Unbalanced 2D Chiral Crystallization of Pentahelicene Propellers and Their Planarization into Nanographenes

Voigt, J.; Roy, Myriam; Baljozović, Miloš; Wäckerlin, Christian; Coquerel, Yoann; Gingras, Marc; Ernst, Karl‐Heinz

doi:10.1002/chem.202101223

Cited by 9 publications

(13 citation statements)

References 36 publications

(35 reference statements)

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“…More recently, Ernst et al have used STM to image the structures formed by trispentahelicene enantiomers on Au(111). 25 In that system, the adsorbates are large enough that their absolute chirality can be determined from the STM images. This reveals ordered 2D domains in which the ratio of enantiomers is 2:1, as observed in this work.…”

Section: Resultsmentioning

confidence: 99%

“…A recent study by Ernst et al has identified a 2D system that forms an ordered structure with unequal numbers of enantiomers in each unit cell . Trispentahelicene has a structure mimicking a three bladed propeller and exists in enantiomeric forms labeled M- and P-.…”

mentioning

confidence: 99%

“…A recent study by Ernst et al has identified a 2D system that forms an ordered structure with unequal numbers of enantiomers in each unit cell. 25 Trispentahelicene has a structure mimicking a three bladed propeller and exists in enantiomeric forms labeled M- and P-. The STM study of a racemic mixture of trispentahelicene propellers adsorbed on Au(111) revealed that the molecules lie roughly parallel to the Au(111) surface and that the absolute chirality of each molecule is discernible from the STM images.…”

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confidence: 99%

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Molecular Origins of Chiral Amplification on an Achiral Surface: 2D Monolayers of Aspartic Acid on Cu(111)

et al. 2023

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Recent experiments have demonstrated an intriguing phenomenon in which adsorption of a nonracemic mixture of aspartic acid (Asp) enantiomers onto an achiral Cu(111) metal surface leads to autoamplification of surface enantiomeric excess, ee s , to values well above those of the impinging gas mixtures, ee g . This is particularly interesting because it demonstrates that a slightly nonracemic mixture of enantiomers can be further purified simply by adsorption onto an achiral surface. In this work, we seek a deeper understanding of this phenomena and apply scanning tunneling microscopy to image the overlayer structures formed by mixed monolayers of d - and l -Asp on Cu(111) over the full range of surface enantiomeric excess; ee s = −1 (pure l -Asp) through ee s = 0 (racemic dl -Asp) to ee s = 1 (pure d -Asp). Both enantiomers of three chiral monolayer structures are observed. One is a conglomerate (enantiomerically pure), another is a racemate (equimolar mixture of d - and l -Asp); however, the third structure accommodates both enantiomers in a 2:1 ratio. Such solid phases of enantiomer mixtures with nonracemic composition are rare in 3D crystals of enantiomers. We argue that, in 2D, the formation of chiral defects in a lattice of one enantiomer is easier than in 3D, simply because the stress associated with the chiral defect in a 2D monolayer of the opposite enantiomer can be dissipated by strain into the space above the surface.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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Molecular Origins of Chiral Amplification on an Achiral Surface: 2D Monolayers of Aspartic Acid on Cu(111)

et al. 2023

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“…Alternatively, the Co-DPP may form an enantiopure self-assembly structure in such high dense coverage. A formation of a random mixture of the two chiral enantiomers may also lead to the disordered phase appearing achiral in STM …”

Section: Resultsmentioning

confidence: 99%

“…A formation of a random mixture of the two chiral enantiomers may also lead to the disordered phase appearing achiral in STM. 52 In order to understand the formation of chiral Co-DPP configurations, we investigate in more detail their appearances in STM images and their structure from DFT calculations (Figure 2). On the surface, isolated molecules are only found adsorbed at step edges, and they appear also as L-and R-Co-DPP as shown in Figure 2a.…”

Section: Stmmentioning

confidence: 99%

Coverage-Induced Chiral Transition of Co(II)-5,15-Diphenylporphyrin Self-Assemblies on Cu(111)

Xiang

Schneider

2022

J. Phys. Chem. C

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Wallach's rule elucidates the phenomenon that racemic crystals are denser than their enantiopure form. The rule applies to most chiral molecular systems with the exception of some amino acids. However, it remains unclear whether Wallach's rule applies to the special but important class of chiral systems where chirality is induced by the adsorption of prochiral molecules on substrates. In this work, we show that the exemplary system, Cobalt(II)-diphenylporphyrin (Co-DPP) on Cu (111), follows Wallach's rule. Co-DPP assumes chiral isomers upon adsorption and shows a phase transition from an enantiopure linear chain structure to a racemic close-packed structure with increasing molecular density. Density functional theory (DFT) reveals that the chiral recognition, separation, and phase mixture of Co-DPP are due to the synergistic mechanism of substrate−molecule and molecule−molecule interactions.

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Multihelicenic Platforms from Halogenated Helicenes and Related Precursors

Roy¹,

Gingras²

2022

Helicenes

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Unbalanced 2D Chiral Crystallization of Pentahelicene Propellers and Their Planarization into Nanographenes

Abstract: Supporting information for this article is given via a link at the end of the document.

Cited by 9 publications

References 36 publications

Molecular Origins of Chiral Amplification on an Achiral Surface: 2D Monolayers of Aspartic Acid on Cu(111)

Molecular Origins of Chiral Amplification on an Achiral Surface: 2D Monolayers of Aspartic Acid on Cu(111)

Coverage-Induced Chiral Transition of Co(II)-5,15-Diphenylporphyrin Self-Assemblies on Cu(111)

Multihelicenic Platforms from Halogenated Helicenes and Related Precursors

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