Proton-Gated Torsional Spring for Molecular Energy Storage

A molecular torsional spring was developed to demonstrate a new strategy for molecular energy storage. Protonation of an N-pyridylsuccinimide rotor lowers the rotational barrier and shifts the equilibrium toward the higher-energy syn-atropisomer. Neutralization kinetically traps this high-energy state, which is stable at room temperature for years. On heating, the stored energy is released and measured by DSC, as the atropisomer reverts to its equilibrium ratio. Since switching involves only single-bond rotation, the system avoids reactive intermediates and retains its performance over repeated energy storage-release cycles.