Search Results (138)

Tailoring the chirality of an optical vortex is crucial for advancing helical chiroptical spectroscopy techniques in various scenarios and attracts great attention. In contrast to the single vortex, the optical vortex pair exhibits richer, fantastic chirality properties due to its additional adjustment parameters. Here, a comprehensive investigation of the chirality for linearly polarized optical vortex pairs based on the vector angular spectrum decomposition method is conducted. The numerical results show that the magnitudes and distributions of local chirality density, helical dichroism, and enantioselective force of the optical vortex pair can be flexibly customized by the position as well as sign combination of vortices, and can vary during free space propagation. The underlying physical mechanism behind these phenomena is ascribed to the interplay of two vortices. Our work can deepen the understanding of the chirality for multiple vortices and open-up the prospect for relevant applications in chiral recognition and manipulation. Full article

In this study, three alternating donor–acceptor (D–A) type [12]cycloparaphenylene ([12]CPP) derivatives ([12]CPP 1a, 2a, and 3a) were designed through precise molecular engineering, and their multidimensional photophysical responses and chiroptical properties were systematically investigated. The effects of the alternating D–A architecture on electronic structure, excited-state dynamics, and optical behavior were elucidated through density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. The results show that the alternating D–A design significantly reduced the HOMO–LUMO energy gap (e.g., 3.11 eV for [12]CPP 2a), enhanced charge transfer characteristics, and induced pronounced red-shifted absorption. The introduction of an imide-based acceptor ([12]CPP 2a) further strengthened the electron push-pull interaction, exhibiting superior performance in two-photon absorption, while the symmetrically multifunctionalized structure ([12]CPP 3a) predominantly exhibited localized excitation with the highest absorption intensity but lacked charge transfer features. Chiral analysis reveals that the alternating D–A architecture modulated the distribution of chiral signals, with [12]CPP 1a displaying a strong Cotton effect in the low-wavelength region. These findings not only provide a theoretical basis for the molecular design of functionalized CPP derivatives, but also lay a solid theoretical foundation for expanding their application potential in optoelectronic devices and chiral functional materials. Full article

Background/Objective: Avapritinib is an orally bioavailable tyrosine kinase inhibitor and was approved by the FDA in 2020 for gastrointestinal stromal tumor treatments. Although avapritinib is known to be chiral, its stereochemistry was initially established randomly. This study aims to develop a definitive method for determining avapritinib’s absolute configuration and propose a universal methodology for stereochemical characterization of flexible chiral drugs. Methods: The absolute configuration of avapritinib was determined through an integrated approach combining chiral resolution, chiroptical spectroscopy and synthetic validation. Enantiomeric separation was achieved via chiral liquid chromatography, followed by comprehensive chiroptical characterization including electronic circular dichroism (ECD), specific optical rotation and optical rotatory dispersion. Conformational analysis and density functional theory (DFT) calculations correlated experimental spectra with theoretical predictions, facilitating definitive configurational assignment. The stereochemical determination were further verified through ECD derivatization and chemical synthesis. Finally, the enantiomers’ kinase inhibition profiles against c-KIT D816V were quantitatively assessed. Results: Two enantiomers of avapritinib were resolved via chiral HPLC and a Chiralpak IG column. Through combined experimental ECD spectra and time-dependent DFT calculations employing the core extraction method, the levo-isomer was unambiguously determined as S configuration. This stereochemical assignment was confirmed by p-cyanobenzaldehyde derivatization and de novo synthesis. Biological evaluation revealed (S)-(−)-avapritinib exhibited superior c-KIT D816V inhibitory activity compared to its (R)-(+)-counterpart, a finding corroborated by molecular docking studies elucidating their differential target interactions. Conclusions: This study advances avapritinib stereochemical understanding and establishes a definitive protocol for its absolute configuration assignment, serving as a paradigm for flexible chiral drug characterization. Full article

Seeking a supramolecular chiral system induced by trace chiral molecules instead of traditional complex and expensive chiral ligands to achieve high yield or ee value conversion of the products is of great significance in asymmetric synthesis but still remains a challenge. Herein, two types of double helical supramolecular chiral systems, (M)-Helix and (P)-Helix, with opposite chiral optics were constructed in situ using tyrosine-functionalized pillar[5]arene as inducers. These systems exhibit chiroptical stability and enable remarkable chirality amplification from 7 mol% chiral seeds. When applied to intermolecular olefin cyano-trifluoromethylation, (M)-Helix exhibits remarkable catalytic efficiency (yield up to 89%), whereas (P)-Helix achieves higher enantioselectivity (ee up to 84%). This research will provide new ideas for supramolecular chiral catalysts in organic asymmetric catalysis applications. Full article

