Abstract

In this work, the density functional theory with B3LYP hybrid functional was employed to calculate quantities useful for estimating the behavior of pyridine, pyrazine and their derivatives monosubstituted with Cl or Br atom, when exposed to low-energy electron impact. Vertical electron affinities obtained in several Pople basis sets and in aug-cc-pVTZ basis set are reported. Although some of the investigated molecules do not form stable anions, the results are in a satisfactory agreement with the available, albeit sparse experimental data, if the diffuse functions are included in calculations. It was found that the 6-31+G* basis is sufficient and its further enlargement does not significantly change the results. At this level of theory, potential energy curves, supported by enthalpies of dissociation to the neutral and anion fragment, were also determined for the description of the dissociative electron attachment. According to B3LYP, the potential energy curves of the halogen bond are almost repulsive in halopyridines, whereas halopyrazine anions require small activation energy for dissociation. Vertical electron affinities, enthalpies and equilibrium C-X distances (X=H, Cl, Br) were also calculated using Møller-Plesset second-order perturbation theory.

Graphic Abstract

中文翻译：

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DFT研究与吡啶，吡嗪及其卤代衍生物的低能电子相互作用

摘要

在这项工作中，采用具有B3LYP杂合功能的密度泛函理论来计算可用于估算暴露于低能电子撞击时吡啶，吡嗪及其衍生物被Cl或Br原子单取代的行为的量。报告了在几个Pople基集和在aug-cc-pVTZ基集中获得的垂直电子亲和力。尽管某些被研究的分子不能形成稳定的阴离子，但如果计算中包括扩散函数，则结果与可用的实验数据令人满意，尽管实验数据稀疏。发现6-31 + G *基已足够，并且其进一步扩大不会显着改变结果。在此理论水平上，势能曲线由离解到中性和阴离子碎片的焓所支撑，还确定了用于解离电子附着的描述。根据B3LYP，卤代吡啶中卤素键的势能曲线几乎是排斥的，而卤代吡嗪阴离子离解所需的活化能很小。垂直电子亲和力，焓和平衡CX距离（X = H，Cl，Br）也使用Møller-Plesset二阶摄动理论进行计算。

图形摘要