Reversible conformational change coupled electron transfer (CCET) for stable redox-active molecules

Reversible electron transfer is a fundamental process that is essential in redox-active organic molecules and materials (ROMs) across biological, chemical, and energy technologies. Achieving stable and reversible redox behavior often requires careful molecular design or coupling electron transfer with a chemical step, such as proton-coupled electron transfer (PCET). In this study, we investigate a distinct stabilization mechanism based on conformational change coupled electron transfer (CCET). We show that acyclic 1,2-dicarbonyl compounds exhibit enhanced electrochemical stability by undergoing a conformational shift from skewed cis-geometries to more stable trans-conformations upon reduction, enabling stability even at more negative reduction potentials. Mechanistic studies demonstrate that CCET stabilizes the reduced state by allowing bond rotation that minimizes electron repulsion and delocalizes electron density by retaining a trans-planar geometry. Unlike PCET, which shifts reduction potentials positively, CCET enhances stability even at more negative potentials—breaking the conventional trade-off between redox potential and stability. Charge-discharge cycling of benzil shows 99.8% capacity retention over 500 cycles, demonstrating CCET as a powerful strategy for developing stable, high-performance ROMs for potential energy storage applications.