Self-Assembled Single-Walled Metal-Helical Nanotube (M-HN): Creation of Efficient Supramolecular Catalysts for Asymmetric Reaction

Enantio- and Diastereoselective Synthesis and Spiral-Stair-Like Single Helix Assembly of Figure-Eight Cyclophenylenes

Helix assemblies of chiral molecules can transfer microscopic unimolecular chirality to macroscopic supramolecular chirality, enhancing various chiral properties. In addition to the commonly observed spiral-column-like helix assembly, a small number of spiral-stair-like helix assemblies have also been reported in aromatic nanocarbons with multiple chirality-related irregularities. However, they require separation of diastereomers and/or enantiomers or do not have stable chirality. Here, we report the enantio- and diastereoselective synthesis of figure-eight [10]cyclophenylenes with stable helical chirality by the rhodium-catalyzed four consecutive intramolecular [2 + 2 + 2] cycloadditions of dodecaynes with two flexible biphenyl units. The chiral figure-eight [10]cyclophenylene with ethyl and methyl side chains exhibits the spiral-stair-like single helix assembly in the crystal due to CH-π and CH-O interactions and good CPL properties in solution. Experimental verification of the enantio- and diastereodetermining steps of four consecutive [2 + 2 + 2] cycloadditions is also reported.

Novel Cationic Bolaamphiphiles for Protein and DNA Binding, Gene Delivery, and Antimicrobial Applications

In this study, we have designed and developed a cationic bolaform C12-(2,3-dihydroxy-N, N-dimethyl-N-(2-ureidoethyl)propan-1-aminium chloride)2 (C12(DDUPAC)2) that is derived from biocompatible molecules. The bolaform C12(DDUPAC)2 has hydroxyl (OH) functionality at both the cationic head groups. The impact of head group structure on the self-assembly and effectiveness of gene transfection and antimicrobial activity was investigated and compared with that of the hydrochloride salt C12-(N, N-dimethyl-N-(2-ureidoethan-1-aminium chloride)2 (C12(DUAC)2) of its precursor molecule. The formation of spherical as well as rod-like self-assembled structures was found to occur above a relatively low critical aggregation concentration (CAC) by the bolaforms. The results of calorimetric measurements demonstrated thermodynamically favorable aggregation in water. Interaction studies of the cationic bolaforms with the calf thymus DNA revealed stronger binding of C12(DDUPAC)2 in comparison to C12(DUAC)2, which explained higher in vitro gene transfection efficiency of C12(DDUPAC)2 than C12(DUAC)2. Both bolaforms interact weakly with the bovine serum albumin protein. MTT-based in vitro cytotoxicity assay was performed and both bolaforms were found to have marginal cytotoxicity. Further, both bolaforms exhibit advantageous antibacterial activity against E. coli and potent antifungal activity against Fusarium oxysporum at high dosages.

Smart β-cyclodextrin-dominated helical supramolecular dendritic assemblies improve the foliar affinity and biofilm disruption for treating alarming bacterial diseases

Recent outbreaks of alarming bacterial diseases have significantly impacted global agricultural productivity. Conventional bactericides exhibit certain limitations in efficiently impeding biofilm formation and annihilating biofilm-dispersed pathogens, and often expose to high off-target movement during foliar spraying. Here, we produce an innovative helical dendrimer-like supramolecular material (PhA28@β-CD) assembled by a bioactive small-molecule 2-chlorophenylisopropanolamine (PhA28) and β-cyclodextrin (β-CD) through host-guest recognition principle. In this system, the advisable optimization by a macrocyclic oligosaccharide-β-CD significantly enhances the water-solubility, biocompatibility, and bioavailability of PhA28. At a low-dose of 6.8 μg/mL, PhA28@β-CD discloses an outstanding biofilm disruption rate of 82.4 %, notably exceeding that of PhA28 (60.6 %), which thereby reduces the biofilm-associated virulence. Meanwhile, the self-assembled PhA28@β-CD possesses superior wetting and dispersing properties on hydrophobic leaves, leading to effective foliar deposition and prolong retention of active components. In vivo studies reveal that PhA28@β-CD exhibits superior curative (66.0 %) and protective (72.6 %) activities against citrus canker at 200 μg/mL, markedly surpassing those of the existing bactericide thiodiazole‑copper (46.8 % and 52.2 %) and single PhA28. This material also has broad-spectrum control efficiency (53.0 % ~ 59.5 %) against rice bacterial blight. This research lays the groundwork for developing carbohydrate-optimized multifunctional dendrimer-like assemblies aimed at disrupting biofilms and improving sustained bioavailability to combat bacterial diseases.

Hollow Superhelices Based on Chiral Europium Coordination Polymers

The construction of helical nanotubes based on chiral coordination polymers (CPs) is an intriguing but challenging task, which is important for the development of functional materials that combine macroscopic chirality with tube-related properties. Here, we selected a chiral europium phosphonate system, e. g., Eu(NO3)3/R-,S-pempH2, and carried out a systematic work. By controlling the hydrothermal reaction conditions such as the pH value of the reaction mixture, the molar ratio and concentration of the reactants, we obtained block-like crystals of R/S-1 b, rod-like crystals of R/S-3 r, hollow superhelices of R/S-2 hh, and solid superhelices of R/S-4 sh. In the latter two cases, the chirality has been successfully transferred and amplificated from the molecular level to the macroscopic level. Interestingly, compounds R/S-2 hh and R/S-4 sh have the same chemical composition of Eu(R/S-pempH)3⋅2H2O and show identical PXRD patterns, thus can be considered as the same material except for different morphologies. We further investigated their circularly polarized luminescence (CPL) properties and found that the hollow superhelix of R/S-2 hh had a larger dissymmetry factor than the solid superhelix of R/S-4 sh. This study not only provides the first example of hollow superhelices of chiral CPs, but also offers the possibility of modulating the chiroptical properties of CPs through morphological control.

