PNNL

Abstract

To enhance our understanding of the role of solvent on the thermodynamics and kinetics of forming Frustrated Lewis pairs (FLP), we carried out a systematic simulation study on these systems in dichloromethane and toluene solvents. These molecular systems are of particular interest due to their relevance in the catalytic hydrogenation and hydrogen storage processes. While the computed structural observables for both molecules are very similar, the slow molecular reorientation was consistent with the size of the species. The computed free energy profiles for the FLP in both solvents show similar gross characteristics but differ in details. We observe two well-defined contact and a solvent-separated regions with different well depths and barrier heights to dissociation. The kinetics of solute-pair interconversion was studied using transition state theory, comparing Kramers and Grote Hynes treatment of the dynamic response of the solvent. These rate results were used to predict solvent effects on dynamical features of contact solute-pair association. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The calculations were carried out using computer resources provided by BES. Method development benefits M86304. The scientific understanding of the systems studied benefits F63768