Supramolecular Chirality Inversion Research Articles

Photoisomerization and thermal reconstruction induced supramolecular chirality inversion in nanofiber determined by minority isomer

Here, amphiphile GCH based on glutamide-cyanostilbene is designed and synthesized, it is found that it can assembly in acetonitrile, and shows circular dichroism signals. After Z-E isomerizaition by UV irradiation, the CD signal of the assembly can be inverted. Unexpectedly, after another heating and cooling process, the circular dichroism signals can be totally inverted even though the E-isomers are in minority. Finally, the molecular dynamics (MD) simulations deeply elucidate the supramolecuar chirality inversion mechanism. This work brings some new insights into the control of chirality inversion, which may provide a perspective for the smart chiroptical materials construction.

Achiral substituent- and stoichiometry-controlled inversion of supramolecular chirality and circularly polarized luminescence in ternary co-assemblies.

Handedness inversion of supramolecular chirality and circularly polarized luminescence (CPL) in assembled systems containing more than two components with higher complexity is of prominent importance to simulate biological multicomponent species and design advanced chiral materials, but it remains a considerable challenge. Herein, we have successfully developed ternary co-assembly systems based on aromatic amino acids, vinylnaphthalene derivatives and 1,2,4,5-tetracyanobenzene with effective chirality transfer. Notably, the handedness of supramolecular chirality and CPL can be readily inverted by changing the residues of amino acids, the substituents of achiral vinylnaphthalene derivatives, or by adjusting the stoichiometric ratio. The hydrogen bonds, charge transfer interactions, and steric hindrance are proved to be the crucial factors for the chirality inversion. This flexible control over chirality not only offers insights into developing multicomponent chiral materials with desirable handedness from simple molecular building blocks, but also is of practical value for use in chiroptics, chiral sensing, and photoelectric devices.

A Single-Enantiomer Emitter Enabled Superstructural Helix Inversion for Upconverting and Downshifting Luminescence with Bidirectional Circular Polarization.

The helical twisting tendency of liquid crystals (LCs) is generally governed by the inherent configuration of the chiral emitter. Here, we introduce the multistage inversion of supramolecular chirality as well as circularly polarized luminescence (CPL) by manipulating the ratio of single enantiomeric emitters (R-PCP) to LC monomers (5CB). Increasing the content of R-PCP from 1 wt % to 3 wt % inverted the helix of LCs from left-handed to right-handed, accompanying a CPL sign changed from positive to negative. The biaxiality of chiral emitters, as well as the steric effect of chiral-chiral and chiral-achiral interaction, were identified as the reasons for helical sense inversion. Due to the strong helical twisting power, 4 wt % R-PCP drove the photonic band gap (PBG) of chiral LCs to match up with their emission range, leading to an inversion of the CPL again with a high dissymmetry factor (≈1.2). Directly adjusting the PBG using chiral emitters is seldom achieved in cholesteric LCs. On this basis, an achiral sensitizer PtTPBP was assembled into the helical superstructure. The generation of triplet-triplet annihilation-induced upconverted CPL from R-PCP and the downshifting CPL from PtTPBP with opposite rotation was achieved in a single chiral LC system by tuning the position of the PBG.

Circularly Polarized Luminescence Switching Driven by Precisely Tuned Supramolecular Interactions: From Hydrogen Bonding to π-π Interaction.

It is highly challenging to achieve circularly polarized luminescence (CPL) switching by precisely tuning supramolecular interactions and unveiling the mechanism of supramolecular chirality inversion. Herein, we demonstrated CPL switching based on diethyl l-glutamate-9-cyanophenanthrene (LGCP) and diethyl l-glutamate-pyrene (LGP) via the precise regulation of supramolecular interactions. LGCP assembly driven by hydrogen bonding showed right CPL, while LGP assembly driven by π-π interaction led to left CPL. Remarkably, significant CPL switching was observed from the assemblies of LGCP/octafluoronaphthalene (OFN), attributed to the alteration of the dominating interaction from weak hydrogen bonding to rather strong π-π interaction, while the assemblies of LGP/OFN exhibited minimum CPL variation because the dominating π-π interaction within the assembly of LGP/OFN illustrated quite limited variations upon arene-perfluoroarene interaction. This work provides a feasible strategy toward the efficient modulation of the chiroptical properties of multiple component supramolecular systems, meanwhile offering possibilities for the mechanism exploration of the chirality inversion of supramolecular assemblies.

