Effect of cation–π interaction on lithium and halogen bonds: a comparative study

Abstract

Ab initio calculations have been performed to study the complex of M+–PhX–NCY (M = Li, Na; X = Li, Br and Y = H, OH and NH2). The aim is to compare the mutual cooperative effects between cation–π and lithium/halogen interactions. These effects are studied in terms of geometric and energetic properties, 15N chemical shielding parameters, molecular electrostatic potentials and natural bond orbital analyses. A positive cooperativity is observed on introduction of a cation–π interaction to the PhLi–NCY and PhBr–NCY dyads. The cation–π interaction has an enhancing effect on the halogen bond interaction energy, making it increased by152%–233%, whereas that of lithium bond interaction by 18%–22%. The enhancing mechanism is analysed in views with the atomic charges, charge transfer and electrostatic potentials.