Carbide cluster metallofullerenes: structure, properties, and possible origin.

Area of Science:

• Materials Science
• Nanotechnology
• Supramolecular Chemistry

Background:

• Endohedral metallofullerenes (EMFs) are hybrid molecules with metallic species inside fullerene cages.
• Novel EMFs encapsulate metallic clusters, including carbide clusters (CCMFs), which are synthesized using only graphite and a metal source.
• The structural characterization of CCMFs has been challenging, leading to previous misassignments as conventional EMFs.

Purpose of the Study:

• To present a comprehensive summary of carbide cluster metallofullerenes (CCMFs).
• To detail historically erroneous assignments and provide corrected structural characterizations.
• To discuss the intrinsic properties, formation mechanisms, and origins of cluster EMFs.

Main Methods:

• X-ray crystallography was employed for unambiguous structural identification of CCMFs.
• Review and analysis of existing literature on EMFs and CCMFs.
• Discussion of electrochemical and chemical properties related to CCMF structures.

Main Results:

• Accurate structural characterization of various CCMFs (MxC₂@C2n) using X-ray crystallography.
• Correction of numerous misassigned structures previously described as conventional EMFs (Mx@C2n+2).
• Identification of numerous CCMF species, including scandium, gadolinium, and yttrium-based compounds.

Conclusions:

• X-ray crystallography is crucial for unambiguously identifying CCMFs and distinguishing them from conventional EMFs.
• The '@' symbol should be used cautiously for EMFs lacking unambiguous structural determination.
• Understanding CCMF structures is fundamental for comprehending their intrinsic properties and formation.