A Pyrazole‐Based Highly Selective Colorimetric Chemosensor for Hg ²⁺ Ion in Semi‐Aqueous Medium

In this study, a pyrazole‐based ( Py‐KS) chemosensor was successfully designed and synthesized via Knoevenagel condensation and utilized as a colorimetric chemosensor for selective determination of Hg 2+ in semi‐aqueous media. The probe exhibits a typical absorption band at 519 nm upon interaction with Hg 2+ , which is responsible for remarkable color change from yellow to pink. The detection limit of Py‐KS for the analysis of Hg 2+ was found to be 4.73×10 −7 M. The binding modes of interaction of Py‐KS with Hg 2+ have been determined by Job's plot which exhibits 2:1 ( Py‐KS: Hg 2+ ) ratio, and further confirmed with 1 H NMR titration and FT‐IR analysis. The association constant of Py‐KS ‐Hg 2+ complex was found as 1.2×10 3 M −1 using Benesi‐Hildebrand method. The probe could be recyclable after appropriate treatment with the reagents such as EDTA. Moreover, the designed probe Py‐KS has successfully demonstrated for the detection of Hg 2+ in real sample analysis.