Study On The Stimulus Response Of BF₃ To 7-Diethylamino Coumarin Derivatives

Stimulus-responsive fluorescent materials can sense subtle changes in the external environment.External environmental stimuli such as mechanical force,light,heat,acid and alkali,and voltage will cause a series of dynamic and reversible fluorescence intensity and color changes of these materials.Therefore,stimulus-responsive fluorescent materials are used in biological detection,chemical analysis,information storage and photoelectric lighting field.The aggregation induction effect of traditional organic fluorescent materials is caused by the strong intermolecular?-?interaction,which reduces the fluorescence intensity of solid materials.Therefore,the practical application of solid materials is limited.It is very important to design new stimulus-responsive fluorescent materials with strong fluorescent emission in the solid state.Coumarin has excellent fluorescence properties in the visible light range because of its rigid planar conjugated structure.Therefore,coumarin is used as the basic structure to connect various groups such as hydroxyl,isopentenyl,alkoxy,carbonyl and other substituents to obtain a variety of coumarin derivatives with superior performance.In this paper,based on7-diethylaminocoumarin,two coumarin derivatives with strong fluorescence emission were synthesized by connecting different substituents at the 3-position.The contents of rewritable paper and LED based on TAC1 and TAC2 are as follows:(1)Two coumarin-based fluorescent materials(TAC1 and TAC2)were synthesized by connecting thiophene substituents and p-toluene to the 3-position of 7-diethylaminocoumarin.First,the photophysical properties of the two compounds in different polar solvents are studied.As the solvent polarity increases,the fluorescence emission peaks of the two compounds occur blue-shifted,which indicates that the molecules have an intramolecular charge transfer(ICT)effect;In the solution,after TAC1 interacts with BF₃,the fluorescence color of the solution changes from green to bright blue,the maximum absorption peak is blue-shifted from the original 425 nm to 363 nm,and the fluorescence emission peak is blue-shifted from 485 nm to 431 nm.After adding TEA to the solution,the fluorescence color of the system quickly returned to green,the maximum absorption peak and fluorescence emission peak were also red-shifted to their original positions;the similar phenomenon was observed in TAC2 solution.After adding BF₃,the fluorescence color of the solution changes from bright blue to dark blue,the position of the maximum absorption peak of TAC2 is blue shifted from 398 nm to 325 nm,and the fluorescence emission peak is blue shifted from 464nm to 408 nm,after adding TEA to the solution,the fluorescent color of the solution returned to bright blue.When TAC1 interacted with BF₃,the fluorescence changed from green to bright blue,but after adding triethylamine,the fluorescence of the system quickly returned to yellow-green;Based on the above experiment,a recyclable rewritable paper was designed and its conditions were optimized.When TAC1 concentration was 1×10^-6M,no traces on the rewritable paper can be observed by naked eyes.The process of writing with BF₃and erasing with triethylamine can only be seen under ultraviolet light.As a result,a novel encryption function was realized on recyclable rewritable paper.(2)The luminescence performance of TAC1 and TAC2 in the solid state was studied,and it was found that both compounds have excellent solid-state luminescence performance;Based on TAC1 and TAC2,a primary rewritable system was designed.The TAC1 test paper with high sensitivity and short action time was selected for encryption test.When TAC1concentration was 1×10^-6M,no traces on the rewritable paper can be observed by naked eyes.The process of writing with BF₃and erasing with triethylamine can only be seen under ultraviolet light.As a result,a novel encryption function was realized on recyclable rewritable paper.Two high-efficiency LED devices are designed with TAC1 and TAC2.When working voltage is 4.0V,their color coordinates are(0.257,0.533)and(0.3649,0.5796).The TAC2LED has higher luminous intensity than TAC1 LED.Under the working voltage of 4.0 V,the maximum luminous intensity of TAC2 reaches 132300 cd/m²,this phenomenon shows that TAC2 has high light conversion efficiency.