Molecular Mechanochemistry Understood at the Nanoscale: Thiolate Interfaces and Junctions with Copper Surfaces and Clusters

Two very different approaches to activate chemical bonds, nanoscale mechanochemistry and the ubiquitous thermochemistry, are studied and compared for a range of different thiolate/copper interfaces and junctions using self-assembled monolayers (SAMs) on perfect surfaces as well as single molecules anchored at steps and on clusters. In nanoscale mechanochemistry the activation proceeds by supplying locally pure mechanical energy to the desired atom(s) and/or bond(s). Using both dynamic and static electronic structure methods we predict vastly different reaction pathways and product classes for the two types of activation. These differences can be understood in terms of directional mechanical manipulation of coordination numbers and system fluctuations in the process of mechanical activation which affect the coupling of the thiolate molecular orbitals to the metal part of the molecule/metal junction or interface. The observed conceptual differences are huge in size and general in nature.