Chiral Supramolecular Assemblies Research Articles

Molecular Propeller Tethering on a Dipeptide Induces a One-Step Conversion of Its Secondary Structure on Water Surface Promoted by Chiral Supramolecular Assembly.

Water provides a unique surface for the formation of directed self-assembly and transformation of secondary structures of peptides and proteins as witnessed in the biological systems. Herein a one-step transformation of an amyloid-derived dipeptide is reported from β-sheet to α-helix structures on the water surface, facilitated by chiral supramolecular assembly. The study utilizes various analytical techniques to elucidate the structural transformation and the supramolecular packing of the peptide assemblies. Organizations such as spherical aggregates and molecular nanowires containing β-sheet structure are converted into (2D) molecular sheets comprising a larger planar area yet with a molecular level thickness of α-helix structure. The conformational features of the β-sheet to α-helix structural transformation are dominated by the intermolecular H-bonding, π-π stacking, and C─H···π interactions. Strikingly, the dynamic changes in the dihedral (intramolecular) angle between the aromatic rings of the dipeptide at the water surface alter the molecular packing and shorten the intermolecular H-bonds with larger binding energies required for the secondary structural transformation. Thus, the novel one-step strategy reports herein offers a simple, efficient, and hitherto unprecedented way of chiral supramolecular assembly directed total secondary structural transformation of the dipeptide on water surface.

Three-Level Chirality Transfer and Amplification in Liquid Crystal Supramolecular Assembly for Achieving Full-Color and White Circularly Polarized Luminescence.

Chiral liquid crystal supramolecular assembly provides an ideal strategy for constructing excellent circularly polarized luminescence (CPL) materials. However, the chirality transfer in chiral liquid crystals normally occurs at two levels from the configurational chirality to the supramolecular phase chirality. The more precise and more levels of chirality transmission are fascinating but remain challenging. The present work reports the first success of three-level chirality transfer and amplification from configurationally point chirality of small molecules to conformationally helical chirality of helical polymers and finally to supramolecular phase chirality of cholesteric liquid crystals composed of chiral nonfluorescent polymers (P46) and nematic liquid crystals. Noticeably, the helical twisting power of P46 is five-fold larger than its monomer. Full-color and white CPL with maximum luminescence dissymmetry factor up to 1.54 and photoluminescence quantum yield up to 63.8% are realized utilizing helical supramolecular assembly combined with selective reflection mechanism. Also significantly, the electrically stimuli-responsive CPL switching device as well as anti-counterfeiting security, information encryption, and chiral logic gate applications are developed. This study deepens the understanding of chirality transfer and amplification across different hierarchical levels.

Circularly Polarized Lasing from Helical Superstructures of Chiral Organic Molecules.

Chiral supramolecular aggregates have the potential to explore circularly polarized lasing with large dissymmetry factors. However, the controllable assembly of chiral superstructures towards deterministic circularly polarized laser emission remains elusive. Here, we design a pair of chiral organic molecules capable of stacking into a pair of definite helical superstructures in microcrystals, which enables circularly polarized lasing with deterministic chirality and high dissymmetry factors. The microcrystals function as optical cavities and gain media simultaneously for laser oscillations, while the supramolecular helices endow the laser emission with strong and opposite chirality. As a result, the microcrystals of two enantiomers allow for circularly polarized laser emission with opposite chirality and high dissymmetry factors up to ~1.0. This work demonstrates the chiral supramolecular assemblies as an excellent platform for high-performance circularly polarized lasers.

Circularly Polarized Lasing from Helical Superstructures of Chiral Organic Molecules

AbstractChiral supramolecular aggregates have the potential to explore circularly polarized lasing with large dissymmetry factors. However, the controllable assembly of chiral superstructures towards deterministic circularly polarized laser emission remains elusive. Here, we design a pair of chiral organic molecules capable of stacking into a pair of definite helical superstructures in microcrystals, which enables circularly polarized lasing with deterministic chirality and high dissymmetry factors. The microcrystals function as optical cavities and gain media simultaneously for laser oscillations, while the supramolecular helices endow the laser emission with strong and opposite chirality. As a result, the microcrystals of two enantiomers allow for circularly polarized laser emission with opposite chirality and high dissymmetry factors up to ~1.0. This work demonstrates the chiral supramolecular assemblies as an excellent platform for high‐performance circularly polarized lasers.

