Chirality Transfer Research Articles

Structure-Guided Approaches for Enhanced Spin-Splitting in Chiral Perovskite.

Hybrid organic-inorganic perovskites with diverse lattice structures and chemical composition provide an ideal material platform for novel functionalization, including chirality transfer. Chiral perovskites combine organic and inorganic sublattices, therefore encoding the structural asymmetry into the electronic structures and giving rise to the spin-splitting effect. From a structural chemistry perspective, the magnitude of the spin-splitting effect crucially depends on the noncovalent and electrostatic interaction within the chiral perovskite, which induces the local site and long-range bulk inversion symmetry breaking. In this regard, we systematically retrospect the structure-property relationships in chiral perovskite. Insight into the rational design of chiral perovskites based on molecular configuration, dimensionality, and chemical composition along with their effects on spin-splitting manifestation is presented. Lastly, challenges in purposeful material design and further integration into chiral perovskite-based spintronic devices are outlined. With an understanding of fundamental chemistry and physics, we believe that this Perspective will propel the application of multifunctional spintronic devices.

Chiral Ni(Ⅱ)-Based coordination polymers with helixes and dinuclear clusters constructed from lactate synthons

Chiral coordination polymers [Ni((R)-ceba) (1,3-dpp) (H2O)0.5] (HU15-R), [Ni((R)-ceba) (1,3-dpp) (H2O)0.5] (HU15–S), [Ni((R)-ceba) (4,4′-dib) (H2O)0.5] (HU16-R) and [Ni((S)-ceba) (4,4′-dib) (H2O)0.5](HU16–S) were prepared from lactate-derived synthons and different N-donor linkers under hydrothermal conditions (H2ceba = 4-(1-carboxyethoxy)benzoic acid, 1,3-dpp = 1,3-di(pyridine-4-yl)propane, 4,4′-dib = 4,4′-di (1H-imidazole-1-yl)-1,1′-biphenyl). Structural analysis confirmed that that all complexes are three-dimensional frameworks containing dinuclear [Ni2(CO2)2(H2O)]2+ clusters. In addition, four types of helical structures were also obtained though chiral transfer and asymmetric induction from chiral synthons among them. (R)-ceba2- anions and Ni(Ⅱ) ions were bridged together to construct right-handed (R)-ceba-Ni chains in HU15-R and HU16-R, while (S)-ceba2- anions were linked by Ni(Ⅱ) ions to build right-handed (S)-ceba-Ni chains in HU15–S and HU16–S. Apart from chiral synthons, achiral linkers 1,3-dpp and 4,4′-dib assembled with Ni(Ⅱ) ions to form single 1,3-dpp-Ni chains in HU15-R and HU15–S and double 4,4′-dib-Ni chains in HU16-R and HU16–S, respectively. Meanwhile, the introductions of N-donor ligands resulted in varied topological structures. HU15-R and HU15–S are 4-connected dia nets, while HU16-R and HU16–S are 8-connected frameworks. Moreover, magnetic experiments indicated that antiferromagnetic interactions exist in these complexes.

Cholesterol-decorated porphyrin with circularly polarized luminescence: Design, synthesis and properties

Porphyrin was an excellent near-infrared dye but its rigid planar structure is not favorable for producing circularly polarized luminescence (CPL) property. Chirality transfer is an effective strategy to realize the CPL emission for achiral fluorescent unit. In this study, porphyrin derivatives with four cholesterol groups and dodecyl groups B4C and B4D were designed and synthesized. B4C and B4D exhibited good near-infrared emission in both solution and aggregated states. The solid film of B4C emitted strong left CPL fluorescence, while this CPL signal in mesomorphic film was stronger and switched to right CPL emission. The fluorescence dissymmetry factor (glum) of B4C was as high as 2.31×10−2. These results suggested the effective chirality transfer from cholesterol units to porphyrin units based on spiral columnar liquid crystalline stacking and the CPL signal of B4C was tunable by temperature, supplying a good way on design and synthesis of CPL material with tunable CPL signal based on achiral dyes.

