Encapsulation of Hydrogen Molecules in C₅₀ Fullerene: An ab Initio Study of Structural, Energetic, and Electronic Properties of H₂@C₅₀ and 2H₂@C₅₀ Complexes

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.