Search Results (582)

4,8,12-Trioxaphosphangulene is a bowl-shaped phosphorus-containing π-conjugated molecule whose molecular geometry is highly sensitive to the substituent attached to the phosphorus atom. Herein, we report the synthesis of a new tungsten pentacarbonyl complex of a chiral 4,8,12-trioxaphosphangulene bearing three phenylethynyl groups. The complex was prepared by coordination of the phosphine center to an in situ generated W(CO)₅ fragment and was characterized by multinuclear NMR spectroscopy and elemental analysis. The NMR spectra revealed that the phosphangulene framework retains its threefold symmetry in solution. Comparison of the NMR parameters with those of a previously reported phosphangulene–tungsten complex indicates that incorporation of the phenylethynyl substituents has little effect on either the coordination environment around the phosphorus atom or the phosphine–tungsten interaction. These findings demonstrate that the characteristic bowl-shaped phosphangulene framework is preserved upon tungsten coordination despite π-extension of the molecular framework. Full article

The oxygen reduction reaction (ORR) is the cathode cornerstone of fuel cells and metal-air batteries. Its inherent spin mismatch between triplet O₂ and singlet products causes sluggish kinetics that conventional catalyst designs cannot fully overcome. This review critically summarizes the past three years’ breakthroughs in spin-regulated ORR electrocatalysis and offers a fresh perspective beyond traditional electronic and geometric optimization. We first dissect the physical mechanism of spin-selective electron transfer required for the 4e⁻ pathway. We then systematically present four strategies for modulating the spin state of transition-metal active sites, namely strain engineering, defect engineering, heteroatom doping, and interfacial heterostructures. Subsequently, we highlight the emerging chirality-induced spin selectivity effect, where chiral organic molecules or intrinsically chiral inorganic materials act as spin filters without an external magnetic field, enabling spin-matched electron transfer and enhanced ORR performance. At the end of our review, we identify several key challenges, including the lack of in situ techniques to dynamically track spin states under operating conditions, the limited stability and universality of chiral catalysts, and the insufficient understanding of synergistic effects between spin control and traditional design parameters. We also outline future research directions, such as developing operando spin characterization, constructing robust chiral inorganic nanostructures, and employing high-throughput computational screening to integrate spin, geometric, and electronic level design. Our review provides a timely and comprehensive framework that bridges spin physics with electrocatalyst design, offering critical mechanistic insights and practical guidelines. Full article

Phenylglycine (Phg) is a nonproteinogenic α-amino acid found in various bioactive molecules. The C-terminal activation of N-acyl Phg is often accompanied by oxazolone-mediated racemization, arising from the direct attachment of the phenyl ring to the α-carbon. After peptide bond formation with another chiral amino acid, this stereochemical erosion is observed as Phg-site epimerization and diastereomer formation. N-acyl activated esters, particularly N-hydroxysuccinimide (OSu) esters, are widely used for peptide bond formation with proteinogenic α-amino acids. Our previous study on N-trifluoroacetyl phenylglycine (TFA-Phg-OH) revealed that Phg-site epimer formation could still occur when TFA-Phg-OSu was employed as an acyl donor for coupling with amino acid ester hydrochlorides (AA–OMe·HCl) in the presence of a soluble organic base. To address these issues, in this study, we report a base-limited one-pot coupling of TFA-Phg-OH with α-amino acid ester hydrochlorides (AA–OR·HCl; R = Me or tert-Bu) using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (WSCD·HCl), which effectively suppresses Phg epimerization. The resulting TFA-Phg–AA–OR dipeptides (AA = Ala, Val, Leu, Met, Phg) were all obtained at a >60% yield with a diastereomeric excess (de) ≥ 98.5%. Notably, reducing the amount of triethylamine further minimized epimer formation, while Ba(OH)₂·8H₂O and trifluoroacetic acid enabled stereoretentive deprotection of the N-TFA group and tert-butyl ester, respectively. This workflow provides practical access to both protected and deprotected Phg–AA motifs, thereby facilitating the preparation of unprotected Phg-containing peptide building blocks. Full article

