Chiral Nanostructures from Artificial Helical Polymers: Recent Advances in Synthesis, Regulation, and Functions

Helical structures such as right-handed double helix for DNA and left-handed α-helix for proteins in biological systems are inherently chiral. Importantly, chirality at the nanoscopic level plays a vital role in their macroscopic chiral functionalities. In order to mimic the structures and functions of natural chiral nanoarchitectures, a variety of chiral nanostructures obtained from artificial helical polymers are prepared, which can be directly observed by atomic force microscopy (AFM), scanning tunneling microscopy (STM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). This review mainly focuses on the formation of chiral nanostructures and the morphology regulation triggered by polymer chain length, concentration, solvent, temperature, photoirradiation, and chemical additives. In addition, the distinct chiral functions including chiral recognition, circularly polarized luminescence, drug release, cell imaging, and antibiosis are also discussed.

Multicolor and sign-invertible circularly polarized luminescence from nonchiral charge-transfer complexes assembled with N-terminal aromatic amino acids

Circularly polarized luminescence (CPL) materials with precisely controlled emission colors and handedness are highly desirable for their promising applications in advanced optical technologies, but it is rather challenging to obtain them primarily due to the lack of convenient, powerful, and universal preparation strategies. Herein, we report a simple yet versatile solution route for constructing multicolor CPL materials with controllable handedness from nonchiral luminescent charge-transfer (CT) complexes through co-assembly with chiral N-terminal aromatic amino acids. The resulting ternary co-assemblies exhibit obvious CPL signals from 489 to 601 nm, covering from blue via green and yellow to orange-red. Notably, the CPL sign can be readily inverted by changing the substituents at the α-position of amino acids or the molecular structure of achiral electron donors due to effects on the hydrogen bonds, CT interactions, and stacking patterns. This work provides a new insight into developing CPL materials with tunable color and inverted handedness.

Amplification and Attenuation of Asymmetry via Kinetically Controlled Seed-Induced Supramolecular Polymerization

The amplification of asymmetry in supramolecular polymers has recently garnered significant attention. While asymmetry amplification has predominantly been explored under thermodynamic conditions, the kinetic aspect of this process unveils intriguing observations, yet is scarcely reported in the literature. Herein, drawing inspiration from macromolecular systems, we propose a novel strategy for enhancing asymmetry in supramolecular polymers through a seed-induced supramolecular polymerization approach under kinetic conditions, employing a naphthalene diimide-derived monomer (ANSG) for template-induced supramolecular polymerization, utilizing adenosine triphosphate (ATP) and pyrophosphate (PPi) as templates. A chiral seed comprising [ANSG-ATP]S effectively amplifies the overall supramolecular asymmetry when exposed to a mixture of achiral templates (PPi) and monomers (ANSG), owing to its efficient seeding characteristics under kinetic conditions. As a result of efficient co-operativity, conversely, employing an achiral seed [ANSG-PPi]S in a mixture of chiral templates (ATP) and monomers (ANSG) results in the attenuation of asymmetry, highlighting the effective modulation achievable through the seeding approach, an unprecedented observation in the field. Exploiting the efficient aggregation-induced emission enhancement (AIEE) of the resultant supramolecular polymers further extends the amplification and attenuation of circularly polarized luminescence (CPL) as a potential function.

Lighting Up Bispyrene-Functionalized Chiral Molecular Muscles with Switchable Circularly Polarized Excimer Emissions

Aiming at the further extension of the application scope of traditional molecular muscles, a novel bispyrene-functionalized chiral molecular [c2]daisy chain was designed and synthesized. Taking advantage of the unique dimeric interlocked structure of molecular [c2]daisy chain, the resultant chiral molecular muscle emits strong circularly polarized luminescence (CPL) attributed to the pyrene excimer with a high dissymmetry factor (glum) value of 0.010. More importantly, along with the solvent- or anion- induced motions of the chiral molecular muscle, the precise regulation of the pyrene stacking within its skeleton results in the switching towards either "inversed" state with sign inversion and larger glum values or "down" state with maintained handedness and smaller glum values, making it a novel multistate CPL switch. As the first example of chiral molecular muscle-based CPL switch, this proof-of-concept study not only successfully widens the application scopes of molecular muscles, but also provides a promising platform for the construction of novel smart chiral luminescent materials for practical applications.

Dynamic Control of Chiral Recognition in Water-Soluble Naphthotubes Induced by Hydrostatic Pressure

The dynamic control of chiral (enantiomeric) responses in chiral host-guest complexes through external stimuli is a significant challenge in modern chemistry for developing smart stimuli-responsive materials. Herein, we report the (chir)optical properties and chiral recognition behavior of water-soluble chiral naphthotubes (1) under the influence of hydrostatic pressure as an external stimulus. The hydrostatic pressure spectral profiles compared to those obtained at normal pressure revealed the dynamic behavior of 1 under hydrostatic pressure, owing to the flexible linker. In chiral recognition experiments, hydrophilic amino acids such as phenylalanine (Phe) and tryptophan (Trp) exhibited reaction volume changes (ΔV°) of -0.9 cm3 mol-1 for d-Phe, -1.2 cm3 mol-1 for l-Phe, -5.6 cm3 mol-1 for d-Trp, and -7.0 cm3 mol-1 for l-Trp, with enantioselectivity ranging from 1.2 to 1.6. In contrast, hydrophobic chiral styrene oxide (2) showed ΔV° values of 1.5 cm3 mol-1 for R-2 and 3.5 cm3 mol-1 for S- 2, with a relatively higher enantioselectivity of up to 7.6. These contrasting effects of hydrostatic pressure primarily originate from the dynamics of chiral naphthotubes.

