Magnetically controllable random laser in ferromagnetic nematic liquid crystals.

This paper first reports random laser action in dye-doped ferromagnetic nematic liquid crystals, which act as a randomly distributed cavity. The random laser intensity of the ferromagnetic nematic liquid crystals can be controlled by a weak magnetic field (∼1 mT). Moreover, the magnetic switching of random laser is attributed to the direction and polarization dependent emission of light in the ferromagnetic nematic liquid crystals in an external magnetic field.

Helicity Control of Supramolecular Gel Fibers Consisting of an Achiral NiII Complex in a Chiral Nematic Solvent.

The supramolecular chirality of aggregates consisting of achiral trans-bis(salicylaldiminato)NiII complex 1 bearing long alkyl chains can be generated and controlled precisely in a chiral nematic liquid-crystalline (LC) solvent, whereas the complex naturally forms achiral gel fibers in achiral nematic LC solvents and crystals in nonmesogenic solvents. The direction and intensity of the helicity of the gel fibers of 1 in the LC gel state can be adjusted by means of the nature of the helical twisting and the concentration of the chiral dopants. Helicity control was precisely detected in the circular dichroism (CD) spectra of LC gels and by direct SEM observation of the dried gel fibers. XRD analysis revealed that the flexibility of the herringbone-based lamellar alignment of this complex is the key to the LC-specific gelation and helicity control of the gel fibers.

Unique Superparamagnetic-like Behavior Observed in Non-π-delocalized Nitroxide Diradical Compounds Showing Discotic Liquid Crystalline Phase.

A unique superparamagnetic-like behavior and a large "positive magneto-LC effect" were observed in the solid phases and the hexagonal columnar (Colh ) liquid crystalline (LC) phase, respectively, of novel achiral non-π-delocalized nitroxide diradical compounds (R,S)-1, which showed polymorphism in the solid phases (solids I and II). The SQUID magnetization measurement revealed that (1) (R,S)-1 containing a small amount of racemic diastereomers (R*,R*)-1 possessed an unusual and large temperature-independent magnetic susceptibility (χTIM >0) component in the original nanocrystalline solid I that was responsible for the observed superparamagnetic-like behavior under low magnetic fields and did not arise from the contamination by extrinsic magnetic metal or metal ion impurities, besides ordinary temperature-dependent paramagnetic susceptibility (χpara >0) and temperature-independent diamagnetic susceptibility (χdia <0) components, (2) a large increase in molar magnetic susceptibility (χM ) (positive magneto-LC effect) that occurred at the solid I-to-liquid crystal transition upon heating was preserved as an additional χTIM increase in the resulting polymorphic nanocrystalline solid II by cooling, and (3) such unique magnetic phenomena were induced by thermal processing for (R,S)-1 or by adding a small amount of (R*,R*)-1 to (R,S)-1 as the impurity.

Distribution of lignans and lignan mono/diglucosides within Ginkgo biloba L. stem.

To investigate the biosynthetic pathways and regulatory mechanisms of lignans in plants, the actual distributions of lignans and lignan glucosides in flash-frozen stems of Ginkgo biloba L. (Ginkgoaceae) were studied using cryo time-of-flight secondary ion mass spectrometry coupled with scanning electron microscopy (cryo-TOF-SIMS/SEM). Four lignans and four lignan glucosides were successfully characterized. Quantitative HPLC measurements were conducted on serial tangential sections of freeze-fixed ginkgo stem to determine the amount and approximate distribution of lignan and lignan glucosides. (-)-Olivil 4,4'-di-O-ß-d-glucopyranoside (olivil DG) was the most abundant lignan glucoside in ginkgo and was distributed mainly in the phloem, ray parenchyma cells, and pith. The comparative accumulation of olivil DG revealed its possible transport pathways and storage sites in ginkgo. Although not all relevant enzymes have been identified, understanding the distributions of lignan and lignan glucosides in ginkgo stems provides significant insight into their biological functions.

Thermal Molecular Motion Can Amplify Intermolecular Magnetic Interactions.

Against a sensible expectation that molecular mobility in fluids generally disrupts magnetic orderings that depend on intermolecular interactions, some molecular compounds with isolated electrons, which are called radicals, exhibit the increase of magnetic susceptibility in melting. Here we first propose a simple model to explain the thermomagnetic anomaly unique to fluids; the effect of the magnetic interactions in each of the contacts could be accumulated on each of the molecular spins as if the molecular motion amplified the first coordination number of each molecule hundredfold. The huge coordination number theoretically guarantees the retention of memory of interactions at equilibrium; molecules might be able to conserve the memory of molecular conformations, configurations, electric charges, energies as well as magnetic memory with each other.