Accurate estimation of molecule–nanotube interaction energies is critical for the computational screening of carbon-based materials for hydrogen storage; however, density functional theory (DFT) calculations remain computationally expensive for extensive configurational sampling. In this work, we develop a multilayer perceptron (MLP) surrogate model to predict H₂–CNT interaction energies, represented by $E_{ads}$, for H₂ interactions with a chiral (2,1) carbon nanotube. A curated dataset comprising 696 configurations was generated using DMol³ (BIOVIA Materials Studio), varying intermolecular distance, molecular orientation, and interaction site across three regions: internal cavity, edges, and external surface. The proposed MLP architecture (64–32–1) incorporates GELU activation functions, L2 regularization, and dropout to improve generalization. The model achieves coefficients of determination in the range R² = 0.90–0.96 across all interaction regions, with particularly strong performance at the nanotube edges (R² = 0.9358, MSE = 0.046 eV²), as well as on the external surface (R² = 0.9625, MSE = 0.574 eV²) and within the internal cavity (R² = 0.9051, MSE = 1.506 eV²). The original $E_{ads}$ distribution had a mean of 4.0955 eV and a sample standard deviation of 4.3189 eV. The elevated energy values observed in the internal cavity (up to 12 eV) are consistent with steric repulsion induced by geometric confinement rather than predictive artifacts. The trained MLP showed close agreement with DFT-derived trends, enabling exploration of interaction-energy landscapes spanning both attractive and repulsive regimes. These results indicate that MLP-based models trained on diverse configurational datasets provide a computationally efficient alternative for screening carbon nanostructures in hydrogen storage applications, without substantially compromising accuracy relative to first-principles methods. Full article

Single-molecular white circularly polarized luminescence emitters show promise for use in chiral displays and solid-state lighting, but their design remains challenging because broadband emission, exciton utilization, color balance, and chiroptical activity must be integrated within one molecule. Herein, we report a chiral single-molecular white emitter, DCz-PTZ, constructed through a π-interrupted strategy by combining a rigid spiro framework, an oxygen-bridged carbazole/cyanobenzene segment, and a phenothiazine donor. The interrupted conjugation suppresses excessive charge-transfer (CT) domination and enables dual emissive channels, including short-wavelength locally excited (LE) emission and long-wavelength CT emission. DCz-PTZ exhibits near-ideal white emission in dilute toluene solution with CIE coordinates of (0.33, 0.33), and maintains balanced dual emission in 5 wt% doped films with CIE coordinates of (0.32, 0.34). Photophysical studies support the assignment of the yellow emission to a thermally activated delayed fluorescence (TADF)-active CT state. The enantiomers show mirror-image circularly polarized signals with |g_lum| up to 2.9 × 10⁻³. Optimized white organic light-emitting diodes (WOLEDs) achieve color rendering index (CRI) up to 92 and a maximum external quantum efficiency (EQE_max) of 1.3%. This work demonstrates a π-interrupted molecular strategy for integrating dual emission, TADF exciton utilization, and circularly polarized electroluminescence (CPEL) in a single chiral emitter. Full article

Life demonstrates remarkable homochirality of its major building blocks: nucleic acids, amino acids, sugars, and phospholipids. Phospholipid bilayer vesicles (liposomes) are formed at the water/air interface from Langmuir layers and contain ribose, a constituent of primordial water. Although the primordial ribose was initially racemic, life, as we know it, is homochiral, with d-ribose and its derivatives as the predominant forms. The phospholipid membrane’s permeability to d-ribose, together with ribose’s interaction with the bilayer’s charged phosphate groups, leads to ribose phosphorylation, yielding d-ribose-5-phosphate. Once inside, the d-ribose-5-phosphate molecules cannot cross the membrane. A similar path also exists for l-ribose, but with a lower rate. Therefore, overall, this process is enantioselective, favoring the buildup of d-ribose over l-ribose. Through liposome fusion, fission, and self-replication, this eventually leads to the Darwinian evolution of these structures and to the conversion of d-ribose-5-phosphate into complex functional molecules, such as ribozymes and RNA, and eventually into DNA, all of which inherit d-ribose’s chirality. Full article

Electron correlation and quantum interference are pivotal in mesoscopic transport. We theoretically study the nonequilibrium transport dynamics of a triangular triple-quantum-dot (TTQD) molecule connected to fermionic reservoirs using the exact hierarchical equations of motion (HEOM) formalism. We demonstrate a counterintuitive transport signature in which the stationary current is significantly enhanced by increasing U, a behavior distinct from the suppression typically observed in linear quantum dot arrays. By analyzing the evolution of spectral functions, we attribute this enhancement to the interplay between Coulomb-interaction-induced energy shifts and quantum interference effects specific to the triangular topology. We also explore how the circulation of chiral currents and electrode coupling strength modulate these interaction effects. Finally, we present a three-dimensional map of the transport current as a function of inter-dot tunneling (t) and Coulomb interaction (U), illustrating their combined effect on the current magnitude and its applications. Full article

