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

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(2)PO(4)(-), HSO(4)(-) and ClO(4)(-) by naked-eyes and UV-vis spectra changes in aqueous solution (H(2)O/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. (1)H 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).