Synthesis And Property Of Functional Molecules With Triphenylamine And 1,4-dihydropyrrolo [3,2-b] Pyrroles Moieties

Organic optoelectronic materials are always diverse with tunable molecular structures and molecular packing.The change of the molecular structures and the different packing modes in the aggregation state could have an effect on the photophysical properties of materials,which is different from the dispersed state.The current research topics mainly focus on the designing of molecular structures to regulate the properties of materials in aggregation state.In addition,the arrangement ways of molecules can also be changed upon external stimulus.For example,some compounds may respond to mechanical action or photo irradiation and change the packing modes.This design idea is widely used in the field of mechanoluminescence and photo-induced room-temperature phosphorescence.The traditional room-temperature phosphorescence phenomenon refers to the luminescence after the UV lamp is turned off,while compounds with photo-induced room-temperature phosphorescence property show an increase in the intensity or lifetime of phosphorescence after photo irradiation,which are non-emission after the UV lamp is turned off at first,but with strong phosphorescence emission after photo irradiation.Mechanoluminescence is luminescence induced by mechanical stimulus on a solid.At present,the related research on organic molecules is still limited,leading to the poor understanding of the internal mechanism.The study of the origin of the phenomenon can not only help to learn about the similarities and differences between the photoluminescence process and the mechanoluminescence process in depth,but also provide some ideas for designing more photo-induced room-temperature phosphorescent or mechanoluminescent materials,and realize the applications of more intelligent response materials.This thesis could be divided into two parts:In the first part,a triphenylamine derivative is synthesized,and the mechanoluminescence property and photo-induced room-temperature phosphorescence property are studied in detail.In the second part,a series of conjugated polymers with narrow band gap were synthesized.They adopted tetraarylpyrrole as the core to be a novel donor unit with some common acceptor units and may be used as the active layer of polymer photodetector.Chapter 1:A review of the relationship between the molecular packings in aggregated state and the emission properties of organic luminogens,and the applications of narrow-bandgap conjugated polymers in organic photodetectors is presented.In the first part,the effects of molecular packing on the room-temperature phosphorescence property,mechanoluminescence property and photo-responsive property of materials are introduced.In the second part,the development,working mechanism and related performance indexes of polymer photodetectors are introduced,and the applications of narrow bandgap conjugated polymers with different design ideas in photodetectors are emphasized.Finally,the effects of mechanical action and photo irradiation on the packing modes of crystals and their emission properties,as well as the influence of molecular designs on the properties of polymers,are described.The molecular design and main research contents of the thesis are put forward.Chapter 2:Based on triphenylamine,borate group was introduced to synthesize the compound TPA-B.Both photo-induced room-temperature phosphorescence property and mechanoluminescence property were achieved in this simple structure.Based on the luminescence upon two different external stimuli,including UV light and mechanical action,the photophysical properties of TPA-B before and after UV irradiation were examined carefully,and the emission behaviors in different solid state（crystal,microcrystalline,powder state）prepared by different mechanical action were also studied.In addition,the effects of temperature and oxygen on the photo-induced process or mechanoluminescence property were investigated.Finally,we combine the results of single crystal analyses,powder X-Ray diffraction and theoretical calculations to gain a deep understanding of the differences and connections between photoluminescence and mechanoluminescence.The research shows that the compressive molecular packing is more conducive to mechanoluminescence,and the increased intermolecular interactions after UV irradiation leads to the photo-induced room-temperature phosphorescence.A series of patterns have also been designed and realized through the combination of these two properties.Chapter 3:Based on tetraphenylpyrrole,novel donor units with different fluorine substituted positions or alkoxy chain lengths were designed.Ten polymers,which can be divided into three parts to study the relationship between the structures and properties,were prepared by Suzuki coupling of those donor units and common acceptor units like naphthalene diimide compounds and pyrrolopyrrolediones.In the first part,four polymers,PPN-OC₈C₁₂,PPN-OC₁₀C₁₄,FPPN-OC₈C₁₂,FPPN-OC₁₀C₁₄,were designed and synthesized by fine-tuning the length of alkoxy chains of the donor unit or introducing a fluorine atom.It helped to investigate the effect of fluorine substitution and the length of alkoxy chains on the properties of the polymer.We also changed the method to synthesize polymer FPPN-OC₁₀C₁₄-2 with a larger molecular weight to find the effect of different molecular weight.In the second part,the alkyl chains length of the acceptor unit pyrrolopyrrolediones was adjusted to synthesize two polymers,FPPD-C₂C₆ and FPPD-C₈C₁₂,to investigate the effect of different length of the alkyl chains of the acceptor unit.In the third part,the pyrrolopyrrolediones with the longer alkyl chains in the second part were used as acceptor units.Three polymers PPD,o-FPPD and m-FPPD were prepared based on different acceptor units without fluorine substitution,with ortho-fluoro substitution and meta-fluoro substitution.We explored the effect of different fluorine substitution positions on the electron and absorption properties of the polymer.The results indicate that the length of the alkyl chains at the donor or acceptor units mainly change the packing modes of polymers in aggregation state.And fluorine atoms can act as electron acceptor groups and hydrogen atoms acceptor groups to form hydrogen bonds with adjacent aromatic rings to increase its planarity and broaden the conjugate structure of the main chain at the same time,which has different dominant effects in different systems.