The effect of nitrogen lone-pair interaction on the conduction in a single-molecule junction with amine-Au bonding

Abstract

We have applied our previously developed three-dimensional dynamic probe method to analyze the conductance in a Au-/1,4-benzenediamine (BDA)/Au single molecule junction. This structure is a typically used example to demonstrate the high performance of the break junction (BJ) method for measuring conductance with small variations, however, details of the interaction of the nitrogen (N) lone-pair in the amine group with a Au electrode, which is considered to have a fundamental role in determining the conductance of the single molecule junction with the amine, have not yet been clarified and still remain an important issue to be resolved. In this study, we have succeeded, for the first time, in observing the site-dependent change in conductance of this system while the molecular conformation was accurately controlled, and the results were well reproduced by a simulation taking account of the effect of the N lone-pair in an amine bonding with a Au electrode.

Mechanistic Insight into Formate Production via CO2 Reduction in C–C Coupled Carbon Nanotube Molecular Junctions

“…Although the density functional theory (DFT)-based calculations showed variation in the density of states (DOS) of CNTs when coupled through C 6 H 4 , a direct experimental proof was lacking. Scanning tunneling microscopy/spectroscopy (STM/S) can probe the local DOS (LDOS) of a molecular junction, − and the modification in the electronic band structure of CNTs can be studied. Further, such a molecular junction will also be useful in developing molecular circuitries, which are highly important in molecular electronics and spintronic devices. − …”

Development of Classical Force Fields for Interfaces between Single Molecules and Au

“…The molecule, through its chemical linker groups, binds to one of these undercoordinated Au adatoms in the trimer motif. Such unit cells are interface geometries are typical of single-molecule junction structure simulations. ,− In all classical and DFT simulations, the position of Au layers was kept fixed, while molecular atoms and Au trimer atoms were allowed to move. We performed simulations using both the semiempirical force field developed, as well as DFT.…”

Effect of Contact Geometry on Spin Transport in Amine-Ended Single-Molecule Magnetic Junctions

“…To reach the ultimate goal of maximizing the efficiency in electronic devices, − single-molecule junctions (SMJs) have attracted intensive attention due to their diversity and flexibility, and have been successfully fabricated by the scanning tunneling microscopy breaking junction process, , the mechanically controllable breaking junction process, and the self-assembled monolayer fabrication. , SMJs consist of three distinct components: the electrode, linker, and central molecule; the linker group (also known as the anchor group or contact group) connects the central molecule to the electrodes, and the linker typically binds to the electrode, that is, the most used Au electrode, either through the dative interaction or via the covalent bonding. Based on Pearson’s principle of hard and soft acids and bases, the weaker coupling between the soft metal (Au) and hard base (N) provides the dative contact involving a lone pair donors of the H-non-dissociated amine linker selectively binding to the undercoordinated Au adatom, − which may limit the contact geometry and narrows the charge-transfer channels. In contrast, the thiol linker is one of the most appropriate candidates for charge transport in SMJs due to its excellent interfacial coupling and ductility.…”