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Peyssonnoside A is an unusual natural product consisting of a diterpene unit and a sulfonated monosaccharide. The experimental and theoretical comparison of Optical Rotatory Dispersion (ORD) and quantitative Nuclear Magnetic Resonance (NMR) data provided strong evidence for the stereochemistry of the diterpene unit. However, predicted Vibrational Circular Dichroism (VCD) spectra of Peyssonnoside A at the B3LYP/6-311++G(2d,2p) level showed poor correlation to the corresponding experimental spectra, preventing independent absolute configuration (AC) determination from VCD analysis. New calculations using the B3PW91 functional and the 6-311G(3df,2pd) basis set suggest that we can now independently and confidently assign the AC of Peyssonnoside A through VCD analyses. The use of f-polarization functions is responsible for the current successful assignment, compared to previously failed VCD analysis. This study highlights two important points: (a) the importance of using multiple levels of theories for satisfactorily reproducing the experimental spectra and (b) for quantitative comparisons using similarity indices, it is important to consider not only the VCD spectra but also the corresponding absorption spectra. [ABSTRACT FROM AUTHOR]

A comprehensive theory is developed for the chiral optical response of two configurations of the N-oscillator Born–Kuhn model (NOBK): the helically stacked and the corner stacked models. In the helical NOBK model, there is always a chiral response regardless of the value of N, whereas in the corner NOBK, only configurations with even N demonstrate a chiral response. Generally, the magnitudes of optical rotatory dispersion (ORD) and circular dichroism (CD) increase with N when the parameters of each oscillator are fixed. In cases of weak coupling, the spectral shapes of ORD and CD remain invariant, while strong coupling significantly alters the spectral shapes. For large damping, the spectral amplitude becomes smaller, and the spectral features become broader. In the presence of small damping, strong coupling introduces degeneracy in the coupled oscillator system, leading to multiple spectral features in both ORD and CD across the entire spectral region. This simple model can not only help in the design of tunable chiral metamaterials but also enhance our understanding of chiro-optical responses in structures with different configurations. [ABSTRACT FROM AUTHOR]

The nonresonant optical activity of two highly flexible aliphatic amines, (2R)‐3‐methyl‐2‐butanamine (R‐MBA) and (2R)‐(3,3)‐dimethyl‐2‐butanamine (R‐DMBA), has been probed under isolated and solvated conditions to examine the roles of conformational isomerism and to explore the influence of extrinsic perturbations. The optical rotatory dispersion (ORD) measured in six solvents presented uniformly negative rotatory powers over the 320–590 nm region, with the long‐wavelength magnitude of chiroptical response growing nearly monotonically as the dielectric constant of the surroundings diminished. The intrinsic specific optical rotation, αλT (in deg dm−1 [g/mL]−1), extracted for ambient vapor‐phase samples of R‐MBA [−11.031(98) and −2.29 (11)] and R‐DMBA [−9.434 (72) and −1.350 (48)] at 355 and 633 nm were best reproduced by counterintuitive solvents of high polarity (yet low polarizability) like acetonitrile and methanol. Attempts to interpret observed spectral signatures quantitatively relied on the linear‐response frameworks of density‐functional theory (B3LYP, cam‐B3LYP, and dispersion‐corrected analogs) and coupled‐cluster theory (CCSD), with variants of the polarizable continuum model (PCM) deployed to account for the effects of implicit solvation. Building on the identification of several low‐lying equilibrium geometries (nine for R‐MBA and three for R‐DMBA), ensemble‐averaged ORD profiles were calculated at T = 300 K by means of the independent‐conformer ansatz, which enabled response properties predicted for the optimized structure of each isomer to be combined through Boltzmann‐weighted population fractions derived from corresponding relative internal‐energy or free‐energy values, the latter of which stemmed from composite CBS‐APNO and G4 analyses. Although reasonable accord between theory and experiment was realized for the isolated (vapor‐phase) species, the solution‐phase results were less satisfactory and tended to degrade progressively as the solvent polarity increased. These trends were attributed to solvent‐mediated changes in structural parameters and energy metrics for the transition states that separate and putatively isolate the equilibrium conformations supported by the ground electronic potential‐energy surface, with the resulting displacement of barrier locations and/or decrease of barrier heights compromising the underlying premise of the independent‐conformer ansatz. [ABSTRACT FROM AUTHOR]

Two new phenolic compounds Fusagunolics A (1) and B (2) were isolated from the plant endophytic fungus Fusarium guttiforme, in addition to the previously known metabolites (3-6). The structures of these compounds was elucidated using a combination of spectroscopic analyses, including UV, HRESIMS, 1 D, and 2 D NMR, as well as electronic circular dichroism (ECD) and the optical rotatory dispersion (ORD). Further, the anti-inflammatory activity of all the compounds was evaluated to assess their capability to inhibit nitric oxide (NO) production by RAW 264.7 macrophages. The bioactive screening revealed that compounds 2 and 6 exhibited moderate inhibitory effects against NO production with the IC50 values 28.6 and 37.6 μM, respectively. [ABSTRACT FROM AUTHOR]

A comprehensive theory is developed for the chiral optical response of two configurations of the N-oscillator Born–Kuhn model (NOBK): the helically stacked and the corner stacked models. In the helical NOBK model, there is always a chiral response regardless of the value of N, whereas in the corner NOBK, only configurations with even N demonstrate a chiral response. Generally, the magnitudes of optical rotatory dispersion (ORD) and circular dichroism (CD) increase with N when the parameters of each oscillator are fixed. In cases of weak coupling, the spectral shapes of ORD and CD remain invariant, while strong coupling significantly alters the spectral shapes. For large damping, the spectral amplitude becomes smaller, and the spectral features become broader. In the presence of small damping, strong coupling introduces degeneracy in the coupled oscillator system, leading to multiple spectral features in both ORD and CD across the entire spectral region. This simple model can not only help in the design of tunable chiral metamaterials but also enhance our understanding of chiro-optical responses in structures with different configurations.