The self-assembly of a novel synthesized chiral dipeptide, Boc-p-nitro-L-phenylalanyl-tyrosine, into supramolecular structures is investigated by optical absorption and photoluminescence spectroscopy as well as single crystal X-ray diffraction. The compound is a diphenylalanine derivative belonging to a family of aromatic dipeptides that spontaneously self-organize into nanostructures through molecular recognition. The dipeptide exhibits several step-like peaks in its absorption band, indicative of self-assembly into quantum-confined nanostructures. In contrast, the parent Boc-p-nitro-L-phenylalanine amino acid lacks these features, indicating that the tyrosine residue favors quantum-confined self-assembly. Crystal structure determination reveals distinct packing styles: Boc-p-nitro-L-phenylalanine forms two-dimensional hydrogen-bonded layers, while the related p-nitro-free Boc-L-phenylalanyl-tyrosine dipeptide organizes into a 3D helical columnar architecture, driven by the additional hydrogen-bonding capacity of the peptide bond and tyrosine hydroxyl group, which favors the formation of a channel-type tetragonal architecture network over the planar sheets of the monomer. Furthermore, the introduction of a tyrosine residue into the Boc-p-nitro-L-phenylalanine molecule alters its supramolecular assembly, as the dipeptide Boc-p-nitro-L-phenylalanyl-tyrosine crystallizes as a monohydrate. The water molecule present in the structure acts as a bridge, participating in a hydrogen-bonding network between the tyrosine hydroxyl groups of neighboring columns through intermolecular interactions. Full article

The two-dimensional chiral self-assembly and chiral separation of achiral Ext-TEB molecules on a Bi(111) surface were investigated using low-temperature scanning tunneling microscopy (LT-STM). At low coverage, the molecules self-assembled into chiral clusters. As the coverage increased, a monolayer film with a non-edge-sharing honeycomb structure was formed. This supramolecular structure exhibited organizational chirality, accompanied by chiral separation. Upon annealing, part of the non-edge-sharing honeycomb structure transformed into a close-packed structure, while retaining the organizational chirality, supramolecular chirality, and pronounced chiral separation. Furthermore, applying a higher bias was found to induce a transition in the electronic state of the non-edge-sharing honeycomb structure, converting it into an edge-sharing honeycomb configuration. This study reveals that the chirality of 1,3,5-tris(4-ethynylphenyl) benzene (Ext-TEB) arises from the rotation of the side-chain phenyl rings, which is induced by the rotation of the molecular axis relative to the substrate lattice. This work presents a strategy for the preparation of chiral nanostructures from achiral molecules due to the spontaneous chiral symmetry generation. Full article

Aspartic acid, a non-essential amino acid required for mammalian growth, has long been overlooked as a simple nutrient. It has been revealed that aspartic acid serves as a key node molecule in the tricarboxylic acid cycle and the urea cycle, and possesses biological activities such as antioxidant, anti-inflammatory, immunomodulatory, and lipid metabolism-regulating effects, garnering widespread attention in the medical, food, and animal husbandry industries. Due to its chiral structure, aspartic acid naturally exists in two configurations, L- and D-forms, which exhibit certain differences in function and chemical properties. In animal husbandry, both configurations of aspartic acid have been applied in various animal models, where they have demonstrated roles in promoting growth, alleviating oxidative stress, modulating immune stress, and regulating gut microbial community structure. Therefore, aspartic acid holds promise as a conditionally functional amino acid for application in animal production. This review summarizes the physicochemical properties, metabolic pathways, and transport mechanisms of aspartic acid, outlines its in vitro synthesis methods, elucidates its physiological functions, and comprehensively reviews the current applications of its different configurations in the field of animal husbandry. The aim is to provide a theoretical foundation for the use of aspartic acid as a green, low-cost, and safe conditionally functional amino acid in animal husbandry. Full article

Continuous exposure to environmental stressors necessitates the development of novel, effective, and safe cosmetic active ingredients to preserve the skin’s structural integrity and physiological function. In this context, chiral cosmetic actives have emerged as particularly promising candidates owing to their diverse skincare properties. Notably, stereochemistry can markedly influence biological activity, producing enantiomer- or diastereomer-specific differences in efficacy and safety. Herein, we summarize recent advances in the application of chiral bioactive molecules as cosmetic actives, organizing them according to biological activity. We provide a comprehensive discussion of their mechanistic biological activities, the activity differences arising from distinct stereochemical configurations, current limitations, and future prospects. Full article

