Colorimetric recognition of acetate anions in aqueous solution using charge neutral azo derivatives

Abstract Two novel highly sensitive colorimetric acetate anion receptors: 4-phenylazo-2-hydroxy-benzaldehyde 4-nitrophenylhydrazone ( 1 ) and 4-phenylazo-2-hydroxy-benzaldehyde 2,4-dinitrophenylhydrazone ( 2 ) based on azo derivative have been designed and synthesized. UV–vis experiments show that receptor 1 and receptor 2 can selectively recognize acetate in DMSO and even in 9/1 DMSO/H 2 O (v/v) mixtures. Meanwhile the color changes induced by anions can provide a way of detection by ‘naked-eye’. The further insights to the nature of interactions between receptor 1 , 2 and AcO − have been investigated by 1 H NMR titration experiments.