Anion Recognition through Multivalent C-H Hydrogen Bonds: Anion-Induced Foldamer Formation and Transport across Phospholipid Membranes.

A series of triazole-cyanostilbene receptors were designed and synthesized. The receptor binds with the anions through various CH···anion hydrogen bonding interactions, where strong binding was observed for SO42- anions followed by Cl-, Br-, NO3-, and I-, calculated from the 1H NMR titration experiment. The NOESY NMR experiment of the receptor confirmed the formation of anion-induced folded conformation. The CH···anion hydrogen bonding interaction-mediated anion recognition and foldamer formation were further confirmed from geometry optimization studies of the anion-bound complex. The receptor transports Cl- anions efficiently compared to SO42- anions across the lipid bilayer membrane via a mobile carrier mechanism.