The Studies On Synthesis Of Coumarin Schiff-base Ligands As Metal Ions Fluorescent Sensors

Compared with traditional methods, fluorescent probes have a series of advantages, such as high sensitivity, good selectivity, fast response, easy to operate, no destroyed of the sample, low cost and don’t affected by external electromagnetic fields. In biochemistry, molecular biology and environmental science, the fluorescent probes for metal ions analysis is the most and thorough studied aspect. As we all know, many metal ions are essential trace elements for human. However, some of the metal ions excess enrichment in the body would have serious damage on human health and environmental. Therefore, to design and synthesis fluorescent probes to detect these toxic metal ions has attracted a lot of people’s attention.Coumarin compounds not only have many distinct pharmacological activity, but also outstanding candidate fluorophore molecular for the fluorescent sensors. In visible light, coumarin is colorless or pale yellow crystals; Under UV light, it will emit visible blue fluorescence. Its fluorescence enhancement when we import hydroxyl at7-rear. For8-formyl-7-hydroxy-4-methyl coumarin Schiff-base, there are nitrogen and oxygen atoms belong to7-hydroyl and C=N, which can get the stable six ring coordination complex with metal ions.In this paper, a series of Schiff-base derivatives based on8-formyl-7-hydroxy-4-methyl coumarin have been designed and synthesized. The paper is organized as follows:In the first chapter, we give out a brief introduction to the basic background knowledge of coumarin, fluorescent probes and the research process of various metal ions in nearly two years. In the second chapter, by reaction of coumarin and rhodamine, we synthesized a new "off-on" type Schiff base fluorescent probe. The sptral properties experimental tests revealed that, in acetonitrile the ligand has good selectivity and high sensitivity for the calcium ions. In the third chapter, we designed and synthesized a novel fluorescent probes for iron ions. Due to the characteristics of iron ions, the fluorescent probe for iron ions reported previously are mostly quenched type. However, the new synthesised iron fluorescent probe is enhanced fluorescence type. So it has better selectivity and higher sensitivity. In addition, in the fourth and fifth part of the paper, we also synthesized three other different coumarin schiff-base ligands. Through experimental results, we found that these probes have some recognition effect for aluminum ions and zinc ions. We believe that these fluorescence sensors have potential application in environmental, biological and medical areas.