Self-Assembled Bolaamphiphile-Based Organic Nanotubes as Efficient Cu(II) Ion Adsorbents

Self-assembled organic nanotubes (ONTs) have been actively examined for various applications such as chemical separations and catalysis owing to their well-defined tubular nanostructures with distinct chemical environments at the wall and internal/external surfaces. Adsorption of heavy metal ions onto ONTs plays an essential role in many of these applications but has rarely been assessed quantitatively. Herein, we investigated interactions between Cu2+ and single-/quadruple-wall bolaamphiphile-based ONTs having inner carboxyl groups with different inner diameters, COOH-ONT10nm and COOH-ONT20nm. We first examined the effects of Cu2+ on their nanotubular structures using SAXS, STEM, and AFM. COOH-ONT10nm was stable in aqueous Cu2+ solution in contrast to COOH-ONT20nm owing to the presence of polyglycine-II-type hydrogen bonding networks within its wall. Subsequently, we studied the Cu2+ adsorption behavior of COOH-ONT10nm by monitoring the concentration of unbound Cu2+ using linear sweep anodic stripping voltammetry. The Cu2+ adsorption was quick, attributable to efficient Cu2+ partitioning through the open ends of the ONT, followed by fast Cu2+ diffusion in the uniform, relatively large nanochannel. More importantly, the Cu2+ adsorption capacity and affinity of COOH-ONT10nm were measured under different pH conditions using the Langmuir adsorption model. The adsorption capacity was similar at the pH range examined, showing the participation of approximately 25% of the inner carboxyl groups in the adsorption. The adsorption affinity increased with pH, indicating the essential role of the deprotonated carboxyl groups in Cu2+ adsorption. Most interestingly, the Langmuir adsorption constant was significantly higher than those of previously reported synthetic adsorbents and planar monolayer based on carboxyl binding sites. The high Cu2+ affinity of the ONT was attributable to the highly dense binding sites on the well-defined nanoscale concave structure of the inner channel. These results provide a valuable guideline for designing self-assembled nanomaterials for efficient chemical separations, detection, and catalysis.

Metal Ion-Mediated Supramolecular Nanotube Catalyst for Enantioselective Reactions

Rational control over the morphologies of supramolecular assemblies for asymmetric catalysis with enhanced enantioselectivity represents a pivotal challenge in the realm of synthetic chemistry and material technology. Herein, Cu(II) ion-mediated supramolecular nanostructures assembled from chiral amino acid-based amphiphiles (l/d-AlaC16) are fabricated as chiral catalysts for Diels-Alder cycloaddition between aza-chalcone and cyclopentadiene. In particular, compared with the supramolecular nanosheet formed by l/d-AlaC16 without Cu(II) ions, we found that the l/d-alanine chiral amphiphile can form supramolecular nanotubes with a multilayer structure and with the thickness of the tubular wall about 15 nm through the transition from a nanoribbon to tubular structure in the presence of Cu(II) ions. Consequently, the catalytic enantioselectivity of Diels-Alder was improved from 6% (nanosheet) to 49% (nanotube), attributed to the curved surface of the nanotube structure, which provides a preferential chiral environment and high density of the catalytic center to favor the chirality transfer. Our study presented in this work offers valuable insights for designing chiral supramolecular catalysts with a higher enantioselectivity driven by a metal ions-mediated nanostructure.

Pathway-directed recyclable chirality inversion of coordinated supramolecular polymers

It remains challenging to elucidate the fundamental mechanisms behind the dynamic chirality inversion of supramolecular assemblies with pathway complexity. Herein, metal coordination driven assembly systems based on pyridyl-conjugated cholesterol (PVPCC) and metal ions (Ag+ or Al3+) are established to demonstrate pathway-directed, recyclable chirality inversion and assembly polymorphism. In the Ag(I)/PVPCC system, a competitive pathway leads Ag-Complex to form either kinetically controlled supramolecular polymer (Ag-SP I) or thermodynamically favored Ag-SP II, accompanied by reversible chiroptical inversion. Conversely, the Al(III)/PVPCC system displays a solvent-assisted consecutive pathway: the Al-Complex initially forms ethanol-containing Al-SP II, and subsequently converts into ethanol-free Al-SP I with opposite chiroptical performance upon thermal treatment. Moreover, stable chirality inversion in the solid state enables potential dynamic circularly polarized luminescence encryption when Ag(I)/PVPCC is co-assembled with thioflavin T. These findings provide the guidance for the dynamic modulation of chirality functionality in supramolecular materials for applications in information processing, data encryption, and chiral spintronics.

Remarkable Stability of Glutathione-Based Supramolecular Gel in the Presence of Oxidative Stress from Hydrogen Peroxide

Low molecular weight 7-methoxy-3-(p-nitrophenyl)iminocoumarin (MNI) with donor and acceptor groups has been synthesized. The molecule shows typical π-stacking geometry in the crystal structure. In this study, MNI, an achiral small organic molecule, forms a nanostructured supramolecular gel along with a short peptide sequence glutathione (GSH). The self-assembly of the achiral organic coumarin component and chiral biomolecule produces a chiral gel with helical fiber structures. Interestingly, the helicities of chiral gels are controlled by the solvent ratio, where MNI in DMSO and GSH in water has been used. Variation of the solvent ratio from 6:4 to 1:9 for DMSO:H2O results in six gels (4, 5, 6, 7, 8 and 9), where the gel numbers signify the water content ratio. FE-SEM analysis shows gel fibers with right-handed helical structures, which have been further confirmed by circular dichroism (CD) with notable helicity in 4 to 6. This is the first report of controlled chiral helical nanostructured supramolecular gel formation by a solvent mixture with an organic small molecule and biomolecule. Interestingly, storage modulus (G') initially decreases from 4 to 6 and further increases up to 9. An opposite strain (%) trend was observed among these six gels. These unusual solvent-dependent gel properties have been further applied to monitor the stability of the gels in the presence of hydrogen peroxide (H2O2), which converts GSH to oxidized glutathione (GSSG) in general. The oxidative stress from H2O2 disrupts 4 to 6 gels, and precipitation occurs. It is noteworthy to mention that GSSG alone cannot form a gel with the MNI molecule and forms a precipitate. Remarkably, on the other hand, 7 to 9 remain as strong gels even after H2O2 treatment. Among all six gels, 9 shows extraordinary stability of gels even after H2O2 treatment.

