Studies On Quinoline-Azo Derivatives' Sensing Of Anions

Anion coordination research has recently been a hot topic of supramolecular chemistry because of the important role in a wide range of chemical and biological processes, and considerable attention has been focused on the design of host molecules that can recognize and sense anion species selectively through optical responses. Colorimetric and fluorescent detection and sensing are widely used either owing to the low cost or lack of expensive equipment or its high sensibility as a versatile tool in analytical chemistry, biochemistry, cell biology.The interaction between a series of hosts with anions were investigated via colorimetric detection and fluorescent spectroscopy. This thesis consists of five chapters as follows:1. The development of anion recognition in the past six years was briefly reviewed which contented: some basic concepts such as supramolecular chemistry, anion recognition, the colorimetric and fluorescent sensors for anions.2. A series of 5-(8-hydroxyquinoline)-azo-4'-substituted phenyl derivatives were synthesized and characterized by ¹H NMR, Their sensing of anions were explored using UV-vis spectroscopy or fluorescence spectroscopy.3. The interactions between artificial hosts and anions such as AcO^-, F^-, H₂PO₄^-, Cl^- and Br in acetonitrile were investigated by UV-vis spectroscopy. Results indicated that hydrogen-bonding complexes were formed between hosts and anions, which induced remarkable color change. It was found that the selectivity of hosts to anions could be efficiently tuned by substitution at the phenyl moiety. 5-(8-hydroxyquinoline)-azo-4'-methyl phenyl (MBAZQH) was capable of selectively binding fluoride anion over other anions. A 1:1 model complex was formed between MBAZQH and fluoride. The solution of MBAZQH turned red from colorless and a new absorption band peaked at 508 nm appeared. The association constant of MBAZQH-F^- complex was 2.5×10⁴ mol^-1 L. However, no obvious color changes were observed upon addition of one equivalence of other anions such as AcO", H₂PO₄^-, Cl^- and Br^-. This selective colorimetric assay for fluoride was developed.4. A 1:1 model complex between CNBAZQH and nickel ion was formed and the association constant of CNBAZQH-Ni²⁺ was 9.2×10⁶ mo^-1 L. The metal-ligand complex of CNBAZQH-Ni²⁺ was demonstrated to selectively sense HSO₄^- over other anions such as AcO^-, F, H₂PO₄^-, Cl and Br^- by using naked-eye colorimetric assay. The complex exhibits the remarkable color change from red to colorless upon introducing HSO₄^- in acetonitrile. The mechanism was proposed that the competitive binding occurred between HSO₄^- and ligand...