Chirality-sensing supramolecular systems

Racemization of Cross-Chain Bridging Cryptands: Effects of Linker Combination on Racemization Rate

We synthesized three 28-membered chiral cross-chain bridging cryptands ([3.3.6], [4.4.5], and [5.5.4]) with three different linker combinations. After the separation of their enantiomers, the racemization behavior of the cryptands was evaluated by chiral high-performance liquid chromatography. As the number of ethylene glycol units in the two cross-chain linkages increased, the racemization reaction proceeded slowly.

Emergent chiral and topological nanoarchitectonics in self-assembled supramolecular systems

The fabrication of structures with designated topologies at the nanoscale is an intriguing issue, attributed to the possibility of both imparting unique properties to functional materials and unravelling the codes that lie in many natural systems. As a significant bottom-up approach, the self-assembly strategy is potent in formulating various exquisite structures. While the building of common types of miniaturized structures such as tubes, twists and spheres has been investigated in depth to gain insight into the intrinsic principles that dictate their formation and functions, the preparation of peculiar topological nanostructures is still scattered and unsystematic. In parallel, chirality is among the most ubiquitous phenomena of fundamental significance in nature and is in close relationship with the origin of life. Essentially, chirality represents a type of orderliness and thus may interplay with peculiar topologies in an orchestrated and serendipitous way. In this review, we describe the development of constructing emergent chiral and topological nanoarchitectures via the self-assembly method, mainly focusing on structures including toroids, catenanes, Möbius strips, spirals and fractals. In addition, other types involving toruloids/kebabs, trumpets and bamboos, screws, dendritic and lamellar twists are also exemplified. The design of building blocks and various self-assembling strategies towards these target architectures are highlighted in this review, in an effort to provide an overview of the feasible approaches that facilitate the tailored construction of mesoscopic structures.

Chiral nanographenes exhibiting circularly polarized luminescence

Chiral nanographenes constitute an unconventional material class that deviates from planar graphene cutouts. They have gained considerable attention for their ability to exhibit circularly polarized luminescence (CPL), which offers new opportunities in chiral optoelectronics. Their unique π-conjugated architectures, coupled with the ability to introduce chirality at the molecular level, have made them powerful contenders in developing next-generation optoelectronic devices. This review thoroughly explores recent advances in the synthesis, structural design, and CPL performance of chiral nanographenes. We delve into diverse strategies for inducing chirality, including covalent functionalization, helically twisted frameworks, and heteroatom doping, each of which unlocks distinct CPL behaviors. In addition, we discuss the mechanistic principles governing CPL and future directions in chiral nanographenes to achieve high dissymmetry factors (glum) and tunable emission properties. We also discuss the key challenges in this evolving field, including designing robust chiral frameworks, optimizing CPL efficiency, and scaling up real-world applications. Through this review, we aim to shed light on recent developments in the bottom-up synthesis of structurally precise chiral nanographenes and evaluate their impact on the growing domain of circularly polarized luminescent materials.

Enantioselective Discrimination of l-Phenylglycine Ethyl Ester through Supramolecular Assembly with a Binaphthyl-Linked Zinc Bisporphyrinate Host

Chiral discrimination of amino acid stereoisomers is essential for biological processes and pharmaceutical development. Bisporphyrins represent promising candidates for the chiral recognition of amino acid derivatives. Herein, we report a rationally designed binaphthyl-linked zinc bisporphyrinate complex demonstrating remarkable enantioselective binding toward l-phenylglycine ethyl ester (L-PhgOEt). The complex demonstrates a 19-fold amplification in circular dichroism (CD) response intensity for L-PhgOEt over its d-enantiomer, with quantified enantioselectivity (L/D = 4.8), reflecting good chiral recognition capabilities. Single-crystal X-ray analysis unveils a multimodal recognition mechanism involving (i) axial coordination to zinc centers, (ii) hydrogen bonding interactions with amide functionalities, and (iii) π-system stabilization through both C-H···π and O···π interactions with the methoxy-functionalized binaphthyl linker. This synergistic combination of coordination bonds and noncovalent interactions establishes bisporphyrins as tailorable chiral receptors and guides the design of biomimetic systems for pharmaceutical applications.

Chiral polymer-induced hydroxyapatite for promoting bone regeneration

Chirality is one of the basic characteristics of living matter, yet the effect of chiral polymers on osteogenesis is seldom studied. Thus, it is necessary to deeply recognize the behaviors of chiral polymers in osteogenic processes, which can be beneficial for the development of bone repair materials. In this work, chiral hydroxyapatite (HAP) was constructed simply using poly(levorotatory/dextral-tartaric acid) as the guest of the chiral transfer system. We studied the influence of chiral HAPs on the migration and differentiation of pre-osteoblasts, and angiogenesis of endothelial cell in vitro. The results showed that poly(levorotatory-tartaric acid)-induced HAP did promote vascular remodeling and exhibited excellent impact on osteogenetic differentiation by improving the related gene and protein expression, whereas no significant change was observed in poly(dextral-tartaric acid) or poly(racemic-tartaric acid) induced HAP, respectively. This study highlighted the effects of chiral polymers on osteogenic potential, which laid the groundwork for the development of biomaterials for bone regeneration.

Raman Optical Activity Enhanced via Supramolecular Aggregation and Other Intermolecular Interactions-A Review

In this review, we show that Raman optical activity (ROA) combined with electronic circular dichroism (ECD) are effective tools for detecting supramolecular chirality and related processes such as chiral signal amplification and chirality transfer (also called induction) between chiral and achiral solutes. Research on spontaneous self-organization has led to significant discoveries in vibrational optical activity (VOA) over the past decade. As a leading topic, we discuss different aggregation pathways of carotenoids, which contributed to the definition of new phenomena in the field of ROA, i.e., aggregation-induced resonance Raman optical activity (AIRROA), and the first chirality induction observed in nature. We present the chirality of carotenoids as i) amplification via supramolecular assembly, ii) induction by a small number of chiral monomers, and iii) transfer from the local environment. We also report here other complex systems that are relevant to the VOA community in the context of chiroptical analysis. These include ROA signal enhancement, e.g., recorded for amyloid fibrils or achiral linker aggregates attached to silver colloid (plasmonic effects). Finally, we highlight the challenges faced by ROA studies of supramolecular aggregates of strongly absorbing compounds, where chirality transfer may be misinterpreted as artifacts due to the ECD-Raman effect.

