Remarkable Stabilities of Trimetallic Nitride Clusterfullerenes MSc2N@C-70 (M = Sc, Y, Dy) with Three Pentagon Adjacencies: A Theoretical Survey

摘要

A MSc2N@C-70 (M = Sc, Y, Dy) family has been systematically investigated by density functional calculations in conjunction with statistical thermodynamic analyses for the first time. The results revealed that C-2 nu(7854)-C-70 is the most predominant carbon cage when encapsulating DySc2N, YSc2N, and Sc3N clusters. In addition, endohedral structures based on C-1(7852)-C-70 and C-1(7851)-C-70 are also stable with large concentrations in the temperature region of fullerene formation. All these three isomers are non-IPR structures with three pentagon adjacencies (PA) and related by Stole-Wales transformation. The interaction energies (INT) of MSc2N@C-2 nu(7854)-C-70, MSc2N@C-1 (7852)-C-70, and MSc2N@C-1(7851)-C-70 are much more negative than those of the IPR structures MSc2N@D-sh(8149)-C-70, revealing a stabilizing effect of the MSc2N (M = Sc, Y, Dy) clusters toward the PAs. On the basis of the ionic model of (MSc2N)(6+)@C-70(6-), which is confirmed by the frontier orbital analyses, the electron back-donation from C-70(6-) to (MSc2N)(6+) increases in the order of Sc3N@C-70 < YSc2N@C-70 < DySc2N@C-70. Therefore, the INT value increases in the order of Sc3N@C-70 < YSc2N@C-70 < DySc2N@C-70, suggesting that the stabilizing effect of the endohedral cluster is weakened by Y and Dy. Moreover, the UV-vis-NIR spectra of MSc2N@C-2 (7854)-C-70 (M = Sc, Y, Dy) coincide with the experimental characterizations well, and simulations for other isomers will be helpful for further identification of those metal nitride clusterfullerenes.