Reactivity of Diethylstilbestrol Toward Electrogenerated Superoxide in N , N ‐Dimethylformamide Through Proton‐Coupled Electron Transfer

The superoxide radical anion (O 2 • − ) scavenging mechanism of diethylstilbestrol (DesH 2 ) was investigated using in situ UV–vis spectroelectrochemistry, cyclic voltammetry, and DFT/TD‐DFT calculations. While thermodynamic evaluation indicates that all tested stilbene derivatives possess favorable free energy changes for scavenging O 2 •− , comparative cyclic voltammetry revealed that only DesH 2 and 4,4′‐dihydroxystilbene exhibit distinct scavenging waves. On the electrochemical timescale, effective scavenging requires a 1:1 stoichiometric proton‐coupled electron transfer (PCET) mechanism involving the transfer of two protons and one electron from a single molecule. Thermodynamic and mechanistic analyses supported this PCET pathway. Crucially, the diethyl substituents in DesH 2 stabilize the generated radical anion and maintain the structural integrity of the stilbene core, enabling further two‐ to four‐electron oxidation. Furthermore, subsequent chemical steps (e.g., adduct decomposition or OH addition) pull the reaction equilibrium forward to dynamically drive the initial PCET process.