@article{Qiu2026, 
author = {Shengzhe Qiu and Ningyue Chen and Zhenghao Wang and Jin-liang Lin and Yu Xie and Dezhuang Ji and Ziming Zhou and Sitong Liu and Wenkun Lv and Yuan Li},
title = {Halogen substitution with subtle effects on the electronic structure of fully conjugated molecular junctions},
year = {2026},
journal = {Nano Research},
volume = {19},
number = {4},
pages = {94908462},
keywords = {self-assembled monolayers, halogen substitution, conjugated molecules, molecular tunneling junctions, π-backbone pinning effect},
url = {https://www.sciopen.com/article/10.26599/NR.2026.94908462},
doi = {10.26599/NR.2026.94908462},
abstract = {Halogen atoms possess distinct atomic polarizabilities and have been recently employed in molecular junctions composed of saturated alkanethiol to greatly enhancing tunneling currents, dielectric responses, and plasmonic properties. However, their influence in fully conjugated molecular systems remains insufficiently understood. Here, a series of conjugated molecules, HSCH2TPDA-X (X = H, F, Cl, Br, I), based on the fully conjugated triphenyldiacetylene (TPDA, C6H4C≡CC6H4C≡CC6H4) backbone were designed, and Metal (Ag/Au)-SAMs//Eutectic gallium-indium alloy (EGaIn) molecular junctions were constructed to systematically investigate how halogen substitution affects charge transport in conjugated systems. The J–V characteristics of the HSCH2TPDA-X molecules remain stable over the measured temperature range, exhibiting temperature-independent behavior that indicates a tunneling-dominated charge transport mechanism. Single-level model (SLM) fitting reveals that halogen substitution (X = H, F, Cl, Br, I) does not significantly alter the highest occupied molecular orbital (HOMO)–Fermi level alignment, while the coupling strength is positively correlated with the current density. Density-functional theory (DFT) density-of-states (DOS) analysis reveals that, despite local terminal orbital shifts induced by halogen substitution, the overall DOS of the metal–self-assembled monolayer (SAM) closely follows that of the TPDA π-backbone, indicating a π-conjugated backbone pinning effect that constrains halogen-induced perturbations. These results contrast with previous saturated systems and indicate an observation of strong π-backbone pinning effect in conjugated system.}
}