Stabilization of 2,6-Diarylanilinum Cation by Through-Space Cation-π Interactions

Energetically favorable cation-π interactions play important roles in numerous molecular recognition processes in chemistry and biology. Herein, we present synergistic experimental and computational physical-organic chemistry studies on 2,6-diarylanilines that contain flanking meta/para-substituted aromatic rings adjacent to the central anilinium ion. A combination of measurements of pK_a values, structural analyses of 2,6-diarylanilinium cations, and quantum chemical analyses based on the quantitative molecular orbital theory and a canonical energy decomposition analysis (EDA) scheme reveal that through-space cation-π interactions essentially contribute to observed trends in proton affinities and pK_a values of 2,6-diarylanilines.