H2@C70
Unlike the H_{2}@C_{60}, the H_{2}@C_{70 }consists of a C_{70 }fullerene that acts as a cage for the trapped H_{2 }molecule. Otherwise, the H_{2}@C_{70 }shares the same physical properties as the H_{2}@C_{60}, its elegant and more symmetric variant of endofullerenes. The C_{70 }cage consistsof 70 carbon atoms arranged in an ellipsoidal shape resembling a rugby ball, with point group symmetry D_{5h}. [1] Hence, the C_{70 }cage is anisotropic as one of its axes is longer than the other two.
The cage potential of C_{70 }experienced by the trapped H_{2 }has been calculated using 5D Potential Energy Surface constructed by summing over pairwise interactions of each atom of H_{2 }with each atom of C_{60 }(Figure1). The HC interactions are modelled using the standard LeonardJones potential. [2] From 1, we can see that the cage potential of the long axis is highly anharmonic and seems almost flat in the central region, whereas the other two short axes cages potential are similar to the cage potentials in H_{2}@C_{60}. [2] Therefore, the C_{70 }has cage potentials resembling a squarewell potential on the long axis, and harmonic potentials on the other two short axes.
Figure 1.The above illustrates the 1D cut through of the optimized 5D Potential Energy Surface of H_{2}@C_{70}. The legends on the graphs represent the orientations of the H_{2 }relative to the C_{70 }at the time of the calculations, where Z is for H_{2 }aligned with the long axis (z), while X and Y are for H_{2 }aligned with the short axes (x and y). [2]
The lower symmetry of the C_{70 }cage causes splitting in states which are otherwise degenerate in H_{2}@C_{60}. [1, 2] For example, the J =1 ground states of orthoH_{2}, which is triply degenerate in the case of H_{2}@C_{60}, is split in the case of H_{2}@C_{70 }into a nondegenerate state with the rotating H_{2 }longitudinally polarized with respect to the C_{70 }long axis (A_{2}” symmetric level), and a doubly degenerate state with the rotating H_{2 }transversely polarized with respect to the C_{70 }long axis (E_{1}’ symmetric level). [1] The spatial wavefunction of H_{2 }in the A_{2}” state has the form of a p_{z }atomic orbital oriented along the long axis of the cage, whereas the spatial wavefunctions of the degenerate E_{1}’ states may be represented either as transverse p_{x }and p_{y }orbitals, or as a complex superposition of both orbitals, giving rise to toruslike complex wavefunctions (see Figure 2). [1]
Figure 2. The figureabove illustrates the spatial wavefunctions of the two lowest energy levels of orthoH_{2}. The labels A_{2}” and E_{1}’rrepresents the symmetric levels of their respective states. The wavefunctions of the confined hydrogen are represented by the torusshaped and p_{z}shaped orbitals inside the fullerene respectively. [1]
References

Salvatore Mamone, Maria Concistr, Ivo Heinmaa, Marina Carravetta, Ilya Kuprov, Gary Wall, Mark Denning, Xuegong Lei, Judy Y.C. Chen, Yongjun Li, Yasujiro Murata, Nicholas J. Turro, and Malcolm H. Levitt (2013), ChemPhysChem, 10.1002/cphc.201300269.

M. Z. Xu, F. Sebastianelli, B. R. Gibbons, Z. Bacic, R. Lawler et al. (2009) J. Chem. Phys.130, 224306.