Tunable Circularly Polarized Luminescence via Chirality Induction and Energy Transfer from Organic Films to Semiconductor Nanocrystals

Circularly polarized luminescent (CPL) films with high dissymmetry factors hold great potential for optoelectronic applications. Herein, we propose a strategy for achieving strongly dissymetric CPL in nanocomposite films based on chirality induction and energy transfer to semiconductor nanocrystals. First, focusing on a purely organic system, aggregation-induced emission (AIE) and CPL activity of organic liquid crystals (LCs) forming helical nanofilaments was detected, featuring green emission with high dissymmetry factors g_lum ∼ 10^-2. The handedness of helical filaments, and thus the sign of CPL, was controlled via minute amounts of a small chiral organic dopant. Second, nanocomposite films were fabricated by incorporating InP/ZnS semiconductor quantum dots (QDs) into the LC matrix, which induced the chiral assembly of QDs and endowed them with chiroptical properties. Due to the spectral matching of the components, energy transfer (ET) from LC to QDs was possible enabling a convenient way of tuning CPL wavelengths by varying the LC/QD ratio. As obtained, composite films exhibited absolute g_lum values up to ∼10^-2 and thermally on/off switchable luminescence. Overall, we demonstrate the induction of chiroptical properties by the assembly of nonchiral building QDs on the chiral organic template and energy transfer from organic films to QDs, representing a simple and versatile approach to tune the CPL activity of organic materials.

Hydrophobic Gold Nanoparticles with Intrinsic Chirality for the Efficient Fabrication of Chiral Plasmonic Nanocomposites

The development of plasmonic nanomaterials with chiral geometry has drawn extensive attention owing to their practical implications in chiral catalysis, chiral metamaterials, or enantioselective biosensing and medicine. However, due to the lack of effective synthesis methods of hydrophobic nanoparticles (NPs) showing intrinsic, plasmonic chirality, their applications are currently limited to aqueous systems. In this work, we resolve the problem of achieving hydrophobic Au NPs with intrinsic chirality by efficient phase transfer of water-soluble NPs using low molecular weight, liquid crystal-like ligands. We confirmed that, after the phase transfer, Au NPs preserve strong, far-field circular dichroism (CD) signals, attesting their chiral geometry. The universality of the method is exemplified by using different types of NPs and ligands. We further highlight the potential of the proposed approach to realize chiral plasmonic, inorganic/organic nanocomposites with block copolymers, liquid crystals, and compounds forming physical gels. All soft matter composites sustain plasmonic CD signals with electron microscopies confirming well-dispersed nanoinclusions. The developed methodology allows us to expand the portfolio of plasmonic NPs with intrinsic structural chirality, thereby broadening the scope of their applications toward soft-matter based systems.

Chirality-Induced Spin Selectivity in Heterochiral Short-Peptide-Carbon-Nanotube Hybrid Networks: Role of Supramolecular Chirality

Supramolecular short-peptide assemblies have been widely used for the development of biomaterials with potential biomedical applications. These peptides can self-assemble in a multitude of chiral hierarchical structures triggered by the application of different stimuli, such as changes in temperature, pH, solvent, etc. The self-assembly process is sensitive to the chemical composition of the peptides, being affected by specific amino acid sequence, type, and chirality. The resulting supramolecular chirality of these materials has been explored to modulate protein and cell interactions. Recently, significant attention has been focused on the development of chiral materials with potential spintronic applications, as it has been shown that transport of charge carriers through a chiral environment polarizes the carrier spins. This effect, named chirality-induced spin selectivity or CISS, has been studied in different chiral organic molecules and materials, as well as carbon nanotubes functionalized with chiral molecules. Nevertheless, this effect has been primarily explored in homochiral systems in which the chirality of the medium, and hence the resulting spin polarization, is defined by the chirality of the molecule, with limited options for tunability. Herein, we have developed heterochiral carbon-nanotube-short-peptide materials made by the combination of two different chiral sources: that is, homochiral peptides (l/d) + glucono-δ-lactone. We show that the presence of a small amount of glucono-δ-lactone with fixed chirality can alter the supramolecular chirality of the medium, thereby modulating the sign of the spin signal from "up" to "down" and vice versa. In addition, small amounts of glucono-δ-lactone can even induce nonzero spin polarization in an otherwise achiral and spin-inactive peptide-nanotube composite. Such "chiral doping" strategies could allow the development of complementary CISS-based spintronic devices and circuits on a single material platform.

