Optical Rotatory Power Research Articles

Measurement and general modeling of optical rotation in anisotropic crystal

In this paper a novel method of computing the optical rotation of a parallel plated crystal is presented. The calculation is based on Fourier optics and solves generally the vectorial Maxwell's equations for both the refraction and propagation. It does not require the paraxial approximation, instead, the incident beam may have complex shape, not only a single plane wave. The medium may be anisotropic and optically active. We compare the simulation and experimental results which agree well within the error limit of the measurement. The comparison of the results enabled us to determine the optical rotatory power. The main advantage of the method is that it computes accurately the polarization in case of arbitrary incident angle. The primary purpose of the model is to calculate accurately the electric fields for the different polarizations in case of acousto-optical cells of various orientations.

Synthesis of Optically Active Regioregular Polythiophenes and Their Self-Organization at the Air–Water Interface

Regioregular polythiophenes containing an optically active substituent in the third position of the thiophene ring, head-to-tail poly(3-[2-((S)-1-methyloctyloxy)ethyl]thiophene)s (HT-P(S)MOETs), were synthesized using highly reactive zinc. For comparison, HT-P(R)MOET and achiral HT-P(±)MOET also were synthesized from R-type monomers and racemic monomers, respectively. The HT-PMOET possessed greater than 95% head-to-tail coupling with a weight-average molecular weight (Mw) between 1.96 × 10(4) and 2.94 × 10(4). The polymers were characterized using (1)H and (13)C NMR, optical rotatory power measurements, circular dichroism (CD), and UV-vis spectroscopy. X-ray diffraction patterns of the cast films demonstrated that regioregular HT-PMOET possessed a strong tendency to self-assemble into highly ordered, crystalline structures. The HT-P(S)MOET and HT-P(R)MOET showed strong Cotton effects, while HT-P(±)MOET showed very weak Cotton effects. The presence of a circular dichroism effect indicated that the side chain chirality induced optical activity in poly(thiophene) main chains. The monolayer formation of HT-PMOET spread on the water surface was characterized using a pressure-area (π-A) isotherm. The molecular areas of HT-P(S)MOET and HT-P(R)MOET molecules on the water surface were 33.5 and 32.9 Å(2), respectively, at 10 °C, which were larger than that of HT-P(±)MOET (27.9 Å(2)), suggesting that optically active HT-PMOET expanded because of the chiral repulsion between side chains. Multilayer films of HT-PMOET were prepared by repeating horizontal deposition of the monolayer on the water surface. The multilayer films of optically active HT-PMOET obtained showed stronger Cotton effects than did the cast films. In addition, electrical conductivities of HT-PMOET multilayer films were superior to those of spin-coated films. Head-to-tail poly(3-[2-((S)-1-methylpropyloxy)ethyl]thiophene) (HT-P(S)MPET), which contained shorter side chain lengths compared to HT-P(S)MOET, also was synthesized. The CD intensities of HT-P(S)MPET multilayer films were smaller than those of HT-P(S)MOET multilayer films, suggesting that the optically active side-chain length is critically important to the optically active self-assembly.

17.3L: Late‐News Paper: Enhancing the Contrast Ratio of Blue Phase LCDs

AbstractExperimental evidence proves that polymer‐stabilized blue phase liquid crystal is not perfectly optically isotropic. The optical rotatory power (ORP) of double twist cylinders causes the polarization axis of the transmitted light to rotate a small angle, and leaks through the crossed polarizers. Rotating the analyzer by ∼2o to correct this ORP can improve the contrast ratio by 3X.

Optical Activity of Langatate Crystals

A calculation technique based on the polarizability theory for optical activity (OA) is applied to derive optical rotatory power (ORP) for the La3Ga5.5Ta0.5O14 (LGT). Dispersions of both the ordinary and extraordinary refractive indices and the ORP are calculated. A comparison of the observed and calculated OA parameters confirms validity of our theoretical calculations.

Optical rotatory power of polymer-stabilized blue phase liquid crystals

Macroscopically, a polymer-stabilized blue phase liquid crystal (BPLC) is assumed to be an optically isotropic medium. Our experiment challenges this assumption. Our results indicate that the optical rotatory power (ORP) of some nano-scale double-twist cylinders in a BPLC composite causes the polarization axis of the transmitted light to rotate a small angle, which in turn leaks through the crossed polarizers. Rotating the analyzer in azimuthal direction to correct this ORP can greatly improve the contrast ratio. A modified De Vries equation based on a thin twisted-nematic layer is proposed to explain the observed phenomena.

