Synthesis And Characteristics Of D-A Type Mechanofluorochromic Materials Based On Phenothiazine

Aggregation-Induced emission(AIE)materials have received widespread attention in recent years because of their excellent optical properties and variable fluorescence color.These materials have been widely used in biological probes,chemical sensor,dual function diagnostics,data storage and many other fields.In the last decades,researchers have been continuing to innovate and designed many organic sensitive fluorescent materials with significant AIE property.Among them,materials with mechanochromic properties are becoming more and more popular in recent years.Phenothiazine derivatives have become a popular research area for mechanochromic materials due to their excellent pressure-induced discoloration and flexible chemical structure.Besides,D-A type templates have a considerable interest in tunable emission.Therefore,based on the phenothiazine precursors,four novel organic fluorescence compounds(PB-M,PB-D,PB-I,PB-B)that were modified with different electron-drawing groups were designed and synthesized successfully.All the compounds behaved mechanical induced blue-shift properties.Its aggregation-induced luminescence effect,mechanochromic phenomenon and morphology of the compound was investigated,respectively.Then the relationship between the fluorescence phenomenon and the crystal structure of the compound was further discussed.Then the mechanical induced red-shifted precursor aldehyde(PBA)was also investigated to compare with our novel compounds.And through X-ray single crystal diffraction analysis,the mechanism of blue shift induced by external forces was also obtained.The UV-Vis absorption spectrum and fluorescence spectrum of compounds were examined and analyzed,then found that in addition to the obvious AIE properties of the compound PB-M,the other three compounds showed aggregation-induced fluorescence reduction.Precursor aldehyde(PBA)has a good effect of pressure-induced red-shifted phenomenon,but all novel compounds have mechanical induced blue-shifted obvious after ground by external forces.After thermal annealed,the ground samples of PB-D,PB-B,PB-I and PBA can return to its original state.However for PB-M after being annealed,its fluorescence even undergoes a certain more blue-shift.Powder wide-angle X-ray diffraction,SEM and X-ray single crystal diffraction were used to study the relationship between optical properties of the compound and its crystal structure,the change of the angle between C-C and C-N induced their mechanochromic blue-shifted behavior.