Molecular one-dimensional topological insulators (1D TIs), which conduct through energetically low-lying topological edge states, can be extremely highly conducting and exhibit a reversed conductance ...decay, affording them great potential as building blocks for nanoelectronic devices. However, these properties can only be observed at the short length limit. To extend the length at which these anomalous effects can be observed, we design topological oligonemeraldine wires using short 1D TIs as building blocks. As the wire length increases, the number of topological states increases, enabling an increased electronic transmission along the wire; specifically, we show that we can drive over a microampere current through a single ∼5 nm molecular wire, appreciably more than what has been observed in other long wires reported to date. Calculations and experiments show that the longest oligo7emeraldine with doped topological states has over 106 enhancements in the transmission compared to its pristine form. The discovery of these highly conductive, long organic wires helps overcome a fundamental hurdle to implementing molecules in complex, nanoscale circuitry: their structures become too insulating at lengths that are useful in designing nanoscale circuits.
Single-molecule one-dimensional topological insulator (1D TI) is a class of molecular wires that exhibit increasing conductance with wire length. This unique trend is due to the coupling between the ...two low-lying topological edge states of 1D TIs described by the Su–Schrieffer–Heeger model. In principle, this quantum phenomenon within 1D TIs can be utilized to achieve long-range gating in molecular conductors. Here, we study electron transport through a single-edge state of doubly oxidized oligophenylene bis(triarylamine) to understand the effect of the edge state coupling on conductance. We find that conductance is elevated by approximately 1 order of magnitude compared to a control molecule with the same conductance pathway. Density function theory calculations further support that the increase in conductance is due to the interaction between the edge states of 1D TIs. This work demonstrates a new gating paradigm in molecular electronics, while also providing a deeper understanding of how edge states interact and affect electron transport within 1D TIs.
Remote Control of Dynamic Twistacene Chirality Bao, Si Tong; Jiang, Haoyu; Schaack, Cedric ...
Journal of the American Chemical Society,
10/2022, Letnik:
144, Številka:
41
Journal Article
Recenzirano
We report a reliable way to manipulate the dynamic, axial chirality in perylene diimide (PDI)-based twistacenes. Specifically, we reveal how chiral substituents on the imide position induce the ...helicity in a series of PDI-based twistacenes. We demonstrate that this remote chirality is able to control the helicity of flexible 4helicene subunits by UV–vis, CD spectroscopy, X-ray crystallography, and TDDFT calculations. Furthermore, we have discovered that both the chiral substituent and the solvent each has a strong impact on the sign and intensity of the CD signals, highlighting the control of the dynamic helicity in this flexible system. DFT calculations suggest that the steric interaction of the chiral substituents is the important factor in how well a particular group is at inducing a preferred helicity.
Because of their unique cyclic architectures, tunable electronic properties, and supramolecular chemistries, cycloparaphenylenes (CPPs) have the potential to act as a new class of ligands for ...coordination cages, metal–organic frameworks, and small-molecule transition-metal complexes. However, currently there is no general strategy to coordinate the cyclic framework to a variety of metal centers. We report here a general and scalable synthetic strategy to embed 2,2′-bipyridine units into the backbone of CPPs. We use this approach to synthesize a 2,2′-bipyridine-embedded 8CPP, which we show can successfully coordinate to both Pd(II) and Ru(II) metal centers. The resulting coordination complexes, a Pd(II)–nanohoop dimer and a bis(bipyridyl)ruthenium(II)-functionalized nanohoop, show unique solid-state and photophysical properties. This work provides a proof of concept for a general strategy to use nanohoops and their derivatives as a new class of ligands.