Chiral Selectivity between Pd12Ala24 Metal-Organic Cages Containing Endohedral Chiral Ligands and Their Chiral Counterions

A chiral endohedral Pd12Ala24 metal-organic cage (MOC) incorporating enantiomeric tert-butyloxycarbonylalanine (Boc-Ala) ligands is synthesized as a model system of a chiral macrocation containing internal chiral centers away from the surface of the MOC. The endohedral chiral geometry leads to the interaction between these chiral centers inside the MOCs far away from other chiral components such as chiral counterions in solution. The consequence is that the chiral recognition (two MOC enantiomers self-assemble individually in their mixed solution) and chiral discrimination (self-assembly favors one enantiomer over the other) previously observed in the self-assembly of MOCs carrying exohedral chiral centers become weaker or completely disappear in the current MOC solutions, demonstrating that the effective electrostatic interaction in a short range is critical for the chiral recognition behavior of macromolecules during their self-assembly. Different small chiral species in solution (e.g., arabinose, lactate, tartrate, and γ-cyclodextrin) show various capabilities on the chiral recognition and discrimination of endohedral Pd12Ala24 MOCs during the self-assembly, based on the size and charge of these species.

Phenol[4]arenes: Excellent Macrocyclic Precursors for Constructing Chiral Porous Organic Cages

The development of new chiral building blocks for constructing complex chiral architectures, such as macrocycles and cages, is both crucial and challenging. Although concave-shaped calixarenes have been established as versatile building blocks for the synthesis of cage compounds, there are no reports on cages constructed from chiral calix[4]arene derivatives. Herein, we present a straightforward and effective method for gram-scale synthesis of a new member of chiral calix[4]arene macrocycle enantiomers, namely, phenol[4]arene (PC[4]A). As a proof of concept, we functionalized these enantiomers into tetraformylphenol[4]arene (PC[4]ACHO) derivatives via the Duff reaction to construct chiral porous organic cages (CPOCs) using polyamine synthons. Specifically, we employ two fluorescent amine synthons, bis(4-aminophenyl)phenylamine and tris(4-aminophenyl)amine, to assemble with PC[4]ACHO enantiomers, resulting in [2 + 4] lantern-shaped and [6 + 8] truncated octahedral CPOCs, respectively. These structures have been unambiguously characterized by single-crystal X-ray diffraction and circular dichroism (CD) spectroscopy. Notably, the [6 + 8] truncated CPOCs exhibit internal diameters of approximately 3.1 nm, a cavity volume of around 5300 Å3, and high specific surface areas of up to 1300 m2 g-1 after desolvation, making them among the largest CPOCs reported. Additionally, investigations into their chiral sensing performance demonstrate that these PC[4]A-based CPOCs enable the enantioselective recognition of amino acids and their derivatives. This work strongly suggests that PC[4]A can serve as an excellent building block for the rational design of chiral materials with practical applications.

Heterochiral Self-Discrimination Driven Dimerization of Polynuclear Gold(I)-Sulfido Complexes with Enhanced Phosphorescence

Decanuclear chiral gold(I) sulfido clusters (SSDP-Au10 and RSDP-Au10) have been assembled by taking advantage of the judiciously selected SDP ligands (SDP = 7,7'-bis(diphenylphosphino)-1,1'-spirobiindane). Interestingly, an achiral heterodimer icosanuclear meso-cluster (mesoSDP-Au20) has been obtained by simply mixing SSDP-Au10 and RSDP-Au10 in a 1:1 ratio. These gold(I) complexes have been found to display intense near-infrared (NIR) luminescence with an emission maximum at around 750 nm in the solid state. The photoluminescence quantum yield (PLQY) of mesoSDP-Au20 in drop-cast solid-state thin film has been found to show a significant enhancement from 8 % in the SSDP-Au10 and RSDP-Au10 to 25 %. In addition, the dimerization process with heterochiral self-discrimination has been found to be sensitive to the solvent polarity and configuration of the diphosphine ligand. This work has provided a platform for the investigation and mechanistic understanding of heterochiral self-sorting and assembly processes.

Designing Chiral Organometallic Nanosheets with Room-Temperature Multiferroicity and Topological Nodes

Two-dimensional (2D) room-temperature chiral multiferroic and magnetic topological materials are essential for constructing functional spintronic devices, yet their number is extremely limited. Here, by using the chiral and polar HPP (HPP = 4-(3-hydroxypyridin-4-yl)pyridin-3-ol) as an organic linker and transition metals (TM = Cr, Mo, W) as nodes, we predict a class of 2D TM(HPP)2 organometallic nanosheets that incorporate homochirality, room-temperature magnetism, ferroelectricity, and topological nodes. The homochirality is introduced by chiral HPP linkers, and the change in structural chirality induces a topological phase transition of Weyl phonons. The room-temperature magnetism arises from the strong d-p spin coupling between TM cations and HPP doublet anions. The ferroelectricity is attributed to the breaking of spatial inversion symmetry in the lattice structure. Additionally, by adjusting the type of TMs, these nanosheets show rich and tunable band structures. Notably, all predicted materials are topologically nontrivial, featuring a quadratic nodal point around the Fermi level.

Chiral synthetic hosts for efficient enantioselective molecular recognition. Design principles and synthetic aspects

Discrimination of enantiomeric substrate molecules is one of the fundamental properties of biological hosts. Replicating enantioselective molecular recognition with synthetic receptors is a topic of interest with implications in diverse applications such as bioinspired enantioselective catalysis, enantiomer separation, or sensing. In this review, five different systems reported in the literature are discussed, and their performance and versatility are analyzed. A recently reported host featuring a flexible scaffold challenges the long-established view that a high degree of preorganization in combination with strongly directional non-covalent interactions is required for efficient enantiodiscrimination. The review is complemented with an analysis of the synthetic effort required for each of the hosts presented.