Porphyrins are highly conjugated macrocyclic compounds that possess exceptional photophysical and chemical properties, progressively establishing themselves as versatile tools in the structural investigation of biomolecules. This review explores their role as chiroptical conformational probes, focusing on their interactions with DNA and RNA. The planar electron rich structure of porphyrin macrocycle that promote π–π interactions, their easy functionalization at the meso positions, and their capacity to coordinate metal ions enable their use in probing nucleic acid structures with high sensitivity. Emphasis is placed on their induced circular dichroism (ICD) signals in the Soret region, which provide precise diagnostic insights into binding mechanisms and molecular interactions. The review examines the interactions of porphyrins with various DNA structures, including B-, Z-, and A-DNA, single-stranded DNA, and G-quadruplex DNA, as well as less common structures like I-motif and E-motif DNA. The last part highlights recent advancements in the use of porphyrins to probe RNA structures, emphasizing binding behaviors and chiroptical signals observed with RNA G-quadruplexes, as well as the challenges in interpreting ICD signals with other RNA motifs due to their inherent structural complexity. Full article

The analysis of natural and artificial chiral compounds is vital wherever the nuances in the three-dimensional structure are decisive for the possibility of their further use, e.g., as pharmaceuticals or catalysts. The qualitative determination of the structure of a chiral entity requires either an anomalous scattering of X-ray radiation or chiroptical techniques, of which electronic circular dichroism (ECD) is one of the most useful. Chiroptical sensing that uses stereodynamic probes remains one of the remedies for the problem of the lack of a suitable chromophore in the molecules of the chiral compound. A covalent or non-covalent binding of an ECD-silent chiral molecule (the inducer) to the UV-active chromophoric system (chiroptical probe) led to obtaining complex ECD active at a given spectral region. The transfer of structural information from a permanently chiral inducer molecule to the structurally labile chromophoric system of the probe results in adjusting the latter’s structure to the chiral environment. This contribution focuses on some fundamental aspects of chirality sensing using conformationally labile probes. It discusses the mechanism of action of arbitrarily chosen stereodynamic chirality sensors, with particular emphasis on probes based on di- and triarylmethyl derivatives and biphenyl and its congeners. Full article

Vibrational circular dichroism (VCD) enhancement by low-lying electronic states (LLESs) is a fascinating phenomenon, but accounting for it theoretically remains a challenge despite significant research efforts over the past 20 years. In this article, we synthesized two transition metal complexes using the tetradentate Schiff base ligands (R,R)- and (S,S)-N,N′-Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine with Co(II) and Mn(III), referred to as Co(II)-salen-chxn and Mn(III)-Cl-salen-chxn, respectively. Their stereochemical properties were explored through a combined experimental chiroptical spectroscopic and theoretical approach, with a focus on Co(II)-salen-chxn. Extensive conformational searches in CDCl₃ for both high- and low-spin states were carried out and the associated infrared (IR), VCD, ultraviolet-visible (UV-Vis) absorption, and electronic circular dichroism (ECD) spectra were simulated. A good agreement between experimental and simulated data was achieved for IR, VCD, UV-Vis, and ECD, except in the case of VCD of Co(II)-salen-chxn which exhibits significant intensity enhancement and monosignate VCD bands, attributed to the LLESs. Interestingly, detailed comparisons with Mn(III)-Cl-salen-chxn and previously reported Ni(II)-salen-chxn and Cu(II)-salen-chxn complexes suggest that the enhancement factor is predicted by the current density functional theory simulations. However, the monosignate signatures observed in the experimental Co(II) VCD spectrum were not captured theoretically. Based on the experiment and theoretical VCD and ECD comparison, it is tentatively suggested that Co(II)-salen-chxn exists in both low- and high-spin states, with the former being dominant, while Mn(III)-Cl-salen-chxn in the high-spin state. The study indicates that VCD enhancement by LLESs is at least partially captured by the existing theoretical simulation, while the symmetry consideration in vibronic coupling provides further insight into the mechanisms behind the VCD sign-flip. Full article

