Fluorescent Probes Based on 7-(Diethylamino)quinolin-2(1<i>H</i>)-one Cucurbit[7]uril Complexes for Indicator Displacement Assays: <i>In Silico</i> and Experimental Approaches

In this work, two 7-(diethylamino)-quinolin-2-(1<i>H</i>)-one derivatives (<b>DQ1</b> and <b>DQ2</b>) were synthesized and characterized both structurally and physicochemically. The interaction of these derivatives with cucurbit[7]-uril (<b>CB7</b>) was explored through combined experimental and <i>in silico</i> 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 <b>CB7</b> macrocycle resulted in an unusual negative shift in the p<i>K</i> _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, <b>DQ2</b> is proposed as a probe for the indicator displacement assay (IDA) and was tested using methyl viologen (<b>MV</b>) as an analyte.