The role of the counteranion in the cation-(pi) interaction

Chemical double mutant cycles have been used to quantify cation-(pi) interactions in chloroform as a function of the nature of the counteranion. The cation-(pi) interaction is –2.5 ± 0.4 kJ mol–1 and independent of the anion, even though the overall stability of the complexes varies by an order of magnitude due to competition of the anion for alternative binding sites.