Kundu Sohang, Berkelbach Timothy C
Department of Chemistry, Columbia University, New York, New York 10027, United States.
Initiative for Computational Catalysis, Flatiron Institute, New York, New York 10010, United States.
J Am Chem Soc. 2024 Sep 25;146(38):26041-26047. doi: 10.1021/jacs.4c05877. Epub 2024 Sep 5.
The application of an external, oriented electric field has emerged as an attractive technique for manipulating chemical reactions. Because most applications occur in solution, a theory of electric field catalysis requires treatment of the solvent, whose interaction with both the external field and the reacting species modifies the reaction energetics and thus the reaction rate. Here, we formulate such a transition state theory using a dielectric continuum model, and we incorporate dynamical effects due to solvent motion via Grote-Hynes corrections. We apply our theory to the Menshutkin reaction between CHI and pyridine, which is catalyzed by polar solvents, and to the symmetric S2 reaction of F with CHF, which is inhibited by polar solvents. At low applied field strengths when the solvent responds linearly, our theory predicts near-complete quenching of electric field catalysis. However, a qualitative treatment of the nonlinear response (i.e., dielectric saturation) shows that catalysis can be recovered at appreciable field strengths as solvent molecules begin to align with the applied field direction. The dynamical correction to the rate constant is seen to vary nonmonotonically with increasing solvent polarity due to contrasting effects of the screening ability and the longitudinal relaxation time of the solvent.
施加外部定向电场已成为一种用于操纵化学反应的有吸引力的技术。由于大多数应用发生在溶液中，电场催化理论需要考虑溶剂，溶剂与外部电场和反应物种的相互作用会改变反应能量，进而影响反应速率。在此，我们使用介电连续介质模型构建了这样一种过渡态理论，并通过格罗特-海因斯修正纳入了由于溶剂运动引起的动力学效应。我们将我们的理论应用于由极性溶剂催化的CHI与吡啶之间的门舒特金反应，以及由极性溶剂抑制的F与CHF的对称S2反应。在低外加场强下，当溶剂呈线性响应时，我们的理论预测电场催化几乎完全淬灭。然而，对非线性响应（即介电饱和）的定性处理表明，随着溶剂分子开始沿外加场方向排列，在相当可观的场强下催化作用可以恢复。由于溶剂的屏蔽能力和纵向弛豫时间的对比效应，速率常数的动力学修正随溶剂极性增加呈非单调变化。
