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@<i>C</i>_<i>2v</i><i>(9)</i>-C₈₂ and Sm@<i>C</i>_<i>3v</i><i>(7)</i>-C₈₂, respectively. A combined study of single crystal X-ray diffraction and theoretical calculations suggest that in Sm@<i>C</i>_<i>2v</i><i>(9)</i>-C₈₂ the preferred Sm²⁺ ion position shall be located in a region slightly off the <i>C</i>₂ axis of <i>C</i>_<i>2v</i><i>(9)</i>-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

Sm@<i>C</i>_2<i>v</i>(19138)‑C₇₆: A Non-IPR Cage Stabilized by a Divalent Metal Ion

Although a non-IPR fullerene cage is common for endohedral cluster fullerenes, it is very rare for conventional endofullerenes M@C_2<i>n</i>, probably because of the minimum geometry fit effect of the endohedral single metal ion. In this work, we report on a new non-IPR endofullerene Sm@<i>C</i>_2<i>v</i>(19138)-C₇₆, including its structural and electrochemical features. A combined study of single-crystal X-ray diffraction and DFT calculations not only elucidates the non-IPR cage structure of <i>C</i>_2<i>v</i>(19138)-C₇₆ but also suggests that the endohedral Sm²⁺ ion prefers to reside along the C₂ cage axis and close to the fused pentagon unit in the cage framework, indicative of a significant metal–cage interaction, which alone can stabilize the non-IPR cage. Furthermore, electrochemical studies reveal the fully reversible redox behaviors and small electrochemical gap of Sm@<i>C</i>_2<i>v</i>(19138)-C₇₆, which are comparable to those of IPR species Sm@<i>D</i>_3<i>h</i>-C₇₄