Supramolecular Complexation of Locked-Flavylium Fluorescent Dye by Cucurbit[7]uril: Photophysics and pKa Modulation

Abstract

Herein, we studied the supramolecular host-guest complexation between cucurbit[7]uril (CB7) and a locked version of flavylium dye (LF) in aqueous solution. CB7 was able to form complexes with LF in its various protonation states as verified by UV-visible and fluorescence spectroscopy, revealing high binding affinities for the cationic and neutral form compared to the anionic one and resulting in complexation induced pKa shifts. The formation of inclusion complexation was established by 1H NMR and supported by DFT calculations.