DOE OSTI · 3022598
Pseudo–Jahn–Teller Distortion in a One-Dimensional π-Conjugated Polymer
Abstract
Structural distortions in low-dimensional π-conjugated systems profoundly influence their electronic properties, but the control of such behavior in laterally extended systems remains challenging. Here, in this study, we demonstrate that a one-dimensional conjugated polymer─ poly -(difluorenoheptalene-ethynylene) (PDFHE)─undergoes a pronounced out-of-plane backbone distortion, equivalent to a spontaneous symmetry breaking (SSB) of its mirror symmetry. We synthesized PDFHE on noble metal surfaces and characterized its structure and electronic states using low-temperature scanning tunneling microscopy (STM). Rather than adopting a planar, high-symmetry conformation, PDFHE relaxes into nonplanar isomers stabilized by a pseudo–Jahn–Teller (PJT) distortion having mirror-odd out-of-plane character. The distortion lowers the total energy and increases the band gap, providing a concise rationale for the observed symmetry breaking. Density functional theory calculations corroborate these findings, providing a microscopic explanation for the SSB. Our results show that even in mechanically robust extended π-systems, subtle electron–lattice coupling can spontaneously drive significant structural rearrangements, even in mechanically robust extended π-systems.
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Wang, Ziyi [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Kavli Energy NanoScience Institute, Berkeley, CA (United States)] (ORCID:0000000310495038), Qie, Boyu [University of California, Berkeley, CA (United States); Kavli Energy NanoScience Institute, Berkeley, CA (United States)] (ORCID:0000000335527366), Tang, Weichen [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000219455369), Jiang, Jingwei [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000209494401), Liu, Fujia [University of California, Berkeley, CA (United States)] (ORCID:0009000582424281), Jacobse, Peter H. [University of California, Berkeley, CA (United States)], Lu, Jiaming [University of California, Berkeley, CA (United States)], Li, Xinheng [University of California, Berkeley, CA (United States)], Louie, Steven G. [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000306220170), Fischer, Felix R. [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Kavli Energy NanoScience Institute, Berkeley, CA (United States)] (ORCID:0000000347233111), Crommie, Michael F. [University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Kavli Energy NanoScience Institute, Berkeley, CA (United States)] (ORCID:0000000182463444). 2026-02-14. Pseudo–Jahn–Teller Distortion in a One-Dimensional π-Conjugated Polymer. https://doi.org/10.1021/jacs.5c21950
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