English

Effect of Modified Thiophene Anchor on Molecule-Electrode Bonding

• Yongjiu Lei ,
• Xu Wang ,
• Zhiye Wang ,
• Jianghao Zhou ,
• Haijian Chen ,
• Lei Liang ,
• Yunchuan Li ^, ,
• Bohuai Xiao ^, ,
• Shuai Chang ^,

• School of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China

Corresponding author: Email: yc.l@wust.edu.cn (Y.L.); Tel.: +86-27-68867531 (Y.L.); Email: xiaobhuai@foxmail.com (B.X.); Email: schang23@wust.edu.cn (S.C.)

• Received Date: 14 December 2022
  Accepted Date: 28 February 2023
  Revised Date: 27 February 2023
  Available Online: 15 November 2023
• Fund Project:

  the Outstanding Young and Middle-aged Technical Innovation Team Project in Hubei Universities 

  the South China University of Technology State Key Laboratory of Luminescent Materials and Devices Open Fund 

Abstract: The anchor group of a molecule determines its binding characteristics with electrodes. It impacts the molecular conductance of the formed single molecule junctions and is of great importance to the field of molecular electronics. Thiophene unit is an emerging anchor ligand and shows the ability to bind with Au electrodes. As a building block in designing organic photoelectric materials, thiophene has a potential in expanding the variety of target molecules in single-molecule electronics. In this work, we designed and synthesized three analogous π-conjugated molecules, 1, 4-di(thiophen-2-yl)benzene (BT-H), 1, 4-bis(5 hexylthiophen-2-yl)benzene (BT-Hex) and 1, 4-bis(5-chlorothiophen-2-yl)benzene (BT-Cl). These molecules have the same backbone, but different substituents (H, C6 and Cl atoms, respectively) at position 4 of both end-capped thiophenes. Enabled by thiophene anchors, these molecules can be readily incorporated into the nano gaps between electrodes to form molecular junctions. Charge transport properties of three types of single molecule junctions are explored using scanning tunneling microscopy based break junction (STM-BJ) technique and the influence of different substituents at thiophene on the molecule-electrode binding modes are comparatively studied. Two separate binding modes with a conductance discrepancy of more than an order of magnitude are observed for all three molecules, with a high conductance state (G_H) corresponding to a Au—π linked junction (Au electrode coupled with the thiophene π orbital) and a low conductance state (G_L) originating from a Au—S binding scheme. Interestingly, the values of the G_L state for three molecules are greatly affected by the different substituents at thiophenes, yielding a conductance trend of G_BT-Hex > G_BT-H > G_BT-Cl. This can be explained by the electron affinity of different substituents, which shifts their highest occupied molecular orbital (HOMO) with respect to Au Fermi level and thus changes the energy barrier. In contrast, the G_H state values of three molecules are not affected obviously by different substituents. We also statistically analyzed the formation rate of two binding modes for three molecules and found that the ratio between two binding modes can be changed with different addition of substituents. This work provides a useful method in modifying the binding properties of thiophene as an anchor group to gold and sheds light on a simple strategy in the design of anchor ligands.

Key words:
• Single molecule conductance
•  /  Molecular configuration
•  /  Substituent group
•  /  Thiophene
•  /  Scanning tunneling microscope break junction

• 1. [1]

     Buchanan, M. Nat. Phys. 2016, 12 (3), 200. doi: 10.1038/nphys3685

  2. [2]

     杨扬, 刘俊扬, 晏润文, 吴德印, 田中群. 高等学校化学学报, 2015, 36 (1), 9. doi: 10.7503/cjcu20140941Yang, Y.; Liu, J. Y.; Yan, R. W.; Wu, D. Y.; Tian, Z. Q. Chem. J. Chin. Univ. 2015, 36 (1), 9. doi: 10.7503/cjcu20140941

  3. [3]

     余培锴, 冯安妮, 赵世强, 魏珺颖, 杨扬, 师佳, 洪文晶. 物理化学学报, 2019, 35 (8), 829. doi: 10.3866/PKU.WHXB201811027Yu, P. K.; Feng, A. N.; Zhao, S. Q.; Wei, J. Y.; Yang, Y.; Shi, J.; Hong, W. J. Acta Phys. -Chim. Sin. 2019, 35 (8), 829. doi: 10.3866/PKU.WHXB201811027

