Synthesis And Properties Of Chemosensors For Cyanide Based On Benzothiazole

This thesis mainly expounds the application in industrial production,the harm in daily life of cyanide and also summarizes the research direction and progress of cyanide anion chemosensor in recent years. As benzothiazole and its salts have strong electron withdrawing ability, a conjugated system after connecting with chromophore will form. Cyanide anions can change the structure of the system and lead to change of the spectra of the compounds. This type of chemosensors have the advantages of high selectivity, low detection limit, strong design ability, and so on.The purpose of this thesis is mainly on developing and designing cyanide anion chemosensors with the central group of benzothiazole. The research was developed around Michael addition reaction and copper ion substitution reaction mechanism(1) Benzothiazole- coumarin sensors 1-4 for cyanide(2) Benzothiazole- indole compounds and their derivatives 5-10 for cyanide(3) Benzothiazole- Schiff based chemosensors and its comparable compounds 11-13(4) Pyridine salt chemosensor compounds 14-18In benzenethiazole-coumarin system, four compounds(1-4) were synthesized and characterized and their crystal structures were obtained firstly. Compounds 1-4 have chemical reaction with cyanide anions, wherein compounds 1-3 can directly recognize cyanide anions by the Michael addition reaction. The color of compound 3 changes from yellow to colorless, at the same time, green fluorescence was almost completely quenched upon the addition of cyanide anions. Coumarin benzothiazolyliden compound 4 can can recognize cyanide anions with fluorescence turn-on response based on the copper complex ensemble displacement mechanism.We found that compounds 1-4 have a good selective recognition for cyanide anion with very low detection limit.Compounds 3 and 4 show a relatively good recognition ability for cyanide anions with obvious color change, which can be seen by naked eyes.In benzenethiazole-indole system, six compounds(5-10) were synthesized and characterized. These chemosensors can detect cyanide anions by the naked eye in natural light and have a very good selectivity. By comparing with the traditional similar sensors, the absorption spectrum of chemosensors 5-7 have very different trends. The 1H NMR analysis showed that cyanide anions are bonded to the C=N of benzothiazole salt or the 4- position of pyridine ring by Michael addition reaction. At the same time, the NH of indole forms hydrogenbond with cyanide. The two forms of interaction affect the physical properties of the anions,which lead to obvious changes in color and fluorescence.Compounds 11-13 were synthesized in Benzothiazole- Schiff base system and systematical characterization was carried out. Taking 12 as an example, the X-ray single crystal was analyzed.The optical physical properties of the three compounds were analyzed in detail. Compounds 12 and 13 have very high fluorescence quantum yield and their selective recognition for cyanide anion can be realized with copper ions exchange reaction. They are fluorescence enhanced chemosensors and can be used repeatedly. Compound 11 can achieve rapid and efficient recognition to cyanide anion in an instant and compound 11 is also capable of selective recognition of copper ions. The recognition process of two kinds of ions can be visible to the naked eye, so we can make it into the test paper to realize the detection of cyanide anions. It has an important application value for the recognition of the cyanide anion in the actual production and life.A total of five pyridine salt compounds are obtained and systematically characterized in pyridine salt system. The synthetic route is simple with easy purification. The physical properties of the compounds were analyzed by UV-Vis absorption spectra and fluorescence spectra. The investigation indicates that those pyridine salts can recognize cyanide anions with high sensitivity and good selectivity. Color change of the solution can be detected by the naked eye upon the addition of cyanide anion. The recognition mechanism of the compounds are analyzed by Job's plots and 1H NMR. The recognition mechanism of those compounds containing hydroxyl group is hydrogen bonding, and the compounds without hydroxyl group is Michael addition reaction.