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 pKa 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 pKa values
of 2,6-diarylanilines.