Carbide cluster metallofullerenes (CCMFs) have drawn more and more attention during recent years due to their special structures and properties^1-3. Herein, we found that some unprecedented medium-sized carbon cages ranging from C₈₆ to C₉₀ can be stabilized by choosing suitable metal atoms (yttrium). Our single-crystal crystallographic results unambiguously showed that they are carbide cluster metallofullerenes Y₂C₂@C_2n (2n=86,88 and 90). It is proposed that the size of the encapsulated metallic units plays a crucial role in stabilization of these medium-sized fullerene cages.

Reference

(1) Lu, X.; Akasaka, T.; Nagase, S. Carbide Cluster Metallofullerenes: Structure, Properties, and Possible Origin. Acc. Chem. Res. 2013, 47 (7), 1627–1635.

(2) Cai, W.; Bao, L.; Zhao, S.; Xie, Y.; Akasaka, T.; Lu, X. Anomalous Compression of D₅(450)-C₁₀₀ by Encapsulating La₂C₂ Cluster instead of La2. J. Am. Chem. Soc. 2015, 137 (32), 10292–10296.

(3) Cai, W.; Li, F.-F.; Bao, L.; Xie, Y.; Lu, X. Isolation and Crystallographic Characterization of La₂C₂@Cs(574)-C₁₀₂ and La₂C₂@C₂(816)-C₁₀₄: Evidence for the Top-Down Formation Mechanism of Fullerenes. J. Am. Chem. Soc. 2016, 138 (20), 6670–6675.