Paramagnetic Liquid Research Articles

All-organic liquid crystalline radicals with a spin unit in the outer position of a bent-core system

All-organic paramagnetic liquid crystals offer the advantage of a long-range order of liquid crystalline phases and the magnetic properties of the individual molecules.

Activation of Peroxymonosulfate by Benzoquinone: A Novel Nonradical Oxidation Process.

The reactions between peroxymonosulfate (PMS) and quinones were investigated for the first time in this work, where benzoquinone (BQ) was selected as a model quinone. It was demonstrated that BQ could efficiently activate PMS for the degradation of sulfamethoxazole (SMX; a frequently detected antibiotic in the environments), and the degradation rate increased with solution pH from 7 to 10. Interestingly, quenching studies suggested that neither hydroxyl radical (•OH) nor sulfate radical (SO4•-) was produced therein. Instead, the generation of singlet oxygen (1O2) was proved by using two chemical probes (i.e., 2,2,6,6-tetramethyl-4-piperidinol and 9,10-diphenylanthracene) with the appearance of 1O2 indicative products detected by electron paramagnetic resonance spectrometry and liquid chromatography mass spectrometry, respectively. A catalytic mechanism was proposed involving the formation of a dioxirane intermediate between PMS and BQ and the subsequent decomposition of this intermediate into 1O2. Accordingly, a kinetic model was developed, and it well described the experimental observation that the pH-dependent decomposition rate of PMS was first-order with respect to BQ. These findings have important implications for the development of novel nonradical oxidation processes based on PMS, because 1O2 as a moderately reactive electrophile may suffer less interference from background organic matters compared with nonselective •OH and SO4•-.

PA23 シアノ基を有する新規常磁性ニトロキシドラジカル液晶の合成と相転移挙動(液晶化学材料,ポスター発表,2015年日本液晶学会討論会)

PA23 シアノ基を有する新規常磁性ニトロキシドラジカル液晶の合成と相転移挙動(液晶化学材料,ポスター発表,2015年日本液晶学会討論会)

Synthesis and Characterization of a New Series of Paramagnetic Ferroelectric Liquid Crystalline Nitroxide Radicals

A new series of all-organic liquid-crystalline (LC) chiral radical compounds, trans-1-alkoxyphenyl-4-[(4-(4-alkoxyphenyl)-2,5-dimethylpyrrolidine-1-oxy-2-yl)-benzylideneamino]benzenes (1) with various alkyl chains, containing a chiral nitroxide unit in the mesogen core were synthesized and their LC properties were fully characterized. The enantiomerically enriched compounds (2S,5S)-1 showed N*, TGBA*, SmA* and SmC* phases, while the racemates (±)-1 exhibited N, SmA and SmC phases. The phase transition behavior and the ferroelectric properties of the SmC* phase of (2S,5S)-1 differed from those of previously reported analogues with an ester group as a substitute for the imino group of (2S,5S)-1. Some of the (2S,5S)-1 series showed a temperature-dependent spontaneous polarization PS (θ) inversion. We discuss the origin of this difference in terms of their molecular structures optimized by molecular orbital calculations. The phase transition behavior supports the hypothesis that the large ϕ, which is defined as the angle between the molecular long axis (one of the principal axes of inertia) and the direction of the dipole moment in each molecule, results in the stabilization of the SmA* (SmA) phase.

Susceptibility cancellation of a microcoil wound with a paramagnetic-liquid-filled copper capillary

Even though microcoils improve the sensitivity of NMR measurement of tiny samples, magnetic-field inhomogeneity due to the bulk susceptibility effect of the coil material can cause serious resonance-line broadening. Here, we propose to fabricate the microcoil using a thin, hollow copper capillary instead of a wire and fill paramagnetic liquid inside the capillary, so as to cancel the diamagnetic contribution of the copper. Susceptibility cancellation is demonstrated using aqueous solution of NiSO4. In addition, the paramagnetic liquid serves as coolant when it is circulated through the copper capillary, effectively transferring the heat generated by radiofrequency pulses.

Conduction electron spin resonance in the α-Yb1−xFexAlB4 (0 ⩽ x ⩽ 0.50) and α-LuAlB4 compounds

β-YbAlB4 has become one of the most studied heavy fermion systems since its discovery due to its remarkable physical properties. This system is the first reported Yb-based heavy-fermion superconductor (HFS) for which the low-T superconducting state emerges from a non-fermi-liquid (NFL) normal state associated with quantum criticality Nakatsuji et al 2008 Nature 4 603. Additionally, it presents a striking and unprecedented electron spin resonance (ESR) signal which behaves as a conduction electron spin resonance (CESR) at high temperatures and acquires features of the Yb3+ local moment ESR at low temperatures. The latter, also named Kondo quasiparticles spin resonance (KQSR), has been defined as a 4f-ce strongly coupled ESR mode that behaves as a local probe of the Kondo quasiparticles in a quantum critical regime, Holanda et al 2011 Phys. Rev. Lett. 107 026402. Interestingly, β-YbAlB4 possesses a previously known structural variant, namely the α-YbAlB4, phase which is a paramagnetic Fermi liquid (FL) at low temperatures Macaluso et al 2007 Chem. Mater. 19 1918. However, it has been recently suggested that the α-YbAlB4 phase may be tuned to NFL behavior and/or magnetic ordering as the compound is doped with Fe. Here we report ESR studies on the α-Yb1−xFexAlB4 (0 ⩽ x ⩽ 0.50) series as well as on the reference compound α-LuAlB4. For all measured samples, the observed ESR signal behaves as a CESR in the entire temperature range (10 K ≲ T ≲ 300 K) in clear contrast with what has been observed for β-YbAlB4. This striking result indicates that the proximity to a quantum critical point is crucial to the occurrence of a KQSR signal.

