High Specific Rotation Research Articles

Nanometer thick iron garnet films with high Faraday rotation

Here we demonstrate nanometer thick iron garnet films with high specific Faraday rotation suitable for the magneto-optical applications. Bismuth-substituted iron garnet films of compositions Bi1Y2Fe5O12 and Bi1Tm2Fe5O12 deposited on gadolinium gallium garnet substrate are fabricated and characterized. Their thicknesses range from 2 to 10 nm, which corresponds to just a few crystal lattice constants. Spectacularly, Faraday rotation of the 2 nm thick Bi1Y2Fe5O12 film reaches 29.3deg/µm at 420 nm that is comparable to the single crystal micrometer thick films of similar composition. The film surface morphology by atomic force microscopy gives root mean square (RMS) roughness of the nanometer thick films as small as 0.13 nm that is also similar to the RMS of single crystal micrometer thick films. Moreover, the 3 nm thick Bi1Tm2Fe5O12 films demonstrate a pronounced effective uniaxial anisotropy. These all make the fabricated nanometer thick films very promising for their potential applications in magneto-optical devices and quantum technologies.

Thermoresponsive behavior of polyrotaxanes based on α-cyclodextrins threaded on poly(2-alkyl-2-oxazoline)-poly(ethylene glycol)-poly(2-alkyl-2-oxazoline) triblock copolymers

Polyrotaxanes with poly-2-alkyl-2-oxazoline blocking moieties have been successfully synthesized. The structure of the synthesized samples was confirmed by NMR spectroscopy, and the molar masses were measured by light scattering and GPC. The density of cyclodextrin rings on polyethylene glycol did not depend on the structure of poly-2-alkyl-2-oxazoline chains and ranged from 2 to 5. A high specific optical rotation of the prepared polyrotaxanes is found which is caused by the formation of hydrogen bonds between neighboring macrocycles. The behavior of water-salt solutions of synthesized polyrotaxanes depended on the size of the poly-2-alkyl-2-oxazoline side groups. Only polymers with poly-2-isopropyl-2-oxazoline and poly-2-n-propyl-2-oxazoline blocking moieties were thermoresponsive in aqueous solutions, and the phase separation temperature decreased at passage from a polymer with poly-2-isopropyl-2-oxazoline to a sample with poly-2-n-propyl-2-oxazoline. Aqueous solutions of polyrotaxanes with smaller side groups were molecularly dispersed at all temperatures, and the polymer with poly-2-butyl-2-oxazoline blocking chains did not dissolve in water.

Study on laser-induced damage of TbBiIG crystal at 1064 nm.

With the development of miniaturization of high-energy laser systems, a new Faraday rotator material must be studied to realize the miniaturization and integration of optical isolators. In this paper, high-quality (TbBi)3Fe5O12 (TbBiIG) and Ca-doped (TbBi)3Fe5O12 (Ca: TbBiIG) single crystal films with hundreds of microns thickness were grown by liquid phase epitaxy method on (111) oriented garnet substrate. The crystal structure, magneto-optical (MO), optical and laser induced damage properties were investigated in detail. We found that the (TbBi)3Fe5O12 film has outstanding magneto-optical and laser-induced damage properties. Optical and MO properties indicate that TbBiIG films have a high specific faraday rotation angle of 1452 deg/cm at 1310 nm, and 2812 deg/cm at 1064 nm, absorption coefficient (α) is 5.63 cm-1 and 15.7 cm-1 at 1310 nm and 1064 nm, respectively. The laser-induced damage threshold (LIDT) of TbBiIG irradiated by a multi-frequency laser is 8.91 J/cm2. The light absorption has a significant impact on LIDT value. Rare-earth ion doped iron garnet (RIG) material is a very potential MO material, which can greatly reduce the size and weight of optical isolators in the 1064 nm band.

