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

Handedness-Inverted and Stimuli-Responsive Circularly Polarized Luminescent Nano/Micromaterials Through Pathway-Dependent Chiral Supramolecular Polymorphism

The precise manipulation of supramolecular polymorphs has been widely applied to control the morphologies and functions of self-assemblies, but is rarely utilized for the fabrication of circularly polarized luminescence (CPL) materials with tailored properties. Here, this work reports that an amphiphilic naphthalene-histidine compound (NIHis) readily self-assembled into distinct chiral nanostructures through pathway-dependent supramolecular polymorphism, which shows opposite and multistimuli responsive CPL signals. Specifically, NIHis display assembly-induced CPL from the polymorphic keto tautomer, which become predominant during enol-keto tautomerization shifting controlled by a bulk solvent effect. Interestingly, chiral polymorphs of nanofiber and microbelt with inverted CPL signals can be prepared from the same NIHis monomer in exactly the same solvent compositions and concentrations by only changing the temperature. The tunable CPL performance of the solid microbelts is realized under multi external physical or chemical stimuli including grinding, acid fuming, and heating. In particular, an emission color and CPL on-off switch based on the microbelt polymorph by reversible heating-cooling protocol is developed. This work brings a new approach for developing smart CPL materials via supramolecular polymorphism engineering.

Thioxanthone Functionalized NanoTiO2 Composites as Photocatalyst for Degradation of Organic Dyes

Titanium dioxide (TiO2) photocatalytic technology has the advantages of high catalytic activity, high chemical stability, nontoxicity, and low cost. Therefore, it finds widespread applications in the degradation of organic pollutants in water, antibacterial, environmental purification, and other fields. In this study, we have obtained a photocatalyst by modifying nanoTiO2 with the photosensitizer thioxanthone. The light-harvesting units of thioxanthone and nanoTiO2 can work synergistically to capture light energy. As a heterogeneous photocatalytic material, it can efficiently degrade organic dyes such as Rhodamine B, methyl blue and methyl orange. Specifically, the degradation rate of 0.1 mmol/L Rhodamine B can reach 97% after 35 min of irradiation, and methyl blue and methyl orange can also reach 98 and 56%, respectively.

Multiple Chirality Switching of a Dye-Grafted Helical Polymer Film Driven by Acid & Base

A stimuli-responsive multiple chirality switching material, which can regulate opposed chiral absorption characteristics, has great application value in the fields of optical modulation, information storage and encryption, etc. However, due to the rareness of effective functional systems and the complexity of material structures, developing this type of material remains an insurmountable challenge. Herein, a smart polymer film with multiple chirality inversion properties was fabricated efficiently based on a newly-designed acid & base-sensitive dye-grafted helical polymer. Benefited from the cooperative effects of various weak interactions (hydrogen bonds, electrostatic interaction, etc.) under the aggregated state, this polymer film exhibited a promising acid & base-driven multiple chirality inversion property containing record switchable chiral states (up to five while the solution showed three-state switching) and good reversibility. The creative exploration of such a multiple chirality switching material can not only promote the application progress of current chiroptical regulation technology, but also provide a significant guidance for the design and synthesis of future smart chiroptical switching materials and devices.

Modulating Helix-Preference of an Axially-Twisted Molecular Scaffold Through Diastereomeric Salt Formation with Tartaric Acid Stereoisomers

Herein, we designed a chiral, axially-twisted molecular scaffold (ATMS) using pyridine-2,6-dicarboxamide (PDC) unit as pivot, chiral trans-cyclohexanediamine (CHDA) residues as linkers, and pyrene residues as fluorescent reporters. R,R-ATMS exclusively adopted M-helicity and produced differential response in UV-vis, fluorescence, and NMR upon addition of tartaric acid (TA) stereoisomers allowing naked-eye detection and enantiomeric content determination. Circular dichroism (CD) profile of R,R-ATMS underwent unique changes during titration with TA stereoisomers - while loss of CD signal at 345 nm was observed with equimolar D-TA and meso-TA, inversion was seen with equimolar L-TA. Temperature increase weakened these interactions to partially recover the original CD signature of R,R-ATMS. 2D NMR studies also indicated the significant structural changes in R,R-ATMS in the solution state upon addition of L-TA. Single crystal X-ray diffraction (SCXRD) studies on the crystals of the R,R-ATMS⊃D-TA salt revealed the interacting partners stacked in arrays and ATMS molecules stabilized by π-π stacking between its PDC and pyrene residues. Contrastingly, tightly-packed supramolecular cages comprised of four molecules each of R,R-ATMS and L-TA were seen in R,R-ATMS⊃L-TA salt, and the ATMS molecules contorted to achieve CH-π interactions between its pyrene residues. These results may have implications in modulating the helicity of topologically-similar larger biomolecules.

