Harnessing electrostatic catalysis in single molecule, electrochemical and chemical systems: a rapidly growing experimental tool box

Abstract

Static electricity is central to many day-to-day practical technologies, from separation methods in the recycling of plastics to transfer inks in photocopying, but the exploration of how electrostatics affects chemical bonding is still in its infancy. As shown in the Companion Tutorial, the presence of an appropriately-oriented electric field can enhance the resonance stabilization of transition states by lowering the energy of ionic contributors, and the effect that follows on reaction barriers can be dramatic. However, the electrostatic effects are strongly directional and harnessing them in practical experiments has proven elusive until recently. This tutorial outlines some of the experimental platforms through which we have sought to translate abstract theoretical concepts of electrostatic catalysis into practical chemical technologies. We move step-wise from the nano to the macro, using recent examples drawn from single-molecule STM experiments, surface chemistry and pH-switches in solution chemistry. The experiments discussed in the tutorial will educate the reader in some of the viable solutions to gain control of the orientation of reagents in that field; from pH-switchable bond-dissociations using charged functional groups to the use of surface chemistry and surface-probe techniques. All of these recent works provide proof-of-concept of electrostatic catalysis for specific sets of chemical reactions. They overturn the long-held assumption that static electricity can only affect rates and equilibrium position of redox reactions, but most importantly, they provide glimpses of the wide-ranging potential of external electric fields for controlling chemical reactivity and selectivity.

TITAN: A Code for Modeling and Generating Electric Fields—Features and Applications to Enzymatic Reactivity

“…Often times, it is more meaningful to consider the projection of an electric field in one specific direction. As mentioned before, the exact orientation of the electric field—and its alignment with the considered bond or reaction axis—is of paramount importance to gauge its impact on the chemical reactivity. One can define the oriented electric field (OEF), , at point O ( a , b , c ) in a given direction as follows: …”

“…In recent years, (external) electric fields are increasingly being recognized as potent—and smart—effectors of chemical change . Their introduction in the toolbox of synthetic chemists could potentially be a game changer, opening new (and more sustainable) routes toward chemical synthesis .…”

“…The seemingly endless potential of electric fields as a means for the control of chemical reactivity has sparked a lot of interest, not only from the biochemistry community, but also from organic chemists, as well as others . As a consequence, there is an increasing need for computational and theoretical chemists to extend their activities and expertise to this new research field.…”

A greener catalyst for hydroboration of imines—external electric field modify the reaction mechanism

“…The directions of one‐dimension EEF are oriented along the X ‐, Y ‐, and Z ‐axes as showed in Figure . It is to be noted that the positive direction of the electric field vector is defined from the negative to the positive charge in Gaussian 09, which is opposite to the conventional definition in physics . Multiwfn program was used to draw the electron density difference (EDD) maps for the transition states relative to field‐free TSs.…”

“…Up to now, some endeavors had been done to develop a new methodology in accordance with green chemistry principles . An emerging greener catalyst is coming into one's sight, which is the external electric field (EEF), as a smart reagent to catalyze reactions had been reported by theory and experiment . Especially, the experiment of EEF by Aragonés et al paved the way for the development of EEF in catalyzing chemistry reactions.…”