ELECTRON TRANSFER MAKES D3h (78:5) CAGE EASY TO FORM M2@C78(M = La, Ce): A RELATIVISTIC DENSITY-FUNCTIONAL THEORY STUDY

Applying relativistic density functional theory to isomers of C78 and M2@C78(M = La, Ce), we calculate and analyze the relative energies and HOMO–LUMO gaps of neutral and hexaanion ( -6 charged) C78 isomers. Our results indicate that the (5) isomer is the most stable, and it illustrate that electron transfer plays an important role in controlling the stability of endohedral metallofullerenes. We also calculate the electronic structures of there neutral isomers, and based on their LUMO + 2 and LUMO + 3 gaps, we explain why it is easier to encage two metal atoms in D3h′ (78:5). To further elucidate this issue, we theoretically characterize M2@C78(M = La, Ce) and compare the relative energies and the HOMO–LUMO gap of the two isomers M2@C78 (4) and the M2@C78 (5) (M = La, Ce). The results indicate that M2@C78 (5) is more stable than M2@C78 (4). Furthermore, the good agreement between the experimental and computed 13C NMR chemical shift of the isomer M2@C78 (5) provided strong evidence that M2@C78 forms a D3h′ (78:5) cage.