Copper-Induced Supramolecular Peptide Assemblies for Multi-Pathway Cell Death and Tumor Inhibition

Although self-assembly has emerged as an effective tool for fabricating biomaterials, achieving precise control over the morphologies and functionalities of the resultant assemblies remains an ongoing challenge. Inspired by the copper peptide naturally present in human plasma, in this study, we designed a synthetic precursor, FcGH. FcGH can self-assemble via two distinct pathways: spontaneous and Cu2+-induced. These two assembly pathways enabled the formation of assemblies with tunable morphologies by adjusting the amount of added Cu2+. We found that the nanoparticles formed by Cu2+-induced self-assembly exhibited a significantly higher cellular uptake efficiency than the wormlike fibers formed spontaneously. Moreover, this Cu2+-induced assembly process occurred spontaneously at a 1 : 1 molar ratio of Cu2+ to FcGH, avoiding the excessive use of Cu2+ and a tedious preparation procedure. By co-assembling with 10-hydroxycamptothecin (HCPT)-conjugated FcGH, Cu2+-induced supramolecular nanodrugs elicited multiple cell death modalities in cancer cells with elevated immunogenicity, enhancing the therapeutic effect compared to free HCPT. This study highlights Cu2+-induced self-assembly as an efficient tool for directing the assembly of nanodrugs and for synergistic tumor therapy.

Ligand Chirality Transfer from Solution State to the Crystalline Self-Assemblies in Circularly Polarized Luminescence (CPL) Active Lanthanide Systems

The synthesis of a family of chiral and enantiomerically pure pyridyl-diamide (pda) ligands that upon complexation with europium [Eu(CF3SO3)3] result in chiral complexes with metal centered luminescence is reported; the sets of enantiomers giving rise to both circular dichroism (CD) and circularly polarized luminescence (CPL) signatures. The solid-state structures of these chiral metallosupramolecular systems are determined using X-ray diffraction showing that the ligand chirality is transferred from solution to the solid state. This optically favorable helical packing arrangement is confirmed by recording the CPL spectra from the crystalline assembly by using steady state and enantioselective differential chiral contrast (EDCC) CPL Laser Scanning Confocal Microscopy (CPL-LSCM) where the two enantiomers can be clearly distinguished.

Rapid room-temperature phosphorescence chiral recognition of natural amino acids

Chiral recognition of amino acids is very important in both chemical and life sciences. Although chiral recognition with luminescence has many advantages such as being inexpensive, it is usually slow and lacks generality as the recognition module relies on structural complementarity. Here, we show that one single molecular-solid sensor, L-phenylalanine derived benzamide, can manifest the structural difference between the natural, left-handed amino acid and its right-handed counterpart via the difference of room-temperature phosphorescence (RTP) irrespective of the specific chemical structure. To realize rapid and reliable sensing, the doped samples are obtained as nanocrystals from evaporation of the tetrahydrofuran solutions, which allows for efficient triplet-triplet energy transfer to the chiral analytes generated in situ from chiral amino acids. The results show that L-analytes induce strong RTP, whereas the unnatural D-analytes produce barely any afterglow. The method expands the scope of luminescence chiral sensing by lessening the requirement for specific molecular structures.

Dynamic Chemistry Toolbox for Advanced Sustainable Materials

Developing dynamic chemistry for polymeric materials offers chemical solutions to solve key problems associated with current plastics. Mechanical performance and dynamic function are equally important in material design because the former determines the application scope and the latter enables chemical recycling and hence sustainability. However, it is a long-term challenge to balance the subtle trade-off between mechanical robustness and dynamic properties in a single material. The rise of dynamic chemistry, including supramolecular and dynamic covalent chemistry, provides many opportunities and versatile molecular tools for designing constitutionally dynamic materials that can adapt, repair, and recycle. Facing the growing social need for developing advanced sustainable materials without compromising properties, recent progress showing how the toolbox of dynamic chemistry can be explored to enable high-performance sustainable materials by molecular engineering strategies is discussed here. The state of the art and recent milestones are summarized and discussed, followed by an outlook toward future opportunities and challenges present in this field.

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.

Reversible chirality inversion of an AuAgx-cysteine coordination polymer by pH change

Responsive chiral systems have attracted considerable attention, given their potential for diverse applications in biology, optoelectronics, photonics, and related fields. Here we show the reversible chirality inversion of an AuAgx-cysteine (AuAgx-cys) coordination polymer (CP) by pH changes. The polymer can be obtained by mixing HAuCl4 and AgNO3 with L-cysteine (or D-cysteine) in appropriate proportions in H2O (or other surfactant solutions). Circular dichroism (CD) spectrum is used to record the strong optical activity of the AuAg0.06-L-cys enantiomer (denoted as L0.06), which can be switched to that of the corresponding D0.06 enantiomer by alkalization (final dispersion pH > 13) and can be switched back after neutralization (final dispersion pH <8). Multiple structural changes at different pH values (≈9.6, ≈13) are observed through UV-Vis and CD spectral measurements, as well as other controlled experiments. Exploration of the CP synthesis kinetics suggests that the covalent bond formation is rapid and then the conformation of the CP materials would continuously evolve. The reaction stoichiometry investigation shows that the formation of CP materials with chirality inversion behavior requires the balancing between different coordination and polymerization processes. This study provides insights into the potential of inorganic stereochemistry in developing promising functional materials.

