| Pyrazoline derivatives are important nitrogen containing 5-membered heterocyclic compounds and have received considerable attention in various fields such as pharmaceuticals, dyes, hole-transporting materials and fluorescent sensors. It is worthy of note that pyrazoline derivatives not only have been reported to show a wide range of biological activities, including antimicrobial, antinociceptive, anti-inflammatory, antiamoebic, anticonvulsant, antitubercular, anticancer and human monoamine oxidase (MAO) inhibitor, but also have displayed excellent blue emission, high quantum yield and hole-transporting efficiency. Therefore, pyrazoline derivatives have widely been used as whitening or brightening reagents for synthetic fibers, artificial leather and paper, fluorescent sensors for recognition of metal ions, hole-transport materials in electrophotography, organic light-emitting diodes, and novel fluorescent materials.In view of the importance of pyrazoline derivatives in pharmaceuticals and fluorescent materials fields, we focused our attention on the synthesis and optical properties research of pyrazoline derivatives and the exploration of fluorescent sensor based on pyrazoline moiety. The detailed work mainly contained two aspects as followed:1. Synthesis, structure characterization and optical properties research of pyrazoline derivatives.1.1 A series of pyrazoline derivatives have been synthesized by the reaction of phenyl chalcones containing different substituents and 3-chloro-6-hydrazinylpyridazine in the alkaline ethanol solution at reflux condition. The structures of compounds obtained were determined by 1H NMR, IR and HRMS spectra. Representatively, the spatial structure of compound 3d was determined by using X-ray diffraction analysis. Furthermore, Absorption and fluorescence spectra of these compounds in chloroform solution were investigated and the substituent effect on the absorption and emission spectra was discussed. At the same time, the absorption and emission spectra of compounds 3a,3b,3e and 3d in three solvents (THF, CHCl3 and CH3CN) with different polarity have been investigated and the solvent effect on the absorption and emission spectra was discussed.1.2 A series of pyrazoline derivatives have been synthesized by the reaction of ferrocenyl chalcone and 3-chloro-6-hydrazinylpyridazine in the alkaline n-propanol solution at reflux condition. The structures of compounds obtained were determined by 1H NMR, IR and HRMS spectra. Representatively, the spatial structure of compound 3c and 4c were determined by using X-ray diffraction analysis. Furthermore, absorption and fluorescence spectra of these compounds in chloroform solution were investigated and the substituent effect on the absorption and fluorescence spectra was discussed. At the same time, the absorption of compounds 3b and 3d in three solvents (THF, CHCl3 and CH3CN) with different polarity and fluorescence spectra of compounds 3b and 4b in three solvents (CHCl3, CH3CN and CH3OH) with different polarity were investigated and the solvent effect on absorption and fluorescence spectra was discussed.1.3 A series of bis-pyrazoline derivatives have been synthesized by the reaction of chalcones and (sulfonylbis(3,1-phenylene))bis(hydrazine) in the alkaline ethanol solution at reflux condition. The structures of compounds obtained were determined by 1H NMR, IR and HRMS spectra. Representatively, the spatial structure of compound 3b was determined by using X-ray diffraction analysis. Furthermore, absorption and fluorescence spectra of these compounds in dichloromethane solution were investigated and the substituent effect on the absorption and fluorescence spectra was discussed. At the same time, the absorption and fluorescence spectra of compounds 3c in six solvents (toluene, dichloromethane, ethyl acetate, CH3CN, ethanol and DMF) with different polarity were investigated and the solvent effect on absorption and fluorescence spectra was discussed.2. Synthesis, structure characterization and ion selectivity research of fluorescent sensors for Zn2+ based on pyrazoline.2.1 Pyrazoline derivative 5 modified by carboxyl group can be synthesized using 4-chlorophenol and 3-chloro-6-hydrazinylpyridazine as starting materials through five-step reaction. The structures of compounds obtained were determined by 1H NMR, IR and HRMS spectra. Furthermore, from the ion selectivity experiments, we found that compound 5 had a good selectivity for Zn2+ and anti-interference capacity against other ions in CH3CN/EtOH solution (90/10, v/v). The nonlinear curve fit according to the fluorescent titration data gave a 1:1 stoichiometric ratio between compound 5 and Zn2+ similar to Job's plot and the binding constant of the complex of 5 with Zn2+was calculated to be 2.5×106M-1. The fluorescence intensity at 480 nm of compound 5 in CH3CN/EtOH solution (90/10, v/v) increased almost 6-fold, when 1.0 equiv. Zn2+ was added.2.2 Pyrazoline derivative 4 can be synthesized using 4-chlorophenol and 2-aminopyridine as starting materials through multi-step reaction. The structure of compound obtained was determined by 1H NMR, IR and HRMS spectra. Furthermore, from the ion selectivity experiments, we found that compound 5 had a good selectivity for Zn2+ and anti-interference capacity against other ions in the HEPES buffer (20 mM HEPES, pH=7.2,50% (v/v) CH3CN). The nonlinear curve fit according to the Zn2+ titration data from absorption and fluorescence emission spectra all gave a 1:1 stoichiometric ratio between compound 4 and Zn2+ and the binding constant of the complex of 4 with Zn2+ was calculated to be 2.87×106M-1. Moreover, the limit of detection for determination of Zn2+ was calculated to be 1.2×10-7 M and the fluorescence quantum yield of compound 4 in the HEPES buffer (20 mM HEPES, pH= 7.2,50% (v/v) CH3CN) increased almost 3.5-fold, when 1.0 equiv. Zn2+ was added.In conclusion, three novel series of pyrazoline derivatives using pyrazoline moiety as core structure unit have been synthesized. Moreover, absorption and fluorescence spectra of these compounds in different solvents have been investigated and substituent effect as well as solvent effect on the wavelength and intensity of absorption and fluorescence spectra has been discussed. The above research can play a critical role in the further research or exploration of applicable fluorescence material based on pyrazoline. Furthermore, on the basis of fluorescence properties research of pyrazoline derivatives, we have also made some exploration of fluorescent sensors based on pyrazoline moiety and synthesized two Zn2+ sensors molecules. The ion selectivity, aiti-interference capacity against other ions and coordination number as well as banding constant of the complex of compounds and Zn2+ have been researched and discussed, which pointed out the direction for our further research or exploration of pyrazoline fluorescence sensors what can been applied in the water solution with highly sensitivity and selectivity. |
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