运用Gaussian 09W量子化学程序包, 对胭脂红分子进行基态和激发态几何结构构型优化, 计算得到激发态电子结构、 分子前线轨道和发射光谱等信息; 应用英国Edinburgh FLS920P 光谱仪, 实验测定胭脂红溶液的荧光光谱。 比较荧光发射光谱的计算值与实验值, 吻合较好, 说明优化所得构型基本合理。 进一步对比胭脂红分子基态和激发态结构, 分析荧光光谱产生的机理, 发现胭脂红分子激发态几乎呈平面结构, 为强荧光物质, 其荧光由139→137轨道的跃迁产生。

The molecule structures of Ponceau 4R in ground state and the excited state were optimized by employing the Gaussian 09W program package. In addition, the electronic structure and frontier orbital of the ground state, the emission wavelength of the excited state was also investigated. And then, the Edinburgh FLS920P fluorescence spectrometer was applied to the measurement of the fluorescence spectra of cochineal solution, and the emission spectra was obtained. The calculated emission wavelength had a good coincidence with the experiment data, which indicates that the optimized structures mentioned above are reasonable. The structures comparison between the ground state and the excited state was also performed to analyze the mechanism of fluorescence spectrum. It can be concluded that the molecule structure of excited state is nearly planar, so Ponceau 4R is thought to have strong fluorescent characteristics, the emission fluorescence is the result of transition from orbit 139 to orbit 137.