The Underexplored Field of Lanthanide Complexes with Helicene Ligands: Towards Chiral Lanthanide Single Molecule Magnets

The effective combination of chirality and magnetism in a single crystalline material can lead to fascinating cross-effects, such as magneto-chiral dichroism. Among a large variety of chiral ligands utilized in the design and synthesis of chiral magnetic materials, helicenes seem to be the most appealing ones, due to the exceptionally high specific rotation values that reach thousands of deg·cm3·g−1·dm−1, which is two orders of magnitude higher than for compounds with chiral carbon atoms. Despite the sizeable family of transition metal complexes with helicene-type ligands, there are only a few examples of such complexes with lanthanide ions. In this mini-review, we describe the most recent developments in the field of lanthanide-based complexes with helicene-type ligands and summarize insights regarding the further exploration of this family of compounds towards multifunctional chiral lanthanide single molecule magnets (Ln-SMMs).

One-dimensional micro/nanomotors for biomedicine: delivery, sensing and surgery.

ABSTRACTThe rapid development of artificial micro/nanomachines brings promising strategies to overcome challenges in biomedicine, including delivery, sensing and surgery. One-dimensional (1D) micro/nanomotors are one of the most attractive micro/nanomachines due to their high specific surface area, powerful impetus and weak rotation diffusion. In this review, different propulsion mechanisms and motion control strategies of 1D micro/nanomotors are summarized, and recent efforts towards their fabrication methods and biomedical applications are discussed. We envision the multidisciplinary research efforts in the field of 1D micro/nanomotors will pave their way to practical applications in bioimaging and biomedicine.

Propriedades físicas de óleos essenciais: Uma ferramenta experimental no ensino de Química

As atividades experimentais representam recurso indiscutível no processo ensino – aprendizagem. Para alunos de graduação essas práticas se tornam mais eficientes quando tratadas de forma contextualizada. Métodos físicos de análises são alternativas simples, de baixo custo e rápidas na verificação da autenticidade de óleos essenciais com alto valor comercial, além de oferecer didática experimental que facilita o aprendizado de discentes dos cursos de química e áreas afins. Entre os parâmetros físicos destacam-se densidade, índice de refração e rotação óptica, que regulamentam a comercialização de fitoterápicos no Brasil. O presente estudo tem como objetivo fornecer alternativas de atividade experimental no ensino de química voltado para aplicação prática relacionada a regulamentação na comercialização de óleo essencial com alto valor agregado e produção científica na área. Os óleos essenciais foram obtidos por hidrodestilação. A densidade, o índice de refração e a rotação específica foram medidos em aparelhos específicos. O óleo essencial de candeeiro obteve maior rotação específica (-58,75° à -59,25°). O índice de refração foi maior para o pau-de-óleo (1,501560 ± 0,000000 nD). A densidade foi superior para o óleo essencial da marangaba vermelha (0,98 ±0,015 g/mL). Alterações na composição química de óleos essenciais apresentam mudanças significativas nas suas propriedades físicas, estas podem ser facilmente identificadas com a ajuda de aparelhos de fácil acesso e manuseio, garantindo eficiência das suas propriedades biológicas. Os estudantes, podem desenvolver habilidades profissionais para identificação dessas características, possibilidade esta, que representa motivação no processo de ensino-aprendizagem.

Enantiomeric resolution of helicochiral paddlewheel complexes and their infrared, Raman, UV–vis and X-ray optical activity

