High electronic couplings of single mesitylene molecular junctions

Area of Science:

• Molecular electronics
• Quantum transport phenomena
• Nanoscale science and technology

Background:

• Understanding charge transport in single molecules is crucial for developing molecular electronic devices.
• Mesitylene (1,3,5-trimethylbenzene) is a model aromatic molecule for studying charge transport.
• Molecular junctions formed with gold electrodes are common platforms for such studies.

Purpose of the Study:

• To experimentally investigate the charge transport properties of single mesitylene molecular junctions.
• To determine the electronic coupling and structural configurations influencing conductance.
• To correlate conductance states with molecular junction geometry.

Main Methods:

• Utilizing a scanning tunneling microscopy-based break-junction technique at room temperature.
• Measuring electronic conductance and current-voltage (I-V) characteristics of mesitylene/Au junctions.
• Performing statistical analysis of I-V data and fitting to a single-channel resonant tunneling model.

Main Results:

• Observed two distinct conductance states for mesitylene molecular junctions: ~10⁻¹ G₀ and >10⁻³ G₀ (G₀ = 2e²/h).
• Determined significant electronic couplings (up to ~0.15 eV) responsible for high conductance, attributed to direct π-bonding.
• Proposed two structural models based on junction stretch length and electronic coupling analysis: perpendicular binding or tilted orientation.

Conclusions:

• The charge transport in single mesitylene junctions is highly dependent on electronic coupling and molecular orientation.
• Direct π-bonding facilitates high conductance, suggesting favorable electronic coupling pathways.
• The findings provide insights into the structure-property relationships governing charge transport in molecular junctions.