Molecular Chirality at Surfaces

Ernst, Karl‐Heinz

doi:10.1002/9783527680580.ch42

Cited by 9 publications

(7 citation statements)

References 240 publications

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“…1 Work is not limited to the behavior of adsorbed chiral molecules on high-symmetry surfaces and ranges from the chiral self-organization of simple achiral molecules on achiral surfaces, to the enantiospecific restructuring of intrinsically chiral surfaces induced by chiral adsorbates. 1,2 With their low reactivity, copper surfaces provide ideal substrates on which to study the propagation of chirality from the molecular level to the mesoscopic level and the formation of long-range chiral networks. In recent years, the behavior of several simple amino acids on the low-index Cu{100} and Cu{110} surfaces has been studied extensively.…”

Section: ■ Introductionmentioning

confidence: 99%

Spontaneous Local Symmetry Breaking: A Conformational Study of Glycine on Cu{311}

et al. 2015

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Understanding the interplay between intrinsic molecular chirality and chirality of the bonding footprint is crucial in exploiting enantioselectivity at surfaces. As such, achiral glycine and chiral alanine are the most obvious candidates if one is to study this interplay on different surfaces. Here, we have investigated the adsorption of glycine on Cu{311} using reflection–absorption infrared spectroscopy, low-energy electron diffraction, temperature-programmed desorption, and first-principles density-functional theory. This combination of techniques has allowed us to accurately identify the molecular conformations present under different conditions and discuss the overlayer structure in the context of the possible bonding footprints. We have observed coverage-dependent local symmetry breaking, with three-point bonded glycinate moieties forming an achiral arrangement at low coverages, and chirality developing with the presence of two-point bonded moieties at high coverages. Comparison with previous work on the self-assembly of simple amino acids on Cu{311} and the structurally similar Cu{110} surface has allowed us to rationalize the different conditions necessary for the formation of ordered chiral overlayers

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Section: ■ Introductionmentioning

confidence: 99%

Spontaneous Local Symmetry Breaking: A Conformational Study of Glycine on Cu{311}

et al. 2015

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“…One example is the odor of limonene enantiomers. R‐(+)‐limonene, which appears in most citrus oils, smells like orange fruit, while S‐(–)‐limonene, which is abundant in conifer needles, smells like turpentine . Such effects are most likely related to interactions and signal transductions at the interface on the biological membrane that has receptors sensitive to chiral molecular structures and interactions.…”

Section: Introductionmentioning

confidence: 99%

“…For example, one of the simplest cases is that the CH 2 in the ethanol (CH 3 CH 2 OH) molecule is prochiral, as it can be converted into CH 3 CHDOH when one of the hydrogen atoms on the CH 2 group is replaced by a deuterium atom (D). Desymmetrization steps include reactions or interactions with a chiral induction agent, ligand, or even surfaces . Controlled transformation between the prochiral and the chiral molecular structures has been a significant part of the art of organic stereochemistry .…”

Section: Introductionmentioning

confidence: 99%

Intrinsic Chirality and Prochirality at Air/R‐(+)‐ and S‐(–)‐Limonene Interfaces: Spectral Signatures With Interference Chiral Sum‐Frequency Generation Vibrational Spectroscopy

Zhang

Wei

et al. 2014

Chirality

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We report in this work detailed measurements of the chiral and achiral sum-frequency vibrational spectra in the C-H stretching vibration region (2800-3050 cm(-1)) of the air/liquid interfaces of R-(+)-limonene and S-(-)-limonene, using the recently developed high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BB-SFG-VS). The achiral SFG spectra of R-limonene and S-limonene, as well as the RS racemic mixture (50/50 equal amount mixture), show that the corresponding molecular groups of the R and S enantiomers are with the same interfacial orientations. The interference chiral SFG spectra of the limonene enantiomers exhibit a spectral signature from the chiral response of the Cα-H stretching mode, and a spectral signature from the prochiral response of the CH(2) asymmetric stretching mode, respectively. The chiral spectral feature of the Cα-H stretching mode changes sign from R-(+)-limonene to S-(-)-limonene surfaces, and disappears for the RS racemic mixture surface. While the prochiral spectral feature of the CH(2) asymmetric stretching mode is the same for R-(+)-limonene and S-(-)-limonene surfaces, and also surprisingly remains the same for the RS racemic mixture surface. Therefore, the structures of the R-(+)-limonene and the S-(-)-limonene at the liquid interfaces are nevertheless not mirror images to each other, even though the corresponding groups have the same tilt angle from the interfacial normal, i.e., the R-(+)-limonene and the S-(-)-limonene at the surface are diastereomeric instead of enantiomeric. These results provide detailed information in understanding the structure and chirality of molecular interfaces and demonstrate the sensitivity and potential of SFG-VS as a unique spectroscopic tool for chirality characterization and chiral recognition at the molecular interface.

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“…Although chirality is a central and powerful concept in chemistry ever since its introduction by Pasteur, the notion of “surface chirality” and its fascinating consequences were explored only recently. 14,15 For a 2D, prochiral molecule with a 3D inversion center like indigo or quinacridone, which is inclined with respect to a high symmetry direction of the surface, the 2D-mirror operation about this axis will leave the adsorption configuration unchanged but switch the handedness of the molecule on the surface. Therefore, the two adsorption configurations depicted in Figure 1 are the energetically equivalent ones for the two different 2D-enantiomers.…”

Section: Introductionmentioning

confidence: 99%

Quinacridone on Ag(111): Hydrogen Bonding versus Chirality

et al. 2014

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Quinacridone (QA) has recently gained attention as an organic semiconductor with unexpectedly high performance in organic devices. The strong intermolecular connection via hydrogen bonds is expected to promote good structural order. When deposited on a substrate, another relevant factor comes into play, namely the 2D-chirality of the quinacridone molecules adsorbed on a surface. Scanning tunneling microscopy (STM) images of monolayer quinacridone on Ag(111) deposited at room temperature reveal the formation of quasi-one-dimensional rows of parallel quinacridone molecules. These rows are segmented into short stacks of a few molecules in which adjacent, flat-lying molecules of a single handedness are linked via hydrogen bonds. After annealing to a temperature of T = 550–570 K, which is close to the sublimation temperature of bulk quinacridone, the structure changes into a stacking of heterochiral quinacridone dimers with a markedly different intermolecular arrangement. Electron diffraction (LEED) and photoelectron emission microscopy (PEEM) data corroborate the STM findings. These results illustrate how the effects of hydrogen bonding and chirality can compete and give rise to very different (meta)stable structures of quinacridone on surfaces.

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Molecular Chirality at Surfaces

Cited by 9 publications

References 240 publications

Spontaneous Local Symmetry Breaking: A Conformational Study of Glycine on Cu{311}

Spontaneous Local Symmetry Breaking: A Conformational Study of Glycine on Cu{311}

Intrinsic Chirality and Prochirality at Air/R‐(+)‐ and S‐(–)‐Limonene Interfaces: Spectral Signatures With Interference Chiral Sum‐Frequency Generation Vibrational Spectroscopy

Quinacridone on Ag(111): Hydrogen Bonding versus Chirality

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