Tip‐Induced Inversion of the Chirality of a Molecule's Adsorption Potential Probed by the Switching Directionality

Abstract

The switching behavior of surface‐supported molecular units excited by current, light, or mechanical forces is determined by the shape of the adsorption potential. The ability to tailor the energy landscape in which a molecule resides at a surface gives the possibility of imposing a desired response, which is of paramount importance for the realization of molecular electronic units. Here, by means of scanning tunneling microscopy, a triazatruxene (TAT) molecule on Ag(111) is studied, which shows a switching behavior characterized by transitions of the molecule between three states, and which is attributed to three energetically degenerate bonding configurations. Upon tunneling current injection, the system can be excited and continuously driven, showing a switching directionality close to 100%. Two surface enantiomers of TAT show opposite switching directions pointing at the chirality of the energy landscape of the adsorption potential as a key ingredient for directional switching. Further, it is shown that by tuning the tunneling parameters, the symmetry of the adsorption potential can be controllably adjusted, leading to a suppression of the directionality or an inversion of the switching direction. The findings represent a molecule‐surface model system exhibiting unprecedented control of the shape of its adsorption potential.

Ferrocenyl-Substituted Triazatruxenes: Synthesis, Electronic Properties, and the Impact of Ferrocenyl Residues on Directional On-Surface Switching on Ag(111)

“…We have recently shown that N , N ′, N ″-triethyltriazatruxene ( Et TAT , Figure , R = Et) serves as a programmable molecular switch when deposited on Ag(111) . Binding to the substrate results in two degenerate, enantiomeric configurations, R (clockwise rotation for the symmetry equivalent transformations) and S (counterclockwise rotation for symmetry equivalent transformations).…”

“…The reversible and directional switching in either a clockwise ( R surface enantiomer) or counterclockwise ( S enantiomer) direction between these three states was achieved by placing the tip of a scanning tunneling microscope (STM) in a lateral position above a TAT molecule and adjusting the tunneling current and bias voltage. The switching relies on a rocking motion of the Et TAT molecules in a ratchet-like potential yet not on a rotational motion . Hence, the TAT molecules on Ag(111) constitute three-state, trinary-digit (trit) units for on-surface information storage.…”

“…The TAT core is readily recognized by the characteristic 3-fold symmetric molecular backbone surrounded by the three distinct circular-shaped maxima, which are associated with the N-bonded ethyl groups.Close inspection of the images in Figure8a−c shows the depletion areas resulting from charge redistribution between the TAT molecule and the substrate at only two of the three maxima. This particular pattern originates from a tilting of the TATs and the local differences in the N−Ag bond lengths, which are themselves due to a slight mismatch between the positions of the TAT N atoms and the Ag atoms of the substrate 42. Taking into account the 3-fold symmetry of the TAT core, three bonding configurations within the same adsorption geometry exist, depending on which the N atom is further lifted from the underlying Ag atoms.…”

“…300 pm at 1.8 V (see FigureS64), which agrees with the results of STM measurements on other surfaceconfined ferrocenes.96−98 As presented in Figures 8d−f, S59, and S60, increasing the bias voltage and the current induces switching between the three adsorption configurations of the TAT core unit, as discussed above. The changes in the tilting of the entire molecule during this process lead to fluctuations of the tunneling conductance and accordingly to variations of the zposition of the STM scanner 42. Configurational on-surface switching is then visible in the tunneling current images as noise clouds localized at the positions of the amine N atoms and ethyl side arms as they move closer toward or further away from the substrate.…”

Local Chiral Inversion of Thymine Dimers by Manipulating Single Water Molecules

“…However, no local information on the interactions between water and organic molecules could be obtained. Thus, it is generally intriguing to manipulate each single water molecule in a water-involved structure in situ to detect local intermolecular interactions. − …”