Spontaneous resolution, whence and whither: from enantiomorphic solids to chiral liquid crystals, monolayers and macro- and supra-molecular polymers and assemblies

Pérez‐García, Lluïsa; Amabilino, David B.

doi:10.1039/b610714a

Cited by 417 publications

(264 citation statements)

References 170 publications

(178 reference statements)

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“…The nanoscale control of chiral molecular assembly at surfaces is of central importance in fields as diverse as chiral separations, 1,2 heterogeneous enantioselective catalysis, 3,4 plasmonics, 5 chiroptical switching 6,7 and biosensors. 8 In all cases, the surface function is profoundly influenced by how individual enantiomers organize at the local and the global level, therefore the outstanding problem in the field is to understand the factors that drive enantiomer assembly and segregation.…”

Section: Introductionmentioning

confidence: 99%

Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: bitartrate on Cu(110)

Darling

Forster

Lin

et al. 2017

Phys. Chem. Chem. Phys.

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Local or global ordering of chiral molecules at a surface is a key step in both chiral separation and heterogeneous enantioselective catalysis. Using density functional theory and scanning probe microscopy results, we find that the accepted structural model for the well known bitartrate on Cu(110) chiral system cannot account for the chiral segregation observed. Instead, we show that this strongly bound, chiral adsorbate changes its adsorption footprint in response to the local environment. The flexible adsorption geometry allows bitartrate to form stable homochiral trimer chains in which the central molecule restructures from a rectangular to an oblique footprint, breaking its internal hydrogen bonds in order to form strong intermolecular hydrogen bonds to neighbouring adsorbates. Racemic structures containing mixed enantiomers do not form strong hydrogen bonds, providing the thermodynamic driving force for the chiral separation that is observed experimentally. This result shows the importance of considering the dynamical response of molecular adsorption footprints at the surface in directing chiral assembly and segregation. The ability of strongly-chemisorbed enantiomers to change footprint depending on the local adsorption environment indicates that supramolecular assemblies at surfaces may exhibit more complex dynamical behaviour than hitherto suspected, which, ultimately, could be tailored to lead to environment and stimuli-responsive chiral surfaces.

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Section: Introductionmentioning

confidence: 99%

Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: bitartrate on Cu(110)

Darling

Forster

Lin

et al. 2017

Phys. Chem. Chem. Phys.

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“…mirror symmetry | parity symmetry | topological defects | chiral defects T he emergence of chirality from achiral systems poses fundamental questions about which we have limited mechanistic understanding (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). When the chiral symmetry of an achiral system is broken, a handedness is established, and materials with different handedness commonly exhibit distinct and useful properties (10)(11)(12)(13)(14) relevant for applications ranging from chemical sensors (15,16) to photonics (17)(18)(19).…”

mentioning

confidence: 99%

Chiral structures from achiral liquid crystals in cylindrical capillaries

Jeong

Kang

Davidson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

105

102

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We study chiral symmetry-broken configurations of nematic liquid crystals (LCs) confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls (i.e., perpendicular surface alignment). Interestingly, achiral nematic LCs with comparatively small twist elastic moduli relieve bend and splay deformations by introducing twist deformations. In the resulting twisted and escaped radial (TER) configuration, LC directors are parallel to the cylindrical axis near the center, but to attain radial orientation near the capillary wall, they escape along the radius through bend and twist distortions. Chiral symmetry-breaking experiments in polymercoated capillaries are carried out using Sunset Yellow FCF, a lyotropic chromonic LC with a small twist elastic constant. Its director configurations are investigated by polarized optical microscopy and explained theoretically with numerical calculations. A rich phenomenology of defects also arises from the degenerate bend/twist deformations of the TER configuration, including a nonsingular domain wall separating domains of opposite twist handedness but the same escape direction and singular point defects (hedgehogs) separating domains of opposite escape direction. We show the energetic preference for singular defects separating domains of opposite twist handedness compared with those of the same handedness, and we report remarkable chiral configurations with a double helix of disclination lines along the cylindrical axis. These findings show archetypally how simple boundary conditions and elastic anisotropy of confined materials lead to multiple symmetry breaking and how these broken symmetries combine to create a variety of defects.mirror symmetry | parity symmetry | topological defects | chiral defects T he emergence of chirality from achiral systems poses fundamental questions about which we have limited mechanistic understanding (1-11). When the chiral symmetry of an achiral system is broken, a handedness is established, and materials with different handedness commonly exhibit distinct and useful properties (10-14) relevant for applications ranging from chemical sensors (15, 16) to photonics (17-19). To date, considerable effort has been expended to control handedness in materials (for example, by chiral separation of racemic mixtures or chiral amplification of small enantiomeric imbalances) (1,8,(20)(21)(22). Recently and in a different vein, identification and elucidation of pathways by which achiral building blocks spontaneously organize to create chiral structures have become an area of active study. Examples of these pathways include packing with multiple competing length scales (8-10, 23, 24), reconfiguration through mechanical instabilities of periodic structures (20,25,26), and helix formation of flexible cylinders through inter-and intracylinder interactions (27,28). In addition, the system of a broken chiral symmetry often consists of domains of opposite handedness with defects separating the domains.Liquid crystals (LCs) are soft materials composed ...

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“…Not all examples given are illustrated with figures, some examples are covered in more detail and others only very briefly, in which it might be necessary to consult the original literature to obtain a more detailed picture of the particular case. There are several reviews that have covered various aspects of the field, in part with a different perspective [9][10][11][12][13][14][15][16][17][18].…”

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Molecular chirality at surfaces

Ernst

2012

Physica Status Solidi (b)

218

257

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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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Spontaneous resolution, whence and whither: from enantiomorphic solids to chiral liquid crystals, monolayers and macro- and supra-molecular polymers and assemblies

Cited by 417 publications

References 170 publications

Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: bitartrate on Cu(110)

Chiral segregation driven by a dynamical response of the adsorption footprint to the local adsorption environment: bitartrate on Cu(110)

Chiral structures from achiral liquid crystals in cylindrical capillaries

Molecular chirality at surfaces

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