A reversible and selective chromogenic thiazole tagged chemosensor for Hg2+ in aqueous medium: Crystal structure, theoretical investigations and real sample analysis

A novel thiazole tagged Schiff base chemosensor, (E)-N'-((2-aminothiazol-5-yl)methylene)-2-hydroxybenzohydrazide (ATH) has been synthesized in excellent yield by a simple one pot method and characterized by single crystal X-ray diffraction and spectroscopic techniques. The sensing ability of ATH was determined for detection of Hg2 + ions in the presence of different metal ions in aqueous medium. It behaves as an extremely selective and sensitive chromogenic sensor for naked-eye detection of Hg2 + ions with a colour change from colourless to yellow due to ligand to metal charge transfer. Remarkably, the binding constant (Ka) and limit of detection (LOD) for ATH -Hg2 + complex were found as 1.75 x 10(-4) M (-1) and 8.85 x 10 (-7) M, respectively. The Job's plot indicated that the stoichiometric ratio of ATH to Hg2 + is 1:1. The binding mechanism was established based on FT-IR, (1) H NMR titration, mass spectrometry and density functional theory studies. The chemosensor exhibited an excellent colorimetric property in 7.0-12.0 pH range. The chemosensor was found to be reversible and reusable in the presence of CN- ions with logic gate behaviour. Further, the chemosensor was utilized to sense Hg2 + ions in tap and Ganga river water samples.(c) 2023 Elsevier B.V. All rights reserved.