Fluorescent Probes Based on 7‑(Diethylamino)quinolin-2(1H)‑one Cucurbit[7]uril Complexes for Indicator Displacement...

In this work, two 7-(diethylamino)-quinolin-2-(1H)-one derivatives (DQ1 and DQ2) were synthesized and characterized both structurally and physicochemically. The interaction of these derivatives with cucurbit[7]-uril (CB7) was explored through combined experimental and in silico approaches, highlighting their unique behavior and practical potential. Experimentally, the complexes exhibited a 1:1 stoichiometry, as confirmed by fluorescence spectroscopy and isothermal titration calorimetry (ITC). Remarkably, the interaction with the CB7 macrocycle resulted in an unusual negative shift in the pK _a values of the probes alongside a significant enhancement in fluorescence emission, quantum yield, and fluorescence lifetime. From a computational perspective, the molecular dynamics simulations (MD) demonstrated that hydrogen bonds play a critical role in maintaining the system's stability. Finally, DQ2 is proposed as a probe for the indicator displacement assay (IDA) and was tested using methyl viologen (MV) as an analyte.