Study On Mechanism Of Metal Ion Induced Abnormal Fluorescence Emission Of Rhodamine Dye

Series of14rhodamine amide derivatives were designed and synthesized to investigate themechanism of abnormal fluorescence emission of rhodamine dye in the presence of metal cationssuch as Cu2+and Hg2+. The potential applications of some rhodamine derivatives in fluorescencesensing and living cells imaging were also studied. The thesis includes six chapters:Chapter1is the introduction. The small molecule fluorescent probes and rhodamine-basedprobes were reviewed, including the fluorescence sensing mechanism and the application. Thefirst rhodamine-based fluorescent probe that emits abnormal green fluorescence upon binding withCu2+was also introduced, in which the mechanism is still unclear. Based on these considerations,we proposed the idea of developing series of rhodamine amide derivatives to investigate theirmechanism of metal ion induced abnormal fluorescence in this thesis.Chapter2is the experimental part. The equipments, materials, methods and details ofsynthesis and characterizations involved in the thesis were described.Chapter3investigated the mechanism of Cu2+-induced abnormal fluorescence emission ofrhodamine-ethylenediamine amide derivatives. Their absorption and fluorescent spectra werecomparatively measured in CH3CN in the presence of Cu2+and Hg2+, respectively. It was foundthat the addiction of Cu2+leads to the blue-shifted of the absorption and emission spectra ofrhodamine derivatives, but Hg2+does not induce such changes. It was also found that theblue-shift of spectra depends on substitution, where COOH group showed stronger tendency thanCOOR substitution, and alkyl chain length, substitution numbers as well as storage time havesignificant effect on spectra.Chapter4investigated the mechanism of Cu2+-induced abnormal fluorescence emission ofrhodamine B hydrazide derivatives. Their absorption and fluorescent spectra were comparativelymeasured in CH3CN in the presence of Cu2+and Hg2+, respectively. Similarly, the addiction ofCu2+leads to the blue-shift of both absorption and emission spectra, while the addiction Hg2+ showed the normal spectra. It was also found that the blue-shift of spectra strongly depends onCOOH and COOR substitution, single C-N and double C=N bond nature, and standing time.Chapter5investigated the potential applications of water-soluble rhodamine B hydrazidederivatives in fluorescence sensing and living cells imaging. Two water soluble derivativescontaining the C-N and C=N structure were selected as fluorescent probes to make a comparativestudy of the selectivity for metal ions, respectively. It was found that the probe with the C-Nstructure was highly selective for Cu2+detection, whereas the probe with the C=N structureshowed high selectivity on Hg2+. Both of these probes were successfully used for fluorescenceimaging in living cells.Chapter6is summary of thesis. Conclusions were drawn from the comparison study of seriesof rhodamine derivatives. It was concluded that all the designed derivatives emitted abnormalgreen fluorescence upon binding with Cu2+, while showed ordinary orange fluorescence with Hg2+in CH3CN. The blue-shifted fluorescence emission strongly depends on substitution nature andstanding time that may originate from Cu2+promoted aggregation of the rhodamine dye.