Enigma of Pyramidal Neurons: Chirality-Centric View on Biological Evolution. Congruence to Molecular, Cellular, Physiological, Cognitive, and Psychological Functions

The mechanism of brain information processing unfolds within spatial and temporal domains inherently linked to the concept of space–time symmetry. Biological evolution, beginning with the prevalent molecular chirality, results in the handedness of human cognitive and psychological functions (the phenomena known as biochirality). The key element in the chain of chirality transfer from the downstream to upstream processes is the pyramidal neuron (PyrN) morphology–function paradigm (archetype). The most apparent landmark of PyrNs is the geometry of the cell soma. However, “why/how PyrN’s soma gains the shape of quasi-tetrahedral symmetry” has never been explicitly articulated. Resolving the above inquiry is only possible based on the broad-view assumption that encoding 3D space requires specific 3D geometry of the neuronal detector and corresponding network. Accordingly, our hypothesis states that if the primary function of PyrNs, at the organism level, is sensory space symmetry perception, then the pyramidal shape of soma is the best evolutionary-selected geometry to support sensory-motor coupling. The biological system’s non-equilibrium (NE) state is fundamentally linked to an asymmetric, non-racemic, steady state of molecular constituents. The chiral theory of pyramidal soma shape conceptually agrees that living systems have evolved as non-equilibrium systems that exchange energy with the environment. The molecular mechanism involved in developing PyrN’s soma is studied in detail. However, the crucial missing element—the reference to the fundamental link between molecular chirality and the function of spatial navigation—is the main obstacle to resolving the question in demand: why did PyrNs’ soma gain the shape of quasi-tetrahedral symmetry?

Optical Activity and Excitonic Characteristics of Chiral CdSe Quantum Dots.

Introduction of chirality to colloidal semiconductor quantum dots (QDs) triggers a chiroptical effect. However, there remains a knowledge gap in the mechanism of chirality transfer and amplification from molecules to QDs. By time-dependent density functional theory calculations combined with a correlated electron-hole picture, we explored the chiroptical activity of CdSe QDs decorated with different chiral monocarboxylic acids from an excitonic perspective. Our calculations showed strong circular dichroism (CD) signals in the visible region for the chiral CdSe QDs. The excitonic states with large CD originate from QDs, while the chiral molecules break the orthogonality between electric and magnetic transition dipoles, which synergistically facilitates the prominent dissymmetric effect. The considered monocarboxylic acid chiral molecules all favor the bidentate adsorption configuration of the carboxyl group on the CdSe surface, endowing an identical CD signature but distinct excitonic characteristics. These findings are crucial for the regulation of chirality and excitons in semiconductor QDs to develop excitonic devices.

Tunable Circularly Polarized Luminescence by Confining Dye Molecules within Chiral Layered Metal–Organic Framework

AbstractCircularly polarized luminescence (CPL) active materials have attracted widespread attention because of their potential applications. Nonetheless, it is still a great challenge to fabricate CPL materials with both high fluorescence quantum efficiency (Φ) and high luminescent asymmetry factor (glum). According to the unique structure characteristics of chiral layered metal–organic frameworks (CLMOFs), herein a novel strategy to construct high‐performance CPL materials, by utilizing the confinement effect of CLMOFs is developed. Conjugate dye molecules, such as fluorescent brighteners, fluorescein, and rhodamine B, which are readily subjected to aggregation‐caused quenching (ACQ) effect, are successfully intercalated into CLMOF matrix, affording blue, yellow–green, and red CPL, respectively. Both high Φ and glum values of up to 91% and 0.069 are obtained, owing to the distinct confinement effect of CLMOFs. After confining dye molecules within CLMOF, the ACQ effect is effectively inhibited, which is beneficial for fluorescence enhancement; simultaneously, the chirality transfer from CLMOF matrix to dyes by controlling their arrangement in the chiral confinement microenvironment, leading to the high glum values. Based on the full‐color and strong CPL, a multi‐dimensional code system is proposed. This work paves a new avenue to design and assemble CPL materials with high Φ and glum, which can be widely adopted.

