The Synthesis And Properties Of New Coumarin Fluorescent Compounds And Fluorescent Probes

As an important group of organic heterocycles, coumarin derivatives are found to possess versatile biological activities. Besides, they have unique photochemical and photophysical properties. Coumarin is a kind of none fluorescent substance, while coumarins with an electron-donating substituent in position 7 along with an electron withdrawing or electron delocalizing substituent in position 3 are known to exhibit particularly strong fluorescence. There are so many advantages of coumarin derivatives such as high fluorescence quantum yields; large Stokes shifts and good photostability, so design and synthesis of novel coumarin derivatives with fluorescent are very important.The crucial recognition events of chemistry, biology, and materials science are molecular recognition and assembly, micro detectction and research in the molecular line is of great importance. Information about these events can be conveniently transmitted to us via light signals emitted by purpose-built molecular fluorescent probes. Due to their difference from fluorophore, fluorescent probes can be divided into rhodamine derivatives, fluorescein derivatives, cyanine dyes, BODIPY derivatives and coumarin derivatives. Design and synthesis of fluorescent probes based on coumarins have become a hot point in chemosensor research because of their unique properties.In this thesis, a general introduction to the research progress on coumarin-based fluorescent compounds and probes was presented and many novel coumarin-based fluorescent functional moleculars are researched and developed. The main contributions are listed as follows.Firstly, fourteen coumarins were designed and synthesized. Furthermore, we study the effect of the subetituent groups on the fluorescent properties of coumarins. Taking 4-halo resorcinol as primary material, three halo-substituted salicylaldehyde were synthesized through formylation. Then, fourteen coumarins were synthesized via Knoevenagal reaction of halo-substituted salicylaldehede with compound containing active methylene group. Their structures were characterized by IR,'H NMR, MS and elemental analysis. Moreover, the relationship between the fluorescent properties of coumarins and structure was studied. Halo substituent in position 6 of coumarins bring about little excitation and emission wavelength change, but result in difference of fluorescence quantum yields; the fluorescent properties of coumarins mainly depend on substituent in position 3, strong electron withdrawing substituent in position 3 lead to strong fluorescence. Extending the conjugation degree, red shif of emission wavelength will take place.Secondly, five novel ion fluorescent probes based on coumarins were designed and synthesized. Furthermore, their fluorescent properties were investigated. Their structures were characterized by IR,1H NMR, MS and elemental analysis. These fluorescent probes are low fluorescent compounds. Upon mixing with Ca2+ in aqueous solution, the fluorescent of the system increases dramaticly, while the maxium emission wavelength has no change; Upon mixing with Mg2+ in aqueous solution, the fluorescent of the system has a moderate increase, the maxium emission wavelength also does not change. Upon mixing with Zn2+ in aqueous solution, the fluorescent of the system increases dramaticly, but there has a blue shift of the maxium emission wavelength.Thirdly, four novel coumarin-based fluorescent probes have been developed for highly selective detection of bisulfite anions in water. The fluorescent probes have shown a selective response to bisulfite over other anions via nucleophilic addition reactions. The fluorescent probes with salicylaldehyde functionality as recognition unit were synthesized via formylation reaction of Ethyl 6-substitute-7-hydroxycoumarin-3-carboxylate. The probes were weakly fluorescent compounds in weakly acidic aqueous. Upon addition of the probes to bisulfite anion in pH-buffered aqueous solution at room temperature, fluorescence intensity of the detected solution increased dramaticlly. The probes showed high selectivity toward bisulfite anions in water. A fluorescence analysis method for detection of bisulfite anions in water was established.