Electro-optically active low-bandgap conjugated copolymers were obtained by electrochemical polymerization (EP) in cholesteric liquid crystal (CLC). We prepared CLC electrolyte mixture blends of monomers, and electrochemically polymerized for obtaining conjugated copolymer with optical activity, in which the structure of the CLC is transferred, from achiral monomers on a CLC template. In addition, this copolymer showed a narrow bandgap and a significant red shift of the absorption band compared to the homopolymer. The optical rotatory dispersion (ORD) indicates that the polymer is chiroptically active and that the optical rotation can be tuned via redox. The guest monomers used for the EP in liquid crystal (LC) require solubility in the host LC and a rod-like structure, limiting their structural design. This technique has the advantage that complex synthesis of monomers is no required, and simple composition of monomers can be used to prepare copolymer films in a convenient manner by blending various monomers. This method expands the design range of optically active electrochromic devices based on conjugated polymers with pleochroic properties. [ABSTRACT FROM AUTHOR]

Objective: The aim of this research was the isolation, structure elucidation and evaluation of the bioactivity of natural products produced by an Aureobasidium pullulans fungal endophyte of the medicinal plant Thuja occidentalis. Methods: The natural products were isolated from an extract of A. pullulans culture broth by reversed-phase chromatography and their structures were elucidated based on analysis of HRESIMS and 1D/2D NMR data. The absolute configurations of the compounds were assigned by comparison of their electronic circular dichroism (ECD) and optical rotatory dispersion (ORD) data with values obtained for Boltzmann-weighted conformer ensembles calculated by density functional theory. Results/Conclusion: Two new C11-polyketides, aureobasidol A (1) and B (2), were isolated from the A. pullulans extract. Both polyketides showed selective but weak inhibitory activity against Mycobacterium tuberculosis in vitro. [ABSTRACT FROM AUTHOR]

Triacetone triperoxide (TATP) and hexamethylene triperoxide diamine (HMTD) are cyclic peroxides that exhibit atropisomerism resulting from restricted rotation around three peroxide bonds. As a result, one pair of enantiomers with D3 symmetry and another pair of enantiomers with C2 symmetry can be identified. Previous studies, based on mass spectrometry data and computational results, have shown that conformations of TATP with D3 and C2 symmetry can be isolated. Assuming that enantiomer samples of TATP and HMTD can be obtained with sufficient enantiopurity, we investigated their chiroptical properties, namely, optical rotatory dispersion (ORD), vibrational circular dichroism (VCD), and Raman optical activity (VROA). ORD curves and VCD spectra are seen to be very similar for D3‐ and C2‐symmetric atropisomers with the same overall helicity. Predicted VROA results, however, show significant differences between D3‐ and C2‐symmetric atropisomers with the same overall helicity. The D3‐symmetric atropisomer is predicted to exhibit considerably larger magnitude vibrational optical activity signals than the C2‐symmetric atropisomer. [ABSTRACT FROM AUTHOR]

A novel β-carboline, namely Plagranline A (1), and a known alkaloid (2) were isolated from the roots of Platycodon grandiflorus. Their structure was elucidated using a combination of spectroscopic analyses and computational chemistry, including electronic circular dichroism (ECD) and optical rotatory dispersion (ORD). Alkaloids 1 and 2 exhibited moderate inhibitory effects against NO production. Interestingly, 1 and 2 are the first alkaloid constituents reported from the plant P. grandifloras. [ABSTRACT FROM AUTHOR]

A new monoterpene rhamnoside, (+)-(R)-α-terpineol α-L-rhamnoside (1), along with ten known compounds (2–11) were obtained after purification of the ethanol extract of Cercis glabra legumes. Their structures were elucidated by spectroscopic evidence including NMR, optical rotatory dispersion (ORD), HR-ESIMS and chemical hydrolysis. In the acetylcholinesterase inhibitory assay, compounds 3 and 8 showed high percentages of inhibition which were comparable to the activity of donepezil (a commercial drug, the positive control), and exhibited IC50 values of 0.488, 0.391 mg/mL. These bioactive components could be promising acetylcholinesterase inhibitors. [ABSTRACT FROM AUTHOR]

Density functional theory is widely used for modeling the magnetic properties of molecules, solids, and surfaces. Rung-3.5 ingredients, based on the expectation values of nonlocal one-electron operators, are new promising tools for the construction of exchange-correlation functional approximations. We present the formal extension of rung-3.5 ingredients to the calculation of magnetic properties. We add to the underlying nonlocal operators a dependence on the gauge of the magnetic field, and we derive the working equations for rung-3.5 expectation values in basis sets of gauge-including atomic orbitals. We demonstrate that the gauge corrections are significant. We conclude with an initial study of chemical shifts, optical rotatory dispersion, and Raman optical activity spectra predicted by M11plus, a range-separated hybrid meta functional incorporating nonlocal rung-3.5 correlation. M11plus proves to be reasonably accurate, further motivating the incorporation of nonlocal rung-3.5 ingredients in new density functional approximations. [ABSTRACT FROM AUTHOR]

