Synthesis And Photophysical Properties Of Naphthalimide Small Molecule Luminescent Materials

In order to achieve the national strategy of carbon peak and carbon neutrality,it is of great significance to study the deep processing of coal tar and prepare new chemical materials.1,8-naphthylimide derivatives prepared from coal tar acenaphthene are stable and refractory chemical materials.They are widely used in pigments and dyes.With further research,1,8-naphthalimide（NAI）derivatives were found to have excellent photoelectric properties.Naphthalimide materials with Donor and Acceptor systems have the ability to transmit electrons and holes at the same time,and can balance the injection of charge carriers well,which is an ideal structure for the construction of high-efficiency luminescent materials.In this thesis,a series of 1,8-naphthalimide blue light materials were synthesized using 1,8-naphthalimide as acceptor core.Phenyl（Ph）,thiophene（Th）and ethoxy（ETO）with weak power supply capacity were selected for substitution at 4 positions.In order to compare the influence of N-position linking groups on luminescence wavelength,thermal stability and solubility,different types of groups such as heterocyclic,aromatics and alkanes were selected.The results show that Th-NAI-Py has a maximum wavelength of 486 nm and a fluorescence quantum efficiency of 0.43in five kinds of blue materials.The introduction of rigid groups and heteroatoms can improve the thermal stability of compounds.Th-NAI-Py,Ph-NAI-Py and Ph-NAI-Me Ph all show good thermal stability,with 5%weight loss temperature（T_d）between 292℃-306℃and melting point（T_m）between 269℃-281℃.In order to improve fluorescence quantum efficiency and avoid fluorescence quenching caused by uneven doping of devices,a series of 1,8-naphthalimide red light materials were synthesized using 1,8-naphthalimide as accepter core.Using phenoxazine（PXZ）and phenothiazine（PTZ）as strong electron donor units,four kinds of PXZ-NAI-py,PXZ-NAI-Me Ph,PTZ-NAI-Py and PTZ-NAI-Me Ph with the characteristics of both convergence-induced luminescence（AIE）and thermal-activated delayed fluorescence（TADF）were synthesized.The study showed that their luminous wavelength is between 650-677 nm,belonging to the red luminous materials,and the fluorescence quantum efficiency of these four compounds is between 0.30 and 0.38.The energy level difference(ΔE_ST)of the four red light materials is between 0.06 e V and 0.10 e V,indicating that phenothiazine and phenooxazine have a high trimodal energy level,which can be replaced by naphthalimide to have TADF properties.The four compounds were tested with tetrahydrofuran/water mixed solution.The fluorescence intensity of the four compounds did not change significantly when the content of water component（f_w）was 0-60%,and the strong fluorescence emission could be detected when the f_wwas over 70%,which proved that the four compounds had obvious AIE properties.Phenoxazine and phenothiazine are rigid,and the 4compounds replaced by phenoxazine and phenothiazine have good thermal stability,with T_dbetween 295℃and 338℃.The glass transition temperature（T_g）of the four materials is between 137℃and 138℃,which can have good stability when making thin films,and is more conducive to application in electroluminescent devices.