Chiral Group Research Articles

Highly Enantioselective Transportation Across Liquid Membranes Mediated by Porous Covalent Organic Frameworks.

Chiral liquid membrane separation is crucial in pharmaceuticals and chemical synthesis for its simplicity and stability, yet designing membrane carriers that enable efficient enantioseparation remains a challenge. Here, we demonstrated for the first time that chiral porous materials can act as mobile carriers of bulk liquid membranes (BLMs) to enhance enantioselective transport and separation. We design and prepare three 2D chiral covalent organic frameworks (CCOFs) by imine condensations of a chiral dialdehyde with triamines containing ethyl, fluorine and/or isopropyl groups. These isostructural CCOFs feature ABC stacking, excellent water, acid and base tolerance, and chiral amine groups in 1D porous channels, promoting efficient enantioselective transportation of amino acid enantiomers. Among them, the CCOF with both -F and -iPr groups showing superior transport performance. Exfoliating the CCOF into chiral nanosheets creates flexible layers with accessible active sites, enabling nanosheet-mediated liquid membranes to separate chiral drug enantiomers, a feat unattainable with the pristine CCOF. This work establishes CCOFs as a promising platform for chiral BLM separations and will guide the design of high-performance BLMs using porous materials for enantioselective separation.

Highly Enantioselective Transportation Across Liquid Membranes Mediated by Porous Covalent Organic Frameworks

Chiral liquid membrane separation is crucial in pharmaceuticals and chemical synthesis for its simplicity and stability, yet designing membrane carriers that enable efficient enantioseparation remains a challenge. Here, we demonstrated for the first time that chiral porous materials can act as mobile carriers of bulk liquid membranes (BLMs) to enhance enantioselective transport and separation. We design and prepare three 2D chiral covalent organic frameworks (CCOFs) by imine condensations of a chiral dialdehyde with triamines containing ethyl, fluorine and/or isopropyl groups. These isostructural CCOFs feature ABC stacking, excellent water, acid and base tolerance, and chiral amine groups in 1D porous channels, promoting efficient enantioselective transportation of amino acid enantiomers. Among them, the CCOF with both ‐F and ‐iPr groups showing superior transport performance. Exfoliating the CCOF into chiral nanosheets creates flexible layers with accessible active sites, enabling nanosheet‐mediated liquid membranes to separate chiral drug enantiomers, a feat unattainable with the pristine CCOF. This work establishes CCOFs as a promising platform for chiral BLM separations and will guide the design of high‐performance BLMs using porous materials for enantioselective separation.

Phonon-Induced Geometric Chirality.

Chiral properties have seen increasing use in recent years, leading to the emerging fields of chiral quantum optics, plasmonics, and phononics. While these fields have achieved manipulation of the chirality of light and lattice vibrations, controlling the chirality of materials on demand has yet remained elusive. Here, we demonstrate that linearly polarized phonons can be used to induce geometric chirality in achiral crystals when excited with an ultrashort laser pulse. We show that nonlinear phonon coupling quasistatically displaces the crystal structure along phonon modes that reduce the symmetry of the lattice to that of a chiral point group corresponding to a chiral crystal. By reorienting the polarization of the laser pulse, the two enantiomers can be induced selectively. Therefore, geometric chiral phonons enable the light-induced creation of chiral crystal structures and therefore the engineering of chiral electronic states and optical properties.

RE(HSeO3)(SeO3)(H2O)·(H2O) (RE = Y, Gd): Two Rare-Earth Selenite Nonlinear Optical Crystals with Wide Band Gaps.

The band gap is one of the significant parameters for nonlinear optical (NLO) materials, which is the key factor in their application band in laser technology. This study reports the synthesis of two rare-earth selenite NLO crystals, namely, RE(HSeO3)(SeO3)(H2O)·(H2O) (RE = Y, Gd), utilizing the hydrothermal technique. The two compounds are isostructural, and both belong to the orthorhombic chiral space group of P212121 and possess three-dimensional structures consisting of two-dimensional rare-earth selenite layers connected by hydrogen bonds (O-H··O). These two compounds exhibit a moderate second harmonic generation intensity of 0.5/0.8 × KDP and wide energy band gaps reaching 4.8 eV. Comprehensive density functional theory analyses based on first-principles were carried out to unravel the relationship between the structural and corresponding properties. This work provides an approach for band gap enlargement in rare-earth selenite systems and is beneficial to the design of future NLO materials.

