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Miao Z, Pan X, Kamenetska M. Conductance and assembly of quasi-1D coordination chain molecular junctions with triazole derivatives. Dalton Trans 2024; 53:10453-10461. [PMID: 38868899 DOI: 10.1039/d4dt01085j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2024]
Abstract
Incorporating transition metal atoms into metal-molecule-metal junctions presents opportunities for exploring the electronic properties of coordination complexes, organometallics and metal-organic materials on the single molecule level. Recent single molecule conductance studies have shown that in situ incorporation of electrode metal atoms into coordination chains formed in the junction can occur with deprotonated, negatively charged organic ligands, such as the imidazolate (Im-) anion. However, the mechanism and chemical principles, such as the role of the charge state of the ligand, for the construction of such coordination chains are still debated. Here, we probe the role of the ligand charge state and electronic structure in single-molecule conductance and formation of metal-molecule coordination chains. We perform break junction measurements with triazole isomers, which can bridge junctions both in their neutral and charged forms, and find that prior deprotonation of the ligands is not required for coordination complex assembly, but can affect the molecular conductance and junction formation probability. Our results indicate that coordination chains can form with neutral ligands, as long as the electron density in the frontier MOs is concentrated at the binding sites and along the direction of pulling, promoting ligand binding and incorporation of gold atoms into the junction during elongation. Our findings may provide insight into design principles for in situ assembled molecular wires with transition metal atoms and open the door to electronic and spintronic studies of such materials.
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Affiliation(s)
- Zelin Miao
- Division of Materials Science and Engineering, Boston University, Boston, Massachusetts, 02215, USA.
| | - Xiaoyun Pan
- Department of Chemistry, Boston University, Boston, Massachusetts, 02215, USA
| | - Maria Kamenetska
- Division of Materials Science and Engineering, Boston University, Boston, Massachusetts, 02215, USA.
- Department of Chemistry, Boston University, Boston, Massachusetts, 02215, USA
- Department of Physics, Boston University, Boston, Massachusetts, 02215, USA
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Wang M, Zhang GP. Tuning the polarity of charge carriers in N-heterocyclic carbene-based single-molecule junctions via atomic manipulation. Phys Chem Chem Phys 2024; 26:9051-9059. [PMID: 38441317 DOI: 10.1039/d3cp04677j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
Tuning the polarity of charge carriers at a single-molecular level is essential for designing complementary logic circuits in the field of molecular electronics. Herein, the transport properties of N-heterocyclic carbene (NHC)-linked single-molecule junctions are investigated using the ab initio quantum transport approach. The results reveal that the hydrogen atoms in NHCs function as a switch for regulating the polarity of charge carriers. Dehydrogenation changes the chemical nature of NHC anchors, thereby rendering holes as the major charge carriers rather than electrons. Essentially, dehydrogenation changes the anchoring group from electron-rich to electron-deficient. The electrons transferred to molecules from the electrodes raise the molecular level closer to the Fermi level, thus resulting in charge carrier polarity conversion. This conversion is influenced by the position and number of hydrogen atoms in the NHC anchors. To efficiently and decisively alter charge carrier polarity via atomic manipulation, a methyl substitution approach is developed and verified. These results confirm that atomic manipulation is a significant method for modulating the polarity of charge carriers in NHC-based single-molecule devices.
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Affiliation(s)
- Minglang Wang
- Shandong Key Laboratory of Medical Physics and Image Processing & Shandong Provincial Engineering and Technical Center of Light Manipulations, School of Physics and Electronics, Shandong Normal University, Jinan 250358, China.
| | - Guang-Ping Zhang
- Shandong Key Laboratory of Medical Physics and Image Processing & Shandong Provincial Engineering and Technical Center of Light Manipulations, School of Physics and Electronics, Shandong Normal University, Jinan 250358, China.
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3
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Pan X, Matthews K, Lawson B, Kamenetska M. Single-Molecule Conductance of Intramolecular Hydrogen Bonding in Histamine on Gold. J Phys Chem Lett 2023; 14:8327-8333. [PMID: 37695735 DOI: 10.1021/acs.jpclett.3c02172] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/13/2023]
Abstract
We perform single-molecule conductance measurements and DFT calculations on histamine, a biogenic amine that contains a flexible aliphatic linker and several nitrogen moieties with a potential for hydrogen bonding. Our study determines that junctions containing the free-base form of histamine can bridge through a molecular structure containing an intramolecular hydrogen bond. Conductance of this structure is higher than that through the saturated aliphatic linker. Flicker noise analysis of junction conductance confirms that transport occurs through the hydrogen bond and establishes a benchmark for noise measurements in hydrogen-bonded junctions. Overall, our work provides insights into the formation and conduction of intramolecular hydrogen bonding in single-molecule conductance measurements and into the conformations of the neurotransmitter histamine on noble metal surfaces.
