Mercapto thiadiazole-based sensor with colorimetric specific selectivity for AcO − in aqueous solution

Abstract

A novel acetate selective anion sensor 3 based on azophenol and mercapto thiadiazole had been designed and synthesized. Sensor 3 behaves a single selectivity and sensitivity in the recognition for AcO − anion over other anions such as F −, Cl −, Br −, I −, H 2PO 4 −, HSO 4 − and ClO 4 − by naked-eyes and UV–vis spectra changes in aqueous solution (H 2O/DMSO, 5:5, v/v). The color of the solution containing sensor 3 had an obvious change from colorless to orange only after the addition of AcO − in aqueous solution while other anions did not cause obvious color change. 1H NMR titration results revealed that the binding process includes two steps: (i) hydrogen bonding interactions (for small quantities of acetate) and (ii) proton transfer between the sensor 3 and the coordinated anion (for high quantities of acetate). The association constant K a was 7.35 × 10 3 M −1. The detection limitation of AcO − with the sensor 3 was 1.0 × 10 −6 mol L −1.