Coverage and Enantiomeric Excess Dependent Enantiomorphism in Two-Dimensional Molecular Crystals

Parschau, Manfred; Fasel, Román; Ernst, Karl‐Heinz

doi:10.1021/cg701100r

Cited by 74 publications

(98 citation statements)

References 39 publications

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“…20d has a higher density than the heterochiral phase observed. Molecular modeling calculations favor the enantiopure phase by 1 kJ mol À1 over the racemate l/r phase [125]. However, deposition at room temperature leads to a disordered monolayer due to high mobility.…”

Section: Racemic Mixturesmentioning

confidence: 98%

“…A formation of the enantiomorphous (4-1, 2 4) phase is not observed for the racemic mixture, which saturates in a c(2 Â 4) structure [119]. Other than tartaric acid, racemic heptahelicene ( [7]H; C 30 H 18 ) forms completely different structures from the pure enantiomers on Cu(111) [122][123][124][125]. This aromatic hydrocarbon is basically a construct of seven orthoannulated C6 rings and therefore an example of a chiral molecule without a stereogenic center (Fig.…”

Section: Racemic Mixturesmentioning

confidence: 99%

“…For [7]H on Cu(111), calculations favored heterochiral dimers and heterochiral small clusters [125]. A similar apolar intrinsically chiral molecule, the aromatic 5,6,11,12-tetraphenyltetracene (rubrene, Fig.…”

Section: Racemic Mixturesmentioning

confidence: 99%

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Molecular chirality at surfaces

Ernst

2012

Physica Status Solidi (b)

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With the adsorption of larger molecules being increasingly tackled by surface scientists, the aspect of chirality often plays a role. This paper gives a topical review of molecular chirality at surfaces and gives a phenomenological overview of different aspects of adsorption and self‐assembly of chiral and prochiral molecules and the principles of mirror‐symmetry breaking at a surface. After a brief introduction into the history of molecular chirality and the important role it played for understanding the spatial structure of molecules, definitions of chirality are presented. Topics treated here are principle ways to create single chiral adsorbates, chiral ensembles, and monolayers by achiral molecules, adsorption of intrinsically chiral molecules at achiral and chiral surfaces, long‐range symmetry breaking in two‐dimensional (2D) crystals due to additional chiral bias, chiral restructuring of solid surfaces under the influence of chiral molecules, switching the handedness of adsorbates, and chirality at the liquid/air interface. An outlook onto further potential research directions and recommendations for further reading, including nonsurface‐related sources of chiral topics completes this paper.

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Section: Racemic Mixturesmentioning

confidence: 98%

Section: Racemic Mixturesmentioning

confidence: 99%

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Molecular chirality at surfaces

Ernst

2012

Physica Status Solidi (b)

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221

264

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“…Figure 4 presents STM images for the racemate at medium coverage and saturation. Overall, three pairs of enantiomorphous structures, denoted as ε/δ, λ /ρ and λ/ρ, are observed [37]. All these adlattices successively form with increasing global coverage and have a common feature, i.e., the molecules are aligned in zigzag double rows (see insets of Fig.…”

Section: Helical Aromatesmentioning

confidence: 98%

Intermediate structures in two-dimensional molecular self-assembly

Ernst

2010

Front. Phys. China

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We discuss the occurrence of transition structures observed in molecular self-assembly at surfaces. The increasing surface coverage transitions from low coverage structures to high coverage structures are a common phenomenon. However, often observed and not perfectly understood is the formation of intermediate structures, sometimes with lower lateral density than the initial phase. We will present different examples from our recent work and discuss the possible mechanisms of intermediate phase formation. In addition, we present intermediate structures occurring due to temperature-controlled reversible phase transitions.

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“…and λ/ρ, successively form with increasing coverage. [14] All these adlattices have a common feature in that the molecules are aligned in zigzag double rows. The lattice structure of the λ/ρ phase has been determined via high-resolution STM in combination with extended Hückel simulations as well as MMC (Fig.…”

Section: Racemic Crystals Versus Conglomeratesmentioning

confidence: 99%

Expression and Amplification of Chirality in Two-Dimensional Molecular Crystals

Ernst¹

2008

Chimia

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Expression and amplification of chirality in two-dimensional molecular crystals Expression and amplification of chirality in two-dimensional molecular crystals Abstract Chirality can be bestowed onto achiral surfaces by adsorption of chiral molecules. This offers a good opportunity to study two-dimensional chiral crystallization phenomena, like lateral resolution of enantiomers or the transfer of handedness from single molecules into mesoscopic ensembles with high resolution by scanning probe microscopy. Induction of homochirality on surfaces via cooperatively amplified interactions in molecular monolayers is a new phenomenon of supramolecular surface chirality. Prochiral molecules will turn into either handedness upon adsorption, but doping with intrinsically chiral molecules breaks this symmetry and induces homochirality. A similar effect is induced by a small enantiomeric excess. The excess molecules provide the chiral bias that becomes amplified into single lattice chirality. Expression and Amplification of Chirality in Tw o-Dimensional Molecular CrystalsKarl-Heinz Ernst * Dedicated to Professor Jack D. Dunitz on the occasion of his 85 th birthdayAbstract: Chirality can be bestowed onto achiral surfaces by adsorption of chiral molecules. This offers a good opportunity to study two-dimensional chiral crystallization phenomena, like lateral resolution of enantiomers or the transfer of handedness from single molecules into mesoscopic ensembles with high resolution by scanning probe microscopy. Induction of homochirality on surfaces via cooperatively amplified interactions in molecular monolayers is a new phenomenon of supramolecular surface chirality. Prochiral molecules will turn into either handedness upon adsorption, but doping with intrinsically chiral molecules breaks this symmetry and induces homochirality. A similar effect is induced by a small enantiomeric excess. The excess molecules provide the chiral bias that becomes amplified into single lattice chirality.

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Coverage and Enantiomeric Excess Dependent Enantiomorphism in Two-Dimensional Molecular Crystals

Cited by 74 publications

References 39 publications

Molecular chirality at surfaces

Molecular chirality at surfaces

Intermediate structures in two-dimensional molecular self-assembly

Expression and Amplification of Chirality in Two-Dimensional Molecular Crystals

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