Intramolecular Torsion Based Molecular Switch Functionality Enhanced in π-Conjugated Oligomolecules by a π-Conjugated Pendant Group

Dou, Kaiying; Sarkar, Abir De; Wang, C. L.; Zhang, R. Q.

doi:10.1021/jp202609x

Cited by 6 publications

(6 citation statements)

References 37 publications

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“…This large transmission difference by torsional control of the endgroups has previously been suggested as a means to achieve electronic functionality in polyynebased molecular devices. [106][107][108][109] The suppression happens as the HOMO and HOMO-1 (LUMO and LUMO+1) become degenerate at ~90° (see Figure 4), and consequently the transmission through the helical p-systems is fully suppressed. Rather than due to two orthogonal p-systems, we consider the low transmission at 90° as a consequence of destructive quantum interference effect due to near-degeneracy of two helical orbitals with opposite symmetries.…”

Section: Polyynic Carbon Wiresmentioning

confidence: 99%

Three Distinct Torsion Profiles of Electronic Transmission through Linear Carbon Wires

2020

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The one-dimensional carbon allotrope carbyne, a linear chain of sp-hybridized carbon atoms, is predicted to exist in a polyynic and a cumulenic structure. While molecular forms of carbyne have been extensively characterized, the structural nature is hard to determine for many linear carbon wires that are made in-situ during pulling experiments. Here, we show that cumulenes and polyynes have distinctively different low-bias conductance profiles under axial torsion. We analyze the change of the electronic structure, Landauer transmission, and ballistic current density of the three types of closed-shell molecular carbynes as a function of the torsion angle. Both polyynic, odd-carbon cumulenic, and even-carbon cumulenic carbon wires exhibit helical frontier molecular orbitals when the end-groups are not in a co-planar configuration. This helical conjugation effect gives rise to strong ring current patterns around the linear wires. Only the transmission of even-carbon polyynic wires follows the well-known cosine-squared law with axial torsion that is also seen in biphenyl-type systems. Notably, the transmission of even-carbon cumulenic carbon wires rises with axial torsion from co-planar towards perpendicular orientation of the end-groups. The three distinct transmission profiles of polyynes, odd-carbon cumulenes, and even-carbon cumulenes may allow for experimental identification of the structural nature of linear carbon wires. Their different electron transport properties under axial torsion furthermore underline that, in the molecular limit of carbyne, three different subclasses of linear carbon wires exist. File list (3)download file view on ChemRxiv torsion_chemrxiv3.pdf (6.17 MiB) download file view on ChemRxiv SI_chemrxiv3.pdf (9.24 MiB) download file view on ChemRxiv files.zip (21.38 MiB)

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Section: Polyynic Carbon Wiresmentioning

confidence: 99%

Three Distinct Torsion Profiles of Electronic Transmission through Linear Carbon Wires

2020

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“…The electronic coupling between different molecular building blocks is essential for the design and fabrication of molecular materials and devices. − In the current stage, most molecular electronic devices select molecules with a planar structure as building blocks, − which is mainly because the charge transport through the twisted molecular wires significantly decreases with the increasing twist angle owing to the reduction of inter-ring π-orbital overlap. − However, the delocalized electronic structure and strong coupling between building blocks also bring huge challenges for the rational and modularized tuning of charge transport in individual building blocks. To minimize the delocalization for the modularized fabrication of molecular devices, a large twist angle is typically employed to reduce the inter-ring coupling. − Although the highly twisted molecular wires exhibit a weaker charge-transport ability owing to the weak π-orbital overlap, − the weak coupling between each block of molecules with a large inter-ring twist angle results in a highly localized electronic structure.…”

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confidence: 99%

Modularized Tuning of Charge Transport through Highly Twisted and Localized Single-Molecule Junctions

Chen

Liu

et al. 2019

J. Phys. Chem. Lett.

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Although most molecular electronic devices and materials consist of a backbone with a planar structure, twisted molecular wires with reduced inter-ring π-orbital overlap offer a unique opportunity for the modularized fabrication of molecular electronic devices. Herein we investigate the modularized tuning of the charge transport through the localized molecules by designing highly twisted molecules and investigating their single-molecule charge transport using the scanning tunneling microscopy break junction technique. We find that the anthracenediyl-core molecule with a 90° inter-ring twist angle shows an unexpectedly high conductance value, which is five times higher than that of the phenylene-core molecule with a similar configuration, whereas the conductance of the delocalized planar molecule with an anthracenediyl core or a phenylene core is almost the same. Theoretical calculations revealed that highly twisted angles result in weak interactions between molecular building blocks, for which molecule orbitals are separated into localized blocks, which offers the chance for the modularized tuning of every single block. Our findings offer a new strategy for the design of future molecular devices with a localized electronic structure.

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“…In particular, theoretical calculations have predicted the temperature-dependent torsion of the biphenyl skeleton and conformation-dependent charge transport through the biphenyl molecule . This prediction strongly suggests the potential use of realizing the switching function with proper design of the biphenyl structures . In the case of terphenyl, there are two different dihedral angles between the outer two benzene rings at each end: one is zero, while the other is almost two times as large as that between the benzene rings in the biphenyl (Figure , top).…”

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confidence: 99%

“…39 This prediction strongly suggests the potential use of realizing the switching function with proper design of the biphenyl structures. 40 In the case of terphenyl, there are two different dihedral angles between the outer two benzene rings at each end: one is zero, while the other is almost two times as large as that between the benzene rings in the biphenyl (Figure 1, top).…”

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confidence: 99%

Stereoelectronic Effect-Induced Conductance Switching in Aromatic Chain Single-Molecule Junctions

et al. 2017

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Biphenyl, as the elementary unit of organic functional materials, has been widely used in electronic and optoelectronic devices. However, over decades little has been fundamentally understood regarding how the intramolecular conformation of biphenyl dynamically affects its transport properties at the single-molecule level. Here, we establish the stereoelectronic effect of biphenyl on its electrical conductance based on the platform of graphene-molecule single-molecule junctions, where a specifically designed hexaphenyl aromatic chain molecule is covalently sandwiched between nanogapped graphene point contacts to create stable single-molecule junctions. Both theoretical and temperature-dependent experimental results consistently demonstrate that phenyl twisting in the aromatic chain molecule produces different microstates with different degrees of conjugation, thus leading to stochastic switching between high- and low-conductance states. These investigations offer new molecular design insights into building functional single-molecule electrical devices.

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Intramolecular Torsion Based Molecular Switch Functionality Enhanced in π-Conjugated Oligomolecules by a π-Conjugated Pendant Group

Cited by 6 publications

References 37 publications

Three Distinct Torsion Profiles of Electronic Transmission through Linear Carbon Wires

Three Distinct Torsion Profiles of Electronic Transmission through Linear Carbon Wires

Modularized Tuning of Charge Transport through Highly Twisted and Localized Single-Molecule Junctions

Stereoelectronic Effect-Induced Conductance Switching in Aromatic Chain Single-Molecule Junctions

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