Design and synthesis of a novel chemosensor for simultaneous detection of CN−, HCO3− and AcO− anions and Fe2+ cation in an organic-aqueous environment: An experimental and Density Functional Theory studies

Abstract

• A novel Schiff base ligand, namely 2-((E)-(2-(1H-indol-3-yl)ethylimino)methyl)-4-((E)-(2-nitrophenyl)diazenyl)phenol (L) was synthesized. • The receptor (L) (5 × 10 −5 M) in DMF solution exhibited very good sensing behavior towards CNˉ, HCO 3 −, AcO− and Fe2+ ions. • The stabilization energy of the optimized complexes was more negative than the energy of free receptor (L) proving the greater stability of the formed complexes. • The reversibility of the synthesized receptor (L) was successfully approved. • The receptor (L) can be candidate as an operational colorimetric chemosensor with low-cost detection, high selectivity and nice reversibility in DMF solutions. A new azo–azomethine chemosensor, 2-((E)-(2-(1H-indol-3-yl)ethylimino)methyl)-4-((E)-(2-nitrophenyl)diazenyl)phenol, L, was synthesized and characterized by Infrared spectroscopy (IR), Ultraviolet–visible spectroscopy (UV-Visible) and Nuclear magnetic resonance spectroscopy (NMR) methods. The sensory properties of this Schiff base compound (L) were investigated in Dimethyl sulfoxide (DMSO)/H 2 O (9.5:0.5 v/v) solution. It was selectively sensitive to CN ˉ and HCO 3 ˉ and AcO ˉ anions, and in the presence of them, the color of solution L through deprotonating mechanism changed from yellow to orange. This chemosensor also sensitive to Fe 2+ . Then, by using Job's method and Benesi–Hildebrand equation, the binding stoichiometry of L with anions and binding constant (k a ) were determined (CN − : 1:1, 3.47×10 +5 ; HCO 3 − : 1:1, 2.44×10 +5 ; AcO − : 1:1, 1.76×10 +5 ), respectively. Also, the Limit of Detection (LOD) was calculated. Finally, the observed experimental results were confirmed by Density Functional Theory (DFT) calculations. A new Schiff base chemosensor, 2-((E)-(2-(1H-indol-3-yl)ethylimino)methyl)-4-((E)-(2-nitrophenyl)diazenyl)phenol, L, was synthesized. The L sensor successfully detected both cations (Fe 2+ ) and anions (AcO ˉ , CN ˉ , HCO 3 ˉ ) by the naked-eye and UV–Vis spectroscopy in an organic-aqueous environment. Through DFT calculations, the experimental results were confirmed. So, we believe that L can be an efficient sensor for detecting said ions in aqueous media.