Signatures of Conformational Dynamics and Electrode-Molecule Interactions in the Conductance Profile During Pulling of Single-Molecule Junctions

Abstract

We demonstrate that conductance can act as a sensitive probe of conformational dynamics and electrode-molecule interactions during the equilibrium and nonequilibrium pulling of molecular junctions. To do so, we use a combination of classical molecular dynamics simulations and Landauer electron transport computations to investigate the conductance of a family of Au-alkanedithiol-Au junctions as they are mechanically elongated. The simulations show an overall decay of the conductance during pulling that is due to a decrease in the through-space electrode-molecule interactions, and that sensitivity depends on the electrode geometry. In addition, characteristic kinks induced by level alignment shifts (and to a lesser extent by quantum destructive interference) were also observed superimposed to the overall decay during pulling simulations. The latter effect depends on the variation of the molecular dihedral angles during pulling and therefore offers an efficient solution to experimentally monitor conformational dynamics at the single-molecule limit.

Inside Back Cover: Hemilabile Ligands as Mechanosensitive Electrode Contacts for Molecular Electronics (Angew. Chem. Int. Ed. 46/2019)

“…Well-defined conductance variations are also found for 4 ( Figure 3b), although this longer molecule also shows as maller modulation than 1.T he overall results confirm that the labile behaviour of the thienyl moiety is indeed responsible for the observed behaviour,w ith 1 being the compound providing the largest conductance variation upon modulation of the electrode position as evidenced by analysing the modulation profile (Figure 3c). Thef act that both conformationally locked molecules 1 and 2,a nd conformationally flexible molecule 4 show significant modulation in conductance upon junction compression supports the notion that an explanation for the conductance switching based on possible different conformers [40] of oligothiophenes [36] like 4 is not reasonable here.…”

Force–conductance spectroscopy of a single-molecule reaction

“…These results illustrate the power of force–conductance measurements as a general platform for the development of highly discriminating multidimensional single-molecule spectroscopies,44,46 and represent new frontiers in the control of chemical processes at the single-molecule limit.…”

“…A complementary observable to force that can be implemented in the same experimental setup is conductance 44–46. Conductance signals changes in the transport-determining molecular electronic energy levels.…”

Simultaneous Suppression of pi- and sigma- Transmission in pi-Conjugated Molecules

“…41 Therefore, the interference effect is clearest in the single-molecule conductance of saturated silanes that are generally permethylated, though it is also significant in alkanes. [41][42][43][44][45] By considering trans-alkanes the archetypical s-conductor and gauche-alkanes the archetypical s-insulator, we deduce from Scheme 1 that the structural requirements for pand s-interference appear to be mutually exclusive. The s-path through metabenzene is structurally akin to that of the trans-alkane, and the s-path of para-benzene to that of the gauche-alkane.…”