Photocontrolled chiroptical switch based on the self-assembly of azobenzene-bridged bis-tryptophan enantiomers

Chirality dynamic tuning plays fundamental roles in chemistry, material science and biological system. Herein, a pair of azobenzene-bridged bis-tryptophan enantiomers (Azo-di-d/l-Trp) were designed and synthesized via simple reactions. With the fuel of glucono-δ-lactone (GdL), releasing protons during its hydrolysis, the alkaline solution of Azo-di-d/l-Trp gradually self-assembled into contrast chiral helical structures and displayed magnitude and mirror image of circular dichroism (CD) signals. While the chiral helices converted to CD silent nanoparticles when the azobenzene moiety isomerized from trans- to cis-form under UV irradiation. More importantly, this chiroptical switch, displaying reversible interconversion between chiral amplification and silent, can be smartly controlled via photoirradiation at various wavelengths.

Solvent-induced structural transformation in a one-dimensional coordination polymer

We have rationally designed a one-dimensional coordination polymer (1D CP), termed 1D-DGIST-18, that exhibits intrinsic structural flexibility. This 1D CP enables its expansion into a three-dimensional network through supramolecular interactions involving coordinated solvents and/or ligands. The strategic selection of solvents for solvent exchange, prior to drying, significantly influences the structures of 1D-DGIST-18 by removing certain coordinating solvents and modulating π-π stacking. Consequently, a hierarchical porosity emerges, ranging from micro- to meso- to macroporous structures, which is attributed to its inherent structural dynamics. Additionally, the formation of excimers endows 1D-DGIST-18, when immersed in acetone, with 'turn-on' fluorescence, as evidenced by fluorescence decay profiles. These structural transitions within 1D-DGIST-18 are further elucidated using single-crystal X-ray diffractometry. The insights from this study provide a foundation for the design of materials with structural dynamics and tunable properties.

Structurally Diverse Pyrene-decorated Planar Chiral [2,2]Paracyclophanes with Tunable Circularly Polarized Luminescence between Monomer and Excimer

We reported the synthesis of a series of structurally diverse CPL-active molecules, in which pyrene units were installed to chiral pm/po-[2,2]PCP scaffolds either with or without a triple bond spacer for pm/po-PCP-P1 and pm/po-PCP-P2, respectively. The X-ray crystallographic analyses revealed that these pyrene-based [2,2]PCP derivatives exhibited diverse structures and crystal packings in the solid phases. The pyrene-based [2,2]PCP derivatives exhibit various (chir)optical properties in organic solutions, depending on their respective structures. In a mixture of dioxane and water, pm/po-PCP-P1 emit green excimer fluorescence, whereas pm/po-PCP-P2 emit blue one. The chiroptical investigation demonstrated that Rp-pm-PCP-P1 and Rp-pm-PCP-P2 exhibited completely opposite CD and CPL signals even they possess the same chiral Rp-[2,2]PCP core. The same argument also holds for other chiral pyrene-based [2,2]PCP derivatives. The theoretical calculation revealed that these unusual phenomena were attributed to different orientation between transition electric dipole moments and the magnetic dipole moments originating from the presence or absence of a triple bond spacer. These pyrene-based [2,2]PCP derivatives display various colours and fluorescence emissions in the solid state and PMMA films, possibly due to the different packings as observed in the crystal structure. Moreover, these compounds also can interact with perylene diimide through π-π interactions, leading to near-white fluorescence.

Full-Color Circularly Polarized Luminescence of Supramolecular Polymers with Handedness Inversion Regulated by Anion and Temperature

Constructing full-color circularly polarized luminescence (CPL) materials with switchable handedness in the solid state is an appealing yet considerably challenging task, especially for supramolecular polymer films assembled from homochiral monomers. Herein, supramolecular polymers with full-color CPL and inverted handedness are realized through the coassembly of a homochiral cholesterol derivative (PVPCC), metal ions (Zn2+), and achiral fluorescent dyes. The obtained coassembled systems show anion-directed supramolecular chirality inversion by exchanging the anions of NO3-, ClO4-, BF4-, and Cl-. For instance, the negative CD and right-handed CPL are detected in the PVPCC/Zn(NO3)2 aggregates, which convert into positive CD and left-handed CPL after introducing Cl-, corresponding to the transformation from nanorods to nanofibers. Furthermore, the tunable CPL color and handedness inversion of the coassembly system of PVPCC/Zn(NO3)2 and achiral fluorescent dyes can be established by alternately changing the assembling temperature of 298 and 273 K. Importantly, the full-color CPL polymeric materials are then constructed by doping the PVPCC/Zn(NO3)2/dyes complexes into poly(methyl methacrylate) (PMMA) film, which maintains the handedness inversion and shows the enhanced CPL performance. The work not only deepens the understanding of chirality inversion in supramolecular chemistry but also helps to construct full-color CPL materials with switchable handedness from homochiral building blocks in materials science.

Biomimetic chiral hydrogen-bonded organic-inorganic frameworks

Assembly ubiquitously occurs in nature and gives birth to numerous functional biomaterials and sophisticated organisms. In this work, chiral hydrogen-bonded organic-inorganic frameworks (HOIFs) are synthesized via biomimicking the self-assembly process from amino acids to proteins. Enjoying the homohelical configurations analogous to α-helix, the HOIFs exhibit remarkable chiroptical activity including the chiral fluorescence (glum = 1.7 × 10-3) that is untouched among the previously reported hydrogen-bonded frameworks. Benefitting from the dynamic feature of hydrogen bonding, HOIFs enable enantio-discrimination of chiral aliphatic substrates with imperceivable steric discrepancy based on fluorescent change. Moreover, the disassembled HOIFs after recognition applications are capable of being facilely regenerated and self-purified via aprotic solvent-induced reassembly, leading to at least three consecutive cycles without losing the enantioselectivity. The underlying mechanism of chirality bias is decoded by the experimental isothermal titration calorimetry together with theoretic simulation.