Adsorption of Prochiral Solvent Molecules by Surface-Confined Chiral Supramolecular Assemblies: How Solvent Impacts on-Surface Chirality.

The understanding of supramolecular chirality in self-assembled molecular networks (SAMNs) on surfaces generates a lot of interest because of its relation to the production of chiral sensors, reactors, and catalysts. We herein report the adsorption of a prochiral solvent molecule in porous SAMNs formed by a chiral dehydrobenzo[12]annulene (cDBA) derivative. Through the prochirality recognition of a solvent molecule, the supramolecular chirality of the SAMN is switched: the cDBA exclusively forms a counter-clockwise pore through co-adsorption of the solvent molecule in prochiral 1,2,4-trichlorobenzene, while in 1-phenyloctane it produces the opposite chiral, clockwise pore. The prochirality recognition of the solvent molecule in the chiral SAMN pores is attributed to the adaptable conformational changes of the chiral chains of the cDBA molecule.

TPE-embedded butterfly bis-crown ether with controllable conformation and supramolecular chiroptical property

Understanding how subtle structural differences between macrocyclic conformational isomers impact their properties and separation has garnered increasing attention in the field of supramolecular synthetic chemistry. In this work, a series of tetraphenylene (TPE)-embedded butterfly bis-crown ether macrocycles (BCE[n], n = 4–7), comprising two crown ether side rings and a TPE core, are synthesized through intramolecular McMurry coupling. Unexpectedly, the presence of flexible oligoethylene chains with varying lengths are found to influence molecular conformation via multiple intramolecular interactions, resulting in the formation of two stabilized conformers with specific semi-rigid symmetric/asymmetric structures (sym-BCE[n] and asym-BCE[n], n = 5, 6). Moreover, it is noteworthy that neither symmetric nor asymmetric conformers are present in the more rigid BCE[4] or the more flexible BCE[7]. Interestingly, these conformers display distinct fluorescence properties and host-guest binding abilities, and only sym-BCE[5] can serve as a host for chiral polymer binding, resulting in the formation of chiral supramolecular assemblies through host-guest interaction induced chirality. Moreover, both circular dichroism and circularly polarized luminescence signals of the obtained assemblies can be switched off by the addition of sodium ion, suggesting potential applications in the field of dynamic chiral materials.

Intense Circularly Polarized Luminescence Induced by Chiral Supramolecular Assembly: The Importance of Intermolecular Electronic Coupling

Herein we report on circularly polarized luminescence (CPL) emission originating from supramolecular chirality of organic microcrystals with a |glum| value up to 0.11. The microcrystals were prepared from highly emissive difluoroboron β‐diketonate (BF2dbk) dyes R‐1 or S‐1 with chiral binaphthol (BINOL) skeletons. R‐1 and S‐1 exhibit undetectable CPL signals in solution but manifest intense CPL emission in their chiral microcrystals. The chiral superstructures induced by BINOL skeletons were confirmed by XRD analysis. Spectral analysis and theoretical calculations indicate that intermolecular electronic coupling, mediated by the asymmetric stacking in the chiral superstructures, effectively alters excited‐state electronic structures and facilitates electron transitions perpendicular to BF2bdk planes. The coupling increases cosθµ,m from 0.05 (monomer) to 0.86 (tetramer) and triggers intense optical activity of BF2bdk. The results demonstrate that optical activity of chromophores within assemblies can be regulated by both orientation and extent of intermolecular electronic couplings.

Intense Circularly Polarized Luminescence Induced by Chiral Supramolecular Assembly: The Importance of Intermolecular Electronic Coupling.

Herein we report on circularly polarized luminescence (CPL) emission originating from supramolecular chirality of organic microcrystals with a |glum| value up to 0.11. The microcrystals were prepared from highly emissive difluoroboron β-diketonate (BF2dbk) dyes R-1 or S-1 with chiral binaphthol (BINOL) skeletons. R-1 and S-1 exhibit undetectable CPL signals in solution but manifest intense CPL emission in their chiral microcrystals. The chiral superstructures induced by BINOL skeletons were confirmed by single-crystal XRD analysis. Spectral analysis and theoretical calculations indicate that intermolecular electronic coupling, mediated by the asymmetric stacking in the chiral superstructures, effectively alters excited-state electronic structures and facilitates electron transitions perpendicular to BF2bdk planes. The coupling increases cosθμ,m from 0.05 (monomer) to 0.86 (tetramer) and triggers intense optical activity of BF2bdk. The results demonstrate that optical activity of chromophores within assemblies can be regulated by both orientation and extent of intermolecular electronic couplings.

