Design And Synthesis Of Carborane Functionalized Tetraphenylethylene Molecules And Research On Application Of Luminescent Properties

Carborane is an icosahedral organoboron molecule with a three-dimensional cage structure.It has excellent thermal and chemical stability,special electronic effects,spatial rigid structure,and C-C bond that can stretch and vibrate.Because of these unique properties,carborane has been applied in many fields,such as energy,catalysis,medicine and materials.In addition,the C-H and B-H of carborane can be functionalized to improve its properties and be more widely used in different fields.Aggregation-induced emission(AIE)is a special kind of luminescence phenomenon,which was first discovered by Professor Benzhong Tang’s group in 2001.Contrary to the well-known phenomenon of aggregation-caused quenching(ACQ),the AIE phenomenon refers to the fact that the compound does not emit light in a dilute solution,but it has strong fluorescence in the aggregate state or solid state.The most typical molecule is tetraphenylethylene.Tetraphenylethylene(TPE)has a rotatable and a larger conjugated system,and is a typical aggregation-induced luminescence small molecule.Because of its simple synthesis method,easy modification and unique photoelectric characteristics and biological activity,it has very important significance in light-emitting devices,biological imaging and OLED chemical sensors.In recent years,carborane molecules have been used to combine with TPE molecules,and a series of compounds with adjustable luminous color and high solid-state luminous efficiency has been designed and synthesized.Based on the previous research,this article has designed and synthesized novel carborane modified tetraphenylethylene luminescent materials,and studied their photophysical properties,which can be roughly divided into the following three contents.(1)First,a three-dimensional propeller-like structure where triphenylamine as the parent nucleus was designed and successfully synthesized,which is a substance with bright yellow fluorescence.In addition,the photophysical properties measured in experiment show that the compound has good aggregation-induced luminescence properties.After the introduction of the carborane cage,the solid-state fluorescence quantum yield has increased from 14% to62%,which is significantly improved.The emission wavelength of the target compound has a red shift of 150 nm compared to the precursor material.Besides,I also used density functional theory(DFT)and time-dependent density functional theory(TD-DFT)for quantum calculations,and tested the oxidation-reduction potential by cyclic voltammetry.(2)According to previous study,I have successfully synthesized new compounds by increasing the number of tetraphenylethylene and carborane,which extended the conjugated system.The experimental data show that the yield of solid-state luminescent quantum is significantly increased from 21.2% to 68.2% with the increasing of the bridging number of carborane and TPE,and the luminescent color changes from blue to orange yellow.In addition to completing the spectral characterization,we also apply density functional theory(DFT)and time-dependent density functional theory(TD-DFT)to calculate the optimized molecular structure and its electronic energy level diagram.(3)Finally,aiming at explaining the impact of cis-trans isomerism on TPE-Car molecules,we control the configuration from the raw materials,and successfully synthesized the cis-trans isomer organic molecules ofcarborane functionalized tetraphenylethylene.The experimental results showed that Z-TPE-2Car and E-TPE-2Car have a solid-state emission peak of 528 nm and 533 nm respectively,and exhibit a high solid-state fluorescence quantum yield of 0.99 and 0.90 respectively.We have given a corresponding explanation from crystal configuration and other aspects to reslove the difference in the propertyof isomer.