Chiral supramolecular assemblies from achiral and chiral molecules investigated by second harmonic generation at the air-water interface (original) (raw)
Related papers
Langmuir, 2004
We have investigated the two-dimensional ordering of chiral and achiral monodendrons at the liquidsolid interface. The chiral molecules self-assemble into extended arrays of dimers. As expected, the R enantiomer forms the mirror image type pattern of the chiral two-dimensional structure formed by the S enantiomer. A racemic mixture applied from solution onto the substrate undergoes spontaneous segregation: the enantiomers separate on the surface and appear in different domains. In contrast to the chiral molecules, the achiral analogue self-assembles into cyclic tetramers. Moreover, the pattern formed by the achiral molecule strongly depends on the solvent used. In the case of 1-phenyloctane, solvent molecules are coadsorbed in a 2:1 (dendron:solvent) ratio whereas in 1-octanol, no solvent molecules are coadsorbed. By the appropriate solvent choice, the distance between the potential "supramolecular containers" can be influenced.
Chirality in molecular films at the air-water interface
Organic Photonic Materials and Devices Xiii, 2011
Second Harmonic Generation (SHG) was used to study the nonlinear optical properties of a two-dimensional film formed by the achiral amphiphilic compound 5-(octadecyloxy)-2-(2-thiazolylazo) phenol (TARC18) at the air-water interface. The S-polarized SHG intensity was measured as a function of the incident fundamental wave polarization angle during the monolayer compression. The method was applied to follow the emergence of chirality during the film compression and at constant surface pressure. The formation of molecular aggregates revealing supramolecular chirality was then demonstrated. It was shown furthermore that the origin of chirality was dominated by the magnetic contributions.
Communication: Probing the absolute configuration of chiral molecules at aqueous interfaces
The Journal of Chemical Physics, 2015
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Journal of the American Chemical Society, 2001
Spontaneous formation of complementary hydrogen-bond pairs and their hierarchical self-assembly (reconstitution) into chiral supramolecular membranes are achieved in water by mixing amphiphilic pairs of glutamate-derived melamine 6 and ammonium-derivatized azobenzene cyanuric acid 4. Electron microscopy is used to observe formation of helical superstructures, which are distinct from the aggregate structures observed for each of the single components in water. In addition, a spectral blue-shift and induced circular dichroism (ICD) with exciton coupling are observed for the π-π* absorption of the azobenzene chromophores. These observations are consistent with the reconstitution of the hydrogen-bond-mediated supramolecular membrane 6-4. Spectral titration experiments indicate the stoichiometric integration of the complementary subunits with an association constant of 1.13 × 10 5 M-1. This value is considerably larger than those reported for the artificial hydrogen-bonding complexes in aqueous media. The remarkable reconstitution efficiency is ascribed to the hydrophobically driven self-organization of the amphiphilic, linear hydrogen-bond networks in water. Molecular structure of the complementary subunits plays an important role in the complexation process since it is restricted by the photoisomerized cis-azobenzene subunit. On the other hand, thermally regenerated trans-isomer 4 undergoes facile complexation with the counterpart 6. The present reconstitution of supramolecular membranes provides the first example of complementary hydrogen-bond-directed formation of soluble, mesoscopic supramolecular assemblies in water.
Functional Chirality: from Small Molecules to Supramolecular Assemblies
Symmetry, 2022
Many structures in nature look symmetric, but this is not completely accurate, because absolute symmetry is close to death. Chirality (handedness) is one form of living asymmetry. Chirality has been extensively investigated at different levels. Many rules were coined in attempts made for many decades to have control over the selection of handedness that seems to easily occur in nature. It is certain that if good control is realized on chirality, the roads will be ultimately open towards numerous developments in pharmaceutical, technological, and industrial applications. This tutorial review presents a report on chirality from single molecules to supramolecular assemblies. The realized functions are still in their infancy and have been scarcely converted into actual applications. This review provides an overview for starters in the chirality field of research on concepts, common methodologies, and outstanding accomplishments. It starts with an introductory section on the definitions ...
Supramolecular Chirality: Solvent Chirality Transfer in Molecular Chemistry and Polymer Chemistry
Symmetry, 2014
Controlled mirror symmetry breaking arising from chemical and physical origin is currently one of the hottest issues in the field of supramolecular chirality. The dynamic twisting abilities of solvent molecules are often ignored and unknown, although the targeted molecules and polymers in a fluid solution are surrounded by solvent molecules. We should pay more attention to the facts that mostly all of the chemical and physical properties of these molecules and polymers in the ground and photoexcited states are significantly influenced by the surrounding solvent molecules with much conformational freedom through non-covalent supramolecular interactions between these substances and solvent molecules. This review highlights a series of studies that include: (i) historical background, covering chiral NaClO 3 crystallization in the presence of D-sugars in the late 19th century; (ii) early solvent chirality effects for optically inactive chromophores/fluorophores in the 1960s-1980s; and (iii) the recent development of mirror symmetry breaking from the corresponding achiral or optically inactive molecules and polymers with the help of molecular chirality as the solvent use quantity.