Higher fullerenes

Higher fullerenes are fullerene molecules consisting of more than 70 carbon atoms. They are cage-like fused-ring structures made of hexagons and pentagons, with a carbon atom at the vertices of each polygon and a bond along each polygon edge.

Synthesis

In 1990, W. Krätchmer and D. R. Huffman's developed a simple and efficient method which boosted the fullerene research. In this technique, carbon soot is produced from two high-purity graphite electrodes by igniting an arc discharge between them in an inert atmosphere (helium gas). Alternatively, soot is produced by laser ablation of graphite or pyrolysis of aromatic hydrocarbons. Fullerenes are extracted from the soot by dissolving it in appropriate organic solvents followed by chromatography.[1] Milligram amounts of higher fullerenes can be obtained with this method in the laboratory and are available commercially for C76, C78 and C84.

Properties

Molecule

Formula CAS number[2] Nis[3] Symmetry[4][5]
C60 99685-96-8 1 Ih
C70 115383-22-7 1 D5h
C72 1 D6h
C74 1 D3h
C76135113-15-4 2 D2*
C78136316-32-0 5 D2v
C80136316-32-0 7
C82136316-32-0 9 C2, C2v, C3v
C84135113-16-5 24 D2*, D2d
C86135113-16-5 19
C88135113-16-5 35
C90135113-16-5 46
C3996175833-78-0

In the table, Nis represents the number of possible isomers within the "isolated pentagon rule", which states that two pentagons in a fullerene should not share edges. Symmetry is specified for the most experimentally abundant form(s), and * marks symmetries with more than one chiral form.

Solid

Solid phases of higher fullerenes[6]
Formula Symmetry Space group No Pearson
symbol		a (nm)b (nm)c (nm)β°Z ρ (g/cm3)
C76 Monoclinic P21 4 mP2 1.102 1.1081.768108.102 1.48
C76 Cubic Fm3m 225 cF4 1.5475 1.5475 1.5475904 1.64
C82 Monoclinic P21 4 mP2 1.141 1.1355 1.8355108.072
C84 Cubic Fm3m 1.5817[7] 1.5817 1.581790

When C76 or C82 crystals are grown from toluene solution they have a monoclinic symmetry. The crystal structure contains toluene molecules packed between the spheres of the fullerene. However, evaporation of the solvent from C76 transforms it into a face-centered cubic form.[6] Both monoclinic and face-centered cubic (fcc) phases are known for better-characterized C60 and C70 fullerenes.

References

  1. ↑ Katz, 369-370
  2. ↑ W. L. F. Armarego; Christina Li Lin Chai (11 May 2009). Purification of laboratory chemicals. Butterworth-Heinemann. pp. 214–. ISBN 978-1-85617-567-8. Retrieved 26 December 2011.
  3. ↑ Manolopoulos, David E.; Fowler, Patrick W. (1991). "Structural proposals for endohedral metal-fullerene complexes". Chemical Physics Letters 187: 1. doi:10.1016/0009-2614(91)90475-O.
  4. ↑ Diederich, Francois; Whetten, Robert L. (1992). "Beyond C60: The higher fullerenes". Accounts of Chemical Research 25 (3): 119. doi:10.1021/ar00015a004.
  5. ↑ K Veera Reddy (1 January 1998). Symmetry And Spectroscopy Of Molecules. New Age International. pp. 126–. ISBN 978-81-224-1142-3. Retrieved 26 December 2011.
  6. ↑ 6.0 6.1 Kawada, H.; Fujii, Y.; Nakao, H.; Murakami, Y.; Watanuki, T.; Suematsu, H.; Kikuchi, K.; Achiba, Y.; Ikemoto, I. (1995). "Structural aspects of C82 and C76 crystals studied by x-ray diffraction". Physical Review B 51 (14): 8723. doi:10.1103/PhysRevB.51.8723.
  7. ↑ Margadonna, Serena; Brown, Craig M.; Dennis, T. John S.; Lappas, Alexandros; Pattison, Philip; Prassides, Kosmas; Shinohara, Hisanori (July 1998). "Crystal Structure of the Higher Fullerene C". Chemistry of Materials 10 (7): 1742–1744. doi:10.1021/cm980183c.

Bibliography

External links