Stability of Single- and Few-Molecule Junctions of Conjugated Diamines

González, M. Teresa; Díaz, Adrián; Leary, Edmund; García, Ricardo López; Herranz, M. Ángeles; Rubio‐Bollinger, Gabino; Martín, Nazario; Agraı̈t, Nicolás

doi:10.1021/ja312392q

Cited by 29 publications

(39 citation statements)

References 37 publications

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“…For each silane (Si1 to Si10) a large fraction of traces showed an abrupt jump from a lower to a higher value of conductance as the tip-substrate electrode gap widened. Although a similar effect has been observed before in other systems [31][32][33] , it is uncommon; molecular junctions do not typically demonstrate this inverted conductance behaviour. Figure 3c demonstrates this effect in individual traces.…”

Section: Si10supporting

confidence: 79%

Stereoelectronic switching in single-molecule junctions

et al. 2015

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A new intersection between reaction chemistry and electronic circuitry is emerging from the ultraminiaturization of electronic devices. Over decades chemists have developed a nuanced understanding of stereoelectronics to establish how the electronic properties of molecules relate to their conformation; the recent advent of single-molecule break-junction techniques provides the means to alter this conformation with a level of control previously unimagined. Here we unite these ideas by demonstrating the first single-molecule switch that operates through a stereoelectronic effect. We demonstrate this behaviour in permethyloligosilanes with methylthiomethyl electrode linkers. The strong σ conjugation in the oligosilane backbone couples the stereoelectronic properties of the sulfur-methylene σ bonds that terminate the molecule. Theoretical calculations support the existence of three distinct dihedral conformations that differ drastically in their electronic character. We can shift between these three species by simply lengthening or compressing the molecular junction, and, in doing so, we can switch conductance digitally between two states.

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Section: Si10supporting

confidence: 79%

Stereoelectronic switching in single-molecule junctions

et al. 2015

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“…We have observed similar behavior in amine terminated OPEs. 30 It is also clear that more pure-tunneling traces are seen in the STM, and with greater counts in the region between log(G/G 0 ) = 0 and −2. This may also be related to the speed of the measurement as the slower it is, the more the gold electrodes can retract through relaxation of the gold atoms.…”

Section: ■ Introductionmentioning

confidence: 91%

A Comprehensive Study of Extended Tetrathiafulvalene Cruciform Molecules for Molecular Electronics: Synthesis and Electrical Transport Measurements

et al. 2014

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Cruciform-like molecules with two orthogonally placed π-conjugated systems have in recent years attracted significant interest for their potential use as molecular wires in molecular electronics. Here we present synthetic protocols for a large selection of cruciform molecules based on oligo(phenyleneethynylene) (OPE) and tetrathiafulvalene (TTF) scaffolds, end-capped with acetyl-protected thiolates as electrode anchoring groups. The molecules were subjected to a comprehensive study of their conducting properties as well as their photophysical and electrochemical properties in solution. The complex nature of the molecules and their possible binding in different configurations in junctions called for different techniques of conductance measurements: (1) conducting-probe atomic force microscopy (CP-AFM) measurements on self-assembled monolayers (SAMs), (2) mechanically controlled break-junction (MCBJ) measurements, and (3) scanning tunneling microscopy break-junction (STM-BJ) measurements. The CP-AFM measurements showed structure-property relationships from SAMs of series of OPE3 and OPE5 cruciform molecules; the conductance of the SAM increased with the number of dithiafulvene (DTF) units (0, 1, 2) along the wire, and it increased when substituting two arylethynyl end groups of the OPE3 backbone with two DTF units. The MCBJ and STM-BJ studies on single molecules both showed that DTFs decreased the junction formation probability, but, in contrast, no significant influence on the single-molecule conductance was observed. We suggest that the origins of the difference between SAM and single-molecule measurements lie in the nature of the molecule-electrode interface as well as in effects arising from molecular packing in the SAMs. This comprehensive study shows that for complex molecules care should be taken when directly comparing single-molecule measurements and measurements of SAMs and solid-state devices thereof.

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“…This is assumed to be the situation when the conductance plateau is visible immediately after the gap opens (trace 2, Fig. 31 On a simple level, one can argue that a weakly bound molecule is expected to detach more frequently than a strongly bound molecule, displaying more broken plateau traces. Alternatively, no molecule may be bridging the junction initially, but one may jump into contact after a certain time.…”

Section: Mechanically Controllable Break Junctionsmentioning

confidence: 99%

“…31 Two main profiles were observed, those with uninterrupted, continuous, plateaus from beginning to end, and those with a drop in conductance below the noise level which persisted for a certain duration, termed 'broken' plateaus. 31 Two main profiles were observed, those with uninterrupted, continuous, plateaus from beginning to end, and those with a drop in conductance below the noise level which persisted for a certain duration, termed 'broken' plateaus.…”

Section: Chemical Anchoring Groupsmentioning

confidence: 99%

Incorporating single molecules into electrical circuits. The role of the chemical anchoring group

et al. 2015

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Constructing electronic circuits containing singly wired molecules is at the frontier of electrical device miniaturisation. When a molecule is wired between a pair of electrodes, the two points of contact are determined by the chemical anchoring groups, located at the ends of the molecule. At this point, when a bias is applied, electrons are channelled from a metallic environment through an extremely narrow constriction, essentially a single atom, into the molecule. The fact that this is such an abrupt change in the electron pathway makes the nature of the chemical anchoring groups critically important regarding the propagation of electrons from the electrode across the molecule. A delicate interplay of phenomena can occur when a molecule binds to the electrodes, which can produce profound differences in conductance properties depending on the anchoring group. This makes answering the question "what is the best anchoring group for single molecule studies" far from straight forward. In this review, we firstly take a look at techniques developed to 'wire-up' single molecules, as understanding their limitations is key when assessing a molecular wire's performance. We then analyse the various chemical anchoring groups, and discuss their merits and disadvantages. Finally we discuss some theoretical concepts of molecular junctions to understand how transport is affected by the nature of the chemical anchor group.

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Stability of Single- and Few-Molecule Junctions of Conjugated Diamines

Cited by 29 publications

References 37 publications

Stereoelectronic switching in single-molecule junctions

Stereoelectronic switching in single-molecule junctions

A Comprehensive Study of Extended Tetrathiafulvalene Cruciform Molecules for Molecular Electronics: Synthesis and Electrical Transport Measurements

Incorporating single molecules into electrical circuits. The role of the chemical anchoring group

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