Quinoline based bio-compatible fluorophore employing dual sensor for Mg(II) and Zn(II): insights from single crystal structures, spectroscopic, DFT and cell imaging studies

Abstract

The quinoline based Schiff base HQNP (E)-3-((2-(4,6-dimethylpyrimidin-2-yl)hydrazono)methyl)quinolin-2-ol were designed and synthesized as fluorescent probe for the dual detection of Zn2+ and Mg2+ ions. The structure of the probe was confirmed by different spectroscopic techniques like single crystal X-ray diffraction (SCXRD), 1H & 13C NMR, FT-IR and ESI-MS spectra. The probe HQNP showed excellent ‘turn on’ fluorescence response with Zn2+ at 446 nm, and with Mg2+ at 442 nm having the detection limits of 1.36 µM and 0.90 µM, respectively. The photoinduced electron transfer (PET) and chelation-enhanced fluorescence (CHEF) sensing mechanism and binding mode of HQNP with these two cations were established by UV-Vis, fluorescence, ESI-MS spectra, Job's plot, lifetime study and DFT studies. Importantly, the 1:1 complexation of HQNP with Zn2+ is confirmed by SCXRD study. The probe able to sense Zn2+ and Mg2+ reversibly against chelating agent EDTA in multiple times. Moreover, HQNP able to detect Zn2+ and Mg2+ in different solvent, different counter cationic as well as anionic environment with minimal interference. Further, excellent cell imaging performance of HQNP with the mentioned ions in TPC-1 and HtH-7 cell lines is observed without marked cytotoxicity.