Surface-site reactivity in small-molecule adsorption: A theoretical study of thiol binding on multi-coordinated gold clusters

Background: The adsorption of organic molecules on metal surfaces has a broad array of applications, from device engineering to medical diagnosis. The most extensively investigated class of metal–molecule complexes is the adsorption of thiols on gold. Results: In the present manuscript, we investigate the dependence of methylthiol adsorption structures and energies on the degree of unsaturation at the metal binding site. We designed an Au(20) cluster with a broad range of metal site coordination numbers, from 3 to 9, and examined the binding conditions of methylthiol at the various sites. Conclusion: We found that despite the small molecular size, the dispersive interactions of the backbone are a determining factor in the molecular affinity for various sites. Kink sites were preferred binding locations due to the availability of multiple surface atoms for dispersive interactions with the methyl groups, whereas tip sites experienced low affinity, despite having low coordination numbers.