Colorimetric and spectroscopic cobalt(II) sensing by a simple Schiff base

A Schiff base ligand assembled on 2,6-bis(iminomethyl)pyridine L has been synthesized, showing visual sensing of cobalt(II) ions over a wide range of transition metal ions including chromium (II), manganese (II), iron(III), nickel(II), copper(II) and zinc(II) in aqueous solution. The addition of cobalt(II) ions to the ligand induced a remarkable visible color change from colorless to yellow in solution, while other cations do not show any apparent color change. The ability of the ligand to detect cobalt(II) ions has been confirmed by UV-Vis studies, displaying new absorption bands at 370 and 570 nm, and supporting the colorimetric results. Structural analysis of the complex of L with nickel(II) reveals that the metal ion is chelated in an octahedral environment by six N atoms from two ligands. (C) 2020 Elsevier Ltd. All rights reserved.