Supramolecular Chiral Aggregation of Porphyrin Induced by Photo-Generated Triphenylamines Radical Cations.

Here, it is shown that photoirradiation triggered chiral J-aggregates formation of an achiral anionic porphyrin, TPPS (tetrakis(4-sulfonatophenyl) porphyrin), in the presence of chiral triphenylamine (TPA) derivatives. A series of chiral triarylamines linked with aromatic rings is designed through urea or amide bonds. UV-irradiation of self-assembled urea-linked triphenylamine derivatives causes the formation of persistent radical cations in the chlorinated solvents, which subsequently induces the aggregation of TPPS. Transferring chirality of TPA derivatives to achiral TPPS J-aggregates leads to the chiral assemblies with remarkable chiroptical signals. The experimental results demonstrate that, TPA derivatives linked by the urea bond can effectively promote the aggregation of TPPS rather than those with the amide bond although the photo-generated radical cations are both produced. It is suggested that the urea-linked TPA derivatives are more favorable to stable radical cations and thus cause the formation of TPPS chiral J-aggregation. This work may open up an avenue for designing photo-modulated chiral supramolecular assemblies.

Regulating the Chiroptical Expression of Aggregated Solvophobic Core by Solvophilic Segments.

The investigation of chiral supramolecular stacking is of essential significance for the understanding of the origin of homochirality in nature. Unlike structurally well-defined amphiphilic liposomes, it remains unclear whether the solvophilic segments of the amphiphilic block copolymer play a decisive role in the construction of asymmetric superstructures. Herein, insights are presented into the stacking patterns and morphological regulation in azobenzene-containing block copolymer assemblies solely by modulating the solvophilic chain length. The solvophilic poly(methacrylic acid) (PMAA) segments of different molecular weights could cause multi-mode chirality inversions involving stacking transitions between intra-chain π-π stacking, inter-chain H- and J-aggregation. Furthermore, the length of the solvophilic PMAA also affects the morphology of the chiral supramolecular assemblies; rice grain-like micelles, worms, nanofibers, floccules, and lamellae can be prepared at different solvophilic-solvophobic balance. The comprehensive mechanism is collectively revealed by utilizing various measurement methods, such as including circular dichroism (CD), small-angle X-ray scattering (SAXS), and wide-angle X-ray diffraction (WAXD). This study highlights the critical importance of fully dissolved solvophilic segments for the chiroptical regulation of the aggregated core, providing new insights into the arrangement of chiral supramolecular structures in polymer systems.

Revealing Pathway Complexity and Helical Inversion in Supramolecular Assemblies Through Solvent-Induced Radical Disparities.

New insights are raised to interpret pathway complexity in the supramolecular assembly of chiral triarylamine tris-amide (TATA) monomer. In cosolvent systems, the monomer undergoes entirely different assembly processes depending on the chemical feature of the two solvents. Specifically, 1,2-dichloroethane (DCE) and methylcyclohexane (MCH) cosolvent trigger the cooperative growth of monomers with M helical arrangement, and hierarchical thin nanobelts are further formed. But in DCE and hexane (HE) combination, a different pathway occurs where monomers go through isodesmic growth to generate twisted nanofibers with P helical arrangement. Moreover, the two distinct assemblies exhibit opposite excited-state chirality. The driving force for both assemblies is the formation of intermolecular hydrogen bonds between amide moieties. However, the mechanistic investigation indicates that radical and neutral triarylamine species go through distinct assembly phases by changing solvent structures. The neutralization of radicals in MCH plays a critical role in pathway complexity, which significantly impacts the overall supramolecular assembly process, giving rise to inversed supramolecular helicity and distinct morphologies. This differentiation in pathways affected by radicals provides a new approach to manipulate chiral supramolecular assembly process by facile solvent-solute interactions.

