New Oxoquinoline‐Imidazole Based Fluorescence Signaling Switches for the Determination of Zn ²⁺ /F ⁻ (OFF‐ON), and Fe ³⁺ /Picric Acid (ON‐OFF): Applications in Anticancer Activity

Abstract A series of new oxoquinoline‐imidazole derivatives ( IMD1‐IMD4) was prepared, and they were characterized by analytical and spectral data. Further, they were employed as effective fluorescence signaling switches through “OFF‐ON” and “ON‐OFF” by an ESIPT (excited‐state intramolecular proton‐transfer) mechanism. The OFF‐ON green fluorescence exhibited by IMD1 selectively at 486 nm with Zn 2+ and F − is the basis for the determination of Zn 2+ and F − ions by way of detection limits of 5.28×10 −9 M and 1.74 ×10 −10 M, respectively. In contrast, IMD3 being fluorescent active (ON) with blue emission at 464 nm selectively exhibits quenching in fluorescence intensity in the presence of Fe 3+ and picric acid (PA) at pH 7.4. This quenching property of IMD3 leads to the rapid determination of Fe 3+ and picric acid (PA) selectively with a limit of detection of 3.28×10 −9 M and 1.63×10 −10 M, respectively. Experimental findings have been well‐complemented by Density Functional Theory (DFT) studies. The activity of the synthesized oxoquinoline‐imidazole compounds ( IMD1 and IMD3) was demonstrated on HeLa (Henrietta Lacks, a human cell line) and breast cancer cells for the detection of Zn 2+ and Fe 3+ ions, respectively.