Synthesis Of Thiosemicarbazone Derivative Receptors And The Anion Recognition Properties

Molecular recognition is the process that host molecular form binding with guest molecular selectively and produce some special function, which is an important research area in supramolecular chemistry. The development of anion coordination chemistry is delayed compared with neutral moleculars and cations. It is therefore necessary to construct novel anion receptors. In this thesis, we have synthesized some novel thiosemicarbazone derivative receptors and studied on their anion recognition properties. The major contents are as follows:1. Researches in the development of anion recognition were briefly reviewed. The coordination chemistry of anions has received little attention over the last 30 years when compared to that devoted to coordination chemistry of cations. Therefore a number of anion recognition systems have been reported. The content of this chapter includes: (i) Structural characters of anions. (ii) Noncovalent interactions existed in anion coordination, (iii) The development of anion recognition researchers of thiosemicarbazone derivative receptors.2. Three N-arylthiosemicarbazone receptors of 4'-acetylbenzo-15-crown-5 have been prepared and characterized. The binding properties of the receptors 3a, 3b, 3c with anions such as F^-, Cl^-, Br^-, I^-, CH₃COO^-, C₃H₇COO^-, ClO₄^- and NO₃^- in acetonitrile were examined by UV-Vis and ¹H NMR spectroscopy methods. A clear color change was observed from colorless to light 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 for F^-, CH₃COO^- and C₃H₇COO^-, but no evident binding with Cl^-, Br^-, I^-, ClO₄^- 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 compound 3a, 3b, or 3c and anions, while ¹H NMR titrations confirmed hydrogen interaction between the receptors and anions.3. Three new glyoxal bisarylthiosemicarbazone receptors were designed and synthesized. The binding properties of the receptors with anions such as F^-, Cl^-, Br^-, I^-, CH₃COO^- C₃H₇COO^-, HSO₄^- and NO₃^- in DMSO were examed by UV-Vis and ¹H NMR spectroscopy. A clear color change was observed from colorless to deep yellow upon addition of F^-,CH₃COO^- and C₃H₇COO^- to the solution of the three receptors in DMSO. The results showed that the three receptors had a better selectivity for F^-,CH₃COO^- and C₃H₇COO^-, but had no evident binding with Cl^-, Br^-, I^-, HSO₄^-and NO₃^-. It was regular that the three receptors had different binding ability with F^- and CH₃COO^-. The UV-Vis data indicated that a 1:1 stoichiometry complex was formed between receptors and the three anions. ¹H NMR titrations and solvation effect confirmed hydrogen interaction between the receptors and anions.4. A new series of dibenzoyl bisarylthiosemicarbazone receptors (1, 2 and 3) have been synthesized by simple steps in good yields. Their anion recognition properties were studied by UV-vis and ¹H NMR spectroscopy. The result showed that receptors 1, 2 and 3 had no evident binding with Cl^-, Br^-, I^-, NO₃^- and HSO₄^- but a better selectivity for F^-, CH₃COO^- and H₂PO₄^-. Upon addition of the three anions to the receptors in DMSO, the solution acquired a color change from colorless to dark yellow that can be detected by the naked-eyes, thus the receptors can act as fluoride ion sensors even in the presence of other halide ions. The data showed that it was regular that the three receptors had different binding ability with the three anions. For the same anion, the association constants followed the trend: receptor l>receptor 3>receptor 2. The UV-vis data indicates that a 1:1 stoichiometry complex is formed through hydrogen bonding interactions between compound 1, 2 or 3 and anions.