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

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.