Heteroatom Effects on Quantum Interference in Molecular Junctions: Modulating Antiresonances by Molecular Design

Abstract

Controlling charge transport through molecular wires by utilizing quantum interference (QI) is a growing topic in single-molecular electronics. In this article, scanning tunneling microscopy-break junction techniques and density functional theory calculations are employed to investigate the single-molecule conductance properties of four molecules that have been specifically designed to test extended curly arrow rules (ECARs) for predicting QI in molecular junctions. Specifically, for two new isomeric 1-phenylpyrrole derivatives, the conductance pathway between the gold electrodes must pass through a nitrogen atom: this novel feature is designed to maximize the influence of the heteroatom on conductance properties and has not been the subject of prior investigations of QI. It is shown, experimentally and computationally, that the presence of a nitrogen atom in the conductance pathway increases the effect of changing the position of the anchoring group on the phenyl ring from para to meta , in comparison with biphenyl analogues. This effect is explained in terms of destructive QI (DQI) for the meta -connected pyrrole and shifted DQI for the para -connected isomer. These results demonstrate modulation of antiresonances by molecular design and verify the validity of ECARs as a simple “pen-and-paper” method for predicting QI behavior. The principles offer new fundamental insights into structure–property relationships in molecular junctions and can now be exploited in a range of different heterocycles for molecular electronic applications, such as switches based on external gating, or in thermoelectric devices.

Quantum Interference Controlled Spin-Polarized Electron Transmission in Graphene Nanoribbons

“…Exploiting quantum interference (QI) effects is another effective method for controlling electron transport. − This phenomenon has been extensively discussed in molecular junctions consisting of benzene and other π-conjugated systems, where the relative positions of anchoring groups (para or meta) affect the molecular conductance. − O’Driscoll et al. demonstrated experimentally and computationally that the presence of heteroatom in conduction pathway increase the effect of changing the anchoring group by utilizing the destructive quantum interference (DQI) in molecular junctions . Apart from the electron transport, a few of the recent reports have also witnessed the spintronic applications of QI effects.…”

“…42−44 O'Driscoll et al demonstrated experimentally and computationally that the presence of heteroatom in conduction pathway increase the effect of changing the anchoring group by utilizing the destructive quantum interference (DQI) in molecular junctions. 45 Apart from the electron transport, a few of the recent reports have also witnessed the spintronic applications of QI effects. An anomalous effect of QI in organic-radical based spin filters with the reversal of para-meta conductance was realized in our previous work 46 which is recently certified by an experimental observation.…”

Site and length dependent quantum interference and resonance in the electron transport of armchair carbon nanotube molecular junctions

“…Quantum interference (QI) in electron transport of singlemolecule devices is a phenomenon that takes place when two or more pathways of electrons are in phase or out of phase. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In clear contrast with the double-slit interference of light or electrons for which the interference patterns are observed in real space, quantum interference in electron transport studied here happens in the energy space and is typically accompanied by the increase or decrease of the transmission function in a certain energy range. [19][20][21] In particular, the case of destructive quantum interference (DQI) is characterized by a sharp dip in the transmission function, which leads to a decrease of transmission by several orders of magnitude.…”

Multiple heteroatom substitution effect on destructive quantum interference in tripodal single-molecule junctions

“…8 Additionally, the formation of intramolecular hydrogen bonds near the meta -linked benzene core can break the π-electron delocalization and the DQI between the two transmission paths. 9 These findings indicate that the molecular conductance of the molecules with DQI features is very sensitive to subtle chemical modifications, 5,10 providing sufficient space to regulate the electron transport of the molecules. Despite the present advances, the regulation of the QI effect by two or more heteroatom substitutions and the underlying mechanism is still ambiguous, which is important for future molecular devices based on heterocycle compounds.…”