Sowlati-Hashjin Shahin, Karttunen Mikko, Matta Chérif F
Department of Chemistry, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada.
The Centre of Advanced Materials and Biomaterials Research, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada.
J Phys Chem A. 2020 Jun 11;124(23):4720-4731. doi: 10.1021/acs.jpca.0c02569. Epub 2020 May 29.
Oriented external electric fields (OEEFs) have been shown to have great potential in being able to provide unprecedented control of chemical reactions, catalysis, and selectivity with applications ranging from H storage to molecular machines. We report a theoretical study of the atomic origins of molecular changes because of OEEFs since understanding the characteristics of OEEF-induced couplings between atomic and molecular properties is an important step toward comprehensive understanding of the effects of strong external fields on the molecular structure, stability, and reactivity. We focus on the atomic and molecular (bond) properties of a set of homo- (H, N, O, F, and Cl) and heterodiatomic (HF, HCl, CO, and NO) molecules under intense external electric fields in the context of quantum theory of atoms in molecules (QTAIM). It is shown that the atomic properties (atomic charges, energies, and localization indices) correlate linearly with the field strengths, but molecular properties (bond length, electron density at the bond critical point, and electron delocalization index) exhibit nonlinear responses to the imposed fields. In particular, the changes in the electron density distribution alter the shapes and locations of the zero-flux surfaces, atomic volumes, atomic electron population, and localization/delocalization indices. The topography and topology of the molecular electrostatic potential undergo dramatic changes. External fields also perturb the covalent-polar-ionic characteristic of the studied chemical bonds, hallmarking the impact of electric fields on the stability and reactivity of chemical compounds. The findings are well-rationalized within the framework of the QTAIM and form a coherent conceptual understanding of these effects in prototypical diatomic molecules.
已有研究表明，定向外部电场（OEEFs）在实现对化学反应、催化作用及选择性的前所未有的控制方面具有巨大潜力，其应用范围涵盖从氢存储到分子机器等领域。我们报告了一项关于OEEFs引起分子变化的原子起源的理论研究，因为了解OEEF诱导的原子与分子性质之间耦合的特征是全面理解强外部场对分子结构、稳定性和反应性影响的重要一步。我们在分子中原子的量子理论（QTAIM）背景下，重点研究了一组同核（H、N、O、F和Cl）及异核双原子（HF、HCl、CO和NO）分子在强外部电场下的原子和分子（键）性质。结果表明，原子性质（原子电荷、能量和定位指数）与场强呈线性相关，但分子性质（键长、键临界点处的电子密度和电子离域指数）对施加的场表现出非线性响应。特别是，电子密度分布的变化改变了零通量表面的形状和位置、原子体积、原子电子布居以及定位/离域指数。分子静电势的形貌和拓扑结构发生了显著变化。外部场还扰动了所研究化学键的共价 - 极性 - 离子特性，这标志着电场对化合物稳定性和反应性的影响。这些发现在QTAIM框架内得到了很好的解释，并对这些在典型双原子分子中的效应形成了连贯的概念理解。
