Various DFT functionals, including
those containing long-range
interactions and dispersion, together with HF and MP2 theoretical
methods, were used to identify the number of H2 molecules
that can be encapsulated inside a C50 cage. It is demonstrated
that the 2H2@C50 complex is thermodynamically
unstable based on its positive complexation energy. Some discrepancies,
however, were found with respect to the stability of the H2@C50 complex. Indeed, SVWN5, PBEPBE, MP2, B2PLYP, and
B2PLYPD calculations confirmed that the H2@C50 complex is thermodynamically stable, while HF, BP86, B3LYP, BHandHLYP,
LC–wPBE, CAM–B3LYP, and wB97XD showed that this complex
is thermodynamically unstable. Nevertheless, examination of strain
and dispersion energies further supported the fact that one H2 molecule can indeed be encapsulated inside the C50 cage. Other factors, such as the host–guest interactions
and bond dissociation energy, were analyzed and discussed.