Detection of Iodide Using a Fluorescent Chemosensor Based on Quinaldinium and Imidazole Moieties

—Here, the sensing capability of 2-(2-(1H-imidazol-5-yl)vinyl)-1-ethylquinolin-1-ium iodide (QIM) synthesized by the Knoevenagel reaction, was evaluated with certain anions (F−, Cl−, Br−, I−, CH3COO−, NO3−, HSO4−, and H2PO4−) in solution phase of acetonitrile (MeCN) using fluorescence and absorption spectroscopy techniques. The fluorescence intensity of QIM was substantially quenched upon binding with I− compared to other anions. The detection limit of QIM for I− were calculated as 4.23 μM in MeCN, along with a linear range spanning from 0 μM to 50 μM. Further, the binding mechanism of QIM for detecting I− ion was investigated through Job's plot analysis, and Benesi-Hildebrand study. Job's plots revealed that QIM formed complex with I− in the ratio of 1:1. The binding constant for the QIM-I− complex was determined to be 4.79×105 M−1 by Benesi-Hildebrand equation. Additionally, Stern Volmer quenching constant for the QIM-iodide interaction was determined as 0.0211×106 M-1.