Enantioselective Demethylation of Nicotine as a Mechanism for Variable Nornicotine Composition in Tobacco Leaf

Nicotine and its N-demethylation product nornicotine are two important alkaloids in Nicotiana tabacum L. (tobacco). Both nicotine and nornicotine have two stereoisomers that differ from each other at 2'-C position on the pyrrolidine ring. (S)-Nicotine is the predominant form in the tobacco leaf, whereas the (R)-enantiomer only accounts for ∼0.2% of the total nicotine pool. Despite considerable past efforts, a comprehensive understanding of the factors responsible for generating an elevated and variable enantiomer fraction of nornicotine (EF(nnic) of 0.04 to 0.75) from the consistently low EF observed for nicotine has been lacking. The objective of this study was to determine potential roles of enantioselective demethylation in the formation of the nornicotine EF. Recombinant CYP82E4, CYP82E5v2, and CYP82E10, three known tobacco nicotine demethylases, were expressed in yeast and assayed for their enantioselectivities in vitro. Recombinant CYP82E4, CYP82E5v2, and CYP82E10 demethylated (R)-nicotine 3-, 10-, and 10-fold faster than (S)-nicotine, respectively. The combined enantioselective properties of the three nicotine demethylases can reasonably account for the nornicotine composition observed in tobacco leaves, which was confirmed in planta. Collectively, our studies suggest that an enantioselective mechanism facilitates the maintenance of a reduced (R)-nicotine pool and, depending on the relative abundances of the three nicotine demethylase enzymes, can confer a high (R)-enantiomer percentage within the nornicotine fraction of the leaf.

Structure effect on the absorption and circular dichroism spectra of Sm14B6Ge2O34 crystals

The spectroscopic and chiroptical properties of rare-earth-rich borate germanate crystals of composition Sm14B6Ge2O34 have been studied for the first time. The absorption and circular dichroism spectra of the crystals have been measured. For some of the f-f transitions involved, we have calculated the dipole strength and optical rotatory power.

Generalization of the crystalline optical activity dispersion relations for arbitrary propagation direction of electromagnetic waves

This study suggests an alternative method concerning the derivation of the dispersion relations in crystalline optical activity for the arbitrary propagation direction of the electromagnetic waves. The solution is based on the dipole–dipole interactions between the valence electrons that are represented by the harmonic oscillators. The following theoretical description of the optical activity uses the modified Rosenfeld relations. The rotational strengths of the quantum-mechanical transitions in the normal modes of vibrations are obtained following simple calculations of a sum of two independent components. The specific model of three coupled oscillators, which seems to be sufficient for the description of the optical activity of crystals having space groups of symmetry D34 or D36, is solved as the example and the dispersion relations are derived for the optical rotatory power and circular dichroism. The results are applied on the example of trigonal selenium, for which the optical rotatory power ratio in the direction perpendicular and in the direction parallel to the optic axis is calculated. The calculated relation is compared with a similar relation derived by Chandrasekhar. The validity of both relations is then discussed.

Synthesis and Characterization of Poly (L-Lactic acid) Containing the Azobenzene Mesogens

A series of azobenzene containing group Poly (L-lactic acid) (PLLA) were synthesized by Ring-Opening Polymerization of L-lactide (L-LA) catalysted by Sn (Oct)2initiated by alcohol-OH containing the azobenzene chromophores. Their molecular weights were well controlled by the feed ratio as characterized by Gel Permeation Chromatography (GPC) and1H NMR Spectrometry and agreed well with theoretical values. The thermal properties and liquid crystal phases were investigated by Differential Scanning Calorimetry (DSC), polarized optical microscopy (POM) and X-ray Diffraction (XRS) measurements. Cis-trans photoisomerization behavior of the polymers in the solutions and the films were studied with UV irradiation. By the Circular Dichroism Spectroscopy (CD) characterization of the solutions and films of the polymer, the PLLA segments show huge optical rotation power in helical structure.

Thermal and Optical Properties of Main Chain Polymer Compose of Oligo-L-LA Segments and Biphenol Group

Thermal properties and phase behavior of series of main chain copolymers containing oligomeric-L-LA segments (OLLA) and biphenol groups were synthesized and characterized. OLLA segments were prepared by ring opening polymerization of L-LA initiated by biphenol mesogens with active HO-group and then polymerized to form main chain polymer by the reaction pentanedioyl dichloride with the-OH groups at the free end of OLLA. Their phase behaviors were studied by using DSC and POM. XRD measurements revealed the formation of layered structures. CD measurements were used to measure the helical structure and the optical rotation power of the main chain polymers.

