Dimetallic sulfide endohedral metallofullerene Sc₂S@C ₇₆: Density functional theory characterization

In terms of density functional theory combined with statistic mechanics computations, we investigated a dimetallic sulfide endohedral fullerene Sc ₂S@C₇₆ which has been synthesized without any characterization in experiments. Our theoretical study reveals that Sc ₂S@T_d(19151)-C₇₆ which satisfies the isolated-pentagon rule (IPR) possesses the lowest energy, followed by three non-IPR structures (Sc₂S@C_2v(19138)-C₇₆, Sc₂S@C_s (17490)-C₇₆, and Sc₂S@C ₁(17459)-C₇₆). To clarify the relative stabilities of those isomers at high temperatures, enthalpy-entropy interplay has been taken into consideration. Calculation results indicate that three species Sc ₂S@T_d(19151)-C₇₆, Sc₂S@C _2v(19138)-C₇₆, and Sc₂S@C₁(17459)- C₇₆ have noticeable molar fractions at the fullerene-formation temperature region (500-3000K), and the Sc₂S@C₁(17459)- C₇₆ with one pentagon pair becomes the most predominant isomer above 1800 K, suggesting that the unexpected non-IPR structure is thermodynamically favorable at elevated temperatures. In addition, the structural characteristics, electron features, UV-vis-NIR adsorptions, and ¹³C NMR spectra of those three stable structures are introduced to assist experimental identification and characterization in future.