Unifying Conceptual Density Functional and Valence Bond Theory: The Hardness–Softness Conundrum Associated with Protonation Reactions and Uncovering Complementary Reactivity Modes,Journal of the American Chemical Society

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Unifying Conceptual Density Functional and Valence Bond Theory: The Hardness–Softness Conundrum Associated with Protonation Reactions and Uncovering Complementary Reactivity Modes
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2020-11-12 , DOI: 10.1021/jacs.0c09041
Thijs Stuyver ₁ , Sason Shaik ₁

Affiliation

In this study, we address the long-standing issue—arising prominently from conceptual density functional theory (CDFT)—of the relative importance of electrostatic, i.e., “hard–hard”, versus spin-pairing, i.e., “soft–soft”, interactions in determining regiochemical preferences. We do so from a valence bond (VB) perspective and demonstrate that VB theory readily enables a clear-cut resolution of both of these contributions to the bond formation/breaking process. Our calculations indicate that appropriate local reactivity descriptors can be used to gauge the magnitude of both interactions individually, e.g., Fukui functions or HOMO/LUMO orbitals for the spin-pairing/(frontier) orbital interactions and molecular electrostatic potentials (and/or partial charges) for the electrostatic interactions. In contrast to previous reports, we find that protonation reactions cannot generally be classified as either charge- or frontier orbital-controlled; instead, our results indicate that these two bonding contributions generally interplay in more subtle patterns, only giving the impression of a clear-cut dichotomy. Finally, we demonstrate that important covalent, i.e., spin pairing, reactivity modes can be missed when only a single spin-pairing/orbital interaction descriptor is considered. This study constitutes an important step in the unification of CDFT and VB theory.

中文翻译：

统一概念密度泛函和价键理论：与质子化反应和揭示互补反应模式相关的软硬难题

在这项研究中，我们解决了长期存在的问题——主要来自概念密度泛函理论 (CDFT)——静电的相对重要性，即“硬-硬”，与自旋对，即“软-软” ，确定区域化学偏好的相互作用。我们从价键 (VB) 的角度这样做，并证明了 VB 理论可以很容易地明确解决这些对键形成/断裂过程的贡献。我们的计算表明，适当的局部反应性描述符可用于单独测量两种相互作用的大小，例如，Fukui 函数或 HOMO/LUMO 轨道用于自旋对/（前沿）轨道相互作用和分子静电势（和/或部分电荷) 静电相互作用。与之前的报道相比，我们发现质子化反应通常不能归类为电荷控制或前沿轨道控制；相反，我们的结果表明，这两种结合贡献通常以更微妙的模式相互作用，只会给人一种清晰的二分法的印象。最后，我们证明了当仅考虑单个自旋配对/轨道相互作用描述符时，可能会错过重要的共价键（即自旋配对）反应模式。这项研究是 CDFT 和 VB 理论统一的重要一步。自旋配对，当仅考虑单个自旋配对/轨道相互作用描述符时，可能会错过反应模式。这项研究是 CDFT 和 VB 理论统一的重要一步。自旋配对，当仅考虑单个自旋配对/轨道相互作用描述符时，可能会错过反应模式。这项研究是 CDFT 和 VB 理论统一的重要一步。

更新日期：2020-11-12

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