Beyond Simple Structure–Function Relationships: The Interplay of Geometry, Electronic Structure, and Molecule/Electrode Coupling in Single-Molecule Junctions

Abstract

Structure–function relationships constitute an important tool to investigate the fundamental principles of molecular electronics. Most commonly, this involves identifying a potentially important molecular structural element, followed by designing and synthesizing a set of related organic molecules, and finally interpretation of their experimental and/or computational quantum transport properties in the light of this structural element. Though this has been extremely powerful in many instances, we demonstrate here the common need for more nuanced relationships even for relatively simple structures, using both experimental and computational results for a series of stilbene derivatives as a case study. In particular, we show that the presence of multiple competing and subtle structural factors can combine in unexpected ways to control quantum transport in these molecules. Our results clarify the reasons for previous widely varying and often contradictory reports on charge transport in stilbene derivatives and highlight the need for refined multidimensional structure–property relationships in single-molecule electronics.

Direct biomolecule discrimination in mixed samples using nanogap-based single-molecule electrical measurement

“…5 e. The electronic structures of the electrodes affect single-molecule conductance. Electronic structure variation due to molecular adsorption on the electrode surface or different geometries of the electrodes may affect single-molecule signals 42 – 45 . A wide variety of machine learning methods have been developed in recent years.…”

Light-driven modulation of electrical conductance with photochromic switches: bridging photochemistry with optoelectronics

“…A recent article by Monti et al describes some important factors that affect the alteration in the conductance on isomerization, such as a change in tunnelling barrier width, and disruption of the conjugation due to the twisted nature of the cis geometry. 40 On the other hand, the photochromic nature of the azobenzene can be tuned by incorporating different heterocycles 41 or by changing the substitutions on the aryl rings. 42 Both azobenzenecontaining organic polymers and metal-containing systems have been used as photoswitchable conductors.…”

The effect of weak π–π interactions on single-molecule electron transport properties of the tetraphenylethene molecule and its derivatives: a first-principles study

“…17,18 Nevertheless, the calculated frontier orbital energy levels show that the HOMO energy level is closer to the Fermi level of gold electrodes than the LUMO energy level, which indicates that the conductance properties of the HPB-SM molecular system is generally dominated by the HOMO. [19][20][21][22] In addition, the nodal surfaces of the HOMO will not be conducive to electron transport to some extent; therefore, it is necessary to deeply analyze the relationship between the innermost p delocalized molecular orbital and molecular electronic conductance. In order to explore the electron transport mechanism of V-shaped structures involving non-covalent weak p-p interactions, we need to further calculate and simulate the electron transport properties of the related molecular systems to clarify the existence of the throughspace electron transport pathway and understand its corresponding conductance transport mechanism.…”