Three-Dimensional Homochiral Covalent Organic Frameworks with Intrinsic Chiral qzd Topology.

Although a variety of chiral porous framework materials have been reported, there are few examples known to combine molecular chirality, helicity, and three-dimensional (3D) intrinsically chiral topology in one structure, which is beneficial for chirality transfer and amplification. Here, we report the synthesis of the first two 3D covalent organic frameworks (COFs) with an intrinsic chiral qzd topology, which exhibit unusual integration of various homochiral and homohelical features. By imine condensation of 4-connected porphyrin tetraamines and 2-connected enantiopure diene dialdehyde, we prepared two isostructural COFs with a noninterpenetrated qzd topology. The specific geometry and conformation flexibility of the V-shaped diene linker control the alignment of square-planar porphyrin units with rotational linkages and facilitate the creation of homochiral extended porous structures that feature a helical arrangement of porphyrins. Post-synthetic metalation of CCOF 23 with Rh(I) affords a heterogeneous catalyst for the asymmetric Michael addition reaction of aryl boronic acids to 2-cyclohexenone, which shows higher enantioselectivities compared to their homogeneous counterparts, presumably due to the confined effect of helical channels. This finding will provide an impetus to explore multichirality materials, offering new insights into the generation and control of helicity, homochirality, and enantioselectivity in the solid state.

A chiral zeolite material with improved enantioselective catalytic properties prepared from readily accessible ephedrine alkaloids

Substituted-benzyl-containing N-methyl-ephedrinium derivatives (BMEP), prepared from the highly-accessible (1R,2S)- or (1S,2R)-ephedrine alkaloids, have been found to act as efficient structure-directing agents for the synthesis of chiral zeolite GTM-4 with –ITV framework structure, promoting the enantio-enrichment in one of the chiral crystalline polymorphs as a function of the organic handedness. Results of a systematic variation of substituents in the benzyl ring attached to the ephedrine core (with methyl-, fluoro- or chloro-groups in the different positions of the aromatic ring) revealed that F-containing SDAs brought about an improvement in the structure-directing ability toward the –ITV framework, giving asymmetric zeolite acid-catalysts that yielded notable enantiomeric excesses in the range of 40–45 % for the trans-stilbene oxide ring-opening with 1-butanol. Interestingly, the incorporation of a methyl group in ortho-position (oMBMEP) had a double positive effect: on the one hand, this SDA prevented the crystallization of the competing BEC phase, allowing the crystallization of the -ITV structure at higher temperature and with higher crystallinity, and on the other, it drove to GTM-4 asymmetric catalysts that yielded enantiomeric excesses up to 60 %, resulting in the chiral GTM catalysts with the best enantioselective properties found so far. Remarkably, our catalytic results show the same chiral activity (in terms of zeolite handedness) for GTM-4 materials prepared from benzyl-containing (1S,2S)-N-methyl-pseudoephedrinium (BMPS) and (1S,2R)-N-methyl-ephedrinium (BMEP) derivatives, thus suggesting that the host-guest transfer of chirality during crystallization with these chiral organic aromatic agents is imposed by the absolute configuration of the C1 atom to which the OH group is attached. The relatively high enantiomeric excess of 60 % achieved, combined with the high accessibility of the ephedrine chiral precursors used for the synthesis that enables the production of both crystalline handedness of the –ITV framework, bring these materials closer to a potential application as heterogeneous asymmetric catalysts for the synthesis of chiral compounds of interest.

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

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

Symmetry breaking and chiral amplification in prebiotic ligation reactions.