Kinetic and Thermodynamic Aggregation of Coordinated Supramolecular Polymers with Quadruple Modulated Inversion of Circular Dichroism

AbstractSupramolecular chirality is the inherent property and the corresponding performance of aggregated materials in the supramolecular polymer (SP) system. It is an interesting but challenging issue to regulate the handedness direction of supramolecular chirality and achieve the circular dichroism (CD) inversion of chiral SP‐based aggregates, especially for the ones assembled from metal‐organic supramolecular polymer (MOSP) with great potential in asymmetric catalysis, chiral recognition, and chiroptical devices. Herein, a set of nanoaggregates coassembled from para‐pyridine imine‐linked cholesterol conjugate (pPMPCC) and various metal salts, using the cooperative interactions of metal‐ion coordination, van der Waals interaction and solvent polarity, is rationally designed and prepared. Interestingly, quadruple modulated supramolecular chirality inversion (SMCI) of MOSP‐based nanoaggregates is modulated by various metal ions (such as Co2+, Cu2+, Zn2+, Mn2+, and Bi3+) and their content, as well as the external stimuli like solvent effects, temperature, and ultrasound. This work provides a facile pathway to tune the helical self‐aggregation of metal‐organic complex systems with quadruple‐modulated CD inversion, which would be of great potential in asymmetric catalysis, chiral recognition, and sensing with dynamic supramolecular chirality.

Metallophilic Interaction-Mediated Hierarchical Assembly and Temporal-Controlled Dynamic Chirality Inversion of Metal–Organic Supramolecular Polymers

The study of dynamic supramolecular chirality inversion (SMCI) not only helps to deepen the understanding of chiral transfer and amplification in both living organizations and artificially chemical self-assembly systems but also is useful for the development of smart chiral nanomaterials. However, it is still challenging to achieve the dynamic SMCI of the self-aggregation of metal-organic supramolecular polymers with great potential in asymmetric synthesis, chiroptical switches, and circular polarized luminescence. Here, we successfully developed a hierarchical coassembly system based on the mPAzPCC and various metal ions with effective chirality transfer and temporal-controlled SMCI. Due to the dynamic self-assembly and hierarchical chirality transfer of the Ag+/mPAzPCC complex driven by metallophilic interaction and coordination, morphological transition with nanoribbons, helical nanoribbons, and chiral nanotubules was successively obtained. Interestingly, the SMCI of chiral nanoaggregates was precisely regulated by solvents and metal ions in the Cu2+/mPAzPCC and Mn2+/mPAzPCC system. Besides, temporal-controlled dynamic SMCI switching from helix to bundled helix was clearly revealed in the aggregation of Cu2+/mPAzPCC, Mn2+/mPAzPCC, and Bi3+/mPAzPCC systems. This work provides a metallophilic interaction-mediated helical assembly pathway to dynamically modulate the chirality of metal-organic complex-based assemblies and deepen the understanding of the hierarchically dynamic self-assembly process, which would be of great potential in metal ion-mediated supramolecular asymmetric catalysis and bioinspired chiral sensing.

Self-assembled stereomutation with supramolecular chirality inversion.

Supramolecular chirality is involved not only in biological events such as gene communication, replication, and enzyme catalysis but also in artificial self-assembly systems and aggregated materials. The precise control of supramolecular chirality, and especially supramolecular chirality inversion (SMCI), would deepen the understanding of chiral transfer and regulation in both living systems and artificial self-assembly systems, providing efficient ways to construct advanced chiral materials with an optimum assembly pathway necessary for various functions. In this review, the fundamental principles of SMCI are comprehensively summarized, with a focus on the helical assemblies having opposite handedness or chiroptical properties of the compositions. Thereafter, various SMCI strategies that have been developed for chiral nanostructures and assembled materials are systematically reviewed, and the promising applications of SMCI, including chiroptical switches, chiral recognition, enantiomeric separation, asymmetric catalysis, chiral optoelectronic materials, chiral spin filters, and biomedical uses, are highlighted accordingly. Finally, the scientific challenges and future perspectives for assembling materials with SMCI are also discussed.

Multiple chirality inversion of pyridine Schiff-base cholesterol-based metal-organic supramolecular polymers.

Based on a metal coordination driven co-assembly strategy, a metal-organic supramolecular polymer system of pyridine Schiff-base cholesterol and metal ions with multiple supramolecular chirality inversion was successfully achieved by the stoichiometry and exchange of metal ions (such as Co2+, Ni2+, Cu2+, Zn2+, and Ag+), as well as the solvent polarity.

