Selective Host-Guest Interactions of a Transformable Coordination Capsule/Tube with Fullerenes

An M2L4 coordination capsule or an M2L2 coordination tube was selectively formed by the combination of Hg-II hinges and bent bispyridine ligands. The two structures reversibly interconvert at room temperature in response to modulation of the metal-to-ligand ratio and exhibit different host-guest interaction behavior. The capsule alone encapsulates large spherical molecules, fullerenes C-60 and C-70, and the bound guests are released upon capsule-to-tube transformation by the simple addition of metal ions.