Multiple hydrogen bonding driven supramolecular architectures and their biomedical applications.

Supramolecular chemistry combines the strength of molecular assembly via various molecular interactions. Hydrogen bonding facilitated self-assembly with the advantages of directionality, specificity, reversibility, and strength is a promising approach for constructing advanced supramolecules. There are still some challenges in hydrogen bonding based supramolecular polymers, such as complexity originating from tautomerism of the molecular building modules, the assembly process, and structure versatility of building blocks. In this review, examples are selected to give insights into multiple hydrogen bonding driven emerging supramolecular architectures. We focus on chiral supramolecular assemblies, multiple hydrogen bonding modules as stimuli responsive sources, interpenetrating polymer networks, multiple hydrogen bonding assisted organic frameworks, supramolecular adhesives, energy dissipators, and quantitative analysis of nano-adhesion. The applications in biomedical materials are focused with detailed examples including drug design evolution for myotonic dystrophy, molecular assembly for advanced drug delivery, an indicator displacement strategy for DNA detection, tissue engineering, and self-assembly complexes as gene delivery vectors for gene transfection. In addition, insights into the current challenges and future perspectives of this field to propel the development of multiple hydrogen bonding facilitated supramolecular materials are proposed.

Nanofibrous Chiral Supramolecular Assembly-Derived Self-Healing Hydrogels With Polyethylene Glycol

Unique polymer hydrogels with unusual cross-linking networks and self-healing properties have been recently reported. In this study, we fabricated hybrid hydrogels consisting of a chiral supramolecular one-dimensional assembly of glutamide-derived...

Chiral helix amplification and enhanced bioadhesion of two-component low molecular weight hydrogels regulated by OH to eradicate MRSA biofilms.

The supramolecular chemistry of small chiral molecules has attracted widespread attention owing to their similarity to natural assembly codes. Two-component low-molecular-weight (LMW) hydrogels are crucial as they form helical structures via chirality transfer, enabling diverse functions. Herein, we report a pair of two-component chiral LMW hydrogels based on the small molecular drugs baicalin (BA), scutellarin (SCU) and berberine (BBR). The two hydrogels exhibited different helicities and abilities to adhere to methicillin-resistant staphylococcus aureus (MRSA) biofilms. The BA or SCU can each laterally interact with BBR in a tail-to-tail configuration, forming a stable hydrophobic structure, while hydrophilic glucuronide groups are exposed to a water solution to form a hydrogel. However, the tiny variant steric hindrance of the terminal OH moiety of SCU affects π-π stacking in the layered assembly, resulting in SCU-BBR having much stronger chirality deviation and supramolecular chirality amplification than BA-BBR. Thereafter, the OH group in SCU-BBR forms more intermolecular hydrogen bonds with MRSA biofilms, enhancing stronger adhesion and better scavenging effects than BA-BBR. This work provides a unique chiral supramolecular assembly pattern, expands the antibacterial application prospect of a two-component LMW hydrogel accompanying chirality amplification, and provides a new perspective and strategy for biofilm removal.

Tailoring Dynamic Chiral Supramolecular Assembly with Phototriggered Radical Anions of C3-Symmetric Triphenylene Triimides

Tailoring Dynamic Chiral Supramolecular Assembly with Phototriggered Radical Anions of C₃-Symmetric Triphenylene Triimides

P/M Macromolecular Switch Based on Conformational Control Exerted by an Achiral Side Chain within an Axially Chiral Locked Pendant.

Molecular switches, supramolecular chemistry, and polymers can be combined to create stimuli-responsive multichiral materials. Therefore, by acting on the extended/bent conformational composition of an achiral arm, it is possible to create a macromolecular gear, where different supramolecular interactions can be activated/deactivated to control the helical sense of a polymer containing up to five different chiral axial motifs. For this, a chiral allene with a flexible achiral arm was introduced as a pendant in poly(phenylacetylene). Through flexible arm control between extended and bent conformations, it is possible to selectively induce either a P or M helical sense in the polymer, while the relative spatial distribution of the substituents in the allene remains unaltered in two perpendicular planes (configurationally locked). These results show that complex dynamic multichiral materials can be obtained by the polymerization of appropriate monomers that combine chirality, switching properties, and the ability to generate chiral supramolecular assemblies.

