Novel Spiro-Conjugated Arylethene Optoelectronic Functional Materials:Synthesis,Properties And Applications

With the booming development of flexible optoelectronic technologies and industries,organic optoelectronic functional materials have received considerable attention,and their research and development of application have laid an important foundation for the future development of optoelectronic devices.Arylethylenes is an important organic optoelectronic molecular moiety with rich photophysical and photochemical activities.On one hand,it shows rich classes of photo-promoted chemical reaction activities,such as isomerization,cyclization and dimerization reactions,which can build intelligent photochromic materials with high sensitivity and reversibility,and has great prospects for molecular machines,information storage and anti-counterfeiting.On the other hand,as a typical structural motif of aggregation-induced emission(AIE)materials,it can build advanced functional solid-state luminescent materials,which show great potential in flexible light-emitting devices,chemical sensing,bioimaging etc.The optical properties and functions of arylethylenes are essentially determined by their excited-state properties.However,its excited state process is complex,involving multiple physicochemical decay pathways and variables,and its photochemical activity is usually limited in the solid phase.Therefore,how to develop solid-state photo-functional materials through molecular design and aggregated state modulation are both emphasis and difficulty of research.In this thesis,by introducing the rigid orthogonal spiro skeleton into the diarylethylene through intramolecular oxidative dehydrocyclization reactions,a series of novel functional materials based on spiro-fused arylethylene molecules have been developed through chemical structural and aggregated state modulation,and most of which are AIE-active.We investigated the relationship of chemical structure-aggregated state packing modes-optoelectronic performance of organic materials and explored their applications in anti-counterfeiting,organic light-emitting diodes(OLEDs),organic solid-state lasers,etc.The main contents are as following:(1)By using radical-mediated intramolecular oxidative dehydrocyclization,we constructed a new class of AIE-active spiro-functionalized diphenylethenes.Experimental and theoretical studies reveal that the highly reversible ring-opening and closing photochemical processes of the diphenylethene moiety in such AIE materials are highly correlated with the efficiency of molecular luminescence.The role of spiro skeleton in modulating the excited-state radical cyclization decay was also discussed.It is shown that the restriction of the photocyclization leads to the activation of AIE properties in the solid state,which provides new ideas for the design of AIE materials.In addition,a class of novel deep-blue material with solid-state fluorescent quantum yield up to 99.8%and chromaticity close to the European Broadcasting Union standard blue was developed,which was successfully used as the blue light-emitting layer material in OLEDs.(2)In view of the serious deactivation of photochemical response in the solid state for arylethylene photoswithes,we developed a new class of bromine-substituted spiro-fused diphenylethylene derivatives with much improved solid-state performance.It enables photochromic and fluorescence-responsive conversion based on photocyclization in the crystalline state,a molecular process that produces an efficient,sensitive and stable reversible(>10,000 cycles)signal,and the response pattern of the photocyclized process is found to be modulated by different lighting conditions.The single crystal structure analysis shows the existence of through space and near-vertical configuration of halogen-?interaction owing to the spiro-ring spatial structure.These unique through-space interactions enhance the spatial freedom of motion of the arylethylene moiety and activate the highly reversible photocyclization process in the porous crystalline framework.This study also reveals the potential of through-space halogen-?interaction in the modulation of aggregated state properties for molecular materials.(3)A new class of organic solid-state laser materials has been developed based on the spiro-conjugated arylethylene molecular structure by introducing the arylamine groups.It is used as an optical gain medium for optically pumped organic crystal lasers,achieving blue(CIE_xy:(0.13,0.08))laser device with a minimum threshold of 0.50m J/cm² and a minimum half-width of 7 nm.The relationships between molecular structure,crystalline structure and laser performance of such materials were explored,by using single crystal structure analysis,transient spectroscopy,and ultrafast time-resolved fluorescence spectroscopy testing.This study may expand the design and modulation strategies of organic solid-state laser materials.(4)A new class of spiroanthracene-based diphenylethene photoresponsive molecules has been designed and synthesized by extending the synthetic method of radical-mediated intramolecular oxidative cyclization.These spiroanthracene derivatives exhibit AIE-active and molecular structure-dependent photochemical properties.Systematic experiments have revealed that the photochemical response of spiroanthracene compound originated from the reversible photocyclization of diphenylethylene.Particularly,anthrone modification of spiroanthracene derivatives could transfer the photochemically active center to congested bianthracene moiety and activate its photochemical oxidation process.Theoretical calculation studies showed that the conjugation and electron-withdrawing effects of anthrone moiety can modulate the molecular conformation and excited-state electronic structure of spiroanthracene derivatives,which in turn affect their photochemical processes.This provides new insights into the development of spiroanthracene-based photoresponsive materials.