A quantum chemical study of cation-π interaction of lithium cation-aromatic systems

A group of 17 lithium cation-aromatic systems has been investigated with MP2 and density functional theory B3LYP at different level. Geometries, charge transfer, binding energies and electrostatic potential have been obtained for all systems both with restricted and unrestricted optimization. For some systems, possible competition of cation-π interaction with cation-heteroatom interaction has been examined. Particularly, a good correlation between binding energy and electrostatic potential at one point above the center of the aromatic rings was established, which shows that electrostatic potential plays an important role in lithium cation-π systems. It is also demonstrated that for designing or evaluating new larger systems, binding energy can be quantitatively predicted by considering only the aromatic electrostatic potential.