Theoretical Study on the Ground State Structure of Uranofullerene U@C₈₂

Despite its experimental characterization, the detailed geometry and electronic structure of actinide metallofullerene U@C₈₂ have been rarely studied. We predict that ^#5C₈₂ and ^#8C₈₂ are the best cages for the encapsulation of monovalent and tetravalent U (i.e., U⁺ and U⁴⁺), respectively; while ^#9C₈₂ is the best cage for divalent, trivalent, pentavalent, and hexavalent U cations (i.e., U²⁺, U³⁺, U⁵⁺, and U⁶⁺). U@^#9C₈₂ is the thermodynamically most stable one among all the isomers and thus corresponds to the most experimentally isolable isomer of U@C₈₂. The calculated spin density explicitly suggests that the endohedral metallofullerene U@^#9C₈₂ is a trivalent ion-pair with an electronic configuration of U³⁺@C₈₂^3–. The proposed geometry and electronic structure of U³⁺@^#9C₈₂^3– are in good agreement with the experimental observation.