Clarys Tom, Stuyver Thijs, De Proft Frank, Geerlings Paul
Research Group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium.
Phys Chem Chem Phys. 2021 Jan 21;23(2):990-1005. doi: 10.1039/d0cp05277a.
The extension of the E = E[N, v] functional for exploring chemical reactivity in a conceptual DFT context to include external electric fields is discussed. Concentrating on the case of a homogeneous field the corresponding response functions are identified and integrated, together with the conventional response functions such as permanent dipole moment and polarizability, in an extended response function tree associated with the E = E[N, v, ε] functional. In a case study on the dihalogens F2, Cl2, Br2, I2 the sensitivity of condensed atomic charges (∂q/∂ε) is linked to the polarizability of the halogen atoms. The non-integrated (∂ρ(r)/∂ε) response function, directly related to the field induced density change, is at the basis of these features. It reveals symmetry breaking for a perpendicular field, not detectable in its atom condensed counterpart, and accounts for the induced dipole moment directly related to the molecular polarizability. The much higher sensitivity of the electronic chemical potential/electronegativity as compared to the chemical hardness is highlighted. The response of the condensed Fukui functions to a parallel electric field increases when going down in the periodic table and is interpreted in terms of the extension of the outer contours in the non-condensed Fukui function. In the case of a perpendicular field the (∂f(r)/∂ε) response function hints at stereoselectivity with a preferential side of attack which is not retrieved in its condensed form. In an application the nucleophilic attack on the carbonyl group in H2CO is discussed. Similar to the dihalogens, stereoselectivity is displayed in the Fukui function for nucleophilic attack (f+) in the case of a perpendicular electric field, and opposite to the one that would arise based on the induced density. Disentangling the expression for the evolution of the Fukui function in the presence of an electric field reveals that this difference can be traced back to local differences in the polarization or induced density between the anionic and the neutral system. This difference may be exploited, e.g. for an appropriately substituted H2CO, to generate enantioselectivity.
讨论了在概念性密度泛函理论（DFT）背景下用于探索化学反应性的E = E[N, v]泛函扩展到包含外部电场的情况。聚焦于均匀场的情况，确定并整合了相应的响应函数，以及诸如永久偶极矩和极化率等传统响应函数，将其纳入与E = E[N, v, ε]泛函相关的扩展响应函数树中。在对二卤化物F2、Cl2、Br2、I2的案例研究中，凝聚原子电荷的灵敏度（∂q/∂ε）与卤素原子的极化率相关联。与场诱导密度变化直接相关的未积分响应函数（∂ρ(r)/∂ε）是这些特征的基础。它揭示了垂直场导致的对称性破缺，这在其原子凝聚对应物中无法检测到，并且解释了与分子极化率直接相关的诱导偶极矩。突出了电子化学势/电负性与化学硬度相比更高的灵敏度。凝聚福井函数对平行电场的响应在元素周期表中向下移动时增加，并根据非凝聚福井函数中外轮廓的扩展进行解释。在垂直场的情况下，（∂f(r)/∂ε）响应函数暗示了具有优先攻击侧的立体选择性，而其凝聚形式无法体现这一点。在一个应用中，讨论了对H2CO中羰基的亲核攻击。与二卤化物类似，在垂直电场的情况下，福井函数对亲核攻击（f+）显示出立体选择性，并且与基于诱导密度产生的立体选择性相反。解开电场存在时福井函数演化的表达式表明，这种差异可以追溯到阴离子和中性系统之间极化或诱导密度的局部差异。例如，对于适当取代的H2CO，这种差异可用于产生对映选择性。