Unravelling denaturation, temperature and cosolvent-driven chiroptical switching in peptide self-assembly with switchable piezoelectric responses

Herein, we explore the intricate pathway complexity, focusing on the dynamic interplay between kinetic and thermodynamic states, during the supramolecular self-assembly of peptides. We uncover a multiresponsive chiroptical switching phenomenon influenced by temperature, denaturation and content of cosolvent in peptide self-assembly through pathway complexity (kinetic vs. thermodynamic state). Particularly noteworthy is the observation of chiroptical switching during the denaturation process, marking an unprecedented phenomenon in the literature. Furthermore, the variation in cosolvent contents produces notable chiroptical switching effects, emphasizing their infrequent incidence. Such chiroptical switching yields switchable piezoresponsive peptide-based nanomaterials, demonstrating the potential for dynamic control over material properties. In essence, our work pioneers the ability to control piezoresponsive behavior by transforming nanostructures from kinetic to thermodynamic states through pathway complexity. This approach provides new insights and opportunities for tailoring material properties in self-assembled systems.

Chiral Supramolecular Self-Assembly Catalysts with Enhanced Metal Ion Interaction for Higher Enantioselectivity

Understanding the interaction between metal ions as catalytic centers and supramolecular scaffolds as chiral substrates plays an important role in developing chiral supramolecular catalysts with high enantioselectivity. Herein, we found that compared with l-norleucine chiral amphiphile (l-NorC16), l-methionine chiral amphiphile (l-MetC16) with the only heteroatom of S site difference in the hydrophilic group can form a similar supramolecular chiral nanoribbon (NR) with the bilayer structure through the self-assembly approach; yet, the interaction between the Cu(II) ion catalytic centers and supramolecular scaffolds is reinforced, favoring the chirality transfer and therefore enhancing their catalytic enantioselectivity of Diels-Alder reaction from 23% [l-NorC16-NR-Cu(II)] to 78% [l-MetC16-NR-Cu(II)]. Our work demonstrates a new strategy from the perspective of strengthening the metal ion-supramolecular scaffold interaction for the preparation of chiral supramolecular catalysts with good catalytic enantioselectivity.

PyBox-La(OTf)3-Catalyzed Enantioselective Diels-Alder Cycloadditions of 2-Alkenoylpyridines with Cyclopentadiene

The PyBox-La(OTf)3-catalyzed enantioselective Diels-Alder cycloaddition of 2-alk-2-enoylpyridines with cyclopentadiene is realized, producing enantiopure disubstituted norbornenes, which possess four contiguous stereocenters and are biologically relevant structures in up to 92:8 dr and 99:1 er.

Biomimetic Chiral Nanomaterials with Selective Catalysis Activity

Chiral nanomaterials with unique chiral configurations and biocompatible ligands have been booming over the past decade for their interesting chiroptical effect, unique catalytical activity, and related bioapplications. The catalytic activity and selectivity of chiral nanomaterials have emerged as important topics, that can be potentially controlled and optimized by the rational biochemical design of nanomaterials. In this review, chiral nanomaterials synthesis, composition, and catalytic performances of different biohybrid chiral nanomaterials are discussed. The construction of chiral nanomaterials with multiscale chiral geometries along with the underlying principles for enhancing chiroptical responses are highlighted. Various biochemical approaches to regulate the selectivity and catalytic activity of chiral nanomaterials for biocatalysis are also summarized. Furthermore, attention is paid to specific chiral ligands, materials compositions, structure characteristics, and so on for introducing selective catalytic activities of representative chiral nanomaterials, with emphasis on substrates including small molecules, biological macromolecule, and in-site catalysis in living systems. Promising progress has also been emphasized in chiral nanomaterials featuring structural versatility and improved chiral responses that gave rise to unprecedented chances to utilize light for biocatalytic applications. In summary, the challenges, future trends, and prospects associated with chiral nanomaterials for catalysis are comprehensively proposed.

Self-Assembled Metal-Coordination Nanohelices as Efficient and Robust Chiral Supramolecular Catalysts for Enantioselective Reactions

The development of chiral nanostructures-based supramolecular catalysts with satisfied enantioselectivity remains a significantly more challenging task. Herein, the synthesis and self-assembly of various amino acid amphiphiles as chiral supramolecular catalysts after metal ion coordination is reported and systematically investigate their enantioselectivity in asymmetric Diels-Alder reactions. In particular, the self-assembly of l/d-phenylglycine-based amphiphiles (l/d-PhgC16) and Cu(II) into chiral supramolecular catalysts in the methanol/water solution mixture is described, which features the interesting M/P nanohelices (diameter ≈8 nm) and mostly well-aligned M/P nanoribbons (NRs). The M/P supramolecular catalysts show both high but inverse enantioselectivity (>90% ee) in Diels-Alder reactions, while their monomeric counterparts display nearly racemic products. Analysis of the catalytic results suggests the outstanding enantioselectivities are closely related to the specific stereochemical microenvironment provided by the arrangement of the amphiphiles in the supramolecular assembly. Based on the experimental evidence of chirality transfer from supramolecular nanohelices to coordinated Cu(II) and substrate aza-chalcone and the molecular dynamics simulations, the enantioselective catalytic mechanisms are proposed. Moreover, the relationships between molecular structures of amino acid amphiphiles (the hydrophilic head group and hydrophobic alkyl chain length) in supramolecular catalysts and enantioselectivity in Diels-Alder reactions are elaborated.