Supramolecular Nanostructures for the Delivery of Peptides in Cancer Therapy

Supramolecular nanostructured based delivery systems are emerging as a meaningful approach in the treatment of cancer, offering controlled drug release and improved therapeutic efficacy. The self-assembled structures can be small molecules, polymers, peptides, or proteins, which can be used and functionalized to achieve tailored release and target specific cells, tissues, or organs. These structures can improve the solubility and stability of drugs having low aqueous solubility by encapsulating and protecting them from degradation. Alongside, peptides as natural biomolecules have gained increasing attention as potential candidates in cancer treatment because of their biocompatibility, low cytotoxicity, and high specificity toward tumor cells. The amino acid sequences in peptide molecules are tunable, efficiently controlling the morphology of peptide-based self-assembled nanosystems and offering flexibility to form supramolecular nanostructures (SNs). It is evident from the current literature that the supramolecular nanostructures based delivery of peptide for cancer treatment hold great promise for future cancer therapy, offering potential strategies for personalized medicine with improved patient outcomes. SIGNIFICANCE STATEMENT: This review focuses on fundamentals and various drug delivery mechanisms based on SNs. Different SN approaches and recent literature reviews on peptide delivery are also presented to the readers.

Unraveling Dynamic Helicity Inversion and Chirality Transfer through the Synthesis of Discrete Azobenzene Oligomers by an Iterative Exponential Growth Strategy

Unraveling the chirality transfer mechanism of polymer assemblies and controlling their handedness is beneficial for exploring the origin of hierarchical chirality and developing smart materials with desired chiroptical activities. However, polydisperse polymers often lead to an ambiguous or statistical evaluation of the structure-property relationship, and it remains unclear how the iterative number of repeating units function in the helicity inversion of polymer assemblies. Herein, we report the macroscopic helicity and dynamic manipulation of the chiroptical activity of supramolecular assemblies from discrete azobenzene-containing oligomers (azooligomers), together with the helicity inversion and morphological transition achieved solely by changing the iterative chain lengths. The corresponding assemblies also differ from their polydisperse counterparts in terms of thermodynamic properties, chiroptical activities, and morphological control.

Peptide-Based Optical/Electronic Materials: Assembly and Recent Applications in Biomedicine, Sensing, and Energy Storage

The unique optical and electronic properties of living systems are impressive. Peptide-based supramolecular self-assembly systems attempt to mimic these properties by preparation optical/electronic function materials with specific structure through simple building blocks, rational molecular design, and specific kinetic stimulation. From the perspective of building blocks and assembly strategies, the unique optical and electronic properties of peptide-based nanostructures, including peptides self-assembly and peptides regulate the assembly of external function subunits, are systematically reviewed. Additionally, their applications in biomedicine, sensing, and energy storage are also highlighted. This bioinspired peptide-based function material is one of the hot candidates for the new generation of green intellect materials, with many advantages such as biocompatibility, environmental friendliness, and adjustable morphology.

Enhancing Circularly Polarized Luminescence in Quantum Dots through Chiral Coordination-Mediated Growth at the Liquid/Liquid Interface

Here, we develop a novel methodology for synthesizing chiral CdSe@ZnS quantum dots (QDs) with enhanced circularly polarized luminescence (CPL) by incorporating l-/d-histidine (l-/d-His) ligands during ZnS shell growth at the water/oil interface. The resulting chiral QDs exhibit exceptional absolute photoluminescence quantum yield of up to 67.2%, surpassing the reported limits of 40.0% for chiral inorganic QDs, along with absorption dissymmetry factor (|gabs|) and luminescence dissymmetry factor (|glum|) values of 10-2, exceeding the range of 10-5-10-3 and 10-4-10-2, respectively. Detailed investigations of the synthetic pathway reveal that the interface, as a binary synthetic environment, facilitates the coordinated ligand exchange and shell growth mediated by chiral His-Zn2+ coordination complexes, leading to a maximum fluorescent brightness and chiroptical activities. The growth process, regulated by the His-Zn2+ coordination complex, not only reduces trap states on the CdSe surface, thereby enhancing the fluorescence intensity, but also significantly promotes the orbital hybridization between QDs and chiral ligands, effectively overcoming the shielding effect of the wide bandgap shell and imparting pronounced chirality. The proposed growth pathway elucidates the origin of chirality and provides insights into the regulation of the CPL intensity in chiral QDs. Furthermore, the application of CPL QDs in multilevel anticounterfeiting systems overcomes the limitations of replication in achiral fluorescence materials and enhances the system's resistance to counterfeiting, thus opening new opportunities for chiral QDs in optical anticounterfeiting and intelligent information encryption.