Recent Advances of Organic Cocrystals in Emerging Cutting-Edge Properties and Applications

Organic cocrystals, representing one type of new functional materials, have gathered significant interest in various engineering areas. Owing to their diverse stacking modes, rich intermolecular interactions and abundant functional components, the physicochemical properties of organic cocrystals can be tailored to meet different requirements and exhibit novel characteristics. The past few years have witnessed the rapid development of organic cocrystals in both fundamental characteristics and various applications. Beyond the typical properties like ambipolarity, emission tuning ability, ferroelectricity, etc. that are previously well demonstrated, many novel, impressive and cutting-edge properties and applications of cocrystals are also emerged and advanced recently. Especially during the nearest five years, photothermal conversion, room-temperature phosphorescence, thermally activated delay fluorescence, circularly polarized luminescence, organic solid-state lasers, near-infrared sensing, photocatalysis, batteries, and stimuli responses have been reported. In this review, these new properties are carefully summarized. Besides, some neoteric architecture and methodologies, such as host-guest structures and machine learning-based screening, are introduced. Finally, the potential future developments and expectations for organic cocrystals are discussed for further investigations on multiple functions and applications.

Reversible Circularly Polarized Luminescence Inversion and Emission Color Switching in Photo-Modulated Supramolecular Polymer for Multi-Modal Information Encryption

Constructing circularly polarized luminescence (CPL) materials that exhibit dynamic handedness inversion and emissive color modulation for multimodal information encryption presents both a significant challenge and a compelling opportunity. Here, we have developed a pyridinethiazole acrylonitrile-cholesterol derivative (Z-PTC) that exhibits wavelength-dependent photoisomerization and photocyclization, enabling dynamic handedness inversion and emissive color modulation in supramolecular assemblies with decent CPL activity. Coordination with Ag+ ions form the Z-PTC Ag supramolecular polymer (SP1), which assembles into nanotubes displaying enhanced positive yellow-green CPL. Irradiation at 454 nm transforms SP1 into nanospheres of a mixture supramolecular polymer (SP2) of Z/E-PTC Ag, displaying inverted supramolecular chirality and emitting negative orange-yellow CPL. Reheating SP2 to 343 K restores the original nanotube structure via excellent reversible photoisomerization. Exposure to 365 nm light also induces CPL inversion from positive to negative and triggers morphological changes from SP1 to SP2. Prolonged irradiation causes further transformation into irregular supramolecular aggregate, shifting the emission color to blue and eliminating CPL. These dynamic properties of the multicolor CPL system, including reversible handedness inversion, can also be realized in the semisolid state, exhibiting promising potential for multimodal information encryption applications with enhanced security and complexity.

Coaxial Helices in Chiral Supramolecular Aggregates from Highly Hindered Chiral Allenes

Chiral allenes self-assembly following a cooperative mechanism into a supramolecular chiral aggregate consisting of two coaxial helices: the internal helix described by the allene stack and the external helix which consist in a 4-helix described by the four allene substituents. More precisely, this supramolecular aggregate possesses six axially chiral elements within its structure-the allene, the allene stack (internal helix) and the stacks of the four allene substituents (external 4-helix)-. Interestingly, slight variations in the magnitude of the tilting degree while keeping its P- or M- orientation (internal helix) can vary the orientation of the 4-axial motifs at the external helix. Thus, while (P)-1 produces a supramolecular helix with a Θ ca. 15° (Pint) and a M1/P2/M1'/P2' orientation of the four axial motifs at the periphery, (P)-2 produces a supramolecular helix with a Θ ca. 23° (Pint) and a P1/P2/P1'/P2' orientation of the four axial motifs at the external helix. As a result, the ECD spectra and the AFM images of the (P)-1 and (P)-2 supramolecular aggregates dominated by the 1 and 1' substituents of the chiral allene indicate opposite handedness although the chirality of the building block and the orientation of the allene stack are the same.

Excitation-Dependent Circularly Polarized Luminescence Inversion Driven by Dichroic Competition of Achiral Dyes in Cholesteric Liquid Crystals

The development of stimuli-responsive chiral cholesteric liquid crystals (CLCs) materials holds significant potential for achieving three-dimensional (3D) anti-counterfeiting and multi-level information encryption. However, constructing phototunable CLCs systems with easy fabrication and fast response remains a great challenge. Herein, we exploit an excitation-dependent CLCs (ExD-CLCs) material by establishing dynamically photoresponsive dichroic competition between two achiral dyes: a negative dichroic dye (SP-COOH) and a positive dichroic dye (Nile Red, NR) within a CLCs medium. The ExD-CLCs exhibits a negative circularly polarized luminescence (CPL) signal (glum=-0.16) at 625 nm when excited at 365 nm. Remarkably, under excitation at 430 nm, the CPL signal is inverted, and the glum value increases to +0.26. Notably, the helical superstructure and handedness of the ExD-CLCs remain unchanged during this reversal process. The CPL signal reversal is driven by the dichroic competition between the SP-COOH dimer, which displays strong negative dichroism in its open-ring isomer form and silent negative dichroism in its closed-ring isomer form, and the NR dye, which exhibits static positive dichroism. Leveraging these excitation-dependent CPL properties, the quadruplex numerical anti-counterfeiting using ExD-CLCs is achieved.

Divergent Synthesis of Chiroptical Molecular Switches Based on 1,2-Diaxial Atropisomers

The development of chiroptical molecular switches for chiral sensing, data communication, optical displays, chiral logic gates, and asymmetric catalysis is currently a vibrant frontier of science and technology. Herein, we report a practical artificial dynamic system based on a 1,2-diaxial atropisomer. Organocatalytic parallel kinetic resolution allows the divergent synthesis of two sets of stereoisomers with vicinal C-C and N-N axes from the same racemic single-axis substrates. By simply varying the configuration of the single catalyst, all four stereoisomers are accessible. The successive conduction of covalent unlocking/locking and thermal-isomerization processes enables sequential switching between all four atropisomeric states with electronic circular dichroism signal reversal, providing an example of multistate chiroptical molecular switches.