Biostable hydrogels consisting of hybrid β-sheet fibrils assembled by a pair of enantiomeric peptides

The assembly of chiral peptides facilitates the formation of diverse supramolecular structures with unique physicochemical and biological properties. However, the effects of chirality on peptide assembly and resulting hydrogel properties remain underexplored. In this study, we systematically investigated the assembly propensity, morphology, and biostability of mixture of a pair of enantiomeric peptides LELCLALFLF (ECF-5) and DEDCDADFDF (ecf-5) at various ratios. Results indicate the development of β-sheet fibrils, ultimately leading to the formation of self-supporting hybrid hydrogels. The hydrogel formed at a ratio of 1:1 exhibits a significantly lower storage modulus (G') than of the ratios of 0:1, 1:3, 3:1 and 1:0 (nD/nL; same below). Kink-separated fragments of approximately 100 nm in length predominate at ratios of 1:3 and 3:1, compared with the smooth fibrils at other ratios, probably attributed to an alternating arrangement of the co-assembled and self-assembled peptide fragments. The introduction of ecf-5 to the hybrid hydrogels improves resistance to proteolytic digestion and maintains commendable biocompatibility in both MIN6 and HUVECs cells. These findings provide valuable insights into the development of hydrogels with tailored properties, positing them potential scaffolds for 3D cell culture and tissue engineering.

Fabrication strategies for chiral self-assembly surface

Chiral self-assembly is the spontaneous organization of individual building blocks from chiral (bio)molecules to macroscopic objects into ordered superstructures. Chiral self-assembly is ubiquitous in nature, such as DNA and proteins, which formed the foundation of biological structures. In addition to chiral (bio) molecules, chiral ordered superstructures constructed by self-assembly have also attracted much attention. Chiral self-assembly usually refers to the process of forming chiral aggregates in an ordered arrangement under various non-covalent bonding such as H-bond, π-π interactions, van der Waals forces (dipole-dipole, electrostatic effects, etc.), and hydrophobic interactions. Chiral assembly involves the spontaneous process, which followed the minimum energy rule. It is essentially an intermolecular interaction force. Self-assembled chiral materials based on chiral recognition in electrochemistry, chiral catalysis, optical sensing, chiral separation, etc. have a broad application potential with the research development of chiral materials in recent years.

Chiral Supramolecular Organogel Constructed Using Riboflavin and Melamine: Its Application in Photo-Catalyzed Colorimetric Chiral Sensing and Enantioselective Adsorption

The synthesis of a chiral supramolecular organogel via the hierarchical helical self-assembly of optically active riboflavin and melamine derivatives is described herein. Owing to the photocatalysis of riboflavin and the supramolecular chirality induced in the helically stacked riboflavin/melamine complex, the gel is observed to act as a light-stimulated chiral sensor of optically active alcohols by detecting the change in color from yellow to green. The gel also served as an efficient chiral adsorbent, enabling optical resolution of a racemic compound with high chiral recognition ability.

Macroscopic Helical Assembly of One-Dimensional Coordination Polymers: Helicity Inversion Triggered by Solvent Isomerism

Assembling macroscopic helices with controllable chirality and understanding their formation mechanism are highly desirable but challenging tasks for artificial systems, especially coordination polymers. Here, we utilize solvents as an effective tool to induce the formation of macroscopic helices of chiral coordination polymers (CPs) and manipulate their helical sense. We chose the Ni/R-,S-BrpempH2 system with a one-dimensional tubular structure, where R-,S-BrpempH2 stands for R-,S-(1-(4-bromophenyl)ethylaminomethylphosphonic acid). The morphology of the self-assemblies can be controlled by varying the cosolvent in water, resulting in the formation of twisted ribbons of R-,S-Ni(Brpemp)(H2O)·H2O (R-,S-2T) in pure H2O; needle-like crystals of R-,S-Ni(Brpemp)(H2O)2·1/3CH3CN (R-,S-1C) in 20 vol % CH3CN/H2O; nanofibers of R-,S-Ni(Brpemp)(H2O)·H2O (R-,S-3F) in 20-40 vol % methanol/H2O or ethanol/H2O; and superhelices of R-,S-Ni(Brpemp)(H2O)·H2O (R-,S-4H or 5H) in 40 vol % propanol/H2O. Interestingly, the helicity of the superhelix can be controlled by using a propanol isomer in water. For the Ni/R-BrpempH2 system, a left-handed superhelix of R-4H(M) was obtained in 40 vol % NPA/H2O, while a right-handed superhelix of R-5H(P) was isolated in 40 vol % IPA/H2O. These results were rationalized by theoretical calculations. Adsorption studies revealed the chiral recognition behavior of these compounds. This work may contribute to the development of chiral CPs with a macroscopic helical morphology and interesting functionalities.

Supramolecular Polyaniline-Metal Ion as Chiral Nanozymes for Enantioselective Catalysis

Understanding origin of asymmetric information encoded on chiral nanozymes is important in mediating enantioselective catalysis. Herein, the supramolecular chiral nanozymes constructed from P/M-polyaniline (P/M-PANI) nanotwists and metal ions (M2+ , M = Cu, Ni, Co, and Zn) are designed through thioglycolic acid (TA) without chiral molecules to show the regulated catalytic efficiency and enantioselectivity. With combination of chiral environment from supramolecular scaffolds and catalytic center from metal ions, the P-PANI-TA-M2+ as nanozymes show preference to 3,4-dihydroxy-S-phenylalanine (S-DOPA) oxidation while the M-PANI-TA-M2+ show better selectivity to R-DOPA oxidation. Among them, though the Cu2+ doped supramolecular nanotwists show the highest catalytic efficiency, the Co2+ doped ones with moderate catalytic efficiency can exhibit the best enantioselectivity with select factor as high as 2.07. The molecular dynamic (MD) simulation clarifies the mechanism of enantioselective catalysis caused by the differential kinetics with S/R-DOPA enantiomers adsorbed on chiral PANI surface and free in solution. This work systematically studies the synergistic effect between the chiral supramolecular nanostructures assembled by achiral species and metal ions as peroxidase-like catalytic centers to regulate the enantioselectivity, providing deep understanding of the origin of asymmetric catalysis and serving as strong foundation to guide the design of nanozymes with high enantioselectivity.