Chiral Polar Bifunctional Polyimide Enantiomers for Asymmetric Photo- and Piezo-Catalysis

Chiral catalysts for asymmetric catalysis represent a crucial research focus in chemistry and materials science. However, a few cases about chiral-dependent photocatalysts primarily focus on plasmonic noble metals. Particularly, developing chiral nano-catalysts that can be driven by mechanical energy remains in the blank stage. Herein, organic polymer-based enantiomers, chiral polar polyimide (PI) microspheric nano-assembly are synthesized as novel bifunctional catalysts for asymmetric photocatalysis and piezocatalysis. The PI catalyst enantiomers present enantioselectivity towards left- and right-circularly polarized light, demonstrating chiral-dependent H2O2 photoproduction. Interestingly, enantioselectivity of the catalyst reverses under irradiation of different bands, presenting tunability in the interaction between chiral catalysts and circularly polarized light. For the first time, enantioselective piezocatalytic behavior is demonstrated by the chiral polar PI catalysts. They show remarkable chiral preference for asymmetric Diels-Alder reaction and enantioselective conversion of tyrosine substrates under ultrasonic vibration. The findings provide a new perspective into exploring metal-free chiral catalysts and their asymmetric catalysis applications across multiple energy forms.

Temperature-Dependent Left- and Right-Twisted Conformational Changes in 1 : 1 Host-Guest Systems: Theoretical Modeling and Chiroptical Simulations

An efficient strategy for high-performance chiral materials is to design and synthesize host molecules with left- and right- (M- and P-)twisted conformations and to control their twisted conformations. For this, a quantitative analysis is required to describe the chiroptical inversion, chiral transfer, and chiral recognition in the host-guest systems, which is generally performed using circular dichroism (CD) and/or proton nuclear magnetic resonance (1H NMR) spectroscopies. However, the mass-balance model that considers the M- and P-twisted conformations has not yet been established. In this study, we derived the novel equations based on the mass-balance model for the 1 : 1 host-guest systems. Then, we further applied them to analyze the 1 : 1 host-guest systems for the achiral calixarene-based capsule molecule, achiral dimeric zinc porphyrin tweezer molecule, and chiral pillar[5]arene with the chiral and/or achiral guest molecules by using the data obtained from the CD titration, variable temperature CD (VT-CD), and 1H NMR experiments. The thermodynamic parameters (ΔH and ΔS), equilibrium constants (K), and molar CD (Δϵ) in the 1 : 1 host-guest systems could be successfully determined by the theoretical analyses using the derived equations.

Chiral Induction of a Tetrakis(porphyrin) in Various Chiral Solvents

Non-covalent interactions offer an alternative way for developing stimulus-responsive materials such as sensors, machines, and drug-delivery systems. We recently reported that a urethane-equipped tetrakis(porphyrin) forms one-handed helical supramolecular polymers in solution in response to chirality of chiral solvents. Conformational changes in helical sense were detected using circular dichroism (CD) spectroscopy, which showed that the tetrakis(porphyrin) can possibly be used as a sensor for determining the enantiomeric excess of a chiral analyte. Hence, we studied the scope and limitations of the chiral-induction behavior of tetrakis(porphyrin) to deepen the understanding of tetrakis(porphyrin)-based chiral sensing systems. Herein, we report the chiral-induction behavior of tetrakis(porphyrin) in various chiral solvents, which was found to be CD-active in many chiral solvents. Notably, the tetrakis(porphyrin) was CD active in a cryptochiral molecular solvent, which is exciting because the chiralities of acyclic saturated hydrocarbons are hard to sense. Consequently, this study highlights the potential advantages of supramolecular chiral sensors capable of targeting a wide range of analytes, including molecules that are absorption-silent in the UV/vis region, ones devoid of anchoring functional groups, and acyclic, saturated hydrocarbons.

Conformational Switching of a Nano-Size Urea-Bridged Zn(II)Porphyrin Dimer by External Stimuli

For the first time, explicit stabilization of all the three conformers, viz. (cis,cis), (cis,trans) and (trans,trans), of a 'nano-sized' highly-flexible urea-bridged Zn(II)porphyrin dimer have been achieved via careful manipulations of external stimuli such as solvent dielectrics, temperature, anionic interactions, axial ligation and surface-induced stabilization. The conformers differ widely in their structures, chemical and photophysical properties and thus have vast potential applicability. X-ray structural characterizations have been reported for the (cis,cis) and (cis,trans)-conformers. While (cis,cis) conformer stabilized exclusively in dichloromethane, more polar solvents resulted in the stabilization of (cis,trans) and (trans,trans)-conformers. Low temperature promotes the stabilization of (cis,trans)-conformer while rise in temperature facilitates flipping to the (cis,cis) one. Significantly, exclusive stabilization of the (trans,trans)-isomer has been illustrated using acetate anion which facilitates H-bonding with the two amide linkages of the urea spacer. Remarkably, HOPG surface facilitates stabilization of the energetically challenging (trans,trans)-conformer via CH⋅⋅⋅π and π⋅⋅⋅π interactions with the solid surface to the porphyrinic cores. DFT calculations demonstrate that the relative stability of the conformers can be modulated upon slight external perturbations as also observed in the experiment. Several factors contributing towards the conformational landscape for the highly flexible urea-bridged porphyrin dimers have been mapped.

Detection of VOCs and Biogenic Amines Through Luminescent Zn-Salen Complex-Tethered Pyrenyl Arms

Amines are produced through various industrial and biological processes, contributing significantly to atmospheric pollution, particularly in the troposphere. Moreover, amine-related pollution raises global concerns due to its detrimental effects on human health, environmental quality, and the preservation of animal species. Low-molecular-weight volatile amines, categorized as volatile organic compounds (VOCs), are present in the atmosphere, and they represent the main cause of air pollution. Biogenic amines, resulting from the natural decarboxylation of amino acids, are released into the environment from both natural and industrial sources. Several methods have been developed so far to detect amines in the environment. In this study, we present a novel fluorescent receptor based on a Zn-Salen complex, functionalized with pyrenyl moieties and a chiral diamine bridge, to enhance its affinity for a broad range of amines. Fluorescence titrations and density functional theory (DFT) calculations reveal and explain the high binding affinity of this receptor toward selected amines, demonstrating its potential as an effective tool for amine detection.

