The anion recognition properties of hydrazone derivatives containing anthracene

A series of artificial receptors, hydrazone derivatives containing anthracene, have been designed and synthesized. The interaction of these receptors with biologically important anions was determined by UV–vis, fluorescence and ¹H NMR titration experiments and theoretical investigation. Results indicate that the receptor (1) without NO₂ shows no binding ability for various anions. The other receptors (2 and 3) show the highest binding ability for acetate (AcO⁻) among studied anions (fluoride (F⁻), dihydrogen phosphate (H₂PO₄⁻), chloride (Cl⁻), bromide (Br⁻), iodide (I⁻)); and the binding ability for AcO⁻ is not interfered by the existence of other anions. The additions of AcO⁻, F⁻ and H₂PO₄⁻ can arouse different degrees of fluorescence quenching. ¹H NMR titration shows that the interaction between the receptor 2 and F⁻ firstly depends on the hydrogen-bond formation; later the interacted site NH is deprotonated and the added F⁻ forms hydrogen bond with the near CH in Schiff base. Moreover, visual color changes accompany guest binding, enabling this system to act as colorimetric anion sensors.