Aggregation-induced Emission (AIE)-active Benzothiadiazole Or Benzo[d]imidazole Derivatives: Preparation And Investigation On Their Mechanofluorochromic Properties

Organic compounds with luminescence properties have important application prospects in sensing,photoelectric applications,information storage and other fields,which have attracted extensive attention of researchers.However,in the clustered state,most traditional fluorescent organic materials will be partially or even completely quenched,which is called aggregation-induced quenching effect（ACQ）.In practical applications,most fluorescent materials exist in the form of aggregates such as films or solids.In 2001,aggregation-induced luminescence（AIE）was discovered,indicating that compounds with AIE effect emit very little or no luminescence in solution,but can emit strong fluorescence in the aggregation state.Therefore,AIE effect is very important for the practical application of fluorescent materials.Subsequently,in 2002,Park and his colleagues developed a aggregation-induced emission enhancement（AIEE）effect associated with planarization and J-aggregation.The luminogen with AIE or AIEE properties can be induced to exhibit bright luminescence through the formation of aggregates.Since the discovery of AIE/AIEE phenomenon,a large number of high-aggregation emitting molecules have been obtained,and a series of potential applications of AIE/AIEE active luminogen have attracted wide attention.In addition,strong solid state luminescent materials with mechanofluorochromism properties can be applied in the fields of sensing,information storage and recording,so they are promising stimuli-responsive materials,and relevant research is meaningful.Obviously,the development of luminescent compounds with mechanofluorochromism and AIE/AIEE characteristics is a meaningful and challenging work.Based on the above research background,a series of novel fluorescence molecules with aggregation induced luminescence and mechanofluorochromism properties were designed and synthesized in this thesis.The main research contents are as follows:1.Three fluorescent molecules I-1,I-2 and I-3 based on benzothiadiazole unit were designed and synthesized.The structure of the molecule was characterized by¹H NMR and¹³C NMR.The aggregation-induced emission and mechanofluorochromism properties of molecules were studied by UV-vis absorption spectra and fluorescence emission spectra.The results showed that the fluorescence molecules I-1 and I-2 had obvious aggregation-induced fluorescence enhancement and distributed bright yellow and yellow-green fluorescence in the aggregation state.In solid state,the derivatives I-1 and I-3 showed reversible mechanofluorochromism characteristics by the crystalline-amorphous phase transition.2.Three distorted fluorescence molecules II-1,II-2 and II-3 of D-A-π-D benzothiadiazole derivatives were designed and synthesized.The structure of the molecule was characterized by¹H NMR and¹³C NMR.The aggregation-induced emission and mechanofluorochromism properties of molecules were studied by UV-vis absorption spectra and fluorescence emission spectra.It was shown that all of these fluorescent molecules are AIE active and emit bright orange light in the concentrated state.In solid state,compound II-1 exhibits reversible mechanofluorochromism properties by the crystalline-amorphous phase transition.The original yellow fluorescence of compounds II-2 and II-3 was converted to yellow-green fluorescence after slight grinding,and both compounds showed orange fluorescence after regrinding.Therefore,compounds II-2 and II-3 exhibit interesting three-color mechanofluorochromism properties.3.Four fluorescent molecules III-1,III-2,III-3 and III-4 based on benzimidazole units were designed and synthesized.The structure of the molecule was characterized by¹H NMR and¹³C NMR.The aggregation-induced emission and mechanofluorochromism properties of molecules were studied by UV-vis absorption spectra and fluorescence emission spectra.The results showed that the four compounds had obvious aggregation-induced fluorescence enhancement and distributed bright yellow and green fluorescence in the aggregation state.In solid state,compound III-4 exhibits reversible mechanofluorochromism propertiesby the crystalline-amorphous phase transition.