Selective Confinement of Rare-Earth-Metal Hydrates by a Capped Metallo-Cage under Aqueous Conditions.

The properties of rare-earth-metal ions in aqueous media often depend on their various hydration modes, which allow them to exist as monomeric or oligomeric species with different coordination numbers. Capturing rare-earth-metal ions in a confined cavity can fix their hydration modes and thus enable their intrinsic properties to be distinguished. However, the isolation of ionic species from bulk aqueous media is not an easy task due to competitive interaction with bulk water.

Confinement of Water-Soluble Cationic Substrates in a Cationic Molecular Cage by Capping the Portals with Tripodal Anions.

The ability of a cationic coordination cage to encapsulate molecular guests is enhanced by non-covalent capping of the cage portals with tripodal anions. The capped cage provides new cation binding sites at the portals, which enable accommodation of cationic substrates within the cationic cage. In addition, non-covalent capping allows neutral guests in the cage to be exchanged for cationic ones on demand.