Spectroscopic studies of colorimetric receptors for detection of biologically important inorganic F−, AcO− and H2PO4 − anions in organo-aqueous medium: Real-life application

Abstract

Two new 4-nitrobenzylidene based receptors 2-((E)-(((E)-4-nitrobenzylidene) hydrazono) methyl)-1H-indole (R1) and 2-((E)-(((E)-4-nitrobenzylidene)hydrazono)methyl)-1H-pyrrole (R2) have been designed and synthesized by the simple condensation reaction and characterized by using spectroscopic techniques. The receptors exhibited high sensitivity and selectivity towards biologically important anions such as F−, AcO− and H2PO4 − in DMSO and sodium salts F−, AcO− and H2PO4 − in aqueous medium (9:1 v/v, DMSO: H2O). The receptors R1 and R2 dispensed high sensitivity towards sodium arsenite and detection limit were found to be 0.143 ppm and 0.32 ppm in (9:1 v/v, DMSO: H2O) reflect the stable complex formation of the receptor with AsO2 − ion in aqueous medium. 1H NMR titration carried out to understand the nature of interaction between receptor R1 and F− ion. Cyclic voltammetric studies performed for receptors R1 and R2 in DMSO exhibited shift in oxidation and reduction peak with addition of basic F− ion signifying strong interaction between receptors and anions. Interesting, receptor R1 exhibited high selectivity for AcO− ion in the different range of pH from (6–11). Furthermore, receptor R1 and R2 showed colorimetric sensing of F− and AcO− ion present in commercially available toothpaste and vinegar in the form of Na+F− and Na+AcO− in aqueous medium. © 2020 Elsevier B.V.