Competitive inclusion of molecular photo-switches in host cavities

Azobenzene is a widely used guest molecule to build up dynamic photo-responsive host-guest systems. Here, we studied the host-guest complexation of a water-soluble, ortho-fluorinated azobenzene with two different host molecules, a cyclodextrin (β-CD) and a cucurbit[8]uril (CB[8]), and demonstrate that in the presence of both, the guest forms two stable supramolecular complexes selectively. In its trans-form, it favors binding to β-CD, whereas in its cis-form it favors complexation to CB[8]. Upon light-triggered photo-isomerization, the photoswitch was reversibly and selectively transferred from one host cavity to the other. This light-driven host exchange provides a new tool for supramolecular systems