scholarly journals Single-molecule level control of host-guest interactions in metallocycle-C60 complexes

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Jian-Hong Tang ◽  
Yueqi Li ◽  
Qingqing Wu ◽  
Zixiao Wang ◽  
Songjun Hou ◽  
...  
Keyword(s):  
Single Molecule ◽  
Guest Molecule ◽  
Scanning Tunneling ◽  
Level Control ◽  
Tunneling Microscopy ◽  
Central Importance ◽  
Single Molecule Level ◽  
Order Of Magnitude ◽  
Different Shapes ◽  
Mechanical Stretching

Abstract Host−guest interactions are of central importance in many biological and chemical processes. However, the investigation of the formation and decomplexation of host−guest systems at the single-molecule level has been a challenging task. Here we show that the single-molecule conductance of organoplatinum(II) metallocycle hosts can be enhanced by an order of magnitude by the incorporation of a C60 guest molecule. Mechanically stretching the metallocycle-C60 junction with a scanning tunneling microscopy break junction technique causes the release of the C60 guest from the metallocycle, and consequently the conductance switches back to the free-host level. Metallocycle hosts with different shapes and cavity sizes show different degrees of flexibility to accommodate the C60 guest in response to mechanical stretching. DFT calculations provide further insights into the electronic structures and charge transport properties of the molecular junctions based on metallocycles and the metallocycle-C60 complexes.

scholarly journals Realizing Two-Dimensional Spin Arrays on Surfaces via Halogen-Bonding Molecular Self-Assembly

2021 ◽  
Author(s):  
Dingguan Wang ◽  
Zishen Wang ◽  
Shaofei Wu ◽  
Arramel Arramel ◽  
Xinmao Yin ◽  
...  
Keyword(s):  
Single Molecule ◽  
Self Assembly ◽  
Halogen Bonding ◽  
Scanning Tunneling ◽  
Two Dimensional ◽  
Halogen Bonds ◽  
Tunneling Microscopy ◽  
Single Molecule Level ◽  
Magnetic Devices ◽  
Temperature Scanning

Well-ordered spin arrays are highly desirable for next-generation molecule-based magnetic devices, and yet its synthetic method remains a challenging task. Herein, we demonstrate the realization of two-dimensional supramolecular spin arrays on surfaces via halogen-bonding molecular self-assembly. A bromine-terminal perchlorotriphenymethyl radical with net carbon spin was synthesized and deposited on Au(111) to achieve two-dimensional supramolecular spin arrays. By taking advantage of the diversity of halogen bonds, five supramolecular spin arrays are presented with ultrahigh spin densities (up to the value of 3 × 10<sup>13</sup> spins at the size of a flash drive), as probed by low-temperature scanning tunneling microscopy at the single-molecule level. First principle calculations verify that the formation of three distinct types of halogen bonds can be used to tailor supramolecular phases via molecular coverage and annealing temperature. Our work demonstrates supramolecular self-assembly as a promising method to engineering 2D spin arrays for potential application in magnetic devices.

scholarly journals From Starphenes to Non-Benzenoid Linear Conjugated Polymers by Substrate Templating

2020 ◽  
Author(s):  
Mohammed S. G. Mohammed ◽  
James Lawrence ◽  
Fátima García ◽  
Pedro Brandimarte ◽  
Alejandro Berdonces-Layunta ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Single Molecule ◽  
Molecular Structures ◽  
Synthetic Methods ◽  
Synthesis And Characterization ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Single Molecule Level ◽  
Templating Effect

Combining on-surface synthetic methods with the power of scanning tunneling microscopy to characterize novel materials at the single molecule level, we show how to steer the reactivity of one anthracene-based precursor towards different product nanostructures. Whereas using a two-dimensional Au(111) surface results in the dominant formation of a starphene derivative, the templating effect of a reconstructed Au(110) surface allows the selective growth of non-benzenoid linear conjugated polymers. We further assess the electronic properties of each of the observed product structures via tunneling spectroscopy and DFT calculations, altogether advancing in the synthesis and characterization of molecular structures of notable scientific interest that have been only scarcely investigated to date, as applied to both starphenes and to non-benzenoid conjugated polymers. <br>

Determining structural and chemical heterogeneities of surface species at the single-bond limit

