Synthesis And Anion Recognition Properties Of Aroyl Thioureas

Molecular recognition is an important area of supramolecular chemistry, it means selectively bind to receptors on the substrate and produce a specific function in the process. Qualitative and quantitative detection of anions has drawn increasing attention because of the important role of anions in biological, environmental and chemical industries, etc. Thiourea is an excellent hydrogen bond donor, providing dual hydrogen binding sites. The major contents are as follows :1. We synthesized 24 compounds and charaeterized them. The binding properties of the compounds with anions such as F-, Cl-, Br-, I-, Ac O-, HSO4-and Cl O4- were examined by UV-Vis 、 IR and 1HNMR spectroscopy methods. The results showed that 11 receptors can recognize F- and Ac O-, color changes can be observed by naked-eyes with addition of the two anions to the receptors 1, 9 and 17.2. UV-Vis titration experiments showed that absorbance values have a good linear relationship with concentration of anions when the anions were added in receptors 1, 4, 17, 20 and 23, correlation coefficients were above 0.95, up to 0.9978. The detection limit to Ac O- and F- is 5 × 10-6 mol/L when the concentration of receptors are 2 × 10-5 mol /L.3. The mechanism is that strong acidic NH deprotonated by little anions first and the less acidic NH deprotonated by excess anions. The data of Job-plot showed the binding stoichiometry.4. The binding properties of receptors were examined in the aqueous phase. The results showed that the receptors 1 and 17 can recognize F- and Ac O- when the water content is lower than 15%, and receptor 9 can recognize F- and Ac O- when the water content is lower than 20%.