Enhanced charge transport via d(δ)-p(π) conjugation in Mo₂-integrated single-molecule junctions

Area of Science:

• Inorganic Chemistry
• Materials Science
• Molecular Electronics

Background:

• Single-molecule electronics aims to miniaturize devices using individual molecules.
• Organic π-conjugated molecules have shown promise but often exhibit limited conductance.
• Metal-containing molecular wires offer potential for enhanced charge transport properties.

Purpose of the Study:

• To synthesize and characterize novel trans-dimolybdenum (Mo2) complexes with pyridyl anchors.
• To investigate the single-molecule charge transport properties of these Mo2 complexes.
• To compare the conductance of Mo2 complexes with their organic analogues and understand structure-property relationships.

Main Methods:

• Crystallographic characterization of synthesized Mo2 complexes (m-Mo2 and p-Mo2).
• Scanning Tunneling Microscopy Break Junction (STM-BJ) technique for single-molecule conductance measurements.
• Density Functional Theory (DFT)-based transmission calculations to elucidate electronic structure.

Main Results:

• Synthesized and structurally characterized trans-dimolybdenum nicotinate (m-Mo2) and its isomer (p-Mo2).
• Mo2 complexes demonstrated over an order of magnitude higher single-molecule conductance compared to organic analogues (p-Ph, m-Ph).
• The meta-connected m-Mo2 complex exhibited higher conductance than the para-connected p-Mo2 complex, contrary to organic analogues.
• DFT calculations revealed a reduced HOMO-LUMO gap and d(δ)-p(π) conjugation as key factors for high conductance.

Conclusions:

• Quadruply bonded Mo2 units significantly enhance single-molecule conductance.
• The connectivity of pyridyl anchors (meta vs. para) influences conductance in Mo2 complexes.
• The delocalized electronic structure arising from Mo2-pyridine conjugation is crucial for achieving high molecular conductivity.