Selective anion binding by a “Chameleon” capsule with a dynamically reconfigurable exterior

A new class of tetrahedral metal–organic capsules that can incorporate up to twelve different externally-directed amine residues is reported, allowing for very large dynamic libraries to be formed from mixtures of amines. Selectivity is observed both externally—more electron-rich amines are incorporated in favour of electron-poor amines—and internally—PF6− is bound in preference to CF3SO3− or BF4−.