ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 2, pp. 121−127. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © V.S. Kozlov, M.V. Suyasova, V.T. Lebedev, 2014, published in Zhurnal Prikladnoi Khimii, 2014, Vol. 87, No. 2, pp. 137−143.
INORGANIC SYNTHESIS AND INDUSTRIAL
Preparation and study of nanosized materials
exhibiting unique structure and properties is a rapidly
developing line of the modern science. Nanomaterials
based on carbon, such as fullerenes, carbon nanotubes,
and graphenes, have wide and diverse ﬁ elds of potential
application in science, engineering, molecular biology,
and medicine [1, 2].
Prospects for introducing fullerenes and radioactive
endohedral metallofullerenes (EMFs) into medicine for
diagnostic (NMR imaging) and therapeutic purposes are
of particular importance .
A unique advantage of radiometallofullerens as
radiopharmaceuticals is chemical protection of the
radioactive isotope by the carbon shell, preventing
chemical and biological action on the radioisotopes and
eliminating the side effects (toxicity).
Numerous procedures for preparing metallofuller-
enes, from laser sputtering to “molecular surgery,” have
been reported [4, 5]. The electric arc method for prepar-
ing fullerenes, suggested for the ﬁ rst time as early as
1990 , remains the most efﬁ cient. It consists in that
graphite rods doped with difﬁ cultly volatile compounds
of appropriate metal (e.g., lanthanide oxides, carbides,
hydrides, alloys) are evaporated in an arc discharge in
an inert gas atmosphere. The soot thus obtained con-
tains a mixture of empty fullerenes and endohedral
metallofullerenes, which is subjected to extraction and
subsequent chromatographic separation.
Various extraction procedures are used for
recovering EMFs from fullerene-containing soot (FCS)
in a laboratory [7, 8]. Soxhlet extraction  is the
simplest, the most efﬁ cient, and the safest procedure
for recovering EMFs from fullerene-containing soot.
Extraction of fullerenes with FCS is performed with
solvents differing in the fullerene solubility, polarity,
and chemical structure: toluene, o-xylene, carbon
disulﬁ de, o-dichlorobenzene, 1,2,4-trichlorobenzene,
and dimethylformamide (DMF).
For example, Shinohara et al.  recovered scandium
EMFs by Soxhlet extraction of the soot with carbon
disulﬁ de. Low efﬁ ciency of the EMF recovery with the
suggested procedure is associated with relatively low
extraction ability of carbon disulﬁ de.
The metal ion in EMFs is not located in the center of
the fullerene cage but is shifted toward one of the ends
of the elongated molecule. As a result, the molecule,
Synthesis, Extraction, and Chromatographic Puriﬁ cation
of Higher Empty Fullerenes
and Endohedral Gadolinium Metallofullerenes
V. S. Kozlov, M. V. Suyasova, and V. T. Lebedev
Konstantinov Petersburg Institute of Nuclear Physics, National Research Center Kurchatov Institute, Orlova Roshcha,
Gatchina, Leningrad oblast, 188300 Russia
Received February 14, 2014
Higher empty and endohedral gadolinium metallofullerenes were prepared by electric arc synthesis,
isolated, and separated chromatographically to high degree of purity (99 wt %). The samples obtained were
characterized by chromatography, optical spectroscopy, and mass spectrometry. According to small-angle
neutron scattering data, the endohedral metallofullerenes in o-xylene form a molecular solution in which
the molecules interact to form molecular pairs.