  4. [4]

     Diez-Perez, I.; Hihath, J.; Lee, Y.; Yu, L. P.; Adamska, L.; Kozhushner, M. A.; Oleynik, II; Tao, N. J. Nat. Chem. 2009, 1 (8), 635. doi: 10.1038/nchem.392

  5. [5]

     Daaoub, A.; Sangtarash, S.; Sadeghi, H. Nanomaterials 2020, 10 (8), 7. doi: 10.3390/nano10081544

  6. [6]

     Quek, S. Y.; Kamenetska, M.; Steigerwald, M. L.; Choi, H. J.; Louie, S. G.; Hybertsen, M. S.; Neaton, J. B.; Venkataraman, L. Nat. Nanotechnol. 2009, 4 (4), 230. doi: 10.1038/nnano.2009.10

  7. [7]

     Komoto, Y.; Fujii, S.; Iwane, M.; Kiguchi, M. J. Mater. Chem. C 2016, 4 (38), 8842. doi: 10.1039/c6tc03268k

  8. [8]

     Mathew, P. T.; Fang, F. Engineering 2018, 4 (6), 760. doi: 10.1016/j.eng.2018.11.001

  9. [9]

     Chen, Y. R.; Huang, L. F.; Chen, H.; Chen, Z. X.; Zhang, H. W.; Xiao, Z. Y.; Hong, W. J. Chin. J. Chem. 2021, 39 (2), 421. doi: 10.1002/cjoc.202000420

  10. [10]

      Chen, F.; Li, X.; Hihath, J.; Huang, Z.; Tao, N. J. J. Am. Chem. Soc. 2006, 128 (49), 15874. doi: 10.1021/ja065864k

  11. [11]

      Ie, Y.; Tanaka, K.; Tashiro, A.; Lee, S. K.; Testai, H. R.; Yamada, R.; Tada, H.; Aso, Y. J. Phys. Chem. Lett. 2015, 6 (18), 3754. doi: 10.1021/acs.jpclett.5b01662

  12. [12]

      Kaliginedi, V.; Rudnev, A. V.; Moreno-Garcia, P.; Baghernejad, M.; Huang, C. C.; Hong, W. J.; Wandlowski, T. Phys. Chem. Chem. Phys. 2014, 16 (43), 23529. doi: 10.1039/c4cp03605k

  13. [13]

      Sebera, J.; Lindner, M.; Gasior, J.; Meszaros, G.; Fuhr, O.; Mayor, M.; Valasek, M.; Kolivoska, V.; Hromadova, M. Nanoscale 2019, 11 (27), 12959. doi: 10.1039/c9nr04071d

  14. [14]

      Huang, Z.; Chen, F.; Bennett, P. A.; Tao, N. J. J. Am. Chem. Soc. 2007, 129 (43), 13225. doi: 10.1021/ja074456t

  15. [15]

      Xie, Z. T.; Baldea, I.; Haugstad, G.; Frisbie, C. D. J. Am. Chem. Soc. 2019, 141 (1), 497. doi: 10.1021/jacs.8b11248

  16. [16]

      Ohto, T.; Inoue, T.; Stewart, H.; Numai, Y.; Aso, Y.; Ie, Y.; Yamada, R.; Tada, H. J. Phys. Chem. Lett. 2019, 10 (18), 5292. doi: 10.1021/acs.jpclett.9b02059

  17. [17]

      Xu, Y. X.; Sun, L. Y.; Wu, J. F.; Ye, W. Y.; Chen, Y. S.; Zhang, S. M.; Miao, C. Y.; Huang, H. Dyes Pigment. 2019, 168, 36. doi: 10.1016/j.dyepig.2019.04.050

  18. [18]

      Byeon, S. Y.; Han, S. H.; Lee, J. Y. Dyes Pigment. 2018, 155, 114. doi: 10.1016/j.dyepig.2018.03.033

