Research On Michael Acceptor As Probe For Cyanide

This thesis introduces the application and endanger of cyanide (cyanide anions) andsummarizes the research progress of cyanide fluorescence sensors in recent years. Based onthe advantages of Michael acceptors of high selectivity, low cost and high designability, thisthesis is devoted to explore Michael acceptors as cyanide sensors and focuses on theinvestigation on the intramolecular hydrogen-bonding activated Michael acceptors. Thisthesis is carried on from two systems of2′-hydroxy chalcone sensors and amidocoumarinsensors.(1)2′-hydroxy chalcone sensors1-4for cyanide(2) amidocoumarin sensors5-13for cyanide To2′-hydroxy chalcone sensors system, four new fluorescent probes (compounds1-4) andtwo cyanide ionic bonding compounds has been synthesized and characterized in detail. All thefour compounds are fluorescent probes with compounds1-3as fluorescence turn-on cyanideprobes and compound4as dual signal fluorescence probe. They all respond with highselectively and sensitivity to cyanide. Among them, compounds3and4exhibit betterrecognization ability to cyanide and achieved the recognition of cyanide in aqueous media withdetection limit of7.2μM and3.2μM, respectively. The investigation indicates that theintroduction of electron-withdrawing group can improve activity of compounds as Michaelreceptors, and then improve the recognition ability of the sensors. In addition, we explored therecognition mechanism of the sensors for cyanide and demonstrated this reaction is Michaelreaction and the importance of intramolecular hydrogen-bonding activating the neighboringcarbonyl oxygen for the fast sensing of cyanide anions.To amidocoumarin system, nine compounds (compounds5-13) and the bondingcompounds (5-CN and6-CN) of5and6with cyanide anions have been synthesized and thecrystal structures of5-CN and6-CN have been obtained. The photophysical properties wereinvestigated. The investigation indicates that replace aniline (compound5) by benzylamine(compound6) can eliminate the TITC effect of benzamide and then the compound exhibit afairly good fluorescence properties (Φ5=0.002, Φ6=0.11).7-Diethylaminocoumarin-3-carboxamide derivatives (compounds9-13) exhibit excellent photophysical properties and arestrong fluorescent compounds with their fluorescent quantum around0.3, which is becausethis kind of compound has ICT and TICT double fluorescence. The recognization propertiesof the compounds for cyanide anions were investigated systematically. The investigationindicates that intramolecular hydrogen bond can activate Michael receptor and improve theability of detecting cyanide anions. Electron withdrawing group can promote the activity ofcompounds as Michael receptor, but electron-donating group is opposite. At the same time,the thesis also discussed the recognition mechanism between the sensors and cyanide anionsand demonstrated that the reaction is Michael reaction. Among this Michael reaction,itramolecular hydrogen bond is directly involved in the reaction and plays the role ofstabilizing unstable structure. Besides, this thesis firstly demonstrated that the additionreaction of coumarin derivative and cyanide anions is Michael addition reaction from crystal structure.