Chiral Rotaxane-Branched Dendrimers as Relays in Artificial Light-Harvesting Systems with Boosted Circularly Polarized Luminescence

Starting from AIEgen-functionalized chiral [2]rotaxane building block, we have successfully synthesized a new class of chiral rotaxane-branched dendrimers through controllable divergent strategy for the first time, based on which novel chiral artificial light-harvesting systems (LHSs) were successfully constructed in aqueous phase by sequentially introducing achiral donor and acceptor. More importantly, accompanied by the two-step Förster resonance energy transfer (FRET) process in the resultant artificial LHSs, the sequentially amplified circularly polarized luminescence (CPL) performances were achieved, highlighting that the chiral rotaxane-branched dendrimers could serve as excellent relay for both energy transfer and chirality transmission. Impressively, compared with the sole chiral rotaxane-branched dendrimers, the dissymmetry factors (glum) values of the resultant artificial LHSs were amplified by one order of magnitude up to 0.038, enabling their further applications in information storage and encryption. The proof-of concept study provides not only a feasible approach for the efficient amplification of CPL performances but also a novel platform for the construction of novel chiral luminescent materials.

Reversible Local Protonation-Deprotonation: Tuning Stimuli-Responsive Circularly Polarized Luminescence in Chiral Hybrid Zinc Halides for Anti-Counterfeiting and Encryption

Precise control over the organic composition is crucial for tailoring the distinctive structures and properties of hybrid metal halides. However, this approach is seldom utilized to develop materials that exhibit stimuli-responsive circularly polarized luminescence (CPL). Herein, we present the synthesis and characterization of enantiomeric hybrid zinc bromides: biprotonated ((R/S)-C12H16N2)ZnBr4 ((R/S-LH2)ZnBr4) and monoprotonated ((R/S)-C12H15N2)2ZnBr4 ((R/S-LH1)2ZnBr4), derived from the chiral organic amine (R/S)-2,3,4,9-Tetrahydro-1H-carbazol-3-amine ((R/S)-C12H14N2). These compounds showcase luminescent properties; the zero-dimensional biprotonated form emits green light at 505 nm, while the monoprotonated form, with a pseudo-layered structure, displays red luminescence at 599 and 649 nm. Remarkably, the reversible local protonation-deprotonation behavior of the organic cations allows for exposure to polar solvents and heating to induce reversible structural and luminescent transformations between the two forms. Theoretical calculations reveal that the lower energy barrier associated with the deprotonation process within the pyrrole ring is responsible for the local protonation-deprotonation behavior observed. These enantiomorphic hybrid zinc bromides also exhibit switchable circular dichroism (CD) and CPL properties. Furthermore, their chloride counterparts were successfully obtained by adjusting the halogen ions. Importantly, the unique stimuli-responsive CPL characteristics position these hybrid zinc halides as promising candidates for applications in information storage, anti-counterfeiting, and information encryption.

Biofuel-Driven Stepping Chiral Supramolecular Transfer Container

Herein, we reported a biofuel-driven recyclable chiral supramolecular transfer container based on hexacationic triphenylamine cage and nucleotides. Possessing rotatable paddle rigid backbones, the artificial receptor effectively encapsulated nucleotides with a high binding constant up to 5.37×105 M-1 in water, displaying guest-induced efficient fluorescence enhancement with quantum yield increased from 6.5 % to 16.6 %. Especially, the achiral cage could effectively bind with adenosine triphosphate to activate chirality transfer from substrates to the single molecular container, giving circularly polarized luminescence at 575 nm and positive Cotton effect peaks with significant asymmetric factor (gabs=+6.4×10-4). Meanwhile, the adaptive chiral supramolecule not only has reversible thermal responsiveness but also could stepwise regulate chirality transfer by the catalysis of hexokinase and apyrase in tandem, showing recovery adaptive chirality after refueled, achieving dynamically regulated programmable multistate chiral luminescent supramolecules. Therefore, the biofuel-driven chiral supramolecular transfer container could be successfully applied in chiral logic gates and multilevel information encryption, providing new insight into intelligent chiral materials.

Pathway-directed recyclable chirality inversion of coordinated supramolecular polymers

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

Chiral nanoenzymes: synthesis and applications

Chiral nanoenzymes are a new type of material that possesses both chiral nanostructures and enzymatic catalytic activity. These materials exhibit selectivity in their catalytic activity towards organisms due to the introduction of chiral features in nanomaterials and have inherent chiral discrimination in organisms. As synthetic enzymes, chiral nanoenzymes offer significant advantages over natural enzymes. Due to their unique chiral structure and distinctive physicochemical properties, chiral nanoenzymes play an important role in various fields, including biology, medicine, and environmental protection. Their strong stereospecificity and biocompatibility make them useful in disease therapy, biosensing, and chiral catalysis, setting them apart from conventional and natural enzymes. In recent years, the design of synthetic methods and biological applications of chiral nanoenzymes has received significant attention and extensive research among scientists. This paper provides a systematic review of the research progress in the discovery, development, and application of chiral nanoenzymes in the last decade. Additionally, it presents various applications of chiral nanoenzymes, such as disease therapy, biosensing, and chiral catalysis. Finally, the challenges and future prospects of chiral nanoenzymes are discussed.

Configurationally Stepping Confinement Achieved Tunable Chiral Near-Infrared Luminescence Supramolecular Phenothiazine Organic Framework

Herein, thermally responsive reversible chiral supramolecules are reported, constructed by the chirality transfer from tripeptides to achiral network supramolecular organic frameworks (SOF) based on configurationally stepping confinement, which displayed not only highly selective reversible chirality transfer but also efficient enhanced near-infrared (NIR) luminescence. Taking advantage of macrocyclic confinement, CB[8] separately encapsulated two kinds of tetracationic bis(phenothiazines) derivatives (G1, G2) at 2:1 stoichiometric to form organic 2D SOFs, efficiently enhancing 12.6 fold NIR luminescence and blueshifted from 705 to 680 nm for G1, and redshifted from 695 to 710 nm for G2, respectively. Uncommonly, the tripeptide coassembled with two kinds of achiral noncovalent frameworks (G1/CB[8] or G2/CB[8]) displayed different opposite circular dichroism signals based on different binding modes and affinity, achieving chirality transfer from tripeptide to organic supramolecular assemblies with further enhanced NIR fluorescence up to 46.2 times and the quantum yield (QY) increased from 0.71% to 10.29% for G2/CB[8], showing reversible chirality transfer and tunable NIR fluorescence under thermal stimulus. Therefore, the current research has achieved controllable chirality transfer from tripeptide to the SOFs and the enhancement of tunable NIR fluorescence, which is successfully applied in thermal responsive chiral logic gates, information encryption, and cell imaging.

