Kinetics and Dynamics of Adsorption and Desorption on Chiral Surfaces

Lead Research Organisation: University of Cambridge
Department Name: Chemistry

Abstract

There has been considerable interest, over the past couple of decades, in the prospects for asymmetric chemistry conducted at surfaces that exhibit microscopic chirality, either due to their inherent crystalline structure or conferred by modification involving chiral molecules. For the most part, investigations have focussed upon elucidation of the equilibrium structure and energetics of such systems, merely inferring likely consequences for dynamics and kinetics rather than addressing them directly. Recently, however, experiments designed to reveal asymmetric kinetic effects (for example, in explosive desorption) have been reported, and there would seem also to be some considerable promise in making use of supersonic molecular beams to study the dynamics of asymmetric adsorption.

The present project aims to explore this same territory from a computational perspective. Application of first-principles molecular dynamics will allow us
to confirm the existence of (and assess the magnitude of) chiral effects in both adsorption and desorption processes for a range of candidate systems. Initially, we will focus upon the intrinsically chiral Cu{531} surface, which combines a high density of chiral kink sites with a relatively low reactivity suitable for binding comparatively delicate chiral molecules without dissociation into achiral products. Probe molecules will likely include both chiral and achiral species, such as organic acids and related compounds. It is hoped that the work will stimulate experimental work in this exciting area.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/N509620/1 01/10/2016 30/09/2022
2112388 Studentship EP/N509620/1 01/10/2018 31/03/2022 Sabine Matysik
 
Description We were able to show that chiral surfaces can induce rotations of molecules that are desorbing from such a surface. We employed a set of quantum chemistry methods applied to a model system, for which we chose the dissociative adsorption of formic acid on both chiral and achiral Cu surfaces. The chiral surface induced a significantly larger and more directed rotation of desorbing formic acid molecules than the achiral surface. It also induced only one sense of rotation, which is then uniquely associated to the chirality of the surface. This could have important implications on the adsorption probabilities of molecules on chiral surfaces and provides interesting general insight into the interaction between molecules and chiral surfaces.
We could not reproduce the same effect for the very spherical molecule methane on Pt surfaces. This outcome might be connected to the molecules' intrinsically high symmetry or caused by an important difference in the adsorption geometry on the surface, which we will investigate further.
Exploitation Route We hope to inspire experimental designs that will verify and apply our theoretical findings experimentally. Our results could have important implications for chiral recognition, sensors specific to molecular rotations and potentially pharmaceutical synthesis pathways that include a synthesis step mediated or catalysed by a chiral surface.
Sectors Chemicals,Energy,Pharmaceuticals and Medical Biotechnology