Interplay of Stereochemistry and Charge Governs Guest Binding in Flexible ZnII4L4 Cages

Here, we report the synthesis of a family of chiral ZnII4L4 tetrahedral cages by subcomponent self-assembly. These cages contain a flexible trialdehyde subcomponent that allows them to adopt stereochemically distinct configurations. The incorporation of enantiopure 1-phenylethylamine produced Δ4 and Λ4 enantiopure cages, in contrast to the racemates that resulted from the incorporation of achiral 4-methoxyaniline. The stereochemistry of these ZnII4L4 tetrahedra was characterized by X-ray crystallography and chiroptical spectroscopy. Upon binding the enantiopure natural product podocarpic acid, the ZnII stereocenters of the enantiopure Δ4-ZnII4L4 cage retained their Δ handedness. In contrast, the metal stereocenters of the enantiomeric Λ4-ZnII4L4 cage underwent inversion to a Δ configuration upon encapsulation of the same guest. Insights gained about the stereochemical communication between host and guest enabled the design of a process for acid/base-responsive guest uptake and release, which could be followed by chiroptical spectroscopy.

Supramolecular chiroptical sensing of chiral species based on circularly polarized luminescence

Circularly polarized luminescence (CPL) refers to the differentiation of the left-handed and right-handed emissions of chiral systems in the excited state. Serving as an alternative characterization method to circular dichroism (CD), CPL can detect changes in fluorescence in a chiral system, which could be more efficient in recognizing chiral species. Although CPL can be generated by attaching luminophores to a chiral unit through a covalent bond, the non-covalent bonding of fluorescent chromophores with chiral species or helical nanostructures can also induce CPL and their changes. Thus, CPL can be used as an alternative detection technique for sensing chiral species. In this review, we summarize typical recent advances in chirality sensing based on CPL. The determination of the absolute configuration of chiral compounds and encrypted sensing is also discussed. We hope to provide useful and powerful insights into the construction of chemical sensors based on CPL.

Investigating Nanoscale Interactions of Host-Guest Complexes Formed Between CB[7] and Atenolol by Quantum Chemistry and Ultrasensitive Vibrational Spectroscopy

In addition to the course of over 20 years of cucurbit-7-uril (CB[7]) in the pharmaceutical industry, the present study brings together the most recent observations from the perspective of ultrasensitive Raman spectroscopy and Density Functional Theory (DFT) related to the interaction of this molecule with atenolol (Ate) enantiomers during the formation of these host-guest complexes. Quantum chemistry calculations based on DFT were first used to understand the interaction geometry between CB[7] and Ate. These results were further confirmed by ultrasensitive vibrational spectroscopy. The spectral features associated with each enantiomer in the presence of CB[7] were analyzed by means of SERS, highlighting distinct interaction profiles. These experimental findings validated quantum chemical calculations, offering a comprehensive understanding of the host-guest interactions at the nanoscale level.

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.

High-efficiency detection of primary amine-based chiral molecules by a facile aldimine condensation reaction

Detection of chiral molecules in a high-efficiency way is very important to meet the demands for chiral analysis in drug testing, asymmetric synthesis, etc. Herein, we have developed a novel route to realize the rapid determination of concentration and configuration of primary amine-based chiral molecules. An aldehyde functionalized acid & base-sensitive fluorane dye (R-C) was used as the active agent to be reacted with the chiral molecules through an aldimine condensation reaction. After the mixing operation, concentration and configuration of the detected chiral molecule could be facilely read from the UV-vis absorption spectra and CD spectra, respectively.

Enantio- and Diastereoselective Desymmetrization of 1,1'-Biaryl-2,6-Dicarbaldehydes by Copper-Catalyzed 1,2-Addition of Silicon Nucleophiles

A desymmetrizing 1,2-addition of silicon nucleophiles to biaryl derivatives containing an 2,6-dicarbaldehyde-1-yl unit is reported. The reaction is catalyzed by copper with a triazolium-ion-derived N-heterocyclic carbene as the chiral ligand and makes use of an Si-B reagent as the silicon pronucleophile. The practical methodology furnishes axially chiral aromatic carbaldehydes decorated with a centrally chiral α-hydroxysilane moiety in moderate to good yields and with high enantio- as well as excellent diastereoselectivities. The silicon nucleophile always attacks at the diastereotopic face of either carbonyl group away from the ortho substituent on the phenyl ring at C1 of the 2,6-dicarbaldehyde-1-yl fragment. The resulting axially and centrally chiral products can be further converted into valuable biaryl compounds with hardly any erosion of the enantiomeric excess.

Chirality Interplay between the Interior and Exterior of Metal-Organic Cages

A series of metal-organic cages featuring two stereogenic elements, in terms of the twisting of amide moieties within the ligand backbones and the rotation of diazaanthracene segments along the ligand ridges, were exploited. These two chiral components are correlative and serve as relays for transmitting chirality information between the internal and external cages. The chirality information induced by a chiral guest inside the cage cavity can pass through the cage framework and influence the orientation of the diazaanthracene segments on the periphery of the cage. In turn, the chirality of a stereogenic center within the diazaanthracene segments can transfer back into the cavity, enabling discrimination of enantiomeric guests.

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.

Chirality Sensing of Amino Acid Esters by S-2-Methylbutanamido-Substituted m-Phthalic Diamide-Linked Zinc Bisporphyrinate

To understand the role of an additional coordination site in the linker in chirality sensing, we designed and synthesized an S-2-methylbutanamido-substituted m-phthalic diamide-linked zinc bisporphyrinate, [Zn2(S-MAABis)] and investigated its ability to sense the chirality of amino acid esters. The 1H NMR spectra and the crystal structure showed that the amido oxygen adjacent to the chiral carbon was coordinated with zinc. NMR and UV-vis titration showed that the binding of [Zn2(S-MAABis)] to amino acid esters occurred via two equilibria, forming 1:1 and 1:2 host-guest complexes. The CD spectra suggested that [Zn2(S-MAABis)] can effectively recognize the absolute configuration of amino acid esters. The sign of the CD spectra remained unchanged during the titration, indicating that the corresponding 1:1 and 1:2 host-guest complexes had the same chirality. This is different from previously studied amino-substituted m-phthalic diamide-linked zinc bisporphyrinate [Zn2(AmBis)], which showed chirality inversion during titration. Theoretical calculations indicated that the additional coordination sites (amido or amino) in the 1:1 host-guest complexes played different roles, leading to differences in chirality. Our studies suggest that the introduction of a coordination site can influence the chirality transfer process, but the results of chirality transfers are dependent on the specific binding modes.

