Three N-benzamido N' phenylthiourea receptors were designed and synthesized and their interactions with anions such as CH₃CO₂^-, H₂PO₄^-, HSO₄^-, ClO₄^-, Cl^- and Br^- in acetonitrile and acetonitrile-water binary solvents were investigated by using absorption spectroscopy. The results showed that hydrogen bonding complexes were formed between receptors and anions, which turned the solution to yellow from colorless. It was found that the selectivity of receptors to anion could be efficiently tuned by increasing solvent polarity or by substitution at the N benzoyl moiety. The recognition mechanism and binding mode were discussed and the anion recognition was successfully applied to inorganic CH₃CO₂NH₄ in 10% H₂OCH₃CN. These findings are expected to be of significance for designing and developing novel color based anion sensors operated in aqueous solution.

Key words: N-benzamidothiourea, anion recognition, water-acetonitrile binary solvent, hydrogen bonding