Probing the Conductance of the σ-System of Bipyridine Using Destructive Interference

Borges, Antônio Newton; Fung, E-Dean; Ng, Fay; Venkataraman, Latha; Solomon, Gemma C.

doi:10.1021/acs.jpclett.6b02494

“…Interestingly, this head group also showed the highest G M when using a graphene‐coated probe. These results are consistent with constructive ( p P ) and destructive ( m P ) QI effects occurring for both probes, even though in short single molecules, such effects are sensitive to the nature of the molecule–electrode contact and can be masked, due to parallel transport through the σ‐channel and π–σ mixing . The higher conductance of the B head group relative to m P suggests that π–probe interactions contribute significantly to electronic coupling for both probes, as the former has no other binding functionality.…”

Section: Resultssupporting

confidence: 81%

Carbazole‐Based Tetrapodal Anchor Groups for Gold Surfaces: Synthesis and Conductance Properties

O’Driscoll

¹

,

Wang

²

,

Jay

³

et al. 2019

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As the field of molecular‐scale electronics matures and the prospect of devices incorporating molecular wires becomes more feasible, it is necessary to progress from the simple anchor groups used in fundamental conductance studies to more elaborate anchors designed with device stability in mind. This study presents a series of oligo(phenylene‐ethynylene) wires with one tetrapodal anchor and a phenyl or pyridyl head group. The new anchors are designed to bind strongly to gold surfaces without disrupting the conductance pathway of the wires. Conductive probe atomic force microscopy (cAFM) was used to determine the conductance of self‐assembled monolayers (SAMs) of the wires in Au–SAM–Pt and Au–SAM–graphene junctions, from which the conductance per molecule was derived. For tolane‐type wires, mean conductances per molecule of up to 10−4.37 G0 (Pt) and 10−3.78 G0 (graphene) were measured, despite limited electronic coupling to the Au electrode, demonstrating the potential of this approach. Computational studies of the surface binding geometry and transport properties rationalise and support the experimental results.

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“…The pP head group was expected to perform best with am etallic probe,d ue to interactions between the probe and the pyridine lone pair, which were anticipated to enhance electronic coupling,and constructive QI effects.Interestingly, this head group also showed the highest G M when using ag raphene-coated probe.T hese results are consistent with constructive (pP)a nd destructive (mP)Q Ie ffects occurring for both probes,e ven though in short single molecules,s uch effects are sensitive to the nature of the molecule-electrode contact and can be masked, due to parallel transport through the s-channel and p-s mixing. [19] Theh igher conductance of the B head group relative to mP suggests that p-probe interactions contribute significantly to electronic coupling for both probes,asthe former has no other binding functionality.…”

Section: Angewandte Chemiementioning

confidence: 99%

Carbazole‐Based Tetrapodal Anchor Groups for Gold Surfaces: Synthesis and Conductance Properties

O’Driscoll

¹

,

Wang

²

,

Jay

³

et al. 2019

View full text Add to dashboard Cite

As the field of molecular‐scale electronics matures and the prospect of devices incorporating molecular wires becomes more feasible, it is necessary to progress from the simple anchor groups used in fundamental conductance studies to more elaborate anchors designed with device stability in mind. This study presents a series of oligo(phenylene‐ethynylene) wires with one tetrapodal anchor and a phenyl or pyridyl head group. The new anchors are designed to bind strongly to gold surfaces without disrupting the conductance pathway of the wires. Conductive probe atomic force microscopy (cAFM) was used to determine the conductance of self‐assembled monolayers (SAMs) of the wires in Au–SAM–Pt and Au–SAM–graphene junctions, from which the conductance per molecule was derived. For tolane‐type wires, mean conductances per molecule of up to 10−4.37 G0 (Pt) and 10−3.78 G0 (graphene) were measured, despite limited electronic coupling to the Au electrode, demonstrating the potential of this approach. Computational studies of the surface binding geometry and transport properties rationalise and support the experimental results.

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“…meta-connection [44][45][46] of the branches to the pyridyl anchor group, although it has been recently demonstrated that for meta-connected bipyridine DQI in the π electron contribution can be masked by the conductance mediated by σ electrons 47 , ii) from interference between transmission through the two branches which is expected to be constructive for the neutral molecule but might be destructive if the redox-active center on only one of the branches is oxidized, and iii) also from multiple paths provided by nearly degenerate orbitals on the ferrocene moieties. In order to be able to distinguish between these effects we extend our study to the range of molecular junctions illustrated in Fig.…”

Section: Figmentioning

confidence: 99%

“…43 . Such less distinctly visible manifestations of DQI can occur in DFT calculations for real systems, because DQI is linked to the symmetry properties of the π-electrons of a conjugated system, where the σ-electrons are not necessarily affected 47 . Our definition of DQI is that the transmission through a system with more than one MO around E F is lower than the sum of the individual contributions of these MOs to T(E) 40 .…”

Section: B Transmission Functions From Negf-dft and The Observation mentioning

confidence: 99%

“…Hence, we obtained the basis which we need to apply in our TB models by subsequent subdiagonalizations and basis set rotations of the transport Hamiltonian on each C and N atom individually. 47 Additionally, orthogonality between AOs on neighbouring atoms was ensured by applying a Löwdin transformation 56 . As it has been demonstrated in the supporting information of Ref.…”

Section: A Definition Of the Electrodes For All Negf-tb Calculationsmentioning

confidence: 99%

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Quantum interference in coherent tunneling through branched molecular junctions containing ferrocene centers

Zhao

¹

,

Kastlunger

²

,

Stadler

³

2017

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In our theoretical study where we combine a nonequilibrium Green's function (NEGF) approach with density functional theory (DFT) we investigate branched compounds containing ferrocene moieties in both branches which due to their metal centers are designed to allow for asymmetry induced by local charging. In these compounds the ferrocene moieties are connected to pyridyl anchor groups either directly or via acetylenic spacers in a meta-connection where we also compare our results with those obtained for the respective single-branched molecules with both meta-and para-connections between the metal center and the anchors. We find a destructive quantum interference (DQI) feature in the transmission function slightly below the lowest unoccupied molecular orbital (LUMO) which dominates the conductance even for the uncharged branched compound with spacer groups inserted. In an analysis based on mapping the structural characteristics of the range of molecules in our article onto tight-binding models, we identify the structural source of the DQI minimum as the through-space coupling between the pyridyl anchor groups. We also find that local charging on one of the branches only changes the conductance by about one order of magnitude which we explain in terms of the spatial distributions of the relevant molecular orbitals for the branched compounds.

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Probing the Conductance of the σ-System of Bipyridine Using Destructive Interference

Cited by 53 publications

References 30 publications

Carbazole‐Based Tetrapodal Anchor Groups for Gold Surfaces: Synthesis and Conductance Properties

Carbazole‐Based Tetrapodal Anchor Groups for Gold Surfaces: Synthesis and Conductance Properties

Carbazole‐Based Tetrapodal Anchor Groups for Gold Surfaces: Synthesis and Conductance Properties

Quantum interference in coherent tunneling through branched molecular junctions containing ferrocene centers

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