DFT study of the interaction between alkaline cations and molecular bowls derived from fullerene.

A systematic study of the interaction of alkaline cations with curved π systems (molecular bowls) derived from fullerene (C(60)) shows the ability of these structures to form stable cation-π complexes with both of their sides: concave and convex. In all cases, complexes with the cation in the convex side are more stable than its corresponding partner inside the bowl. When forming the complexes with the alkaline cations, these bowls exhibit great stability but several descriptors that usually work in planar conjugate molecules (like the magnitude of the charge transferred to the cation or the cation-ligand distance) do not properly describe the trends observed. The present study shows that with these curved π systems inductive effects play a central role in the formation of complexes with alkaline cations. This conclusion contradicts the simplistic point of view on the dominant effect of the electrostatic term in the interaction between alkaline cations and bowls derived from fullerene. Additionally, steric effects can be relevant when bulky cations are placed in the concave side of the largest bowls.