With the increasing interest in compounds containing heavier elements, the experimental and theoretical community requires computationally efficient approaches capable of simultaneous non-perturbative treatment of relativistic, spin-polarization, and electron correlation effects. The ReSpect program has been designed with this goal in mind and developed to perform relativistic density functional theory (DFT) calculations on molecules and solids at the quasirelativistic two-component (X2C Hamiltonian) and fully relativistic four-component (Dirac–Coulomb Hamiltonian) level of theory, including the effects of spin polarization in open-shell systems at the Kramers-unrestricted self-consistent field level. Through efficient algorithms exploiting time-reversal symmetry, biquaternion algebra, and the locality of atom-centered Gaussian-type orbitals, a significant reduction of the methodological complexity and computational cost has been achieved. This article summarizes the essential theoretical and technical advances made in the program, supplemented by example calculations. ReSpect allows molecules with >100 atoms to be efficiently handled at the four-component level of theory on standard central processing unit-based commodity clusters, at computational costs that rarely exceed a factor of 10 when compared to the non-relativistic realm. In addition to the prediction of band structures in solids, ReSpect offers a growing list of molecular spectroscopic parameters that range from electron paramagnetic resonance parameters (g-tensor, A-tensor, and zero-field splitting), via (p)NMR chemical shifts and nuclear spin–spin couplings, to various linear response properties using either conventional or damped-response time-dependent DFT (TDDFT): excitation energies, frequency-dependent polarizabilities, and natural chiroptical properties (electronic circular dichroism and optical rotatory dispersion). In addition, relativistic real-time TDDFT electron dynamics is another unique feature of the program. Documentation, including user manuals and tutorials, is available at the program's website http://www.respectprogram.org. [ABSTRACT FROM AUTHOR]

We present a detailed theory, implementation, and a benchmark study of a linear damped response time-dependent density functional theory (TDDFT) based on the relativistic four-component (4c) Dirac–Kohn–Sham formalism using the restricted kinetic balance condition for the small-component basis and a noncollinear exchange–correlation kernel. The damped response equations are solved by means of a multifrequency iterative subspace solver utilizing decomposition of the equations according to Hermitian and time-reversal symmetry. This partitioning leads to robust convergence, and the detailed algorithm of the solver for relativistic multicomponent wavefunctions is also presented. The solutions are then used to calculate the linear electric- and magnetic-dipole responses of molecular systems to an electric perturbation, leading to frequency-dependent dipole polarizabilities, electronic absorption, circular dichroism (ECD), and optical rotatory dispersion (ORD) spectra. The methodology has been implemented in the relativistic spectroscopy DFT program ReSpect, and its performance was assessed on a model series of dimethylchalcogeniranes, C4H8X (X = O, S, Se, Te, Po, Lv), and on larger transition metal complexes that had been studied experimentally, [M(phen)3]3+ (M = Fe, Ru, Os). These are the first 4c damped linear response TDDFT calculations of ECD and ORD presented in the literature. [ABSTRACT FROM AUTHOR]

Optically active nanobiocolloids (NBC) containing plasmonic nanoparticles (NP) covered by helical biomacromolecules are interesting for various theranostic applications. We report the study of NBC colloids containing from 4.4 to 9.3 w/w % of small (ca. 10 nm) spherical AgNPs covered by polygalacturonic acid (PGA). The AgNPs were obtained by reduction of silver ions with the functional groups of PGA. The NBC structure was formed by nanoprecipitation of the final solution into an anti-solvent (ethanol) bath. The NBC powders were characterized by transmission electron and atomic force (AFM) microscopies, FT-IR, and X-ray diffraction. The FT-IR analysis showed that the carboxylate groups of PGA were attached to the AgNPs' surface by bidentate binding. The PGA (the major constituent of the main chain of pectins) is a weak anionic polysaccharide which helical conformations and their self-assembly depend on the deprotonation of carboxyl groups. We studied how pH influences the form, size, depolarization of scattered light, and chiroplasmonic properties of NBC. The optical rotatory dispersion of NBC exhibited plasmonically enhanced Cotton effect related to helical PGA macromolecules capped to AgNPs. The Cotton effect changed its sign from negative (at pH 4.01) to positive (at pH 6.86) implying the inversion of handedness of the PGA helixes. By using dynamic and depolarized dynamic light scattering, the effective hydrodynamic radii were calculated for translational (Rh) and rotational (Rrot) diffusion. Their characteristic ratio Rrot/Rh expressed in terms of the Perrin frictional coefficients showed that the form of NBC colloids changed from spherical to elongated with decreasing pH. The elongated form in the acidic buffer was attributed to the side-by-side stacking of the helical segments of PGA. Low fraction of coupled plasmons and plasmonic enhancement of elliptical polarization of light by the helical conformers of PGA were both responsible for high depolarization of light scattered by NBC colloids. The highest depolarization degree of 40% observed in the acidic buffer was ascribed to the non-uniform elliptical shell of PGA around AgNPs. Contrary to the pristine particles of sodium polygalacturonate (PGA@Na), the NBC retained their size upon drying, as shown by AFM. In accord, comparison of the FT-IR spectra of NBC and PGA@Na showed that the NBC were stabilized by additional hydrogen bonds. [ABSTRACT FROM AUTHOR]

