Observation of Electrochemically Controlled Quantum Interference in a Single Anthraquinone‐Based Norbornylogous Bridge Molecule

Cross-conjugated molecules are known to exhibit destructive quantum interference, a property that has recently received considerable attention in single-molecule electronics. Destructive quantum interference can be understood as an antiresonance in the elastic transmission near the Fermi energy and leading to suppressed levels of elastic current. In most theoretical studies, only the elastic contributions to the current are taken into account. In this paper, we study the inelastic contributions to the current in cross-conjugated molecules and find that while the inelastic contribution to the current is larger than for molecules without interference, the overall behavior of the molecule is still dominated by the quantum interference feature. Second, an ongoing challenge for single molecule electronics is understanding and controlling the local geometry at the molecule-surface interface. With this in mind, we investigate a spectroscopic method capable of providing insight into these junctions for cross-conjugated molecules: inelastic electron tunneling spectroscopy (IETS). IETS has the advantage that the molecule interface is probed directly by the tunneling current. Previously, it has been thought that overtones are not observable in IETS. Here, overtones are predicted to be strong and, in some cases, the dominant spectroscopic features. We study the origin of the overtones and find that the interference features in these molecules are the key ingredient. The interference feature is a property of the transmission channels of the π system only, and consequently, in the vicinity of the interference feature, the transmission channels of the σ system and the π system become equally transmissive. This allows for scattering between the different transmission channels, which serves as a pathway to bypass the interference feature. A simple model calculation is able to reproduce the results obtained from atomistic calculations, and we use this to interpret these findings.

show abstract

“…The results are well-known from previous theoretical studies 30−32,36 and supported by experimental observations. 1,3,37,38 …”

Section: Resultsmentioning

confidence: 99%

Strong Overtones Modes in Inelastic Electron Tunneling Spectroscopy with Cross-Conjugated Molecules: A Prediction from Theory

Lykkebo

Gagliardi

Pecchia³

et al. 2013

ACS Nano

View full text Add to dashboard Cite

show abstract

“…[42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] Since the quantum interference effect leads to a significant difference in current (i.e., the constructive/destructive interference) through a molecular junction, the presence of the quantum interference effect was firstly elucidated from the viewpoint of current magnitude. 41,[58][59][60][61] In addition to the indirect observation of the quantum interference effect, a direct observation based on differential conductance was recently performed. 62 Figure 1 clearly exhibits a recent hot situation on the research of the quantum interference effects in molecular junctions.…”

Section: Physical Chemistry Chemical Physics Accepted Manuscriptmentioning

confidence: 99%

Molecular design of electron transport with orbital rule: toward conductance-decay free molecular junctions

Tada

Yoshizawa

2015

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

In this study, we report our viewpoint of single molecular conductance in terms of frontier orbitals. The orbital rule derived from orbital phase and amplitude is a powerful guideline for the qualitative understanding of molecular conductance in both theoretical and experimental studies. The essence of the orbital rule is the phase-related quantum interference, and on the basis of this rule a constructive or destructive pathway for electron transport is easily predicted. We have worked on the construction of the orbital rule for more than ten years and recently found from its application that π-stacked molecular junctions fabricated experimentally are in line with the concept for conductance-decay free junctions. We explain the orbital rule using benzene molecular junctions with the para-, meta- and ortho-connections and discuss linear π-conjugated chains and π-stacked molecular junctions with respect to their small decay factors in this manuscript.

show abstract

“…Previous work investigated the conductance switching effects on single molecules through electrochemical gating, [11][12][13][14][15][16][17][18][19] photo switching, [20][21][22][23][24][25][26][27] and mechanically controlling molecular configurations. [28] The few prior reports of the modulation of molecular conductance through changes in the solution pH show either a small switching effect (on/off ratio of about 2), [29] or the detection of only one state at one pH, presumably the high conductance state, while the conductance value of the second state was not detected, either because a junction could not be formed or the conductance was too low.…”

Section: Angewandte Chemiementioning

confidence: 99%

Single‐Molecule Sensing of Environmental pH—an STM Break Junction and NEGF‐DFT Approach

Smeu

Afsari

et al. 2013

Angewandte Chemie

View full text Add to dashboard Cite

We thank Vu Nguyen and Navin Rao for help with measuring the UV/Vis spectra of the dye molecules. We thank the National Science Foundation (CHE 0809838 to E.B., CHE-1058896 to M.S., CHE-1058896 to M.A.R.) and the FRQNT (M.S.) for financial support. STM = scanning tunneling microscopy, NEGF-DFT = density functional theory calculations carried out under framework of the nonequilibrium Green's function.Supporting information for this article is available on the WWW under http://dx.

show abstract

Observation of Electrochemically Controlled Quantum Interference in a Single Anthraquinone‐Based Norbornylogous Bridge Molecule

Abstract: JJG and MN-PR thank the Australian research council for support. Dr. Erwann Luais is acknowledged for the XPS experiments. Dr. Mohan Bhadbhade and Australian Synchrotron are acknowledged for their technical support.

Cited by 33 publications

References 20 publications

Strong Overtones Modes in Inelastic Electron Tunneling Spectroscopy with Cross-Conjugated Molecules: A Prediction from Theory

Strong Overtones Modes in Inelastic Electron Tunneling Spectroscopy with Cross-Conjugated Molecules: A Prediction from Theory

Molecular design of electron transport with orbital rule: toward conductance-decay free molecular junctions

Single‐Molecule Sensing of Environmental pH—an STM Break Junction and NEGF‐DFT Approach

Contact Info

Product

Resources

About