Fast and Simple Evaluation of the Catalysis and Selectivity Induced by External Electric Fields

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 (FDB beta), 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 FDB beta energy barriers has a computational cost several orders of magnitude lower than the explicit electric field optimizations, and the errors of the FDB beta 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.