In Situ Regulation of Microphase Separation-Recognized Circularly Polarized Luminescence via Photoexcitation-Induced Molecular Aggregation

Circularly polarized luminescence (CPL) has attracted great interest owing to its extensive optical information and chiral structural dependence. However, rationally regulating solid-phase CPL signals remains difficult because of the close packing of molecules in solid-state materials and the lack of structural visualization. In this work, we proposed a microphase-separation-recognized CPL regulation strategy via coassembly of a hexathiobenzene-based luminophore and chiral block copolymer (cBCP) with in situ photocontrollability. As a consequence to the continuous increase in the luminophore-to-cBCP ratio, the CPL signal of the supramolecular system exhibited an increasing trend until a critical point. Then, further increasing the ratio stretched the helical pitch of cBCP, which led to CPL reduction. With the photoexcitation-induced molecular aggregation of the luminophore, which was implemented using in situ photoirradiation, the helical pitch was retracted along with the restoration of the CPL signal. These processes were fully recognized and monitored by the microphase-separated nanomorphological change of the coassembled system, which indicated that such a structural contrast could be an effective method for rationally regulating the supramolecular chiropticity of solid-state materials.

Chiral Non-Fullerene Acceptor Enriched Bulk Heterojunctions Enable High-Performance Near-Infrared Circularly Polarized Light Detection

Organic photodetectors that can sensitively convert near-infrared (NIR) circularly polarized light (CPL) into modulable electrical signals have promising applications in spectroscopy, imaging, and communications. However, the preparation of chiral NIR organic photodetectors with simultaneously high dissymmetry factor, responsivity, detectivity, and response speed is challenging. Here, direct CPL detectors based on the bulk heterojunctions (BHJs) of chiral BTP-4Cl non-fullerene acceptor with dilute achiral PM6 donor are constructed, which successfully address these issues. The chiral acceptor-enriched BHJs with a donor/acceptor ratio of 1/10 achieve an optimal trade-off between chiroptical properties and optoelectronic performance. The supramolecular chirality from the acceptor aggregates provides the BHJs with a true absorption dissymmetry factor (g_abs ) of ±0.02 at 830 nm, the highest value among NIR-sensitive detectors, which endows the photodetector with a photocurrent dissymmetry factor (g_sc ) of ±0.03. Impressively, the photodetector demonstrates an external quantum efficiency as high as 60%, a responsivity of 0.4 A W^-1 , a detectivity of 3 × 10¹¹ Jones (based on noise current), and a fast response speed on the microsecond scale with the -3 dB bandwidth over 7000 Hz in the NIR region. This study exhibits a promising strategy for building high-performing direct NIR CPL detectors by introducing supramolecular chirality into BHJs.

Supramolecular Chiral Assembly of Symmetric Molecules with an Extended Conjugated Core

C3-symmetric molecules carrying a conjugated diacetylene (DA) core are found to self-assemble into well-defined supramolecular fibers with enhanced supramolecular chirality in both organic and aqueous solutions. The conjugated core affords these amphiphiles characteristic fluorescence properties, which can be quenched partially due to the aggregation. Integration of the C3-symmetry with the conjugation provides these novel molecules strong aggregation tendency through solvent-mediated π-π stacking with preferential supramolecular chirality, which is predominately related to steric hindrance from their dipeptide pendants. Highly uniform supramolecular fibers of P and M handedness with thickness consistent in the dimensions of individual C3 molecules are obtained. The increase of concentrations induces these fibers to wrap together to form supramolecular fibrous bundles. Topochemical polymerization of the DA moieties can transform these supramolecular fibers into stable covalent polymers. We therefore believe that self-assembly of these C3-symmetric molecules with extended conjugated DA cores provides new prospects for the construction of supramolecular helical fibers through enhanced π-π stacking and creates a convenient strategy to furnish covalent chiral polymers of hierarchical structures through supramolecular assembly.