Concentration-Switchable Assembly of Carbon Dots for Circularly Polarized Luminescent Amplification in Chiral Logic Gates and Deep-Red Light-Emitting Diodes

Stimuli-responsive circularly polarized luminescent (CPL) materials are expected to find widespread application in advanced information technologies, such as 3D displays, multilevel encryption, and chiral optical devices. Here, using R-/S-α-phenylethylamine and 3,4,9,10-perylenetetracarboxylic dianhydride as precursors, chiral carbon dots (Ch-CDs) exhibiting bright concentration-dependent luminescence are synthesized, demonstrating reversible responses in both their morphologies and emission spectra. By adjusting Ch-CD concentration, the switchable wavelength is extended over 180 nm (539-720 nm), with the maximum quantum efficiency reaching 100%. Meanwhile, upon increasing Ch-CD concentration, the emission wavelength red-shifts, while the chirality of the assembled nanoribbons is synchronously amplified, ultimately achieving CPL at 709 nm and a maximum luminescence asymmetry factor of 2.18 × 10-2. These values represent the longest wavelength and the largest glum reported for CDs. Considering the remarkable optical properties of the synthesized Ch-CDs, multilevel chiral logic gates are designed, and their potential practical applications are demonstrated in multilevel anti-counterfeiting encryption, flexible electronic printing, and solid-state CPL. Furthermore, deep-red chiral electroluminescence light-emitting diodes (EL-LEDs) are prepared using these Ch-CDs, achieving an external quantum efficiency of 1.98%, which is the highest value reported to date for CDs in deep-red EL-LEDs, and the first report of chiral electronic devices based on CDs.

Supramolecular gels: a versatile crystallization toolbox

Supramolecular gels are unique materials formed through the self-assembly of molecular building blocks, typically low molecular weight gelators (LMWGs), driven by non-covalent interactions. The process of crystallization within supramolecular gels has broadened the scope of the traditional gel-phase crystallization technique offering the possibility of obtaining crystals of higher quality and size. The broad structural diversity of LMWGs allows crystallization in multiple organic and aqueous solvents, favouring screening and optimization processes and the possibility to search for novel polymorphic forms. These supramolecular gels have been used for the crystallization of inorganic, small organic compounds of pharmaceutical interest, and proteins. Results have shown that these gels are not only able to produce crystals of high quality but also to influence polymorphism and physicochemical properties of the crystals, giving rise to crystals with potential new bio- and technological applications. Thus, understanding the principles of crystallization in supramolecular gels is essential for tailoring their properties and applications, ranging from drug delivery systems to composite crystals with tunable stability properties. In this review, we summarize the use of LMWG-based supramolecular gels as media to grow single crystals of a broad range of compounds.

Chiral Co-assembly Based on a Stimuli-Responsive Polymer towards Amplified Full-Color Circularly Polarized Luminescence

Stimuli-responsive circularly polarized luminescence (CPL) materials have been attaching wide attention in the field of optical information storage and encryption, while still facing the challenge of the realization of high luminescence dissymmetry factors (glum). This work presents a pair of stimuli-responsive chiral co-assemblies P7R3 and P7S3 by combining polymer PFIQ containing iso-quinoline units with chiral inducers. The obtained chiral co-assemblies can reversibly undergo significant modification in CPL behavior under trifluoroacetic acid (TFA) fumigation and annealing treatment, with the |glum| values exhibiting a reversible shift between 0.2 and 0.3. Moreover, the chiral co-assemblies before TFA fumigating can effectively induce achiral emitters to generate intense full-color CPL signals through CPL energy transfer (CPL-ET), with the corresponding |glum| values larger than 0.2. Moreover, information encryption and decryption as well as a multi-level logic gates application are achieved by leveraging the reversible stimuli-responsive CPL activity of the chiral co-assembly. This work provides a new perspective for the construction of stimuli-responsive chiral luminescent materials with large |glum| values and the activation of CPL behavior in achiral emitters.

Ratiometric Chemosensors That Are Capable of Quantifying Hydrostatic Pressure Stimulus: A Case of Porphyrin Tweezers

Investigating chemosensors that are capable of quantifying pressure in solution, particularly hydrostatic pressure, which is one of the mechanical forces, is an attractive challenge in chemistry from the viewpoint of "mechano"-science. Herein, we report the investigation of chiral porphyrin tweezers, Por-Cy and Por-DPhEt, comprising different flexible linkers; Por-Cy and Por-DPhEt displayed distinct ratiometric signaling by using the higher excited S2 state with a standard excited S1 level. A novel operative mechanism using the S1/S2 fluorescence ratio was revealed using hydrostatic pressure-ultraviolet/visible (UV/vis), fluorescence/excitation, circular dichroism spectroscopy, and lifetime measurements, which can be further controlled by the open-closed conformational change inherent in the tweezer skeleton. Furthermore, the fluorescent chiral tweezers exhibited a promising |g lum| of 2.9 × 10-3, indicating that they are potential candidates for sensory applications in chiral environments. This study provides opportunities for the development of smart pressure-responsive chemosensors.

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.

