The development of two fluorescent chemosensors for the selective detection of Zn and Al ions in a quinoline platform by tuning the substituents in the receptor part: elucidation of the structures of the metal-bound chemosensors and biological studies.

Here, two 8-aminoquinoline-based chemosensors, namely, HL and HL (HL = 2,4-dibromo-6-((quinolin-8-ylimino)methyl)phenol and HL = 4-nitro-2-((quinolin-8-ylimino)methyl)phenol) were synthesized by simply changing the substituents in the ligand framework under ambient conditions. They were thoroughly characterized using different spectroscopic techniques, including ESI-mass spectrometry and elemental analysis. HL selectively sensed Zn ions, whereas HL detected Al ions. The metal-bound chemosensors (complexes 1 and 2) were also investigated using different techniques including X-ray crystallography. The binding stoichiometry of the probes with the respective ions was confirmed to be 2 : 1 by Job's plot analysis and X-ray crystallography. The limit of detection (LOD) values for both chemosensors towards the respective metal ions were in the order of ∼10 M, which clearly indicates that these probes have significant potential for biological applications. The capability of our synthesized chemosensors to detect intracellular Zn and Al ions in the triple negative human breast cancer cell line MDA-MB-468 was evaluated with the aid of fluorescence imaging. Mechanistic insights into the anticancer activity of complexes 1 and 2 were also demonstrated in this study. To the best of our knowledge, this is the first time that this type of biological and sensing activity for 8-aminoquinoline-based complexes has been demonstrated in a single platform.