Theoretical Insights into the Stability and Electronic Properties of Sc3N@C74

Abstract Endohedral metal nitride cluster fullerenes exhibit broad application prospects in fields such as electronics, catalysis, and biomedicines owing to their unique structures and physicochemical properties, while their macroscopic performance fundamentally depends on the microscopic bonding mechanism between the encapsulated clusters and the carbon cages. In this work, Sc3N@C74 is chosen as a representative model to systematically uncover the intrinsic interplay between the encapsulated Sc3N cluster and the C74 carbon cage, alongside the underlying structural and electronic characteristics governing this endohedral fullerene system. The thermodynamic stability, geometric structure, electron distribution, and chemical bonding characteristics were comprehensively analyzed using density functional theory calculations, and the results revealed that the most stable isomer─Sc3N@D3h(14246)-C74─satisfies the isolated-pentagon rule, exhibits pronounced electron transfer from the Sc3N cluster to the C74 cage, and extensive orbital hybridization. Furthermore, Mayer bond order analysis quantitatively confirmed a substantial covalent contribution to the Sc–C interactions. This synergistic bonding motif─characterized by strong covalent bonding at the cluster-cage interface and mixed (covalent/ionic) interactions in the outer regions─establishes a robust theoretical framework and rational design principle for predicting and engineering high-performance endohedral fullerene materials. Finally, the UV-vis-NIR simulation of the most stable isomer Sc3N@D3h(14246)-C74 predicted its characteristic peaks, thereby establishing an experimentally verifiable quantitative theoretical basis for subsequent synthesis and spectral characterization.