Advance Progress in Assembly Mechanisms of Carrier-Free Nanodrugs for Cancer Treatment

Nanocarriers have been widely studied and applied in the field of cancer treatment. However, conventional nanocarriers still suffer from complicated preparation processes, low drug loading, and potential toxicity of carriers themselves. To tackle the hindrance, carrier-free nanodrugs with biological activity have received increasing attention in cancer therapy. Extensive efforts have been made to exploit new self-assembly methods and mechanisms to expand the scope of carrier-free nanodrugs with enhanced therapeutic performance. In this review, we summarize the advanced progress and applications of carrier-free nanodrugs based on different types of assembly mechanisms and strategies, which involved noncovalent interactions, a combination of covalent bonds and noncovalent interactions, and metal ions-coordinated self-assembly. These carrier-free nanodrugs are introduced in detail according to their assembly and antitumor applications. Finally, the prospects and existing challenges of carrier-free nanodrugs in future development and clinical application are discussed. We hope that this comprehensive review will provide new insights into the rational design of more effective carrier-free nanodrug systems and advancing clinical cancer and other diseases (e.g., bacterial infections) infection treatment.

Recent Progress of Preparation Strategies in Organic Nanoparticles for Cancer Phototherapeutics

Phototherapy has the advantages of being a highly targeted, less toxic, less invasive, and repeatable treatment, compared with conventional treatment methods such as surgery, chemotherapy, and radiotherapy. The preparation strategies are significant in order to determine the physical and chemical properties of nanoparticles. However, choosing appropriate preparation strategies to meet applications is still challenging. This review summarizes the recent progress of preparation strategies in organic nanoparticles, mainly focusing on the principles, methods, and advantages of nanopreparation strategies. In addition, typical examples of cancer phototherapeutics are introduced in detail to inform the choice of appropriate preparation strategies. The relative future trend and outlook are preliminarily proposed.

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

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

Stepwise Solution-Interfacial Nanoarchitectonics for Assembled Film with Full-Color and White-Light Circularly Polarized Luminescence

The fabrication of chiral thin films with tunable circularly polarized luminescence (CPL) colors is important in developing chiroptical materials but remains challenging due to the lack of assembly-initiated chiral film formation methodology. Here, by adopting a combined solution aggregation and interfacial assembly strategy, we report the fabrication of chiral film materials with full-color and white-light CPL. A biquinoline glutamic acid ester (abbreviated as BQGE) shows a typical aggregation-induced emission property with blue CPL after solution aggregation. Subsequent interfacial assembly of these solution aggregates on a solid substrate leads to the formation of a CPL active film consisting of nanobelt structures. Since the BQGE molecule has a coordination site, the CPL emission of an individual BQGE film can be extended from blue to green emission upon coordination with a zinc ion, accompanied by morphology transition from nanobelts to nanofibers. Further extension to red-color CPL is successfully achieved by coassembly with an achiral acceptor dye. Interestingly, the proper combination of coordination ratio and acceptor loading ratio provides bright white-light CPL emission from the BQGE/Zn²⁺/PDA triad composite film. This work provides a new approach to fabricating chiroptical film materials with controlled microscopic morphology and tunable CPL properties.

Self-Assembled Charge-Transfer Chiral π-Materials: Stimuli-Responsive Circularly Polarized Luminescence and Chiroptical Photothermic Effects

Despite significant achievements in the field of chiroptical organic materials, the full utilization of both the excited state and ground state chiroptical properties in a single supramolecular system is still rarely disclosed. Here, we report that the rational combination of the charge-transfer (CT) interaction with the spacer effect and controlled protonation of π-histidine leads to chiroptical organic π-materials with both circularly polarized luminescence (CPL) and the supramolecular chirality-directed chiroptical photothermic effect. Three pyrene-conjugated histidine derivatives with varied acyl linkers (PyHis, PyC1His, and PyC3His) were designed to coassemble with electron-deficient 1,2,4,5-tetracyanobenzene (TCNB), leading to the formation of supramolecular CT complexes with intense orange to red CPL depending on the linker length. The linker length also affected the protonation-induced CPL responsiveness of the corresponding CT assemblies. Upon protonation of the histidine moiety, PyC3His/TCNB CT assemblies exhibited an inverted CPL signal, while PyHis/TCNB pairs gave quenched CPL due to the disassembly. The protonation-controlled PyC3His/TCNB CT assemblies at varied pH values showed different chiroptical photothermic effects (CPEs) for the same incident chiral light despite the molecular chirality of PyC3His remaining unchanged, supporting an interesting supramolecular chirality-directed photothermic effect.

Designing supramolecular self-assembly nanomaterials as stimuli-responsive drug delivery platforms for cancer therapy

Stimuli-responsive nanomaterials have attracted substantial interest in cancer therapy, as they hold promise to deliver anticancer agents to tumor sites in a precise and on-demand manner. Interestingly, supramolecular chemistry is a burgeoning discipline that entails the reversible bonding between components at the molecular and nanoscale levels, and the recent advances in this area offer the possibility to design nanotherapeutics with improved controllability and functionality for cancer therapy. Herein, we provide a comprehensive summary of typical non-covalent interaction modes, which primarily include hydrophobic interaction, hydrogel bonding, host-guest interaction, π-π stacking, and electrostatic interaction. Special emphasis is placed on the implications of these interaction modes to design novel stimuli-responsive drug delivery principles and concepts, aiming to enhance the spatial, temporal, and dosage precision of drug delivery to cancer cells. Finally, future perspectives are discussed to highlight current challenges and future opportunities in self-assembly-based stimuli-responsive drug delivery nanotechnologies for cancer therapy.

