用Hirshfeld电荷定量标度亲电性和亲核性:含氮体系(英文)

Hirshfeld Charge as a Quantitative Measure of Electrophilicity and Nucleophilicity: Nitrogen-Containing Systems

准确预测化学过程中分子内各原子提供或接受电子的能力以及化学反应可能的位点,即定量确定亲电性、亲核性和区域选择性,是一个十分重要却仍然亟待解决的课题.此前,基于我们新近提出的信息守恒原理,曾建议使用Hirshfeld电荷和信息增益作为两个等价的描述符用于此目的.我们的这个想法已经被成功地应用于两个系列的分子体系,且其有效性得到了充分的验证.然而,先前我们只考察了碳元素的这些性质,所以其结论的普遍性仍存在疑问.我们尚不清楚它是否适用于其他元素,而且对于同一元素的不同价态该结论是否适用也不清楚.为此,本文将考察含氮体系.对5个不同类别的含氮体系共计40个分子进行了研究,其中包括重氮苯、偶氮、重氮、一级和二级胺体系.结果表明,对所有五个含氮体系其Hirshfeld电荷与实验得到的亲电性和亲核性标度之间仍然存在着较强的线性关联.然而,这些相关性却依赖于氮元素的化合价类型和键合环境.该线性关系只能在同一类型中成立.我们对其可能的原因进行了讨论.

To accurately predict the capability and possible reaction site for atoms in molecules to donate or accept electrons in chemical processes, i.e., to quantitatively determine electrophilicity, nucleophilicity, and regioselectivity, is an important yet incomplete task. Earlier, we proposed using the Hirshfeld charge and information gain as two equivalent descriptors for this purpose, based on the Information Conservation Principle we recently proposed. This idea was successfully applied to two series of molecular systems to confirm its validity. However, our previous work is hindered by the fact that the involved element is carbon. It is unclear if it applies to other elements and to different valence states of the same element. In this study, to address these issues, the method was applied to nitrogen-containing systems. Five different categories of compounds were studied, including benzenediazonium, azodicarboxylate, diazo, and primary and secondary amines, with a total of 40 molecules. The results show that there are strong linear correlations between the Hirshfeld charge and their experimental scales of electrophilicity and nucleophilicity. However, these correlations depend on the valence state and bonding environment of the nitrogen element. The linear relationship only holds within the same category. Possible reasons for this observation are discussed.