Cationic CHπ interactions as a function of solvation.

The energy (ΔG) of a cationic CHπ interaction was measured experimentally through the conformational studies of new molecular torsion balances using proton NMR spectroscopy. Each of the molecular balance adopted folded and unfolded conformations for which the ratio of the conformational equilibrium (i.e., folded/unfolded ratio) provided a quantitative measure of the ΔG as a function of solvation. An excellent linear solvation energy relationship between the ΔG values and the Hunter's solvent hydrogen-bond parameters (αs and βs) revealed that electrostatic interaction is the physical origin of the observed conformational preferences in solution.