CFT Correlators and Mapping Class Group Averages

Mapping class group averages appear in the study of 3D gravity partition functions. In this paper, we work with 3D topological field theories to establish a bulk-boundary correspondence between such averages and correlators of 2D rational CFTs whose chiral mapping class group representations are irreducible and satisfy a finiteness property. We show that Ising-type modular fusion categories satisfy these properties on surfaces with or without field insertions, extending results in [1], and we comment on the absence of invertible global symmetries in the examples we consider.

Spontaneous reversal of spin chirality and competing phases in the topological magnet EuAl4

AbstractMaterials exhibiting a spontaneous reversal of spin chirality have the potential to drive the widespread adoption of chiral magnets in spintronic devices. Unlike the majority of chiral magnets that require the application of an external field to reverse the spin chirality, we observe the spin chirality to spontaneously reverse in the topological magnet EuAl4. Using resonant elastic x-ray scattering we demonstrate that all four magnetic phases in EuAl4 are single-k, where the first two magnetic phases are characterized by spin density wave order and the last two by helical spin order. A single spin chirality was stabilised across the 1mm2 sample, and the reversal of spin chirality occurred whilst maintaining a helical magnetic structure. At the onset of the helical magnetism, the crystal symmetry lowers to a chiral monoclinic space group, explaining the asymmetry in the chiral spin order, and establishing a mechanism by which the spin chirality could reverse via magnetostructural coupling.

(1R,2S,4aR,6S,8R,8aS)-1-(3-Hy-droxy-propano-yl)-1,3,6,8-tetra-methyl-1,2,4a,5,6,7,8,8a-octa-hydronaphthalene-2-carb-oxy-lic acid.

The mol-ecular structure of C18H28O4, (+)-diplodiatoxin, is described, whereby the absolute configuration of the structure of diplodiatoxin has been confirmed by single-crystal X-ray diffraction. Diplodiatoxin crystallizes in the chiral P43212 space group with one mol-ecule in the asymmetric unit.

Phase Transition of a Chiral Lead‐Free Hybrid Antimony(III) Halide Crystal

AbstractChiral organic–inorganic hybrid lead halides have recently attracted great attention due to their unique chirality and diverse functional properties. However, they suffer from highly toxic lead, while lead‐free chiral hybrid metal halides especially those with phase transitions remain sparse. Here, we report a new lead‐free chiral metal halide crystal [R‐3‐fluoropiperidinium]2SbCl5 ([R‐3‐FPP]2SbCl5), which crystalizes in chiral P212121 space group at 293 K and consists of chiral [3‐FPP]+ cations and one‐dimensional [SbCl5]n2− zigzag chains of corner‐sharing SbCl6 octahedrons. Notably, [R‐3‐FPP]2SbCl5 undergoes an above room temperature phase transition at 313 K, which can be attributed to the order‐disorder transition of both the organic [R‐3‐FPP]+ cation and inorganic [SbCl5]2− anions. In addition, [R‐3‐FPP]2SbCl5 also shows a broad band gap of 3.21 eV. This work promotes the exploration of chiral lead‐free hybrid lead halides with phase transitions.

Sn4+ Alloying and Chiral Incorporation into Tellurium Halides Triggering Tunable Luminescence Emission and Second-Harmonic Generation.

Recently, chiral organic-inorganic hybrid metal halides have attracted considerable interest as promising multifunctional materials, benefiting from their diverse structures and tunable photophysical properties. Herein, by introducing the chiral ligand methylbenzylamine (R-/S-MBA) and alloying Sn4+ cation, a series of tellurium-based halides R-/S-MBA2SnxTe1-xCl6 (x = 0, 0.125, 0.2, 0.365 and 0.54) with second-harmonic generation (SHG) effect and photoluminescence (PL) properties are successfully synthesized. Their optical bandgaps are determined to be 2.48-2.6 eV. Specifically, the introduction of chiral organic cations could break the structural symmetry and cause the tellurium halide to crystallize in the chiral space group. The incorporation of isovalent Sn4+ into the chiral host tellurium halides results in the increase in octahedral distortion, thereby promoting host intrinsic self-trapped emission that originates from the interconfigurational 3P0,1 → 1S0 transitions of Te4+. Consequently, the as-prepared Sn4+ doped halides, R-/S-MBA2SnxTe1-xCl6 (x = 0.365, 0.54), exhibit not only SHG response but also bright orange fluorescence. This study provides an effective strategy for designing chiral multifunctional materials.