Cercis glabra is a plant belonging to the legume family, whose flowers and barks are commonly used as food and traditional Chinese medicines. However, its leaves are usually disposed of as wastes. This research comprehensively investigated the bioactive constituents of C. glabra leaves, and two new phenolic, ceroffesters A-B (1–2) and thirteen known compounds (3–15) were isolated. Their structures were elucidated by spectroscopic methods such as nuclear magnetic resonance (1D NMR and 2D NMR), high-resolution electrospray ionization mass spectra (HR-ESI-MS), optical rotatory dispersion (ORD) and electronic circular dichroism (ECD). All of them were assessed for their antioxidant activities through ABTS, DPPH and PTIO methodologies, and evaluated for inhibitory activities against two enzymes (mushroom tyrosinase and acetylcholinesterase). As a result, compounds 3–6, 10 and 13 exhibited evident antioxidant activities. Meanwhile, compounds 5, 10 and 13 showed the most potent tyrosinase inhibitory activities, with IC50 of 0.64, 0.65 and 0.59 mM, and compared with the positive control of 0.63 mM (kojic acid). In the initial concentration of 1 mg/mL, compounds 3, 5 and 6 demonstrated moderate inhibitory activities against acetylcholinesterase with 85.27 ± 0.06%, 83.65 ± 0.48% and 82.21 ± 0.09%, respectively, compared with the positive control of 91.17 ± 0.23% (donepezil). These bioactive components could be promising antioxidants, tyrosinase and acetylcholinesterase inhibitors. [ABSTRACT FROM AUTHOR]

Hexahydrocurcumin (HHC) and octahydrocurcumin (OHC) were synthesized, and their enantiomers were separated using supercritical fluid chromatography. The absolute configurations (ACs) of HHC and OHC were independently determined using experimental measurements and quantum theoretical predictions of vibrational circular dichroism, electronic circular dichroism, and optical rotatory dispersion. These studies lead to AC assignments of (−)‐(R)‐HHC and (+)‐(R,R)‐OHC. The AC of OHC is further confirmed by its structure determined from single crystal x‐ray diffraction. [ABSTRACT FROM AUTHOR]

Compact, lightweight, and on-chip spectrometers are required to develop portable and handheld sensing and analysis applications. However, the performance of these miniaturized systems is usually much lower than their benchtop laboratory counterparts due to oversimplified optical architectures. Here, we develop a compact plasmonic "rainbow" chip for rapid, accurate dual-functional spectroscopic sensing that can surpass conventional portable spectrometers under selected conditions. The nanostructure consists of one-dimensional or two-dimensional graded metallic gratings. By using a single image obtained by an ordinary camera, this compact system can accurately and precisely determine the spectroscopic and polarimetric information of the illumination spectrum. Assisted by suitably trained deep learning algorithms, we demonstrate the characterization of optical rotatory dispersion of glucose solutions at two-peak and three-peak narrowband illumination across the visible spectrum using just a single image. This system holds the potential for integration with smartphones and lab-on-a-chip systems to develop applications for in situ analysis. The authors develop an imaging-based intelligent spectrometer on a plasmonic "rainbow" chip. It can accurately and precisely determine the spectroscopic and polarimetric information of the illumination spectrum using a single image assisted by suitably trained deep learning algorithms. [ABSTRACT FROM AUTHOR]

During the process of searching for tyrosinase inhibitors from natural medicines, one new monoterpene rhamnoside (1) and 13 known compounds (2–14) were isolated from the ethanolic extract of Betula platyphylla barks by repeated column chromatography. These structures were identified by comprehensive spectroscopic data analysis such as high-resolution electrospray ionization mass spectra (HR-ESI-MS), nuclear magnetic resonance (NMR), optical rotatory dispersion (ORD) and acid hydrolysis. In vitro assay revealed that compounds 6, 7 and 14 showed obvious inhibitory activity against tyrosinase. [ABSTRACT FROM AUTHOR]

Enantioselectivity sensing is crucial in biological systems due to the impact of the selective behaviors of chiral compounds on their targets. Conventional approaches for detecting enantioselectivity are restricted by the presence of high phonon energy, complex device manufacturing processes, low sensitivity, and the need for large sample sizes. Here, we propose a single-walled carbon nanotube (SWNT)-based fluidic chip that uses terahertz (THz) optical rotatory dispersion (ORD) spectroscopy to detect tartaric acids with high selectivity in very small amounts of liquid. The chip is composed of tailored U-shaped metasurfaces that show significant amplification of the near-field around the typical peaks of tartaric acids in the ORD spectrum. Additionally, it includes subwavelength gratings made of SWNTs, allowing for accurate detection of polarization angles. The limit of detection (LOD) for d -tartaric acid and l -tartaric acid are 17.9 mg/L and 11.0 mg/L, respectively. The sensitivities are superior to those of UV ORD or CD spectrometers. Furthermore, the presence of tartaric acid in wine is effectively identified, with a LOD of 25.60 mg/L. This technological development provides a significant improvement in chiral analysis by allowing for quick, highly sensitive, and precise detection of enantiomers. Schematic illustration of biosensing based on the proposed SWNT-based fluidic chips. [Display omitted] [ABSTRACT FROM AUTHOR]

One novel monoterpene rhamnoside (1) and 7 known monoterpenes (2-8) were isolated from the ethanol extract of Cynanchum atratum for the first time. Their structures were identified by comprehensive spectroscopic data analysis such as nuclear magnetic resonance, high-resolution electrospray ionization mass spectra, optical rotatory dispersion, and acid hydrolysis. In the subsequent antioxidant assay, compound 8 exhibited obvious 2,2-diphenyl-2-picrylhydrazyl hydrate radical scavenging activity. [ABSTRACT FROM AUTHOR]

Two new phenolic rhamnosides (1–2) and 12 known phenolic compounds (3–14) were isolated from the ethanolic extract of Cinnamomum camphora barks by repeated column chromatography. The structures of all isolated compounds were identified by comprehensive spectroscopic data analysis such as high-resolution electrospray ionization mass spectra, nuclear magnetic resonance, optical rotatory dispersion and chemical method. In vitro assay revealed that compound 8 showed strong inhibitory activity against tyrosinase, and compounds 1, 3–7, 8–9, 13 showed obvious acetylcholinesterase inhibitory activity. [ABSTRACT FROM AUTHOR]

