fullerenes from Soot
Fullerene soot
Toluene extraction
Toluene extract
with C60 to ~C100
C60 pure
Toluene-insoluble
soot
Alumina,
hexane/toluene
(95:5)
~C100 to ~C250
C70 pure
Alumina,
hexane/toluene
(95:5)
Higher fullerenes C76, C78, C84, traces of C90, C94, residual C70
2-3 HPLC runs on C18 reversed
phase CH3CN/toluene (1:1)
C76 pure
C2v-C78 pure
D3-C78 pure
C84, mixture of at
least 2 isomers
Fullerene separation scheme
F. Diederich, & R. L. Whetten, “Beyond C60: The Higher Fullerenes”, Acc. Chem.
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Res. 25, 119-126 (1992)
Rational Synthesis of
Buckminsterfullerene
http://www.trincoll.edu/depts/chem/toms/REUsite/facproj/mitzel/mitzel.html
Tom Mitzel, Trinity College, Connecticut
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Significance of Fullerene yield
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Lubrication
Superconductors
Semiconductors
Photoconductors
Optical Limiters
Atom Encapsulation
R. E. Smalley, “Self-Assembly of the Fullerenes”, Acc. Chem. Res. 25, 98-105 (1992)
Wang, “Photoconductivity of fullerene doped polymers”, Nature 356, 585-587 (1992)
http://www.science.org.au/nova/024/024box02.htm, Australian Academy of Science
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