Photoisomerization, assembling and fluorescence photoswitching behaviors of a water-soluble stiff-stilbene with cucurbit[7]uril

Photoresponsive supramolecular systems have merited extensive attention for their applications in materials science and life science. Here, we synthesized a water-soluble stiff-stilbene molecular photoswitch, exhibiting outstanding photoisomerization reaction between its (E)- and (Z)-configurations upon irradiation at distinct light. The photoswitch can assemble with cucurbit[7]uril (CB[7]) to form a superior fluorescent supramolecular complex (compared to the only guest) with excellent water solubility, which manifested dramatic photoluminescence enhancement caused by restriction of intramolecular rotation and remained good photochromic characteristics. Furthermore, introduction of CB[7] influence photoreaction quantum yield (Φ) of the stiff-stilbene, leading to reduction of ΦE→Z and increase of ΦZ→E of the stiff-stilbene. Importantly, the photoadjustable supramolecular assembly can act as a fluorescence switch, and the phototunable guest further selectively modulate G-quadruplex structure of Tel22 upon light irradiation or with addition of CB[7]. The study provides a new simple way for accurately regulating photochromic properties of molecular switches and developing smart materials with potential applications in controlled modulation of G-quadruplex, targeted biological imaging and so on.