Host-guest complexes of cucurbit[6]uril with isoprenaline: the effect of the metal ion on the crystallization pathway and supramolecular architecture

We report on the three host-guest complexes between the cucurbit[6]uril macrocycle and the catecholamine drug isoprenaline obtained in the presence of magnesium or calcium ions. The metal ions affect both the crystallization pathway of the CB6-isoprenaline complexes and the supramolecular architecture in the solid state. In the case of the magnesium cations the sequential crystallization of the metal-free and the magnesium containing forms of the host-guest complexes was observed, while the use of calcium cations resulted in the direct crystallization of the calcium-coordinated CB6-isoprenaline complex.