Linear polynuclear paddlewheel complexes-extended atom chains or metal strings-have provided attractive models for the study of metal-metal bonding, magnetism and conductivity since their discovery in the 1990s [1]. Their helicoidal chirality, arising from mutual steric hindrance of the 3-pyridyl protons, resulting in the twisting of the equatorial ligand around the axis (see figure), has been less studied. Nonetheless, in one of the few examples of chiral resolution, the obtained enantiomers of a trinickel complex showed a remarkably high specific rotation of 5000 deg•mL•g −1 •dm −1 [2], motivating us to seek a general technique for the chiral resolution of such racemates. We have developed a procedure based on anion exchange for the chiral resolution of [M3(dpa)4] 2+ salts (M = Co(II) or Ni(II), Hdpa = 2,2'-dipyridylamine). Homochiral arsenyl tartrate (AsT) salts promoted the selective crystallization of [-M3(dpa)4(MeCN)2](NBu4)2[-AsT]2, or [-M3(dpa)4(MeCN)2](NBu4)2[-AsT]2 in the P4212 space group. The enantiopure compounds demonstrated surprisingly large optical activities using UV-vis, Raman and infrared spectroscopy in solution and, for the cobalt derivatives, in the X-ray range at the Co K-edge in single crystals. An intense X-ray linear dichroism was observed in the orthoaxial crystal orientation, whereas it vanished in the axial confirmation, while the angular dependence of the circular dichroism spectra followed the expected (3cos 2 − 1) function, thus spectroscopically confirming the D4 crystal symmetry. X-ray magnetic circular dichroism and X-ray magnetochiral dichroism signals at the Co K-edge were not detected, likely due to a strongly delocalized spin density on the metal-metal bonded tricobalt core. Nevertheless, these results establish that chiral polynuclear paddlewheel complexes can be cleanly resolved using selective crystallization and demonstrate considerable optical activity in the infrared, UV-vis and X-ray energy ranges, thus potentially offering future perspectives in non-linear optics and asymmetric synthesis [3].

Synthesis, Structures, Resolution, and Chiroptical Properties of 1,16-Diaryl-Substituted Benzo[5]helicene Derivatives.

An efficient route to the synthesis of benzo[5]helicene derivatives functionalized on the interior side of the helix was developed, and resulted in a series of 1,16-diaryl-substituted benzo[5]helicene derivatives starting from easily available 7-methoxytetralone. X-ray crystal structures showed that the benzo[5]helicene derivatives had highly helical, twisted structures, and could all create hierarchical packing architectures with alternating P and M layers in the solid state. Moreover, seven pairs of enantiomers based on 1,16-diaryl-substituted benzo[5]helicene derivatives were also obtained by efficient resolution through HPLC with semipreparative chiral columns. The enantiomers all showed clear mirror-image circular dichroism (CD) spectra and high specific optical rotations, and their absolute configurations were determined by X-ray crystallography. Interestingly, a helical nanotubular structure was formed by the self-assembly of one enantiomer through halogen bonding. Furthermore, the enantiomers were found to have high racemization barriers and thermostability, which might be caused by the introduction of aryl substituents at the C1(C16) position.

Radical Polymerization of a Novel Methacrylamide Derivative

The radical polymerization of a novel methacrylamide derivative, N-[o-(4-ethyl-4, 5-dihydro-1, 3-oxazol-2-yl) phenyl] methacrylamide ((S)-EtOPMAM), was carried out to obtained optically active polymers. The polymer yield and the chiroptical behavior of the resultant polymers have been examined in detail by using IR and 1H NMR spectroscopies in comparison with our previous observation. The polymers showed relatively high molecular weights (Mn=8000-16000) and largest specific rotations ([α]25D =+120.6o). Particularly, the largest specific optical rotation of the polymer is almost the six times of the monomer.