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Affiliation(s)
- Xiaoyun Pan
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States
| | - Katherine Matthews
- Department of Physics and Astronomy, Haverford College, Haverford, Pennsylvania 1904, United States
| | - Brent Lawson
- Department of Physics, Boston University, Boston, Massachusetts 02215, United States
| | - Maria Kamenetska
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States
- Department of Physics, Boston University, Boston, Massachusetts 02215, United States
- Divistion of Material Science and Engineering, Boston University, Boston, Massachusetts 02215, United States
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Pan X, Montes E, Rojas WY, Lawson B, Vázquez H, Kamenetska M. Cooperative Self-Assembly of Dimer Junctions Driven by π Stacking Leads to Conductance Enhancement. NANO LETTERS 2023; 23:6937-6943. [PMID: 37486358 DOI: 10.1021/acs.nanolett.3c01540] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/25/2023]
Abstract
We demonstrate enhanced electronic transport through dimer molecular junctions, which self-assemble between two gold electrodes in π-π stabilized binding configurations. Single molecule junction conductance measurements show that benzimidazole molecules assemble into dimer junctions with a per-molecule conductance that is higher than that in monomer junctions. Density functional theory calculations reveal that parallel stacking of two benzimidazoles between electrodes is the most energetically favorable due to the large π system. Imidazole is smaller and has greater conformational freedom to access different stacking angles. Transport calculations confirm that the conductance enhancement of benzimidazole dimers results from the changed binding geometry of dimers on gold, which is stabilized and made energetically accessible by intermolecular π stacking. We engineer imidazole derivatives with higher monomer conductance than benzimidazole and large intermolecular interaction that promote cooperative in situ assembly of more transparent dimer junctions and suggest at the potential of molecular devices based on self-assembled molecular layers.
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Affiliation(s)
- Xiaoyun Pan
- Department of Chemistry, Boston University, Boston, Massachusetts 02155, United States
| | - Enrique Montes
- Institute of Physics, Czech Academy of Sciences, Cukrovarnická 10, Prague CZ-162 00, Czech Republic
| | - Wudmir Y Rojas
- Institute of Physics, Czech Academy of Sciences, Cukrovarnická 10, Prague CZ-162 00, Czech Republic
| | - Brent Lawson
- Department of Physics, Boston University, Boston, Massachusetts 02155, United States
| | - Héctor Vázquez
- Institute of Physics, Czech Academy of Sciences, Cukrovarnická 10, Prague CZ-162 00, Czech Republic
| | - Maria Kamenetska
- Department of Chemistry, Boston University, Boston, Massachusetts 02155, United States
- Department of Physics, Boston University, Boston, Massachusetts 02155, United States
- Division of Material Science and Engineering, Boston University, Boston, Massachusetts 02155, United States
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Pan X, Qian C, Chow A, Wang L, Kamenetska M. Atomically precise binding conformations of adenine and its variants on gold using single molecule conductance signatures. J Chem Phys 2022; 157:234201. [PMID: 36550043 DOI: 10.1063/5.0103642] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
We demonstrate single molecule conductance as a sensitive and atomically precise probe of binding configurations of adenine and its biologically relevant variants on gold. By combining experimental measurements and density functional theory (DFT) calculations of single molecule-metal junction structures in aqueous conditions, we determine for the first time that robust binding of adenine occurs in neutral or basic pH when the molecule is deprotonated at the imidazole moiety. The molecule binds through the donation of the electron lone pairs from the imidazole nitrogen atoms, N7 and N9, to the gold electrodes. In addition, the pyrimidine ring nitrogen, N3, can bind concurrently and strengthen the overall metal-molecule interaction. The amine does not participate in binding to gold in contrast to most other amine-terminated molecular wires due to the planar geometry of the nucleobase. DFT calculations reveal the importance of interface charge transfer in stabilizing the experimentally observed binding configurations. We demonstrate that biologically relevant variants of adenine, 6-methyladenine and 2'-deoxyadenosine, have distinct conductance signatures. These results lay the foundation for biosensing on gold using single molecule conductance readout.