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Supramolecular chirality of multicomponent self-assembled systems and their applications

<p indent=0mm>Chirality is closely associated with life, such as amino acids at the molecular level, secondary structures of proteins (DNA, RNA), nanoscale helices and macroscopic conches. Due to the dynamic property of non-covalent bond, self-assembly of molecule shows environmental adaptability. The stacking form of molecule can be regulated via tunning non-covalent interaction. The asymmetric aggregation of molecular building blocks is called supramolecular chirality which is not only related to the structure of molecule and molecular chirality, but also influenced by non-covalent interaction. Regulation of the emergence, amplification, transfer and inversion of supramolecular chirality is an important field. The assemblies with supramolecular chirality are usually driven by various non-covalent interactions with unique chiral micro-environment. Design and fabrication of supramolecular assemblies with two or more kinds of components are much more complex than the single component systems due to the complexity of possible pathways. Compared with single-component systems which have already matured, both basic and application research of multi-component supramolecular chiral assemblies are still limited. However, the study of supramolecular chirality of multicomponent self-assembled systems not only benefit to simulate complex biological systems, but also contribute to the deep understanding of the origin of homochirality in nature to further apply in bionics, which is of great significance. Therefore, in this review article, we mainly discuss the construction of multicomponent self-assembled systems including solvent effect, hydrogen bond, structural analogues, organic/inorganic co-assembly. Solvent polarity has a great influence on self-assembled process of molecules especially for amphiphiles whose molecular stacking layer that exposes to solvents should be solvophilic. Besides the effect of polarity, solvent molecules also could act as an active component to participate self-assembled process generating significant influence on self-assembly behavior and even supramolecular chirality. Due to the directionality and relatively strong intensity compared with other non-covalent interactions, hydrogen bonding has been considered as the important interaction to construct supramolecular assemblies. Hydrogen bonding could be widely observed among amide/imide, ureido and carboxylic acid groups which has been introduced in this review in detail. And the influence of hydrogen bond to supramolecular chirality also has been fully discussed. Introducing structural analogues into building block with chiral center is another effective method to construct multicomponent supramolecular assemblies. Two different paths upon the aggregation of structural analogues including self-sorting and coassembly might occur which are controlled via equilibrium of kinetically or thermodynamically. The realization of coassembly between structural analogues requires strong interactions between components or similarly staking mode. Because of the excellent properties of inorganic material especially in luminescence, inorganic/organic coassembled materials which could be applied in chiroptical with tunable chiral and optical properties have emerged. Moreover, a serial of three component supramolecular assemblies with tunable chiral and optical properties based on the research of double components have been developed. Strong non-covalent interactions including hydrogen bond and π-π stacking interaction are benefit for forming multicomponent supramolecular chiral assemblies. Besides design and fabrication multicomponent supramolecular chiral assemblies, we also introduced their applications in chiral recognition, circularly polarized luminescence (CPL), chiral catalysis and chiral template. Chiral recognition not only displays the interaction between achiral molecules with various chiral molecules, but also between supramolecular assemblies with chiral molecules. We mainly discussed the recognition of supramolecular assemblies to enantiomers. CPL is a nonnegligible application field of multicomponent supramolecular chiral assemblies which has attracted increasing attention due to its wide potential applications in optical displays, encryption and storage of information, photoelectric devices, chiroptical materials, and so on. Catalysts for asymmetric reactions under mild conditions have been widely studied based on different supramolecular assemblies including helical nanorods, nanotubes and vesicles. We expect this review will serve as an introduction and reference for researchers who are interested in exploring this field.

Dynamic evolution of supramolecular chirality manipulated by H-bonded coassembly and photoisomerism

Dynamic evolution of supramolecular chirality inversion and the inversion of corresponding circularly polarized luminescence via the multiple-constituent coassemblies driven by hydrogen bonds was realized.

Photoregulated "Breathing" Vesicle with Inversed Supramolecular Chirality.

Though phospholipids possess chiral centers, their chiral aggregation within bilayer cell membranes has seldom been referred and recognized. Insight into the chirality at higher levels in artificial molecular bilayer assemblies such as vesicles or liposomes is important to better understand biomembrane functions. In this work, we illustrate the fabrication of chiral vesicles with photoresponsive supramolecular chirality and structural transformation property. Cholesterol was conjugated to azobenzene via different spacers, of which molecular chirality underwent transfer to supramolecular level upon aggregation in water. The resultant building block self-assembled into unilamellar vesicles that could respond to light irradiation by showing reversible extension/contraction behavior. Such "breathing" behavior was accompanied with supramolecular chirality inversion from M- to P-handedness, confirmed by the solid-state crystal structure and electronic circular dichroism spectra based on density functional theory. The vesicle membrane behaves as a matrix to accommodate guest molecules via aromatic interactions, which significantly elevated the UV light resistance with respect to the structural and supramolecular chirality transformation. This work offers an unprecedented rational control over supramolecular chirality using photoresponsiveness in vesicular membranes.

