Contrasting behaviors of metal fullerides C60Rhx and C60Mx (M=La, Y) in the metallofullerene formation by laser ablation

Contrasting behaviors of Rh with Y(La) in the formation of metallofullerenes by excimer laser ablation of metal fullerides C60Rhx and C60Mx (M = La, Y) were observed. For Rh, two sequences of rhodium metallofullerenes, C2nRh and C2n+1Rh with even and odd numbers of carbon atoms, are formed in both the negative and positive ion channels, but for La and Y, only the metallofullerene sequence with even numbers of carbon atoms is formed and only in the positive ion channel. Evidence of the encapsulation of La and Y atoms in fullerene cages forming endohedral fullerenes has been observed, whereas the Rh atom is most probably incorporated into the network of the fullerene cage or pseudo-fullerene forming substitutional metallofullerenes. Density functional theory calculation was performed to determine the structures of the model metallofullerenes C53Rh and C54M (M = Rh and Y). The calculated results are in general consistent with the experimental observations.