Computational Investigations On Fluorescence Spectra And Excited State Properties Of Styryl Triphenylamine Series Compounds

Upon the ground state molecule of the triphenylamine organic photoelectric dye is excited by light,the electrons of the ground state are transitioned to the excited state,which changes the geometry,molecular orbit,charge distribution and other properties of the molecule.Due to the phenomenon of charge transfer and charge separation,the photophysical process of molecules becomes more complicated.Based on the related experimental results,this thesis uses density functional theory and time-dependent density functional theory to simulate the excited state structures and fluorescence spectra of the triphenylamine series compounds.The calculation parameters suitable for studying the excited state calculation of molecules are selected.Furthermore,the geometrical structure,electronic structure,electronic transition and fluorescence spectra of the excited state of the molecule are calculated and analyzed to guide the design and synthesis of triphenylamine organic photoelectric molecules.In the first part,B3 LYP,M06-2X,CAM-B3 LYP and ?B97XD functionals were used to calculate the styryl triphenylamine series compounds modified by different substituents.The comparison between the vertical emission energy and the fluorescence emission energy in the experiment shows that the B3 LYP functional is in good agreement with the experimental value in the change trend.Furthermore,B3 LYP functional was used to simulate their excited state structures,electronic structures and fluorescence spectra.The results show that as the electron donating ability of the para substituent decreases and the electron withdrawing ability increases,the overlap integral of HOMO and LUMO decreases.In particular,the bond length between the triphenylamine group and the styrene group in the molecules with strong electronwithdrawing groups increased significantly,showing the tendency of separation,which reasonably explained the charge separation phenomenon in the relevant experimental results.In the second part,B3 LYP,M06-2X,CAM-B3 LYP and ?B97XD functionals were used to calculate the charge-separated triphenylamine-s-triazine series compounds.By comparing with experimental values,comprehensive structural optimization,fluorescence emission energy and oscillator strength calculation results,the ?B97XD functional is suitable for the simulation of excited state-related properties of triphenylamine-s-triazine series compounds.The calculation and analysis results show that the vinyl part of the styrene group in the first excited state structure exhibits a stronger conjugation effect than the ground state structure.The overlap integral between the unoccupied orbit and the occupied orbit gradually decreases with the enhancement of the electron donating ability of the triphenylamine(carbazole,indoline)part.The electron transfer between the fragments shows that during the fluorescence emission,electron transfer from the part of the triazine ring to the part of triphenylamine(carbazole,indoline)occurs.In the third part,The charge separation type triphenylamine-pyrimidine series dyes were calculated with the same calculation parameters as triphenylamine-s-triazine series compounds.The geometry,electronic structure and vertical emission energy of its excited state were simulated and analyzed in the absence of solvent,toluene solvent and methylene chloride solvent.The results show that as the polarity of the solvent increases,the conjugation of the styryl moiety increases,and the separation tendency of the pyrimidine ring from the styryl moiety increases.In the fluorescence emission of triphenylamine-pyrimidine series dyes,the LUMO?HOMO and LUMO?HOMO-1electronic transitions mainly occur when the solvent is not considered,and the LUMO?HOMO and LUMO+1?HOMO electronic transitions mainly occur when the solvent is considered.