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.

Recent Progress in Carrier-Free Nanomedicine for Tumor Phototherapy

Safe and effective strategies are urgently needed to fight against the life-threatening diseases of various cancers. However, traditional therapeutic modalities, such as radiotherapy, chemotherapy and surgery, exhibit suboptimal efficacy for malignant tumors owing to the serious side effects, drug resistance and even relapse. Phototherapies, including photodynamic therapy (PDT) and photothermal therapy (PTT), are emerging therapeutic strategies for localized tumor inhibition, which can produce a large amount of reactive oxygen species (ROS) or elevate the temperature to initiate cell death by non-invasive irradiation. In consideration of the poor bioavailability of phototherapy agents (PTAs), lots of drug delivery systems have been developed to enhance the tumor targeted delivery. Nevertheless, the carriers of drug delivery systems inevitably bring biosafety concerns on account of their metabolism, degradation, and accumulation. Of note, carrier-free nanomedicine attracts great attention for clinical translation with synergistic antitumor effect, which is characterized by high drug loading, simplified synthetic method and good biocompatibility. In this review, the latest advances of phototherapy with various carrier-free nanomedicines are summarized, which may provide a new paradigm for the future development of nanomedicine and tumor precision therapy.

Inverted and Amplified CP-EL Behavior Promoted by AIE-Active Chiral Co-Assembled Helical Nanofibers

It is well-known that high-performance circularly polarized organic light-emitting diodes (CP-OLEDs) remain a formidable challenge to the future application of circularly polarized luminescent (CPL)-active materials. Herein, the design of a pair of AIE-active chiral enantiomers (L/D-HP) is described to construct chiral co-assemblies with an achiral naphthalimide dye (NTi). The resulting co-assemblies emit an inverted CPL signal compared with that from the L/D-HP enantiomers. After thermal annealing at 120 °C, the inverted CPL signal of this kind of L/D-HP-NTi with a 1:1 molar ratio shows regular and ordered helical nanofibers arranged through intermolecularly ordered layered packing and is accompanied with a further amplified effect (|g_em | = 0.032, λ_em  = 535 nm). Significantly, non-doped CP-OLEDs based on a device emitting layer (EML) of L/D-HP-NTi exhibits a low turn-on voltage (V_on ) of 4.7 V, a high maximum brightness (L_max ) of 2001 cd m^-2 , and moderate maximum external quantum efficiency (EQE_max ) of 2.3%, as well as excellent circularly polarized electroluminescence (CP-EL) (|g_EL | = 0.023, λ_em  = 533 nm).

Chiral Naphthalenediimides with High-Efficiency Fluorescence and Circularly Polarized Luminescence in the Solid State for the Application in Organic Optoelectronics

Naphthalenediimides (NDIs) have been extensively studied due to their tunable luminescent properties. However, generally, the monomers or aggregates of non-core substituted NDIs exhibit low fluorescence quantum yields (Φ_FL <10 %) in the solid state, which limit their applications as light-emitting materials and render their chiral species unsuitable for circularly polarized luminescence (CPL). Herein, a series of non-core substituted chiral NDIs that exhibit high luminous efficiencies (Φ_FL up to 56.8 % for racemate and 36.5 % for enantiomer) and a strong CPL behavior in the solid state is reported. These significant improvements are attributed to the unique molecular conformation of the chiral NDIs and the formation of distinctive discrete dimers. The structures of the NDIs were significantly simpler and more accessible than those of other NDIs. The findings evidence that non-core substituted NDIs can exhibit strong fluorescence in the solid state and provide a new pathway to improve photophysical properties of NDIs.

Induced Circular Dichroism and Circularly Polarized Luminescence for Block Copolymers with Chiral Communications

Many sophisticated chiral materials are found in living organisms, giving specific functions and required complexity. Owing to the remarkable optical properties of chiral materials, they have drawn significant attention for the development of synthetic materials to give optical activities for appealing applications. In contrast to a top-down approach, the bottom-up approach from self-assembled systems with chiral host-achiral guest and achiral guest-chiral host for induced circular dichroism and induced circularly polarized luminescence has greatly emerged because of its cost-effective advantage with easy fabrication for mesoscale assembly. Self-assembled hierarchical textures with chiral sense indeed give significant amplification of the dissymmetry factors of absorption and luminescence (g_abs and g_lum ), resulting from the formation of well-ordered superstructures and phases with the building of chromophores and luminophores. By taking advantage of the microphase separation of block copolymers via self-assembly, a variety of well-defined chiral nanostructures can be formed as tertiary superstructures that can be further extended to quaternary phases in bulk or thin film. In this article, a conceptual perspective is presented to utilize the self-assembly of chiral block copolymers with chiral communications, giving quaternary phases with well-ordered textures at the nanoscale for significant enhancement of dissymmetry factors.