The single chirality of biological molecules is a signature of life. Yet, rationalizing how single chirality emerged remains a challenging goal1. Research has commonly focused on initial symmetry breaking and subsequent enantioenrichment of monomer building blocks-sugars and amino acids-that compose the genetic polymers RNAand DNA as well as peptides. If these building blocks are only partially enantioenriched, however, stalling of chain growth may occur, whimsically termed in the case of nucleic acids as "the problem of original syn"2. Here, in studying a new prebiotically plausible route to proteinogenic peptides3-5, we discovered that the reaction favours heterochiral ligation (that is, the ligation of L monomers with D monomers). Although this finding seems problematic for the prebiotic emergence of homochiral L-peptides, we demonstrate, paradoxically, that this heterochiral preference provides a mechanism for enantioenrichment in homochiral chains. Symmetry breaking, chiral amplification and chirality transfer processes occur for all reactants and products in multicomponent competitive reactions even when only one of the molecules in the complex mixture exhibits an imbalance in enantiomer concentrations (non-racemic). Solubility considerations rationalizefurther chemical purification and enhanced chiral amplification. Experimental data and kinetic modelling support this prebiotically plausible mechanism for the emergence of homochiral biological polymers.

Supramolecular Chiral Binding Affinity-Achieved Efficient Synergistic Cancer Therapy.

Supramolecular chirality-mediated selective interaction among native assemblies is essential for precise disease diagnosis and treatment. Herein, to fully understand the supramolecular chiral binding affinity-achieved therapeutic efficiency, supramolecular chiral nanoparticles (WP5⊃D/L-Arg+DOX+ICG) with the chirality transfer from chiral arginine (D/L-Arg) to water-soluble pillar[5]arene (WP5) are developed through non-covalent interactions, in which an anticancer drug (DOX, doxorubicin hydrochloride) and a photothermal agent (ICG, indocyanine green) are successfully loaded. Interestingly, the WP5⊃D-Arg nanoparticles show 107 folds stronger binding capability toward phospholipid-composed liposomes compared with WP5⊃L-Arg. The enantioselective interaction further triggers the supramolecular chirality-specific drug accumulation in cancer cells. As a consequence, WP5⊃D-Arg+DOX+ICG exhibits extremely enhanced chemo-photothermal synergistic therapeutic efficacy (tumor inhibition rate of 99.4%) than that of WP5⊃L-Arg+DOX+ICG (tumor inhibition rate of 56.4%) under the same condition. This work reveals the breakthrough that supramolecular chiral assemblies can induce surprisingly large difference in cancer therapy, providing strong support for the significance of supramolecular chirality in bio-application.

Chiral silver cluster-based light-harvesting systems: Enantioselective chirality transfer and amplified circularly polarized luminescence

Chiral silver cluster-based light-harvesting systems: Enantioselective chirality transfer and amplified circularly polarized luminescence

Acid-Catalyzed Highly Enantioselective Synthesis of α-Amino Acid Derivatives from Sulfinamides and Alkynes.

An enantioselective difunctionalization of activated alkynes using chiral sulfinamide reagents is developed. It is an atom and chirality transfer process that allows for the modular synthesis of optically active α-amino acid derivatives under mild conditions. The reaction proceeds through an acid-catalyzed [2,3]-sigmatropic rearrangement mechanism with predictable stereochemistry and a broad scope.

Design and Synthesis of Diphosphine Ligands Based on the Chiral Biindolyl Scaffold and Their Application in Transition-Metal Catalysis.

An extremely concise, scalable, and stereoselective synthesis of a privileged chiral skeleton based on 2,2'-biindolyl and commercially available chiral building blocks has been developed. This novel skeleton allows for easy access to a range of bisphosphine ligands (decagram scale, up to 58% total yield, only three steps). The synthetic method is characterized by an efficient central-to-axial chirality transfer strategy. In particular, the superior performance of the ligands has been demonstrated in diverse reactions, including several asymmetric hydrogenations, asymmetric conjugate reductions, and cycloisomerization reactions, indicating a great potential for the application of the newly developed chiral backbones in further modifications and exploration of novel chiral ligands and catalysts.

Asymmetric Molecular Adsorption and Regioselective Bond Cleavage on Chiral PdGa Crystals.

