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采用密度泛函理论(DFT)方法和极化连续介质模型(PCM),在B3LYP和混合基组(C,H原子采用6-31G(d);Zn、N、O采用6-311++G(2d,p))水平对L-苏氨酸卟啉锌(L-Thr-TPPZnII)的基态几何构型进行了优化;以优化得到的稳定构型为基础,采用含时密度泛函理论(TD-DFT)方法,在相同基组水平进行了电子圆二色谱(ECD)研究,根据计算获得的电子跃迁吸收波长(λ)和电子旋转强度(R)拟合得到了ECD谱.除吸收峰位置有一定的蓝移外,计算获得的ECD谱带形与实验谱基本吻合.通过跃迁性质分析对实验光谱进行了理论解析.理论研究发现L-Thr-TPP ZnII的ECD谱吸收带主要来源于分子内的π→π*的荷移跃迁.353 nm处的负性Cotton效应具有明显的分子内电子转移特征,电子从卟啉环向氨基酸残基转移.
Density functional theory (DFT) method and polarization continuum medium model (PCM) were used in B3LYP and mixed base groups (6-31G (d) for C and H atoms and 6-311 ++ G (2d, p)) was optimized for the L-Thr-TPPZnII. Based on the optimized stable configuration, the time-dependent density functional theory TD-DFT) was used to study the electronic circular dichroism (ECD) at the same fundamental level, and the ECD spectra were obtained by the calculated electron transition absorption wavelength (λ) and electron spin strength (R) The experimental results show that the ECD band of L-Thr-TPP ZnII is mainly derived from The intramolecular π → π * charge transfer transition.The negative Cotton effect at 353 nm has a remarkable intramolecular electron transfer characteristic, the electron transfer from the porphyrin ring to the amino acid residues.