Photo‐responsive Bioactive Surfaces Based on Cucurbit[8]uril‐Mediated Host–Guest Interactions of Arylazopyrazoles

A photoswitchable arylazopyrazole (AAP) derivative binds with cucurbit[8]uril (CB[8]) and methylviologen (MV(2+)) to form a 1:1:1 heteroternary host–guest complex with a binding constant of K (a)=2×10(3) m (−1). The excellent photoswitching properties of AAP are preserved in the inclusion complex. Irradiation with light of a wavelength of 365 and 520 nm 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 (1)H NMR 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[8]/MV(2+) 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.