Enantioselective Synthesis of Heteroatom-Linked Non-Biaryl Atropisomers

Atropisomers hold significant fascination, not only for their prevalence in natural compounds but also for their biological importance and wide-ranging applications as chiral materials, ligands, and organocatalysts. While biaryl and heterobiaryl atropisomers are commonly studied, the enantioselective synthesis of less abundant heteroatom-linked non-biaryl atropisomers presents a formidable challenge in modern organic synthesis. Unlike classical atropisomers, these molecules allow rotation around two bonds, resulting in low barriers to enantiomerization through concerted bond rotations. In recent years the discovery of new configurationally stable rare non-biaryl scaffolds such as aryl amines, aryl ethers and aryl sulfones as well as innovative methodologies to control their configuration have been disclosed in the literature and constitute the topic of this minireview.

Chirality Sensing of Cryptochiral Guests with Prism[n]arenes

Optical chirality sensing has gained significant attention in recent years. Within this field, the quest for stereodynamic chiroptical probes capable of detecting cryptochiral guests presents a formidable challenge. Macrocycles exhibiting planar chirality have emerged as promising candidates for amplifying the chirality of cryptochiral guests. In this study, we demonstrate that the formation of host-guest complexes between cryptochiral molecules and planar chiral prismarenes triggers electronic circular dichroism (ECD) signals via host-guest complexation-induced chirality amplification. The absolute configuration of the most stable chiral macrocyclic host-guest complex has been established by resorting to both exciton model and DFT computations. Furthermore, we demonstrated that this supramolecular chirality sensing system can be employed to determine the enantiomeric composition of scalemic mixtures by measuring the ECD bands intensity. The information described here opens the way for the use of prismarenes as stereodynamic probes for sensing of cryptochiral guests.

Chirality Sensing of Chiral Carboxylic Acids by a Ureido-Linked Zinc Bisporphyrinate

We designed and synthesized a ureido-linked zinc bisporphyrinate [Zn2(UBis)]. CD spectra show that this zinc bisporphyrinate has the ability to sense the chirality of chiral carboxylic acids without derivatization. Our studies suggest that the phenyl ring in the linker forms π-π interactions with porphyrin planes and that the carboxylic acid is coordinated to the zinc in the host-guest complex. DFT calculations show that the bisporphyrin adopts a "Z"-shaped configuration, and that the ureido group forms hydrogen bonds with carboxylic acids. The combination of π-π interactions, coordination interactions and hydrogen bonding interactions leads to the chirality sensing ability of [Zn2(UBis)].

Controlling Chirogenic Effects in Porphyrin Based Supramolecular Systems: Theoretical Analysis Versus Experimental Observations

Electronic circular dichroism (ECD) spectroscopy is a widely employed method for studying chiral analysis, requiring the presence of a chromophore close to a chiral centre. Porphyrinoids are found to be one of the best chromophoric systems serving for this purpose and enabling the application of ECD spectroscopy for chirality determination across diverse classes of organic compounds. Consequently, it is crucial to understand the induction mechanisms of ECD in the porphyrin-based complexes. The present study explores systematically the influence of secondary chromophores, bonded to an achiral zinc porphyrin or to chiral guest molecules, on the B-region of ECD spectra using the time-dependent density functional theory (TD-DFT) calculations. The study analyses the impact of change in both the conformation of achiral porphyrin (host) and change in position and conformation of chiral organic molecule (guest) on the B-band of ECD spectra (energy, intensity, sign of Cotton effect). Finally, conclusions made on model complexes are applied to published experimental data, contributing to a deeper understanding of various factors influencing ECD spectra in chiral systems. In addition, a computer program aimed to help rationalise ECD spectra by visualizing corresponding orbital energies, rotatory strengths, electric and magnetic transition moments, and angles between them, is presented.

Recognition of Amino Acid Salts by Temperature-Dependent Allosteric Binding with Stereodynamic Urea Receptors

Positive homotropic artificial allosteric systems are important for the regulation of cooperativity, selectivity and nonlinear amplification. Stereodynamic homotropic allosteric receptors can transmit and amplify induced chirality by the first ligand binding to axial chirality between two chromophores. We herein report stereodynamic allosteric urea receptors consisting of a rotational shaft as the axial chirality unit, terphenyl units as structural transmission sites and four urea units as binding sites. NMR titration experiments revealed that the receptor can bind two carboxylate guests in a positive homotropic allosteric manner attributed to the inactivation by intramolecular hydrogen-bonding between urea units within the receptor. In addition, the VT-CD spectra observed upon binding of the urea receptor with l- or D-amino acid salts in MeCN showed interesting temperature-dependent Cotton effects, based on the differences of the receptor shaft unit and the guest structure. The successful discrimination of hydrocarbon-based side chains of amino acid salts indicated that the input of chiral and steric information for the guest was amplified as outputs of the Cotton effect and the temperature-dependence of VT-CD spectra through cooperativity of positive allosteric binding.

Emerging potentials of Fe-based nanomaterials for chiral sensing and imaging

Fe-based nanostructures have possessed promising properties that make it suitable for chiral sensing and imaging applications owing to their ultra-small size, non-toxicity, biocompatibility, excellent photostability, tunable fluorescence, and water solubility. This review summarizes the recent research progress in the field of Fe-based nanostructures and places special emphases on their applications in chiral sensing and imaging. The synthetic strategies to prepare the targeted Fe-based structures were also introduced. The chiral sensing and imaging applications of the nanostructures are discussed in details.

