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在B3LYP/6-311G(d,p)水平下优化了3种香豆素衍生物的几何构型,并通过振动分析验证了其构型稳定性。在此基础上进行垂直激发的TD-DFT(含时密度泛涵)计算,得到化合物的吸收光谱数据,然后放松激发态结构,进行TD-DFT几何优化得到化合物的荧光发射光谱。研究结果表明:3种化合物结构共平面性较好,均为较大共轭π键体系,均具有荧光特征;由于重原子效应导致化合物L-3的荧光强度相对减弱,但荧光波长变长,谱线红移;相对于吸收光谱,发射光谱均存在stokes位移,且发射光谱与吸收光谱第一吸收带之间呈镜像关系。最后,吸收光谱与发射光谱理论计算值与实验数据基本吻合表明该理论计算方法比较可靠。
The geometries of the three coumarin derivatives were optimized at the B3LYP / 6-311G (d, p) level and their configuration stability was verified by vibrational analysis. On this basis, TD-DFT (including time-dependent density functional) of vertical excitation was calculated to obtain the absorption spectrum data of the compound, and then the excited state structure was relaxed and the fluorescence emission spectrum of the compound was obtained by TD-DFT geometry optimization. The results show that the three compounds have a good coplanarity, which are all larger conjugated π-bond systems and have fluorescence characteristics. Due to the heavy atom effect, the fluorescence intensity of compound L-3 is relatively weak, but the fluorescence wavelength is longer, The redshift of the spectrum; relative to the absorption spectrum, there are stokes shifts in the emission spectrum, and the emission spectrum and the first absorption band of the absorption spectrum was a mirror image. Finally, the calculated values of absorption spectrum and emission spectrum agree well with the experimental data, which shows that the theoretical calculation method is more reliable.