Single Molecular Conductance of Tolanes: Experimental and Theoretical Study on the Junction Evolution Dependent on the Anchoring Group

Abstract

Employing a scanning tunneling microscopy based beak junction technique and mechanically controlled break junction experiments, we investigated tolane (diphenylacetylene)-type single molecular junctions having four different anchoring groups (SH, pyridyl (PY), NH(2), and CN) at a solid/liquid interface. The combination of current-distance and current-voltage measurements and their quantitative statistical analysis revealed the following sequence for junction formation probability and stability: PY > SH > NH(2) > CN. For all single molecular junctions investigated, we observed the evolution through multiple junction configurations, with a particularly well-defined binding geometry for PY. The comparison of density functional theory type model calculations and molecular dynamics simulations with the experimental results revealed structure and mechanistic details of the evolution of the different types of (single) molecular junctions upon stretching quantitatively.

Gating of Quantum Interference in Molecular Junctions by Heteroatom Substitution

“…The most probable stretched distance Δ z * is determined from the plateau distribution histograms to be 0.8 nm ( R2 ), 0.7 nm ( R1 ) and 0.6 nm ( R3 ), respectively. As a results, the most probable absolute distance z * ( z *=Δ z * + 0.5 nm)9c between two gold tips is 1.3 nm for R2 , 1.2 nm for R1 and 1.1 nm for R3 , which agrees well with theoretically determined junction lengths (1.16 nm for R2 1.09 nm for R1 and 0.96 nm for R3 , Table S3). It can therefore be deduced that the distinct variations in conductance values of M1 – M3 and R1 – R3 are attributed to the different electronic transport pathways whereby the former molecules are trapped between two Au leads via the Au−S bonds while the latter ones are connected on the one side via the Au−S bonds, on the other side via the Au−N bonds.…”

Electrochemical Control of Single-Molecule Conductance by Fermi-Level Tuning and Conjugation Switching

“…17,[34][35][36] Figure 1b The small spike at log (G/G 0 ) ≈ -2.2 in panels e and f represents an artefact related to the switching of the amplifier. 37 Figure 1c shows typical conductance-distance traces of AQ-1,5 in the reduced and oxidized states obtained from the STM-BJ experiment. 37,38 For both redox states, the conductance curves exhibit a short plateau at 1 G 0 due to atomic gold point contacts existing just before rupture.…”

“…37 Figure 1c shows typical conductance-distance traces of AQ-1,5 in the reduced and oxidized states obtained from the STM-BJ experiment. 37,38 For both redox states, the conductance curves exhibit a short plateau at 1 G 0 due to atomic gold point contacts existing just before rupture. In addition to the 1 G 0 plateau, the blue curves show a more extended plateau with conductances ranging from 10 -4.6 G 0 to 10 -5.4 G 0 which can be assigned to the conductance of the reduced AQ-1,5 single-molecule junctions.…”

Single-Molecule Electrochemical Transistor Utilizing a Nickel-Pyridyl Spinterface

“…7 Au-pyridyl contacts, such as the Au-44BP bond, have been shown to provide reproducible junctions for which two conductance values can be distinguished due to different binding geometries. [8][9][10] However, despite significant progress investigating different chemical linker groups 9,[11][12][13][14][15][16][17][18] there have been few previous attempts to broaden the range of metal electrodes studied.…”