Eutectogels as Matrices to Manipulate Supramolecular Chirality and Circularly Polarized Luminescence

Solvent is regarded as a factor in tuning the supramolecular chirality of self-assemblies. Deep eutectic solvents (DESs) show diverse properties in contrast to other common solvents, which are emerging in fabricating functional aggregates and nanoarchitectures. Nevertheless, the emergence and manipulation of supramolecular chirality in DES still remain mysterious. Exploring supramolecular chirality in DES would produce tunable chiroptical materials considering their feasible preparation process and abundant hydrogen bonding sites. In this work, we explored the occurrence and manipulation of supramolecular chirality in DES. Transfer from inherent chiral DES to solutes in either aggregated or monomeric building units is blocked. However, the chiral assembly of π-conjugated amino acids was realized. Compared to aqueous media, self-assembly in DES hinders the spontaneous structural and chirality evolution that benefit from efficient solvation, where the π-conjugated amino acids were involved as hydrogen bonding donors. DES performs as a dye-friendly matrix to afford chiroptical eutectogels with tunable circularly polarized luminescence, whereby a large dissymmetry g-factor of up to 0.015 was realized. DES behaves as feasible and flexible solvents to fabricate and stabilize functional soft chiral self-assemblies with controllable chiroptical properties.

Induced and Inversed Circularly Polarized Luminescence of Achiral Thioflavin T Assembled on Peptide Fibril

Chiroptical inversion of amyloid fibrils is a novel phenomenon and is of fundamental importance; however, the underlying structural basis remains poorly understood. Here, the co-assembly of Thioflavin T (ThT) with T1 amyloid fibril and the induced supramolecular chirality is investigated by induced circular dichroism (ICD) and circularly polarized luminescence (CPL), followed by direct morphological helicity observation of the fibril by an atomic force microscope (AFM). ThT exhibits negative ICD and CPL when assembled on the left-handed T1 fibril. Interestingly, when ThT dynamically interacts with the T1 fibril, the left-handed fibril partially converts into right-handed, accompanied with the inversion of CD and CPL signals. These results indicate that the morphological helicity of template fibril cannot be arbitrarily distinguished by the sign of chiroptical spectra of the dye/peptide assemblies.

Wide-Range and Highly Sensitive Chiral Sensing by Discrete 2D Chirality Transfer on Confined Surfaces of Au(I)-Thiolate Nanosheets

Circular dichroism (CD) chiral sensing is very promising to meet the ever-increasing demands for high-throughput chiral analysis in asymmetric synthesis. However, it is still very challenging to sensitively quantify the composition of enantiomers in a wide concentration range because the existing sensing systems show either linear CD response resultant from stoichiometric chiral transfer or nonlinear CD response resultant from amplified chiral transfer and thus have the drawbacks of low sensitivity and narrow quantification range, respectively. Herein, we propose a sensing system of two-dimensional (2D) Au(I)-thiolate nanosheets. The disordered interligand interactions on the confined surfaces of nanosheets enable the formation of discrete amplified chiral domains around the adsorbed chiral analytes, resulting in a linearly amplified chiral transfer behavior, which provides a solution for highly sensitive and wide-range quantification of enantiomer compositions. Taking (1R, 2R)-(-)- and (1S, 2S)-(+)-1,2-diamino cyclohexanes as example analytes, the concentration and full-range enantiomeric excess (ee) values have been quickly determined by adsorbing them on the surface of Au(I)-MPA (MPA: 3-mercaptopropionic acid) nanosheets in the concentration range of 1.0 × 10^-6 to 4.0 × 10^-5 M. By engineering the surface functional groups, Au(I)-thiolate nanosheets can be extended to sense other types of analytes, and several polyols with multiple chiral centers have been sensed by boronic acid functionalized nanosheets at the 10^-7 M level. The high performances, good extendibility, and one-pot high-yield aqueous synthesis ensure these Au(I)-thiolate nanosheets can be developed as a practical and powerful chiral sensing platform.

Solvent-Modulated Chiral Self-Assembly: Selective Formation of Helical Nanotubes, Nanotwists, and Energy Transfer

As the medium for self-assembly processes, solvents strongly influence the supramolecular assemblies via specific solute-solvent interactions, which may result in effective modulation of properties, self-assembled nanostructures, and functions through varying the solvent. Here, two kinds of pyridine-cyanostilbene functionalized chiral amphiphiles (l/d-PyPhG and l-PyG) were designed, and their self-assembly behaviors in different solvents were investigated. It was found that both amphiphiles formed gels in dimethyl sulfoxide (DMSO) and self-assembled into right-handed nanotwists, while they formed suspensions in ethanol consisting of left-handed nanotubes. Although the molecular chirality in the compounds remained unchanged in the two solvents, the nanoassemblies showed opposite handedness at the nanoscale together with opposite circular dichroism (CD) and circularly polarized luminescence (CPL) signals. Furthermore, when the amphiphiles were co-assembled with an achiral dye, it was found that efficient energy transfer took place in the systems composed of nanotubes rather than those composed of nanotwists. Therefore, by assembling molecules with the same molecular chirality in different solvents, a selective formation of helical nanotubes or nanotwists and the regulation of handedness as well as energy transfer efficiency were achieved.

