Binding energy in and equilibrium constant of formation for the dodecahedrane compounds He@C₂₀H₂₀ and Ne@C₂₀H₂₀

Using high-level ab initio methods, the binding energies were calculated for helium and neon inside the cage-like dodecahedrane molecule C₂₀H₂₀- The binding energy of He@C₂₀H₂₀ is 33.8 kcal/mol, including the change in zero-point energy. The corresponding energy for Ne@C₂₀H₂₀ is 98.3 kcal/mol. The ³He nuclear magnetic resonance chemical shift is 1.51 ppm, relative to ³He outside the molecule. The equilibrium constant for He@C₂₀H₂₀ was calculated, and the pressure corresponding to the experimentally synthesized compound is 4 × 10²⁶ atm.