Electronic Excitations in Pyrrole: A Test Case for Determination of Chromophores in the Chromogenic Effects of Neurotoxic Hydrocarbons by Time-Dependent Density Functional Theory and Single-Excitation Configuration Interaction Methods
Electronic Excitations in Pyrrole: A Test Case for Determination of Chromophores in the Chromogenic Effects of Neurotoxic Hydrocarbons by Time-Dependent Density Functional Theory and Single-Excitation Configuration Interaction Methods
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DOI：
10.1006/jmsp.2002.8622
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发表时间：
2002-11
影响因子：
1.4
通讯作者：
C. Zhan;D. Dixon
中科院分区：
文献类型：
--
作者：
C. Zhan;D. Dixon
摘要采用含时密度泛函理论（TD-DFT）和单激发组态相互作用（CIS）方法对吡咯分子的电子激发态进行了计算，考察了第一性原理电子结构方法在预测吡咯类化合物电子激发光谱中的可靠性。TD-DFT和CIS的计算结果令人满意，与现有的实验数据相比，特别是对低激发态。的TD-DFT和CIS计算提供的激发能的下限和上限，分别为低洼的单重激发态。这些结果表明，这些方法可用于预测的激发光谱，特别是激发能为低的激发态，负责神经毒性烃，这被认为是取代的吡咯和它们的加合物与蛋白质的显色效应的发色团。作为一个实际应用的例子，计算了广泛使用的2，5-二甲基吡咯的光谱。结果表明，2，5-二甲基吡咯分子在可见光谱区（400-700 nm）没有吸收，表明在530 nm处观察到的吸收和2，5-二甲基吡咯的颜色是由于另一种物质，可能是2，5-二甲基吡咯自氧化的产物。这表明，需要从显色性与神经毒性的关系方面重新审查先前报告的神经毒性γ-二酮生化反应实验研究的结论。
Abstract Time-dependent density functional theory (TD-DFT) and single-excitation configuration interaction (CIS) calculations on the electronic excitations in pyrrole have been performed to examine the reliability of these first-principles electronic structure methods in predicting electronic excitation spectraof pyrrole-containing compounds. Both the TD-DFT and CIS calculations led to satisfactory results when compared to available experimental data, particularly for low-lying excited states. The TD-DFT and CIS calculations provide lower and upper limits of the excitation energies, respectively, for low-lying singlet excited states. These results suggest that these methods can be used for the prediction of the excitation spectra, particularly the excitation energies for low-lying excited states, of chromophores responsible for the chromogenic effects of neurotoxic hydrocarbons, which are believed to be substituted pyrroles and their adducts with proteins. As an example of a practical application, the spectrum of the widely used 2,5-dimethylpyrrole has been calculated. It is shown that the 2,5-dimethylpyrrole molecule does not have an absorption in the region of the visible spectrum (400–700 nm), suggesting that the absorption observed at 530 nm and the color of 2,5-dimethylpyrrole is due to another species, probably a product of possible 2,5-dimethylpyrrole autoxidation. This suggests that the conclusions from previously reported experimental studies of biochemical reactions of neurotoxic γ-diketones need to be reexamined in terms of the relationship of chromogenicity to neurotoxicity.