Synthesis of thiosemicarbazone derivative receptors and their anion recognition properties

Three unknown neutral thiosemicarbazone derivative receptors were synthesized in good yields. The binding properties of the receptors with anions such as F-, Cl-, Br-, I-, CH3COO-, C3H7COO-, Cl O-4(-) and NO3- in acetonitrile were examined by UV-Vis and H-1 NMR spectroscopy methods. A clear color change was observed from colorless to fight yellow upon addition of F-, CH3COO- or C3H7COO- to the solution of the three receptors in acetonitrile. The results showed that the three receptors had a better selectivity to F-, CH3COO- and C3H7COO-, but no evident binding with Cl-, Br-, I-, Cl O-4(-) and NO3-, and the association constants followed the trend: F-> C3H7COO-> CH3COO-, while regularly the three receptors had different binding ability with the three anions because of the electronic effect. The UV-Vis data indicated that a 1 : 1 stoichiometry complex was formed between compounds 3a, 3b, 3c and anions, while H-1 NMR titrations confirmed hydrogen interaction between the receptors and anions.