Multi-Stimuli-Responsive Network of Multicatalytic Reactions using a Single Palladium/Platinum Catalyst

Given her unrivalled proficiency in the synthesis of all molecules of life, nature has been an endless source of inspiration for developing new strategies in organic chemistry and catalysis. However, one feature that remains thus far beyond chemists' grasp is her unique ability to adapt the productivity of metabolic processes in response to triggers that indicate the temporary need for specific metabolites. To demonstrate the remarkable potential of such stimuli-responsive systems, we present a metabolism-inspired network of multicatalytic processes capable of selectively synthesising a range of products from simple starting materials. Specifically, the network is built of four classes of distinct catalytic reactions-cross-couplings, substitutions, additions, and reductions, involving three organic starting materials-terminal alkyne, aryl iodide, and hydrosilane. All starting materials are either introduced sequentially or added to the system at the same time, with no continuous influx of reagents or efflux of products. All processes in the system are catalysed by a multifunctional heteronuclear PdII/PtII complex, whose performance can be controlled by specific additives and external stimuli. The reaction network exhibits a substantial degree of orthogonality between different pathways, enabling the controllable synthesis of ten distinct products with high efficiency and selectivity through simultaneous triggering and suppression mechanisms.

A photoactivated chiral molecular clamp rotated by selective anion binding

Developing chiral molecular platforms that respond to external fields provides opportunities for designing smart chiroptical materials. Herein, we introduce a molecular clamp whose chiral properties can be turned on by photoactivation. Selective anion binding achieves rational tuning of the conformations and chiroptical properties of the clamp, including circular dichroism and circularly polarized luminescence. Cyanostilbene segments were conjugated to chiral amines with a rotatable axis. Negligible chiroptical signals were significantly enhanced through a light illumination-induced isomerization. Binding with halide ions (F-, Cl- and Br-) enables chiroptical inversion and subsequent amplification of the resulting opposite handedness state by photo treatment. In contrast, the larger I- and NO3 - ions failed to achieve chiroptical inversion. Also the handedness inversion was hampered in conformationally locked amines. Density-functional theory-based computational studies and experimental results reveal a structural transformation that proceeds from a butterfly-like open geometry to a closed V-shaped state initiated by four hydrogen bonds and the rotatable axis. This work illustrates design protocols for use in smart chiroptical molecular platforms mediated by photo treatment and anion binding.

A Double Twisted Nanographene with a Contorted Pyrene Core

The mature synthetic methodologies enable us to rationally design and produce chiral nanographenes (NGs), most of which consist of multiple helical motifs. However, inherent chirality originating from twisted geometry has just emerged to be employed in chiral NGs. Herein, we report a red-emissive chiral NG constituted of orthogonally arranged two-fold twisted π-skeletons at a contorted pyrene core which contributes to optical transitions of S0→S1 and vice versa. The thus-obtained NG exhibited a robustness on its redox properties through 2e- uptake/release. The chemical oxidation generated stable radical cation whose absorption covers near-infrared I and II regions. Overall, the contorted pyrene core governs electronic nature of the chiral NG. The twist operation on NGs would be, therefore, a design strategy to alter conventional chirality induction on NGs.

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.

Strong coupling of an epsilon-near-zero mode to a chiral plasmon

The reconfigurable chiroptical effect is highly desirable for spin photonics, chiral spectroscopy, and photocatalysis due to its merits for dynamic and broadband applications. The coupling of an epsilon-near-zero (ENZ) mode to a chiral plasmon is expected to enable active and effective manipulation of the chiroptical effect but remains unexplored. Here we, for the first time to our knowledge, propose and demonstrate the strong coupling of an ENZ mode to a chiral plasmon by using a hybrid system composed of two identical vertically placed gold nanorods and an in-between ENZ film. An analytical three-oscillator model combined with numerical simulations is established to study the coupling mechanism, which predicts a Rabi splitting up to 240 meV with an ENZ film thickness of 60 nm in circular dichroism.

Multidimensional Dynamic Control of Supramolecular Phthalocyanine Gear: A Self-Assembly System Responding to Solvent, Temperature, and Hydrostatic Pressure

Smart supramolecular materials that respond toward various external stimuli hold great promise for various applications in molecular memories, logic gates, and drug delivery systems. In this study, the active control over the self-assembly of phathalocyanine gear was achieved by combining temperature and hydrostatic pressure stimuli with a dynamic solvent. Eventually, we found that the supramolecular gear can behave as a logic gate; "engaged" (+1) or "not" (0) state is switchable by solvent, temperature, and hydrostatic pressure. This paper describes not only new aspects for the rational design of smart stimuli-responsive supramolecular materials but also the significance of multidimensional dynamic control.

Switchable Dual Circularly Polarized Luminescence in Through-Space Conjugated Chiral Foldamers

Organic materials with switchable dual circularly polarized luminescence (CPL) are highly desired because they can not only directly radiate tunable circularly polarized light themselves but also induce CPL for guests by providing a chiral environment in self-assembled structures or serving as the hosts for energy transfer systems. However, most organic molecules only exhibit single CPL and it remains challenging to develop organic molecules with dual CPL. Herein, novel through-space conjugated chiral foldamers are constructed by attaching two biphenyl arms to the 9,10-positions of phenanthrene, and switchable dual CPL with opposite signs at different emission wavelengths are successfully realized in the foldamers containing high-polarizability substitutes (cyano, methylthiol and methylsulfonyl). The combined experimental and computational results demonstrate that the intramolecular through-space conjugation has significant contributions to stabilizing the folded conformations. Upon photoexcitation in high-polar solvents, strong interactions between the biphenyl arms substituted with cyano, methylthio or methylsulfonyl and the polar environment induce conformation transformation for the foldamers, resulting in two transformable secondary structures of opposite chirality, accounting for the dual CPL with opposite signs. These findings highlight the important influence of the secondary structures on the chiroptical property of the foldamers and pave a new avenue towards efficient and tunable dual CPL materials.

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.

