Ma Zhifeng, Yan Zeyin, Li Xin, Chung Lung Wa
Shenzhen Grubbs Institute, Department of Chemistry, and Guangdong Provincial Key Laboratory of Catalysis, Southern University of Science and Technology, 1088 Xueyuan Avenue, Shenzhen 518055, P. R. China.
J Phys Chem Lett. 2023 Feb 9;14(5):1124-1132. doi: 10.1021/acs.jpclett.2c03461. Epub 2023 Jan 27.
Quantum tunneling and external electric fields (EEFs) can promote some reactions. However, the synergetic effect of an EEF on a tunneling-involving reaction and its temperature-dependence is not very clear. In this study, we extensively investigated how EEFs affect three reactions that involve hydrogen- or (ground- and excited-state) carbon-tunneling using reliable DFT, DLPNO-CCSD(T1), and variational transition-state theory methods. Our study revealed that oriented EEFs can significantly reduce the barrier and corresponding barrier width (and ) through more electrostatic stabilization in transition states. These EEF effects enhance the nontunneling and tunneling-involving rates. Such EEF effects also decrease the crossover temperatures and quantum tunneling contribution, albeit with lower and thinner barriers. Moreover, EEFs can modulate and switch on/off the tunneling-driven 1,2-H migration of hydroxycarbenes under cryogenic conditions. Furthermore, our study predicts for the first time that EEF/tunneling synergy can control the chemo- or site-selectivity of one molecule bearing two similar/same reactive sites.
量子隧穿和外部电场（EEFs）可以促进一些反应。然而，EEF对涉及隧穿的反应的协同效应及其温度依赖性尚不清楚。在本研究中，我们使用可靠的密度泛函理论（DFT）、DLPNO-耦合簇单双激发（T1）方法以及变分过渡态理论方法，广泛研究了EEF如何影响涉及氢或（基态和激发态）碳隧穿的三个反应。我们的研究表明，定向EEF可以通过在过渡态中更多的静电稳定作用，显著降低势垒和相应的势垒宽度（以及）。这些EEF效应提高了非隧穿和涉及隧穿的反应速率。这种EEF效应还降低了交叉温度和量子隧穿贡献，尽管势垒更低、更薄。此外，在低温条件下，EEF可以调节并开启/关闭羟基卡宾的隧穿驱动的1,2-氢迁移。此外，我们的研究首次预测，EEF/隧穿协同作用可以控制具有两个相似/相同反应位点的分子的化学选择性或位点选择性。