Self-Assembly Evolution of N-Terminal Aromatic Amino Acids with Transient Supramolecular Chirality.

Deep understanding and fine tailoring of spontaneous structural evolution of self-assembled arrays are pivotal in the rational design of advanced soft materials. However, an indistinct structure-property relationship and pathway complexity in self-assembly lead to a considerable challenge. Herein, we reveal the self-assembly pathway complexity in spontaneous aggregation of several N-terminated aromatic amino acids. By primarily tuning the incubation time, building blocks appended with alanine and serine selectively form 1:1 hydrated clathrates, enabling the microfiber to transition to crystals. The dynamic water intercalation process was studied by incubation time-dependent morphological changes, powder X-ray diffraction, and single-crystal structure analysis. A pronounced amino acid residue effect on the self-assembly evolution was reflected by supramolecular chirality inversion of the building block having the phenylalanine residue, accomplishing dynamic M- to P-helicity transition within a confined time scale.

Controlling Supramolecular Chirality in Multicomponent Self-Assembled Systems.

Chirality exists as a ubiquitous phenomenon in nature, from molecular level l-amino acids, d-sugar, secondary structures of proteins, DNA, RNA, and nanoscale helices to macroscopic conch and even galaxy. The aggregation of molecular building blocks with or without chiral centers might bring about asymmetric spatial stacking, which further results in the appearance of nonsymmetry in extended scales like helical nanofibers. This phenomenon, known as supramolecular chirality, is an important branch of supramolecular and self-assembly chemistry, which relates intimately with biomimetics, asymmetric catalysis, and designing chiroptic advanced materials. One of the important research focuses among supramolecular chirality is about rational manipulation of chirality amplification and handedness, presenting a profound influence on the performance of resulting soft materials such as circularly polarized luminescence and cell adhesion on hydrogels. The control over supramolecular chirality normally relies on two factors, i.e., thermodynamic and kinetic variables dependent on molecular structural parameters and environmental contributions, respectively. Supramolecular chirality in two or more component-based systems places an emphasis on thermodynamic control as it occurs from either integrated coassembly or separated self-sorting, which is more sophisticated than that of single component systems. Thus, the study on supramolecular chirality in multicomponent systems could mimic complicated biosystems, allowing for better understanding about the origin of natural chirality and extended applications as biomimetics. To date, the exploration of supramolecular chirality in multicomponent systems is restricted on both fundamental and application aspects when compared to more matured single component systems. Over the past few years, we have carried out systematic studies on several systems expressing supramolecular chirality from chiral amplification or symmetry breaking. We emphasized more the thermodynamic control by introducing a second component to form noncovalent bonding like hydrogen bonding or coordination interactions. In this Account, we would specifically discuss rational manipulation of the occurrence, transfer, and inversion of supramolecular chirality by taking several of the latest representative examples. In the multicomponent systems, in addition to the building blocks with chiral centers, the second or third components could be structural analogues and achiral small molecules such as bipyridines, melamine, metal ions, inorganic nanomaterials, and even solvents. These second or third components are able to incorporate during the aggregation to form coassembly via noncovalent bonds, influencing spatial arrangements of building blocks within various dimensions from vesicles and nanofibers to organic/inorganic hybrids. Other than chirality, morphology, stimulus responsiveness, and properties could also be well tailored by controlling interactions between different components.

Water-Binding-Mediated Gelation/Crystallization and Thermosensitive Superchirality.

Determination of molecular structural parameters of hydrophobic cholesterol-naphthalimide conjugates for water binding capabilities as well as their moisture-sensitive supramolecular self-assembly were revealed. Water binding was a key factor in leading trace water-induced crystallization against gelation in apolar solvent. Ordered water molecules entrapped in self-assembly arrays revealed by crystal structures behave as hydrogen-bonding linkers to facilitate three-dimensional growth into crystals rather than one-dimensional gel nanofibers. Water binding was also reflected on the supramolecular chirality inversion of vesicle self-assembly in aqueous media via heating-induced dehydration. Structural parameters that favor water binding were evaluated in detail, which could help rationally design organic building units for advancing soft materials, crystal engineering, and chiral recognition.

