Structure of a missing-caged metallofullerene: La2@C72

Area of Science:

• Fullerene Chemistry
• Materials Science
• Nanotechnology

Background:

• The C72 fullerene cage is considered "missing" due to its rarity in fullerene synthesis.
• Metallofullerenes, where metal atoms are encapsulated within fullerene cages, exhibit unique properties.
• The isolated-pentagon rule (IPR) is a guiding principle for stable fullerene structures.

Purpose of the Study:

• To elucidate the precise atomic structure of the La2@C72 metallofullerene.
• To investigate whether the La2@C72 structure adheres to the isolated-pentagon rule.
• To understand the implications of non-IPR structures in metallofullerene chemistry.

Main Methods:

• 13C Nuclear Magnetic Resonance (NMR) spectroscopy to analyze the carbon cage.
• 139La Nuclear Magnetic Resonance (NMR) spectroscopy to probe the lanthanum atoms.
• Computational analysis to confirm the proposed structure.

Main Results:

• The structure of La2@C72 was successfully determined.
• The determined structure violates the isolated-pentagon rule (IPR).
• The cage adopts a non-IPR D2 symmetry (cage #10611) with lanthanum atoms near fused pentagons.

Conclusions:

• La2@C72 represents a significant example of a stable non-IPR metallofullerene.
• The findings challenge the universality of the isolated-pentagon rule for metallofullerenes.
• This work expands the understanding of fullerene cage diversity and stability.