A high accuracy polarimetric method was used for measuring the values of the gyration tensor component g11 of Ca3Ga2Ge4O14for various wavelength of light. A calculation technique based on the polarizability theory of optical activity was applied to determine the dispersion of the optical rotatory power for investigated crystals in a wide spectral region. [ABSTRACT FROM AUTHOR]

A recent article in the National Science Review discusses the concept of chiral materials, which are materials that lack mirror symmetry. Chirality is found in nature, such as in DNA and proteins, and is also used to describe physical states of matter in quantum mechanics. The article highlights the unique properties of chiral materials, including their interaction with polarized light. The article also introduces a new method for creating chiral superstructures using quadrupole fields of permanent magnets, which allows for the assembly of materials of any size, shape, and chemical composition into chiral structures. This method has the potential to advance the design of chiral materials and optical devices. [Extracted from the article]

These days, single-crystal X-ray analysis is a routine method that not only allows the elucidation of the stereostructures of individual molecules but also gives insights regarding the crystal structures hiding symmetry/asymmetry-related issues. One of the most relevant fields includes optical activity that is the consequence of a kind of chirality center, such as an asymmetric C atom, while a heteroatom, like P. Atrop isomerism, may also be a reason. All kinds of symmetry-related problems in organic and inorganic chemistry may be the subject of papers submitted to I Symmetry i . [Extracted from the article]

These systems, obtained as a result of the condensation of low-molecular-weight (<=1 × 10 SP 6 sp Da) DNA in the presence of polyethylene glycol (PEG) and high salt concentration [[7]], have an outstanding CD signal intensity and are inexpensive and easy to prepare. At the same time, a decrease in the intensity of the CD signal to 22% of its initial value was noted with an increase in the DMSO content to 5.00 vol %. [Extracted from the article]

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Thirteen previously undescribed steroidal saponins, named parisverticilloside A-M (1 – 13) and twenty known steroidal saponins (14 – 33) were isolated from ethanol extract of the roots of Paris verticillata. Their structures were identified by a series of spectroscopic methods, including 1D and 2D NMR, HR-ESI-MS, optical rotatory dispersion and chemical processes. The anti-proliferative activities of all compounds against LN229, HepG2, MDA-MB-231 and 4T1 cell lines were evaluated using the CCK8 assay with cisplatin or capecitabine as the positive control. The anti-inflammatory activities of all compounds were measured by inhibition of LPS-induced NO release from BV2 cell lines, with dexamethasone as the positive control. [Display omitted] • Thirteen previously undescribed steroidal saponins were isolated from the roots of Paris verticillata. • The structures were identified by 1D and 2D NMR, HRESIMS, IR, and physical properties. • Steroidal saponins have anti-proliferative and the anti-inflammatory activities. [ABSTRACT FROM AUTHOR]

• Optical rotation is the most important characteristic of optical active materials. • Optical rotatory dispersion is widely used in analytical chemistry. • The proposed design of a differential spectropolarimeter based on phase measurements does not require high-precision angle measuring devices. • Such a spectropolarimeter has a low cost, compact size and high accuracy. This paper considers the features of polarimetric methods used for the analysis of optically active substances. It presents a design of a differential spectropolarimeter operating by analyzing the phase difference between two harmonical signals received when splitting a laser beam from a common source into separate reference and object beams. The expediency of using the Fourier transform to calculate the phase difference of differential spectropolarimeter signals is noted. The results of calculating the parameters of the measuring method and the results of an experimental study of reference polarimetric plates at various wavelengths are presented. The error in measuring the optical rotation angle in the wavelength range 405–780 nm did not exceed ±0.005°. [ABSTRACT FROM AUTHOR]

Optical activity, a foundational part of chemistry, is not restricted to chiral molecules although generations have been instructed otherwise. A more inclusive view of optical activity is valuable because it clarifies structure–property relationships however, this view only comes into focus in measurements of oriented molecules, commonly found in crystals. Unfortunately, measurements of optical rotatory dispersion or circular dichroism in anisotropic single crystals have challenged scientists for more than two centuries. New polarimetric methods for unpacking the optical activity of crystals in general directions are still needed. Such methods are reviewed as well as some of the 'nourishment' they provide, thereby inviting to new researchers. Methods for fitting intensity measurements in terms of the constitutive tensor that manifests as the differential refraction and absorption of circularly polarized light, are described, and examples are illustrated. Single oriented molecules, as opposed to single oriented crystals, can be treated computationally. Structure–property correlations for such achiral molecules with comparatively simple electronic structures are considered as a heuristic foundation for the response of crystals that may be subject to measurement. [ABSTRACT FROM AUTHOR]

The equilibrium constant of the PLLA-C70 complex was determined spectrophotometrically and found at 1084 M−1, a value fully comparable with the equilibrium constant of the PLLA-C60 complex 956 M−1. In fact, both C60 and C70 share practically the same electron affinity and both are able to form charge-transfer complex with poly(L-lactic acid) (PLLA) in dichloromethane solution. The PLLA-C70 complex in CH2Cl2 solution shows also a pronounced extrinsic or induced Cotton effect when analyzed with optical rotatory dispersion (ORD) spectroscopy suggesting a kind of host-guest interaction where the helical conformation of PLLA by binding C70 internally or externally to the helical coils, is able to induce the optical activity to the achiral C70. [ABSTRACT FROM AUTHOR]

