A Colorimetric Receptor Based on Schiff-Base Bearing Azo-Phenolic Hydroxy Group

A novel N-(2-hydroxy-5-chlorodibenzophenone)-N0-2-hydroxy-5-azophenyl-benzaldehyde-1,2-diaminobenzene receptor has been synthesized by simple steps with good yields. The anion recognition properties were studied by ultraviolet-visible spectroscopy. The resultsshowed that the receptor had a higher affinity to F^-, AcO^-, and H₂PO₄^-, but no evident binding with Cl^-, Br^-, and I^-. Upon addition of the three former anions to the receptors in DMSO, the solution exhibited an obvious color change from colorless to yellow, which could be observed by the naked eye, thus the receptor could act as a fluoride ion sensor even in the presence of other halide ions. The UV-Vis data indicates that a 1:1 stoichiometric complex is formed through hydrogen bonding interactions between receptor and anions.