Recent advances in chiral analytical chemistry have revealed that fermented and natural foods contain substantial amounts of D-amino acids (D-AAs), the mirror-image counterparts of L-amino acids, leading to their recognition as nutraceutical components with potential health relevance. Although clinical evidence provides only limited support for their therapeutic efficacy, commercial expectations have outpaced scientific validation, and recent safety concerns emphasize the need for critical evaluation. In this review, we integrate findings from food chemistry, microbiology, biochemistry, physiology, and clinical research to provide a critical overview of dietary D-AAs. We examine how dietary exposure, microbial metabolism, host clearance capacity, and redox status collectively shape their context-dependent biological effects. We highlight the mechanistic linkage between D-amino acid oxidase (DAAO)-mediated hydrogen peroxide (H₂O₂) generation and organ-specific vulnerability, thereby clarifying the molecular basis of their “double-edged sword” actions. Within this interdisciplinary framework, we propose that D-AAs function as context-dependent “contronymic” molecules in cellular communication. By distinguishing physiological regulation, experimental modulation, and clinical application, this review aims to support evidence-based nutraceutical strategies and safety assessments that harness the potential benefits of D-AAs while minimizing associated risks. Full article

This study contains a combination of a review and a related individual case study, which discusses the possibility of predicting the success of enantiomers’ optical separation using fractional crystallization of diastereomeric salts. The key idea is to use relatively simple and rapid experimental methods, such as differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD), to construct ternary melting diagrams. These diagrams can be used for visualization and predicting compositional conditions favorable for successful separation. The main limitations are also mentioned, such as the ideal eutectic behavior of components and the need to identify all crystalline phases in the system. For demonstration, three novel studies, attempts in ternary resolution systems of racemic o- and p-chloromandelic acids with chiral 1-cyclohexylethylamine or pregabalin, resulting in either declined or promising aspects for a successful resolution, were completed, and the corresponding individual ternary phase diagrams have been compiled and presented, as well. In addition, indexing and modeling of one of the diastereomeric salts’ unit cells have been successfully carried out by means of powder X-ray diffraction, using the DASH software package. Full article

The induction of chirality to obtain enantiopure products of high synthetic value is of great importance across various scientific fields, particularly in the medical area, as it has been demonstrated that the different enantiomers of drugs interact differently with biological receptors. In this context, asymmetric catalysis focuses on the design of catalysts that are easy to synthesize, capable of efficiently and enantioselectively forming C–C bonds, and suitable for reuse in multiple catalytic processes. This work describes the application of a Pd(II) complex coordinated with the R and S forms of proline in direct Aldol, Morita–Baylis–Hillman, and Heck coupling reactions. The catalytic system efficiently promoted the aldol reaction, achieving yields of 80–95%, excellent diastereoselectivities (1:69 syn/anti), and enantiomeric excesses greater than 99%. From a mechanistic perspective, the formation of a transition state is proposed in which a proline molecule generates an enamine that, upon coordination with the metal center, is stabilized through interaction with the intermediate’s double bond. Moreover, the study of the Morita–Baylis–Hillman and Heck coupling reactions highlights the versatility of this type of catalyst. Full article

The widespread occurrence of pharmaceutical residues in aquatic environments necessitates the development of advanced porous materials for efficient remediation. This study investigates the adsorption mechanisms of ibuprofen and atenolol within the high-silica zeolite Y. Batch adsorption experiments demonstrated significant uptake, with loading capacities of 191.6 mg/g for ibuprofen and 273.0 mg/g for atenolol, confirming the material’s effectiveness. Using a combination of neutron and X-ray powder diffraction, complemented by Rietveld refinement and simulated annealing algorithms, we achieved the exact localization of the guest molecules. While the pristine zeolite maintains cubic symmetry $Fd\overline{3}$, the incorporation of pharmaceutical molecules induces significant residual nuclear density and anisotropic lattice distortions. To accurately model these perturbations, a systematic symmetry reduction to the acentric triclinic space group F1 was implemented. This approach enabled an ab initio refinement of the structure, revealing that drug uptake of each guest is governed by distinct chemical drivers. Ibuprofen is stabilized via steric confinement and long-range dispersive interactions. In contrast, atenolol stability is governed by electrostatic charge compensation within the zeolitic voids. Our results suggest that the final adsorption geometry is dictated by the spatial orientation of functional groups and host–guest proximity rather than molecular chirality. These results provide a microscopic model describing the fundamental host–guest interactions in FAU zeolites. This structural understanding is an essential step towards the potential use of zeolitic materials in environmental remediation and complex guest sequestration. Full article