An enzymolysis-induced energy transfer co-assembled system for spontaneously recoverable supramolecular dynamic memory

The continuing growth of the digital world requires new ways of constructing memory devices to process and store dynamic data, because the current ones suffer from inefficiency, limited reads, and difficulty to manufacture. Here we propose a supramolecular dynamic memory (SDM) strategy based on an enzymolysis-induced energy transfer co-assembly derived from a naphthalene-based cationic monomer and organic dye sulforhodamine 101, enabling the construction of spontaneously recoverable dynamic memory devices. Benefitting from the large exciton migration rate (4.48 × 1015 L mol-1 s-1) between the monomer and sulforhodamine 101, the energy transfer process between the two is effectively achieved. Since alkaline phosphatase can selectively hydrolyze adenosine triphosphate, leading to the disruption of the co-assemblies, an enzyme-mediated time-dependent fluorochromic system is realized. On this basis, a SDM system featuring spontaneous recovery and enabling the memory of dynamic information in optical and electrical modes is successfully constructed. The current study represents a promising step in the nascent development of supramolecular materials for computational systems.

Enantiomerically Resolvable Inherent Chirality Induced by Strong Para-Steric Hindrance in Cycloparaphenylene-Based Carbon Nanohoops

The chemical modification of the achiral carbon nanohoops to break the symmetry will result in inherently chiral structures with interesting optical properties. Herein, we report two novel π-extended chiral macrocycles, cyclo[10]paraphenylene-pyrene ([10]CPP-2Pyrene) and cyclo[10]paraphenylene-hexa-peri-hexabenzocoronene ([10]CPP-2HBC). The large substituents on the nanohoop peripheries effectively prevented free rotation and the racemization process. The conformation of each enantiomer is stable enough to be resolved by recycling HPLC.

Photon Upconversion Cooperates with Downshifting in Chiral Systems: Modulation, Amplification, and Applications of Circularly Polarized Luminescence

Circularly polarized luminescence (CPL)-active materials are increasingly recognized for their potential applications such as 3D imaging, data storage, and optoelectronic devices. Typically, CPL materials have required high-energy (HE) photons for excitation to emit low-energy (LE) circularly polarized light, a process known as downshifting CPL (DSCPL). However, the emergence of upconverted CPL (UCCPL), where the absorption of multi LE photons results in the emission of a single HE photon with circular polarization, has recently attracted considerable attention. This minireview highlights the intricate relationship between upconversion and CPL phenomena. During upconversion, the dissymmetry factor (glum) value can be improved in certain systems. Additionally, the integration of both LE and HE photons in upconversion-downshifting-synergistic systems offers avenues for dual-excitation or dual-emission CPL functionalities. More in detail, the emerging UCCPL based on various photon upconversion mechanisms and their synergy with DSCPL are introduced. Additionally, several examples that demonstrate the applications of UCCPL are presented to highlight the future opportunities.

Cholesterol-substituted spiropyran: Photochromism, thermochromism, mechanochromism and its application in time-resolved information encryption

Organic multi-stimulus-responsive materials are widely used in anti-counterfeiting and information encryption due to their unique response characteristics and designability. However, progress in obtaining multi-stimulus-responsive smart materials has been very slow. Herein, a spiropyran derivative is constructed, which shows photochromic, thermochromic and mechanical photochromic properties, and has reversible absorption/luminescence adjustment ability. By introducing non-covalent interactions such as van der Waals force and hydrogen bond, this new molecule is more sensitive to external stimuli and exhibits better photochromic, mechanochromic and thermochromic properties with rapid speed and high contrast. Furthermore, these three stimulus responses can be completely restored to the initial state under white light irradiation. The reversible multiple response characteristics of this molecule make it possible to provide dynamic anti-counterfeiting and advanced information encryption capabilities. To demonstrate its application in advanced information encryption, powders treated with different stimuli are combined with fluorescent dyes to encrypt complex digital information. This work puts forward a new time-resolved encryption strategy, which provides important guidance for the development of time-resolved information security materials.

When quantum dots meet blue phase liquid crystal elastomers: visualized full-color and mechanically-switchable circularly polarized luminescence

Polymer-based circularly polarized luminescence (CPL) materials with the advantage of diversified structure, easy fabrication, high thermal stability, and tunable properties have garnered considerable attention. However, adequate and precise tuning over CPL in polymer-based materials remains challenging due to the difficulty in regulating chiral structures. Herein, visualized full-color CPL is achieved by doping red, green, and blue quantum dots (QDs) into reconfigurable blue phase liquid crystal elastomers (BPLCEs). In contrast to the CPL signal observed in cholesteric liquid crystal elastomers (CLCEs), the chiral 3D cubic superstructure of BPLCEs induces an opposite CPL signal. Notably, this effect is entirely independent of photonic bandgaps (PBGs) and results in a high glum value, even without matching between PBGs and the emission bands of QDs. Meanwhile, the lattice structure of the BPLCEs can be reversibly switched via mechanical stretching force, inducing on-off switching of the CPL signals, and these variations can be further fixed using dynamic disulfide bonds in the BPLCEs. Moreover, the smart polymer-based CPL systems using the BPLCEs for anti-counterfeiting and information encryption have been demonstrated, suggesting the great potential of the BPLCEs-based CPL active materials.

Accelerating Cellular Uptake with Unnatural Amino Acid for Inhibiting Immunosuppressive Cancer Cells

Targeting immunosuppressive metastatic cancer cells is a key challenge in therapy. We recently have shown that a rigid-rod aromatic, pBP-NBD, that responds to enzymes and kill immunosuppressive metastatic osteosarcoma (mOS) and castration resistant prostate cancer (CRPC) cells in mimetic bone microenvironment. However, pBP-NBD demonstrated moderate efficacy against CRPC cells. To enhance activity, we incorporated the unnatural amino acid L- or D-4,4'-biphenylalanine (L- or D-BiP) into pBP-NBD, drastically increasing cellular uptake and CRPC inhibition. Specifically, we inserted BiP into pBP-NBD to target mOS (Saos2 and SJSA1) and CRPC (VCaP and PC3) cells with overexpressed phosphatases. Our results show that the D-peptide backbone with an aspartate methyl diester at the C-terminal offers the highest activity against these immunosuppressive mOS and CRPC cells. Importantly, imaging shows that the peptide assemblies almost instantly enter the cells and accumulate primarily within the endoplasmic reticulum of Saos2, SJSA1, and PC3 cells and at the lysosomes of VCaP cells. By using BiP to boost cellular uptake and self-assembly within cancer cells, this work illustrates an unnatural hydrophobic amino acid as a versatile and effective residue to boost endocytosis of synthetic peptides for intracellular self-assembly.

