DNA‐Decorated,Helically Twisted Nanoribbons: A Scaffold for the Fabrication of One‐Dimensional,Chiral, Plasmonic Nanostructures

Crafting of chiral plasmonic nanostructures is extremely important and challenging. DNA‐directed organization of nanoparticle on a chiral template is the most appealing strategy for this purpose. Herein, we report a supramolecular approach for the design of DNA‐decorated, helically twisted nanoribbons through the amphiphilicity‐driven self‐assembly of a new class of amphiphiles derived from DNA and hexaphenylbenzene (HPB). The ribbons are self‐assembled in a lamellar fashion through the hydrophobic interactions of HPB. The transfer of molecular chirality of ssDNA into the HPB core results in the bias of one of the chiral propeller conformations for HPB and induces a helical twist into the lamellar packing, and leads to the formation of DNA‐wrapped nanoribbons with M‐helicity. The potential of the ribbon to act as a reversible template for the 1D chiral organization of plasmonic nanomaterials through DNA hybridization is demonstrated.     

Dynamic Formation of Hybrid Peptidic Capsules by Chiral Self‐Sorting and Self‐Assembly

Owing to their versatility and biocompatibility, peptide‐based self‐assembled structures constitute valuable targets for complex functional designs. It is now shown that artificial capsules based on β‐barrel binding motifs can be obtained by means of dynamic covalent chemistry (DCC) and self‐assembly. Short peptides (up to tetrapeptides) are reversibly attached to resorcinarene scaffolds. Peptidic capsules are thus selectively formed in either a heterochiral or a homochiral way by simultaneous and spontaneous processes, involving chiral sorting, tautomerization, diastereoselective induction of inherent chirality, and chiral self‐assembly. Self‐assembly is shown to direct the regioselectivity of reversible chemical reactions. It is also responsible for shifting the tautomeric equilibrium for one of the homochiral capsules. Two different tautomers (keto‐enamine hemisphere and enol‐imine hemisphere) are observed in this capsule, allowing the structure to adapt for self‐assembly.     

Cooperative Chirality and Sequential Energy Transfer in a Supramolecular Light‐Harvesting Nanotube

By constructing a supramolecular light‐harvesting chiral nanotube in the aqueous phase, we demonstrate a cooperative energy and chirality transfer. It was found that a cyanostilbene‐appended glutamate compound (CG) self‐assembled into helical nanotubes exhibiting both supramolecular chirality and circularly polarized luminescence (CPL). When two achiral acceptors, ThT and AO, with different energy bands were co‐assembled with the nanotube, the CG nanotube could transfer its chirality to both of the acceptors. The excitation energy could be transferred to ThT but only be sequentially transferred to AO. During this process, the CPL ascribed to the acceptor could be sequentially amplified. This work provides a new insight into the understanding the cooperative chirality and energy transfer in a chiral supramolecular system, which is similar to the natural light‐harvesting antennas.     

Hierarchical Self‐Assembly in Liquid‐Crystalline Block Copolymers Enabled by Chirality Transfer

Helical topological structures are often found in chiral biological systems, but seldom in synthesized polymers. Now, controllable microphase separation of amphiphilic liquid‐crystalline block copolymers (LCBCs) consisting of hydrophilic poly(ethylene oxide) and hydrophobic azobenzene‐containing poly(methylacrylate) is combined with chirality transfer to fabricate helical nanostructures by doping with chiral additives (enantiopure tartaric acid). Through hydrogen‐bonding interactions, chirality is transferred from the dopant to the aggregation, which directs the hierarchical self‐assembly in the composite system. Upon optimized annealing condition, helical structures in film are fabricated by the induced aggregation chirality. The photoresponsive azobenzene mesogens in the LCBC assist photoregulation of the self‐assembled helical morphologies. This allows the construction and non‐contact manipulation of complicated nanostructures.     

Dual Upconverted and Downconverted Circularly Polarized Luminescence in Donor–Acceptor Assemblies

Through mimicking both the chiral and energy transfer in an artificial self‐assembled system, not only was chiral transfer realized but also a dual upconverted and downconverted energy transfer system was created that emit circularly polarized luminescence. The individual chiral π‐gelator can self‐assemble into a nanofiber exhibiting supramolecular chirality and circularly polarized luminescence (CPL). In the presence of an achiral sensitizer Pd^II octaethylporphyrin derivative, both chirality transfer from chiral gelator to achiral sensitizer and triplet‐triplet energy transfer from excited sensitizer to chiral gelator could be realized. Upconverted CPL could be observed through a triplet–triplet annihilation photon upconversion (TTA‐UC), while downconverted CPL could be obtained from chirality‐transfer‐induced emission of the achiral sensitizer. The interplay between chiral energy acceptor and achiral sensitizer promoted the communication of chiral and excited energy information.     