Investigating the diastereoselective synthesis of a macrocycle under Curtin-Hammett control

This work sheds new light on the stereoselective synthesis of chiral macrocycles containing twisted aromatic units, valuable π-conjugated materials for recognition, sensing, and optoelectronics. For the first time, we use the Curtin-Hammett principle to investigate a chiral macrocyclisation reaction, revealing the potential for supramolecular π-π interactions to direct the outcome of a dynamic kinetic resolution, favouring the opposite macrocyclic product to that expected under reversible, thermodynamically controlled conditions. Specifically, a dynamic, racemic perylene diimide dye (1 : 1 P : M) is strapped with an enantiopure (S)-1,1'-bi-2-naphthol group (P-BINOL) to form two diastereomeric macrocyclic products, the homochiral macrocycle (PP) and the heterochiral species (PM). We find there is notable selectivity for the PM macrocycle (dr = 4 : 1), which is rationalised by kinetic templation from intramolecular aromatic non-covalent interactions between the P-BINOL π-donor and the M-PDI π-acceptor during the macrocyclisation reaction.

Axially Chiral Organic Semiconductors for Visible-Blind UV-Selective Circularly Polarized Light Detection

Technologies that detect circularly polarized light (CPL), particularly in the UV region, have significant potential for various applications, including bioimaging and optical communication. However, a major challenge in directly sensing CPL arises from the conflicting requirements of planar structures for efficient charge transport and distorted structures for effective interaction with CPL. Here, a novel design of an axially chiral n-type organic semiconductor is presented to surmount the challenge, in which a binaphthyl group results in a high dissymmetry factor at the molecular level, while maintaining excellent electron-transporting characteristics through the naphthalene diimide group. Experimental and computational methods reveal different stacking behaviors in homochiral and heterochiral assemblies, yielding different structures: Nanowires and nanoparticles, respectively. Especially, the homochiral assemblies exhibit effective π-π stacking between naphthalene diimides despite axial chirality. Thus, phototransistors fabricated using enantiomers exhibit a high maximum electron mobility of 0.22 cm2 V-1 s-1 and a detectivity of 3.9 × 1012 Jones, alongside the CPL distinguishing ability with a dissymmetry factor of responsivity of 0.05. Furthermore, the material possesses a wide bandgap, contributing to its excellent visible-blind UV-selective detection. These findings highlight the new strategy for compact CPL detectors, coupled with the demonstration of less-explored n-type and UV region phototransistors.

Synthesis of axially chiral diaryl ethers via NHC-catalyzed atroposelective esterification

Axially chiral diaryl ethers bearing two potential axes find unique applications in bioactive molecules and catalysis. However, only very few catalytic methods have been developed to construct structurally diverse diaryl ethers. We herein describe an NHC-catalyzed atroposelective esterification of prochiral dialdehydes, leading to the construction of enantioenriched axially chiral diaryl ethers. Mechanistic studies indicate that the matched kinetic resolutions play an essential role in the challenging chiral induction of flexible dual-axial chirality by removing minor enantiomers via over-functionalization. This protocol features mild conditions, excellent enantioselectivity, broad substrate scope, and applicability to late-stage functionalization, and provides a modular platform for the synthesis of axially chiral diaryl ethers and their derivatives.

Interactions between achiral porphyrins and a mature miRNA

Recent discoveries have revealed that mature miRNAs could form highly ordered structures similar to aptamers, suggesting diverse functions beyond mRNA recognition and degradation. This study focuses on understanding the secondary structures of human miR-26b-5p (UUCAAGUAAUUCAGGAUAGGU) using circular dichroism (CD) and chiroptical probes; in particular, four achiral porphyrins were utilized to both act as chiroptical probes and influence miRNA thermodynamic stability. Various spectroscopic techniques, including UV-Vis, fluorescence, resonance light scattering (RLS), electronic circular dichroism (ECD), and CD melting, were employed to study their interactions. UV-Vis titration revealed that meso-tetrakis(4-N-methylpyridyl) porphyrin (H2T4) and meso-tetrakis(4-carboxyphenylspermine) porphyrin (H2TCPPSpm4) formed complexes with distinct binding stoichiometries up to 6 : 1 and 3 : 1 ratios, respectively, and these results were supported by RLS and fluorescence, while the zinc(II) derivative porphyrin ZnT4 exhibited a weaker interaction. ZnTCPPSpm4 formed aggregates in PBS with higher organization in the presence of miRNA. CD titrations displayed an induced CD signal in the Soret region for every porphyrin investigated, indicating that they can be used as chiroptical probes for miR-26b-5p. Lastly, CD melting experiments revealed that at a 1 : 1 ratio, porphyrins did not significantly affect miRNA stability, except for H2TCPPSpm4. However, at a 3 : 1 ratio, all porphyrins, except ZnTCPPSpm4, exhibited a strong destabilizing effect on miRNA secondary structures. These findings shed light on the structural versatility of miR-26b-5p and highlight the potential of porphyrins as chiroptical probes and modulators of miRNA stability.

Chirality Induction and Memory of Pillar[4]arene[1]quinone Derivatives in Visible-Light Range

Pillar[4]arene[1]quinone derivatives (PQXs) were synthesized by the oxidation of pillar[5]arenes, which exhibited notable charge transfer (CT) transitions at approximately 485 nm. Successful chiral resolution of two pairs of enantiomeric conformers was achieved. Despite reduced binding affinity, PQXs demonstrated slower racemization kinetics. Visible-light chiroptical induction with a significant dissymmetry factor was attained by complexing PQXs with a chiral guest. The induced enantiomeric excess could be maintained through competitive binding with an achiral guest, offering a promising strategy for chiral sensing and memory.

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

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

NHC-Catalyzed Chemo- and Enantioselective Reaction between Aldehydes and Enals for Access to Axially Chiral Arylaldehydes

A chiral carbene-catalyzed chemo- and enantioselective reaction with racemic biaryl aldehydes and α-bromoenals is developed for access to axially chiral 2-arylbenzaldehydes through atroposelective dynamic kinetic resolution (DKR) processes. This atroposelective DKR strategy can tolerate a broad scope of substrates with diverse functionalities. The axially chiral 2-aryl benzaldehyde products generally afford moderate to good yields and enantioselectivities. The axially chiral molecules afforded from the current approach are variable through simple transformations to afford axially chiral functional molecules with excellent optical purities.