Chiral metasurfaces exploit structural asymmetry to control circular polarized light, presenting new possibilities for the design of optical devices, specifically in the dynamic control of light and enhanced optical sensing fields. This study employed theoretical and computational methods to examine the chiroptical properties of a bilayer crescent chiral metasurface, demonstrating the effect of the angle of rotation on the chiroptical response. We particularly investigated the changes in transmittance, electric field distribution, and circular dichroism (CD) across various rotation angles. The crescent chiral metasurface demonstrated the maximum CD and showed significant control over the CD and electric field distribution across different rotation angles in the near-infrared region. The highest CD value was observed at a 23° rotation angle, where the chiroptical response reached its maximum. In addition, the left circular polarized light showed a stronger intensity of the electric field along the crescent metasurface edge relative to the right circular polarized light, underscoring the significant difference in the intensity and field localization. It was also shown that the configuration with a 2 by 2-unit cell, compared with a single-unit cell, exhibited significantly enhanced CD, thus underlining the importance of the unit cell arrangement in optimizing the chiroptical properties of metasurfaces for advanced photonic applications. These results prove that the 2 by 2 bilayer crescent chiral metasurface can be tailored to a fine degree for specific applications such as improved biosensing, enhanced optical communications, and precise polarization control by optimizing the configuration. The insight presented by this theoretical and computational study will contribute to the broad understanding of chiroptical phenomena as well as pave the way for potential applications in developing advanced optical devices with tuned chiroptical interactions. Full article

Chiral layered coordination polymers have attracted considerable attention not only because of their intriguing physicochemical properties but also because of their ability to exfoliate into chiral nanosheets. Chiral metal phosphonates with layered structures are of particular interest due to their relatively high thermal and water stabilities, but their corresponding nanosheets are rarely reported on. Herein, we report on a pair of enantiopure zinc phosphonates with the formula S- and R-Zn₈(cyampH)₈Cl₈ (S-Zn, R-Zn), where S- and R-cyampH₂ represent S- and R-(1-cyclohexylamino)methylphosphonic acids. They have layered structures in which the {ZnO₃Cl} tetrahedra are connected by {PO₃C} tetrahedra via corner-sharing. By doping analogous chromophore ligands S- and R-(1-naphthalenethylamino)methylphosphonic acid (S-, R-nempH₂), we obtained compounds S- and R-Zn₈(cyampH)_8-n(nempH)_nCl₈ (S-, R-Zn-x%, x = 2, 4, 6), which exhibited obvious circular dichroism (CD) and circularly polarized luminescence (CPL) properties. The bulk samples of S-Zn and S-Zn-4% were further subjected to exfoliation in acetone, resulting in chiral nanosheets of one–three-layer thicknesses. Full article

Circularly polarized luminescence (CPL) is an emerging field with significant applications in molecular electronics, optical materials, and chiroptical sensing. Achieving efficient CPL emission in organic systems remains a major challenge, particularly in the development of materials with high fluorescence quantum yields (Φ_F) and large luminescence dissymmetry factors (g_lum). Herein, we report the efficient synthesis of shape-persistent tetraphenylethylene macrocycles and investigate its potential as a CPL material. Chiral side chains were introduced to induce chiroptical properties. The macrocycles and their properties were characterized using NMR, MALDI-TOF MS, FT-IR, TGA, DSC, UV-Vis spectroscopy, SEM, fluorescence spectroscopy, ECD, and CPL. A significant fluorescence enhancement was observed upon aggregation, demonstrating a typical aggregation-induced emission (AIE) behavior. Moreover, one of the macrocycles in the solid state displayed distinct CPL emission with a high g_lum of 2 × 10⁻² and a Φ_F value reaching 60%, and exhibited aggregation-induced circularly polarized luminescence (AICPL). These findings highlight the advantage of using a macrocycle with a noncollapsible backbone for the design of organic systems with CPL property, offering promising applications in chiroptical materials. Full article

Achieving superior circularly polarized luminescence brightness (B_CPL) is an important subject and continuous challenge for chiroptical materials. Herein, by applying a binary molecular design for the synthesis of chiral organo-Tb³⁺ molecules, a novel pair of mononuclear chiral tris-pyrazolate-Tb³⁺ enantiomers, [Tb(PMIP)₃(R,R-Ph-PyBox)] (2) and [Tb(PMIP)₃(S,S-Ph-PyBox)] (5), have been synthesized and characterized. The three 1-phenyl-3-methyl-4-(isobutyryl)-5-pyrazolone (HPMIP) ligands play the role of efficient luminescence sensitizers and strong light-harvesting antennas, while the enantiopure 2,6-bis(4-phenyl-2-oxazolin-2-yl) pyridine ligand (R,R/S,S-Ph-PyBox) is employed as the strong point-chiral inducer. With the proper combination of the HPMIP and Chiral-Ph-PyBox within the Tb³⁺ enantiomers, strong (PMIP)⁻-centered π-π^* electronic absorption (ε_{263 nm} = 38,400–39,500 M⁻¹ cm⁻¹) and brilliant high-purity ligand-sensitized Tb³⁺-centered green luminescence (Φ_PL = 47–48%) were observed. In addition, a clear circularly polarized luminescence (CPL) activity (|g_lum| = 0.096–0.103) was also observed, resulting in a strong B_CPL (610–623 M⁻¹ cm⁻¹) for the two Tb³⁺ enantiomers from the hypersensitive transitions. Our results offer an effective path to develop high-performance chiroptical organo-Tb³⁺ luminophores. Full article