Rh-coordinated histidyl bolaamphiphile assembly: a catalyst for the isomerization of cis-stilbene and cis-alkene

In this study, we present a colloidal assembly of histidyl bolaamphiphiles whose imidazoles coordinate with rhodium ions (HisC7[Rh]) to exhibit catalytic isomerization activity for cis-stilbene and cis-alkene molecules. The histidyl bolaamphiphiles self-assemble to form a soft scaffold that functions analogously to an apoenzyme. This scaffold exposes multiple histidyl imidazoles and carboxylates on its surface, to which rhodium ions bind, generating catalytically active sites. The Rh coordination with the biochemical functional groups was verified through comprehensive vibrational spectroscopy and calorimetry. The colloidal HisC7[Rh] demonstrated a significant catalytic effect on the isomerization of cis- to trans-stilbene under mild H2 conditions, resulting in 69% yield of trans-stilbene. In contrast, when Rh(cod)2BF4 was employed as a control catalyst, only the hydrogenated products of bibenzyl were obtained. These findings underscore the crucial role of histidyl motifs in exhibiting unique catalytic isomerization activity through the coordination with Rh. The catalytic activity of HisC7[Rh] is governed by several factors, such as rhodium content, solvent composition, temperature, and H2 pressure. Moreover, HisC7[Rh] displayed moderate isomerization activity towards not only stilbene but also unsaturated fatty acid isomers, highlighting its expansive potential as an isomerization catalyst.

Catalysis of a Diels-Alder Reaction between Azachalcones and Cyclopentadiene by a Recyclable Copper(II)-PEIP Metal-Organic Framework

Metal-organic frameworks (MOFs) have attracted considerable interest as emerging heterogeneous catalysts for organic transformations of synthetic utility. Herein, a Lewis-acidic MOF, {[Cu3(PEIP)2(5-NH2-mBDC)(DMF)]·7DMF}∞, denoted as Cu(ΙΙ)-PEIP, has been synthesized via a one-pot process and deployed as an efficient heterogeneous catalyst for a Diels-Alder cycloaddition. Specifically, the [4 + 2] cycloaddition of 13 substituted azachalcone dienophiles with cyclopentadiene has been investigated. MOF-catalyzed reaction conditions were optimized, leading to the selection of water as the solvent, in the presence of 10% mol sodium dodecyl sulfate (SDS) to address substrate solubility. The Cu(II)-PEIP catalyst showed excellent activity under these green and mild conditions, exhibiting comparable or, in some cases, superior efficiency to a homogeneous catalyst often employed in Diels-Alder reactions, namely, Cu(OTf)2. The nature of the azachalcone substituent played a significant role in the reactivity of the dienophiles, with electron-withdrawing (EW) substituents enhancing conversion and electron-donating (ED) ones exhibiting the opposite effect. Coordinating substituents appeared to enhance the endo selectivity. Importantly, the Cu(II)-PEIP catalyst can be readily isolated from the reaction mixture and recycled up to four times without any significant reduction in conversion or selectivity.

Self-Assembly, In Vitro Gene Transfection, and Antimicrobial Activity of Biodegradable Cationic Bolaamphiphiles

Bolaamphiphiles or bolaforms have drawn particular interest in drug and gene delivery, and studies of bolaforms have been growing continuously. Bolaforms, due to their unique structure, exhibit specific self-assembly behavior in water. The present work aims to develop biodegradable cationic bolaforms with a better gene transfection ability. In this work, a novel cationic bolaform (Bola-1) with head groups bearing hydroxyl (OH) functionality was designed and synthesized to investigate self-assembly and gene transfection efficiency. The self-assembly behavior of Bola-1 in water was compared with that of the hydrochloride salt (Bola-2) of its precursor molecule to investigate the effect of the -OH functionality on their solution properties. Several techniques, including surface tension, electrical conductivity, fluorescence probe, calorimetry, dynamic light scattering, and atomic force microscopy, were employed for the physicochemical characterization of Bola-1 and Bola-2. Despite the presence of polar urea groups in the spacer chain, both bolaforms were found to form spherical or elongated micelles above a relatively low critical aggregation concentration (CAC). The presence of the OH group was found to significantly affect the CAC value. The results of calorimetric measurements suggested a thermodynamically favorable aggregate formation in salt-free water. Despite stronger binding efficiency with calf thymus DNA, in vitro gene transfection studies performed using adherent cell Hek 293 suggested that both Bola-1 and Bola-2 have gene transfection efficiency comparable to that of turbofectamine standard. Both bolaforms were found to exhibit significant in vitro cytotoxicity at higher concentrations. Also, the bolaforms showed beneficial antibacterial activity at higher concentrations.

Kinetic Controlled Chirality Transfer and Induction in 2D Hydrogen-Bonding Assemblies of Glycylglycine on Au(111)

Chirality transfer is of vital importance that dominates the structure and functionality of biological systems and living matters. External physical stimulations, e.g. polarized light and mechanical forces, can trigger the chirality symmetry breaking, leading to the appearance of the enantiomeric entities created from a chiral self-assembly of achiral molecule. Here, several 2D assemblies with different chirality, synthesized on Au(111) surface by using achiral building blocks - glycylglycine (digly), the simplest polypeptide are reported. By delicately tuning the kinetic factors, i.e., one-step slow/rapid deposition, or stepwise slow deposition with mild annealing, achiral square hydrogen-bond organic frameworks (HOF), homochiral rhombic HOF and racemic rectangular assembly are achieved, respectively. Chirality induction and related symmetry broken in assemblies are introduced by the handedness (H-bond configurations in principle) of the assembled motifs and then amplified to the entire assemblies via the interaction between motifs. The results show that the chirality transfer and induction of biological assemblies can be tuned by altering the kinetic factors instead of applying external forces, which may offer an in-depth understanding and practical approach to peptide chiral assembly on the surfaces and can further facilitate the design of desired complex biomolecular superstructures.

