Tuning the binding configurations of single-molecule junctions by molecular co-assembly.

Significant variability issues in metal-molecule contacts, such as adsorption geometry, lead to characteristic variability in the electrical responses of individual molecules. Herein, co-assembling 1-ethylimidazole (EIM) on Au(111) has been shown to be a feasible and effective strategy for tuning the binding configurations of pyridine-linked molecular junctions in the most common aqueous environments and atmospheric environments. The single-molecule conductance measurements clearly show a transition from multiple conductance peaks to a single conductance peak with increasing EIM concentration. Raman spectroscopy and DFT calculations suggest that the thermodynamically favorable EIM adsorbate results in the vertical orientation of the bipyridine.