Stabilizing a non-IPR C 2 (13333)-C 74 cage with Lu 2 C 2 /Lu 2 O: the importance of encaged non-metallic elements.

A difference in encaged non-metallic element ( i.e. , C 2 versus O) leads to a clear change of intramolecular interactions and shifts in redox potentials of Lu 2 C 2 @ C 2 (13333)-C 74 and Lu 2 O@ C 2 (13333)-C 74 , as a result of their distinct molecular orbital energy levels. Different from these two endoherals whose HOMOs are located on the cage, experimentally absent Lu 2 @ C 2 (13333)-C 74 possesses a HOMO predominantly delocalized on the internal Lu-Lu bond, accompanied by a much smaller HOMO-LUMO gap, suggesting that the presence of a non-metallic unit broadens the electrochemical gaps and consequently improves the kinetic stability. These findings shed light on the role of non-metallic moieties in clusterfullerenes, providing valuable insights into the stability and properties of metallofullerenes.