Thermoresponsive Supramolecular Assemblies from Dendronized Amphiphiles To Form Fluorescent Spheres with Tunable Chirality

Balance between self-association of structural units and self-repulsion from crowding-induced steric hindrance accounts for the supramolecular assembly of the amphiphilic entities to form ordered structures, and solvation provides a toolbox to conveniently modulate the assemblies through differential interactions to various structural units. Here we report solvation-modulated supramolecular chiral assembly in aqueous solutions of amphiphilic dendronized tetraphenylethylenes (TPEs) with three-folded dendritic oligoethylene glycols (OEGs) through dipeptide Ala-Gly linkage. These dendronized amphiphiles can form supramolecular spheres with enhanced supramolecular chirality, which is tunable and dependent on solvation. These nanosized spherical aggregates exhibit thermoresponsive behavior, and their cloud point temperatures are dependent on mixed solvent of water and THF. The phase transition temperatures increase with water fractions due to water-driven shifting of OEG moieties from interiors of the aggregates to their peripheries. Furthermore, the thermally induced dehydration and collapse of OEG moieties mediate the reversible aggregation and deaggregation between the spheres, imparting tunable aggregation-induced fluorescent emission (AIE) and supramolecular chirality. Both experimental results and molecular dynamic simulations have highlighted that reversible chirality transformations of the amphiphilic dendronized assemblies mediated by solvation through change solvent quality or thermally dehydration are dependent on the balance between interactions of OEG dendrons with TPE moieties and with the solvent molecules.

Ultraviolet Light Detectable Circularly Polarized Room Temperature Phosphorescence in Chiral Naphthalimide Self-Assemblies

The combination of circularly polarized luminescence (CPL) and pure-organic room temperature phosphorescence (RTP) potentially facilitates the construction of organic chiroptical optoelectronics and display materials, which however are challenging to use in realizing smart control of luminescent colors and switchable chiroptical properties. Here, we show a host-guest strategy to fabricate color-tunable RTP-based circularly polarized phosphorescence. Napthalimides were conjugated directly to chiral segments, of which supramolecular chirality and CPL activities in solid-states could be triggered by substituting bromine atoms on amines. Introducing tetracyanobenzene as an achiral host matrix via simple grinding would allow for the intersystem crossing to trigger red RTP and corresponding CPL by excitation lower than 320 nm, with a large Stokes shift more than 300 nm. The critical excitation wavelength of the RTP switch is determined by the absorbance of tetracyanobenzene. When the excitation wavelength was larger than 320 nm, blue fluorescence dominated with turned off RTP and CPL. The excitation wavelength-dependent RTP and CPL switch allows for detecting ultraviolet (UV) light, showing distinguishable red-blue luminescent color transition, accompanied by on/off RTP. Changing the host matrix from tetracyanobenzene to tricyanobenzene or dicyanobenzene could adjust the critical detecting wavelength limit from 320 to 300 nm. This work establishes a strategy to realize color-tunable, UV light detectable RTP and CPL under smart control.

Engineering Achiral Liquid Crystalline Polymers for Chiral Self-Recovery

Flexible construction of permanently stored supramolecular chirality with stimulus-responsiveness remains a big challenge. Herein, we describe an efficient method to realize the transfer and storage of chirality in intrinsically achiral films of a side-chain polymeric liquid crystal system by combining chiral doping and cross-linking strategy. Even the helical structure was destroyed by UV light irradiation, the memorized chiral information in the covalent network enabled complete self-recovery of the original chiral superstructure. These results allowed the building of a novel chiroptical switch without any additional chiral source in multiple types of liquid crystal polymers, which may be one of the competitive candidates for use in stimulus-responsive chiro-optical devices.