Mesophase and Optical Properties of Side Chain Copolyacrylate with Mesogens and OLLA Segments Side Chains

Thermal properties and phase behaviors of series of newly synthesized copolyacrylate esters with oligomeric-L-LA (OLLA) segments (DP = 10-40) and mesogens as side chains were characterized. The OLLAs prepared by ring opening polymerization of L-LA with active HO-group were modified to form polymerizable acrylate esters and then copolymerized with polymerizable mesogens. The thermal behaviors of these copolyacrylate esters were studied by DSC and POM measurements and phase structures by XRD measurements. The mesogens showed very good induce effect on the formation of layered structures. CD measurements were used to determine the helical structure and the optical rotation power of the side chain copolyacrylate esters.

Ent-2′-epi-Orobanchol and Its Acetate, As Germination Stimulants for Striga gesnerioides Seeds Isolated from Cowpea and Red Clover

Striga gesnerioides is a root parasitic weed of economic significance to cowpea (Vigna unguiculata) crops in Western Africa. Seeds of the parasite germinate in response to cowpea root exudates. Germination stimulants for the seeds were isolated from the hydroponic culture filtrate of cowpea, and their structures were unambiguously determined as (-)-(3aR,4R,8bR,2'R)-ent-2'-epi-orobanchol and (+)-(3aR,4R,8bR,2'R)-ent-2'-epi-orobanchyl acetate, on the basis of mass, CD, and (1)H NMR spectra; optical rotatory power; and chromatographic behavior on HPLC. The alcohol was first isolated and identified from the cowpea root exudates, and the acetate may be the same compound that had been previously isolated from the exudates and designated as alectrol. Identity of the stimulants produced by cowpea to those produced by red clover (Trifolium pratense) was confirmed.

Relationships between the stereochemistry and biological activity of fungal phytotoxins

Toxins produced by phytopathogenic fungi assume great importance because of their involvement in several plant diseases. Although such pathogens are known to have seriously damaged crops, forest, and environmental resources, they represent a very important tool to develop new environmentally friendly herbicides and fungicides. This review deals with the relationships between the biological activity of some phytotoxins produced by pathogenic fungi for major forest plants and for damaging weeds and their stereochemistry. In particular, the methods used to determine their relative and/or absolute configuration will be illustrated. These include the application of Mosher's and Murata's methods, X-ray diffractometric analysis, circular dichroism, and the use of computational methods to determine the theoretical optical rotatory power as well as the CD spectrum. The importance of determining the absolute configuration to achieve the total synthesis of some phytotoxins, interesting for their potential practical application, is also discussed.

Establishment of phase diagram of a chiral smectic liquid crystal

Chiral smectic liquid crystals are well known to exhibit the following sequence of phases as the temperature is increased: Sm- C A ⁎ , Sm- C Fi 1 ⁎ , Sm- C Fi 2 ⁎ , Sm- C ⁎ and Sm- C α ⁎ . Surprisingly, some compounds appear in several publications to present other tilted phases, which not only do not belong to the previous series but change from one paper to the other although the studied compound is the same. Such is the chiral smectic liquid crystal ( R) or ( S)-12OF1M7 that we have re-synthesized and studied with various techniques: dielectric spectroscopy, optical rotatory power, conoscopic measurements and electro-optic properties. Our conclusion is that this compound presents the ordinary phase sequence at the exception of the Sm- C α ⁎ phase. In addition, the ( E– T) phase diagram of this compound was established.

Theoretical Study of the 1:1 and 2:1 (Homo- and Heterochiral) Complexes of XOOX′ (X, X′ = H, CH3) with Lithium Cation

A theoretical study of the 1:1 and 2:1 complexes of XOOX' (X, X' = H, CH(3)) with the lithium cation has been carried out by means of ab initio computational methods up to the MP2/aug-cc-pVTZ level. The optical rotatory power and NMR parameters (absolute chemical shielding and indirect coupling constants) have been calculated. In addition, the racemization barriers within the complexes formed have been evaluated. Special attention has been paid concerning the differences between the 2:1 homo- and heterochiral complexes.

Observations on the intravenous toxicity and chelating activity of sodium stibogluconate.

Abstract The optical activity, calcium chelating power and intravenous toxicity, but not the leishmanicidal activity, of a sodium stibogluconate solution varies with pH and age. As the optical rotatory power increases, the calcium chelating property decreases, and the solution becomes less toxic. Solutions of sodium stibogluconate injected intravenously into mice produce hypocalcaemia, which may be the cause of death. Production of hypocalcaemia may be a phenomenon common to many substances with chelating powers, a factor to be considered in the design of comparative toxicity tests.

