Stretch Evolution of Electronic Coupling of the Thiophenyl Anchoring Group with Gold in Mechanically Controllable Break Junctions

The current-voltage characteristics of a single-molecule junction are determined by the electronic coupling Γ between the electronic states of the electrodes and the dominant transport channel(s) of the molecule. Γ is profoundly affected by the choice of the anchoring groups and their binding positions on the tip facets and the tip-tip separation. In this work, mechanically controllable break junction experiments on the ,'-bis(5-ethynylbenzenethiol-salicylidene)ethylenediamine are presented, in particular, the stretch evolution of Γ with increasing tip-tip separation. The stretch evolution of Γ is characterized by recurring local maxima and can be related to the deformation of the molecule and sliding of the anchoring groups above the tip facets and along the tip edges. A dynamic simulation approach is implemented to model the stretch evolution of Γ, which captures the experimentally observed features remarkably well and establishes a link to the microscopic structure of the single-molecule junction.