Structural stability, electronegativity and electronic property of endohedral TM@C24 and exohedral TMC24 (TMÂ =Â Sc, Y and La) metallofullerene complexes: Density-functional theory investigations

The structural stability, electronegativity and electronic property of endohedral TM@C24 and exohedral TMC24 (TM = Sc, Y and La) complexes have been systematically investigated using the hybrid DFT-(U)B3PW91 functional. The calculated results show that the endohedral complexes do not undergo any major deformation in the structures, and the Sc atom is energetically favorable to be encapsulated into the centre of the cage. But in the Y and La cases the exohedral structure is more stable than the endohedral structure. The frontier orbital analyses indicate that the exohedral TMC24 complexes have the high kinetic stabilities, which are consistent with their thermodynamic stabilities. Additionally, natural population analyses also tell us that the natural charges on TM atoms are obviously increased with the increasing atomic radii except for the endohedral La@C24. In the La@C24, the La atom acts as an electron acceptor with the negative charges. And its 4f orbitals are significantly involved in the formation of the chemical bonding.