Through-Space Polar-π Interactions in 2,6-Diarylthiophenols.

Molecular recognition between polar groups and aromatic molecules is fundamentally important to rational drug design. Although it has been well established that many polar functionalities interact with electron-rich aromatic residues through energetically favorable polar-π interactions, there is a limited understanding of the association between thiols and aromatic systems. Herein we report physical-organic chemistry studies on 2,6-diarylthiophenols that possess the central thiophenol ring and two flanking aromatic rings with tunable electronic properties caused by substituents at distant para position. Hammett analysis revealed that pKa values and proton affinities correlate well with Hammett sigma values of substituents. Additional energy decomposition analysis supported the conclusion that both through-space SH-π interactions and S- -π interactions contribute to intramolecular stabilization of 2,6-diarylthiophenols.