Wibowo-Teale Meilani, Huynh Bang C, Wibowo-Teale Andrew M, De Proft Frank, Geerlings Paul
School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
Research group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, B-1050 Brussels, Belgium.
Phys Chem Chem Phys. 2024 May 29;26(21):15156-15180. doi: 10.1039/d4cp00799a.
The extension of conceptual density-functional theory (conceptual DFT) to include external electromagnetic fields in chemical systems is utilised to investigate the effects of strong magnetic fields on the electronic charge distribution and its consequences on the reactivity of π-systems. Formaldehyde, HCO, is considered as a prototypical example and current-density-functional theory (current-DFT) calculations are used to evaluate the electric dipole moment together with two principal local conceptual DFT descriptors, the electron density and the Fukui functions, which provide insight into how HCO behaves chemically in a magnetic field. In particular, the symmetry properties of these quantities are analysed on the basis of group, representation, and corepresentation theories using a recently developed automatic program for symbolic symmetry analysis, QSYM. This allows us to leverage the simple symmetry constraints on the macroscopic electric dipole moment components to make profound predictions on the more nuanced symmetry transformation properties of the microscopic frontier molecular orbitals (MOs), electron densities, and Fukui functions. This is especially useful for complex-valued MOs in magnetic fields whose detailed symmetry analyses lead us to define the new concepts of and . Through these concepts, the deep connection between the vanishing constraints on the electric dipole moment components and the symmetry of electron densities and Fukui functions can be formalised, and the inability of the magnetic field in all three principal orientations considered to induce asymmetry with respect to the molecular plane of HCO can be understood from a molecular perspective. Furthermore, the detailed forms of the Fukui functions reveal a remarkable reversal in the direction of the dipole moment along the CO bond in the presence of a parallel or perpendicular magnetic field, the origin of which can be attributed to the mixing between the frontier MOs due to their subduced symmetries in magnetic fields. The findings in this work are also discussed in the wider context of a long-standing debate on the possibility to create enantioselectivity by external fields.
概念密度泛函理论（概念性DFT）扩展到包含化学系统中的外部电磁场，用于研究强磁场对电子电荷分布的影响及其对π体系反应性的后果。甲醛（HCO）被视为一个典型例子，利用电流密度泛函理论（电流DFT）计算来评估电偶极矩以及两个主要的局部概念性DFT描述符，即电子密度和福井函数，这有助于深入了解HCO在磁场中的化学行为。特别是，使用最近开发的用于符号对称性分析的自动程序QSYM，基于群论、表示论和余表示论对这些量的对称性进行分析。这使我们能够利用宏观电偶极矩分量上的简单对称性约束，对微观前沿分子轨道（MOs）、电子密度和福井函数更细微的对称性变换性质做出深刻预测。这对于磁场中复值MOs特别有用，其详细的对称性分析引导我们定义了 和 的新概念。通过这些概念，可以形式化电偶极矩分量消失约束与电子密度和福井函数对称性之间的深层联系，并且可以从分子角度理解在所考虑的所有三个主要方向上的磁场都无法诱导相对于HCO分子平面的不对称性。此外，福井函数的详细形式揭示了在平行或垂直磁场存在下，沿CO键的偶极矩方向发生了显著反转，其起源可归因于前沿MOs由于在磁场中对称性降低而导致的混合。本文的研究结果还在关于外部场能否产生对映选择性这一长期争论的更广泛背景下进行了讨论。
