Synthetically simple, click-generated quinoline-based Fe sensors.

Simple quinoline-based fluorescent probes for Fe have been efficiently synthesized through 'click' reaction. Both probes gave intense fluorescence compared to 8-hydroquinoline in various organic solvents due to the inhibition of the excited state intramolecular photon transfer process, while showing dramatically quenched and red-shifted fluorescence in an aqueous solution, which can be attributed to the hydrogen bond-induced intermolecular excited state proton transfer process. In the presence of Fe or in an acidic condition (pH less than 4.0), both probes showed similar quenching of the emission and over 100 nm red-shifts of their emission maxima. The binding mode between the probes and Fe has been found to be 1:1 based on Job's plot. A highly sensitive and selective response in their absorption and emission towards Fe over many other metal ions, including Cr and Cu, was observed and may be the result of the ground state metal to ligand charge transfer effect from Fe to quinoline ligands.