Time-resolved investigation of photocatalytic allene deracemization with kinetic modeling and force-field-based molecular dynamics.

Chiral thioxanthones were shown to be promising energy transfer catalysts for the photoinduced catalysis of organic molecules. In recent years, they were successfully applied in photocatalytic deracemization and kinetic resolution reactions with high enantiomeric excess rates. Previous computational investigations focused on static investigation mostly using density functional theory. In this study, we use force field-based molecular dynamics to explore the dissociation dynamics of a photocatalyst-substrate complex comprised of a primary allene amide (substrate) and a functionalized chiral thioxanthone (catalyst). Leveraging the quantum mechanically derived force-field framework enables the efficient simulation of the molecules in the ground and excited states. We derive kinetic parameters for the complex dissociation and use them in a kinetic reaction model. Our study indicates that the experimentally observed temperature optimum results from a different temperature dependence of the photoinduced energy transfer and the dissociation and association processes of the substrate-catalyst complexes.