Quinoline based reversible fluorescent probe for Pb; applications in milk, bioimaging and INHIBIT molecular logic gate.

We report the modular design and synthesis of an amine dangled Schiff base quinoline-morpholine conjugate (QMC) for highly selective detection of Pb ions via fluorimetry. The sensing strategy of QMC towards Pb ion exhibits a large blue shift with fluorescent enhancement via the intramolecular charge transfer (ICT) process. At the same time, QMC coordination with Pb, the CN single bond rotation between quinoline and morpholine rings and the CN isomerization process were blocked. Best of our knowledge, this is the first blue shifted turn-on fluorescent chemosensor for Pb ion via the ICT process. Furthermore, QMC selectively detects Pb ion without any interference with alkali, alkaline earth, and transition metal ions, and limit of detection (LOD) downs to 13 μM, which is a permissible level of Pb ion in drinking water reported by WHO. The 1:2 binding stoichiometry between QMC and Pb was confirmed by fluorimetric, H NMR titration, mass spectrometry, and theoretical studies. Finally, QMC was potentially applied for the sensing of Pb ions in milk, red wine, live cells and an INHIBIT molecular logic function was constructed by using Pb and EDTA as chemical inputs.