Study On Several Luminescent Materials With Triazine And Diphenyl Sulfone As Electronic Acceptors

Organic light-emitting diode(OLED),as the third generation of display technology,has become a research hotspot in recent years,and pure π-conjugated material with thermal activated delayed fluorescence(TADF)is an excellent OLED material.The structure(D-π-A)of electron donor(D)connected to electron acceptor(A)through π bridge is the most common design method for TADF materials.The selection of different donor and acceptor becomes an important affecting factor of optical properties.Based on the electron acceptors of triazine and diphenyl sulfone,in this paper,several D-π-A molecules were synthesized by connecting with different number of donors and donors modified by different substituents.The structureproperty relationship and luminescence mechanism of these organic luminescent molecules were discussed by density functional theory(DFT)calculation,steady state and transient fluorescence spectra.(1)Trimethyltriazine was used as the acceptor,acridine as donor and benzene ring as second electron donor,four D-π-A triazine derivatives were synthesized through alkalicatalyzed alcohol-aldehydes condensation reaction by connecting different number of electron donors,changing their molecular symmetry.The results show that the photophysical properties of the triazine derivatives do not change significantly with the increase of the number of donors,which can be attributed to the fact that the photophysical properties of the designed triazine derivatives are mainly determined by the intramolecular charge transfer of a pair of acridine donor D and the triazine acceptor A.(2)Diphenyl sulfone was used as the acceptor,acridine as donor,and bromine was introduced into diphenylsulfone group,a D-π-A structure was synthesized by nucleophilic substitution.The results show that solvation effect had been found,blue fluorescence emitted in toluene,green fluorescence in THF and yellow fluorescence in acetonitrile.Moreover,aggregation induction effect was also dicoverd,and the mixed system doped with more than80% water presents blue fluorescence that is similar to that of solid.When the doping ratio reaches 95%,the fluorescence intensity as good as the fluorescence intensity in pure THF.Therefore,the substance shows aggregation induced emission(AIE),and also has strong luminescence in organic solvents,which is different from the traditional aggregation induced luminescence materials.(3)Diphenylsulfone-acridine D-A-D molecule was modified with N-acetaniline,aniline and bromine,and the derivatives C,D and E were synthesized by Suzuki coupling reaction.The three molecules showed different photophysical properties.Compared with the ultra-low luminescence efficiency and short lifetime of monomers modified with aniline and bromine groups,the monomers modified with N-acetaniline showed higher luminescence efficiency and fluorescence lifetime close to microsecond level.The study shows that the molecule modified by N-acetanilide had potential TADF properties,and the molecule had hydrogen bonding sites that can construct supramolecular system,which is of great value for further study.