Solvent attenuation of dispersion interactions quantified in polar and nonpolar media using rigid CH–π balances

Abstract

Solvent attenuation of dispersion interactions was quantified using a new class of rigid intramolecular CH–π molecular balances. These balances incorporate small, two-carbon CH donors that minimize solvophobic effects and isolate the dispersion component. Folding energies (ΔG_exp) were measured across eight solvents: cyclohexane, toluene, chloroform, ethyl acetate, acetone, acetonitrile, DMSO, and methanol. Attenuation values in nonpolar solvents closely matched those reported by Peter Chen using a bimolecular host-guest system. Our use of a molecular balance also enabled study in polar solvents where the attenuation remained similarly high in polar solvents such as DMSO and methanol. The narrow 75 to 80 percent range observed across all solvents demonstrates the consistency of dispersion attenuation and the effectiveness of molecular balances in quantifying weak noncovalent forces while avoiding interference from solvent driven effects. Comparisons between sp² and sp³ CH donors showed similar dispersion contributions, with sp² groups exhibiting stronger overall interactions due to greater electrostatic stabilization. As a result, sp² CH groups formed stronger interactions in nonpolar solvents, while both CH types showed similar strengths in polar solvents.