Synthesis And Properties Of Ion Receptors Recognition Based On Benzimidazole And Acylhydrazone

In recent years, it is very important that the quantitative detection and qualitative analysis of heavy metals and transition metal ions in clinical, food safety and environmental detection;Also, anion detection plays an extremely important role in chemical, life sciences and environmental science. It has a very important research significance to design the simple structure, ease-to-synthesis and water soluble of colorimetric /fluorescent sensor, which could detect heavy metal ions and anions with high selective and specific sensitive. In view of this,the paper designed and synthesized several receptor molecules, which could detect specific anion and cation. In addition, we studied its ion recognition performance. The thesis including the following four parts:Chapter 1: This chapter introduces the concept of molecular recognition, the mechanism and research value. It mainly elaborated the current situation of cyanide anion and cation recognition based on subject and object function. According to recognition mechanisms of these sensors, it can be divided into the following five categories: the first kinds are deprotonation based ion sensors; the second kinds are hydrogen bonds based ion sensors; the third kinds are specific reaction based ion sensors; the fourth kinds are the coordination based sensors; the fifth kinds, based on other recognition mechanism.Chapter 2: A novel cyanide selective fluorescent chemosensor L1 based on benzimidazole group and naphthalene group as the fluorescence signal group had been designed and synthesized. The detection of cyanide was performed via the deprotonation of the –OH and –NH and intramolecule hydrogen bond process, which could be confirmed by 1H NMR, 13 C NMR and ESI-MS. The receptor could instantly detect CN- anion over other anions such as F-, Cl-, Br-, I-, AcO-, H2PO4-, HSO4-, SCN-and ClO4-by fluorescence spectroscopy changes in aqueous solution(H2O/DMSO, 8:2, v/v) with specific selectivity and high sensitivity. The chemosensor L1 produced a band at λmax = 388 nm in the absorption spectrum recorded at a 2×10-5 mol/L concentration of the sensors in a H2 O system, the emission spectrum of L1, which is excited at 360 nm, exhibits an emission maximum at 450 nm with a low quantum yield(Φf = 0.34). Changes in spectral pattern were observed only in the presence of added 20 equivalent of CN- and showed a strong fluorescence response with a increasement quantum yield(Φf = 0.50), and responded with a dramatic color change, from pale blue to mazarine. No change in spectral pattern for receptor L1 in the presence of other anions suggests either a very weak or no interaction between these anions and the compound.Moreover, further study demonstrates the detection limit on fluorescence response of the sensor to CN- is down to 8.8×10-8 mol/L, which is far lower than the WHO guideline of1.9×10-6mol/L. Test strips based on L1 were fabricated, which could act as a convenient and efficient CN- test kit to detect CN- in pure water for “in-the-field” measurement.Chapter 3: A novel host L2 based on the acylhydrazone group as binding site andnaphthalene ring as signal groups has been designed and synthesized. Sensor L2 could detect to CN- in the presence of other competitive anions by dual channel of fluorescence and UV-vis spectrum with highly efficient and rapid. In the H2O/DMSO(4:6, v/v) solution of L2 containing the other competition anions, only the addition of CN-and the L2 solution responded with a dramatic color change, from colorless to yellow, and other anion is not obvious changes on the “naked eye” and spectrum. In addition, the detection limit on UV-vis and fluorescence response of the sensor to CN- is down to 6.9×10-7 mol/L and 1.20×10-9mol/L, respectively, which are far lower than the WHO guideline of 1.9×10-6mol/L.Moreover, test strips based on L2 were fabricated, which could act as a convenient and efficient CN- test kit to detect CN- in aqueous solution for “in-the-field” measurement. We believe that these characteristics of L2 make it attractive for further molecular modifications and underlying applications as fluorescence sensor for CN-in aqueous solution.Chapter 4: A highly selective host L3 based on an acylhydrazone was designed and synthesized, which could instantly detect heavy metal ion Cu2+ in DMSO without interference by other cations. It is very interesting that L3 could recognize CN- without interference, when we changed our experiments system to DMSO/H2O(2:8, v/v) in the aqueous system. Sensor L3 could detect to Cu2+in the presence of other competitive cations(Fe3+, Hg2+, Ag+, Ca2+,Cu2+, Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+, Mg2+) by UV-vis spectrum with highly efficient and rapid. In the DMSO solution of L3 responded with a dramatic color change, from colorless to dark yellow color, and other cations are not obvious changes on the “naked eye” and spectral.In addition, the detection limit on UV-vis response and “naked eye” of the sensor to Cu2+is down to 3.6×10-8 mol/L and 5.0×10-7 mol/L, respectively. At the same time, test strips based on L3 were fabricated, which could act as a convenient and efficient Cu2+ test kit to detect Cu2+. The research shows that the sensor L3 respond to Cu2+through coordination.