Popular C₈₂ Fullerene Cage Encapsulating a Divalent Metal Ion Sm²⁺: Structure and Electrochemistry

Two Sm@C₈₂ isomers have been well characterized for the first time by means of ¹³C NMR spectroscopy, and their structures were unambiguously determined as Sm@C_2v(9)-C₈₂ and Sm@C_3v(7)-C₈₂, respectively. A combined study of single crystal X-ray diffraction and theoretical calculations suggest that in Sm@C_2v(9)-C₈₂ the preferred Sm²⁺ ion position shall be located in a region slightly off the C₂ axis of C_2v(9)-C₈₂. Moreover, the electrochemical surveys on these Sm@C₈₂ isomers reveal that their redox activities are mainly determined by the properties of their carbon cages.