Helical mesobenzanthrones: a class of highly luminescent helicenes

Diazotization of 3-aminophthalic acid in the presence of 7,9-di(1-naphthyl)-8H-cyclopent[a]acenaphthylen-8-one (9, a dinaphthyl analog of the common cyclopentadienone acecyclone), followed by treatment with thionyl chloride in toluene, gave 11-(1-naphthyl)-7H-fluorantheno[9,8,7-no]tetraphen-7-one (3), an orange luminescent helicene. Similar treatment of 1,3-di(1-naphthyl)-2H-cyclopenta[l]phenanthren-2-one (11, a dinaphthyl analog of phencyclone) gave 11-(1-naphthyl)-7H-triphenyleno[3,2,1-no]tetraphen-7-one (4), a highly luminescent derivative of hexahelicene. Both 3 and 4 are composed of four stable conformational isomers: two diastereomers, each of which contains a pair of enantiomers. One pure isomer of 3 and two isomers of 4 were ultimately obtained by supercritical fluid chromatography (SFC) of the mixtures on chiral supports. These isolated components exhibited high specific rotations and strong circular dichroism. Attempts to prepare a third helicene by diazotization of 3-aminophthalic acid in the presence of aceanthrenecyclone (5) gave no helicene products, but instead resulted in the oxidation of 5 to two unusual chiral diketones (7 and 8) whose structures were determined by X-ray diffraction.

Anionic Polymerization of Optically Active Propene Oxides Bearing Substituted N,N-Diphenylamino Moiety

Abstract A series of novel chiral propene oxides bearing substituted N,N-diphenylamino moiety were synthesized and anionically polymerized. Most of propene oxides gave polymers possessing high specific rotation and intensive circular dichroism (CD) signals, which were attributed to the helical conformation of the main chain. Poly(3-(4,4′-dimethoxy)diphenylaminopropene oxide) exhibited the highest specific rotation ([α ]36520 = −5400).

Radical Polymerizations of Optically Active Methacrylamides Having Oxazoline Moieties

A novel type of chiral N-substituted methacrylamide derivatives bearing an oxazoline pendant (OPMAM) had been synthesized. Radical polymerization were carried out to produced corresponding polymers with high specific rotation in moderate yields. The polymerization characteristics and the chiroptical behavior of the resultant polymers have been examined in detail by using HPLC and CD and UV-vis spectra. The polymers showed relatively high molecular weights(Mn=5000-15000). The abolutely value of the specific rotation of poly(OPMAM)s basically increased with increasing the molecular weights.

Polymerization and Characterization of N-[o-(4-phenyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl] Methacrylamide

A novel type of chiral methacrylamide derivative, N-[o-(4-phenyl-4,5-dihydro-1,3-oxazol-2-yl) phenyl]methacrylamide ((R)-PhOPMAM), was synthesized and radically polymerized to the corresponding polymers in moderate yields. The polymerization characteristics and the chiroptical behavior of the resultant polymers have been examined in detail by using IR and 1H NMR spectroscopies in comparison with our previous observation. The polymers showed relatively high molecular weights(Mn=5000-10000) and large specific rotations([α] 25D = -326.0°～-357.4°).

The reliability and utility of high reported specific rotations: reports and predictions of molecules with extremely high specific rotations, and high specific rotations suggest revision of the structures of huperzines E′ and F′

A search of the literature for all compounds with [α]D>1000 found 13 molecules with reliably determined specific rotations in excess of 6500, as judged by comparison with DFT-calculated values of [α]D for the same compounds, with a maximum [α]D −11,560 for a decacyclic helicene quinone. Several reports of [α]Ds ranging from 10,000 to 44,000 were judged to be spurious. On the basis of similar computational studies, several molecules are proposed that should have very high [α]Ds but relatively modest visible absorptions, unlike the current record holders, which have strong absorption near the sodium D line. In addition, the search found two natural products, huperzines E′ and F′, that have large reported [α]Ds (−4750 and −3182, respectively), that are inconsistent with their structures. However, computational studies found epimers of the reported structures that possess [α]Ds consistent with the reported chiroptical data.

Synthesis and Chiroptical Properties of Arylimines of Cholest-4-ene-3,6-dione

In the hope of generating a new class of materials with large optical rotations, various arylamines were condensed with cholest-4-ene-3,6-dione (2) to give 3-arylimino steroids. These compounds possess moderately high specific rotations ([α](D) ~300-800) and strong circular dichroism. One such derivative, 3-(4-methoxyphenylimino)cholest-4-en-6-one (3), crystallizes as the (E)-imine and upon dissolution undergoes mutarotation to an equilibrium mixture of (E)- and (Z)-isomers with a half-life of approximately 1 h at room temperature, as judged by both NMR spectroscopy and polarimetry.

