Single‐Molecule Doping: Conductance Changed By Transition Metal Centers in Salen Molecules

Kilibarda, Filip; Strobel, Alexander; Sendler, Torsten; Wieser, Matthias; Mortensen, Michael; Trads, Julie B.; Helm, M.; Kerbusch, Jochen; Scheer, Elke; Gemming, Sibylle; Gothelf, Kurt V.; Erbe, Artur

doi:10.1002/aelm.202100252

Cited by 7 publications

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References 35 publications

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“…Density functional theory (DFT) calculations results by Palma demonstrate that acene derivatives have near length-independent conductance and the anchoring configuration (steric effect) could dominate the conductance behavior. In general, intrinsic electronic property study of atomically thin GNRs at the single molecule level still presents a great challenge in terms of structure–property interpretations, − and there still lacks a good example to case-study the regio- and steric effect of anchoring groups on the molecular conductance of GNRs with atomic precision. A systematic case-study of the regio- and steric effect of six phenanthrene derivatives with dithiomethyl substitutions at different positions as the anchoring groups with the same aromatic core is highly desirable.…”

Section: Introductionmentioning

confidence: 99%

Regio- and Steric Effects on Single Molecule Conductance of Phenanthrenes

et al. 2021

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Here, six phenanthrene (the smallest arm-chair graphene nanoribbon) derivatives with dithiomethyl substitutions at different positions as the anchoring groups were synthesized. Scanning tunneling microscopy break junction technique was used to measure their single molecule conductances between gold electrodes, which showed a difference as much as 20-fold in the range of ∼10–2.82 G0 to ∼10–4.09 G0 following the trend of G2,7 > G3,6 > G2,6 > G1,7 > G1,6 > G1,8. DFT calculations agree well with this measured trend and indicate that the single molecule conductances are a combination of energy alignment, electronic coupling, and quantum effects. This significant regio- and steric effect on the single molecule conductance of phenanthrene model molecules shows the complexity in the practice of graphene nanoribbons as building blocks for future carbon-based electronics in one hand but also provides good conductance tunability on the other hand.

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Section: Introductionmentioning

confidence: 99%

Regio- and Steric Effects on Single Molecule Conductance of Phenanthrenes

et al. 2021

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“…Characterizing the physical and electronic properties of such single-molecular components requires selectivity and resolution at the nanoscale. This can be achieved using scanning tunneling microscopy (STM), , atomic force microscopy (AFM), − mechanically controllable break junctions (MCBJs), , and electromigrated (EM) break junctions. The electron transport regimes, where these different measurement techniques are employed, have been discussed in detail in the literature .…”

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“…Among the above-mentioned techniques, MCBJs enable a more systematic study of the current–voltage ( I–V ) characteristics and conductance-breaking traces owing to the mechanical stability of the junctions. The stability of such molecule junctions is dictated by the binding strength of the anchoring group, deformation of the molecule, and thermal vibrations. ,− Nevertheless, molecules can bind to the metallic electrodes at different positions and in various orientations depending on the specific chemical nature of the anchoring groups and the local symmetry of binding sites, ,− which makes it a challenging task to elucidate the underlying physical mechanism governing the electronic behavior of single-molecule junctions.…”

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confidence: 99%

“…Usually, 1-D conductance histograms and conductance-distance 2-D histograms are constructed from few hundreds or thousands of individual traces. The most probable I–V characteristic for a particular molecule–metal combination is associated with the most prominent conductance peak observed in the conductance histograms. ,,,,, The experimental characterization of single-molecule junctions via MCBJ is complemented with ab initio transport calculations, in order to estimate the relative positions of molecular levels, which act as transport channels, and the chemical potential of the metallic leads. ,,− However, the theoretical modeling of the broad distribution in the experimental conductance histograms is not feasible because (1) in MCBJ experiments, the adsorption geometries of the molecule between the metallic electrodes are a priori unknown, − (2) many experimental factors remain elusive and are therefore not considered, and (3) the ab initio transport calculations are computationally expensive. Consequently, a limited number of energetically most favorable configurations are selected as representative junction geometries for theoretical investigations. ,,, However, recent technological advancements allow the simultaneous measurement of mechanical and electronic properties of single-molecule junctions, which enables deeper understanding of the structural information on junction geometries.…”

