Stereoselective Encapsulation for a Triarylmethylium o,o-Dimer by Natural γ-Cyclodextrin: Origin of Chiral Recognition for the Axially Chiral Dicationic Guest.
Upon 1:1 complexation with γ-cyclodextrin (CyD) in water, easily interconverting rotational isomers of biphenyl-2,2'-diylbis[bis(4- dimethylaminophenyl)methylium] (R)/(S)-1a2+ were biased to prefer an R configuration (75 : 25 at 25 ºC). Docking and quantum chemical calculations revealed two modes (on-top and botton-side) of encapsulation of γ-CyD, which shed a light on the origin of the first chiral recognition of axially chiral dicationic dyes by using natural CyDs.