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Formation and Evolution of Metallocene Single-Molecule Circuits with Direct Gold-π Links
Brent Lawson1, Percy Zahl2, Mark S Hybertsen2
1Department of Physics, Boston University, Boston, Massachusetts 02215, United States.
Journal of the American Chemical Society
|March 30, 2022
Summary
Group 8 metallocenes form direct gold-π bonds in single-molecule circuits, enabling stable molecular junctions. Conductance is independent of electrode sharpness, revealing distinct binding mechanisms for molecular electronics.
Area of Science:
- Molecular electronics
- Nanotechnology
- Physical chemistry
Background:
- Single-molecule circuits are crucial for advancing molecular electronics.
- Understanding electrode-molecule interactions is key to controlling junction properties.
- Metallocenes offer unique electronic properties for molecular wire applications.
Purpose of the Study:
- Investigate direct gold-π binding in metallocene-based single-molecule circuits.
- Characterize the effect of this binding on molecular conductance and junction evolution.
- Elucidate the atomic-scale mechanisms of metallocene-gold electrode interactions.
Main Methods:
- Scanning tunneling microscope-based break junction (STMBJ) measurements at cryogenic and room temperatures.
- Analysis of molecular plateau persistence during junction extension and compression.
- Density functional theory (DFT)-based calculations for modeling electrode-molecule interfaces.
Main Results:
- Direct gold-π binding formed stable single-molecule circuits with group 8 metallocenes without linkers.
- Junction persistence correlated with electrode tip geometry (sharp vs. blunt).
- Two distinct binding modes identified: donor-acceptor bonds on sharp tips and van der Waals interactions on blunt tips.
- Molecular conductance was largely independent of electrode atomic structure.
- Non-specific interactions led to extended conductance plateaus.
Conclusions:
- Direct gold-π interactions enable robust metallocene single-molecule junctions.
- Electrode geometry influences binding modes but not significantly conductance.
- Metallocene-based circuits offer a distinct mechanism for stable molecular wires compared to traditional rod-shaped molecules.
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