Synthesis, Structure Characterization And Propertiesresearch Of Pyrazoline Fluorescent Probes

Heavy metal ions are one kind of main pollutants in the environment, which have caused great threat to human living conditions. Heavy metal ions in the environment are difficult to degrade, which can be accumulated into the human body through the food chain, leading a serious threat to people’s health and life. Therefore, it is of great significance to establish a simple, fast, sensitive method to detect them as to the control of environmental pollution and the protection of human health.The advantages of molecular fluorescent probes for sensing can be summarized as follo wings:high sensitivity of detection, observation in situ, good selectivity, low cost, easy operation and so on. They have been widely used for cation, anion, amino acid, nucleic acid and protein detection. Pyrazoline derivatives have been obtained more and more attention as fluorophore for the metal ion probes because of their blue light emission with high fluorescence quantum yield, high fluorescence selectivity and excellent stability.Based on the advantages of the molecular fluorescence probe and pyrazoline compounds, we have designed and synthesized three fluorescent probes for metal cations in this thesis. The main contents are summarized as follow:1. Synthesis and study as copper ion fluorescent probe of [4-chloro-2-(5-phenyl-l-pyridin-2-yl-4,5-dihydro-lH-pyrazol-3-yl)-phenoxy]-acetic acid ethyl esterEthyl ester-pyrazoline derivative can be synthesized using4-chlorophenol and3-chloro-6-hydrazinylpyridazine as starting materials through multi-step reaction. The structures of compounds obtained were determined by1H NMR, IR and HRMS spectra. We have developed a highly sensitive and selective probe for Cu2+in aqueous solution. The color of solution changes from fluorescent blue to a non-fluorescent. Job’s plot confirmed the probe bind Cu2+in the1:1mode. When10μM of this probe were used in buffered EtOH/HEPES (20mM, pH=7.2,2:3, v/v) solution, the detection limit was0.4μM. Meanwhile, the experimental results demonstrate that this probe could be used to detect Cu2+in living cells. 2. Synthesis and study as copper ion fluorescent probe of2-(5-phenyl-3-thiophen-2-yl-4,5-dihydro-pyrazol-1-yl)-pyridineThiophene-pyrazoline derivative can be synthesized using2-acetyl thiophene and2-chloropyridine as starting materials through multi-step reaction. The structures of compounds obtained were determined by1H NMR, IR and HRMS spectra. The probe can detect Cu2+with high sensitivity and selectivity over other competitive metal ions in aqueous solution (EtOH:HEPES=1:1, v/v,0.02M, pH=7.2). The binding ratio of this probe and Cu2+was determined to be1:1based on the Job’s plot and the Cu2+-titration result. The binding constant (Ka) of complex was calculated to be6.80×104M-1and the detection limit of the probe for Cu2+was1.92×10-7M. Additionally, we have demonstrated that this probe could serve as a reversible fluorescent probe to detecet Cu2+in living cells.3. Synthesis and study as zinc ion fluorescent probe of3-(2-hydroxy-5-methyl-phenyl)-5-pyridin-3-y1-4,5-dihydro-pyrazole-1-carbothioic acid amidePyrazoline derivatives can be synthesized using p-methyl phenol and thiosemicarbazide as starting materials through multi-step reaction. The structures of compounds obtained were determined by1H NMR, IR and HRMS spectra. We have developed a highly sensitive and selective probe for Zn2+ions in aqueous media. Upon addition of Zn2+, the fluorescence maximum was remarkably enhanced up to80-fold. The addition of EDTA can quench the fluorescence of complex indicating this probe to be reversible for Zn2+. In addition, the probe was successfully applied to image Zn2+in SH-SY5Y neuron cells by excellent water solubility and higher sensing ability under the physiological pH. The fluorescent image was returned by adding an appropriate amount of EDTA. This probe can be employed to selectively monitor Zn2+in living neuron cells.