Amplified Circularly Polarized Luminescence Behavior in Chiral Co-assembled Liquid Crystal Polymer Films via the Strategic Manipulation of Chiral Inducers

One of the most important factors for the future application of circularly polarized luminescence (CPL) materials is their high dissymmetry factors (gem), and more and more studies are working tirelessly to focus on increasing the gem value. Herein, we chose an achiral liquid crystal polymer (LC-P) and two chiral binaphthyl-based inducers (R/S-3 and R/S-6) with different substitution positions (3,3' positions for R/S-3 and 6,6' positions for R/S-6) to construct chiral co-assemblies and explored their induced amplification CPL behaviors. Interestingly, after the thermal annealing treatment, this kind of chiral co-assembly (R/S-3)0.05-(LC-P)0.95 can emit a superior CPL signal (|gem| = 0.31 and λem = 424 nm), which achieves about 13-fold signal amplification in the spin-coated film, compared to (R/S-6)0.1-(LC-P)0.9 (|gem| = 0.023 and λem = 424 nm). This is because (R/S-3)0.05-(LC-P)0.95 could further co-assemble to form a more ordered arrangement LC state and generate regular helix nanofibers than that of (R/S-6)0.1-(LC-P)0.9. This work provides an efficient method for synthesizing high-quality CPL-active materials through the strategic manipulation of the structure of chiral binaphthyl-based inducers in chiral co-assembled LCP systems.

Synthesis and Photophysical Properties of a Chiral Carbon Nanoring Containing Rubicene

Herein we report the construction of an inherently chiral carbon nanoring, cyclo[7]paraphenylene-2,9-rubicene ([7]CPPRu2,9), by combining rubicene with a C-shaped synthon through the Suzuki-Miyaura coupling reaction. The structure was fully confirmed by high-resolution mass spectroscopies (HR-MS) and various NMR techniques. The photophysical properties were investigated by UV-vis absorption and fluorescence spectroscopy as well as the time-resolved fluorescence decay. Moreover, two enantiomers (M)/(P)-[7]CPPRu2,9 were successfully resolved by recyclable HPLC and studied by CD and CPL spectra.

Construction of a pillar[5]arene-based supramolecular chiral polymer linked to aminophosphine salt for chiral recognition of enantiomers of mandelic acid

In recent years, supramolecular chirality has been greatly developed in asymmetric synthesis, chiral sensing and other research fields, but its application in molecular chiral recognition has not been extensively studied. In this paper, L-Boc-tyrosine methoxyester and phosphorus chloride salts were introduced into the framework of pillar[n]arene, and a pillar[5]arene-based supramolecular chiral polymer L-TPP-P was constructed. The supramolecular polymer had stable supramolecular chiral properties and could be used as a chiral solvation reagent for chiral recognition of mandelic acid MA. The molar ratio method and Scatchard plot showed that the complexation ratio of L-TPP-P (pillar[5]arene monomer as the reference object) and MA was 1 : 1, and the complexation constants of L-TPP-P with R-MA and S-MA were 4.51 × 105 M-1 and 6.5 × 104 M-1, respectively. The significant affinity difference of L-TPP-P for different enantiomers of MA showed the excellent chiral recognition and stereoselectivity of pillar[5]arene-based supramolecular polymers for MA. This study provides a new idea for a novel supramolecular polymer chiral recognition reagent or chiral recognition method.

Switchable supramolecular helices for asymmetric stereodivergent catalysis

Despite recent developments on the design of dynamic catalysts, none of them have been exploited for the in-situ control of multiple stereogenic centers in a single molecular scaffold. We report herein that it is possible to obtain in majority any amongst the four possible stereoisomers of an amino alcohol by means of a switchable asymmetric catalyst built on supramolecular helices. Hydrogen-bonded assemblies between a benzene-1,3,5-tricarboxamide (BTA) achiral phosphine ligand coordinated to copper and a chiral BTA comonomer are engaged in a copper-hydride catalyzed hydrosilylation and hydroamination cascade process. The nature of the product stereoisomer is related to the handedness of the helices and can thus be directed in a predictable way by changing the nature of the major enantiomer of the BTA comonomer present in the assemblies. The strategy allows all stereoisomers to be obtained one-pot with similar selectivities by conducting the cascade reaction in a concomitant manner, i.e. without inverting the handedness of the helices, or sequentially, i.e. by switching the handedness of the supramolecular helices between the hydrosilylation and hydroamination steps. Supramolecular helical catalysts appear as a unique and versatile platform to control the configuration of molecules or polymers embedding several stereogenic centers.

Ultrasensitive Solvatochirochromism of Single Benzene Chromophores

Solvents influence the structure, aggregation and folding behaviors of solvatochromic compounds. Ultrasensitive solvent mediated chiroptical response is conducive to the fabrication of molecular platform for sensing and recognition, which however, remains great challenges in conceptual or applicable design. Here we report a cysteine-based single benzene chromophore system that shows ultrasensitivity to solvents. Compared to the ratiometrically responsive systems, the chiroptical activities could be triggered or inverted depending on the substituents of chiral entities with an ultralow solvent volume fraction (<1 vol %). One drop of dipolar solvents shall significantly induce the emergence or inversion of chiroptical signals in bulky phases. Based on the experimental and computational studies, the ultrasensitivity is contributed to the intimate interplay between solvents and chiral compounds that anchors the specific chiral conformation. It illustrates that structurally simple organic compounds without aggregation or folding behaviors possess pronounced solvatochiroptical properties, which sheds light on the next-generation of chiroptical sensors and switches.

