Chem. J. Chinese Universities ›› 2025, Vol. 46 ›› Issue (2): 20240429.doi: 10.7503/cjcu20240429

• Organic Chemistry • Previous Articles     Next Articles

Influence of Polycyclic Aromatic Hydrocarbon Molecular Framework on Single-molecule Conductance

WANG Mingzhen, WANG Zhiye, LI Mengxiao, LU Yuhua, WANG Xu, LI Yunchuan()   

  1. State Key Laboratory of Refractories and Metallurgy,the Institute of Advanced Materials and Nanotechnology,Faculty of Materials,Wuhan University of Science and Technology,Wuhan 430081,China
  • Received:2024-09-16 Online:2025-02-10 Published:2024-11-25
  • Contact: LI Yunchuan E-mail:yc.l@wust.edu.cn

Abstract:

The charge transport process within molecular junctions is influenced by many factors, including the molecular backbones and anchoring groups. In this paper, to investigate the impact of the molecular backbone on the charge transport properties of molecular junctions, we designed and synthesized three kinds of polycyclic aromatic hydrocarbons(PAHs) with different fused-ring core(benzene, naphthalene and anthracene) as molecular skeleton and thiophene as anchor group. Scanning tunneling microscope break junction(STM-BJ) measurement and density functional theory(DFT) -based calculations were performed to investigate the charge transport process of single PAHs junctions. The STM experimental results of three molecules exhibit two distinct conductivity states, designated as high conductance states(GH) and low conductance states(GL), which correspond to the two binding configurations of Au-π and Au-S within single molecular junctions for three molecules. In the case of the GL state, the increase of fused-ring core effectively shifts the HOMO level closer to the Au Fermi level, resulting in a conductance trend of GDT-A>GDT-N>GDT-B. In the GH state, the conductance value of three molecular junctions will not change obviously with the increase of π-conjugated area, but the increase in twist angle of PAHs results in an enhancement of steric hindrance, which reduces the probability of Au-π bonding configuration, ultimately leading to a change in the formation ratio of the two molecular configurations of Au-π and Au-S.

Key words: Polycyclic aromatic hydrocarbon, Scanning tunneling microscope break junction(STM-BJ), Molecular junction, Contact configuration

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