Novel quinoline-derived chemosensors: synthesis, anion recognition, spectroscopic, and computational study

Abstract

Fluorescent-small molecules offer an excellent source of chemosensors when optimized for detection of anions with sensitivity and selectivity, low-cost and robust synthesis. In the present study we synthesized new quinoline-based chemosensors (4a–e) via the one-pot multi component reaction and confirmed their potential for chemosensory via cyclic voltammetry. 4a–e were tested for ligand–anion interaction against F⁻, OAc⁻, Br⁻, ClO₃, I⁻, HSO₄⁻, CN⁻, ClO₄⁻ and SCN-ions, by using UV-visible, colorimetry and Fluorescence. The NH deprotonation was observed as the mechanism of anion interaction via FTIR and H¹NMR spectroscopies. Benesi–Hildebrand plot was drawn to calculate binding constants and limit of detection was also computed which showed agreement in theoretical and experimental results. Lastly, computational studies were conducted to investigate the ligand–anion interaction in three-dimensional setting by performing frontier molecular orbital (FMO), UV-Vis, natural bond orbital (NBO) analysis and global reactivity parameters (GRPs) elucidation. Study showed that chemosensors’ chemical reactivity and charge transfer phenomena is explained by the band gap of orbitals. A relatively stable HOMO/LUMO orbitals with grater values of hardness is examined. Further, NBO study described that the intermolecular charge transfer and hyper-conjugation played a significant role in stabilizing the compounds. The findings demonstrated that (4a–e) quinoline-based chemosensors are viable for advance assessment in optimizing excellent chemosensors for fluoride ions.