Sc₂@C₆₆. Spherical Aromaticity in a Markedly Ellipsoidal Endohedral Metallic Fullerene

Incorporation of metallic atoms into fullerenes leads to the characterization of nonclassical cage landscapes, highlighting the markedly ellipsoidal Sc₂@C_2v(4059)-C₆₆ structure. In this work, we set out to explore Sc₂@C_2v(4059)-C₆₆ and its Stone-Wales transformation isomer (Sc₂@C_2v-(3441)-C₆₆) in terms of the resulting characteristics provided by the donation of six electrons from the metallic atoms into the π-electron C₆₆ kernel in terms of induced magnetic field characteristics. The Sc₂@C₆₆ species shows a long/short axis ratio surpassing that of C₇₀, featuring two sets of three consecutively fused pentagons at the poles. From the resulting electron transfer from two encapsulated Sc atoms to the C₆₆ cage, resulting in a 72 π-electron system that fulfills Hirsch's 2(N + 1)² spherical aromaticity rule (N = 5). Our results support the formation of a spherical aromatic endohedral metallic fullerene (EMF) despite the elongated shape, which shows the absence of a direct Sc-Sc bond. The Stone-Wales transformation connecting both isomers modulates their local electronic and magnetic properties, having a lesser impact on the global aromatic properties. These findings highlight the persistence of spherical aromatic characteristics and adaptability in relation to structural rearrangements within an ellipsoidal EMF, as a suitable building block for applications in supramolecular chemistry and related fields.