C68 Fullerene Isomers, Anions, and their Metallofullerenes: Charge‐Stabilizing Different Isomers

Abstract

The complete set of 6332 classical isomers of the fullerene C(68) as well as several non-classical isomers is investigated by PM3, and the data for some of the more stable isomers are refined by the DFT-based methods HCTH and B3LYP. C(2):0112 possesses the lowest energy of all the neutral isomers and it prevails in a wide range of temperatures. Among the fullerene ions modeled, C(68) (2-), C(68) (4-) and C(68) (6-), the isomers C(68) (2-)(C(s):0064), C(68) (4-)(C(2v):0008), and C(68) (6-)(D(3):0009) respectively, are predicted to be the most stable. This reveals that the pentagon adjacency penalty rule (PAPR) does not necessarily apply to the charged fullerene cages. The vertical electron affinities of the neutral C(s):0064, C(2v):0008, and D(3):0009 isomers are 3.41, 3.29, and 3.10 eV, respectively, suggesting that they are good electron acceptors. The predicted complexation energy, that is, the adiabatic binding energy between the cage and encapsulated cluster, of Sc(2)C(2)@C(68)(C(2v):0008) is -6.95 eV, thus greatly releasing the strain of its parent fullerene (C(2v):0008). Essentially, C(68) fullerene isomers are charge-stabilized. Thus, inducing charge facilitates the isolation of the different isomers. Further investigations show that the steric effect of the encaged cluster should also be an important factor to stabilize the C(68) fullerenes effectively.