A chromone based Schiff base: An efficient colorimetric sensor for specific detection of Cu (II) ion in real water samples

A new chromone based Schiff base ligand L was synthesized by the condensation of 3-formyl chromone and pyrazine-2-carbohydrazide as a colorimetric probe to detect Cu (II) ions selectively. An instant visual colour change from colourless to yellow was obtained on addition of Cu2+ ions to the probe L solution, while other metal ions found ineffective. The ligand L was characterized by H-1 NMR, FTIR and HRMS spectral techniques. UV-Visible spectroscopic technique was used to study the sensing ability of probe L for copper ions above other metal ions. The Job's plot obtained from absorption studies and HRMS data confirmed that the Cu2+ ions bind with ligand L in 1:1 stoichiometric ratio. DFT computations were also supported the binding framework between L and Cu (II) ions. The LOD value and the association constant were obtained 3.9 x 10(-7) M and 2.3 x 10(5) M-1 respectively, via Benesi-Hildebrand equation. Selectivity of L towards Cu2+ ions was also studied and it was found that the probe L worked specifically for copper ions without any considerable influence of other intruding metal ions. In addition, in real water samples, the ligand L was fully implemented for identification and quantification of Cu2+ ions. (C) 2020 Elsevier B.V. All rights reserved.