  19. [19]

      Oniwa, K.; Kikuchi, H.; Shimotani, H.; Ikeda, S.; Asao, N.; Yamamoto, Y.; Tanigaki, K.; Jin, T. N. Chem. Commun. 2016, 52 (26), 4800. doi: 10.1039/c6cc00948d

  20. [20]

      Zhou, J.; Yang, Y. X.; Liu, P.; Camillone, N.; White, M. G. J. Phys. Chem. C 2010, 114 (32), 13670. doi: 10.1021/jp1025009

  21. [21]

      Mao, J. -C.; Peng, L. -L.; Li, W. -Q.; Chen, F.; Wang, H. -G.; Shao, Y.; Zhou, X. -S.; Zhao, X. -Q.; Xie, H. -J.; Niu, Z. -J. J. Phys. Chem. C 2017, 121 (3), 1472. doi: 10.1021/acs.jpcc.6b10925

  22. [22]

      Huang, M.; Dong, J.; Wang, Z.; Li, Y.; Yu, L.; Liu, Y.; Qian, G.; Chang, S. Chem. Commun. 2020, 56 (94), 14789. doi: 10.1039/d0cc05602b

  23. [23]

      Huang, M.; Zhou, Q.; Liang, F.; Yu, L.; Xiao, B.; Li, Y.; Zhang, M.; Chen, Y.; He, J.; Xiao, S.; et al. Nano Lett. 2021, 21 (12), 5409. doi: 10.1021/acs.nanolett.1c01882

  24. [24]

      Chen, H.; Li, Y.; Chang, S. Anal. Chem. 2020, 92 (9), 6423. doi: 10.1021/acs.analchem.9b05549

  25. [25]

      Wang, Z.; Huang, M.; Dong, J.; Wang, X.; Li, Y.; Sun, M.; Chang, S. J. Phys. Chem. C 2023, 127 (5), 2518. doi: 10.1021/acs.jpcc.2c06683

  26. [26]

      Li, Y.; Xiao, B.; Chen, R.; Chen, H.; Dong, J.; Liu, Y.; Chang, S. Chem. Commun. 2019, 55 (57), 8325. doi: 10.1039/c9cc02998b

  27. [27]

      华煜晖, 张弘, 夏海平. 有机化学, 2018, 38 (1), 11. doi: 10.6023/cjoc201709009Hua, Y.; Zhang, H.; Xia, H. Chin. J. Org. Chem. 2018, 38 (1), 11. doi: 10.6023/cjoc201709009

  28. [28]

      Moellmann, J.; Grimme, S. J. Phys. Chem. C 2014, 118 (14), 7615. doi: 10.1021/jp501237c

  29. [29]

      Smith, D. G.; Burns, L. A.; Patkowski, K.; Sherrill, C. D. J. Phys. Chem. Lett. 2016, 7 (12), 2197. doi: 10.1021/acs.jpclett.6b00780

  30. [30]

      Li, S. S.; Jira, E. R.; Angello, N. H.; Li, J. L.; Yu, H.; Moore, J. S.; Diao, Y.; Burke, M. D.; Schroeder, C. M. Nat. Commun. 2022, 13 (1), 8. doi: 10.1038/s41467-022-29796-2

  31. [31]

      Makk, P.; Tomaszewski, D.; Martinek, J.; Balogh, Z.; Csonka, S.; Wawrzyniak, M.; Frei, M.; Venkataraman, L.; Halbritter, A. ACS Nano 2012, 6 (4), 3411. doi: 10.1021/nn300440f

  32. [32]

      Balogh, Z.; Makk, P.; Halbritter, A. Beilstein J. Nanotechnology 2015, 6, 1369. doi: 10.3762/bjnano.6.141

  33. [33]

      Huang, C.; Jevric, M.; Borges, A.; Olsen, S. T.; Hamill, J. M.; Zheng, J. T.; Yang, Y.; Rudnev, A.; Baghernejad, M.; Broekmann, P.; et al. Nat. Commun. 2017, 8, 15436. doi: 10.1038/ncomms15436

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