Synthesis And Performance Test Of Florane Functional Dyes

It has been considered that florane dyes are the most promising dyes as the third generation of heat- and pressure-sensitive dyes.Different substituents can be easily introduced to the mother ring of florane,by which the heat- and pressure-sensitive dyes with different colors and more excellent performance can be obtained.Having important physiological activity,aromaticity and strong conjugative effect,1,3,4-thiadiazole and 1,3,4-oxadiazole derivatives have highly fluorescent properties.With introducing the heterocycle 1,3,4-thiadiazole and 1,3,4-oxadiazole,4 different floranes are synthesized.Firstly the important intermediate KETO acid was synthesized,and the reaction mechanism has been studied.The reaction mechanism has been confirmed:3-diethylaminophenol and phthlic anhydride were esterified to form phenolate intermediate,which was then rearranged to form KETO acid.Secondly,the synthesis of 1,3,4-thiadiazole and 1,3,4-oxadiazole derivatives was studied.By passing through a series of processes: hydrazination in hydrazine hydrate,acylation from acyl chloride and cyclization respectively in phosphorus pentasulfide and phosphorus oxychloride with the raw material p-methoxybenzoic acid, 1,3,4-thiadiazole and 1,3,4-oxadiazole derivatives can be synthesized.Not only can the reaction steps be reduced,but also the amount of hydrazine hydrate has been significantly reduced by hydrazinating benzoic acid directly.Based on experiments,the optimum process parameters were discussed and determined.The effect factors of molar ratio of raw materials and reaction time were optimized as follows:n(4-methoxyben-zoic acid):n(hydrazine hydrate) is 1:4,the reaction time is 9 h,the yield is 66.76%.Meanwhile,the synthesis of floranes was studied.The corresponding florane can be obtained by treating KETO acid separately with p-chlorophenol,β-naphthol,2-methyl-5-(4-methoxylphenyl)-1,3,4-thiadiazole,2-phenyl-5-(4-methoxylphenyl)-1,3,4-thiadiazole,2-methyl-5-(4-methoxylphenyl)-1,3,4-oxadiazole and 2-phenyl-5-(4-methoxylphen-yl) -1,3,4-oxadiazole in concentrated sulfuric acid.Simplifying post-processing operation can significantly reduce the waste of materials and improve the yield.The influence factors of florane yield were optimized as follows:the molar ratio of raw materials is 1:1;the reaction time is 24h;the sulfuric acid concentration is 90%;the reaction temperature is 75℃;the yield is 65%.Then performance of heat-sensitive was tested.The influence factors of color performance—color development reagent and solvent was studied.Take 3-diethylamino-7-chloroflorane as an example.It has been concluded that the heat-sensitive dyes with the quality of the shares composition ratio of 1:2:30 of dyes,color development reagent and solvent have the best color effect.Six fluoanes have strong color intensity and good color performance and heat-sensitive effect.Finally,the fluorescent spectrum performances were studied.The relations between fluorescent spectrum performances and chemical structures and solvents were studied.Based on experiments,the ultraviolet absorbance wavelength of florane was influenced by electronegativity,while the absorptivity was influenced by conjugacy.As the solvent polarity grew,the emission spectrum red shifted and the quantum efficiency increased firstly and then reduced.