A photoswitchable arylazopyrazole (AAP) derivative binds with cucurbituril (CB) and methylviologen (MV2+) to form a 1:1:1 heteroternary host-guest complex with a binding constant of Ka=2×103m-1. The excellent photoswitching properties of AAP are preserved in the inclusion complex. Irradiation with light of a wavelength of 365 and 520nm leads to quantitative E- to Z- isomerization and vice versa, respectively. Formation of the Z-isomer leads to dissociation of the complex as evidenced using 1HNMR spectroscopy. AAP derivatives are then used to immobilize bioactive molecules and photorelease them on demand. When Arg-Gly-Asp-AAP (AAP-RGD) peptides are attached to surface bound CB/MV2+ complexes, cells adhere and can be released upon irradiation. The heteroternary host-guest system offers highly reversible binding properties due to efficient photoswitching and these properties are attractive for designing smart surfaces.
- Host-guest systems
- host–guest systems