Dynamic Stereochemistry of M8 Pd6 Supramolecular Cages Based on Metal-Center Lability for Differential Chiral Induction, Resolution, and Recognition

A series of isostructural supramolecular cages with a rhombic dodecahedron shape have been assembled with distinct metal-coordination lability (M8 Pd6 -MOC-16, M=Ru2+ , Fe2+ , Ni2+ , Zn2+ ). The chirality transfer between metal centers generally imposes homochirality on individual cages to enable solvent-dependent spontaneous resolution of Δ8 /Λ8 -M8 Pd6 enantiomers; however, their distinguishable stereochemical dynamics manifests differential chiral phenomena governed by the cage stability following the order Ru8 Pd6 >Ni8 Pd6 >Fe8 Pd6 >Zn8 Pd6 . The highly labile Zn centers endow the Zn8 Pd6 cage with conformational flexibility and deformation, enabling intrigue chiral-Δ8 /Λ8 -Zn8 Pd6 to meso-Δ4 Λ4 -Zn8 Pd6 transition induced by anions. The cage stabilization effect differs from inert Ru2+ , metastable Fe2+ /Ni2+ , and labile Zn2+ , resulting in different chiral-guest induction. Strikingly, solvent-mediated host-guest interactions have been revealed for Δ8 /Λ8 -(Ru/Ni/Fe)8 Pd6 cages to discriminate the chiral recognition of the guests with opposite chirality. These results demonstrate a versatile procedure to control the stereochemistry of metal-organic cages based on the dynamic metal centers, thus providing guidance to maneuver cage chirality at a supramolecular level by virtue of the solvent, anion, and guest to benefit practical applications.

Biogenetic Chiral Deep Eutectic Solvents that Produce Self-Assembled Chiroptical Materials

Deep eutectic solvents (DESs) show particular properties compared to ionic liquids and other traditional organic solvents. Controlled synthesis of chiral materials in DESs is unprecedented due to the complex interplays between DESs and solutes. In this work, all bio-derived chiral DESs were prepared using choline chloride or cyclodextrin as hydrogen bonding acceptors and natural chiral acids as donors, which performed as chiral matrices for the rational synthesis of chiroptical materials by taking advantage of the efficient chirality transfer between the DESs and solutes. In a very selective manner, building units with molecular pockets could facilitate strong binding affinity towards chiral acid components of DESs disregarding the presence of competitive hydrogen bonding acceptors. Chirality transfer from DESs to nanoassemblies leads to chirality amplification in the presence of minimal amounts of entrapped chiral acids, thanks to the spontaneous symmetry breaking of solutes during aggregation. This work utilizes chiral DESs to control supramolecular chirality, and illustrates the structural basis for the fabrication of DES-based chiral materials.

Chiroptical Recognition of Carboxylates with Charge-Neutral Double-Stranded Zinc(II) Helicates

Chirality analysis of small molecules for the determination of their enantiopurity is nowadays ruled by streamlined chromatographic methods which utilize chiral stationary phases. Chiroptical probes which rely on host-guest interactions are so far overshadowed by the latter but have the benefit of depending only on common spectroscopic techniques such as CD spectroscopy to distinguish enantiomers and to quantify their ratio. Interest into this receptor-based approach is constantly rising because non-invasive high-throughput screenings with a minimal waste production can be performed. In this study we investigate the possibility to utilize metal-based containers in form of charge-neutral helicates able to recognize anions for this purpose. Key building block of the helicates are triazole units which show rotational freedom and give rise to either a meso-structure or a racemic mixture of the right- and left-handed complex. A chiroptical response of the probe is observed upon recognition of chiral mono- or dicarboxylates and chirality analysis of tartrate is conducted by CD spectroscopy.

Unleashing the power of porphyrin photosensitizers: Illuminating breakthroughs in photodynamic therapy

This comprehensive review provides the current trends and recent developments of porphyrin-based photosensitizers. We discuss their evolution from first-generation to third-generation compounds, including cutting-edge nanoparticle-integrated derivatives, and explores their pivotal role in advancing photodynamic therapy (PDT) for enhanced cancer treatment. Integrating porphyrins with nanoparticles represents a promising avenue, offering improved selectivity, reduced toxicity, and heightened biocompatibility. By elucidating recent breakthroughs, innovative methodologies, and emerging applications, this review provides a panoramic snapshot of the dynamic field, addressing challenges and charting prospects. With a focus on harnessing reactive oxygen species (ROS) through light activation, PDT serves as a minimally invasive therapeutic approach. This article offers a valuable resource for researchers, clinicians, and PDT enthusiasts, highlighting the potential of porphyrin photosensitizers to improve the future of cancer therapy.

Polymer-Enabled Assembly of Au Nanoclusters with Luminescence Enhancement and Macroscopic Chirality

The construction of macroscopic chiral luminescent aggregates with well-defined structures not only contributes to the development of functional materials but also has significant implications for analyzing chiral transfer and amplification in biological systems and self-assembly systems. Meanwhile, achieving water-soluble chiral metal nanoclusters (NCs) with high photoluminescence (PL) intensity through a convenient method remains a challenge. Herein, we reported the enhanced luminescence of gold nanoclusters stabilized by D-/L-penicillamine (D-/L-AuNCs) induced by poly(allylamine hydrochloride) (PAH) through supramolecular self-assembly strategies. FT-IR spectra and zeta potential measurements revealed that supramolecular assembly was driven by the synergistic effect of hydrogen bonds and electrostatic interactions, which effectively limited the intramolecular vibration and rotation of the ligand and reduced nonradiative relaxation, thus improving the luminescence properties of nanoclusters. Interestingly, during the slow solvent evaporation process, chiral entanglement of assemblies was enhanced, forming macroscopic wheat-shaped superstructures. This study enriches the understanding of the self-assembly mechanism of nanoclusters and provides a pathway for constructing NC-based chiroptical materials.