Coherent tunneling electron transport through molecular wires has been theoretically established as a temperature-independent process. Although several experimental studies have shown counter ...examples, robust models to describe this temperature dependence have not been thoroughly developed. Here, we demonstrate that dynamic molecular structures lead to temperature-dependent conductance within coherent tunneling regime. Using a custom-built variable-temperature scanning tunneling microscopy break-junction instrument, we find that oligonphenylenes exhibit clear temperature-dependent conductance. Our calculations reveal that thermally activated dihedral rotations allow these molecular wires to have a higher probability of being in a planar conformation. As the tunneling occurs primarily through π-orbitals, enhanced coplanarization substantially increases the time-averaged tunneling probability. These calculations are consistent with the observation that more rotational pivot points in longer molecular wires leads to larger temperature-dependence on conductance. These findings reveal that molecular conductance within coherent and off-resonant electron transport regimes can be controlled by manipulating dynamic molecular structure.
Here, we describe the synthesis of the hexameric macrocyclic aniline (MA6), which spontaneously assembles into coaxially conductive organic wires in its oxidized and acidified emeraldine salt (ES) ...form. Electrical measurements reveal that ES-MA6 exhibits high electrical conductivity (7.5 × 10–2 S·cm–1) and that this conductivity is acid–base responsive. Single-crystal X-ray crystallography reveals that ES-MA6 assembles into well-defined trimeric units that then stack into nanotubes with regular channels, providing a potential route to synthetic nanotubes that are leveraged for ion or small molecule transport. Ultraviolet–visible–near-infrared absorbance spectroscopy and electron paramagnetic spectroscopy showcase the interconversion between acidic (conductive) and basic (insulating) forms of these macrocycles and how charge carriers are formed through protonation, giving rise to the experimentally observed high electrical conductivity.
Addition of the bipyridyl‐embedded cycloparaphenylene nanohoop bipy9CPP to Fe{H2B(pyz)2} (pyz=pyrazolyl) produces the distorted octahedral complex Fe(bipy9CPP){H2B(pyz)2}2 (1). The molecular ...structure of 1 shows that the nanohoop ligand contains a non‐planar bipy unit. Magnetic susceptibility measurements indicate spin‐crossover (SCO) behaviour with a T1/2 of 130 K, lower than that of 160 K observed with the related compound Fe(bipy){H2B(pyz)2}2 (2), which contains a conventional bipy ligand. A computational study of 1 and 2 reveals that the curvature of the nanohoop leads to the different SCO properties, suggesting that the SCO behaviour of iron(II) can be tuned by varying the size and diameter of the nanohoop.
Addition of a bipyridyl embedded cycloparaphenylene (CPP) nanohoop to Fe{H2B(pyz)2} (pyz=pyrazolyl) produces the distorted octahedral complex Fe(bipy9CPP){H2B(pyz)2}2. Its spin‐crossover (SCO) properties are strongly influenced by a distortion associated with the nanohoop, implying that variations in nanohoop size may provide a way of tuning the SCO properties of iron compounds.
Addition of the bipyridyl‐embedded cycloparaphenylene nanohoop bipy9CPP to Fe{H2B(pyz)2} (pyz=pyrazolyl) produces the distorted octahedral complex Fe(bipy9CPP){H2B(pyz)2}2 (1). The molecular ...structure of 1 shows that the nanohoop ligand contains a non‐planar bipy unit. Magnetic susceptibility measurements indicate spin‐crossover (SCO) behaviour with a T1/2 of 130 K, lower than that of 160 K observed with the related compound Fe(bipy){H2B(pyz)2}2 (2), which contains a conventional bipy ligand. A computational study of 1 and 2 reveals that the curvature of the nanohoop leads to the different SCO properties, suggesting that the SCO behaviour of iron(II) can be tuned by varying the size and diameter of the nanohoop.
Addition of a bipyridyl embedded cycloparaphenylene (CPP) nanohoop to Fe{H2B(pyz)2} (pyz=pyrazolyl) produces the distorted octahedral complex Fe(bipy9CPP){H2B(pyz)2}2. Its spin‐crossover (SCO) properties are strongly influenced by a distortion associated with the nanohoop, implying that variations in nanohoop size may provide a way of tuning the SCO properties of iron compounds.
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