Microscopic distribution of syringin in freeze-fixed Syringa vulgaris stems.

Monolignols are precursors of lignin, and their glucosides are often found in plants. Glucosylation creates water-soluble and chemically stable monolignols by protecting the phenolic hydroxyl group. To discuss the role of sinapyl alcohol glucoside, syringin, in planta, the cellular distribution of syringin in the transverse and radial surfaces of quick-frozen stems of Syringa vulgaris L. (lilac) was visualized by cryo-time-of-flight secondary ion mass spectrometry and scanning electron microscopy (cryo-TOF-SIMS/SEM) analyses. The amount and rough distribution of syringin were confirmed by high-performance liquid chromatography measurements using serial tangential sections of freeze-fixed lilac stems. The syringin distribution was also discussed with reference to the tissue classification from microscopic observations. Syringin was mainly found in the phloem region. In the xylem region, syringin was evenly distributed irrespective of the cell type from the cambial zone to the early differentiating stage region and selectively distributed in vessels in the later differentiating stage region. After the lignification of wood fibers, syringin was found in rays and some vessels in the initial part of the annual rings. Previously, artificially administered isotope-labeled syringin was shown to be assimilated into lignin in the differentiating xylem region. Based on this, our present data showing syringin storage in the differentiating xylem region and its variation depending on the lignification stage suggest that syringin works as a lignin precursor. Additionally, detection of syringin in vessels and rays indicates intercellular transportation of syringin in lilac stems.

Measuring Magnetically-Tuned Ferroelectric Polarization in Liquid Crystals.

Materials showing coupling phenomena between magnetism and (ferro)electricity, i.e., magnetoelectric effects, have attracted a great deal of attention due to their potential applications for future device technologies such as sensors and storage. However, conventional approaches, which usually utilize materials containing magnetic metal ions (or radicals), have a major problem: only a few materials have been found to show the coupling phenomena at room temperature. Recently, we proposed a new approach to achieve room-temperature magnetoelectrics. In contrast to conventional approaches, our alternative proposal focuses on a completely different material, a "liquid crystal", free from magnetic metal ions. In such liquid crystals, a magnetic field can be utilized to control the orientational state of constituent molecules and the corresponding electric polarization through magnetic anisotropy of the molecules; it is an unprecedented mechanism of the magnetoelectric effect. In this context, this paper provides a protocol to measure ferroelectric properties induced by a magnetic field, that is, the direct magnetoelectric effect, in a liquid crystal. With the method detailed here, we successfully detected magnetically-tuned electric polarization in the chiral smectic C phase of a liquid crystal at room temperature. Taken together with the flexibility of constituent molecules, which directly affects the magnetoelectric responses, the introduced method will serve to allow liquid crystal cells to acquire more functions as room-temperature magnetoelectrics and associated optical materials.

Molecular Mobility Effect on Magnetic Interactions in All-Organic Paramagnetic Liquid Crystal with Nitroxide Radical as a Hydrogen-Bonding Acceptor.

We synthesized new chiral all-organic liquid crystalline (LC) compounds with nitroxide (NO) and hydroxy (OH) groups, which form intermolecular hydrogen bonds between the NO and OH groups. The LC compounds show hexagonal columnar phases at room temperature, which solidify as LC glasses at low temperature. The experimental magnetic susceptibility of each of the compounds in the LC and isotropic phases is larger than that theoretically estimated on the simple assumption about the amount of the spins, whereas it accords with the theoretical one in the LC glass state. It is called magneto-LC effects. The difference between experimental and theoretical magnetic susceptibilities gradually increases as temperature increases through the LC glass state-to-LC phase transition. It suggests that molecular mobility is one of the origins of the magneto-LC effects.

Distribution of coniferin in freeze-fixed stem of Ginkgo biloba L. by cryo-TOF-SIMS/SEM.

To clarify the role of coniferin in planta, semi-quantitative cellular distribution of coniferin in quick-frozen Ginkgo biloba L. (ginkgo) was visualized by cryo time-of-flight secondary ion mass spectrometry and scanning electron microscopy (cryo-TOF-SIMS/SEM) analysis. The amount and rough distribution of coniferin were confirmed through quantitative chromatography measurement using serial tangential sections of the freeze-fixed ginkgo stem. The lignification stage of the sample was estimated using microscopic observations. Coniferin distribution visualized at the transverse and radial surfaces of freeze-fixed ginkgo stem suggested that coniferin is stored in the vacuoles, and showed good agreement with the assimilation timing of coniferin to lignin in differentiating xylem. Consequently, it is suggested that coniferin is stored in the tracheid cells of differentiating xylem and is a lignin precursor.