Aggregation-induced Emission And Mechanochromism In Tetraacetylene Derivatives

Normally,the luminescent molecules have a strong fluorescence in the dilute solution,but in the concentrated solution or in the aggregated state,its luminescence ability becomes weak or even completely disappeared,this phenomenon is called aggregation-caused quenching(ACQ).On the contrary,aggregation-induced emission(AIE)is another photophysical phenomenon associated with chromophore aggregation.The luminescent molecules have a weak fluorescence in the dilute solution while it shows strong fluorescence in the concentrated solution or in the aggregated state.Some compounds with AIE properties also exhibit reversible mechanochromic behavior.In this thesis,five different compounds with benzimidazole/oxazole/thiazole and bipyridyl units were synthesized via Pd-catalyzed Suzuki cross-coupling reaction with tetraphenylethene derivatives.At the same time,their AIE and mechanochromic properties were investigated.A preliminary explanation of their properties was made by X-ray single crystal diffraction.The main research contents are as follows:1.Synthesis of polyarylene derivatives with benzimidazole/oxazole/thiazole and bipyridyl structural units:Catalyzed by tetrakis(triphenylphosphine)palladium,the Suzuki cross-coupling reaction occurs between bromo-substituted imidazole/oxazole/thiazole/bipyridyl derivatives and the polyarylene vinyl alcohol ester(Scheme 1).2.Studies on the aggregation-induced emission(AIE)and mechanochromic properties of Compounds 14-19:Compounds 14-18 had very weak fluorescence in tetrahydrofuran solution,but AIE phenomenon occurred in tetrahydrofuran/water mixed solvent,which showed strong fluorescence in the solid state for 14-18.However,compound 19 did not exhibit AIE properties.Meanwhile,compound 14 exhibited a mechanochromism property,and the fluorescence color of compound 14 is changed under external force.Interestingly,the fluorescence color and the fluorescence emission spectrum of compound 14 can be recovered to the original state by fuming with CH2Cl2,indicating that the mechanochromic process is reversible.