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Affiliation(s)
- Xiaoyun Pan
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, Massachusetts 02215, USA
| | - Cheng Qian
- Department of Chemistry and Chemical Biology, Institute for Quantitative Biomedicine, Rutgers University, 174 Frelinghuysen Road, Piscataway, New Jersey 08854, USA
| | - Amber Chow
- Department of Physics, Boston University, 590 Commonwealth Ave., Boston, Massachusetts 02215, USA
| | - Lu Wang
- Department of Chemistry and Chemical Biology, Institute for Quantitative Biomedicine, Rutgers University, 174 Frelinghuysen Road, Piscataway, New Jersey 08854, USA
| | - Maria Kamenetska
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, Massachusetts 02215, USA
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Lawson B, Zahl P, Hybertsen MS, Kamenetska M. Formation and Evolution of Metallocene Single-Molecule Circuits with Direct Gold-π Links. J Am Chem Soc 2022; 144:6504-6515. [PMID: 35353518 DOI: 10.1021/jacs.2c01322] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Single-molecule circuits with group 8 metallocenes are formed without additional linker groups in scanning tunneling microscope-based break junction (STMBJ) measurements at cryogenic and room-temperature conditions with gold (Au) electrodes. We investigate the nature of this direct gold-π binding motif and its effect on molecular conductance and persistence characteristics during junction evolution. The measurement technique under cryogenic conditions tracks molecular plateaus through the full cycle of extension and compression. Analysis reveals that junction persistence when the metal electrodes are pushed together correlates with whether electrodes are locally sharp or blunt, suggesting distinct scenarios for metallocene junction formation and evolution. The top and bottom surfaces of the "barrel"-shaped metallocenes present the electron-rich π system of cyclopentadienyl rings, which interacts with the gold electrodes in two distinct ways. An undercoordinated gold atom on a sharp tip forms a donor-acceptor bond to a specific carbon atom in the ring. However, a small, flat patch on a dull tip can bind more strongly to the ring as a whole through van der Waals interactions. Density functional theory (DFT)-based calculations of model electrode structures provide an atomic-scale picture of these scenarios, demonstrating the role of these bonding motifs during junction evolution and showing that the conductance is relatively independent of tip atomic-scale structure. The nonspecific interaction of the cyclopentadienyl rings with the electrodes enables extended conductance plateaus, a mechanism distinct from that identified for the more commonly studied, rod-shaped organic molecular wires.
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Affiliation(s)
- Brent Lawson
- Department of Physics, Boston University, Boston, Massachusetts 02215, United States
| | - Percy Zahl
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Mark S Hybertsen
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Maria Kamenetska
- Department of Physics, Boston University, Boston, Massachusetts 02215, United States.,Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States.,Division of Material Science and Engineering, Boston University, Boston, Massachusetts 02215, United States
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Li S, Jiang Y, Wang Y, Sanvito S, Hou S. In Situ Tuning of the Charge-Carrier Polarity in Imidazole-Linked Single-Molecule Junctions. J Phys Chem Lett 2021; 12:7596-7604. [PMID: 34347489 DOI: 10.1021/acs.jpclett.1c01996] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Manipulating the nature of the charge carriers at the single-molecule level is one of the major challenges of molecular electronics. Using first-principles quantum transport calculations, we have investigated the electronic transport properties of imidazole-linked single-molecule junctions and identified the hydrogen atom bonded to the pyrrole-like nitrogen in imidazole as a switch to tune the polarity of the charge carriers. Our calculations show that the chemical nature of the imidazole anchors is dramatically altered by dehydrogenation, which changes the dominant charge carriers from electrons to holes. It is also revealed that upon dehydrogenation the interfacial Au-N bonds are modified from donor-acceptor-like to covalent, along with a significant promotion of the low-bias conductance and the junction stability. At variance with other traditional methods that always require drastic modifications of the junction structure, our findings provide a promising approach to tailor in situ the polarity of charge carriers in molecular electronic devices.
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Affiliation(s)
- Shi Li
- Center for Nanoscale Science and Technology, Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China
| | - Yuxuan Jiang
- Center for Nanoscale Science and Technology, Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China
| | - Yongfeng Wang
- Center for Nanoscale Science and Technology, Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China
| | - Stefano Sanvito
- School of Physics, AMBER and CRANN Institute, Trinity College, Dublin 2, Ireland
| | - Shimin Hou
- Center for Nanoscale Science and Technology, Key Laboratory for the Physics and Chemistry of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China
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