Peripheral Templation-Modulated Interconversion between an A L Tetrahedral Anion Cage and A L Triple Helicate with Guest Capture/Release.

An anion-coordination-based A L ("A" denotes anion and "L" is ligand) tetrahedral cage was constructed by a C -symmetric bis-bis(urea) ligand and phosphate anion, which showed reversible interconversion with the A L triple helicate as a response to the template, concentration, or solvent. Notably, an unusual "peripheral" templation was found to be critical to stabilize the tetrahedral structure. This peripheral effect was utilized to assemble an "empty" A L cage that allows the multi-stimuli-controlled capture/release of biologically important species such as choline and acetylcholine.