Biomimetic mineralization based on self-assembling peptides

Biomimetic science has attracted great interest in the fields of chemistry, biology, materials science, and energy. Biomimetic mineralization is the process of synthesizing inorganic minerals under the control of organic molecules or biomolecules under mild conditions. Peptides are the motifs that constitute proteins, and can self-assemble into various hierarchical structures and show a high affinity for inorganic substances. Therefore, peptides can be used as building blocks for the synthesis of functional biomimetic materials. With the participation of peptides, the morphology, size, and composition of mineralized materials can be controlled precisely. Peptides not only provide well-defined templates for the nucleation and growth of inorganic nanomaterials but also have the potential to confer inorganic nanomaterials with high catalytic efficiency, selectivity, and biotherapeutic functions. In this review, we systematically summarize research progress in the formation mechanism, nanostructural manipulation, and applications of peptide-templated mineralized materials. These can further inspire researchers to design structurally complex and functionalized biomimetic materials with great promising applications.

Triple Thorpe-Ingold Effect in the Synthesis of 18-Membered C3 Symmetric Lactams Stacking as Endless Supramolecular Tubes

Three C₃ symmetric macrolactams were very efficiently cyclized from their linear precursors. Adequately located substituents are responsible for the enhancement of reactivity that is not observed in the unsubstituted parent. DFT calculations show that the properly folded cyclization precursor, the reactive conformer, is more populated than other conformers, leading to a decrease of free energy of activation. The crystal structure of the ring substituted with three very bulky esters indicates that tubular stacking is preserved.

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.

pH and Salt-Assisted Macroscopic Chirality Inversion of Gadolinium Coordination Polymer

The precise adjustment of handedness of helical architectures is important to regulate their functions. Macroscopic chirality inversion has been achieved in organic supramolecular systems by pH, metal ions, solvents, chiral and non-chiral additives, temperature, and light, but rarely in coordination polymers (CPs). In particular, salt-assisted macroscopic chirality inversion has not been reported. In this work, we carried out a systematic investigation on the role of pH and salt in regulating the morphology of CPs based on Gd(NO₃)₃ and R-(1-phenylethylamino)methylphosphonic acid (R-pempH₂). Without extra NO₃^-, the chirality inversion from the left-handed superhelix R-M to the right-handed superhelix R-P can be achieved by pH modulation from 3.2 to 3.8. The addition of NaNO₃ (2.0 eq) at pH 3.8 results in an inversion of chiral sense from R-P to R-M as a pure phase. To our knowledge, this is the first example of salt-assisted macroscopic helical inversion in artificial systems.

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.

Controlling supramolecular filament chirality of hydrogel by co-assembly of enantiomeric aromatic peptides

Supramolecular chirality plays an indispensable role in living and synthetic systems. However, the generation and control of filament chirality in the supramolecular hydrogel of short peptides remains challenging. In this work, as the first example, we report that the heterodimerization of the enantiomeric mixture controls the alignment, chirality, and stiffness of fibrous hydrogels formed by aromatic building blocks. The properties of the resulting racemic hydrogel could not be achieved by either pure enantiomer. Cryo-EM images indicate that the mixture of L and D enantiomers forms chiral nanofibers, the percentage of which can be readily controlled through stoichiometric co-assembly of heterochiral enantiomers. 2D NOESY NMR and diffusion-ordered NMR spectroscopy reveal that heterodimerization of enantiomers plays a crucial role in the formation of chiral nanofibers. Further mechanistic studies unravel the mechanism of supramolecular chirality formation in this two-component system. Molecular dynamics simulations confirm that the intermolecular hydrogen bond and π–π interaction of heterodimers play important roles in forming a chiral hydrogel. Furthermore, regulation of the adhesion and morphology of mammalian cells is achieved by tuning the relative ratio of L and D enantiomers at the same concentration. This work illustrates a novel strategy to control the supramolecular chirality of aromatic peptide hydrogels for materials science.

Self-Assembled Copper Metallogel Bearing Terpyridine and Its Application as a Catalyst for the Click Reaction in Water

Metallogels have attracted a great deal of interest because of their intriguing properties and applications in chemsensors, batteries, catalysis, and other fields. In this work, a novel ligand bearing terpyridine and hydroxyamine units was designed and synthesized. The ligand selectively gelated with copper ions in water by heating and cooling or sonication. Different physicochemical studies [Fourier transform infrared, ultraviolet-visible (UV-vis), electron paramagnetic resonance (EPR), scanning electron microscopy, X-ray diffraction, and rheology] were conducted to characterize the gels. We show that coordination interaction, π-π interaction, and noncovalent interaction had obvious effects on the properties of the gel. Additionally, a stable radical hydrogel could be obtained by ultrasound treatment, which was accompanied by color variation from green to blue. This was further confirmed by UV-vis and EPR experiments. Furthermore, the copper metallogels were developed as catalysts for the preparation of 1,2,3-triazole derivatives in water at 25 °C. Although various types of catalysts have been investigated, the use of metallogels as catalysts for the click reaction in water has been scarce. This strategy shows the process is simple, affords a high yield, and is "green" and economical.

Guanosine Borate Hydrogel and Self-Assembled Nanostructures Capable of Enantioselective Aldol Reaction in Water

A guanosine-based hydrogel formed by the self-assembly of guanosine and 4-((l-prolinamide)methyl)phenylboronic acid was constructed. The G quartets were selectively stabilized by K⁺ ions to form a self-supporting transparent hydrogel. These guanosine-derived assemblies were used to catalyze the aldol reaction in water without any additives, affording desirable conversion and enantioselectivity of the product. The controlled assays of small-molecule components indicated that the stable assemblies were the definite species that achieved high enantioselective catalysis. The current catalytic system can be readily recovered by simple extraction and still acquired good performance of the reaction after four cycles.

Hierarchical self-assembly into chiral nanostructures

One basic principle regulating self-assembly is associated with the asymmetry of constituent building blocks or packing models. Using asymmetry to manipulate molecular-level devices and hierarchical functional materials is a promising topic in materials sciences and supramolecular chemistry. Here, exemplified by recent major achievements in chiral hierarchical self-assembly, we show how chirality may be utilized in the design, construction and evolution of highly ordered and complex chiral nanostructures. We focus on how unique functions can be developed by the exploitation of chiral nanostructures instead of single basic units. Our perspective on the future prospects of chiral nanostructures via the hierarchical self-assembly strategy is also discussed.

