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

The current-voltage characteristics of a single-moleculejunction are determined by the electronic coupling Gamma betweenthe electronic states of the electrodes and the dominant transportchannel(s) of the molecule. Gamma is profoundly affected by thechoice of the anchoring groups and their binding positions on thetip facets and the tip-tip separation. In this work, mechanicallycontrollable break junction experiments on the N,N '-bis(5-ethynylbenzenethiol-salicylidene)ethylenediamineare presented, in particular, the stretch evolution of Gamma withincreasing tip-tip separation. The stretch evolution of Gamma is characterized by recurring local maxima and can be related to thedeformation of the molecule and sliding of the anchoring groups abovethe tip facets and along the tip edges. A dynamic simulation approachis implemented to model the stretch evolution of Gamma, which capturesthe experimentally observed features remarkably well and establishesa link to the microscopic structure of the single-molecule junction.

Automated summary

The current-voltage characteristics of a single-molecule junction depend on the electronic coupling between the electrodes and the molecule's transport channels. This coupling, known as Gamma, is influenced by the choice of anchoring groups and their positions on the tip facets as well as the tip-tip separation. In this study, experiments on a specific molecule, N,N'-bis(5-ethynylbenzenethiol-salicylidene)ethylenediamine, using mechanically controllable break junction, reveal the stretch evolution of Gamma with increasing tip-tip separation. A dynamic simulation approach successfully models this stretch evolution and establishes a connection to the microscopic structure of the single-molecule junction.