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Pseudo-Jahn-Teller Distortion in a One-Dimensional π-Conjugated Polymer
Ziyi Wang1,2,3, Boyu Qie3,4,5, Weichen Tang1,2
1Department of Physics, University of California, Berkeley, California 94720, United States.
Journal of the American Chemical Society
|February 14, 2026
Summary
One-dimensional conjugated polymers exhibit spontaneous symmetry breaking due to out-of-plane distortions. This structural change, driven by electron-lattice coupling, influences electronic properties by increasing the band gap.
Area of Science:
- Materials Science
- Organic Electronics
- Solid-State Physics
Background:
- Structural distortions in low-dimensional π-conjugated systems significantly impact electronic properties.
- Controlling these distortions in extended systems is a persistent challenge.
Purpose of the Study:
- To investigate spontaneous symmetry breaking (SSB) in a one-dimensional conjugated polymer, poly(difluorenoheptalene-ethynylene) (PDFHE).
- To understand the structural and electronic consequences of this distortion.
Main Methods:
- Synthesis of PDFHE on noble metal surfaces.
- Characterization using low-temperature scanning tunneling microscopy (STM).
- Density functional theory (DFT) calculations.
Main Results:
- PDFHE adopts nonplanar isomers instead of a planar conformation.
- A pseudo-Jahn-Teller (PJT) distortion with mirror-odd out-of-plane character stabilizes these isomers.
- The distortion lowers energy and increases the band gap, confirming SSB.
Conclusions:
- Subtle electron-lattice coupling can induce significant structural rearrangements in extended π-systems.
- SSB driven by PJT distortion provides a mechanism for tuning electronic properties in conjugated polymers.
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