Three-level hierarchical self-assembly of azobenzene conjugated phenylalanines into superhelical nanostructures with light-switchable helicity

Photosensitive azobenzene conjugated phenylalanines can self-assemble into a series of hierarchical superhelices, which can reversibly transform into achiral nanorods via light stimuli.

Anisotropic nanomaterials for asymmetric synthesis

The production of enantiopure chemicals is an essential part of modern chemical industry. Hence, the emergence of asymmetric catalysis led to dramatic changes in the procedures of chemical synthesis, and now it provides the most advantageous and economically executable solution for large-scale production of chiral chemicals. In recent years, nanostructures have emerged as potential materials for asymmetric synthesis. Indeed, on the one hand, nanomaterials offer great opportunities as catalysts in asymmetric catalysis, due to their tunable absorption, chirality, and unique energy transfer properties; on the other hand, the advantages of the larger surface area, increased number of unsaturated coordination centres, and more accessible active sites open prospects for catalyst encapsulation, partial or complete, in a nanoscale cavity, pore, pocket, or channel leading to alteration of the chemical reactivity through spatial confinement. This review focuses on anisotropic nanomaterials and considers the state-of-the-art progress in asymmetric synthesis catalysed by 1D, 2D and 3D nanostructures. The discussion comprises three main sections according to the nanostructure dimensionality. We analyze recent advances in materials and structure development, discuss the functional role of the nanomaterials in asymmetric synthesis, chirality, confinement effects, and reported enantioselectivity. Finally, the new opportunities and challenges of anisotropic 1D, 2D, and 3D nanomaterials in asymmetric synthesis, as well as the future prospects and current trends of the design and applications of these materials are analyzed in the Conclusions and outlook section.

Controllable Macroscopic Chirality of Coordination Polymers through pH and Anion-Mediated Weak Interactions

Helical architectures with controllable helical sense bias have recently attracted considerable interest for mimicking biological helices and developing novel chiral materials. Coordination polymers (CPs), composed of metal ion nodes and organic linkers, are intriguing systems showing tunable structures and functions. However, CPs with helical morphologies have rarely been explored so far. Particularly, chirality inversion through external stimulus has not been achieved in helical CPs. In this work, we carried out an in-depth investigation on the self-assembly of 1D gadolinium(III) phosphonate CPs using GdX₃ (X=Cl, Br, I) and Gd(RSO₃ ) (R=CH₃ , C₆ H₅ , CF₃ ) as metal sources and R-(1-phenylethylamino)methyl phosphonic acid (R-pempH₂ ) as ligand. Superhelices were formed by precise control of the interchain interactions through different intercalated anions. Furthermore, the twisting direction of superhelices could be controlled by synergistic effect of anions and pH. This study may provide a new route to fabricate helical nanostructures of CPs with a desirable chiral sense and help understand the inner mechanism of the self-assembly process of macroscopic helical structures of molecular systems.

Hierarchical Chiral Supramolecular Nanoarchitectonics with Molecular Detection: Helical Structure Controls upon Self-Assembly and Coassembly

The morphological transformation from microspheres to helical supramolecular nanofibers with controllable handedness is achieved by the introduction of molecular chirality based on amino acid derivatives (TDAP), and the chirality of the supramolecular architectures that are achieved is nullified through the coassembly of the equivalent TDAP enantiomers. The molecular detection of achiral melamine based on the R-TDAP-COOH supramolecular system is achieved by the appearance of helicity and inversion.

Static Retention of Dynamic Chiral Arrangements for Achiral Shear Thinning Metal-Organic Colloids

Chiral compounds are known to be important not only because they are the fundamental components of living organisms, but also for their unique chiroptical properties. In recent years, scientists have fabricated several chiral organic supramolecular aggregates by using chiral physical fields, such as vortex flow. Herein, the relationship between dynamic chiroptical properties and rheological nature is discussed, suggesting the shear thinning properties of non-Newtonian fluids might help colloidal particles adopt a chiral arrangement in vortices. Furthermore, the storage modulus of colloids could be increased by adding a linking agent, which successfully kept the dynamic chiroptical properties in the static state. Moreover, the salt effect on the host-guest interaction involved in the colloids was studied, the results suggested a significant enhancement of the transferred dynamic circular dichroism for the achiral guest molecule.

Self-Assembling Peptidic Bolaamphiphiles for Biomimetic Applications

Bolaamphiphile, which is a class of amphiphilic molecules, has a unique structure of two hydrophilic head groups at the ends of the hydrophobic center. Peptidic bolaamphiphiles that employ peptides or amino acids as their hydrophilic groups exhibit unique biochemical activities when they self-organize into supramolecular structures, which are not observed in a single molecule. The self-assembled peptidic bolaamphiphiles hold considerable promise for imitating proteins with biochemical activities, such as specific affinity toward heterogeneous substances, a catalytic activity similar to a metalloenzyme, physicochemical activity from harmonized amino acid segments, and the capability to encapsulate genes like a viral vector. These diverse activities give rise to large research interest in biomaterials engineering, along with the synthesis and characterization of the assembled structures. This review aims to address the recent progress in the applications of peptidic bolaamphiphile assemblies whose densely packed peptide motifs on their surface and their stacked hydrophobic centers exhibit unique protein-like activity and designer functionality, respectively.

Hierarchically Evolved Supramolecular Chirality Mediated by Arene-Perfluoroarene Interaction

Rational utilization of diverse weak forces in directing multiple-constituent chiral coassemblies is of vital importance in fabricating functional chiroptical materials. In this work, arene-perfluoroarene (AP) and hydrogen bonds were orthogonally employed to afford synergistic binary and ternary coassemblies. On the supramolecular scale, amino acids were connected to achiral pyrene moieties, which packed into supramolecular tilt chirality individually. The modified aromatic amino acids coassembled with melamine and octafluoronaphthalene (OFN) through multiple hydrogen bond and AP interactions, respectively, to construct binary and ternary systems. The introduction of hydrogen bonds and AP interactions shall alter the nanostructures and luminescent properties. Emergence of macroscopic chirality at nanoscale was realized, accompanied by the inversion of circularly polarized luminescence. These interactions working in an orthogonal way regulated the supramolecular chirality, emission properties, nanostructure transformation, and chiroptical activities, which enriched the protocols in designing functional chiral composites.