Science ◽  
2021 ◽  
Vol 371 (6531) ◽  
pp. 818-822
Author(s):  
Jiayu Xu ◽  
Xiang Zhu ◽  
Shijing Tan ◽  
Yao Zhang ◽  
Bin Li ◽  
...  
Keyword(s):  
Single Molecule ◽  
Scanning Tunneling ◽  
Surface Species ◽  
Tunneling Microscopy ◽  
Single Molecule Level ◽  
Force Microscopy ◽  
Chemical Structures ◽  
Atomic Force ◽  
Surface Catalysis ◽  
Enhanced Raman Scattering

The structure determination of surface species has long been a challenge because of their rich chemical heterogeneities. Modern tip-based microscopic techniques can resolve heterogeneities from their distinct electronic, geometric, and vibrational properties at the single-molecule level but with limited interpretation from each. Here, we combined scanning tunneling microscopy (STM), noncontact atomic force microscopy (AFM), and tip-enhanced Raman scattering (TERS) to characterize an assumed inactive system, pentacene on the Ag(110) surface. This enabled us to unambiguously correlate the structural and chemical heterogeneities of three pentacene-derivative species through specific carbon-hydrogen bond breaking. The joint STM-AFM-TERS strategy provides a comprehensive solution for determining chemical structures that are widely present in surface catalysis, on-surface synthesis, and two-dimensional materials.

scholarly journals From starphenes to non-benzenoid linear conjugated polymers by substrate templating

2021 ◽  
Author(s):  
Mohammed S. G. Mohammed ◽  
James Lawrence ◽  
Fátima García ◽  
Pedro Brandimarte ◽  
Alejandro Berdonces-Layunta ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Conjugated Polymers ◽  
Single Molecule ◽  
Synthetic Methods ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Single Molecule Level ◽  
Novel Materials

Combining on-surface synthetic methods with the power of scanning tunneling microscopy to charac-terize novel materials at the single molecule level, we show how to steer the reactivity of one anthra-cene-based...

scholarly journals From Starphenes to Non-Benzenoid Linear Conjugated Polymers by Substrate Templating

2020 ◽  
Author(s):  
Mohammed S. G. Mohammed ◽  
James Lawrence ◽  
Fátima García ◽  
Pedro Brandimarte ◽  
Alejandro Berdonces-Layunta ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Single Molecule ◽  
Molecular Structures ◽  
Synthetic Methods ◽  
Synthesis And Characterization ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Single Molecule Level ◽  
Templating Effect

Combining on-surface synthetic methods with the power of scanning tunneling microscopy to characterize novel materials at the single molecule level, we show how to steer the reactivity of one anthracene-based precursor towards different product nanostructures. Whereas using a two-dimensional Au(111) surface results in the dominant formation of a starphene derivative, the templating effect of a reconstructed Au(110) surface allows the selective growth of non-benzenoid linear conjugated polymers. We further assess the electronic properties of each of the observed product structures via tunneling spectroscopy and DFT calculations, altogether advancing in the synthesis and characterization of molecular structures of notable scientific interest that have been only scarcely investigated to date, as applied to both starphenes and to non-benzenoid conjugated polymers. <br>

Single molecule level studies of reversible ligand binding to metal porphyrins at the solution/solid interface

2020 ◽  
Vol 24 (08) ◽  
pp. 993-1002 ◽  
Author(s):  
Ursula Mazur ◽  
K. W. Hipps
Keyword(s):  
Ligand Binding ◽  
Single Molecule ◽  
Quantitative Information ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Metal Porphyrin ◽  
Single Molecule Level ◽  
Solid Interface ◽  
Metal Porphyrins ◽  
Exogenous Ligands

Ligands bind reversibly to metal porphyrins in processes such as molecular recognition, electron transport and catalysis. These chemically relevant processes are ubiquitous in biology and are important in technological applications. In this article, we focus on the current advances in ligand binding to metal porphyrin receptors noncovalently bound at the solution/solid interface. In particular, we restrict ourselves to studies at the single molecule level. Dynamics of the binding/dissociation process can be monitored by scanning tunneling microscopy (STM) and can yield both qualitative and quantitative information about ligand binding affinity and the energetics that define a particular ligation reaction. Molecular and time dependent imaging can establish whether the process under study is at equilibrium. Ligand-concentration-dependent studies have been used to determine adsorption isotherms and thermodynamic data for processes occurring at the solution/solid interface. In several binding reactions, the solid support acted as an electron-donating fifth coordination site, thereby significantly changing the metal porphyrin receptor’s affinity for exogenous ligands. Supporting calculations provide insight into the metalloporphyrin/support and ligand–metalloporphyrin/support interactions and their energetics.

