Radical-Enhanced Charge Transport in Single-Molecule Phenothiazine Electrical Junctions

Area of Science:

• Molecular electronics
• Materials science
• Quantum chemistry

Background:

• Single-molecule electronics offers precise control over charge transport.
• Phenothiazine (PTZ) derivatives are promising organic molecules for electronic applications.
• Understanding radical states is crucial for molecular device functionality.

Purpose of the Study:

• To investigate the single-molecule conductance of phenothiazine-based radical junctions.
• To quantify the conductance change between neutral and radical states of PTZ.
• To explore the stability and formation probability of PTZ radical junctions.

Main Methods:

• Mechanically controllable break junction (MCBJ) technique for single-molecule measurements.
• Acid oxidant triggering to form PTZ radical species.
• Density Functional Theory (DFT) calculations for theoretical analysis.

Main Results:

• A significant enhancement of electrical conductance (up to 200 times) was observed in the PTZ radical state compared to the neutral state.
• The PTZ radical junctions exhibited high stability, persisting for at least two months.
• High junction formation probability at room temperature was achieved.
• Theoretical studies indicated that the conductance increase is attributed to a reduced HOMO-LUMO gap and enhanced transmission near the HOMO orbital in the radical state.

Conclusions:

• The formation of stable PTZ radicals dramatically enhances single-molecule conductance.
• This finding demonstrates the potential of PTZ radicals for advanced molecular electronics and spintronics.
• The study provides a foundation for designing novel molecular electronic components.