Synthesis of an anion-selective chromophore based on hydrogen bonding and its application to analytical chemistry

Abstract

The development of artificial receptors for anions is of current interest in host-guest chemistry. In a dissertation, chromogenic thiourea based receptors were designed, and their anion sensing functions were evaluated by 1H-NMR and UV-Vis spectroscopies. In acetonitrile-water, 1,3-di(4-nitrophenyl) thiourea exhibited an effective color change for acetate and aliphatic carboxylates, based on a strong hydrogen bond-mediated complexation of the receptor with these anions. Essentially no responses were observed for various inorganic anions, such as dihydrogenphosphate and halide anions. The application of the receptors to food analysis, was also examined; the receptors were found to be useful for the determination of acetate in vinegar. As charged receptors, isothiourea-based anion receptors were designed, and their anion recognition function at the 1,2-dichloroethane/water interface was examined by dynamic interfacial tensiometry. The complexation kinetics of a thiourea-induced isothiourea receptor with such anions as H2PO4- and Cl- was dependent on the receptor concentration. Both the saturated interfacial concentration and the adsorption constant of the thiourea-induced isothiourea receptor were found to be larger than those of a mono-substituted isothiourea receptor, exhibiting formation of an effective hydrogen bonding between isothiourea group and anion at the interface. Thus, the importance of the hydrogen bonding functions of the thiourea and isothiourea for anion recognition in the bulk solutions as well as at liquid/liquid interfaces was clarified in the present study.