Induced preference for axial chirality in a triarylmethylium o,o-dimer upon complexation with natural -cyclodextrin: strong ECD signaling and fixation of supramolecular chirality to molecular chiralityElectronic supplementary information (ESI) available. CCDC 843534. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2cc17475h

The ratio of the easily interconverting rotational isomers of biphenyl-2,2-diylbis[bis(4-dimethylaminophenyl)methylium] ( R )/( S )- 1a 2+ can be biased to prefer an R configuration upon 1:1 complexation with -cyclodextrin in water. Through the reaction with Na 2 S, the preference of 1a 2+ @-CyD for an axial chirality of R can be fixed as the M -helicity of dihydrothiepin 2 . Intermolecular chirality transfer upon hostguest complexation of dications with cyclodextrins.