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采用量子化学密度泛函理论(DFT)在B3LYP/6-31G*水平上对丹参酮Ⅰ、丹参酮ⅡA、隐丹参酮3个典型的丹参酮类化合物分子几何构型进行优化,分析分子前线轨道能级及分布特征。用含时密度泛函理论(TD-DFT)在相同水平对上述化合物分子进行电子吸收光谱研究。并且以乙醇为溶剂,计算其对分子结构和光谱性质的影响。计算结果表明:丹参酮Ⅰ分子骨架发生共轭形成大π键,为刚性的平面分子结构;丹参酮Ⅰ、丹参酮ⅡA、隐丹参酮分子共轭体系依次缩小。分子HOMO-LUMO能隙随着分子共轭体系的减少而增大。3个分子的λ_(max)均主要来源于电子的π→π*跃迁。乙醇对上述化合物分子结构和光谱性质有一定影响,吸收光谱均发生红移。同时还发现,乙醇改变了丹参酮Ⅰ的λ_(max)主要电子跃迁来源轨道。丹参酮Ⅰ在气相条件下λ_(max)主要来源于分子中的HOMO→LUMO+2的π→π*跃迁;而在乙醇中λ_(max)主要来源于HOMO-5→LUMO的π→π*跃迁,该跃迁存在明显的分子内电子转移现象。
Three typical tanshinone geometries of tanshinone Ⅰ, tanshinone ⅡA and cryptotanshinone were optimized at B3LYP / 6-31G * level by using quantum chemical density functional theory (DFT), and the molecular frontier orbital energy levels and distributions were analyzed feature. The above compound molecules were subjected to electron absorption spectroscopy at the same level using time-dependent density functional theory (TD-DFT). And ethanol as a solvent, calculate its molecular structure and spectral properties. The calculated results show that the tanshinone Ⅰ molecular skeleton is conjugated to form a large π bond, which is a rigid planar molecular structure. The tanshinone Ⅰ, tanshinone Ⅱ A and cryptotanshinone conjugate systems decrease in size. The molecular HOMO-LUMO bandgap increases with the decrease of molecular conjugation system. The λ_ (max) of all three molecules are mainly derived from the π → π * transitions of the electrons. Ethanol has a certain influence on the molecular structure and spectral properties of the above compounds, and the absorption spectra are red-shifted. At the same time, it was also found that ethanol changed the main transition of λ_ (max) electron of tanshinone Ⅰ. The λ max of tanshinone Ⅰ is mainly derived from the π → π * transition of HOMO → LUMO + 2 in the gas phase, and λ max in ethanol is mainly derived from the transition of π → π * of HOMO-5 → LUMO , This transition has obvious intramolecular electron transfer phenomenon.