Terminal Fluorinated Nitroxide Radical Liquid Crystalline Compounds

We have synthesized a new series of all-organic paramagnetic liquid crystalline (LC) compounds, which include a five-membered ring nitroxide radical (NR) moiety in the mesogen core and fluorine atoms as terminal substituents. These new compounds are the structural analogs of the previously reported NR-LC compounds, and showed remarkable fluorine substituent effects. The introducing fluorine atom into terminal unit stabilizes nematic phase. However, an excess of fluorination leads to the destabilization of nematic phase.

Dielectric and magnetic anisotropy of a nematic ytterbium complex

The sign and the magnitude of the dielectric anisotropy of an ytterbium-based paramagnetic nematic liquid crystal complex, namely, tris[1-(4-(4-propylcyclohexyl)phenyl)octane-1,3-dione]-[5,5'-di(heptadecile)-2,2'-bipyridine]ytterbium, are determined. The temperature dependence of the permittivity components of the complex is obtained in the temperature range of a nematic phase. The sign of the anisotropy of the magnetic susceptibility of this compound is experimentally determined.

Ferronematics Based on Paramagnetic Nitroxide Radical Liquid Crystal

We have prepared novel ferronematics based on a paramagnetic liquid crystalline (LC) material. Our ferronematics can disperse a higher volume fraction of magnetic nanoparticles compared to classical ferronematics because paramagnetic nature of the host LC material prevents the aggregation of magnetic nanoparticles. The interactions between the magnetic nanoparticles and the LC material enhance a magnetic anisotropy of ferronematics and improve the magnetic responsivity.

1-Ethyl-2,3-dimethylimidazolium paramagnetic ionic liquids with 3D magnetic ordering in its solid state: synthesis, structure and magneto-structural correlations

We present two novel paramagnetic ionic liquids, Edimim FeX4 (X = Cl and Br), which display a three-dimensional magnetic ordering below 10 K. Exhaustive and systematic studies of the magneto-structural correlations have been performed.

A room temperature spin crossover ionic liquid.

Two new paramagnetic ionic liquids (ILs) comprising a mononuclear iron(III) or manganese(III) complex cation, charge balanced by a dicyanamide anion are reported which show a range of spin states. Both are liquids at room temperature and the Fe(III) based IL exhibits a spin crossover close to 300 K. The spin crossover profile is independent of the solvation, and is both air and moisture stable.

ChemInform Abstract: Magnetic Ionic Liquids: Synthesis, Properties and Applications

AbstractReview: 120 refs.

Anomalous magnetism and normal field instability in supercooled liquid cobalt

Supercooled liquids may offer fascinating phenomena as compared with the normal state. In the case of supercooled paramagnetic liquids, completely different phenomena in high magnetic fields should be observed thanks to the high undercooling leading to higher magnetization and very strong magnetic coupling in the liquids. Here, we report the measurement of an undercooled pure liquid metal with a higher magnetization than the solid at the same temperature. We also observe the normal field instability pattern formation in the undercooled melt. Although the origin of the high magnetism of the liquid remains unclear, we discuss the possibility of a short range ordering effect.

Noncontact orientation of objects in three-dimensional space using magnetic levitation.

This paper describes several noncontact methods of orienting objects in 3D space using Magnetic Levitation (MagLev). The methods use two permanent magnets arranged coaxially with like poles facing and a container containing a paramagnetic liquid in which the objects are suspended. Absent external forcing, objects levitating in the device adopt predictable static orientations; the orientation depends on the shape and distribution of mass within the objects. The orientation of objects of uniform density in the MagLev device shows a sharp geometry-dependent transition: an analytical theory rationalizes this transition and predicts the orientation of objects in the MagLev device. Manipulation of the orientation of the levitating objects in space is achieved in two ways: (i) by rotating and/or translating the MagLev device while the objects are suspended in the paramagnetic solution between the magnets; (ii) by moving a small external magnet close to the levitating objects while keeping the device stationary. Unlike mechanical agitation or robotic selection, orienting using MagLev is possible for objects having a range of different physical characteristics (e.g., different shapes, sizes, and mechanical properties from hard polymers to gels and fluids). MagLev thus has the potential to be useful for sorting and positioning components in 3D space, orienting objects for assembly, constructing noncontact devices, and assembling objects composed of soft materials such as hydrogels, elastomers, and jammed granular media.

