Structure−Property Relationships in Redox-Gated Single Molecule Junctions − A Comparison of Pyrrolo-Tetrathiafulvalene and Viologen Redox Groups

Leary, Edmund; Higgins, Simon J.; Zalinge, Harm van; Haiss, Wolfgang; Nichols, Richard J.; Nygaard, Sune; Jeppesen, Jan O.; Ulstrup, Jens

doi:10.1021/ja8014605

Cited by 109 publications

(117 citation statements)

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“…By contrast, in aqueous electrolytes, only the first redox transition, from 6pTTF6 0 to 6pTTF6 +• is observed. 22 An increase in the single-molecule conductance of 6pTTF6 from ∼0.5 to ∼2 nS was observed, around the redox potential for both redox transitions in the ionic liquid. The conductance data obtained for 6pTTF6 in BMIOTf could be modeled by the KU model of two-step charge transfer with partial vibrational relaxation, which provided a good fit to the data.…”

Section: ■ Conclusionmentioning

confidence: 93%

“…The compound 6pTTF6 was synthesized by a published route. 22,41 Electrochemistry Experiments. All cyclic voltammetry measurements were performed on Ecochemie Autolab potentiostats; either the PGSTAT 20 or PGSTAT 30 model with the corresponding Autolab GPES software.…”

Section: ■ Experimental Methodsmentioning

confidence: 99%

“…10,12,15 For instance, for the viologen 6V6 ( Figure 3) the molecular conductance increases upon reducing the viologen group, but it remains at this higher conductance value even as the electrode potential is swept more negative, leading to a sigmoidal 10,12,15 rather than the bell-shaped profile depicted in Figure 2. Other systems in the molecular break junction configuration also exhibit I tunneling vs electrochemical potential responses which do not easily accord with the KU or Schmickler models for electron transfer across the redox active bridge unless additional features such as gated charge transfer are introduced, as discussed by Haiss et al 12 An exception is the pTTF system in aqueous electrolyte reported by Leary et al, 22 which, at least qualitatively, appears to give a response which accords with either the KU or Schmickler models. However, detailed analysis of this system has not been made with respect to either model.…”

Section: ■ Introductionmentioning

confidence: 99%

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Single-Molecule Electrochemical Gating in Ionic Liquids

et al. 2012

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The single-molecular conductance of a redox active molecular bridge has been studied in an electrochemical single-molecule transistor configuration in a room-temperature ionic liquid (RTIL). The redox active pyrrolo-tetrathiafulvalene (pTTF) moiety was attached to gold contacts at both ends through −(CH2)6S– groups, and gating of the redox state was achieved with the electrochemical potential. The water-free, room-temperature, ionic liquid environment enabled both the monocationic and the previously inaccessible dicationic redox states of the pTTF moiety to be studied in the in situ scanning tunneling microscopy (STM) molecular break junction configuration. As the electrode potential is swept to positive potentials through both redox transitions, an ideal switching behavior is observed in which the conductance increases and then decreases as the first redox wave is passed, and then increases and decreases again as the second redox process is passed. This is described as an “off–on–off–on–off” conductance switching behavior. This molecular conductance vs electrochemical potential relation could be modeled well as a sequential two-step charge transfer process with full or partial vibrational relaxation. Using this view, reorganization energies of ∼1.2 eV have been estimated for both the first and second redox transitions for the pTTF bridge in the 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIOTf) ionic liquid environment. By contrast, in aqueous environments, a much smaller reorganization energy of ∼0.4 eV has been obtained for the same molecular bridge. These differences are attributed to the large, outer-sphere reorganization energy for charge transfer across the molecular junction in the RTIL.

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Section: ■ Conclusionmentioning

confidence: 93%

Section: ■ Experimental Methodsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Single-Molecule Electrochemical Gating in Ionic Liquids

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“…Conductance switching in molecular junctions has been demonstrated previously using various means including light, 1, 2 bias pulses, 3 electrostatic-, 4,5 and electrochemical gating. 6,7 The concept of "electrochemical gating" which provides the opportunity to overcome the technical challenges of incorporating a gate electrode in a solid-state molecular device, has been employed in electrochemically active molecular systems, including viologens, [8][9][10] oligoaniline, 11 ferrocene, [12][13][14] transition metal complexes, 7,15,16 perylenebisimides, [17][18][19] redox-active proteins, 20,21 quinones 22,23 and tetrathiafulvalene, 24 as well as redox-inactive molecules. 25 In the case of redox-inactive molecules, or more generally when the electrode potential does not overlap with the molecule's redox potential, the effect of the gate is simply to shift the molecular levels up or down in energy relative to the Fermi level.…”

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Electrochemical Control of Single-Molecule Conductance by Fermi-Level Tuning and Conjugation Switching

et al. 2014

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Controlling charge transport through a single molecule connected to metallic electrodes remains one of the most fundamental challenges of nanoelectronics. Here we use electrochemical gating to reversibly tune the conductance of two different organic molecules, both containing anthraquinone (AQ) centers, over >1 order of magnitude. For electrode potentials outside the redox-active region, the effect of the gate is simply to shift the molecular energy levels relative to the metal Fermi level. At the redox potential, the conductance changes abruptly as the AQ unit is oxidized/reduced with an accompanying change in the conjugation pattern between linear and cross conjugation. The most significant change in conductance is observed when the electron pathway connecting the two electrodes is via the AQ unit. This is consistent with the expected occurrence of destructive quantum interference in that case. The experimental results are supported by an excellent agreement with ab initio transport calculations.

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“…This could provide an alternate design strategy for molecular devices other than through purely organic molecules due to the wealth of different structures possible via inorganic chemistry. Recent progress in implementing a gate in single-molecule based devices [42][43][44][45] allows us to predict for the studied molecule, with its controlled binding to the electrodes and with its two levels aligned at the Fermi level, that it could be used in a three-terminal device in which only a small gate voltage would be enough to pass through two high/low sequential switching states.…”

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A Molecular Platinum Cluster Junction: A Single-Molecule Switch

et al. 2013

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Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: El acceso a la versión del editor puede requerir la suscripción del recurso Abstract: We present a theoretical study of the electronic transport through single-molecule junctions incorporating a Pt 6 metal cluster bound within an organic framework. We show that the insertion of this molecule between a pair of electrodes leads to a fully atomicallyengineered nano-metallic device with high conductance at the Fermi level and two sequential high on/off switching states. The origin of this property can be traced back to the existence of a HOMO which consists of two degenerate and asymmetric orbitals, lying close in energy to the Fermi level of the metallic leads. Their degeneracy is broken when the molecule is contacted to the leads, giving rise to two resonances which become pinned close to the Fermi level and display destructive interference.

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Structure−Property Relationships in Redox-Gated Single Molecule Junctions − A Comparison of Pyrrolo-Tetrathiafulvalene and Viologen Redox Groups

Cited by 109 publications

References 27 publications

Single-Molecule Electrochemical Gating in Ionic Liquids

Single-Molecule Electrochemical Gating in Ionic Liquids

Electrochemical Control of Single-Molecule Conductance by Fermi-Level Tuning and Conjugation Switching

A Molecular Platinum Cluster Junction: A Single-Molecule Switch

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