Efficient control on orbital energies and vibrational properties of single molecules embedded in electrochemical scanning tunneling microscopy junctions

In spite of remarkable advances in manipulating physical and chemical properties at nanoscale, broadly tuning molecular charge and vibrational modes of single molecules embedded in molecular junctions escaped so far to an efficient control. In this work, we present theoretical results indicating the possibility to continuously drive a redox (viologen) molecule of a junction under electrochemical scanning tunneling microscopy (EC-STM) platform between almost perfect oxidized and reduced states. Because changes in vibrational properties (frequencies and Raman intensities) associated with the change in the average redox state are substantial, we suggest and aim at stimulating concurrent transport-SERS (surface-enhanced Raman scattering) studies in three-terminal EC-STM setup as a possible method of experimental investigation. The present results on the reduction (or oxidation) efficiency reveal significant advantages of the three-terminal EC-STM platform compared to “dry”´ two- or three-terminal platforms (e.g. electromigrated junctions).