Design?Synthesis And Performance Study Of Benzimidazole-based Trivalent Metal Cations Fluorescent Sensor

On account of its high sensitivity and high selectivity,fluorescence chemosensor for sensing metal ion is increasing important.Because of the paramagnetic nature of many heavy metal ion,it is generally believed that probes with a fluorescence enhancement signal when interacting with analytes are much more efficient.Compared to fluorescence quenching and enhancement,a ratiometric fluorescent response due to ON-OFF-ON process at two different acquisition wavelengths provides advantage over ON-OFF and OFF-ON based chemosensors and is considered to be more efficient,not only because of its higher sensitivity but also because of its better resistance to background fluorescence and variation of fluorescent probe concentration.So development of a ratiometric fluorescent probe for metal ion is very meaningful.The main contents of this thesis are shown as following:In chapter 1,the sensing principles were stated at first.It is necessary to detect trivalent metal cations because of its damage and function for human?animal and plant.A detailed review was carried out about the research progress of the fluorescent sensors for trivalent cations and the ratiometric fluorescent probes.Then we put forward our design ideas and research topics.In chapter 2,a novel ratiometric fluorescent sensor bearing two benzimidazole groups for Cr3+ and Fe3+ has been synthesized.The sensor showed a ratiometric fluorescence response with an enhancement of the ratios of emission intensities at 443 and 378 nm from 0.17 to 3.21 for Cr3+.The ratios of emission intensities at 443 and 380 nm were enhanced from 0.40 to 2.09 for Fe3+.Fe3+ revealed significant adsorption in the UV-vis region and other metal ions including Cr3+ caused no change to the absorption intensity of the receptor,which can be used to discriminate Cr3+ and Fe3+.In addition,a series of similar compounds were synthesized to study the sensing mechanism.In chapter 3,a series of click reaction-based fluorescent molecules have been synthesized.We investigated the selectivity for metal cation through changing the binding sites.