Regulating the orientation of a single coordinate bond by the synergistic action of mechanical forces and electric field

Abstract

The conductance of molecular dynamic break junctions decreases upon an increased bias voltage. In contrast, the conductance of molecular fixed junctions increases upon an increased bias.

Conductance Evolution of Photoisomeric Single-Molecule Junctions under Ultraviolet Irradiation and Mechanical Stretching

“…Particularly, the histogram of the original M2 molecular junctions exhibits a high and a low conductance (denoted as HC and LC) peak; see Figure a. The observation of HC and LC can be attributed to distinct contact geometries: the HC plateau is assigned to a tilted bonding geometry where both the π-system of the pyridyl ring and the N atom are strongly coupled to the electrodes, while the LC plateau is attributed to the absence of π coupling when the N–Au bond is perpendicular to the electrode surface. − However, the bonding geometry of the N–Au bond perpendicular to the electrode surface is sterically impossible for the molecule in cis conformation during the stretching process, which leads to the gradual disappearance of the LC plateau upon UV light irradiation; see Figure S10 for a detailed discussion. Here, we focus on the HC plateau to study the conductance evolution.…”

Evolution of Single-Molecule Electronic Interfaces

“…109 Xiang et al investigated the evolution of chemical bonds upon mechanical stretching and electrical field, providing an approach for characterizing and regulating the orientation of a single coordinate bond. 119 Second, the interaction between different anchoring groups and the electrode not only affects the binding configuration at the molecule−electrode interface (i.e., different interfacial couplings) but also directly influences the charge transport capacities at the molecule−electrode interface. In 2009, Venkataraman et al achieved reversible regulation of the high and low conductance states of 4,4′-bipyridine by precisely controlling the electrode spacing at the interface, where the high and low conductance states originated from two different coupling Γ configurations of the pyridine molecule at the interface with the gold electrode.…”

“…Moreover, we can regulate molecule–electrode contact stability by changing the solvent interface environment . Xiang et al investigated the evolution of chemical bonds upon mechanical stretching and electrical field, providing an approach for characterizing and regulating the orientation of a single coordinate bond …”

Regulation of π–π interactions between single aromatic molecules by bias voltage

“…We utilized the scanning tunnelling microscope break junction (STM-BJ) technique to investigate the effect of electric fields on p-p interactions due to its advantages: it can generate a substantial electric field up to 10 9 V m À1 by applying a small a Center of Single-Molecule Sciences, Institute of Modern Optics, Tianjin Key voltage between the source and drain electrodes; 25 (2) the size of the electrode gap can be flexibly adjusted to form thousands of molecular junctions, and thus the statistical conductance of these junctions can be measured, offering a practical approach to characterize the p-p interactions between neighbouring molecules. 26,27 The experiments were conducted in a solution containing 0.1 mM of the target molecule at room temperature and atmospheric conditions.…”