Temperature-Induced Sign Inversion of Circularly Polarized Luminescence of Binaphthyl-Bridged Tetrathiapyrenophanes

D2-symmetric (R)-binaphthyl-bridged pyrenophanes containing thioether bonds were synthesized. The pyrenophanes exhibited the temperature-induced sign inversion of circularly polarized luminescence (CPL) while maintaining the emission wavelength and reversibility. The Δglum value reached 0.02, and the FL quenching by heat was negligible. The sign inversion of CPL originates from the inversion of intramolecular excimer chirality associated with excitation dynamics. The two pyrenes form a kinetically trapped left-handed twist excimer at low temperatures, while they form a thermodynamically favored right-handed twist excimer at high temperatures. The thioether linkers can impart flexibility suitable for the inversion of chirality of the excimers.

Light-Driven Sign Inversion of Circularly Polarized Luminescence Enabled by Dichroism Modulation in Cholesteric Liquid Crystals

Stimuli-responsive circularly polarized luminescence (CPL) materials show great promise in applying information encryption and anticounterfeiting. Herein, light-driven CPL sign inversion is achieved by combining a photoresponsive achiral negative dichroic dye (KG) and a static achiral positive dichroic dye (NR) as dopants at the 0.5:0.5 weight ratio into the cholesteric liquid crystal (CLC) host. The side chains of KG undergo trans/cis isomerization after 365 nm UV light irradiation, leading to the dichroism (SF) decrease. The |glum| value of CLC doping with KG (CLC-KG) weakens from 0.67 to 0.28 in response to the order degree change. Taking advantage of its unique CPL response property, the light-driven CPL sign inversion is achieved (from -0.20/0.14 to 0.02/-0.04) by incorporating NR (0.5:0.5) into the CLC-KG with helical superstructure static. Based on the synergistic use of circular polarization and responsiveness state as cryptographic primitives, the multidimensional information encryption CLC system can be realized.

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.

Circularly polarized luminescence and high photoluminescence quantum yields from rigid 5,10-dihydroindeno[2,1-a]indene and 2,2'-dialkoxy-1,1'-binaphthyl conjugates and copolymers

5,5,10,10-Tetramethyl-5,10-dihydroindeno[2,1-a]indene (COPV1(Me)) was installed into either the 3,3'- or 6,6'-positions of chiral 2,2'-dioctyloxy-1,1'-binaphthyl to afford 2 : 1 conjugates (monomeric compounds) and 1 : 1 copolymers. These compounds showed high photoluminescence quantum yields of >0.95 whilst also exhibiting circular dichroism (CD) and circularly polarized luminescence (CPL). The dissymmetry factors of CPL (gCPL) for the 3,3'- and 6,6'-monomeric compounds in THF were 6.6 × 10-4 and 3.3 × 10-4, respectively. The 3,3'-isomer has a higher g value than the 6,6'-isomer, which was attributed to the difference in the extent of π-conjugation and the angle between electronic and magnetic transition moments. The gCPL values of the 3,3'-linked and 6,6'-linked copolymers were 1.1 × 10-3 and 6.8 × 10-4, respectively. The structural rigidity of the COPV units is beneficial to achieve relatively high g values whilst maintaining a photoluminescence quantum yield that is close to unity by using a single type of fluorophore.

Multiple hydrogen bonding driven supramolecular architectures and their biomedical applications

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

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

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

Enhancing the Circularly Polarized Luminescence of Europium Coordination Polymers by Doping a Chromophore Ligand into Superhelices

Lanthanide-based molecular materials showing efficient circularly polarized luminescence (CPL) activity with a high quantum yield are attractive due to their potential applications in data storage, optical sensors, and 3D displays. Herein we present an innovative method to achieve enhanced CPL activity and a high quantum yield by doping a chromophore ligand into a coordination polymer superhelix. A series of homochiral europium(III) phosphonates with a helical morphology were prepared with the molecular formula S-, R-[Eu(cyampH)3-3n(nempH)3n]·3H2O (S/R-Eu-n, n = 0-5%). The doping of chromophore ligand S- or R-nempH2 into superhelices of S/R-Eu-0% not only turned on the CPL activity with the dissymmetry factor |glum| on the order of 10-3 but also increased the quantum yield by about 14-fold. This work may shed light on the development of efficient CPL-active lanthanide-based coordination polymers for applications.

Modulation of the assembly fashion among metal-organic frameworks for enantioretentive epoxide activation

Highly enantioretentive alcoholysis of epoxides is an important way to synthesize enantiopure β-alkoxy alcohols, which are irreplaceable intermediates demanded by biomedicines, fine chemicals and other industries. In this report, we exploit a series of Zr-based metal-organic frameworks (Zr-MOFs) as the catalysts to achieve high activity and enantioretentivity in the alcoholysis of styrene oxide via modulating their assembly fashions. It is explored that hcp-UiO-66 not only exhibits a ∼10 fold improved catalytic activity than both hxl-CAU-26 and fcc-UiO-66 of varied assemblies but also maintains superior product enantioretentivity. Theoretic calculations together with experimental proof discloses the origin of distinct catalytic activity caused by different assembly fashions. This assembly modulation strategy offers a potential protocol for seeking high-performance catalysts among MOFs by virtue of their rich polymorphisms.

Substituent alkyl-chain-dependent supramolecular chirality, tunable chiroptical property, and dye adsorption in azobenzene-glutamide-amphiphile based hydrogel

Controlling the supramolecular chirality of a self-assembly system by molecular structure design and external stimuli in aqueous solution is significant but challenging. Here, we design and synthesize several glutamide-azobenzene-based amphiphiles with different length alkyl chains. The amphiphiles can form self-assemblies in aqueous solution and show CD signals. As the number of the alkyl chain of amphiphiles increases, the CD signals of the assemblies can be enhanced. However, the long alkyl chains conversely restrict the isomerization of the azobenzene and the corresponding chiroptical property. Moreover, the alkyl length can determine the nanostructure of the assemblies and exert critical influence on the dye adsorption efficiency. This work exhibits some insights into the tunable chiroptical property of the self-assembly by delicate molecular design and external stimuli, and emphasizes the molecular structure can determine the corresponding application.