[Synthesis and spectrum of novel pyrazoline fluorescent compounds]

Pyrazoline derivatives have been used widely in dyeing industry as fluorescent whitening agents due to their excellent capability. According to Schellhammer theory of the relation between chemical structure and fluorescent quality, six new fluorescent compounds were designed and synthesized which contained the benzothiazole group in the 1-pyrazoline, the indole group in the 3-pyrazoline and the derivatives of phenyl in the 5-pyrazoline. The structure of target compounds was confirmed by IR, 1H NMR, MS and elementary analysis. The fluorescence spectra showed that these compounds had good fluorescence. They could absorb ultraviolet light at near 353 nm. The fluorescence maximum emission wavelengths were about 430-443 nm. It was a kind of promising fluorescence compounds. The largest fluorescence emission wavelength and the fluorescence intensity were related to the substituted group of the compounds. When the 6-Br group was introduced into benzothiazole, the fluorescence emission wavelength exhibited a blue shift, and the fluorescence intensity increased. Otherwise, the CH3 group was introduced into benzothiazole, the fluorescence emission wavelength red-shift occurred, and the intensity was lower. The fluorescence quantum yield of the compounds was little affected by the substituted group and polarity of the solvent The relative fluorescence intensity and fluorescence quantum yield were not directly related.