Two Metastable Endohedral Metallofullerenes ScC@(39656)-C and ScC@(51383)-C: Direct-C-Insertion Products from Their Most Stable Precursors.

Endohedral metallofullerenes (EMFs) are sub-nano carbon materials with diverse applications, yet their formation mechanism, particularly for metastable isomers, remains ambiguous. The current theoretical methods focus mainly on the most stable isomers, leading to limited predictability of metastable ones due to their low stabilities and yields. Herein, we report the successful isolation and characterization of two metastable EMFs, ScC@(39656)-C and ScC@(51383)-C, which violate the isolated pentagon rule (IPR).