Homogenous enantioselective catalysis is nowadays the cornerstone in the manufacturing of enantiopure substances, but its technological implementation suffers from well-known impediments like the lack of endurable catalysts exhibiting long-term stability. The catalytically active intermetallic compound Palladium-Gallium (PdGa), conserving innate bulk chirality on its surfaces, represent a promising system to study asymmetric chemical reactions by heterogeneous catalysis, with prospective relevance for industrial processes. Here, this work investigates the adsorption of 10,10'-dibromo-9,9'-bianthracene (DBBA) on the PdGa:A( ) Pd3-terminated surface by means of scanning tunneling microscopy (STM) and spectroscopy (STS). A highly enantioselective adsorption of the molecule evolving into a near 100% enantiomeric excess below room temperature is observed. This exceptionally high enantiomeric excess is attributed to temperature activated conversion of the S to the R chiral conformer. Tip-induced bond cleavage of the R conformer shows a very high regioselectivity of the DBBA debromination. The experimental results are interpreted by density functional theory atomistic simulations. This work extends the knowledge of chirality transfer onto the enantioselective adsorption of non-planar molecules and manifests the ensemble effect of PdGa surfaces resulting in robust regioselective debromination.

Integrated Anionic Zirconium-Organic Cage and Cationic Boron-Imidazolate Cage for Synergetic Optical Limiting.

Making oppositely charged metal-organic cages (MOCs) into a tightly ordered structure may bring interesting functions. Herein, we report a novel structure composed of anionic (Zr4 L6 )8- (L=embonate) tetrahedral cages and in situ-formed cationic [Zn4 (Bim)4 ]4+ (Bim=[BH(im)3 ]- ; im=imidazole) cubic cages. Chiral transfer is observed from enantiopure (Zr4 L6 )8- cage to enantiopure [Zn4 (Bim)4 ]4+ cage. A pair of enantiomers (PTC-373(Δ) and PTC-373(Λ)) are formed. PTC-373 exhibits high chemical and thermal stabilities, affording an interesting single-crystal-to-single-crystal transformation. More importantly, the combination of ionic pair cages significantly enhances its third-order nonlinear optical property, and its thin-film exhibits an excellent optical limiting effect.

Integrated Anionic Zirconium‐Organic Cage and Cationic Boron‐Imidazolate Cage for Synergetic Optical Limiting

AbstractMaking oppositely charged metal‐organic cages (MOCs) into a tightly ordered structure may bring interesting functions. Herein, we report a novel structure composed of anionic (Zr4L6)8− (L=embonate) tetrahedral cages and in situ‐formed cationic [Zn4(Bim)4]4+ (Bim=[BH(im)3]−; im=imidazole) cubic cages. Chiral transfer is observed from enantiopure (Zr4L6)8− cage to enantiopure [Zn4(Bim)4]4+ cage. A pair of enantiomers (PTC‐373(Δ) and PTC‐373(Λ)) are formed. PTC‐373 exhibits high chemical and thermal stabilities, affording an interesting single‐crystal‐to‐single‐crystal transformation. More importantly, the combination of ionic pair cages significantly enhances its third‐order nonlinear optical property, and its thin‐film exhibits an excellent optical limiting effect.

Decoding Van der Waals Impact on Chirality Transfer in Perovskite Structures: Density Functional Theory Insights.

