Where does the metal cation stay in Gd@C2v(9)-C82? A single-crystal X-ray diffraction study

Area of Science:

• Fullerenes Chemistry
• Nanomaterials Science
• Supramolecular Chemistry

Background:

• The precise location of metal atoms within endohedral metallofullerenes (EMFs) is critical for determining their unique molecular symmetry and intrinsic properties.
• Previous studies suggested anomalous structures for EMFs, with metal ions positioned over [6,6] bonds.
• Understanding metal positioning is key to controlling EMF behavior and applications.

Purpose of the Study:

• To elucidate the exact position of the gadolinium ion (Gd(3+)) within the C(2v)(9)-C(82) fullerene cage.
• To resolve discrepancies with previous findings regarding the endohedral structure of Gd@C(2v)(9)-C(82).
• To establish the general coordination preference of single rare-earth metals in M@C(2v)(9)-C(82) fullerenes.

Main Methods:

• X-ray crystallographic analysis of cocrystals formed between Gd@C(2v)(9)-C(82) and nickel(II) octaethylporphyrin [Ni(II)(OEP)].
• Comparison of experimental results with theoretical calculations and existing literature data.

Main Results:

• X-ray analysis revealed the Gd(3+) cation is off-center, situated beneath a hexagonal ring along the 2-fold axis of the C(2v)(9)-C(82) cage.
• This finding contradicts a prior study that reported the metal positioned over a [6,6] bond.
• The results align with theoretical predictions and related experimental observations.

Conclusions:

• The single rare-earth metal in M@C(2v)(9)-C(82) preferentially coordinates with the hexagonal ring along the 2-fold axis.
• This coordination preference holds true regardless of the specific metal atom, indicating a consistent structural motif.
• The study clarifies the endohedral structure of Gd@C(2v)(9)-C(82), emphasizing the hexagonal ring interaction over [6,6] bond interaction.