Abstract
In the oriented external electric-field-driven catalysis, the reaction rates and the selectivity of chemical reactions can be tuned at will. The activation barriers of chemical reactions within external electric fields of several strengths and directions can be computationally modeled. However, the calculation of all of the required field-dependent transition states and reactants is computationally demanding, especially for large systems. Herein, we present a method based on the Taylor expansion of the field-dependent energy of the reactants and transition states in terms of their field-free dipole moments and electrical (hyper)polarizabilities. This approach, called field-dependent energy barrier (FDBβ), allows systematic one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) representations of the activation energy barriers for any strength and direction of the external electric field. The calculation of the field-dependent FDBβ energy barriers has a computational cost several orders of magnitude lower than the explicit electric field optimizations, and the errors of the FDBβ barriers are within the range of only 1–2 kcal·mol–1. The achieved accuracy is sufficient for a fast-screening tool to study and predict potential electric-field-induced catalysis, regioselectivity, and stereoselectivity. As illustrative examples, four cycloadditions (1,3-dipolar and Diels–Alder) are studied.
Highlights
The interaction between molecules and external electric fields (EEFs) generates a broad range of effects.[1]
After that, taking advantage of the computational benefits of the FDBβ methodology, we have studied the DA cycloaddition between C60 fullerene and a diene
The FDBβ methodology only requires the evaluation of field-free dipole moments and
Summary
The interaction between molecules and external electric fields (EEFs) generates a broad range of effects.[1]. The electric-field-induced chemistry can be studied in the electrochemical double layer,[14] the interface layer between the electrode and the electrolyte In this region, the molecular electron density of the reactants and their reactivity can be altered by the electric fields generated by the electrode.[15] The characterization of the electric field generated in the electrochemical double layer is a complex task, the combination of the vibrational stark shift spectroscopy[16] and computational modeling is paving the way.2a,17. The in-depth study of the field-dependent energy barriers (FDB) for one specific reaction involves computation of the reactants and the corresponding transition states (TSs) within external electric fields of several different strengths and directions. It only requires the calculation of the field-free energy, μ, α, and β tensors for the reactants and transition states, which can be calculated analytically using several quantum chemistry packages We refer to this approach to compute the FDB based on eq 4 as FDBβ. Pnr was computed using double-ζ basis, we have checked that calculating Pnr with the triple-ζ basis leads to very similar results for the field-dependent energy barriers (for more details, see Table SI1)
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