Circularly Polarized Light-Driven Supramolecular Chirality

Introduction of asymmetry into a supramolecular system via external chiral stimuli can contribute to the understanding of the intriguing homochirality found in nature. Circularly polarized light (CPL) is regarded as a chiral physical force with right- or left-handedness. It can induce and modulate supramolecular chirality due to preferential interaction with one enantiomer. Herein, this review focuses on the photon-to-matter chirality transfer mechanisms at the supramolecular level. Thus, asymmetric photochemical reactions are reviewed, and the creation of a chiral bias upon CPL irradiation is discussed. Furthermore, the possible mechanisms for the amplification and propagation of the bias into the supramolecular level are outlined based on the nature of the photochromic building block. Representative examples, including azobenzene derivatives, polydiacetylene, bicyclic ketone, polyfluorenes, C_n -symmetric molecules, and inorganic nanomaterials, are presented.

Scissor-Shaped Photochromic Dyads: Hierarchical Self-Assembly and Photoresponsive Property

Unique relationships between hierarchically organized biological nanostructures and functions have motivated chemists to construct sophisticated artificial nanostructured systems from small and simple synthetic molecules through self-assembly. As one of such sophisticated systems, we have investigated scissor-shaped photochromic dyads that can hierarchically self-assemble into discrete nanostructures showing photoresponsive properties. We synthesized various azobenzene dyads and found that these dyads adopt intramolecularly folded conformation like a closed scissor, and then self-assemble into toroidal nanostructures by generating curvature. The toroids further organize into nanotubes and further into helical supramolecular fibers depending on the nature of alkyl substituents. All of these nanostructures can be dissociated and reorganized through the photoisomerization of azobenzene units. On the other hand, the introduction of stilbene chromophores instead of azobenzenes leads to one-dimensional supramolecular polymerization, which upon the intramolecular photocyclization of stilbene chromophores shifts to curved self-assembly leading to helicoidal fibers with distinct supramolecular chirality.

Quorum Sensing Pseudomonas Quinolone Signal Forms Chiral Supramolecular Assemblies With the Host Defense Peptide LL-37

Host defense antimicrobial peptides (HDPs) constitute an integral component of the innate immune system having nonspecific activity against a broad spectrum of microorganisms. They also have diverse biological functions in wound healing, angiogenesis, and immunomodulation, where it has also been demonstrated that they have a high affinity to interact with human lipid signaling molecules. Within bacterial biofilms, quorum sensing (QS), the vital bacterial cell-to-cell communication system, is maintained by similar diffusible small molecules which control phenotypic traits, virulence factors, biofilm formation, and dispersion. Efficient eradication of bacterial biofilms is of particular importance as these colonies greatly help individual cells to tolerate antibiotics and develop antimicrobial resistance. Regarding the antibacterial function, for several HDPs, including the human cathelicidin LL-37, affinity to eradicate biofilms can exceed their activity to kill individual bacteria. However, related underlying molecular mechanisms have not been explored yet. Here, we employed circular dichroism (CD) and UV/VIS spectroscopic analysis, which revealed that LL-37 exhibits QS signal affinity. This archetypal representative of HDPs interacts with the Pseudomonas quinolone signal (PQS) molecules, producing co-assemblies with peculiar optical activity. The binding of PQS onto the asymmetric peptide chains results in chiral supramolecular architectures consisting of helically disposed, J-aggregated molecules. Besides the well-known bacterial membrane disruption activity, our data propose a novel action mechanism of LL-37. As a specific case of the so-called quorum quenching, QS signal molecules captured by the peptide are sequestered inside co-assemblies, which may interfere with the microbial QS network helping to prevent and eradicate bacterial infections.

The Importance of Spin State in Chiral Supramolecular Electronics

The field of spintronics explores how magnetic fields can influence the properties of organic and inorganic materials by controlling their electron’s spins. In this sense, organic materials are very attractive since they have small spin-orbit coupling, allowing long-range spin-coherence over times and distances longer than in conventional metals or semiconductors. Usually, the small spin-orbit coupling means that organic materials cannot be used for spin injection, requiring ferromagnetic electrodes. However, chiral molecules have been demonstrated to behave as spin filters upon light illumination in the phenomenon described as chirality-induced spin selectivity (CISS) effect. This means that electrons of certain spin can go through chiral assemblies of molecules preferentially in one direction depending on their handedness. This is possible because the lack of inversion symmetry in chiral molecules couples with the electron’s spin and its linear momentum so the molecules transmit the one preferred spin. In this respect, chiral semiconductors have great potential in the field of organic electronics since when charge carriers are created, a preferred spin could be transmitted through a determined handedness structure. The exploration of the CISS effect in chiral supramolecular semiconductors could add greatly to the efforts made by the organic electronics community since charge recombination could be diminished and charge transport improved when the spins are preferentially guided in one specific direction. This review outlines the advances in supramolecular chiral semiconductors regarding their spin state and its influence on the final electronic properties.

