Higher Fullerenes: Structure and Properties

Abstract

The structures of higher fullerenes are described based on 13C NMR measurements of isolated and purified samples. The most interesting aspect deduced from the present structural work on the higher fullerenes up to C90 is that among 19 kinds of fullerenes with different sizes and isomers, 18 fullerenes commonly have at least one C2 symmetry axis in their molecular frame. Only one exception is C90 fullerene with a C1 symmetry. The spectral feature of UV/Visible absorption obtained for the HPLC-isolated C120 fullerene gives, on the other hand, a strong indication that the numbers of co-existing isomer of very large fullerenes are extremely limited, probably one or two. Considering the huge numbers of IPR-(isolated pentagon rule) satisfying isomer of C120 (10,774), these experimental evidences may suggest the presence of very strong selectivity for the formation of stable higher fullerenes, which, in turn, is closely associated with the unknown growth process of a fullerene cage network.

C94 IPR isomeric set: large-scale computations of relative stabilities based on the Gibbs function

“…Achiba et al have released [6,33] preliminary notes on their 13 C NMR investigations of C 94 . They list [6,33] four structures with the symmetries: C 2 ; C s ; C 2 ; and C 2 ; though no concentration ratio is given and a further development is, in principle, possible.…”

“…They list [6,33] four structures with the symmetries: C 2 ; C s ; C 2 ; and C 2 ; though no concentration ratio is given and a further development is, in principle, possible. Clearly enough, the AM1 computed relative concentrations match the observed data quite well as the above computational six-membered set of especially populated species contains the four symmetries observed in the experiment.…”

“…[2,27], C 88 -e.g. [2,28], C 90 -e.g. [2,29], C 92 [3,6, 30 -33], and even some still higher families [5,6,34,35].…”

“…[2,28], C 90 -e.g. [2,29], C 92 [3,6, 30 -33], and even some still higher families [5,6,34,35]. In overall, the computations have demonstrated [36,37] that, from the theoretical point of view, the higher fullerenes cannot be really understood without an inclusion of temperature effects, i.e.…”

Computations on the IPR isomers of C88 and C90

“…At present over thirty higher fullerenes C n with n from 76 till 94 have been identified [1][2][3][4], especially by means of 13 C NMR in solution. From the spectra, the molecular symmetries have been assigned to higher fullerenes.…”