We propose a kind of spectral polarization-encoding (SPE) for broadband light pulses, which is realized by inducing optical rotatory dispersion (ORD), and decoded by compensating ORD. Combining with polarization-sensitive devices, SPE can not only work to control polarization-dependent transmission for central wavelength or bandwidth-tunable filtering, but also can be used for broadband regenerative or multi-pass amplification with a polarization-dependent gain medium to improve output bandwidth. SPE is entirely passive thus very simple to be designed and aligned. By using an ORD crystal with a good transmission beyond 3-μm mid-infrared region, e.g., AgGaS2, SPE promises to be applied for the wavelength tuning lasers in mid-infrared region, where the tunning devices are rather under developed compared with those in visible and near-infrared region. [ABSTRACT FROM AUTHOR]

Life is pervasive on planet Earth, but whether life is ubiquitous in the Galaxy and sustainable over timescales comparable to stellar evolution is unknown. Evidence suggests that life first appeared on Earth more than 3.77 Gyr ago, during a period of heavy meteoric bombardment. Amino acids, the building blocks of proteins, have been demonstrated to exist in interstellar ice. As such, the contribution of space-generated amino acids to those existing on Earth should be considered. However, detection of space amino acids is challenging. In this study, we used analytical data from several meteorites and in situ measurements of the comet 67P/Churyumov-Gerasimenko collected by the Rosetta probe to evaluate the detectability of alanine by ultraviolet spectropolarimetry. Alanine is the second-most abundant amino acid after glycine and is optically active. This chirality produces a unique signature that enables reliable identification of this amino acid using the imprint of optical rotatory dispersion (ORD) and circular dichroism (CD) in the ultraviolet spectrum (130–230 nm). Here, we show that the ORD signature could be detected in comets by using ultraviolet spectropolarimetric observations conducted at middle size space observatories. These observations can also provide crucial information for the study of sources of enantiomeric imbalance on Earth. [ABSTRACT FROM AUTHOR]

The CD signals we measure consist of the sum of circular differential scattering and absorption ( HT ht ). We chose an aqueous background of permittivity HT ht . Plus and minus signs correspond to left and right circularly polarized light wavenumbers HT ht and HT ht , respectively. [Extracted from the article]

The crystal structure of the anticancer drug oxaliplatin, [Pt(R,R-DACH)(oxalate)] (DACH = diaminocyclohexane), was first reported in the non-centrosymmetric space group P21, confirming the sole presence of the R,R enantiomer of the DACH ligand [M. A. Bruck et al., Inorg. Chim. Acta, 92 (1984) 279-284]. It was later proposed that the crystal structure is better described in the centrosymmetric space group P21/m, signifying the presence of the compound as a racemic mixture [A. S. Abu-Surrah et al., Polyhedron, 22 (2003) 1529-1534]. Herein is presented a reinvestigation of this crystal structure, which shows that the discrepancy between the two proposed space group assignments arises from overlooked pseudo symmetry. The crystal structures of the synthetic precursor to oxaliplatin, Pt(R,R-DACH)I2, and a platinum(IV) derivative, trans-[Pt(R,R-DACH)(oxalate)(OH)2], were also determined, and the absolute configuration of the DACH ligand in each was confirmed to be R,R. A spectroscopic investigation of the optical rotatory dispersion (ORD) of the oxaliplatin crystals was carried out to further confirm the lack of the true crystallographic mirror plane required for a P21/m solution. The ORD was theoretically simulated, in one instance, by applying the Kramers-Kronig transform to the computed circular dichroism spectrum and was found to corroborate the spectroscopic and crystallographic findings. Finally, a brief discussion is given of the importance of discussing the details of nuanced crystal structures and of providing evidence in addition to X-ray structure determination if chemically unexpected results are obtained.

Another interesting type of system showing how chiral hierarchically organized architectures could arise from chiral molecules by non-classical pathway is optically active chiral supraparticles decorated with spikes or sheets.174-177 For example, right-handed twisting rod-like cellulose nanocrystals (CNCs) were used as a chiral template and building block for the formation of chiral CuO/CNC composite supraparticles (Figure 15A).177 These CNCs had three levels of chirality: (i) molecular chirality of glucose units, (ii) structural chirality of the right-handed nanorods, and (iii) chirality of cholesteric liquid crystal structure. Other geometrical shapes include left-handed ( B ) b and right-handed ( B ) b helices obtained by folding DNA strands.73 Complex chiral shapes can also be obtained by interconnecting NPs with multiple "springs" represented by DNA.74 Their chirality may not be initially obvious by visual comparison with familiar mirror-asymmetric shapes, such as helices, but they can be identified using chirality measures, for instance, Osipov-Pickup-Dunmur index that changes sign depending on the handedness of the structure.75 Continuing the consideration of scale, one can foresee the translation of the chirality of NPs into sub-millimeter, millimeter, and macroscale.76 Connection with biology Considering the rapid expansion of chiral nanostructures toward biology and medicine, it is instructive and insightful to draw parallels between hierarchical chirality in biological compounds and inorganic nanostructures. The optical properties of these nanostructures were compared to those of -HgS nanostructures, which also possessed crystallographic chirality but had achiral morphologies (nanocubes, nano-ellipsoids, nanorods, and nanowires), revealing that the optical activity of -HgS nanostructures with achiral morphologies originated from the chiral crystal lattice. [Extracted from the article]

