Characterization And Regulation Of Pure Organic Triplet Emitters Based On Carbazole And Aromatic Diones

Pure organic triplet-state luminenscent materials have great potential in applications such as security protection,organic light-emitting diodes?OLED?,photodynamic therapy,time monitoring,data recording,and chemo-and biosensors,therefore the characterization and regulation of organic triplet state emission properties is one of the current research focuses.Organic luminescent materials,which including carbonyl?C=O?groups and hetero atoms,can promote the intersystem crossing?ISC?processes and have considerable triplet emission properties under certain conditions.Their distinct structure and properties provide a molecular design strategy for organic triplet emission materials.Furthermore,the introduction of the multiple torsional degree of freedom structure can be utilized to change the molecular conformation and further regulate emission.Electron-rich and planarized molecule carbazole have high triplet energy,which can effectively tune the triplet emission and colors.Based on the above considerations,this thesis is dedicated to designing and preparing a series of pure organic triplet?DF and RTP?materials based on carbazole molecular structure,which we made use of physical or chemical methods to tune the emsssion color and the properities of DF/RTP.We try to do researches and clarify the relationship of structure and properties,providing the related design strategies.Details are as follows:?1?2CZBZL was successfully designed and synthesized based on raw materials carbazole and aromatic diones.When cultivated crystals by solvent evaporation,five polymorphs?crst-A,crst-B,crst-C,crst-D and crst-E?were obtained in DCM and THF,respectively.Besides prompt fluorescence,crst-B with relatively extended conformation exhibits DF property,where the others with more twisted conformations?crst-A,crst-C,crst-D and crst-E?demonstrate mainly RTP or DF and RTP.For the latter four polymorphis,their triplet emission are dramatically different in their delayed and emission color,which can be ascribed to their distinct vibration dissipations and the triplet sensitivity to vibration.These results provides new insighs in tuning the triplet emissions through conformation vibration and moreover molecular vibration.?2?A series of compounds CZBZL?CB?,CZBZL-Br?CBB?,PIDBZL-Br₁?PBB₁?and PIDBZL-Br₂?PBB₂?,which consist of carbazole,aromatic dione moity or/and Br atom,were prepared.The single crystals of four molecules,exihibit mechanochromic emissions,crst-CB and crst-CBB exhibit DF,while crst-PBB₁ shows delayed fluorescence?DF?/RTP dual emission,and crst-PBB₂ mainly demonstrates sole RTP emission.The differences of these four triplet emissions can be ascribed to the differences of conformations and the singlet-triplet energy gap(?E_st),owing to the introduction of Br atom,the connection location of carbazole and aromatic dione.To the best of our knowledge,it is relatively rare to demonstrate mechanochromic properties and to tune sole RTP and RTP/DF dual emissions by the change of conformation and the introduction of Br atom.Such distinct properties make these compounds potential materials in practical applications.