The C60⋯piperidine complex: An excellent model system to evaluate computational methods for noncovalent interactions...

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.