Synthesis, Optical Properties Of Coumarin Derivatives And Their Application As Fluorescent Sensors For Metal Ions

Coumarin derivatives are a kind of heterocyclic compounds based on a-benzopyrone. Coumarin derivatives have been reported to show a wide range of biological activities, such as anti-HIV, anti-cancer, anti-inflammatory, antioxidant and anti-angiogenesis properties. Moreover, this kind of compounds have also been reported to possess good photostability and high fluorescent quantum yield.In recent years, interdisciplinary cross among chemistry, biology and materials science has been increasing. Fluorescent ways to track working process of small organic molecules in biosystem and fluorescent probes for detecting significant pollutants in biosystem or environment have become research focus. For their good performance, coumarin derivatives have been widely used in this field.In this thesis, a short review on newly synthetic methods of coumarin derivatives for recent years and their applications as fluorescent probes is presented, and several series of coumarin compounds are synthesized, among which some compounds are researched as fluorescent probes for metal cations. The main contents are summarized as follow:1. Synthesis and optical properties of novel5-pyrazyl-2-benzofuranyl-1,3,4-oxadiazole derivatives.A series of novel5-pyrazyl-2-benzofuranyl-1,3,4-oxadiazole derivatives7a-f has been synthesized from6-methoxy-3-methylbenzofuran-2-carboxylic acid which was obtained through intramolecular rearrangement reaction of3-bromocoumarin and ethyl3-aryl-1H-pyrazole-5-carboxylate. The structures of compounds obtained were determined by IR,1H NMR and ESI-MS spectra. Typically, the spatial structure of compound7e was determined by using X-ray diffraction analysis. UV-vis absorption and fluorescence spectral characteristics of the compounds in dichloromethane and acetonitrile were investigated. The absorption maxima and the maximum emission spectra of compounds7a-f in two different solvents were mainly dependent on groups in N-1position of pyrazole moiety. In addition, the absorption and emission spectra of these compounds change with increasing solvent polarity. 2. New quinolin-8-yl-7-(diethylamino)coumarin-3-carboxylate as a selective chelation-enhanced fluorescence (CHEF) chemosensor for copper ion.A new fluorescent chemosensor composed of a coumarin fluorophore and an8-hydroxyquinoline ionophore for Cu2+was synthesized and characterized by1H NMR, IR and ESI-MS. Its selectivity towards metal ions in acetonitrile was investigated by UV absorption and fluorescence spectroscopy. The results showed that this chemosensor exhibited good selectivity toward Cu2+over other metal ions by enhancement of fluorescence intensity. The detection limit of Cu2+was determined to be0.58μM, a satisfying level to detect Cu2+in micromolar scale.3. Synthesis, optical properties of of novel coumarin acylhadrazones and their fluorescence selectivity toward metal ions.Four coumarin acylhadrazones la-d were synthesized by the reaction of7-(diethylamino)coumarin-3-carbohydrazide and different aromatic formaldehydes. The structure of compounds la-d was characterized by1H NMR, IR and ESI-MS. UV-vis absorption and fluorescence spectral characteristics of the compounds were measured in dichloromethane, acetonitrile, ethanol and dimethyl sulfoxide. Their selectivity towards metal ions in acetonitrile was investigated by fluorescence spectroscopy. The results indicated that compound lc showed good selectivity towards Cu2+, the binding of Cu2+caused a huge fluorescence quenching, which can be used to detect Cu2+from the other metal ions.