Synthesis and characterization of a novel paramagnetic functionalized ionic liquid as a highly efficient catalyst in one-pot synthesis of 1-amidoalkyl-2-naphtols

A novel paramagnetic ionic liquid, 3-(2-hydroxyethyl)-1-methyl imidazolium bromotrichloro ferrate (III), was synthesized and exhibited high catalytic performance in the synthesis of 1-amidoalkyl-2-naphthols via one-pot three-component condensation reaction of aromatic aldehydes, 2-naphthol and acetamide at 85°C under solvent-free conditions. The catalyst showed response to an external magnet and was characterized by Fourier transform infrared spectroscopy (FT-IR), UV–Visible spectroscopy, Thermal gravimetric analysis (TGA) and Raman spectroscopy.

Direction-dependent freezing of diamagnetic colloidal tracers suspended in paramagnetic ionic liquids.

The dynamic behavior of an inverse ferrofluid consisting of diamagnetic, spherical silica particles suspended in the paramagnetic ionic liquid (EMIm)2[Co(NCS)4] is investigated by means of x-ray photon correlation spectroscopy in the presence of an external magnetic field. Dipole-dipole interactions between the diamagnetic holes in the paramagnetic continuum of the suspending medium induce a direction-dependence of the diffusive motion of the colloidal particles: due to a magnetic repulsion perpendicular to the direction of an external field the diffusive motion of the colloidal particles is selectively frozen in this direction.

Fundamental Study on Magnetic Separator Using Oxygen Dissolved Perfluorocarbon

In this study, we have designed a magnetic separator for medical valuable substance. The substance shows diamagnetism and the density is slightly higher than water. A magneto Archimedes separation is effective in those substances. The separation is a technique to utilize the difference of the levitation place decided by the magnetic susceptibility and the density of substances under the magnetic field. However, the medium used for separation is a paramagnetic liquid in which the manganese chloride and the rare earth nitrate were dissolved, and there are such problems as the metal salt adhesion to the substance and the equipment. When food and a medicine are treated as a separation substance, the security is important in practical use. The oxygen dissolved perfluorocarbon under the pressure was used as the medium. Under atmospheric pressure, a metallic compound doesn't remain on the surface of the separation substance and equipment. Dissolved oxygen concentration rises by pressurization according to Henry's law. By controlling of the pressure and the external magnetic field, the separation of a plastic and KCl used as imitation sample succeeded. The magnetic force and the pressure needed for the separation were estimated from calculations and the separation experiments. We report these results.

Stoner Instability Revisited: Emergence of Local Quantum Criticality?

We revisit Stoner instability, an old problem but in a modern point of view. An idea is to extract out dynamics of directional fluctuations of spins explicitly, resorting to the CP$^{1}$ representation and integrating over their amplitude fluctuations. As a result, we derive an effective field theory for ferromagnetic quantum phase transitions in terms of bosonic spinons and fermionic holons. We show that this effective field theory reproduces overdamped spin dynamics in a paramagnetic Fermi liquid and magnon spectrum in a ferromagnetic Fermi liquid. An interesting observation is that the velocity of spinons becomes zero, approaching the ferromagnetic quantum critical point, which implies emergence of local quantum criticality. Based on this scenario, we predict the $\omega/T$ scaling behavior near ferromagnetic quantum criticality beyond the conventional scenario of the weak-coupling approach.

Physicochemical characterization of paramagnetic ionic liquids 1‐vinyl‐3‐alkylimidazolium tetrahalogenidoferrate(III) [VRIM][FeClmBr4 − m

Using microwave‐assisted synthesis method, a series of paramagnetic ionic liquids comprising 1‐vinyl‐3‐alkylimidazolium VRIM+ cation and tetrahalogenidoferrate (III) FeClmBr4 − m− anion were designed and synthesized. The structure was analyzed using 1H NMR and Raman spectroscopy. Ultraviolet–visible absorption spectra, thermal stability, magnetic susceptibility, viscosity, ionic conductivity, and solubility were characterized. Results show that elongation of the alkyl chain leads to replacement of bromides with a small amount of chlorides in the anion, shifting of UV maximum absorption peaks to shorter wavelengths, reduction of ionic conductivity, and solubility in polar solvents, as well as increase in fluidity, magnetic susceptibility, and solubility in nonpolar solvents. Copyright © 2014 John Wiley & Sons, Ltd.

Determination of Structural Characteristics of All-Organic Radical Liquid Crystals Based on Analysis of the Dipole–Dipole Broadened EPR Spectra

The angular dependences of g-value and line width of EPR spectra of paramagnetic all-organic liquid crystalline (LC) materials were measured for the quantitative characterization of the nematic, cholesteric, and smectic C phases. The detailed molecular alignment in mesophases was determined by means of numerical spectra simulation focusing on spin exchange and dipole-dipole magnetic interactions of neighboring molecules. The obtained structural data indicate that the spin polarization mechanism between neighboring molecules rather than the direct through-space interactions between paramagnetic centers is responsible for the specific magnetic properties of the studied LC materials.