Adatom Coadsorption with Three-Dimensional Cyclophanes on Ag(111)

Arrays of phthalocyanine molecules on Pb(100) are investigated with scanning tunneling microsopy. Maps of the differential conductance exhibit drastic changes as the sample voltage is being varied. Maximal conductances are observed at positions between the molecules mimicking bonding states. However, the maxima are shown to result from a superposition of non-interacting states. We expect that this effect may be observed from many other molecules.

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“…speculate that related features were previously observed between cyclophane molecules [28] and may be found in many other cases.…”

supporting

confidence: 79%

Enhanced conductance of molecular states at interstitial sites

2023

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“…Several approaches have been developed to decouple the photoactive parts from the surface and thus restore the photochemistry. − Tegeder et al employed azobenzene units with large substituents as vertical spacers (airbag approach), − but distortions of the molecule upon adsorption lead to strong suppression of the photoisomerization. Furthermore, cyclophane-type structures were used to enforce a distance between the metal surface and the photoactive part of the molecule to prevent electronic coupling . Switching or rotation of the decoupled units was not reported, however.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, cyclophane-type structures were used to enforce a distance between the metal surface and the photoactive part of the molecule to prevent electronic coupling. 30 Switching or rotation of the decoupled units was not reported, however.…”

Section: ■ Introductionmentioning

confidence: 99%

Ordered Adlayers of a Combined Lateral Switch and Rotor

et al. 2019

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Rotors and switches are elementary building blocks of molecular machines. To achieve more advanced functions, these units have to be integrated into solid-state devices, which triggered interest in mounting these functional units in well-defined geometries onto surfaces. While vertically oriented switches and rotors have been obtained by various strategies, the design of surface-parallel switches and of altitudinal rotors with an in-plane oriented rotation axis has proven to be more difficult. We here demonstrate a molecular adlayer system with highly defined geometry and laterally oriented functional groups that combines facile photoswitching and rotation. We employ a custom-designed molecule with two platforms and pillars that span an azobenzene unit between them. The molecules form well-ordered monolayers on Au(111) with the azobenzene units parallel to and above the surface. Spectroscopic data and density functional calculations suggest that in the trans configuration, at room temperature, the azo unit is freely rotating. Upon irradiation with UV light, the azo unit switches to the bent cis configuration and rotation stops. Irradiation with 430 nm restores the rotating trans state. Notably, the photochemistry is not quenched by the metal surface. This approach offers a promising strategy to operate molecular machines on metal surfaces with light, which is still a major problem in molecular nanotechnology.

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Reversible Redox‐Driven Crystallization in a Paracyclophane Monolayer at a Solid–Liquid Interface

Li,

Mali,

Hapiot

et al. 2024

Adv Funct Materials

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The development and integration of cyclophanes into future functional materials require a detailed understanding of the physicochemical principles that underlie their properties, phase behavior, and in particular the relationship between structure and function. Here, electrochemically switchable crystallization of a ferrocene‐bearing 3D Janus tecton (M‐Fc) at the interface between highly oriented pyrolytic graphite (HOPG) and an electrolyte solution is demonstrated. The M‐Fc adlayer is successfully visualized under both ambient and electrochemical conditions using scanning tunneling microscopy. Voltammetric measurements show a surface‐confined redox process for the M‐Fc modified surface that drives the phase transition between a visible 2D ordered linear phase (M‐Fc0, with ferrocene in the neutral state) and an invisible gas‐like adsorption layer with high mobility when ferrocene is oxidized, M‐Fc+, and a “square scheme” mechanism explains the data. Analogous experiments in a ferrocene‐free tecton adlayer show no phase transition and confirm that the dynamics in M‐Fc are redox‐driven. On‐surface 3D nanoarchitectures are also demonstrated by forming inclusion complexes between M‐Fc and β‐cyclodextrin and device behavior through electrochemical scanning tunneling spectroscopy (STS). These results showcase the functional potential of this class of cyclophanes, which can find use in actuators, optical crystals, and other smart materials.

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Adatom Coadsorption with Three-Dimensional Cyclophanes on Ag(111)

Cited by 6 publications

References 41 publications

Enhanced conductance of molecular states at interstitial sites

Enhanced conductance of molecular states at interstitial sites

Ordered Adlayers of a Combined Lateral Switch and Rotor

Reversible Redox‐Driven Crystallization in a Paracyclophane Monolayer at a Solid–Liquid Interface

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