Stereomutation and chiroptical bias in the kinetically controlled supramolecular polymerization of cyano-luminogens

The synthesis of two pairs of enantiomeric cyano-luminogens 1 and 2, in which the central chromophore is a p-phenylene or a 2,5-dithienylbenzene moiety, respectively, is described and their supramolecular polymerization under kinetic and thermodynamic control investigated. Compounds 1 and 2 form supramolecular polymers by quadruple H-bonding arrays between the amide groups and the π-stacking of the central aromatic moieties. In addition, the peripheral benzamide units are able to form intramolecularly H-bonded pseudocycles that behave as metastable monomer M* thus affording kinetically and thermodynamically controlled aggregated species AggI and AggII. The chiroptical and emissive features of compounds 1 and 2 strongly depend on the aggregation state and the nature of the central aromatic unit. Compounds 1 exhibit a bisignated dichroic response of different intensity but with similar sign for both AggI1 and AggII1 species, which suggests the formation of helical aggregates. In fact, these helical supramolecular polymers can be visualized by AFM imaging. Furthermore, both AggI and AggII species formed by the self-assembly of compounds 1 show CPL (circularly polarized light) activity of opposite sign depending on the aggregation state. Thienyl-derivatives 2 display dissimilar chiroptical, morphological and emissive characteristics for the corresponding kinetically and thermodynamically controlled aggregated species AggI and AggII in comparison to those registered for compounds 1. Thus, a stereomutation phenomenon is observed in the AggI2 → AggII2 conversion. In addition, AggI2 is arranged into nanoparticles that evolve to helical aggregates to afford AggII2. The dissimilar chiroptical and morphological features of AggI2 and AggII2 are also appreciated in the emissive properties. Thus, whilst AggI2 experiences a clear AIE (aggregation induced emission) process and CPL activity, the thermodynamically controlled AggII2 undergoes an ACQ (aggregation caused quenching) process in which the CPL activity is cancelled.

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.

Signal Inversion and Amplification of Circularly Polarized Luminescence in a Poly(phenylacetylene)-Based Composite System Assisted by Achiral PMMA

Multichannel regulable circularly polarized luminescence (CPL) is fascinating because of its fundamental and application interest. There are few reports on helical sense (P-/M-helix) modulation and chiral signal amplification of polyacetylenes with the assistance of achiral polymers and further applications in precisely and conveniently regulating CPL handedness and magnitude. Herein, a helical poly(phenylacetylene)-based CPL-active system was constructed, in which CPL inversion occurred by adding achiral PMMA into a helical poly(phenylacetylene)-CHCl₃ solution. Significantly, there is almost 10 times magnification of luminescence dissymmetry factor values (|g_lum|) during this process. The above phenomena could be ascribed to the PMMA-assisted polyene backbone elongation and the formation of a more ordered helical structure for the poly(phenylacetylene)s. More interestingly, the CPL signal can be facilely inverted and switched by simply changing the thickness of the PPhAD/PMMA layer. The temperature-driven dynamic CPL handedness inversion and magnitude modulation can also be achieved. Based on the multiple regulations for CPL, logic operations were developed, and the practical application is further facilitated by designing various CPL patterns. This study establishes effective and convenient strategies to switch the handedness, magnitude, and wavelength of CPL, which may generate a breakthrough in the manufacturing of CPL-active smart materials and devices with promising application potential.

Host-Guest Complexation-Induced Aggregation Based on Pyrene-Modified Cyclodextrins for Improved Electronic Circular Dichroism and Circularly Polarized Luminescence

Several γ-cyclodextrin (CD) derivatives mono- or di-substituted by pyrenes at the primary rim of the CD were demonstrated to aggregate into nano-strips in aqueous solutions, with the pyrene moieties interpenetrating into γ-CD cavities. The hydrophobic complexation-induced aggregation provides a rigid chiral environment for the pyrenes and leads to significant electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) activities, giving unprecedently high g_abs and g_lum values up to 4.3×10^-2 and 5.3×10^-2 , respectively. The aggregates lead to excimer emission with high quantum yields and show B_CPL and Bⁱ _CPL up to 338. 6 M^-1  cm^-1 and 169.3 M^-1  cm^-1 , respectively.

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.

Selective Anticancer Materials by Self-Assembly of Synthetic Amphiphiles Based on N-Acetylneuraminic Acid

N-Acetylneuraminic acid (Neu5Ac), one of the abundant types of sialic acid, is an emerging anticancer agent owing to its ability to target selectins in the plasma membrane of cancer cells. Considering the functionality of Neu5Ac, obtaining novel Neu5Ac-conjugated materials with a selective and an enhanced antitumor activity has remained a challenge. Herein, we report the supramolecular materials of three novel amphiphiles composed of Neu5Ac as a hydrophilic segment and pyrene or adamantane as a hydrophobic segment. The synthetic amphiphiles 1, 2, and 3 self-assembled into ribbons, vesicles, and irregular aggregates in an aqueous solution, respectively. Among the materials, vesicles of amphiphile 2 showed the most substantial selectivity toward cancer cells, followed by cell death due to the production of reactive oxygen species by the pyrene group. The dual advantage of Neu5Ac-selectivity and the pyrene-cytotoxicity of vesicles of amphiphile 2 can provide a strategy for effective anticancer materials.