Novel AIE liquid crystals with high CPL-active bearing multiple dodecyl/cholesterol-decorated R-BINOL-cyanostilbene

The well-structured circularly polarized luminescence (CPL) active liquid crystal materials (R-BINC-Al and R-BINC-Ch) were synthesized through Suzuki coupling of the R-binaphthyl-cyanostilbene unit, followed by modification with dodecyl chains or cholesterol groups. The influence of chiral sources on the liquid crystal behavior, optical properties, and chiroptical response of R-BINC-Al and R-BINC-Ch was thoroughly investigated. Such results revealed that both molecules exhibited typical aggregation-induced emission (AIE) properties and strong solid-state fluorescence. Concretely, the quantum efficiency (ΦF) values of samples with multiple chiral sources increased from 46 % to 51 % by forming liquid crystals in the smectic C and cholesteric phases, the chirality can be transferred to the cyanostilbene unit through ordered self-assembly in the mesophase, resulting in a significant CPL signal across the molecules. Rightfully, the dissymmetry factor (glum) was increased from -7.92 × 10–3 to -1.53 × 10–2 with the introduction of chiral cholesteryl groups. our work elucidated the relationship between multiple chiral sources and CPL behavior, offering a systematic approach to designing chiral luminescent materials in the liquid-crystal phase with high ΦF and substantial glum values, providing a theoretical framework for potential applications in optoelectronic devices.

Chiral Ca–Mn-frameworks with double helical chains and one-dimensional channels constructed from enantiomorphous lactate synthons

Under solvothermal synthetic condition, lactate derivatives (R)-5-(1- carboxyethoxy)isophthalic acid ((R)-H3CIA) and (S)-5-(1-carboxyethoxy)isophthalic acid ((S)–H3CIA) assembled with Ca(Ⅱ) and Mn(Ⅱ) ions to obtain enantiomers {[MnCa0.5((R)-CIA)(H2O)]·((CH3)2NH2CH3CO2)0.5(H2O)}n (HU21-R) and {[MnCa0.5((S)-CIA)(H2O)]·((CH3)2NH2CH3CO2)0.5(H2O)}n (HU21–S), respectively. Complexes HU21-R and HU21–S belong to orthorhombic crystal system with chiral space group I212121. Single crystal X-ray diffraction analysis revealed that all oxygen atoms of synthons (R)-CIA3- and (S)-CIA3- participated in the coordination with metal ions. Thus, semi-rigid (R)-CIA3- and (S)-CIA3- anions become rigid linkers in HU21-R and HU21–S. Fragments of (R)-CIA3- anion are connected by Ca(Ⅱ) ions to build right-handed double helical chains in HU21-R, while the enantiomeric left-handed double helixes are constructed by (S)-CIA3- fragments and Ca(Ⅱ) ions in HU21–S. Additionally, Mn(Ⅱ) centers and CIA3− anions resulted in a rare 4,4,4-connected net with point symbol of (42.62.82)3(42.64). Ca(Ⅱ) ions were further filed into Mn-CIA-framework to form a three dimensional structure with one dimensional channel. Moreover, magnetic test indicates that the framework has a canted antiferromagnetic behavior.

