Study On The Aggregation-Induced Emission Properties Of Donor-Acceptor Compounds Based On Indole Derivative

Organic luminescent materials are characterized by easy structural modification,stable luminescence,simple synthesis and easy adjustment of luminescence,etc.In the past decades,many organic luminescent materials with excellent performance have been designed and widely used in bioimaging,chemical/biosensing,organic light-emitting diodes and other fields.However,the existence of π-π stacking between most organic molecules tends to lead to aggregation quenching phenomenon,which greatly limits the practical application of organic luminescent materials.Aggregation-induced emission is a phenomenon of enhanced luminescence in the aggregation state,mainly because the molecular motion is restricted in the aggregation state.Based on this,the development of organic luminescent materials with aggregation-induced emission properties could avoid the disadvantages of aggregation-caused quenching,which greatly promotes the development of organic luminescent molecules.Organic luminescent molecules could be divided into fluorescence,phosphorescence and thermally activated delayed fluorescence according to their luminous properties.In this paper,we designed and synthesized a series of organic luminescent molecules based on the twisted structure of the donor-acceptor structure using indole derivatives as the donor and diphenyl sulfone as the acceptor.By regulating the molecular structure,functional molecules such as fluorescence,dual emission of thermally activated delayed fluorescence-room temperature phosphorescence with aggregation-induced emission were obtained,which could be used in water content detection and cell imaging.The specific research contents and results are as follows:1.A series of fluorescence molecules with aggregation-induced emission properties based on donor-receptor structure were synthesized using diphenyl sulfone as electron acceptor and indole or indoline as the donor.By studying the photophysical properties,it was found that these molecules not only have obvious solvatochromism in solvents of different polarity,but also a unique "on-off-on" phenomenon with the emission wavelength first redshift then blueshift in a mixture solution of tetrahydrofuran and water due to the synergistic effect between the twist intramolecular charge transfer and aggregation-induced emission effect.On this basis,the three-dimensional working curve of the water content in tetrahydrofuran was established with the water content in tetrahydrofuran as the X-axis,the logarithmic values of intensity ratio and wavelength ratio as the Y-axis and Z-axis,respectively.This three-dimensional sensing method has higher sensitivity,greater detection range and accuracy than conventional methods.2.A single molecule with dual luminescent centers was designed and synthesized by using the donor-acceptor structure of diphenyl sulfone and indole derivatives as the first luminous unit,the hexathiobenzene as the second luminous unit,and the amide group as the bridging structure.By characterizing the photophysical properties of the molecule,it was found that the molecule has aggregation-induced emission properties and long-lived emission of thermally activated delayed fluorescence and room temperature phosphorescence in both dilute solution and the aggregated state.This work provides an effective strategy for the design of single molecules with dual long-lived emission in dual-phase.In addition,the molecule has the potential to be used as a time-resolved luminescent probe due to its advantages of dual longlived emission in dual-phase,which is expected to solve the problem in imaging such as selfbackground fluorescence interference and effectively improve the imaging quality.