A highly selective fluorescent sensor for zinc ion based on quinoline platform with potential applications for cell imaging studies

An 8-aminoquinoline based fluorescent Zn2+ sensor, 2-methoxy-6-((quinolin-8-ylimino)methyl)phenol (HL), was synthesized. It has been found to display quick responses through fluorogenic properties on selective 2:1 binding to Zn2+, as delineated by absorption and fluorescence titrations as well as by Job’s method and X-ray crystallography studies. This probe features visible light excitation (461 nm) and emission (594 nm) profiles, excellent selectivity responses for Zn2+ over other competing biological metal ions with high binding constant and about 17-fold enhancement in fluorescence quantum yield (Φ) upon half equivalent of Zn2+ binding under physiological pH window. The low detection limit in micromolar range (1.3 × 10−7 M) for Zn2+, makes HL a suitable candidate for the development of a potential probe. It also exhibits cell permeability and intracellular Zn2+ sensing in HeLa cells from human cervical cancer cell and rat hippocampal slices.