Capturing the Labile
Fullerene as C50Cl10
Su-Yuan Xie,1* Fei Gao,1Xin Lu,1Rong-Bin Huang,1
Chun-Ru Wang,2Xu Zhang,3Mai-Li Liu,3Shun-Liu Deng,1
such as C60and its larger homologs, faithfully
satisfy the isolated pentagon rule (IPR) (1),
which governs the stability of fullerenes com-
smaller non-IPR fullerenes (2–9), which are
predicted to have unusual properties because of
their adjacent pentagons and high curvature
(2–8), are so labile that their properties and
reactivity have only been studied in the gas
phase (1–3). Experimental efforts directed at
their bulk synthesis have produced some results
(4–6), but complete structural characterization
is still under way (7). Here we report the syn-
thesis in milligram quantity of a small non-IPR
fullerene C50, a long-sought little sister of
C60(1, 3, 8, 9), through the introduction of
chlorine in the form of carbon tetrachloride
(CCl4) during synthesis from graphite.
C50-containing soot (?90 g) was synthe-
sized in a modified graphite arc-discharge
added to 0.395 atm of helium. The products
in the toluene extract from the soot were
isolated with multistage high-performance
liquid chromatography (11), and ?2 mg of
C50Cl10with 99.5% purity was obtained.
The C50Cl10thus obtained is moderately
soluble in some organic solvents, e.g., car-
bon disulfide, toluene, and benzene, as a
lemon yellow–colored solution.
The comparable mass spectra from the
experiment and a simulation prove the mo-
lecular formula of the isolated substance to
be C50Cl10(Fig. 1, A and B).13C nuclear
magnetic resonance (NMR) measured in
deuterated benzene shows four distinct sig-
nals located at 161.5, 146.6, 143.0, and
88.7 parts per million (Fig. 1C) (11). The
former three signals are characteristic of
sp2-hybridized carbons, whereas the latter
one is typical of sp3-hybridized carbons
bonded to chlorine. Among numerous pos-
sible structures in the C50isomer family (3,
9), only the D5hfullerene has four
unique types of carbon atoms (I to IV, as
illustrated in Fig. 1D). The 10 Cl atoms
should add to the most reactive CIVsites
(that is, to pentagon-pentagon vertex fu-
molecule (Fig. 1D). Indeed, the simulated
13C NMR spectrum (Fig. 1C, inset) of this
Saturn-shaped C50Cl10structure agrees well
with the experimental one (table S1) (11). Ad-
ditionally, the D5hfullerene structure
has been further cocharacterized by a variety of
techniques, including multiple staged mass
spectrometry and infrared, Raman, ultraviolet-
visible, and fluorescence spectroscopies (figs.
S1 to S6 and tables S2 and S3) (11).
Fullerenes smaller than C60are predicted
to have unusual electronic, magnetic, and
mechanical properties that arise mainly from
the high curvature of their molecular surface
(1–9). Hindered by the synthetic difficulty,
however, experimental investigation of these
properties is scarce. Our successful capture of
C50not only brings into reality a long-sought
member of the fullerene family but also re-
veals that small non-IPR fullerenes can be
obtained in macroscopic quantities through
passivation of the highly active sites of an
otherwise extremely unstable cage. We have
chromatographic evidence that stable deriva-
tives of other small fullerenes, such as C54
and C56, are also formed in the CCl4graphite
arc-discharge process (fig. S7) (11). The
chlorinated small fullerenes thus obtained
have their curved cage surfaces maintained
(11) and are ready for further chemical ma-
nipulations. For example, up to four Cl
groups of C50Cl10can be replaced by solvol-
ysis reactions with methanol under mild con-
ditions (fig. S8) (11). These results imply that
some of the curvature-related atypical prop-
erties of small fullerenes are retained in their
chlorinated forms and that new avenues for
routine experimental investigations of the
properties and applications of small full-
erenes and their derivatives are now open.
References and Notes
1. K. M. Kadish, R. S. Ruoff, Eds., Fullerene: Chemistry,
Physics and Technology (Wiley, New York, 2002).
2. T. Guo et al., Science 257, 1661 (1992).
3. H. W. Kroto, Nature 329, 529 (1987).
4. C. Piskoti, J. Yarger, A. Zettl, Nature 393, 771 (1998).
5. A. Koshio, M. Inakuma, T. Sugai, H. Shinohara, J. Am.
Chem. Soc. 122, 398 (2000).
6. A. Koshio, M. Inakuma, Z. W. Wang, T. Sugai, H.
Shinohara, J. Phys. Chem. B 104, 7908 (2000).
7. P. W. Fowler, T. Heine, J. Chem. Soc. Perkin Trans.
2001, 2487 (2001).
8. J. R. Heath, Nature 393, 730 (1998).
9. D. Bakowies, W. Thiel, J. Am. Chem. Soc. 113, 3704
10. F. Gao, S. Y. Xie, R. B. Huang, L. S. Zheng, Chem.
Commun. 2003, 2676 (2003).
11. Materials and methods are available as supporting
material on Science Online.
12. We thank R. E. Smalley and X. Xu for reviewing the
manuscript and for helpful suggestions; J. L. Ye, Y. Q. Feng,
technical support; Y. P. Sun, Z. Q. Tian, S. T. Lee, L. Eche-
Tang for helpful discussions; and L. E. Echegoyen for her
careful reading and editing of the manuscript. Supported
by the National Natural Science Foundation of China, the
Ministry of Science and Technology of China, and the
Ministry of Education of China.
Supporting Online Material
Materials and Methods
Figs. S1 to S8
Tables S1 to S3
References and Notes
12 January 2004; accepted 1 March 2004
1State Key Laboratory for Physical Chemistry of Solid
Surfaces and Department of Chemistry, Xiamen Uni-
versity, Xiamen, 361005, China.2Institute of Chem-
istry, Chinese Academy of Sciences, Beijing, 100080,
China.3State Key Laboratory of Magnetic Resonance
and Molecular Physics, Wuhan Institute of Physics and
Mathematics, Chinese Academy of Sciences, Wuhan,
*To whom correspondence should be addressed. E-
Fig. 1. (A) An atmospheric pressure chemical ion-
ization mass spectrum of the isolated product
acquired in the negative-ion mode on a Finnigan
LCQ instrument. m/z, mass-to-change ratio. (B)
Simulated mass spectrum for C50Cl10. (C) Experi-
mental and theoretical13C NMR spectra of D5h
C50Cl10. The theoretical
(inset) was obtained at the B3LYP/6-31G(d) level
of theory with Gaussian98 (11). (D) Schematic
structure of C50Cl10.
13C NMR spectrum
www.sciencemag.org SCIENCEVOL 30430 APRIL 2004
on March 31, 2010