Helical Nanostructures: Chirality Transfer and a Photodriven Transformation from Superhelix to Nanokebab

Photosensitive cinnamic acid conjugated glutamides were designed to demonstrate photocontrolled hierarchical chirality transfer and switching in self‐assembled systems. In methanol, the cinnamic acid derivatives self‐assembled into superhelices, which could be switched into nanokebabs upon UV irradiation. These two nanostructures showed opposite helicity. The chiral nanostructures could further convey their chirality to achiral fluorescent molecules and result in the emission of circularly polarized luminescence (CPL). Remarkably, the CPL followed the helicity of the chiral nanostructure rather than the inherent molecular chirality. Photodriven dimerization of the cinnamic moiety lead to a significant change in molecular packing and subsequent switching of the helicity of the formed nanostructures.     

Inversion of the Supramolecular Chirality of Nanofibrous Structures through Co‐Assembly with Achiral Molecules

To understand the behavior of chiral nanostructures, it is of critical importance to study how achiral molecules regulate the chirality of such nanostructures and what the main driving forces for the regulation processes are. In this work, the supramolecular chirality of helical nanofibers consisting of phenylalanine‐based enantiomers is inverted by achiral bis(pyridinyl) derivatives through co‐assembly. This inversion is mainly mediated by intermolecular hydrogen bonding interactions between the achiral additives and the chiral molecules, which may induce stereoselective interactions and different reorientations for the assembled molecules, as confirmed by calculations. This work not only exemplifies a feasible method to invert the helicity of chiral nanostructures by the addition of achiral molecules, but also provides a method to explore their functions in environments where chiral and achiral molecules are in close proximity.     

Self‐Assembled Ultralong Chiral Nanotubes and Tuning of Their Chirality Through the Mixing of Enantiomeric Components

Enantiomeric L ‐ or D ‐glutamic acid based lipids were designed and their self‐assembly was investigated. It was found that at a certain concentration, either L ‐ or D ‐enantiomeric derivatives could self‐assemble in absolute alcohol to form a white organogel, which was composed of ultralong nanotubes with an aspect ratio higher than 1000. Further investigations revealed that these nanotubes were in chiral forms. The chirality of the nanotubes was determined by that of the enantiomers employed. In addition, when D and L enantiomers were mixed in different ratios, the nanotube could be tuned consecutively from nanotubes with a helical seam to nanotwists, the chirality of which being determined by the excess enantiomer in the mixed systems. In the case of an equimolar mixture of the enantiomers, flat nanoplates instead of helical nanotubes or nanotwists were obtained. The FTIR vibrational data and XRD layer‐distance values showed a consecutive change as a function of the enantiomeric excess. It was further revealed that the slightly stronger interaction between D –L enantiomeric pairs than that between D –D or L –L pairs was responsible for the formation of the diverse self‐assembled nanostructures.     

Programmable Supra‐Assembly of a DNA Surface Adapter for Tunable Chiral Directional Self‐Assembly of Gold Nanorods

An important challenge in molecular assembly and hierarchical molecular engineering is to control and program the directional self‐assembly into chiral structures. Here, we present a versatile DNA surface adapter that can programmably self‐assemble into various chiral supramolecular architectures, thereby regulating the chiral directional “bonding” of gold nanorods decorated by the surface adapter. Distinct optical chirality relevant to the ensemble conformation is demonstrated from the assembled novel stair‐like and coil‐like gold nanorod chiral metastructures, which is strongly affected by the spatial arrangement of neighboring nanorod pair. Our strategy provides new avenues for fabrication of tunable optical metamaterials by manipulating the directional self‐assembly of nanoparticles using programmable surface adapters.     

Driving Helical Packing of a Cyanine Dye on Dendron Nanofiber: Gel‐Shrinkage‐Triggered Chiral H‐Aggregation and Enhanced Enantiodiscrimination

An intelligent molecular hydrogel with a volume phase transition was constructed to regulate the chiral packing of a well‐known cyanine dye on a dynamically self‐assembled chiral nanofiber by using a pH trigger. During the shrinkage of the gel, the chiral nanofiber hierarchically assembled into a superhelix and simultaneously drove the dye molecules to stack, from a predominantly monomer form, in an unexpected helical H‐aggregation manner. Through such a transformation, the supramolecular chirality of the system was significantly enhanced and a new property of visual discrimination for chiral amines emerged.     

