硅上的亲核取代反应在强振动耦合下的研究：来自高精度从头算视角的深入洞察
Nucleophilic substitution at silicon under vibrational strong coupling: Refined insights from a high-level ab initio perspective
AI总结：
该研究通过高精度从头算方法探讨了强振动耦合下硅基亲核取代反应的机理，揭示了偶极特性在振动极子形成中的关键作用。
摘要：
我们从高精度从头算量子化学和极子化学的角度研究了1-苯基-2-三甲基硅基乙炔（PTA）在强振动耦合（VSC）下的双分子亲核取代（S_N2）反应。具体而言，我们针对矛盾的机理提案、VSC下的腔体诱导电子修正以及之前争议的PTA中Si-C伸缩运动对振动极子形成的相关性进行了探讨。我们首先提供了基于密度泛函理论和高阶耦合簇结果的两步机制的计算证据，识别了新的相遇和产物复合物，并阐明了稀疏基组函数对阴离子反应性系统定性正确描述的相关性。随后我们显示，腔体诱导的偶极波动修正电子能可以在腔体生氧-Oppenheimer耦合簇理论的水平上显著，并讨论了其对所提出的两步机制的定性影响，考虑了腔体诱导的分子重取向。最后我们显示，PTA中Si-C伸缩贡献到实验相关的双峰特征表现出主导的偶极特性，这使其在红外线线性响应和振动极子形成中至关重要，尽管存在CH3摇摆贡献。偶极特性沿断裂的Si-C键最终被证明能解释所提出两步机制中的拉比分裂。我们的工作细化了在VSC下PTA的S_N2反应的微观视角，并突显了近期在从头算极子化学领域针对VSC领域的最新发展。
英文摘要：
We study the bimolecular nucleophilic substitution (S$_\mathrm{N}$2) reaction of 1-phenyl-2-trimethylsilylacetylene (PTA) under vibrational strong coupling (VSC) from the perspective of high-level ab initio quantum and polaritonic chemistry. Specifically, we address conflicting mechanistic proposals, cavity-induced electronic corrections under VSC and the relevance of a previously debated Si-C-stretching motion of PTA for vibrational polariton formation. We first provide computational evidence for a two-step mechanism based on density functional theory and high-level coupled cluster results, identify new encounter and products complexes and illustrate the relevance of diffuse basis functions for a qualitatively correct description of anionic reactive systems. We subsequently show that cavity-induced dipole fluctuation corrections of electronic energies can be significant on the level of cavity Born-Oppenheimer coupled cluster theory and discuss their qualitative impact on the proposed two-step mechanism taking into account cavity-induced molecular reorientation. We finally show that the Si-C-stretching contribution to the experimentally relevant double-peak feature of PTA exhibits a dominant dipole character, which renders it central for linear IR response and vibrational polariton formation despite the presence of CH$_3$-rocking contributions. The dipole character along the cleaving Si-C-bond is eventually shown to rationalize Rabi splittings throughout the proposed two-step mechanism. Our work refines the microscopic perspective on the S$_\mathrm{N}$2 reaction of PTA under VSC and highlights recent developments in ab initio polaritonic chemistry for the VSC regime.
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