Construction And Properties Of Highly Efficient Organic Solid-State Luminescent Materials Based On Arylamide

Organic solid-state luminescent materials are widely used in many fields such as light-emitting devices,biological imaging,sensors,and solar cell,due to the advantages of adjustable structure,high optical stability,good biocompatibility,and low cytotoxicity.Benefit from variable organic molecular structures,abundant organic solid-state luminescent materials with different luminescent properties have been developed.However,most luminescent materials show low luminous efficiency.Therefore,in order to improve the practical application performance of solid-state luminescent materials,it is necessary to further explore the relationship between the structure and properties and develop universal strategies to improve the luminous efficiency of solid-state luminescent materials.In this paper,arylimide as target molecule,a series of high quantum yield solid-state luminescent materials were obtained by molecular structure design and intermolecular force adjustment.1.A series of aryl maleimide derivatives with donor-acceptor(D-A)structure were designed and synthesized by using maleimide as electron-withdrawing group and introducing different aryl groups as electron-donating groups at positions 2 and 3.By adjusting the push-pull electron effect of aryl group,the luminescence color can be adjusted in a wide range from blue to orange.All diphenylmaleimide derivatives show ultra-high luminous efficiency in both solution and crystal.The maximum quantum yield in solution is 88.2%,while in crystal condition,the quantum yield of all diphenylmaleimide derivatives is more than 80%,and the highest is close to 100%.In addition,tert-butoxyamide substituted diphenylmaleimide displays the characteristics of homogeneous polycrystalline.The luminescence color of different crystals ranges from yellow to red.From the crystal structure of diphenylmaleimides,it is found that the "side by side" stacking in crystal can induce carbonyl to form strong intermolecular noncovalent bond,leading to the tight molecular structure and efficient solid-state luminescence.2.In order to further explore the effect of N-aryl on the luminescence properties of maleimide derivatives,triaryl maleimide derivatives with donor-acceptor-donor(D-AD)structure were designed.By adjusting the push-pull electron effect of N-aryl group,the intramolecular charge transfer(ICT)from N-aryl group to maleimide can be adjusted,leading to the high-efficiency fluorescence emission of triaryl maleimide derivatives in solution and solid state.The maximum quantum yield of triaryl maleimide derivatives in solid state up to 92.5%.Among them,triaryl maleimide derivatives with unsubstituted on N-phenyl show obvious aggregation induced emission enhancement(AIEE)characteristics.Comparative experiments and theoretical calculations show that the more planar conformation in the solution state induces a strong ICT effect and leads to fluorescence quenching.In addition,by adjusting the electron effect of maleimide 2,3-aryl group,it is found that triaryl maleimide with unsubstituted or electron-withdrawing group substituted at 2,3-aryl show weak/no fluorescence.While the triaryl maleimide with electron-donating group substituted at 2,3-aryl display strong solid-state fluorescence emission.The possible reason is that the electron-withdrawing substituents leads to the reduction of energy level of maleimide,resulting in the electron transfer from N-aryl to maleimide and fluorescence quenching.Based on the principle of dual ICT regulation,a triphenylmaleimide molecule with orange light emission was designed,with the solidstate quantum yield up to 97.9%.Its single-component white light-emitting diode(WLED)shows high photoelectric efficiency.3.Due to the presence of heteroatoms(n electrons)and carbonyl groups(π electrons)in the molecular structure,imide and anhydride can be prone to electron interaction and form spatial conjugated in the aggregated state.Therefore,two space conjugated materials,thiophene imide and thiophene anhydride,were designed and synthesized.In the crystal state,both spatially conjugated molecules exhibit efficient white light emission with quantum yields up to 26.8%.The steady-state and delayed emission spectra show the characteristics of excitation wavelength dependent.In addition,the yellow afterglow can be observed after the UV lamp is turned off.Theoretical calculation and single crystal structure show that different aggregation modes produce different spatial conjugate luminescence,which is combined into white light emission.Based on the stable luminescence performance of thiophenimide,the dual-mode WLED of ultraviolet chip and blue chip were prepared,which showed excellent electroluminescence performance.The color rendering index(CRI)of WLED driven by blue chip was 85 with International Commission on illumination(CIE)(0.33,0.35),which was close to the CIE of pure white light(0.33,0.33).4.In order to improve the luminescent properties of imide room temperature phosphorescent materials,arylimide was introduced into inorganic boric acid matrix by solid-state synthesis.With the benefit of hydrogen bonding between host and guest molecules,a series of composites with excellent phosphorescent properties were obtained.Among them,the phosphorescent quantum yield of benzoimide composites is up to 84.2% with the average lifetime of 894 ms,which is higher than that of arylimide phosphorescent materials reported at present.Based on the strong hydrogen bond between host and guest,a larger conjugated system was introduced to realize the wide range of phosphorescent color of the complexes from blue to orange.The strategy has good universality,the complexes of dicarboxylic acid with strong hydrogen bond also show efficient phosphorescent emission with maximum phosphorescent quantum yield and the average lifetime up to 73.6% and 1.73 s,respectively.