Photoswitchable Host-Guest Systems Incorporating Hemithioindigo and Spiropyran Units

We cover selected examples of the incorporation of hemithioindigo and spiropyran units in one of the binding partners of synthetic host-guest systems. In the simplest systems, the isomerization of the switch simply modulates the thermodynamic stability of the resulting isomeric host-guest complexes. The presence of more than two binding partners constitute multicomponent host-guest systems. In some of them, the isomerization of the molecular switch alters the composition of the system producing a shuttling process of one of the components between different hosts. In others, the isomerization process controls the uptake and release of some of the components from/to the bulk solution. We show that the understanding of the isomerization mechanisms of the molecular switches and the effects produced by the external stimuli are essential for the design of complex and responsive supramolecular host-guest systems. The physicochemical properties of the hemithioindigo and spiropyran molecular photoswitches are complementary, providing different avenues to their applications in solution and material science.