Semiconductor colloidal nanostructures capped with chiral organic molecules are a research hotspot due to their wide range of important implications for photonic and spintronic applications. However, to date, the study of chiral ligands has been limited almost exclusively to naturally occurring chiral amino and hydroxy acids, which typically contain only one stereocenter. Here, we show the pronounced induction of chirality in atomically thin CdSe nanoplatelets (NPLs) by capping them with enantiopure menthol derivatives as multi-stereocenter molecules. L-(−)/D-(+)-menthyl thioglycolate, easily synthesized from L-(−)/D-(+)-menthol, is attached to Cd-rich (001) basal planes of 2- and 3-monolayer (ML) CdSe NPLs. We show the appearance of narrow sign-alternating bands in the circular dichroism (CD) spectra of 2 ML NPLs corresponding to heavy-hole (HH) and light-hole (LH) excitons with maximal dissymmetry g-factor up to 2.5 × 10⁻⁴. The most intense CD bands correspond to the lower-energy HH exciton, and in comparison with the N-acetyl-L-Cysteine ligand, the CD bands for L-(−)-menthyl thioglycolate have the opposite sign. The CD measurements are complemented with magnetic CD measurements and first-principles modeling. The obtained results may be of interest for designing new chiral semiconductor nanostructures and improving understanding of their chiroptical properties. Full article

Electropolymerization is a convenient way to obtain conducting polymers (CPs) directly adhered to an electrode surface. CPs are well-known for their various application fields in photovoltaic cells, chemical sensors, and electronics. By implementing chirality into a CP, the application possibilities will spread further onto chiral sensors or optoelectronics. In this work, we introduce a new inherently chiral polymer based on a macrocyclic 3,4-ethylenedioxythiophene-diketopyrrolopyrrole-3,4-ethylenedioxythiophene triad (EDOT-DPP-EDOT) fused by 1,4-phenylene groups, which was prepared via oxidative electropolymerization directly on the electrode surface. The investigation of the chiroptical properties was performed by circular dichroism spectroscopy in the solid state. The enantiomeric pure polymer films obtained showed dissymmetry factors of up to −2.71 × 10⁻⁴, whereby linear dichroism contributions can be widely excluded. Full article

The properties of circularly polarized light has recently been used to selectively reflect chiral metasurfaces. Here we report the more complete basic functionalities of reflectors and absorbers that display various optical phenomena under circularly polarized light at normal incidence as before. For the chiral metamirrors we designed, the circular dichroism in about 0.4 reflection is experimentally observed in visible wavelengths. The experimental results also show high reflectance for right-handed circular polarization with preserved handedness and strongly absorbed left-handed circular polarization at chiroptical resonant wavelengths. By combining a nanobrick and wire grating for our design, we find and offer a new structure to demonstrate the superposition concept of the phase in the same plane that is helpful in effectively designing chiral metamirrors, and could advance development of their ultracompact optical components. Full article

The reversible photo-induced conformation transition of a single molecule with a [5]helicene backbone has garnered considerable interest in recent studies. Based on such a switching process, one can build molecular photo-driven switches for potential applications of nanoelectronics. But the achievement of high-performance reversible single-molecule photoswitches is still rare. Here, we theoretically propose a 13,14-dimethylcethrene switch whose photoisomerization between the ring-closed and ring-open forms can be triggered by ultraviolet (UV) and visible light irradiation. The electronic structure transitions and charge transport characteristics, concurrent with the photo-driven electrocyclization of the molecule, are calculated by the non-equilibrium Green’s function (NEGF) in combination with density functional theory (DFT). The electrical conductivity bears great diversity between the closed and open configurations, certifying the switching behavior and leading to a maximum on–off ratio of up to 10³, which is considerable in organic junctions. Further analysis confirms the evident switching behaviors affected by the molecule–electrode interfaces in molecular junctions. Our findings are helpful for the rational design of organic photoswitches at the single-molecule level based on cethrene and analogous organic molecules. Full article