The Synthesis Of Functional Ionic Liquids And The Application As Receptors In The Anion Recognition

Recently, great interest has been attracted in design and synthesis artificial receptors which can recognize anions selectively, because anions play important roles in the life sciences and chemical processes. Currently, many neutral organic compounds with hydrogen bond donor groups have been focused as anion receptors using hydrogen-bonding to interact with anions, such as the receptors containing urea or thiourea group.This thesis is mainly about the synthesis of functional ionic liquids and the application as receptors in the anion recognition. It involves two sections. The first section is about the synthesis of imidazolium based ionic liquids containing urea moiety and the recognition of combined anions by these ionic liquids. The second section is about the synthesis of quinoline based ionic liquids containing urea moiety and the high selective recogniton of fluoride by these ionic liquids.In the first section, a series of imidazolium based ionic liquids containing urea moiety have been synthesized and used as receptors to recognize anions.1H NMR spectra have been used as the detection means. Addition of halides in ionic liquid receptors result in significant upfield shifts of the urea protons, while halides cause the downfield shifts of the urea protons of the neutral receptor which has the similar structure with the ionic liquid receptors. The different tendencies of the chemical shift changes indicate that the recognition mechanism of ionic liquid receptors is completely different from the neutral receptor. The urea protons of ionic liquid receptors change dramatically in the presence of combined anions (BF4-, PF6-and BPb4-) which have the difficult abilities to form hydrogen bond. However, these combined anions can not cause any change of the chemical shift of the neutral receptor. Therefore, these ionic liquid receptors can recognize combined anions which can not be recognized by neutral receptors. The saturated curves of the1H NMR titrations suggest1:1binding stoichiometry. The results suggest that with the addition of adscititious anion the anion exchange would be occured, which is the adscititious anion exchanging with the anion of ionic liquid receptor then forming a new ionic liquid. Anion exchange can trigger the conformational change of the cation of the ionic liquid. The conformational change is detected by X-ray diffraction analysis and Gaussian-03calculation. In ionic liquid receptors OAc-interact with urea moiety by hydrogen bond and the urea protons are on the downfield. After the anion exchange the urea moiety are influenced by the ring current of the imidazolium ring and the protons are on the upfield. Through the conformational change, the intramolecular hydrogen bonds are destroyed and the urea protons are influenced by the ring current of imidazolium ring. Therefore, the urea protons shift to the upfield.In the second section, a series of quinoline based ionic liquids containing urea moiety have been synthesized and used as receptors to high selectively recognize anions through the fluorescence emission spectra, UV-vis spectra, naked eye and1H NMR spectra. The results show that these ionic liquids can recognize fluoride selectively.(1):Fluoride can increase the fluorescence intensity of the ionic liquid receptors nearly300times, OAc-make fluorescence intensity increase100times, while other anions can not cause any change of the fluorescence intensity of the ionic liquid receptors.(2):Fluoride and OAc-can change the colour of the ionic liquid receptors from colourless to red.(3):The UV-vis of the ionic liquid receptors are on the320nm, while adding fluoride the peak of320nm disappears then forming two new peaks at276nm and342nm.(4):Fluoride make the urea protons of the ionic liquid receptors shift to the downfield. The recognition is also accounted to form a new ionic liquid with the fluoride as its anion through the anion exchange. We synthesized the ionic liquid containing fluoride ([Equl]F) and its fluorescence emission spectra, UV-vis spectra, naked eye detection are similar with that of adding fluoride to ionic liquid receptors. X-ray diffraction analysis and Gaussian-03calculation indicate that the fluoride interact with urea moiety by hydrogen bonds in the ionic liquid [Equl]F, which make the urea protons of [Equl]F shift to the downfield.