| Quinoxaline ring has unique optical and electrical properties as a result of the flat and rigid conjugated structure, so its derivatives have been applied to electroluminescence, photoluminescence and light emitting dopant fields. In addition, Quinoxaline derivatives exhibit a broad biological activity in the anti-HIV, antituberculosis, anti-inflammatory, anti-tumor, anti-viral, anti-protozoan, anthelmintics, anti-cancer and anti-bacterial etc. Moreover, synthesis and application of quinoxaline derivatives are one of the important research direction. Zinc is an essential trace element in the living body and involves a lot of life activities, thus the detection of zinc ion has important academic value and application prospects in the life sciences and environmental science research. Fluorescent probes have attracted considerable attention due to a lower cost, easy operation and high sensitivity. Zinc ion fluorescent probe, its molecular design is usually based on having excellent fluorescence properties as a combination of a heterocyclic chromophore, using pyridine, pyrrole and thiophene structures such as the recognition group. The application of quinoxaline derivatives as the recognition group or fluorophore in fluorescent probes has rarely reported in the literature. Based on excellent fluorescence properties of quinoxaline, a series of pyridyl quinoxaline and quinolinyl quinoxaline derivatives were systematically designed and synthesized to detect zinc ion. The structure of the probe was optimized by Gaussian software, and the relationship between the structure and properties of the probe is discussed by the space distribution of the electron cloud and the molecular orbital energy level.The first chapter introduces the recognition mechanism of fluorescent probes, the development of quinoxaline fluorescent materials and the development of zinc ion probe.Chapter II, quinoxaline derivatives were synthesized by an innovative one-pot method with iodine as a catalyst,o-hydroxy ketone and diamine as a starting material. The influence factors of the reaction are discussed. The reaction system has the advantages of mild conditions, fast response, toxicity catalyst and high yield.Chapter Ⅲ, a series of zinc ion fluorescent probes were synthesized with 2,3-bis(2’-pyridyl) quinoxaline derivatives as a recognition group and a fluorescent group by changing the 6-position substituents. The results show that the performance of probes are enhanced by introducing methyl, methoxy group and methoxyacyl group. The combination of quinoxaline probes and zinc ion have led to red shift and the enhancement of fluorescence strength, and probes exhibit strong selectivity and sensitivity for detectin zinc ion. Mechanism of ion recognition for probes may be intramolecular electron transfer.Chapter Ⅳ, three zinc ion probes substituted were designed and synthesized by introducing ammonia groups in the 6-position of 2,3-bis(2’-pyridyl) quinoxaline. The combination of these probes and zinc ion has led to the quenching of fluorescence spectra, and probes exhibit strong selectivity and sensitivity for detecting zinc ion. The mechanism may be the PET process.Chapter Ⅴ, according to expand the conjugated system of 2,3-bis(2’-pyridyl) quinoxaline, several quinoxaline derivatives were synthesized and were applied to the detection of zinc ion. Results show that these compounds have good performance as zinc ion fluorescence probe. In addition, the solution of the probe and zinc ion turned yellow from colourless liquid that can be utilized to the qualitative detection of zinc ions.Chapter VI, two probes was designed and synthesized by introducing trimethoxyphenyl and triphenylamine in 6-position of 2, 3-bis(2’-pyridyl) quinoxaline. The two probes were used to detect the water content in the organic solution. With increasing water content, the fluorescence intensity of the probe solution gradually decreases. The position of the fluorescence emission peak has not been changed. The reason may be charge-separated excited states lead to the end of the electron-donating group enhanced ability to form hydrogen bonds occurs due to rapid migration of electrons. The results show that the probe has a good efficiency in the detection of water content in DMF and acetone. The response speed is fast, the detection range is wide. When the water content is less than 0.1%, the fluorescence intensity of the probe solution is approximately linear, and the detection limit is reached to ppm. The detection range of the water content is related to the number of hydrogen bonds in the donor group, and the number of hydrogen bond is more, the detection range is wider.Chapter VII, two types of di-quinoxaline zinc ion fluorescent probe was designed and synthesized. The results showed that the two probes also showed enhanced fluorescence ratio response to zinc ion. But the position of the fluorescent emission peak show two different characteristics of red-shift and blue-shift. This difference is attributed to different substituent. The different substituents result in the change of intramolecular electron density. The intramolecular charge transfer is considered as the probe mechanism. In addition, two probes also display a high selectivity and sensitivity for detecting zinc ion.Chapter VIII, in order to further improve the properties of such probes, di quinolinyl quinoxaline derivatives(QP17-QP20) were designed and synthesized. Quinoline has excellent conjugated structure and fluorescence properties. Therefore, we have adopted the structure of quinoline containing pyridine instead of pyridine, and get a series of more excellent probes. The results show that these probes have a lower limit of detection and fluorescence characteristics than the corresponding pyridyl quinoxaline probe. For example, fluorescence intensity of the probe QP18 increased about 300 times after the addition of zinc ion, the detection limit also lows an order of magnitude.Chapter Ⅸ,the work of the full text are summarized, and the future prospect of quinoxaline fluorescence probes for detecting zinc ion was discuss. |
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