Inversion Barrier of Corannulene. A Benchmark for Bowl-to-Bowl Inversions in Fullerene Fragments

In a systematic ab initio study, the Hartree−Fock, B3LYP density functional, and MP2 methods are employed to calculate the bowl-to-bowl inversion barrier of corannulene (1). Basis sets ranging from a minimal basis (STO-3G) to a double polarized valence triple-ζ basis (6-311G(2d,2p)) were used. In comparison with experimental data, it was found that inclusion of dynamic electron correlation (e.g., B3LYP) and a 6-311G** basis set (or other basis sets with similar complexity) are essential for quantitatively correct results. At B3LYP/6-311G**, ΔG ⧧ 298 = 44.9 kJ/mol. Thermal corrections to Gibbs energy of activation were of minor importance in the relevant range of temperatures. Inversion barriers (ΔE ⧧ Tot) of the bowl-shaped fullerene fragments C26H12 4 and C30H12 5 and the chiral C30H12 6 are predicted to be 28.0, 199.4, and 277.3 kJ/mol, respectively, at B3LYP/6-311G**. Predicted enthalpies of formations and strain energies are also discussed.