Highly efficient chiral extraction of amino acid enantiomers using Wei-Phos-Pd as chiral extractant

The development of novel and highly efficient chiral extractants has always been a research hotspot in the field of chiral extraction. In this work, Wei-Phos, an adaptive chiral sulfinamide phosphine ligand featuring multiple coordination centers, was employed as a chiral extractant to separate amino acid enantiomers. The influences of metal precursors, organic solvents, pH of the aqueous phase, extractant concentrations, and extraction temperature on enantioselectivities were investigated. The results show that Wei-Phos-Pd is a highly efficient chiral extractant for amino acid enantiomers. D-amino acids are preferentially recognized by Wei-Phos-Pd. The separation factors for phenylalanine (Phe), homophenylalanine (Hph), 3-chlorophenylglycine (3-Cl-Phg), and 4-nitro-phenylalanine (4-NO2-Phe) are 12.19, 8.89, 13.17 and 7.06, respectively. The structure–activity study and recognition mechanism analysis indicate that the chiral tert-butylsulfinamide group and diphosphine structure in Wei-Phos have significant influences on enantioselectivities. The multiple coordination centers account for the high enantioselectivities of Wei-Phos. Wei-Phos-Pd stands out as the most efficient and versatile chiral diphosphine-metal extractant for chiral extraction of amino acids to date.

Photoactive Porphyrin-Based Covalent Organic Frameworks for Photocatalytic Applications

The incorporation of porphyrin units into covalent organic frameworks (COFs) brings new photoelectrochemical properties to the resulted systems. We have developed a bottom-up strategy to prepare a series of tailor-made chiral COFs. The porphyrin subunits act as antennae to harvest visible light. Meanwhile, various secondary amine-based chiral functional groups are immobilized on the pore walls of COFs as catalytic sites. As a result, the COFs that are elaborately designed to merge photoactive building blocks and chiral catalytic sites achieve high production yields with good enantiomeric excess in photocatalytic asymmetric alkylation of aldehydes. In further studies, we have also prepared isostructural porphyrin-based COFs with high crystallinity and porosity, and investigated their photocatalytic N2 fixation performance. The porphyrin building blocks act as not only light-harvesting antennae, but also docking sites for anchoring Au single atoms. Moreover, the microenvironment of Au sites and optoelectronic properties of photocatalysts could be finely tuned by designing the functional groups on proximal and distal position of porphyrin units. The structure-activity relationship has been studied in detail by combining experimental results and theoretical calculations. The introduction of electron-withdrawing groups facilitates the separation and transportation of photogenerated electrons within the entire framework, thus promoting the adsorption of N2 on Au sites for achieving high performance of N2 conversion into NH3.

Bile Acid-conjugate as a Promising Anticancer Agent: Recent Progress.

Bile acids have outstanding chemistry due to their amphiphilic nature and have received a lot of interest in the last few decades in the fields of biomedicine, pharmacology, and supramolecular applications. Bile acids are highly sought after by scientists looking for diverse and effective biological activity due to their chirality, rigidity, and hydroxyl group. The hydroxyl group makes it simple to alter the structure in a way that improves bioactivity and bioavailability. Bile acid-bioactive molecule conjugates are compounds in which a bile acid is linked to a bioactive molecule by a linker in order to increase the bioactivity of the bioactive molecule against the target cancer cells. This method has been used to improve the therapeutic efficacy of cytotoxic drugs while reducing their adverse side effects. These new bile acid conjugates are gaining attention because they overcome bioavailability and stability issues. The design, synthesis, and anticancer effectiveness of various bile acid conjugates are discussed together with recent advances in understanding in this review.

Two Different Chiral Groups Based Thermally Activated Delayed Fluorescence Materials for Circularly Polarized OLEDs.

Circularly polarized organic light-emitting diodes (CP-OLEDs) hold significant promise for applications in 3D displays due to the ability to generate circularly polarized luminescence (CPL) directly. In this study, two pairs of circularly polarized thermally activated delayed fluorescence (CP-TADF) enantiomers, named RR/SS-ONCN and RS/SR-ONCN, were synthesized by integrating two distinct chiral groups into the dicyanobenzene unit. The RR/SS-ONCN and RS/SR-ONCN enantiomers show CPL properties with dissymmetry photoluminescence factors (|gPL|) of 1.3×10-3 and 2.0×10-3 in doped films, respectively. Notably, RR/SS-ONCN exhibit higher |gPL| values than that of RS/SR-ONCN, especially in doped films, indicating that when the configurations of the two chiral groups are identical, the |gPL| value of the CP-TADF materials can be enhanced, demonstrating a certain stacking effect. Moreover, the corresponding CP-OLEDs demonstrate good performances, achieving maximum external quantum efficiencies of up to 21.9 % and notable CP electroluminescence with |gEL| factors of up to 1.0×10-3.

