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@C(82) have been rarely studied. We predict that (#5)C(82) and (#8)C(82) are the best cages for the encapsulation of monovalent and tetravalent U (i.e., U(+) and U(4+)), respectively; while (#9)C(82) is the best cage for divalent, trivalent, pentavalent, and hexavalent U cations (i.e., U(2+), U(3+), U(5+), and U(6+)). U@(#9)C(82) is the thermodynamically most stable one among all the isomers and thus corresponds to the most experimentally isolable isomer of U@C(82). The calculated spin density explicitly suggests that the endohedral metallofullerene U@(#9)C(82) is a trivalent ion-pair with an electronic configuration of U(3+)@C(82)(3-). The proposed geometry and electronic structure of U(3+)@(#9)C(82)(3-) are in good agreement with the experimental observation.