Synthesis And Properties Investigation Of Tetraphenylethene-based Imide Compounds

Materials are the important material basis for human survival and development,and the development of materials directly promotes the progress of society.Traditional luminescent materials can efficiently emit light in dilute solution,however,the luminous efficiency in an aggregated state is significantly reduced or even not emitted.This is called aggregation-caused quenching(ACQ).In practical applications,luminescent materials usually need to be made into solid or thin films,so it is of great significance to research and explore efficient solid-state luminescent organic materials.The discovery of aggregation-induced emission(AIE)provides new opportunies for the development of solid-state luminescent materials.Tetraphenylethene(TPE),as a typical aggregation-induced emission compound,has the advantages of simple molecular structure and simple synthesis.Using TPE as a precursor can effectively construct a variety of solid luminescent materials.In this paper,a series of solid-state luminescent materials were synthesized through the modification of tetraphenylethene by imide groups,and the relationship between structure and properties was studied.The main research contents are as follows:1.Two compounds,TPE-0 and TPEP-0,were synthesized through the introduction of succinimide on tetraphenylethene.Both compounds have high fluorescence quantum yields in the solid powder state,which are 66.04% and 45.50%,respectively.The introduction of succinimide changes the symmetry of tetraphenylethene itself,and the introduction of heteroatoms increases the intermolecular weak interactions,such as C-H···O?C-H···N,these weak interactions to be easily destroyed under external forces.The introduction of succinimide,tetraphenylethene,which has not piezochromic phenomena originally,has successfully obtained reversible piezochromic properties.After grinding,the compound TPEP-0 has a red-shifted fluorescence of 43 nm and a very high contrast before and after grinding.By analyzing PXRD and DSC test results,we believe that the reason for piezochromic properties of the compounds is caused by the change from the crystalline state to the amorphous state.2.Two intermediate compounds TPE-MI and TPEP-MI were synthesized by introducing maleimide group on tetraphenylethene.Fluorescence quenching occurs due to the photo-induced electron transfer(PET)process between tetrastyrene and maleimide.We used the Diels-Alder reaction to block the PET process and obtained four compounds TPE-1,TPE-2,TPEP-1,and TPEP-2.The four compounds have a high fluorescence quantum yield in the solid powder state,of which the TPEP-2 reaches 74.69%.The four compounds also have reversible piezochromic properties.Among them,compound TPE-2 has a red-shifted fluorescence of 40 nm after grinding and a very high contrast before and after grinding.the reason for piezochromic properties of the compounds is also caused by the change from the crystalline state to the amorphous state.3.TPE-3 was synthesized using the Diels-Alder reaction.TPE-3B with Dark blue fluorescence and TPE-3G with yellow-green fluorescence were obtained respectively by recrystallization and removing solvent through rotary evaporation,two different aggregation states have high fluorescence quantum yields.Interestingly,after grinding,the fluorescence of TPE-3B was red shifted and the fluorescence of TPE-3G was blue shifted.The example of fluorescence red-shift and blue-shift of the same compound based on tetraphenylethene derivative in different aggregate states after grinding has not been reported in the literature,providing an ideal model compound for studying the mechanism of piezochromism.Two kinds of single crystal structures were successfully obtained by slowly evaporating the solvent.Crystal structure showed that TPE-3B is a kind of J-aggregates,while TPE-3G is a kind of H-aggregates.