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-, H2PO4-, HSO4- and ClO4- by naked-eyes and UV-vis spectra changes in aqueous solution (H2O/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. H-1 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 x 10(3) M-1. The detection limitation of AcO- with the sensor 3 was 1.0 x 10(-6) mol L. (C) 2011 Elsevier B.V. All rights reserved.