Amplification of Chirality in Dynamic Supramolecular Aggregates

Palmans, Anja R. A.; Meijer, E. W.

doi:10.1002/anie.200701285

Cited by 784 publications

(548 citation statements)

References 150 publications

(136 reference statements)

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“…Optical spectroscopy has in the past proven to be a rich experimental source for elucidating the order in and structure of self-assembled systems (20,41,(51)(52)(53). Circular dichroism (CD) spectroscopic data, in particular, show bisignate cotton effects for all three compounds in the same citrate buffer (100 mM, pH 6), which strongly suggest the presence of ordered aggregates (Fig.…”

Section: Resultsmentioning

confidence: 98%

Controlling the growth and shape of chiral supramolecular polymers in water

Besenius

Portale²,

Bomans

et al. 2010

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

206

187

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A challenging target in the noncovalent synthesis of nanostructured functional materials is the formation of uniform features that exhibit well-defined properties, e.g., precise control over the aggregate shape, size, and stability. In particular, for aqueousbased one-dimensional supramolecular polymers, this is a daunting task. Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing out attractive noncovalent forces within the hydrophobic core of the polymerizing building blocks with electrostatic repulsive interactions on the hydrophilic rim we managed to switch from elongated, rod-like assemblies to small and discrete objects. Intriguingly this rod-tosphere transition is expressed in a loss of cooperativity in the temperature-dependent self-assembly mechanism. The aggregates were characterized using circular dichroism, UV and 1H-NMR spectroscopy, small angle X-ray scattering, and cryotransmission electron microscopy. In analogy to many systems found in biology, mechanistic details of the self-assembly pathways emphasize the importance of cooperativity as a key feature that dictates the physical properties of the produced supramolecular polymers.aqueous self-assembly | controlled architecture | supramolecular polymerization | dynamic materials M olecular self-assembly has emerged as a fascinating area in its own right (1, 2). A toolbox initially developed by supramolecular chemists quickly expanded into an interdisciplinary field aiming at the manipulation of matter at the molecular scale (3, 4). Up until recently self-assembly in dilute aqueous environments has predominantly dealt with linear amphiphiles that form closed structures (5-9), such as spherical micelles, cylindrical or rod-like micelles, and vesicles using, for example, phospholipids (10, 11), synthetic block copolymers (12, 13), or dendrimers (14). Morphological control in objects of defined size or shape, and transitions between different morphologies are increasingly well understood (15)(16)(17)(18). Surprisingly, however, the generality of these concepts has not been translocated into another area of increasing interest, namely, the self-assembly of one-dimensional arrays. In that context the development of discotic monomers has proven to be a valuable route to allow for the synthesis of rod-like supramolecular polymers (19), whose potential applications in functional soft matter include electronics, biomedical engineering, and sensors (20)(21)(22)(23)(24)(25)(26). Considering the enormous interest in such systems, it is surprising that efforts to control the size and shape of nano-and micrometer size one-dimensional objects are rare (27-29); successful strategies rely on the use of templates (30, 31), end cappers (32), or selective solvent techniques (33).In order to control the growth of aqueous one-dimensional supramolecular polymers, we propose to utilize electrostatic repulsive contributions in analogy to surfactant...

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Section: Resultsmentioning

confidence: 98%

Controlling the growth and shape of chiral supramolecular polymers in water

Besenius

Portale²,

Bomans

et al. 2010

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

206

187

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“…29−33 In addition, biosystems have frequently switched their structures hierarchically to effectuate different functions. Although significant effort has been devoted to the tuning of the helical structures through external stimuli such as light irradiation, 34−36 aging, 37−39 dilution, 40 or chiral triggering, 26,[41][42][43][44][45]49 it still remains a challenge to hierarchically tune the helical structures through molecular self-assembly.…”

Section: ■ Introductionmentioning

confidence: 99%

Hierarchical Self-Assembly of Achiral Amino Acid Derivatives into Dendritic Chiral Nanotwists

et al. 2012

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ABSTRACT:The organogel formation and self-assembly of a glycine-based achiral molecule were investigated. It has been found that the compound could gel organic solvents either at a lower temperature with lower concentration or at room temperature with higher concentration, which showed different self-assembled nanostructures. At a low temperature of −15°C, the compound self-assembled into fibrous structures, whereas it formed distinctive flat microbelts at room temperature. When the organogel with nanofibers formed at −15°C was brought into an ambient condition, chiral twist nanostructures were immediately evolved, which subsequently transferred to a giant microbelt through a hierarchical dendritic twist with the time. Although the compound is achiral, it formed chiral twist with both left-and right-handed twist structures simultaneously. When a trace analogical chiral trigger, L-alanine or D-alanine derivative, was added, a complete homochiral dendritic twist was obtained. Interestingly, a reverse process, i.e. the transformation of the microbelts into twists, could occur upon dilution of the organogel with microbelt structure. During the dilution, both left-and right-handed chiral twists could be formed again. Interestingly, the same branch from the microbelt formed the twist with the same handedness. A combination of the density functional theory (DFT), molecular mechanics (MM), and molecular dynamics (MD) simulations demonstrates that the temperature-induced twisting of the bilayer is responsible for the morphological transformation and evolution of the dendrite twist. This research sheds new light on the hierarchical transformation of the chiral structures from achiral molecules via controlled self-assembly.

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“…This leads to the non-linear response in the CD intensity changes, e.g., helicity changes, upon the binding with a carboxylate ion [61]. This is related to the chirality amplification found in some dynamic polymers and supramolecular assemblies, which is one of the recent hot topics in chemistry of responsive molecules [62][63][64]. …”

Section: Helicity Control Using Hydroxy Acidsmentioning

confidence: 99%

Dynamic Helicity Control of Oligo(salamo)-Based Metal Helicates

Akine

2018

Inorganics

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Much attention has recently focused on helical structures that can change their helicity in response to external stimuli. The requirements for the invertible helical structures are a dynamic feature and well-defined structures. In this context, helical metal complexes with a labile coordination sphere have a great advantage. There are several types of dynamic helicity controls, including the responsive helicity inversion. In this review article, dynamic helical structures based on oligo(salamo) metal complexes are described as one of the possible designs. The introduction of chiral carboxylate ions into Zn 3 La tetranuclear structures as an additive is effective to control the P/M ratio of the helix. The dynamic helicity inversion can be achieved by chemical modification, such as protonation/deprotonation or desilylation with fluoride ion. When (S)-2-hydroxypropyl groups are introduced into the oligo(salamo) ligand, the helicity of the resultant complexes is sensitively influenced by the metal ions. The replacement of the metal ions based on the affinity trend resulted in a sequential multistep helicity inversion. Chiral salen derivatives are also effective to bias the helicity; by incorporating the gauche/anti transformation of a 1,2-disubstituted ethylene unit, a fully predictable helicity inversion system was achieved, in which the helicity can be controlled by the molecular lengths of the diammonium guests.

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Amplification of Chirality in Dynamic Supramolecular Aggregates

Cited by 784 publications

References 150 publications

Controlling the growth and shape of chiral supramolecular polymers in water

Controlling the growth and shape of chiral supramolecular polymers in water

Hierarchical Self-Assembly of Achiral Amino Acid Derivatives into Dendritic Chiral Nanotwists

Dynamic Helicity Control of Oligo(salamo)-Based Metal Helicates

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