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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. June 2006, Volume 5, Number 6, 355-363 |
Electronic Structures of the Tube-like Fullerene Dimers
(C60+10n)2
Yasushi Nomura, Hiromitsu Arai, and Susumu Narita
Internet Electron. J. Mol. Des. 2006, 5, 355-363
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Abstract:
In the fullerene C60 polymers, the polymerization reaction can be
described as a [2+2] cycloaddition across parallel 6,6-ring fusion
bonds in neighboring C60 molecules. The bonds are known to be
active in addition reactions due to their high double bond
character. The fullerene C70 with the D5h symmetry also has such
active 6,6-ring fusion bonds nearby the poles of the molecule, and
it have been shown that a [2+2] cycloaddition cap-to-cap C70-dimer
is synthesized. The fullerene C70 with the D5h symmetry is
the smallest member of a group named the tube-like fullerene
C60+10n (n = 1, 2, …) consisting
of the bisected caps of C60 and a
single-wall cylinder. According to the Pauling bond order analysis,
the C60+10n has the active 6,6-ring fusion bonds and the [2+2]
cycloaddition dimer similar to the cap-to-cap C70-dimer is
expected. Here we consider the electronic structures of the cap-to-cap
dimers (C60+10n)2. Analyzing the MOs nearby the HOMO-LUMO
gaps, the mutual relations between MOs of the dimer and
of the monomer are shown. MO calculations are made in the
semiempirical CNDO/S approximation. The geometries optimized
with Gaussian 03 at the AM1 level are used. The HOMO-LUMO
gap energy of the (C60+10n)2
shows a periodic n-dependence quite
similar to that of the C60+10n. The gap value calculated on the
(C60+10n)2 is almost the same to that
on the C60+10n, although the
former is slightly less than the later. The HOMO (LUMO) of the
dimer can be described in terms of the HOMOs (LUMOs) of the
corresponding two monomers. The MO properties of the C60+10n
are maintained in the [2+2] cycloaddition dimer (C60+10n)2 nearby
their HOMO-LUMO gap.
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