The intertwined history of polarimetry and ellipsometry

Ellipsometry and reflection polarimetry are almost synonymous. Therefore it is not surprising that ellipsometry and polarimetry share a common history which is that of optical polarization. The discoveries in the late 1600s by Bartholinus and Huyghens of double refraction by Iceland spar and the unusual properties of the twin beams thus generated presented insurmountable difficulties for the entrenched corpuscular-ray theory of Newton and caused research on polarization to remain stagnant in the 1700s. Major breakthroughs came in the early 1800s when Malus discovered polarization of light by reflection and his cosine-squared law and Fresnel and Arago enunciated their laws of interference of polarized light that helped establish the transverse vector nature of luminous vibrations. Important further research immediately followed on optical rotatory power by Arago, Biot, and Pasteur that ushered fundamental and practical applications of polarimetry in chemistry and biology. Fresnel deserves to be recognized as a founder of ellipsometry by virtue of his laws of reflection of polarized light at interfaces between dissimilar media and his identification and production of circular and elliptical polarization. The later part of the 19th century witnessed significant discoveries of magneto-optic and electro-optic effects by Faraday, Kerr, and Pockels that greatly enriched polarization optics and physics. The 1896 discovery of the Zeeman effect launched the exciting field of solar polarimetry. The 1864 crown achievement of Maxwell's electromagnetic (EM) theory provided a unified framework for the analysis of polarization phenomena across the entire EM spectrum.

Synthesis and characterization of side chain polymer with helical PLLA segments containing mesogenic end group

Series of mesogenic biphenol derivatives HO6OPPOn (n = 4,6,8) were prepared by asymmetric reaction and purified. Then HOLAxO6OPPOn were prepared with controlled molecular weights by adjusting the feed ratios of HO6OPPOn, SnOct2 catalyst and LLA by Ring-Opening Polymerization. P-AOLAxO6OPPOn materials were obtained in high yields by the free radical polymerization of polymerizable macromonomers of AOLAxO6OPPOn synthesized by esterization of HOLAxO6OPPOn with acrylic acid in the presence of DCC/DMAP. Their molecular weights were characterized by 1H NMR and GPC. Differential Scanning Calorimeter method and Polarized Optical Microscopy method were used to study their thermal behaviors. Both AOLAxO6OPPOn and P-AOLAxO6OPPOn materials are found to form LCs with increased Tg, Tm and Ti with longer O-LLA segment length. Polymerization of AOLAxO6OPPOn also resulted in the increase of Tg, Tm and Ti. X-ray diffraction measurements revealed the presence of smectic phase in these materials. The O-LLA segments are in helical structure from CD spectra and this makes the resulting polymer materials good candidate of optical materials for huge optical rotation power.

Model of the coherent magneto-optical dynamics in a single chiral carbon nanotube

A theoretical framework and dynamical model for description of the natural optical activity and Faraday rotation in an individual chiral single-walled carbon nanotube in the highly nonlinear coherent regime is proposed. The model is based on a discrete-level representation of the optically active states near the band edge. Chirality is modelled by a system Hamiltonian corresponding to energy-level configurations, specific for each handedness, that are mirror reflections of each other. An axial magnetic field is introduced through the Aharonov-Bohm and Zeeman energy-level shifts.The time evolution of the quantum system is studied using the coherent vector Maxwell-pseudospin equations. Giant natural and magneto-optical gyrotropy, exceeding the one of the artificial photonic metamaterials, is numerically demonstrated for a single (5,4) carbon nanotube and an estimate of the magnitude of the natural circular dichroism and specific optical rotatory power is obtained. The model provides a framework for investigation of chirality and magnetic field dependence of the ultrafast nonlinear optical response of a single carbon nanotube.

Coherent magneto-optical polarisation dynamics in a single chiral carbon nanotube

We propose a theoretical framework and a dynamical model for the description of the natural optical activity and the Faraday rotation in an individual chiral single-walled carbon nanotube in the highly nonlinear coherent regime. The model is based on a discrete-level representation of the optically active states near the band edge. Chirality is modelled by a system Hamiltonian corresponding to energy-level configurations, specific for each handedness, that are mirror reflections of each other. An axial magnetic field is introduced through the Aharonov–Bohm and Zeeman energy-level shifts.The time evolution of the quantum system following an ultrafast circularly polarised optical excitation is studied using the coherent vector Maxwell pseudospin equations. Giant natural and magneto-optical gyrotropy, exceeding the one of the artificial photonic metamaterials, is numerically demonstrated for a single (5, 4) carbon nanotube and an estimate of the magnitude of the natural and magneto-chiral circular dichroism and specific optical rotatory power is obtained. The model provides a framework for the investigation of chirality and magnetic field dependence of the ultrafast nonlinear optical response of a single carbon nanotube.