Mechanochemistry of Ring-Opening Reactions: From Cyclopropane in the Gas Phase to Thiotic Acid on Gold in the Liquid Phase

We have studied the mechanochemistry of a system consisting of a PEG molecular model with a bidentate thiolate anchor covalently attached to a metallic surface and subject to solvation. Functionalized gold nanoparticles show increasing potential in real-life applications. In these situations, they are exposed to different chemical environments and to mechanical tension due to contact and friction with other molecules. We have used accelerated ab initio molecular dynamics to study the effect of mechanical forces on the chemical reactivity of such a system. Although the results reported here can only be considered as preliminary, a very interesting mechanochemical behavior is displayed by the system under study. We have focused on the attack of OH− on either anchoring S atom. We have determined the free energy of activation for each reaction at two values of a constant external force acting on the molecule and, thus, stressing the gold–thiolate interface. We have also studied the thermal and mechanical detachment of aliphatic and aromatic thiolates adsorbed on gold surfaces. In this case, we have found an interesting change in mechanism of the mechanical detachment that depends on the nature of electronic properties of the carbon skeleton, but that remains unchanged for substituents of widely different nature on the aromatic ring.