7-Cyano-15-methoxy[6]helicene was synthesized, in 54% overall yield, through a short photochemical procedure including mild conditions and inexpensive reagents. The desired helical hexacyclic framework was characterized by 1H and 13C NMR and mass spectroscopies. Single crystals of the helicene were also obtained and an X-ray diffraction analysis is presented. Enantiomers of the helicene were obtained in 100% ee after separation by chiral HPLC and their chiroptical properties were experimentally investigated from optical rotatory dispersion and electronic circular dichroism (ECD). UV--Vis absorption and fluorescence properties of the helicene were evaluated in solutions and a strong emission was noted in the blue region of the visible spectrum . Its electrochemical behavior was also experimentally examined and HOMO and LUMO energy levels were estimated, showing an electrochemical band gap of 2.11 eV. The results obtained herein are helpful to explain the interest of cyano and methoxy groups in making the new material a good candidate to be used in optoelectronic applications. [ABSTRACT FROM AUTHOR]

Chiroptical switches, whose chiral optical signals such as optical rotatory dispersion (ORD), circular dichroism (CD) and circularly polarized luminescence (CPL) are reversibly interchangeable between two states, offer many promising applications in the fields of chiral sensing, optical displays, information storage, asymmetric catalysis and so on. Through various non-covalent interactions, supramolecular chiroptical switches have been constructed by combining the chiral and responsive functional components. This review summarizes the recent progress in the construction of supramolecular chiroptical switchable systems that reversibly respond to various stimuli, such as light, electricity, magnetic fields, mechanical force, solvents, pH, temperature, and chemical additives. The switching of supramolecular chirality in the forms of on/off, amplification/weakening and chirality inversion is shown. Additionally, the design of chiroptical switchable systems for chiral logic gates, data communication, chiral separation and asymmetric catalysis has been demonstrated. Future challenges in developing supramolecular chiroptical switches are also discussed. [ABSTRACT FROM AUTHOR]

A new phenylpentenol, wortmannine H (1) was isolated from Talaromyces wortmannii LGT-4, an endophytic fungus of Tripterygium wilfordii. The structure of 1 was elucidated by IR, MS, 1D and 2D NMR spectra and comparison of the experimental and calculated optical rotatory dispersion (ORD). Monoamine oxidase (MAO), acetylcholinesterase (AChE) and phosphoinositide 3-kinase (PI3Kα) inhibitory activities of 1 was also tested. The compound did not show good biological activity. [ABSTRACT FROM AUTHOR]

We present a new method based on optical null methods for simultaneously measuring the optical rotatory dispersion (ORD) and absorption spectra of chiral substances. The optical rotation angle at a specific wavelength can be obtained from the optical nulls of the Malus curves with and without the sample. We use the optical nulls of the two curves as benchmark points and the readings to the right of the benchmark points by a certain angular offset to eliminate the influence of the analyzer on the light intensity and obtain the absorbance of the chiral substance at a specific wavelength. The 4096 pixels of the line scan CCD can measure multiple wavelengths simultaneously so that continuous ORD and absorption spectra can be obtained. The experimental results show that the standard deviation of the specific optical rotation is 0.11 deg mL g−1 dm−1, the standard deviation of the maximum absorption wavelength is 0.45 nm, and that absorbance of the sample varies linearly with the concentration. This method is helpful for simplifying the experiment and has a profound influence on the analysis of the contents and molecular configurations of chiral substances in the future. [ABSTRACT FROM AUTHOR]

C60 fullerene forms an association complex with poly(l-lactic acid) (PLLA) in dichloromethane solution. The equilibrium constant of the complex was determined spectrophotometrically and found K' = 956 M−1. A new band in the ultraviolet, i.e., at 230 nm was assigned to the charge-transfer interaction between PLLA and C60, whereas the former acts as electron donor through the ketone of the ester group and the latter as electron acceptor being and electron-deficient olefin. The PLLA-C60 complex in CH2Cl2 solution was also studied by optical rotatory dispersion (ORD) spectroscopy. The complex showed a complicate induced Cotton effect in correspondence of the C60 electronic transitions at 404 and 326 nm confirming that PLLA and C60 are in close contact each other and suggesting a kind of host-guest interaction where the helical conformation of PLLA is able to induce the optical activity to the achiral C60 electronic transitions. The PLLA-C60 complex is thermoreversible and more stable at lower temperatures. [ABSTRACT FROM AUTHOR]

Plane-polarized monochromatic light is rotated in an optically active medium. The extent of the rotation is wavelength dependent, following an optical rotatory dispersion (ORD) curve. Typically, this phenomenon is studied by using a few discrete wavelengths. Here, we demonstrate optical rotation of white light. Corn syrup is used as the medium as large angles of optical rotation can be generated in compact containers. The Drude expression for ORD and Malus' law are used to predict the spectrum of the light transmitted as a function of the angle between polarizers located on either side of the sample. Despite the transmission spectrum of corn syrup in the absence of polarizers being unremarkable, optical rotation leads to a dramatic change in color because a "notch" is generated in the spectrum of the transmitted light. The extinction region can be translated across the spectrum by rotating the analyzer. The experimentally measured location of the region of maximum extinction and the color of the transmitted light are in excellent qualitative agreement with the predicted values. The experiment is ideal both as a lecture demonstration and for quantitative investigation in an undergraduate laboratory of the spectral distribution of light transmitted by a chiral medium. [ABSTRACT FROM AUTHOR]

Two new lignan glycosides (1, 2) and four known lignan glycosides (3–6) have been isolated from the ethanolic extract of the stems of Viburnum melanocarpum through repeated column chromatography. Their structures including absolute configurations were confirmed by spectroscopic data [one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectra (HRESIMS), optical rotatory dispersion (ORD) and circular dichroism (CD)] and chemical methods. Additionally, the α-glucosidase inhibitory activity of these compounds was tested in vitro. Compound 1 exhibited the strongest inhibitory activity against α-glucosidase with a half-maximal inhibitory concentration (IC50) value of 10.3 μM. [ABSTRACT FROM AUTHOR]