Synthesis of chiral disulfides: potential reagents for enantioselective sulfurization

Synthesis of chiral phosphorothioates for use as antisense oligonucleotides might benefit from the use of chiral disulfides. This paper reports the synthesis of chiral analogs of phenylacetyl disulfide and of 5-methyl-3H-1,2,4-dithiazol-3-one from the same set of 2-arylalkanoic acids. The X-ray crystal structures of the disulfides derived from (R) and [S]-2-phenylpropanoic acid establish the stereochemistry and the helicity of these materials, and density functional theory calculations suggest that the high specific rotations can be due to preferred retention of this helicity in solution. Chiral HPLC showed that the final products were formed with enantiomeric purities from 86.1% to>99.9%.

Carbohydrates from Lamiaceae. VIII. α-Glucan from Scutellaria baicalensis roots

The homogeneous polysaccharide S b RP-1″ with MW 110 kDa was isolated during an investigation of water-soluble polysaccharides from Scutellaria baicalensis roots. Its aqueous solution gave a positive reaction with iodine and exhibited high specific rotation ([α]D +188.0°). Chemical, chromatographic, and spectral methods established that S b RP-1″ was a slightly branched glucan containing in the main chain α-(1 → 4)-glucopyranose units, 8.3% of which were branched at the C-6 atom with single α-glucopyranose units. Glucan S b RP-1″ was shown to exhibit immunostimulating activity using an azathioprine model of immunosuppression.

Optically Active Amphiphilic Polymer Brushes Based on Helical Polyacetylenes: Preparation and Self-Assembly into Core/Shell Particles

The article reports on the first preparation and self-assembly of a unique class of amphiphilic polymer brushes, which consist of hydrophobic optically active helical polyacetylene backbones and hydrophilic thermosensitive poly(N,N-dimethylamino-2-ethyl methacrylate) (PDMAEMA) side chains. The polymer brushes were prepared by a two-step process: substituted acetylene monomers underwent catalytic copolymerizations to form optically active helical polymer backbones bearing −Br moieties in side chains, which were employed as macroinitiators for the subsequent atom transfer radical polymerization (ATRP) of a vinyl monomer DMAEMA. High specific rotations and intense circular dichroism effects demonstrated that the polymer brushes possessed optical activities, derived from the helical polyacetylene backbones. The polymer brushes could self-assemble in water/tetrahydrofuran mixture solvent to form core/shell structured nanoparticles, which showed considerable optical activity originated in the helical polyacetyl...

Spiro Tröger’s Base Derivatives: Another Structural Phoenix?

Recently, naphthalenoide derivatives of Troger's base (TB) have become important as structural compartments of molecular tweezers and compounds with high specific rotation. The formation of TB derivatives and byproducts from naphthalen-2-amine, methyl 6-aminonaphthalene-2-carboxylate, and anthracen-2-amine was studied. It was discovered that the formation of a naphthalenoide TB derivative is followed by the formation of a unique structural isomer of TB: spiroTB.

Optical-activity anisotropy of ordered phases in cellulose acetates

The optical activity of anisotropic solutions of cellulose diacetate in nitromethane and dimethyl sulfoxide and of diand triacetate films with vitrified ordered structure has been studied. The systems under study are characterized by high specific optical rotation [α], suggesting formation of a cholesteric mesophase. The value of [α] is found to depend on the angle of rotation of the samples relative to the direction of the polarization vector of an incident light beam in the plane perpendicular to this beam (the anisotropy of optical activity). This dependence (indicatrix) shows an irregular pattern and, when plotted in Cartesian coordinates, can be described with a distorted sinusoid. The data on the resolution of indicatrices into harmonic constituents and isolation of contributions due to isotropic components and anisotropic components, each of which is determined by the structural element with the corresponding asymmetry, are analyzed.