Stereospecific change in conformation upon complexation of an exoditopic tetraamide host with a bis(ammonium) guest: chiral recognition and strong CD signaling.

Upon complexation of a rectangular-shaped achiral macrocyclic host with chiral guests, twisting deformation occurs to induce exciton-type bisignated CD, whereas a chiral rectangular host undergoes a similar structural change only with the matching enantiomer of a chiral guest.