The optical rotatory dispersion (ORD) and circular dichroism of the conformationally flexible carvone molecule has been investigated in 17 solvents and compared with results from calculations for the 'free' (gas phase) molecule. The G3 method was used to determine the relative energies of the six conformers. The optical rotation of (R)-(-)-carvone at 589 nm was calculated using coupled cluster and density functional methods, including temperature-dependent vibrational corrections. Vibrational corrections are significant and are primarily associated with normal modes involving the stereogenic carbon atom and the carbonyl group, whose n → π* excitation plays a significant role in the chiroptical response of carvone. Without the inclusion of vibrational corrections the optical rotation calculated with CCSD and DFT has the opposite sign of experimental data. Calculations of optical rotation performed in solution using the polarizable continuum model were also opposite in sign when compared to that of the experiment. [ABSTRACT FROM AUTHOR]

A recently developed subsystem formalism within time-dependent density functional theory for excitation energies [J. Chem. Phys. 126, 134116 (2007)] is extended to the calculation of general response properties such as frequency-dependent polarizabilities or optical rotatory dispersion. Furthermore, explicit expressions for oscillator and rotatory strengths are presented. Polarizabilities and optical rotation tensors of the combined system are obtained as the sum of subsystem properties, so that a natural partitioning of the polarizability or the optical rotation is facilitated. This is of great advantage for the analysis of environmental effects on molecular response properties as it allows one to distinguish changes in the ground-state electronic structure of the subsystems from cooperative excited-state effects. A computational scheme that implements the formalism is presented together with applications highlighting the differences between embedding effects included in the subsystem potential and environmental response effects. The method avoids basis-set superposition errors in the calculation of response properties of large molecules, which occur in supermolecular calculations. Possible approximations to the full response algorithm are discussed. [ABSTRACT FROM AUTHOR]

This paper presents an approach for obtaining accurate interaction energies at the density functional theory level for systems where dispersion interactions are important. This approach combines Becke and Johnson’s [J. Chem. Phys. 127, 154108 (2007)] method for the evaluation of dispersion energy corrections and a Hirshfeld method for partitioning of molecular polarizability tensors into atomic contributions. Due to the availability of atomic polarizability tensors, the method is extended to incorporate anisotropic contributions, which prove to be important for complexes of lower symmetry. The method is validated for a set of 18 complexes, for which interaction energies were obtained with the B3LYP, PBE, and TPSS functionals combined with the aug-cc-pVTZ basis set and compared with the values obtained at the CCSD(T) level extrapolated to a complete basis set limit. It is shown that very good quality interaction energies can be obtained by the proposed method for each of the examined functionals, the overall performance of the TPSS functional being the best, which with a slope of 1.00 in the linear regression equation and a constant term of only 0.1 kcal/mol allows to obtain accurate interaction energies without any need of a damping function for complexes close to their exact equilibrium geometry. [ABSTRACT FROM AUTHOR]

Optical activities such as circular dichroism (CD) and optical rotatory dispersion (ORD) are manifested by almost all natural products. However, the CD is an extremely weak effect so that time-resolved CD spectroscopy has been found to be experimentally difficult and even impossible for vibrational CD with current technology. Here, we show that the weak-signal and nonzero background problems can be overcome by heterodyned spectral interferometric detection of the phase and amplitude of optical activity free-induction-decay (OA FID) field. A detailed theoretical description and a cross-polarization scheme for selectively measuring the OA FID are presented and discussed. It is shown that the parallel and perpendicular electric fields when the solution sample contains chiral molecules are coupled to each other. Therefore, simultaneous spectral interferometric measurements of the parallel and perpendicular FID fields can provide the complex susceptibility, which is associated with the circular dichroism and optical rotatory dispersion as its imaginary and real parts, respectively. On the basis of the theoretical results, to examine its experimental possibility, we present numerical simulations for a model system. We anticipate the method discussed here to be a valuable tool for detecting electronic or vibrational optical activity in femtosecond time scale. [ABSTRACT FROM AUTHOR]

Magnetoinductive waves propagating along a set of resonant metamaterial elements are studied under the condition when the wave travels round a closed circular path and the total phase shift is an integral multiple of 2π. The resonant frequency of the circulating wave is shown to be related to the resonant frequency of the element via the known dispersion relationship. The currents in the elements are determined with the aid of the impedance matrix when the excitation is by a rotating magnetic dipole located at the center of the structure. It is shown that the power taken out from one element in the loop may approach N times that from a single element, where N is the number of elements, provided the quality factor of the individual elements is sufficiently high and suitable modifications are made to nearby elements. Potential applications to magnetic resonance spectroscopy are discussed. [ABSTRACT FROM AUTHOR]

The complex linear response function, which can be employed for calculations of second-order molecular properties in regions of strong absorption, is here extended to encompass the mixed electric-dipole–magnetic-dipole polarizability. The mixed electric-dipole–magnetic-dipole polarizability determines the optical rotation and, when absorption is taken into account, the full anomalous optical rotatory dispersion (ORD) spectra of chiral molecules can be calculated using first-principle quantum-chemical methods. Gauge-origin independence of the results is ensured through the use of London atomic orbitals. To illustrate the importance of taking the absorption process properly into account, we here apply this methodology to the study of the anomalous ORD of hydrogen peroxide, 3R-methylcyclohexanone, 4R-1,1-dimethyl-[3]-(1,2)-ferrocenophan-2-on, and the D[sub 2] isomer of the C[sub 84] fullerene. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]