Hydroxyl Group as the 'Bridge' to Enhance the Single-Molecule Conductance by Hyperconjugation

Area of Science:

• Molecular Electronics
• Organic Chemistry

Background:

• Hyperconjugated molecules with sigma-pi (σ-π) interactions are ideal for single-molecule devices requiring conjugation and flexibility.
• Investigating single-molecule conductance in hyperconjugation systems is underexplored, lacking established construction strategies and electron transport mechanisms.

Purpose of the Study:

• To develop a rational approach for constructing hyperconjugation molecules.
• To investigate the mechanism of electron transport in these systems and its effect on conductance.

Main Methods:

• A skipped-conjugated molecular structure was utilized.
• A hydroxyl group was incorporated as a bridging element between conjugated fragments.
• Single-molecule conductance measurements were performed.
• Theoretical studies were conducted to elucidate the electron transport mechanism.

Main Results:

• A novel hyperconjugation molecule was successfully constructed using a bridging hydroxyl group.
• The hyperconjugation system with the hydroxyl group exhibited a two-fold increase in conductance compared to hydroxyl-free analogs.
• Theoretical analysis confirmed that the hydroxyl group facilitates electron transport by connecting the lowest unoccupied molecular orbitals (LUMOs) of conjugated fragments.

Conclusions:

• A viable strategy for building hyperconjugation systems for molecular electronics was established.
• The bridging hydroxyl group acts as a through-space channel, significantly enhancing single-molecule conductance.
• This finding opens new avenues for designing advanced single-molecule electronic devices.