Abstract: Compounds based on p-nitrobenzene azophenol were designed and synthesized. The properties of absorption spectra and association constants of complexes between hosts and anions were investigated and compare. The results indicated that the three compounds, 1-naphthol-4-azo-4'-nitrobenzene,8-hydroxyl-quinoline-5-azo-4'-nitrobenzene and 1-phenol-4-azo-4'-nitrobenzene, could act as efficient chromogenic reagents for the anion sensing. Upon addition of various anions, the spectral profile and color of the solution of hosts changed significantly. The affinity of hosts for anions was measured by UV-Vis spectroscopic titration experiments. For the same host, the association constants followed the order of AcO^->F^->H₂PO^--4Cl^-, which was in agreement with the basicity order of anions. And for the same anions such as AcO^-, the association constants followed the order of 3(α-naphthol)>2(8-hydroxyl-quinoline)>1(phenol), which is attributed to electronic withdrawing effect of substituents and the conjugated system of host compounds.

Key words: Anion recognition, Naked-eye detection, Azophenol derivatives