Exploring antiaromaticity in single-molecule junctions formed from biphenylene derivatives

Area of Science:

• Molecular electronics
• Organic electronics
• Charge transport

Background:

• Oligophenylene-ethynylenes (OPEs) are crucial for molecular electronics.
• Understanding charge transport through different molecular cores is key to designing molecular junctions.

Purpose of the Study:

• To synthesize OPE derivatives with biphenylene cores.
• To investigate the impact of biphenylene antiaromaticity on charge transport.
• To compare conductance through biphenylene cores with other aromatic and antiaromatic systems.

Main Methods:

• Synthesis of OPE derivatives with varied core units (biphenylene, naphthalene, anthracene, fluorene, biphenyl).
• Single-molecule conductance measurements using the mechanically controllable break junction (MCBJ) technique.
• Analysis of charge transport pathways through different molecular cores.

Main Results:

• Electrical conductance was largely independent of pendant π-systems when transport occurred via phenylene rings.
• Antiaromaticity of the biphenylene core showed minimal impact on conductance compared to fluorene or biphenyl analogues.
• Transport through the biphenylene core was sensitive to its unique single bonds, yet differences in conductance were negligible.

Conclusions:

• The antiaromaticity of biphenylene does not significantly alter charge transport in these molecular junctions.
• Molecular core structure offers a unique way to tune conductance, unlike artificial quantum dots.
• Quantum effects govern electron transport in molecular junctions even at room temperature.