Transfer, Amplification, Storage, and Complete Self-Recovery of Supramolecular Chirality in an Achiral Polymer System

Supramolecular chirality and its complete self-recovery ability are highly mystical in nature and biological systems, which remains a major challenge today. Herein, we demonstrate that partially cross-linked azobenzene (Azo) units can be employed as the potential chiral trigger to fully heal the destroyed helical superstructure in achiral nematic polymer system. Combining the self-assembly of Azo units and terminal hydroxyl groups in polymer side chains allows the vapor-induced chiral nematic phase and covalent fixation of the superstructure via acetal reaction. The induced helical structure of Azo units can be stored by inter-chain cross-linking, even after removal of the chiral source. Most interestingly, the stored chiral information can trigger perfect chiral self-recovery (CSR) behavior after being destroyed by UV light, heat, and solvents. The results pave a new way for producing novel chiroptical materials with reversible chirality from achiral sources.

Supramolecular Interactions and Morphology of Self-Assembling Peptide Amphiphile Nanostructures

The morphology of supramolecular peptide nanostructures is difficult to predict given their complex energy landscapes. We investigated peptide amphiphiles containing β-sheet forming domains that form twisted nanoribbons in water. We explained the morphology based on a balance between the energetically favorable packing of molecules in the center of the nanostructures, the unfavorable packing at the edges, and the deformations due to packing of twisted β-sheets. We find that morphological polydispersity of PA nanostructures is determined by peptide sequences, and the twisting of their internal β-sheets. We also observed a change in the supramolecular chirality of the nanostructures as the peptide sequence was modified, although only amino acids with l-configuration were used. Upon increasing charge repulsion between molecules, we observed a change in morphology to long cylinders and then rodlike fragments and spherical micelles. Understanding the self-assembly mechanisms of peptide amphiphiles into nanostructures should be useful to optimize their well-known functions.

Induction of Λ-helicity in a zinc complex with an alanine-appended aminopyridine ligand

The crystal structure of tris[dimethyl 5-({1-[(pyridin-2-yl-κN)carbamoyl-κO]ethyl}carbamoyl)benzene-1,3-dicarboxylate]zinc(II) dinitrate acetonitrile trisolvate, [Zn(C₁₉H₁₉N₃O₆)₃](NO₃)₂·3CH₃CN or [Zn(L)₃](NO₃)₂·3CH₃CN, (1), has been determined by single-crystal X-ray diffraction. The neutral ligand L coordinates to the Zn²⁺ cation in a bidentate fashion via the pyridine N atom and an amide O atom, forming a six-membered chelate ring. The Λ-helical chirality of the Zn²⁺ coordination sphere is induced by pendant L-alanine residues through stacking interactions between the arene groups of two coordinated ligands, assisted by a hydrogen bond between amide groups bonded to the stacked arene rings. The third ligand is coordinated to the Zn²⁺ cation by the same six-membered chelate ring, but in the opposite direction with respect to the analogous chelate rings of the first two coordinated ligands. Besides ionic interactions between [ZnL₃]²⁺ complexes and NO₃^- anions, several types of hydrogen bonds and intermolecular stacking interactions contribute to the stability of the solid-state phase.

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.