The First Chiral Homology Group

The First Chiral Homology Group

Chiral Star-Shaped [CoIII3LnIII] Clusters with Enantiopure Schiff Bases: Synthesis, Structure, and Magnetism.

Two enantiomeric pairs of new 3d-4f heterometallic clusters have been synthesized from two enantiomer Schiff base derivatives: (R/S)-2-[(2-hydroxy-1-phenylethylimino)methyl] phenol (R-/S-H2L). The formulae of the series clusters are Co3Ln(R-L)6 (Ln = Dy (1R), Gd (2R)), Co3Ln (S-L)6 (Ln = Dy (1S), Gd (2S)), whose crystal structures and magnetic properties have been characterized. Structural analysis indicated that the above clusters crystallize in the chiral P213 group space. The central lanthanide ion has a coordination geometry of D3 surrounded by three [CoIII(L)2]- anions using six aliphatic oxygen atoms of L2- featuring a star-shaped [CoIII3LnIII] configuration. Magnetic measurements showed the presence of slow magnetic relaxation with an effective energy barrier of 22.33 K in the DyIII derivatives under a zero-dc field. Furthermore, the circular dichroism (CD) spectra of 1R and 1S confirmed their enantiomeric nature.

Synthesis of a symmetrically meta-substituted poly(diphenylacetylene) bearing chiral amide groups and its application as a chiral stationary phase for high-performance liquid chromatography

Abstract A symmetrically meta-substituted poly(diphenylacetylene) bearing chiral amide groups was synthesized by reacting (R)-1-phenylethylamine with a carboxy-group-containing precursor polymer, which was obtained by polymerizing the corresponding ester-containing diphenylacetylene using a modified Mo(V)-based catalytic system followed by hydrolysis. The polymer formed a one-handed helical conformation when thermally annealed in a solvent. The chiral recognition ability of the polymer before and after thermal annealing was investigated when used as a chiral stationary phase for high-performance liquid chromatography.

Chiral photoelectron spectroscopy using unpolarized light

This Letter studies the symmetry properties of general vector correlations resulting from one-photon excitation of chiral molecules. We show that the parity-odd second rank tensor is nonzero for molecules in all chiral point groups Cn, Dn, T, O, and I. This chirality-sensitive tensor is nonzero even for chiral isotopomers excited by linearly polarized or even unpolarized light. We develop an irreducible tensor theory based on Curie's limiting groups. As an example of vector correlations, recoil-frame photoelectron angular distributions (RFPADs) are calculated for methyloxirane and CHFCl35Cl37. The difference in the RFPAD between a chiral molecule and its mirror image reaches ±35% of the maximum value for the RFPAD for unpolarized light and ±55% of the value for linearly polarized light. Chiral sensitivity in vector correlation is a quite general phenomenon arising from one-photon excitation by unpolarized and linearly polarized light, and we expect it to be of great importance in time-resolved spectroscopy of ultrafast chemical reactions. Published by the American Physical Society 2024

Synthesis of a New Class of β-Carbonyl Selenides Functionalized with Ester Groups with Antioxidant and Anticancer Properties-Part II.

A series of phenyl β-carbonyl selenides with o-ester functionality substituted on the oxygen atom with chiral and achiral alkyl groups was synthesized. All compounds are the first examples of this type of organoselenium derivatives with an ester substituent in the ortho position. The obtained derivatives were tested as antioxidants and anticancer agents to see the influence of an ester functionality on the bioactivity of β-carbonyl selenides by replacing the o-amide group with an o-ester group. The best results as an antioxidant agent were observed for O-((1R,2S,5R)-(-)-2-isopropyl-5-methylcyclohexyl)-2-((2-oxopropyl)selanyl)benzoate. The most cytotoxic derivative against breast cancer MCF-7 cell lines was O-(methyl)-2-((2-oxopropyl)selanyl)benzoate and against human promyelocytic leukemia HL-60 was O-(2-pentyl)-2-((2-oxopropyl)selanyl)benzoate.