The effect of ring annelation to benzene on cation-π interactions: DFT study

Density functional theory (DFT) B3LYP/6-31G(d,p) calculations reveal that the binding affinity of alkali metal cations (Li+, Na+ and K+) with benzene is enhanced by sequential ring annelation of six-membered aromatic ring or highly strained bicyclo[2.1.1]hexene moieties. The bicyclo[2.1.1]hexene annelation to benzene exhibits larger influence on cation-π interactions than six-membered ring annelation. The harmonic vibrational frequencies indicate that all complexes are minima on their respective potential energy surfaces. The extent of charge transfer values from π-systems to cations have been calculated and analyzed.