Not So Innocent After All: Interfacial Chemistry Determines Charge‐Transport Efficiency in Single‐Molecule Junctions

Daaoub, Abdalghani; Morris, James M F; Béland, Vanessa A.; Demay‐Drouhard, Paul; Hussein, Amaar; Higgins, Simon J.; Sadeghi, Hatef; Nichols, Richard J.; Vezzoli, Andrea; Baumgartner, Thomas; Sangtarash, Sara

doi:10.1002/anie.202302150

Cited by 12 publications

(9 citation statements)

References 64 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is found via the simulation of the electrostatic potential (ESP) distribution that the charge distribution changed dramatically around the molecules, i.e., the charge density on the molecular backbone increases upon the trans → cis transition, see Figure S24. The electron-rich amine anchoring group of M1 can act as an electron reservoir and provides electrons to increase the charge density around the molecular backbone, and thus supports the conformational change. However, this reservoir effect is absent for M2 and M3 molecular junctions with the electron-deficient pyridyl-anchoring group, which cannot supply additional electrons.…”

Section: Resultsmentioning

confidence: 99%

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

Tan,

Sun,

Zhao

et al. 2024

J. Am. Chem. Soc.

View full text Add to dashboard Cite

A comprehensive understanding of carrier transport in photoisomeric molecular junctions is crucial for the rational design and delicate fabrication of single-molecule functional devices. It has been widely recognized that the conductance of azobenzene (a class of photoisomeric molecules) based molecular junctions is mainly determined by photoinduced conformational changes. In this study, it is demonstrated that the most probable conductance of amine-anchored azobenzene-based molecular junctions increases continuously upon UV irradiation. In contrast, the conductance of pyridyl-anchored molecular junctions with an identical azobenzene core exhibits a contrasting trend, highlighting the pivotal role that anchoring groups play, potentially overriding (even reversing) the effects of photoinduced conformational changes. It is further demonstrated that the molecule with cisconformation cannot be fully mechanically stretched into the transconformation, clarifying that it is a great challenge to realize a reversible molecular switch by purely mechanical operation. Additionally, it is revealed that the coupling strength of pyridyl-anchored molecules is dramatically weakened when the UV irradiation time is prolonged, whereas it is not observed for amine-anchored molecules. The mechanisms for these observations are elucidated with the assistance of density functional theory calculations and UV−Vis spectra combined with flicker noise measurements which confirm the photoinduced conformational changes, providing insight into understanding the charge transport in photoisomeric molecular junctions and offering a routine for logical designing synchro opto-mechanical molecular switches.

show abstract

Section: Resultsmentioning

confidence: 99%

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

Tan,

Sun,

Zhao

et al. 2024

J. Am. Chem. Soc.

View full text Add to dashboard Cite

show abstract

“…The conductance of a molecule in a break junction is determined by the coupling strength and energy-level alignment of the frontier orbitals with the Fermi energy of the metal electrodes. , The coupling strength and the Fermi level alignment, in turn, are heavily influenced by the anchoring species. ,− Hence, to probe the Au–S interactions, we first performed single-molecule conductance measurements.…”

Section: Results and Discussionmentioning

confidence: 99%

Chemistry of the Au–Thiol Interface through the Lens of Single-Molecule Flicker Noise Measurements

Rashid,

Bro-Jørgensen,

Harilal

et al. 2024

J. Am. Chem. Soc.

View full text Add to dashboard Cite

Chemistry of the Au−S interface at the nanoscale is one of the most complex systems to study, as the nature and strength of the Au−S bond change under different experimental conditions. In this study, using mechanically controlled break junction technique, we probed the conductance and analyzed Flicker noise for several aliphatic and aromatic thiol derivatives and thioethers. We demonstrate that Flicker noise can be used to unambiguously differentiate between stronger chemisorption (Au− SR) and weaker physisorption (Au−SRR′) type interactions. The Flicker noise measurements indicate that the gold rearrangement in chemisorbed Au−SR junctions resembles that of the Au rearrangement in pure Au−Au metal contact breaking, which is independent of the molecular backbone structure and the resulting conductance. In contrast, thioethers showed the formation of a weaker physisorbed Au−SRR′ type bond, and the Flicker noise measurement indicates the changes in the Au-anchoring group interface but not the Au−Au rearrangement like that in the Au−SR case. Additionally, by employing single-molecular conductance and Flicker noise analysis, we have probed the interfacial electric fieldcatalyzed ring-opening reaction of cyclic thioether under mild environmental conditions, which otherwise requires harsh chemical conditions for cleavage of the C−S bond. All of our conductance measurements are complemented by NEGF transport calculations. This study illustrates that the single-molecule conductance, together with the Flicker noise measurements can be used to tune and monitor chemical reactions at the single-molecule level.

show abstract

“…On the other hand, it has been shown that the electrical response of molecular systems has a very important dependence on the anchoring group and the coordination with the electrodes . This can cause variations of several orders of magnitude .…”

Section: Resultsmentioning

confidence: 99%

Charge Transport in Conjugated and Saturated Hydrocarbons: Comparing Ballistic and Cotunneling Contributions

Cabrera-Tinoco,

Moreira,

Borja-Castro

et al. 2023

J. Phys. Chem. A

View full text Add to dashboard Cite

The comparison between electrical transport in C n H 2 n +2 S 2 alkane and C n H n +2 S 2 alkene ( n = 4, 6, 8, 10) is studied by using a generalized Breit-Wigner approach and considering coherent transport mechanisms and eventual changes in the state of charge (i.e., cotunneling processes) for both molecules. In general, the conductance of alkanes tends to be smaller than that of similar-sized alkenes. However, cotunneling processes have an important participation in the overall transport in the case of alkanes but not for the alkene family. The progressive changes in both the eigenenergies of the relevant frontier molecular orbitals of the charged species and their spatial localization play decisive roles in the observed differences. While the molecular orbitals of the charged species of the conjugated molecules are hardly affected by the applied voltage, their saturated counterparts are quite sensitive to the external field. With this, successive avoided-crossing events between the molecular orbitals of the single-charged alkane molecules can lead to the appearance of nonballistic conduction channels that make no negligible contributions to the molecular transport.

show abstract

Not So Innocent After All: Interfacial Chemistry Determines Charge‐Transport Efficiency in Single‐Molecule Junctions

Cited by 12 publications

References 64 publications

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

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

Chemistry of the Au–Thiol Interface through the Lens of Single-Molecule Flicker Noise Measurements

Charge Transport in Conjugated and Saturated Hydrocarbons: Comparing Ballistic and Cotunneling Contributions

Contact Info

Product

Resources

About