A novel ditopic ligand derived from 8-hydroxyquinoline: Synthesis, characterisation, and its coordination chemistry with selected metal ions

A novel multidentate ligand, 5-(bis(pyridin-2-ylmethyl)amino)quinolin-8-ol (HL) was synthesised and characterised. Its coordination modes with a variety of metal ions (Mg2+, Co2+, Cu2+, Zn2+, and Hg2+) were investigated using UV–Vis spectroscopic titration. Among the examined metal ions, coordination ratios (M2+: HL) between the metal ion and the ligand at 1:2, 1:1, and 3:2 were observed due to the ditopic nature of the ligand. In acetonitrile, Mg2+ showed relatively strong fluorescent response upon binding to the ligand among the examined metal ions, Li+, K+, Mg2+, Ca2+, Al3+, Cu2+, Fe3+, Cr3+, Zn2+, Co2+, Ni2+, and Hg2+.

An 8-hydroxyquinoline-based ditpic ligand. Spectroscopic titration of the ligand against selected metal ions suggests that the metal ions bind progressively to its two binding sites. The binding of Mg2+ enhanced significantly the fluorescent response of the ligand among the examined metal ions.Figure optionsDownload as PowerPoint slideHighlights
► A hydroxylquinoline-based novel ditopic ligand was described.
► Metal ions bind progressively to the two binding sites of the ditopic ligand.
► Intramolecular charge-transfer involving d electron would be the major fluorescence-quenching mechanism.