Water‐Binding‐Mediated Gelation/Crystallization and Thermosensitive Superchirality

AbstractDetermination of molecular structural parameters of hydrophobic cholesterol–naphthalimide conjugates for water binding capabilities as well as their moisture‐sensitive supramolecular self‐assembly were revealed. Water binding was a key factor in leading trace water‐induced crystallization against gelation in apolar solvent. Ordered water molecules entrapped in self‐assembly arrays revealed by crystal structures behave as hydrogen‐bonding linkers to facilitate three‐dimensional growth into crystals rather than one‐dimensional gel nanofibers. Water binding was also reflected on the supramolecular chirality inversion of vesicle self‐assembly in aqueous media via heating‐induced dehydration. Structural parameters that favor water binding were evaluated in detail, which could help rationally design organic building units for advancing soft materials, crystal engineering, and chiral recognition.

Controlling Supramolecular Chirality of Two-Component Hydrogels by J- and H-Aggregation of Building Blocks.

While manipulating the helicity of nanostructures is a challenging task, it attracts great research interest on account of its crucial role in better understanding the formation mechanisms of helical systems. For the supramolecular chirality in self-assembly systems, one challenge is how to understand the origin of supramolecular chirality and inherent helicity information on nanostructures regulated by functionality-oriented stacking modes (such as J- and H-aggregation) of building blocks. Herein, two-component hydrogels were prepared by phenylalanine-based enantiomers and achiral bis(pyridinyl) derivatives, where helical nanofibers with inverse handedness as well as controllable helical pitch and diameter were readily obtained through stoichiometric coassembly of these building blocks. The helix inversion was achieved by the transition between the J- and H-aggregation of bis(pyridinyl) derivatives, which was collectively confirmed by circular dichroism, scanning electron microscopy, Fourier transform infrared spectroscopy, and single X-ray crystallography. Interestingly, the helical coassemblies with opposite handedness could be obtained not only from the enantiomeric building blocks but also from the chiral monomers with the same configurational chirality by exchanging achiral additives. This work provides insight into the origin and helicity inversion of supramolecular chirality in molecular self-assembly systems and may shine light on the precise fabrication of chiral nanostructures for potential applications in smart display devices, optoelectronics, and biological systems.

Stoichiometry-Controlled Inversion of Supramolecular Chirality in Nanostructures Co-assembled with Bipyridines.

To control supramolecular chirality of the co-assembled nanostructures, one of the remaining issues is how stoichiometry of the different molecules involved in co-assembly influence chiral transformation. Through co-assembly of achiral 1,4-bis(pyrid-4-yl)benzene and chiral phenylalanine-glycine derivative hydrogelators, stoichiometry is found to be an effective tool for controlling supramolecular chirality inversion processes. This inversion is mainly mediated by a delicate balance between intermolecular hydrogen bonding interactions and π-π stacking of the two components, which may subtly change the stacking of the molecules, in turn, the self-assembled nanostructures. This study exemplifies a simplistic way to invert the handedness of chiral nanostructures and provide fundamental understanding of the inherent principles of supramolecular chirality.

Transfer and Dynamic Inversion of Coassembled Supramolecular Chirality through 2D-Sheet to Rolled-Up Tubular Structure.

Transfer and inversion of supramolecular chirality from chiral calix[4]arene analogs (3D and 3L) with an alanine moiety to an achiral bipyridine derivative (1) with glycine moieties in a coassembled hydrogel are demonstrated. Molecular chirality of 3D and 3L could transfer supramolecular chirality to an achiral bipyridine derivative 1. Moreover, addition of 0.6 equiv of 3D or 3L to 1 induced supramolecular chirality inversion of 1. More interestingly, the 2D-sheet structure of the coassembled hydrogels formed with 0.2 equiv of 3D or 3L changed to a rolled-up tubular structure in the presence of 0.6 equiv of 3D or 3L. The chirality inversion and morphology change are mainly mediated by intermolecular hydrogen-bonding interactions between the achiral and chiral molecules, which might be induced by reorientations of the assembled molecules, confirmed by density functional theory calculations.

Metal-induced supramolecular chirality inversion of small self-assembled molecules in solution.

A non-covalent self-assembled chiral alanyl aminopyridine ligand exhibits supramolecular chirality in solution, independent of the organic solvent used. The supramolecular chirality of the assemblies is completely inverted by complexation to zinc ions. To date, such a supramolecular metal-ligand system has not been reported in the literature.