scholarly journals Realizing Two-Dimensional Spin Arrays on Surfaces via Halogen-Bonding Molecular Self-Assembly

2021 ◽  
Author(s):  
Dingguan Wang ◽  
Zishen Wang ◽  
Shaofei Wu ◽  
Arramel Arramel ◽  
Xinmao Yin ◽  
...  
Keyword(s):  
Single Molecule ◽  
Self Assembly ◽  
Halogen Bonding ◽  
Scanning Tunneling ◽  
Two Dimensional ◽  
Halogen Bonds ◽  
Tunneling Microscopy ◽  
Single Molecule Level ◽  
Magnetic Devices ◽  
Temperature Scanning

Well-ordered spin arrays are highly desirable for next-generation molecule-based magnetic devices, and yet its synthetic method remains a challenging task. Herein, we demonstrate the realization of two-dimensional supramolecular spin arrays on surfaces via halogen-bonding molecular self-assembly. A bromine-terminal perchlorotriphenymethyl radical with net carbon spin was synthesized and deposited on Au(111) to achieve two-dimensional supramolecular spin arrays. By taking advantage of the diversity of halogen bonds, five supramolecular spin arrays are presented with ultrahigh spin densities (up to the value of 3 × 10<sup>13</sup> spins at the size of a flash drive), as probed by low-temperature scanning tunneling microscopy at the single-molecule level. First principle calculations verify that the formation of three distinct types of halogen bonds can be used to tailor supramolecular phases via molecular coverage and annealing temperature. Our work demonstrates supramolecular self-assembly as a promising method to engineering 2D spin arrays for potential application in magnetic devices.

Substituent-mediated quantum interference toward a giant single-molecule conductance variation

2021 ◽  
Author(s):  
Yi-Fan Zhou ◽  
Wen-Yan Chang ◽  
Jing-Zhe Chen ◽  
Jun-Ren Huang ◽  
Jia-Ying Fu ◽  
...  
Keyword(s):  
Single Molecule ◽  
Quantum Interference ◽  
High Performance ◽  
Substituent Effects ◽  
Molecular Junctions ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Transmission Coefficients ◽  
Order Of Magnitude ◽  
Promising Perspective

Abstract Quantum interference (QI) in single molecular junctions shows a promising perspective for realizing conceptual nanoelectronics. However, controlling and modulating the QI remains a big challenge. Herein, two-type substituents at different positions of meta-linked benzene, namely electron-donating methoxy (-OMe) and electron-withdrawing nitryl (-NO2), are designed and synthesized to investigate the substituent effects on QI. The calculated transmission coefficients T(E) indicates that -OMe and -NO2 could remove the antiresonance and destructive quantum interference (DQI)-induced transmission dips at position 2. -OMe could raise the antiresonance energy at position 4 while -NO2 groups removes the DQI features. For substituents at position 5, both of them are nonactive for tuning QI. The conductance measurements by scanning tunneling microscopy break junction (STM-BJ) show a good agreement with the theoretical prediction. More than two order of magnitude single-molecule conductance on/off ratio could be achieved at the different positions of -NO2 substituent groups at room temperature. The present work proves chemical substituents can be used for tuning QI features in single molecular junctions, which provides a feasible way toward realization of high-performance molecular devices.

Charge Transfer Complexation Boosts Molecular Conductance Through Fermi Level Pinning

2018 ◽  
Author(s):  
Kun Wang ◽  
Andrea Vezzoli ◽  
Iain Grace ◽  
Maeve McLaughlin ◽  
Richard Nichols ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Single Molecule ◽  
Quantum Interference ◽  
Transmission Function ◽  
Scanning Tunneling ◽  
Charge Transfer Complexes ◽  
Tunneling Microscopy ◽  
Quantum Interference Effect ◽  
Single Molecule Junctions ◽  
Charge Transfer Complexation

We have used scanning tunneling microscopy to create and study single molecule junctions with thioether-terminated oligothiophene molecules. We find that the conductance of these junctions increases upon formation of charge transfer complexes of the molecules with tetracyanoethene, and that the extent of the conductance increase is greater the longer is the oligothiophene, i.e. the lower is the conductance of the uncomplexed molecule in the junction. We use non-equilibrium Green's function transport calculations to explore the reasons for this theoretically, and find that new resonances appear in the transmission function, pinned close to the Fermi energy of the contacts, as a consequence of the charge transfer interaction. This is an example of a room temperature quantum interference effect, which in this case boosts junction conductance in contrast to earlier observations of QI that result in diminished conductance.<br>

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