Biomimetic Synthesis of Shaped and Chiral Silica Entities Templated by Organic Objective Materials

Organic molecules with accompanying self‐organization have been a great subject in chemistry, material science and nanotechnology in the past two decades. One of the most important roles of organized organic molecules is the capability of templating complexly structured inorganic materials. The focus of this Minireview is on nanostructured silica with divergent morphologies and/or integrated chirality directed by organic templates of self‐assembled polyamine/polypeptides/block copolymers, chiral organogels, self‐organized chiral amphiphiles and chiral crystalline complexes, etc., by biomimetic silicification and conventional sol–gel reaction. Among them, biosilica (diatoms and sponges)‐inspired biomimetic silicifications are particularly highlighted.     

Reversing the Handedness of Self‐Assembled Porous Molecular Networks through the Number of Identical Chiral Centres

Scanning tunnelling microscope observations at the 1‐phenyloctane/graphite interface reveal how chiral structural information at the molecular level is transferred and expressed structurally at the 2D supramolecular level for a porous system. The chirality of self‐assembled molecular networks formed by chiral dehydrobenzo[12]annulene (cDBA) derivatives having three chiral chains and three achiral chains, alternatingly, is compared with those of cDBAs having six chiral chains reported previously. While for all cDBAs homochiral surfaces are formed, their handedness is not simply a reflection of the absolute configuration of the stereogenic centres. Both the number of stereogenic centres as well as the length of the achiral chains determine the supramolecular handedness, providing a deep insight into the supramolecular chirality induction mechanisms at play. Moreover, these cDBAs act to induce chirality in porous networks formed by achiral DBAs.     

Determination of Enantiomeric Excess in Amine Derivatives with Molecular Self‐Assemblies

We report the first fluorescence‐based assay for the rapid determination of the ee value of amines, amino alcohols, and amino acid esters. The method uses the self‐assembly of 2‐formylphenylboronic acid with a chiral diol and a chiral amine or derivatives (of unknown chirality) to produce two diastereomeric iminoboronates that differ in their fluorescence intensity and polarization. The approach allows for the accurate determination of the ee value of chiral amines with errors of just 1–2 %. We believe that this application of orthogonal dynamic covalent self‐assembly in the determination of the enantioselectivity will lead to the development of high‐throughput procedures for the determination of chirality.     

A Dual‐Functional Metallogel of Amphiphilic Copper(II) Quinolinol: Redox Responsiveness and Enantioselectivity

A dual‐functional metallogel, which was based on the copper(II) complex of quinolinol‐substituted L ‐glutamide, showed both redox‐responsive and enantioselective properties; moreover, the metallogels collapsed into a sol after reduction and could be revived upon subsequent oxidation. The supramolecular chirality and morphology also reversible changed with the gel–sol transition. Furthermore, the metallogels showed new enantioselective recognition towards chiral aromatic amino acids. A new emission band in the blue‐light region at around 393 nm appeared when the metallogels encountered L ‐aromatic amino acids, whereas no new emission band was observed for the corresponding D ‐aromatic amino acids. Such enantioselectivity only occurred in the gel state. No similar phenomenon could be observed in solution. This result suggested that, during the gel formation, the gelator molecules self‐assembled into ordered, chiral supramolecular structures and enhanced the enantiorecognition of the L ‐aromatic amino acids.     

Self‐Assembly of π‐Conjugated Gelators into Emissive Chiral Nanotubes: Emission Enhancement and Chiral Detection

A series of new π‐conjugated gelators that contain various aromatic rings (phenyl, naphthyl, 9‐anthryl) and amphiphilic L ‐glutamide was designed, and their gel formation in organic solvents and self‐assembled nanostructures was investigated. The gelators showed good gelation ability in various organic solvents that ranged from polar to nonpolar. Those gelator molecules with small rings such as phenyl and naphthyl self‐assembled into nanotube structures in most organic solvents and showed strong blue emission. However, the 9‐anthryl derivative formed only a nanofiber structure in any organic solvent, probably owing to the larger steric hindrance. All of these gels showed enhanced fluorescence in organogels. Furthermore, during the gel formation, the chirality at the L ‐glutamide moiety was transferred to the nanostructures, thus leading to the formation of chiral nanotubes. One of the nanotubes showed chiral recognition toward the chiral amines.     