Synthesis of a Stable Benzoxazole Gel from an Imine Gel for Adsorption and Catalysis

Developing stable gel materials for adsorption and catalysis is one of the major themes of gel materials. However, it has been proven to be challenging to achieve them from small molecules. Herein, an imine gel is developed from tetra-aldehyde 4-{2,2-bis[(4-formylphenoxy)methyl]-3-(4-formylphenoxy)propoxy}benzaldehyde (A4) and 3,3'-dihydroxybenzidine (B2) based on dynamic covalent chemistry. The unstable A4B2-imine gel is further converted into a stable aromatic benzoxazole-linked A4B2-benzoxazole gel via oxidative cyclization, which has significantly improved chemical stability under acidic and basic conditions. Benefiting from the stability under acidic conditions, the A4B2-benzoxazole gel is used for Pd(II) adsorption and the adsorption capacity is 250 mg g^-1. After PdCl₂ immersion and reduction, palladium nanoparticles with a size distribution of 1.3-14.7 nm are encapsulated by the network structure of the stable porous benzoxazole gel matrix. The Pd@A4B2-benzoxazole gel exhibits high catalytic activity toward the reduction of toxic hexavalent chromium Cr(VI) (reaction rate constant = 0.0377 min^-1), while there is no significant decrease in the catalytic efficiency after five cycles.

Macroscalar Helices Co-Assembled from Chirality-Transferring Temperature-Responsive Carbohydrate-Based Bolaamphiphiles and 1,4-Benzenediboronic Acid

We present the first example of macroscalar helices co‐assembled from temperature‐responsive carbohydrate‐based bolaamphiphiles (CHO‐Bolas) and 1,4‐benzenediboronic acid (BDBA). The CHO‐Bolas contained hydrophilic glucose or mannose moieties and a hydrophobic coumarin dimer. They showed temperature‐responsive reversible micelle‐to‐vesicle transition (MVT) in aqueous solutions. After the binding of carbohydrate moieties with boronic acids of BDBA in their alkaline solutions, right‐handed helices were formed via the temperature‐driven chirality transfer of d‐glucose or d‐mannose from the molecular to supramolecular level. These helices were co‐assembled by unreacted BDBA, boronate esters (B−O−C bonds) between CHO‐Bolas and BDBA, as well as boroxine anhydrides (B−O−B bonds) of self‐condensed BDBA. After heating at 300 °C under nitrogen, the helices displayed excellent morphological stability. Moreover, they emitted bright blue luminescence caused by strong self‐condensation of BDBA and decomposition of coumarin dimers.

Supramolecular Chirality Transfer toward Chiral Aggregation: Asymmetric Hierarchical Self-Assembly

Self-assembly, as a typical bottom-up strategy for the fabrication of functional materials, has been applied to fabricate chiral materials with subtle chiral nanostructures. The chiral nanostructures exhibit great potential in asymmetric catalysis, chiral sensing, chiral electronics, photonics, and even the realization of several biological functions. According to existing studies, the supramolecular chirality transfer process combined with hierarchical self-assembly plays a vital role in the fabrication of multiscale chiral structures. This progress report focuses on the hierarchical self-assembly of chiral or achiral molecules that aggregate with asymmetric spatial structures such as twisted bands, helices, and superhelices in different environments. Herein, recent studies on the chirality transfer induced self-assembly based on a variety of supramolecular interactions are summarized. In addition, the influence of different environments and the states of systems including solutions, condensed states, gel systems, interfaces on the asymmetric hierarchical self-assembly, and the expression of chirality are explored. Moreover, both the driving forces that facilitate chiral bias and the supramolecular interactions that play an important role in the expression, transfer, and amplification of the chiral sense are correspondingly discussed.

Inverse Evolution of Helicity from the Molecular to the Macroscopic Level Based on N-Terminal Aromatic Amino Acids

Precise control of the emergence of macroscopic helicity with specific handedness is promising in rationally designing chiral nanomaterials, but it is rather challenging. Herein, we present a protocol to address the transmission of helicity at a molecularly resolved level to a macroscopically resolved level, in which process supramolecular chirality undergoes an inversion. A series of N-terminal aromatic amino acids could self-assemble in water, enabling the occurrence of helicity at the molecularly resolved scale, evidenced by the single crystal structure and chiroptical responses. While it failed to transmit the helicity to the macroscopic scale for individual self-assembly, the coassembly with small organic binder through hydrogen bonding interactions allows for the emergence of helical structures at the nano/micrometer scale. Experimental and theoretical results demonstrate that the introduction of extra hydrogen bonds enables a moderate crystallinity of coassemblies with remaining one-dimensional orientation to enhance the helical growth. The transmission of helicity to higher levels by coassembly is accompanied by the helicity inversion, resulting from the exchange of hydrogen bonds. This study presents a rational protocol to precisely control the emergence of macroscopic helicity from molecularly resolved helicity with finely tailored handedness, providing a deeper understanding of the chirality origin in the assembled systems in order to facilitate the design and construction of functional chiral nanomaterials.

Controlling Ultra-Large Optical Asymmetry in Amorphous Molecular Aggregations

Although ultra-large optical asymmetry appears in crystalline materials, distractions from the mesoscopic ordering often causes inauthenticity in chiropticity. In amorphous materials, however, it remains challenging and elusive to achieve large chiropticity. Herein, we report the quantitative control of chiral amplification, on amorphous supramolecular structures of cholesteryl-linked bis(dipyrrinato)zinc(II), to an exceptionally high level. A proper chiral packing of the building block at several molecular scale considerably contributes to the absorptive dissymmetry factor g_abs , although the system is overall disordered. The intense and tunable aggregation strength renders a variable g_abs value up to +0.10 and +0.31 in the solution and in film state. On this basis, a superior ON-OFF switching of chiropticity is realized under external stimuli. This work establishes a general design principle to control over ultra-large optical asymmetry on a wider scope of chiral materials.