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“…Two full-range I–V -curves are obtained for a single bridge position. We wait at least 90 s between the I–V measurements following a butterfly sweep and until the standard deviation of the measured signal is lower than a threshold . The opening speed of the tips is of the order of 2 × 10 –12 m/s.…”

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Stretch Evolution of Electronic Coupling of the Thiophenyl Anchoring Group with Gold in Mechanically Controllable Break Junctions

Lokamani

Kilibarda

Günther

et al. 2023

J. Phys. Chem. Lett.

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The current–voltage characteristics of a single-molecule junction are determined by the electronic coupling Γ between the electronic states of the electrodes and the dominant transport channel(s) of the molecule. Γ is profoundly affected by the choice of the anchoring groups and their binding positions on the tip facets and the tip–tip separation. In this work, mechanically controllable break junction experiments on the N,N′-bis(5-ethynylbenzenethiol-salicylidene)ethylenediamine are presented, in particular, the stretch evolution of Γ with increasing tip–tip separation. The stretch evolution of Γ is characterized by recurring local maxima and can be related to the deformation of the molecule and sliding of the anchoring groups above the tip facets and along the tip edges. A dynamic simulation approach is implemented to model the stretch evolution of Γ, which captures the experimentally observed features remarkably well and establishes a link to the microscopic structure of the single-molecule junction.

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Regulating effect of the halogen atoms on the cofacial dinuclear Schiff base complexes: Synthesis, spectroscopy, electrochemistry, and DFT calculations

Huang,

Jiao,

Yang

et al. 2024

Applied Organom Chemis

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The present study reports the synthesis and characterization of two new halogenated Schiff base copper (II) derivatives, namely [CuII2(3‐Cl‐Salmphen)2] (Cu‐Cl‐Salmphen) and [CuII2(3‐Br‐Salmphen)2] (Cu‐Br‐Salmphen), which were characterized by UV–Vis, FT‐IR, 1H‐NMR, and 13C‐NMR spectroscopy. Single crystal structural analysis revealed that each complex contains two crystallography independent, distorted copper centers, where each Cu center exhibits the same coordination environment with N2O2 donor atoms from two different ligands. To investigate the substitution effect of halogen atoms on the properties of the complexes, the non‐halogenated isomer [CuII2(H‐Salmphen)2] (Cu‐H‐Salmphen) was introduced for comparison. The differences between the halogenated and the non‐halogenated analogues were compared through spectroscopic, electrochemical, DFT, and TD‐DFT theoretical calculations. The optical experimental results indicated that the introduction of halogen atoms decreased the energy gap between the ground and excited states, leading to enhanced optical absorption capabilities of the compounds. Electrochemical tests showed that the halogenated analogues exhibited better electrochemical performance, and with the increase in an atomic number of the halogen atoms, the compounds displayed a gradual increase in cyclic voltammetry peak areas, diffusion coefficients, and conductivities. Theoretical calculations revealed that the introduction of halogen atoms simultaneously expanded the conjugated area of the molecules, decreased the HOMO‐LUMO energy levels of the complexes, and strengthened the intramolecular interactions. Furthermore, the potential mechanism of the tuning effect of halogen atoms on the charge transfer process was proposed.

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Single‐Molecule Doping: Conductance Changed By Transition Metal Centers in Salen Molecules

Cited by 7 publications

References 35 publications

Regio- and Steric Effects on Single Molecule Conductance of Phenanthrenes

Regio- and Steric Effects on Single Molecule Conductance of Phenanthrenes

Stretch Evolution of Electronic Coupling of the Thiophenyl Anchoring Group with Gold in Mechanically Controllable Break Junctions

Regulating effect of the halogen atoms on the cofacial dinuclear Schiff base complexes: Synthesis, spectroscopy, electrochemistry, and DFT calculations

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