When Dihedral Angles Mask Denticity in Molecular Conductance

Area of Science:

• Molecular Electronics
• Quantum Transport
• Surface Science

Background:

• Stronger molecule-electrode coupling is generally linked to higher conductance in single-molecule junctions.
• It is widely assumed that increased molecular coordination (denticity) enhances junction conductance.

Purpose of the Study:

• To investigate the relationship between denticity and conductance in single-molecule junctions.
• To determine if higher denticity inherently leads to higher conductance.
• To explore the influence of other factors, such as dihedral angles, on conductance.

Main Methods:

• Utilized density functional theory (DFT) and the nonequilibrium Green's function (NEGF) technique for theoretical simulations.
• Employed mechanically controlled break-junction (MCBJ) experiments for empirical validation.
• Studied a single N-heterohexacene molecule with tetradentate ethyl sulfide anchors to vary effective denticity within one construct.

Main Results:

• Contrary to expectations, increasing denticity did not result in higher conductance.
• A strong correlation was observed between conductance and the dihedral angle between the electrode and the molecular core.
• Simulated and experimental results showed that dihedral angles have a greater impact on conductance than denticity alone.
• Different denticities merged into a single conductance feature, making them indistinguishable by conductance.

Conclusions:

• Denticity alone is insufficient for designing highly conductive molecular junctions.
• The influence of dihedral angles on conductance can dominate over denticity effects.
• Assumptions linking specific conductance features to denticity require careful re-evaluation.
• Molecular design should consider the interplay between dihedral angles and denticity for optimizing conductance.