Chiral Perylene Diimides: Building Blocks for Ionic Self‐Assembly

A chiral perylene diimide building block has been prepared based on an amine derivative of the amino acid L ‐phenylalanine. Detailed studies were carried out into the self‐assembly behaviour of the material in solution and the solid state using UV/Vis, circular dichroism (CD) and fluorescence spectroscopy. For the charged building block BTPPP, the molecular chirality of the side chains is translated into the chiral supramolecular structure in the form of right‐handed helical aggregates in aqueous solution. Temperature‐dependent UV/Vis studies of BTPPP in aqueous solution showed that the self‐assembly behaviour of this dye can be well described by an isodesmic model in which aggregation occurs to generate short stacks in a reversible manner. Wide‐angle X‐ray diffraction studies (WXRD) revealed that this material self‐organises into aggregates with π–π stacking distances typical for π‐conjugated materials. TEM investigations revealed the formation of self‐assembled structures of low order and with no expression of chirality evident. Differential scanning calorimetry (DSC) and polarised optical microscopy (POM) were used to investigate the mesophase properties. Optical textures representative of columnar liquid–crystalline phases were observed for solvent‐annealed samples of BTPPP. The high solubility, tunable self‐assembly and chiral ordering of these materials demonstrate their potential as new molecular building blocks for use in the construction of chiro‐optical structures and devices.     

Self‐Assembly through Coordination and π‐Stacking: Controlled Switching of Circularly Polarized Luminescence

Multiple noncovalent interactions can drive self‐assembly through different pathways. Here, by coordination‐assisted changes in π‐stacking modes between chromophores in pyrene‐conjugated histidine (PyHis), a self‐assembly system with reversible and inversed switching of supramolecular chirality, as well as circularly polarized luminescence (CPL) is described. It was found that l ‐PyHis self‐assembled into nanofibers showing P‐chirality and right‐handed CPL. Upon Zn^II coordination, the nanofibers changed into nanospheres with M‐chirality, as well as left‐handed CPL. The process is reversible and the M‐chirality can change to P‐chirality by removing the Zn^II ions. Experimental and theoretical models unequivocally revealed that the cooperation of metal coordination and π‐stacking modes are responsible the reversible switching of supramolecular chirality. This work not only provides insight into how multiple noncovalent interactions regulate self‐assembly pathways.     

DNA‐Decorated,Helically Twisted Nanoribbons: A Scaffold for the Fabrication of One‐Dimensional,Chiral, Plasmonic Nanostructures

Crafting of chiral plasmonic nanostructures is extremely important and challenging. DNA‐directed organization of nanoparticle on a chiral template is the most appealing strategy for this purpose. Herein, we report a supramolecular approach for the design of DNA‐decorated, helically twisted nanoribbons through the amphiphilicity‐driven self‐assembly of a new class of amphiphiles derived from DNA and hexaphenylbenzene (HPB). The ribbons are self‐assembled in a lamellar fashion through the hydrophobic interactions of HPB. The transfer of molecular chirality of ssDNA into the HPB core results in the bias of one of the chiral propeller conformations for HPB and induces a helical twist into the lamellar packing, and leads to the formation of DNA‐wrapped nanoribbons with M‐helicity. The potential of the ribbon to act as a reversible template for the 1D chiral organization of plasmonic nanomaterials through DNA hybridization is demonstrated.     

Mirror Symmetry Breaking by Chirality Synchronisation in Liquids and Liquid Crystals of Achiral Molecules

Spontaneous mirror symmetry breaking is an efficient way to obtain homogeneously chiral agents, pharmaceutical ingredients and materials. It is also in the focus of the discussion around the emergence of uniform chirality in biological systems. Tremendous progress has been made by symmetry breaking during crystallisation from supercooled melts or supersaturates solutions and by self‐assembly on solid surfaces and in other highly ordered structures. However, recent observations of spontaneous mirror symmetry breaking in liquids and liquid crystals indicate that it is not limited to the well‐ordered solid state. Herein, progress in the understanding of a new dynamic mode of symmetry breaking, based on chirality synchronisation of transiently chiral molecules in isotropic liquids and in bicontinuous cubic, columnar, smectic and nematic liquid crystalline phases is discussed. This process leads to spontaneous deracemisation in the liquid state under thermodynamic control, giving rise to long‐term stable symmetry‐broken fluids, even at high temperatures. These fluids form conglomerates that are capable of extraordinary strong chirality amplification, eventually leading to homochirality and providing a new view on the discussion of emergence of uniform chirality in prebiotic systems.     

Self‐Assembly Studies of a Chiral Bisurea‐Based Superhydrogelator

A chiral bisurea‐based superhydrogelator that is capable of forming supramolecular hydrogels at concentrations as low as 0.2 mM is reported. This soft material has been characterized by thermal studies, rheology, X‐ray diffraction analysis, transmission electron microscopy (TEM), and by various spectroscopic techniques (electronic and vibrational circular dichroism and by FTIR and Raman spectroscopy). The expression of chirality on the molecular and supramolecular levels has been studied and a clear amplification of its chirality into the achiral analogue has been observed. Furthermore, thermal analysis showed that the hydrogelation of compound 1 has a high response to temperature, which corresponds to an enthalpy‐driven self‐assembly process. These particular thermal characteristics make these materials easy to handle for soft‐application technologies.