Outstanding Energy Exchange between Organic Molecules and Metal Surfaces: Decomposition Kinetics of Excited Vinyl Derivatives Driven by the Interaction with a Cu(111) Surface

Here, we present a thorough theoretical study of the interaction, chemisorption, and thermal decomposition of three vinyl derivatives (acrolein, acrylonitrile, and acrylamide) on a pristine Cu(111) surface. To this, we have carried out density functional theory simulations, including weak van der Waals forces, in the framework of periodic boundary conditions. The results have shown strong anchoring between the molecules and the surface through the vinyl group, with the different functional groups driving molecular orientation. We explain the chemisorption with a simple chemical picture: donation from the occupied lone pair and g orbitals of the molecule to the surface and backdonation from the surface to the pi* orbital of the molecule (pi-backbonding). Ab initio molecular dynamics simulations highlight the efficient energy exchange in excited adsorbed molecules and energy dissipation through the interface, which takes place in a few hundreds of femtoseconds. The study of the dynamics also allows to comprehend the catalytic effect of the chemisorption, which is reflected not only in the larger amount of fragmentation but also in the much richer spectrum of fragments observed with respect to the molecular decomposition in the gas phase.