Relative stabilities of Cisomers

Relative stabilities of six C74 fullerene cages are evaluated: one species obeying the isolated pentagon rule (IPR), three isomers with a pentagon-pentagon junction, two structures with one pentagon-pentagon pair and one heptagon. The computations are carried out using the Gibbs energy in a broad temperature interval. It is shown that the IPR cage (D3h symmetry) prevails throughout. As low-lying electronic excited states are possible for the cages, their electronic partition functions are included into consideration. It is argued that for the special conditions of the fullerene synthesis/isolation, the electronic partition function based on the singlet excited states only should better reproduce the experimental population findings. The computations indicate that isolation of other C74 cage, in addition to the IPR isomer, is less likely though not impossible.