Unexpected Role of Achiral Glycine in Determining the Suprastructural Handedness of Peptide Nanofibrils

Helical supramolecular architectures play important structural and functional roles in biological systems. Although their occurrence is widely perceived to correlate to fundamental chiral units including l-amino acids and d-sugars, the detailed relationship between molecular and supramolecular handedness is still unclear. At the same time, although achiral units are practically always in close proximity to chiral ones by covalent linkage along a polymeric chain, their effect on supramolecular handedness has received relatively less attention. Here, we designed a set of short amphiphilic peptides, in which an achiral glycine residue was incorporated at the interface between the hydrophobic and hydrophilic segments. We observed that glycine incorporation caused dramatic variations in suprastructural handedness in self-assembled peptide nanofibrils, and the effect of the hydrophilic charged residue at the C-terminus on supramolecular handedness was demolished, leading to chiral truncation. Furthermore, molecular dynamics simulations and quantum chemistry calculations revealed that the unanticipated role of the glycine residue in regulating supramolecular handedness originated from its effect on the conformational preference of single β-strands. Importantly, reduced density gradient analyses on single β-strands indicated that, due to the lack of a side chain in glycine, intricate noncovalent interactions were produced among the neighboring amino acid side chains of the incorporated glycine and its local backbone, resulting in diverse β-strand conformations.

Polarization Dependent Photoinduced Supramolecular Chirality in High-Performance Azo Materials

Here, we will show photo-induced supramolecular chirality in thin films of achiral amorphous polymers with azo groups in their side-chain. A matter of particular interest is the effect of various film thicknesses on azimuthal rotation and ellipticity of incident/transmitted polarized light. Furthermore, we investigated the temporal stability of inscribed chirality. By polarimetric measurements, we found out that the azimuthal rotation gets higher with layer thickness. In this scope, we were able to measure a very high azimuthal rotation of Δψ/d=112.5∘/μm. The inscribed chirality was stable for several days. Furthermore, we investigated the time-resolved behavior of incident and transmitted polarization ellipticities for various thicknesses. The time dependency may be explained by a two-step process: (1) fast trans-cis-isomerization resulting in photo-orientation and (2) slow photo-induced mass flow.

Bay-Substitution Effect of Perylene Diimides on Supramolecular Chirality and Optoelectronic Properties of Their Self-Assembled Nanostructures

One-dimensional (1D) organic chiral supramolecules have received a great deal of attention for their promising applications in chiral recognition systems, chemical sensors, catalysts, and optoelectronics. Compared to modifications at the imide position of a perylene diimide (PDI), few studies have explored bay substitution of chiral PDIs and their self-assemblies into 1D nanomaterials. Herein, we describe the synthesis of three bay-substituted PDIs and explore the effects of bay substitution on supramolecular chirality by examining circular dichroism spectra and the optoelectronic performance of chiral PDI nanomaterials in phototransistors. Among the three fabricated self-assemblies, nanomaterials based on (R)-CN-CPDI-Ph exhibited the highest electron mobility of 0.17 cm² V^-1 s^-1, a low threshold voltage of -1 V, and enhanced optoelectronic performance. For example, the photoresponsivity and external quantum efficiency of (R)-CN-CPDI-Ph assemblies were 4-fold higher than those of (R)-2Br-CPDI-Ph and (R)-2F-CPDI-Ph. All three nanomaterials exhibited fast switching speeds compared with previously reported N-substituted PDIs, suggesting that bay substitution can be an effective means of achieving rapid photoswitching. A comprehensive study using density functional theory calculations and crystal analyses revealed that the enhanced optoelectronic performance of (R)-CN-CPDI-Ph nanomaterials is related to the substitution of CN at the bay position of PDI. This minor change provides simultaneous improvements in electron injectability and structural order. Our findings demonstrate that bay substitution can significantly impact the self-assembly, supramolecular chirality, and optoelectronic properties of PDI nanomaterials.

Dissecting the Role of the Sergeants in Supramolecular Helical Catalysts: From Chain Capping to Intercalation

Controlling the properties of supramolecular assemblies requires unveiling the specific interactions between their components. In the present work, the catalytic properties and structure of co-assemblies composed of a benzene-1,3,5-tricarboxamide (BTA) ligand coordinated to copper (the soldier) and seven enantiopure BTAs (the sergeants) have been determined. Whatever the sergeant, the enantioselectivity of the reaction is directly proportional to the optical purity of the supramolecular helices. More strikingly, the role played by the sergeant in the co-assembly process differs significantly: from almost pure intercalator (when it is incorporated in the stacks of the soldier and generates long homochiral helices) to pure chain capper (when it leads to the formation of partly helically biased and short assemblies). The former situation leads to optimal enantioselectivity for the catalytic system under study (58 % ee) while the latter situation leads to very low selectivity (8 % ee). The successful rationalization of this high and unexpected difference is crucial for the development of more efficient catalysts and more elaborate supramolecular systems.