Role of Intact Hydrogen-Bond Networks in Multiproton-Coupled Electron Transfer

• DOI: 10.1021/jacs.0c10474
• Publication Date: 2020-12-18T17:04:53Z
• Authors: Walter D. Guerra; Emmanuel Odella; Maxim Secor; Joshua J. Goings; María N. Urrutia; Brian L. Wadsworth; Miguel Gervaldo; Leónides E. Sereno; Thomas A. Moore; Gary F. Moore; Sharon Hammes-Sch...; Ana L. Moore
• Keywords: Proton-Coupled Electron Transfer; Hydrogen atom

The essential role of a well-defined hydrogen-bond network in achieving chemically reversible multiproton translocations triggered by one-electron electrochemical oxidation/reduction is investigated using pyridylbenzimidazole–phenol models. two molecular architectures designed for these studies differ with respect to the position N atom on pyridyl ring. In one structures, extends uninterrupted across molecule from phenol group. Experimental and theoretical evidence indicates that an overall two-proton-coupled electron-transfer process (E2PT) takes place upon oxidation phenol. This E2PT yields pyridinium cation observed regardless cyclic voltammogram scan rate. contrast, when disrupted, as seen isomer, at high rates (∼1000 mV s–1) E1/2 characteristic one-proton-coupled (E1PT). At slow voltammetric (<1000 results irreversible which second proton-transfer step detected infrared spectroelectrochemistry. this case, we postulate initial intramolecular proton-coupled yielding E1PT product followed slow, likely intermolecular chemical involving proton transfer give product. Insights into behavior systems are provided calculations electrostatic potentials electric fields site transferring protons forward reverse processes. work addresses fundamental design principle constructing wires where translocated over varied distances Grotthuss-type mechanism.