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Guo HY, Pei LQ, Cai ZY, Sun N, Zheng JF, Shao Y, Wang YH, Wu DY, Jin S, Zhou XS. Effects of Connectivity Isomerization on Electron Transport Through Thiophene Heterocyclic Molecular Junction. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:9717-9724. [PMID: 38712354 DOI: 10.1021/acs.langmuir.4c00678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Connectivity isomerization of the same aromatic molecular core with different substitution positions profoundly affects electron transport pathways and single-molecule conductance. Herein, we designed and synthesized all connectivity isomers of a thiophene (TP) aromatic ring substituted by two dihydrobenzo[b]thiophene (BT) groups with ethynyl spacers (m,n-TP-BT, (m,n = 2,3; 2,4; 2,5; 3,4)), to systematically probe how connectivity contributes to single-molecule conductance. Single-molecule conductance measurements using a scanning tunneling microscopy break junction (STM-BJ) technique show ∼12-fold change in conductance values, which follow an order of 10-4.83 G0 (2,4-TP-BT) < 10-4.78 G0 (3,4-TP-BT) < 10-4.06 G0 (2,3-TP-BT) < 10-3.75 G0 (2,5-TP-BT). Electronic structure analysis and theoretical simulations show that the connectivity isomerization significantly changes electron delocalization and HOMO-LUMO energy gaps. Moreover, the connectivity-dependent molecular structures lead to different quantum interference (QI) effects in electron transport, e.g., a strong destructive QI near E = EF leads the smallest conductance value for 2,4-TP-BT. This work proves a clear relationship between the connectivity isomerization and single-molecule conductance of thiophene heterocyclic molecular junctions for the future design of molecular devices.
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Affiliation(s)
- Hong-Yang Guo
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China
| | - Lin-Qi Pei
- Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, China
| | - Zhuan-Yun Cai
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Nan Sun
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China
| | - Ju-Fang Zheng
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China
| | - Yong Shao
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China
| | - Ya-Hao Wang
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China
| | - De-Yin Wu
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Shan Jin
- Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan, Hubei 430079, China
| | - Xiao-Shun Zhou
- Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China
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Lawson B, Skipper HE, Kamenetska M. Phenol is a pH-activated linker to gold: a single molecule conductance study. NANOSCALE 2024; 16:2022-2029. [PMID: 38197186 DOI: 10.1039/d3nr05257e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Single molecule conductance measurements typically rely on functional linker groups to anchor the molecule to the conductive electrodes through a donor-acceptor or covalent bond. While many linking moieties, such as thiols, amines, thiothers and phosphines have been used among others, very few involve oxygen binding directly to gold electrodes. Here, we report successful single molecule conductance measurements using hydroxy (OH)-containing phenol linkers and show that the molecule-gold attachment and electron transport are mediated by a direct O-Au bond. We find that deprotonation of the hydroxy moiety is necessary for metal-molecule binding to proceed, so that junction formation can be activated through pH control. Electronic structure and DFT+Σ transport calculations confirm our experimental findings that phenolate-terminated alkanes can anchor on the gold and show charge transport trends consistent with prior observations of alkane conductance with other linker groups. Critically, the deprotonated O--Au binding shows features similar to the thiolate-Au bond, but without the junction disruption caused by intercalation of sulfur into electrode tips often observed with thiol-terminated molecules. By comparing the conductance and binding features of O-Au and S-Au bonds, this study provides insight into the aspects of Au-linker bonding that promote reproducible and robust single molecule junction measurements.
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Affiliation(s)
- Brent Lawson
- Department of Physics, Boston University, Boston, Massachusetts, 02215, USA.
| | - Hannah E Skipper
- Department of Chemistry, Boston University, Boston, Massachusetts, 02215, USA
| | - Maria Kamenetska
- Department of Physics, Boston University, Boston, Massachusetts, 02215, USA.
- Department of Chemistry, Boston University, Boston, Massachusetts, 02215, USA
- Division of Material Science and Engineering, Boston, Massachusetts, 02215, USA
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