Synthesis And Study Of Naphthalene-1,8-dicarbonitrile Fluorescent Dichroic Dyes

Two novel series of fluorescent dichroic dyes have been synthesized by introducing4-hydroxypiperidine and phenylacetylene substituent group to4-site of the1,8-dicyanonaphthene. All dyes were characterized by nuclear magnetism and high resolution mass spectrum. Spectral quality of all the dichroic dyes, including fluorescence spectra, ultraviolet visible spectrum and polarization spectroscopy were tested. All the test data were summarized and explained.Bright blue-fluorescence was observed when the4-piperidyl-1,8-dicyanonaphthene fluorescent dichroic dyes were under the irradiation of uv light. The fluorescence quantum yield of the dyes is around0.67dissolved in dichloromethane and the maximum reaches up to0.772. A pure color display will be achieved if the dyes were used in "guest-host" liquid crystal display for the narrow half-peak width, about65nm. Assimilate order parameter, Sa reaches up to0.59and the maximum of fluorescence order parameter, Sf is0.591when dissolved in liquid crystal E7.Bright blue-fluorescence was also observed when the4-phenylacetylene-1,8-dicyanonaphthene fluorescent dichroic dyes were under the irradiation of uv light. But the fluorescence quantum yield of the dyes T2-T8is little than that of4-piperidyl-1,8-dicyanonaphthene fluorescent dichroic dyes and the maximum is only0.395. They all show a little Stokes shift, about27nm. Assimilate order parameter, SA is0.429-0.442and fluorescence order parameter, SF locates0.427-0.448when dissolved in liquid crystal E7.The maximum emission wavelength and absorption wavelength of T9is473nm,371nm respectively. It shows72nm half-peak width with the fluorescence quantum yield0.841when dissolved in dichloromethane.The fluorescence quantum yield of the dye is as high as0.88when dissolved in dioxane and show a weak susceptibility to the polarity of solvent. Assimilate order parameter and fluorescence order parameter is0.597,0.598respectively when dissolved in liquid crystal E7. T9shows a distinct nematic phase between125.7℃and151.4℃. The clearing point of E7increased about3℃when T9was dissolved in it at the mass concentration of0.5%. The birefringence of LC7014and XH9120increase when T5or T9is dissolved in it. So they can be used as one component to increase the birefringence of liquid crystal. The birefringence of T9worked out by extrapolation method is0.3217.