Gated off-site radical injection: Bidirectional conductance modulation in single-molecule junctions

Area of Science:

• Molecular electronics
• Organic chemistry
• Surface science

Background:

• Understanding radical effects on molecular conductance is crucial for molecular electronics.
• Single-molecule junctions offer a platform to study conductance changes at the molecular level.

Purpose of the Study:

• To investigate the impact of radical injection on the electrical conductance of organic molecules.
• To explore how different conjugation pathways (linear vs. cross-conjugated) affect conductance modulation by radicals.

Main Methods:

• Synthesis of two families of cyclopentadienone derivatives with distinct radical path geometries (linear FCF and cross-conjugated PCP).
• Utilizing scanning tunneling microscope break junction technique to form single-molecule junctions.
• Measuring electrical conductance upon electronic injection from off-site neutral radicals.

Main Results:

• Radical injection into PCP systems unexpectedly decreased conductance compared to closed-shell analogs.
• Radical injection into FCF systems increased conductance.
• Identified through-bond and through-space conductance mechanisms in FCF and PCP series, respectively.

Conclusions:

• Off-site radical injection can effectively modulate molecular conductance in single-molecule junctions.
• The geometry of conjugation pathways significantly influences the conductance response to radical injection.
• This approach provides a novel strategy for designing molecular electronic devices with tunable electrical properties.