A linear double pyridinium-terminated thread comprising a central chalcone moiety is shown to provide two independent binding sites with similar affinity for cucurbituril (CB7) macrocycles in water as judged from NMR, UV-Visible and fluorescence spectroscopies. Association results in  and pseudorotaxanes, which are both pH and photosensitive. Switching from the neutral chalcone to the cationic flavylium form upon irradiation at 365 nm under acidic conditions provided an enhanced CB7 association (K1:1 increases from 1.2×105 M−1 to 1.5×108 M−1), limiting spontaneous on-thread cucurbituril shuttling. This co-conformational change in the pseudorotaxane is reversible in the dark with kobs=4.1×10−4 s−1. Threading the flavylium moiety into CB7 leads to a dramatic increase in the fluorescence quantum yield, from 0.29 in the free axle to 0.97 in the pseudorotaxane and 1.0 in the pseudorotaxane.
|Journal||Chemistry - A European Journal|
|Publication status||Published - 25 Nov 2021|
- supramolecular chemistry