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应用英国Edinburgh FLS920P光谱仪对苋菜红的吸收光谱和荧光光谱进行了实验检测.同时,分别采用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)对苋菜红分子的基态和激发态构型进行优化,经振动分析合理后,比较这两种能态下分子结构的差异,并对其前线分子轨道和发光机制进行了分析.在此基础上,选用6种泛函并结合溶剂化模型(PCM)在6-311++G(d,p)水平上分别计算苋菜红的吸收光谱和荧光光谱.计算结果表明:苋菜红含有分子内氢键,基态结构非平面,两个萘环所在平面有一定的夹角,激发态时两个萘环共平面;CAM-B3LYP泛函得到光谱的理论值与实验结果基本吻合;421 nm处的荧光峰值波长对应的轨道跃迁为LUMO→HOMO-1.
The absorbance spectra and fluorescence spectra of amaranth were detected by using FLS920P spectrometer in Edinburgh, UK. At the same time, the ground state and excitation of amaranth molecular were investigated by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) State configuration optimization, the vibration analysis is reasonable, the difference between the two molecular states under the two energy states, and its front-line molecular orbital and luminescence mechanism were analyzed.On this basis, the selection of six functional and solvent (PCM) was used to calculate the absorption and fluorescence spectra of amaranth at the level of 6-311 ++ G (d, p) .The results showed that the amaranth contained intramolecular hydrogen bonds, non-planar ground state structure and two naphthalene The two rings are coplanar in the excited state. The theoretical values obtained by the CAM-B3LYP functional theory agree well with the experimental results. The orbital transition corresponding to the fluorescence peak wavelength at 421 nm is LUMO → HOMO -1.