Abstract: Understanding the mechanism and kinetics of chemical processes in a complex fluctuating environment is a challenge. In my contribution I will start with providing a short overview of the strategy that is used at the Amsterdam Center for Multiscale Modeling (ACMM) to address these challenges. 

 

Subsequently, I will demonstrate how DFT-based molecular dynamics of proto-type reactions in solution can provide novel insight in the effect of solvent molecules on the mechanism and kinetics. Specifically, we considered aqueous asymmetric transfer-hydrogenation of ketones catalysed by Noyori-type ruthenium complex. We employed a realistic model of the reacting species, with the metal catalyst and substrate embedded by solvent molecules in a periodic box. Combining density-functional theory with advanced free-energy and path-sampling molecular dynamics techniques, we calculated the energetics, mechanism, and kinetics of the complete catalytic reaction cycle. The simulations show how the solvating water molecules play an active role in the reaction. In particular for the proton transfer steps we find that the reaction mechanism is fundamentally different from that predicted by gas-phase calculations. The path-sampling simulations provide a molecular picture of the kinetics of the reactive pathways, and demonstrate that the proton transfer step can proceed via various distinct pathways involving either the catalyst or the solvent as proton donor. The latter effect can be interpreted as a consequence of the fact that an aqueous proton is an extended object that involves multiple solvation shells. More in general, our simulations demonstrate that a proper understanding of reactions in aqueous solution requires computational and experimental studies that probe the reacting species and nearest solvating molecules in full atomistic detail.

 

About the Speaker: Dr. Evert Jan Meijer, is a full professor of chemistry, holding the chair of Molecular Simulation at the Van ‘t Hoff Insitute for Molecular Sciences at the University of Amsterdam. He is also affiliated with the Amsterdam Center for Multiscale modeling. He is member of the board of the international Master program ATOSIM. Evert Jan Meijer got a MSc in theoretical physics and a PhD in computational chemistry at the Utrecht University. He held various research positions outside The Netherlands, including a position at the IBM Research Laboratory in Switzerland, before returning as a faculty member of the University of Amsterdam in 1998. One of his current research lines of focuses on employing advanced molecular simulations techniques to provide understanding of the role of a fluctuating environment on chemical processes, including catalytic reactions in aqueous solution and enzymatic reactions.