Design and synthesis new colorimetric receptors for naked-eye detection of biologically important fluoride and acetate anions in organic and arsenite in aqueous medium based on ICT mechanism: DFT study and test strip application

Abstract

Novel three colorimetric anion receptors R1, R2 and R3 have been designed and synthesized via condensation reaction and characterized using IR, MS, and NMR spectroscopic techniques. Anion sensing properties were studied using colorimetric, UV-vis titration, ¹H NMR titration, and Cyclic Voltammetric Studies. Comparing the UV-visible titration data of the receptors R1 and R2, R2 showed high redshift (∆λ_max) in the mixed competitive solution (DMSO: H₂O, 9: 1; v/v) of about 155 nm, 157 nm, 169 nm for Na⁺F^-, Na⁺AcO^-, and Na⁺AsO₂^- ions with LOD of 0.23 ppm, 0.18 ppm, and 0.30 ppm, respectively. The observed spectral change of receptor R2 is due to the anion-induced deprotonation of the OH proton, which is confirmed by UV-vis titration, ¹HNMR titration, and cyclic voltammetric studies. Theoretical studies via DFT calculation were carried for R1 and R2 to optimize the structure and to explain the anion-binding mechanism. The application of designed receptor R2 was successfully demonstrated for the detection of F^- and AsO₂^- ions using a test strip. The receptors R1 and R2 proved itself to be potentially useful for real-life application by sensing F^- and AcO^- ions in real samples like toothpaste, mouthwash, vinegar and seawater in a complete aqueous medium.

Keywords: Acetate; Arsenite colorimetric chemosensor; Fluoride; TD-DFT; Test strip.