Chiral SPINOL-Based Pt(II) Metallacycles For Immunogenic Cell Death

The incorporation of chirality endows Pt(II)-based metal-organic complexes (MOCs) with unique potentials in several fields such as nonlinear optics and chiral catalysis. However, the exploration of chiral Pt(II) metallacycles in biological responses remains underdeveloped. Herein, we designed and synthesized two chiral Pt(II) metallacycles 1 and 2 via the coordination-driven self-assembly of chiral 1,1'-spirobiindane-7,7'-diol (SPINOL)-derived ligands and cis-Pt(PEt3)2(OTf)2 (90°Pt). Their structures were well characterized by 1H NMR, 31P{1H} NMR, ESI-TOF-MS, and X-ray crystallography, and their photophysical properties were investigated by UV-vis absorption, fluorescence, and circular dichroism (CD) spectroscopies. Then, the antitumor activity of the two chiral metallacycles in vitro was further tested. Complexes 1 and 2 exhibited strong cytotoxicity, especially toward the A549 cells. The destruction of the mitochondrial function, the inhibition of the glutathione (GSH)/glutathione disulfide (GSSG) level, and the inactivation of superoxide dismutase (SOD) induced by complexes 1 and 2 led to the massive accumulation of reactive oxygen species (ROS). The overloaded ROS then triggered apoptotic cell death, and the release of damage-associated molecular patterns (DAMPs) further induced immunogenic cell death (ICD). To the best of our knowledge, this is the first example of Pt(II)-based metallacycles that can induce immunogenic cell death, providing a new strategy for the future design and construction of immune-modulating platinum agents in cancer therapy.

Stereoselective Plasmonic Interaction in Peptide-tethered Photopolymerizable Diacetylenes Doped with Chiral Gold Nanoparticles

Designing polymeric systems with ultra-high optical activity is instrumental in the pursuit of smart artificial chiroptical materials, including the fundamental understanding of structure/property relations. Herein, we report a diacetylene (DA) moiety flanked by chiral D- and L-FF dipeptide methyl esters that exhibits efficient topochemical photopolymerization in the solid phase to furnish polydiacetylene (PDA) with desired control over the chiroptical properties. The doping of the achiral gold nanoparticles provides plasmonic interaction with the PDAs to render asymmetric shape to the circular dichroism bands. With the judicious design of the chiral amino acid ligand appended to the AuNPs, we demonstrate the first example of selective chiral amplification mediated by stereo-structural matching of the polymer-plasmonic AuNP hybrid pairs. Such ordered self-assembly aided by topochemical polymerization in peptide-tethered PDA provides a smart strategy to produce soft responsive materials for applications in chiral photonics.

Supramolecular Chirogenesis in a Sterically Hindered Porphyrin: A Critical Theoretical Analysis

The determination of molecular stereochemistry and absolute configuration is an important part of modern chemistry, pharmacology, and biology. Electronic circular dichroism (ECD) spectroscopy is a widely used tool for chirality assignment, especially with porphyrin macrocycles employed as reporter chromophores. However, the mechanisms of induced ECD in porphyrin complexes are yet to be comprehensively rationalized. In this work, the ECD spectra of a sterically hindered hexa-cationic porphyrin with two camphorsulfonic acids in dichloromethane and chloroform were experimentally measured and computationally analyzed. The influence of geometric factors such as the position of chiral guest molecules, distortion of the porphyrin macrocycle, and orientation of aromatic and non-aromatic peripheral substituents on the ECD spectra was theoretically studied. Various potential pitfalls, such as a lack of significant conformations and accidental agreement of experimental and simulated spectra, are considered and discussed.

Modulation of supramolecular chirality by stepwise axial coordination in a nano-size trizinc(ii)porphyrin trimer

Herein, we report a chiral guest's triggered spring-like contraction and extension motions coupled with unidirectional twisting in a novel flexible and 'nano-size' achiral trizinc(ii)porphyrin trimer host upon step-wise formation of 1 : 1, 1 : 2, and 1 : 4 host-guest supramolecular complexes based on the stoichiometry of the diamine guests for the first time. During these processes, porphyrin CD responses have been induced, inverted, and amplified, and reduced, respectively, in a single molecular framework due to the change in the interporphyrin interactions and helicity. Also, the sign of the CD couplets is just the opposite between R and S substrates which suggests that the chirality is dictated solely by the stereographic projection of the chiral center. Interestingly, the long-range electronic communications between the three porphyrin rings generate trisignate CD signals that provide further information about molecular structures.

Supramolecular glasses with color-tunable circularly polarized afterglow through evaporation-induced self-assembly of chiral metal-organic complexes

The fabrication of chiral molecules into macroscopic systems has many valuable applications, especially in the fields of optical displays, data encryption, information storage, and so on. Here, we design and prepare a serious of supramolecular glasses (SGs) based on Zn-L-Histidine complexes, via an evaporation-induced self-assembly (EISA) strategy. Metal-ligand interactions between the zinc(II) ion and chiral L-Histidine endow the SGs with interesting circularly polarized afterglow (CPA). Multicolored CPA emissions from blue to red with dissymmetry factor as high as 9.5 × 10^-3 and excited-state lifetime up to 356.7 ms are achieved under ambient conditions. Therefore, this work not only communicates the bulk SGs with wide-tunable afterglow and large circular polarization, but also provides an EISA method for the macroscopic self-assembly of chiral metal-organic hybrids toward photonic applications.

Stereoselective Assembly of Hydrogen-Bonded Anionic Cages Dictated by Organophosphate-Based Chiral Nodes

Inspired by the signal transduction function of organophosphates in biological systems, bioactive organophosphates were utilized for the first time as chiral nodes to dictate the stereoselective assembly of hydrogen-bonded anionic cages. Phosphonomycin (antibiotics), tenofovir (antivirals), adenosine monophosphate (natural product, AMP) and clindamycin phosphate (antibiotics) were assembled with an achiral bis-monourea ligand, thereby leading to the stereoselective formation of quadruple or triple helicates. The extent of the stereoselectivity could be enhanced by either lowering the temperature or adding stronger-binding cations as templates. With the chiral anionic cages as the host, some enantioselectivity was achieved when binding chiral quaternary ammonium cations.