Double helical π-aggregate nanoarchitectonics for amplified circularly polarized luminescence

The canonical double helical π-stacked array of base pairs within DNA interior has inspired the interest in supramolecular double helical architectures with advanced electronic, magnetic and optical functions. Here, we report a selective-recognized and chirality-matched co-assembly strategy for the fabrication of fluorescent π-amino acids into double helical π-aggregates, which show exceptional strong circularly polarized luminescence (CPL). The single crystal structure of the optimal combination of co-assemblies shows that the double-stranded helical organization of these π-amino acids is cooperatively assisted by both CH-π and hydrogen-bond arrays with chirality match. The well-defined spatial arrangement of the π-chromophores could effectively suppress the non-radiative decay pathways and facilitate chiral exciton couplings, leading to superior CPL with a strong figure of merit (g_lum = 0.14 and QY = 0.76). Our findings might open a new door for developing DNA-inspired chiroptical materials with prominent properties by enantioselective co-assembly initiated double helical π-aggregation.

Synthesized or self-assembled helical architectures advance the development of chiral functional materials. Here the authors report a selective-recognized and chirality-matched co-assembly strategy for the fabrication of fluorescent π-amino acids into double helical π-aggregates with exceptional strong circularly polarized luminescence

Multiple Responsive CPL Switches in an Enantiomeric Pair of Perovskite Confined in Lanthanide MOFs

Circularly polarized luminescence (CPL) switches have attracted widespread attention due to their potential applications in advanced information technologies. However, the design and fabrication of solid-state multiple-responsive CPL switches remain challenging. Here, through self-assembly of chiral metal-organic frameworks (MOFs) and perovskite nanocrystals (NCs), a pair of crystalline enantiomeric (P)-(+)/(M)-(-)-EuMOF⊃MAPbX₃ (MA = CH₃ NH₃ ⁺ , X = Cl^- , Br^- , I^- ) adducts is prepared, where the achiral MAPbBr₃ perovskite NCs embedded into chiral MOFs inherit the chirality of host MOFs by host-guest EuBr and PbO coordination bonds, which is demonstrated by synchrotron-radiation-based X-ray absorption spectroscopy. The chiral adducts show enhanced photoluminescence quantum yield (PLQY), good thermal stability of CPL in air, and photoswitchable CPL properties upon altering different UV irradiation. Based on two chiral emission centers and their different characteristics, reversible CPL switches are realized upon a diversity of external stimuli, for example, chemicals (water /CH₃ NH₃ Br solution) or temperatures (room temperature/high temperature). Benefiting from the extraordinary stimuli-responsive and highly reversible switchable CPL, multiple information encryptions and decryptions integrated with CPL, together with a chiroptical logic gate are successfully designed. This work opens a new avenue to generally fabricate solid-state CPL composite materials and develops new applications based on switchable CPL.

Inverted Circularly Polarized Luminescence Behavior Induced by Helical Nanofibers through Chiral Co-Assembly from Achiral Liquid Crystal Polymers and Chiral Inducers

Chiral supramolecular assembly can provide a powerful strategy for developing circularly polarized luminescence (CPL)-active materials by forming helices or superhelices into single or multiple components. Herein, we chose three achiral liquid crystal polymers (LC-P1/P2/P3) and chiral binaphthyl-based inducers (R/S-M) with anchored dihedral angles to construct chiral co-assemblies and explore the induced CPL behavior from pyrenyl (Py) emitters in achiral LC polymers through the regulation of helical nanofibers during the supramolecular co-assembly process. Most interestingly, chiral co-assembly (R/S-M)_0.1-(P3)_0.9 emitted an inverted blue-colored CPL signal during thermal annealing treatment at the glass transition temperature due to the flexible main chain of the LC polymer (LC-P3). The strongest blue-colored CPL emission for the (R/S-M)_0.1-(P3)_0.9 spin-coated film (λ_em = 455 nm, |g_em| = 6.47 × 10^-2, Φ_F = 48.5%) could be detected by using thermal annealing treatment at 105 °C.

Arene-perfluoroarene interaction induced chiroptical inversion and precise ee% detection of chiral acids in a benzimidazole-involved ternary coassembly

Flexible regulation of chirality and handedness of chiral functional materials and quantitative sensing of natural chiral compounds remains a considerable challenge. Herein, an achiral fluorescent 1-pyrenecarboxylic acid-benzimidazole derivative (PBI) was synthesized and its chiroptical properties upon coassembly with chiral acids (TA and MA) and octafluoronaphthalene (OFN) through hydrogen bonds between benzimidazole and chiral acids as well as an arene-perfluoroarene (AP) interaction between a pyrene moiety and OFN were systemically studied. The binary assemblies of PBI/TA and PBI/MA displayed opposite chiroptical properties including circular dichroism (CD) and circularly polarized luminescence (CPL) signals. Interestingly, the handedness of CPL was further inverted in ternary assemblies due to the synergistic effect of the AP interaction and hydrogen bonds. Besides, the highly accurate chiral sensing of chiral acids via binary assemblies was successfully achieved with a high correlation coefficient. This work provides a simple method for regulating the handedness of chiroptical active materials and quantitative sensing of chiral acids through orthogonal multiple component coassemblies.