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Thermodynamic and Kinetic Control of π-Stacked Dimer Conductance in Single-Molecule Junctions
Xin Liu1, Yin Zhao1, Chenming Li1
1Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, 200237, P. R. China.
The Journal of Physical Chemistry Letters
|June 24, 2026
Summary
Thermodynamically stable π-dimers, crucial for molecular electronics, exhibit distinct charge transport properties compared to transient dimers. This study reveals their enhanced conductance and superior π-orbital overlap, guiding future molecular design.
Area of Science:
- Molecular and supramolecular electronics
- Charge transport mechanisms
- Organic semiconductor physics
Background:
- π-stacked dimers significantly influence charge transport in molecular electronics.
- Research has primarily focused on transient, kinetically trapped dimers.
- Thermodynamically stable π-dimers are less understood but vital for advancing the field.
Purpose of the Study:
- To investigate and differentiate the charge transport characteristics of kinetically trapped versus thermodynamically stable π-dimers.
- To explore the role of molecular architecture in dictating dimer formation and electronic properties.
- To provide design principles for controlling charge transport through aggregation in supramolecular systems.
Main Methods:
- Utilized donor-acceptor-donor diketopyrrolopyrrole molecular wires.
- Employed scanning tunneling microscope break-junction measurements and flicker-noise analysis.
- Integrated concentration-dependent UV-vis spectroscopy and DFT-NEGF calculations.
Main Results:
- DPP-1Th predominantly formed monomeric junctions with a low-conductance kinetically generated π-dimer at 1.0 mM.
- DPP-3Th showed preassembly into thermodynamically stable π-dimers above 0.5 mM.
- The thermodynamically stable DPP-3Th dimer exhibited enhanced conductance and longer junction displacement compared to the DPP-1Th dimer.
Conclusions:
- Thermodynamically stable π-dimers possess distinct and potentially superior charge transport capabilities compared to kinetically generated dimers.
- Molecular preorganization significantly impacts π-orbital overlap and charge transport efficiency.
- This research clarifies ambiguities in supramolecular junction analysis and offers design strategies for aggregation-controlled electronic components.
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