Synthesis and spectrum characteristic of four new organic fluorescent dyes of pyrazoline compounds

Four novel fluorescence dyes of the pyrazoline were synthesized, which were 1,3-diphenyl-5-(4-chlorophenyl)-2-pyrazoline (DCP), 1,5-diphenyl-3-biphenyl-2-pyrazoline (DBP), 1,5-diphenyl-3-(N-ethylcarbazole-3-yl)-2-pyrazole (DEP), and 1-phenyl-3-(N-ethylcarbazole-3-vinyl)-5-(N-ethylcarbazole-6-yl)-2-pyrazole (PEEP). The characteristic of the synthesis methods used is that the carbazole radical is linked with pyrazoline molecule. The products were characterized by IR spectra, 1H NMR, elemental analysis and fluorescence spectra. The fluorescence emission spectra of the compounds were red-shifted evidently from DEP to PEEP in CHCl3. The solvent effect on the fluorescence characteristics of the four compounds indicates that the emission wavelength was red-shifted with the increase of solvent polarity. The concentration effect on fluorescence intensities of the four compounds showed that the fluorescence intensities increased initially and then decreased with the concentration increasing. The fluorescence quantum yields of the four compounds were obtained and the fluorescence quantum yield of PEEP was the largest.