Cover Picture

Chiral supramolecular assembly of π‐conjugated luminophores holds significant potential for fabricating circularly polarized luminescent materials. The cover picture illustrates how precise adjustments to the molecular structure influence the circularly polarized luminescent properties of supramolecular assemblies, resulting in bathochromic‐shifted fluorescence and enhanced dissymmetry factors with increasing π‐conjugation length. More details are discussed in the article by Wang et al. on page 135—141. image

Enhancing the Circularly Polarized Luminescence of Self‐assembled Cyanostilbenes through Extended π‐Conjugation

Comprehensive SummaryChiral supramolecular assembly of π‐conjugated luminophores provides a promising avenue for enhancing circularly polarized luminescence. In this study, we shed light on the impact of π‐conjugation length on circularly polarized luminescent performance of the resulting supramolecular assemblies, by designing a tetra‐cyanostilbene monomeric compound alongside two dicyanostilbene control compounds. These cyanostilbene‐based compounds possess the ability to form chiral supramolecular polymers in toluene, driven by a synergistic combination of intermolecular hydrogen bonding and π–π stacking interactions. The extended π‐aromatic skeleton brings bathochromic‐shifted fluorescence and enhanced intermolecular stacking capability for the tetra‐cyanostilbene compound. Consequently, chiral supramolecular assemblies formed by the tetra‐cyanostilbene compound demonstrate a remarkable two‐fold increase in glum values relative to the assemblies formed by the dicyanostilbene compounds. Overall, this study provides valuable insights into the relationship between π‐conjugation length and the circularly polarized luminescent performance of π‐conjugated supramolecular assemblies.

Solvation‐Mediated Self‐Assembly from Crystals to Helices of Protic Acyclic Carbene AuI‐Enantiomers with Chirality Amplification

AbstractConstructing chiral supramolecular assembly and exploring the underlying mechanism are of great significance in promoting the development of circularly polarized luminescence (CPL)‐active materials. Herein, we report a solvation‐mediated self‐assembly from single‐crystals to helical nanofibers based on the first protic acyclic (methoxy)(amino)carbenes (pAMACs) AuI‐enantiomers driven by a synergetic aurophilic interactions and H‐bonds. Their aggregation‐dependent thermally activated delayed fluorescence properties with high quantum yields (ΦFL) up to 95 % were proved to be attributed to packing modes of Au⋅⋅⋅Au dimers with π‐stacking or one‐dimensional extended Au⋅⋅⋅Au chains. Via drop‐casting method, supramolecular P‐ or M‐helices were prepared. Detailed studies on the helices demonstrate that formations of extended helical Au⋅⋅⋅Au molecular chains amplify supramolecular chirality, leading to strong CPL with high dissymmetry factor (|glum|=0.030, ΦFL=67 %) and high CPL brightness (BCPL) of 4.87×10−3. Our findings bring new insights into the fabrication of helical structures to improve CPL performance by modifying aurophilic interactions.

Solvation-Mediated Self-Assembly from Crystals to Helices of Protic Acyclic Carbene AuI -Enantiomers with Chirality Amplification.

Constructing chiral supramolecular assembly and exploring the underlying mechanism are of great significance in promoting the development of circularly polarized luminescence (CPL)-active materials. Herein, we report a solvation-mediated self-assembly from single-crystals to helical nanofibers based on the first protic acyclic (methoxy)(amino)carbenes (pAMACs) AuI -enantiomers driven by a synergetic aurophilic interactions and H-bonds. Their aggregation-dependent thermally activated delayed fluorescence properties with high quantum yields (ΦFL ) up to 95 % were proved to be attributed to packing modes of Au⋅⋅⋅Au dimers with π-stacking or one-dimensional extended Au⋅⋅⋅Au chains. Via drop-casting method, supramolecular P- or M-helices were prepared. Detailed studies on the helices demonstrate that formations of extended helical Au⋅⋅⋅Au molecular chains amplify supramolecular chirality, leading to strong CPL with high dissymmetry factor (|glum |=0.030, ΦFL =67 %) and high CPL brightness (BCPL ) of 4.87×10-3 . Our findings bring new insights into the fabrication of helical structures to improve CPL performance by modifying aurophilic interactions.