Relative Populations of Non-Isomeric Metallofullerenes: La@C76(Td) Vs. La2@C76(Cs,17490)

Very recently, a new member of the lanthanum-containing metallofullerene family has been isolated and its structure determined from X-ray crystallographic analysis, namely [1] La2@C76(Cs,17490), even with two pairs of connected pentagons, hence violating the isolated-pentagon rule (IPR). In order to explain the interesting observation, a computational treatment is suggested for evaluations of the relative populations of non-isomeric metallofullerenes. As a comparative reference structure, the most stable La@C76 isomer is selected - the IPR-C76(Td)-cage based endohedral La@C76(Td). It is found that in the relevant temperature region the La2@C76(Cs,17490) species should be considerably more populated compared to La@C76(Td). The new computational stability treatment is applicable to a wider spectrum of non-isomeric metallofullerenes.

[1] M. Suzuki, N. Mizorogi, T. Yang, F. Uhlik, Z. Slanina, X. Zhao, M. Yamada, Y. Maeda, T. Hasegawa, S. Nagase, X. Lu, T. Akasaka, Chem. Eur. J. 19, doi:10.1002/chem.201302821 (2013).