Chiral organic-inorganic perovskites exhibit unique physicochemical properties driven by the symmetry of monovalent organic cations. However, an atomistic understanding of how chiral cations transfer their chirality to the inorganic framework and the role played by van der Waals (vdW) interactions in this process is still incomplete. In this work, we report a theoretical investigation, based on density functional theory calculations within the Perdew-Burke-Ernzerhof (PBE) formulation for the exchange-correlation functional, into the role of the vdW interactions in the chirality transfer process. For that, we selected several vdW corrections, namely, Grimme (D2, D3, D3(BJ)), Tkatchenko-Scheffler (TS, TS+SCS, TS+HSI), density-dependent energy correction (dDsC), and many-body scattering (MBD) energy method correction. For the chiral perovskite systems, we selected a set of chiral organic-inorganic perovskites with several dimensions, namely, from zero-dimensional to three-dimensional, each having enantiomers with R and S configurations. Based on a statistical treatment of the relative errors of all lattice parameters with respect to experimental data, we found that D3, D3(BJ), TS, TS+SCS, TS+HSI, and MBD vdW are the most accurate corrections to describe the equilibrium structural properties of chiral perovskites using the PBE method. We identify chirality-induced sequential asymmetries of distorted octahedrons and propose angular descriptors to quantify them, where the orientations of these distortions depend on the R or S nature of the chiral cations. Furthermore, we demonstrate the importance of accurate vdW interactions in precisely describing these asymmetric distortions. By means of binding energies and charge-transfer analysis, we show that the impact of vdW corrections on the charge distribution leads to a subtle strengthening of hydrogen bonds between chiral cations and inorganic octahedra, resulting in an increase in the binding energy. Finally, we identified that the Rashba-Dresselhaus effect in two-dimensionality is refined by vdW interactions.

Induced Absolute Configuration of Achiral Tetradentate Ligands in Metal–Organic Frameworks for Circularly Polarized Luminescence

Comprehensive SummaryThe crystallization of chiral molecules is of great significance to understand the origin and evolution of hierarchical chirality and reveal the relationships between structural chirality and circularly polarized luminescence (CPL) activity. Here, we report two pairs of chiral metal–organic frameworks (MOFs) (DCF‐17/LCF‐17, DCF‐18/LCF‐18) by utilizing tetradentate ligands tetra(3‐imidazoylphenyl)ethylene (TIPE) and 4,4'‐[4',5'‐bis[4‐(4‐pyridinyl)phenyl][1,1':2',1”‐terphenyl]‐4,4”‐diyl]bis[pyridine] (TPPP) as linkers. It can be observed that the spontaneous resolution of the achiral ligands is converted into the induced resolution, and the ligands form the absolute configuration by using enantiopure camphoric acid (cam) as chiral induced reagent (CIR). As a result, the racemate MOFs can be driven to generate absolute homochiral crystallization. Another two achiral MOFs [Cd(D‐cam)(TPPP)0.5] (AF‐1, AF = achiral framework) and [Cd(L‐cam)(TPPP)0.5] (AF‐2) were prepared. The position disorder of D/L‐cam skeleton causes the generation of nonchiralization, further leading to disappearance of symmetry breaking of TPPP. For the perspective of structure, this is the first report which reveals the chiral transfer and nonchiralization between chiral induced agents and tetradentate ligands. Besides, DCF‐17 and LCF‐17 show CPL with luminescence dissymmetry factor (glum) of –1.0 × 10‐2 and +9.2 × 10–3, respectively. This work provides the useful evidences to reveal the induced chiral crystallization and the construction of CPL‐active crystalline materials.

Unraveling the Chirality Transfer from Circularly Polarized Light to Single Plasmonic Nanoparticles

AbstractDue to their broken symmetry, chiral plasmonic nanostructures have unique optical properties and numerous applications. However, there is still a lack of comprehension regarding how chirality transfer occurs between circularly polarized light (CPL) and these structures. Here, we thoroughly investigate the plasmon‐assisted growth of chiral nanoparticles from achiral Au nanocubes (AuNCs) via CPL without the involvement of any chiral molecule stimulators. We identify the structural chirality of our synthesized chiral plasmonic nanostructures using circular differential scattering (CDS) spectroscopy, which is correlated with scanning electron microscopy imaging at both the single‐particle and ensemble levels. Theoretical simulations, including hot‐electron surface maps, reveal that the plasmon‐induced chirality transfer is mediated by the asymmetric distribution of hot electrons on achiral AuNCs under CPL excitation. Furthermore, we shed light on how this plasmon‐induced chirality transfer can also be utilized for chiral growth in bimetallic systems, such as Ag or Pd on AuNCs. The results presented here uncover fundamental aspects of chiral light‐matter interaction and have implications for the future design and optimization of chiral sensors and chiral catalysis, among others.