Electrochemical and Electrostatic Catalysis of Chemical Reactions

Abstract

Chemists appreciate that the rate of redox reactions can be manipulated by means of an electrical potential gradient. However, it was only in 2016 that we showed that an external electric field can also be used to catalyze non-redox reactions, thereby opening up a new dimension to chemical catalysis [Nature 2016 531, 88-91]. So-called electrostatic catalysis arises because most chemical species have some degree of polarity and so can be stabilized by an appropriately aligned electric field; when this occurs to a greater extent in transition states compared with reactants, reactions are catalyzed. However, by their nature such effects are highly directional and so implementing them in practical chemical systems is problematic. Significant effects can be achieved using scanning tunnelling microscopy to deliver the field, orient the molecules in it and measure its impact on the single molecule reaction rate. However, this approach is not scalable for bulk chemical synthesis. A much simpler approach is to make use of the internal electric fields of appropriately placed charged functional groups. In this way, the direction of the local field experienced by the reaction centre is fixed, and by associating the stabilization or destabilization with the protonation state of an acid or base group, it has the advantage of providing a convenient pH switch. Alternatively, one might envisage using electrodes to scale field effects but to date our efforts have resulted in electrochemical rather than electrostatically triggered reactions. Nonetheless these have value in their own right as a novel way to generate reactive intermediates in situ for reactions such as methylation. This talk will outline some of our recent progress in both electrochemical and electrostatic catalysis of organic reactions.