The C60⋯piperidine complex: An excellent model system to evaluate computational methods for noncovalent interactions between fullerenes and saturated organic molecules

The five configurations of the complex between fullerene C60 and piperidine are bound mainly by C-H⋯C hydrogen bond, N-H⋯C hydrogen bond, C⋯N tetrel bond, lone pair⋯π interaction, and lone pair⋯σ interaction, respectively, thus making them good models for evaluating computational methods for noncovalent interactions between fullerenes and saturated organic molecules. The interaction energies of the five configurations of C60⋯piperidine were first calculated at the level of the coupled-cluster theory with single, double, and perturbative triple excitations [CCSD(T)] extrapolated to the complete basis set (CBS) limit. Using these CCSD(T)/CBS values as the benchmarks, we evaluated the accuracy of 53 popular low-cost computational methods, among which 49 methods were based on density functional theory (DFT). The results show that the accuracy of DFT-D4 is generally better than that of its predecessor DFT-D3. Surprisingly, even the most primitive DFT-D also consistently outperforms DFT-D3 in terms of accuracy. The ωB97M-V functional demonstrates the highest accuracy in the 53 popular low-cost computational methods, with absolute error magnitudes of the calculated interaction energies all less than 0.20 kcal/mol. The functionals B97M-V, ωB97X-V, B3LYP-D, ωB97X-D, B3LYP-D4, PBE0-D4, TPSS0-D4, X3LYP-D4, and CAM-B3LYP-D4 also show quite good computational accuracy, with absolute error magnitudes of their calculated interaction energies all less than 0.50 kcal/mol. This study lays a solid foundation for further computational investigations of noncovalent interactions between fullerenes and saturated organic molecules.