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Magnetochemistry, Volume 7, Issue 1 (January 2021) – 16 articles

Cover Story (view full-size image): The hydrothermal reaction of lanthanide(III) nitrates and pyrimidine-4,6-dicarboxylic acid gives rise to five different families of isostructural coordination polymers (CPs). These compounds contain oxalate anions, generated as a byproduct, or nitrate anions when the synthesis is carried out in the absence of solvent, both of which participate as co-ligands. The analysis of the alternating current measurements shows field-induced SMM behavior in the Dy-based counterparts, among which higher energy barriers are achieved for those compounds containing the polyhedron that best approaches to an ideal shape. Moreover, these CPs present intense and quite long-lived photoluminescence in solid state at room temperature with characteristic emissions of the corresponding lanthanide, among which one of the Eu-based CPs shows an absolute quantum yield of 25.0%. View this paper.
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Open AccessFeature PaperArticle
Dynamics of a Pair of Paramagnetic Janus Particles under a Uniform Magnetic Field and Simple Shear Flow
Magnetochemistry 2021, 7(1), 16; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010016 - 19 Jan 2021
Viewed by 343
Abstract
We numerically investigate the dynamics of a pair of circular Janus microparticles immersed in a Newtonian fluid under a simple shear flow and a uniform magnetic field by direct numerical simulation. Using the COMSOL software, we applied the finite element method, based on [...] Read more.
We numerically investigate the dynamics of a pair of circular Janus microparticles immersed in a Newtonian fluid under a simple shear flow and a uniform magnetic field by direct numerical simulation. Using the COMSOL software, we applied the finite element method, based on an arbitrary Lagrangian-Eulerian approach, and analyzed the dynamics of two anisotropic particles (i.e., one-half is paramagnetic, and the other is non-magnetic) due to the center-to-center distance, magnetic field strength, initial particle orientation, and configuration. This article considers two configurations: the LR-configuration (magnetic material is on the left side of the first particle and on the right side of the second particle) and the RL-configuration (magnetic material is on the right side of the first particle and on the left side of the second particle). For both configurations, a critical orientation determines if the particles either attract (below the critical) or repel (above the critical) under a uniform magnetic field. How well the particles form a chain depends on the comparison between the viscous and magnetic forces. For long particle distances, the viscous force separates the particles, and the magnetic force causes them to repel as the particle orientation increases above the configuration’s critical value. As the initial distance decreases, a chain formation is possible at a steady orientation, but is more feasible for the RL-configuration than the LR-configuration under the same circumstances. Full article
(This article belongs to the Special Issue Structure, Thermodynamics and Applications of Ferrofluids)
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Open AccessFeature PaperReview
Quantitative NMR as a Versatile Tool for the Reference Material Preparation
Magnetochemistry 2021, 7(1), 15; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010015 - 18 Jan 2021
Viewed by 278
Abstract
The assessment of primary calibrator purity is critical for establishing traceability to the International System of Units (SI). Recently, quantitative nuclear magnetic resonance (qNMR) has been used as a purity determination method for reference material development, and many related measurement techniques have been [...] Read more.
The assessment of primary calibrator purity is critical for establishing traceability to the International System of Units (SI). Recently, quantitative nuclear magnetic resonance (qNMR) has been used as a purity determination method for reference material development, and many related measurement techniques have been designed to acquire accurate and reliable results. This review introduces the recent advances in these techniques (including multidimensional methods), focusing on the application of qNMR to reference material preparation. Full article
(This article belongs to the Special Issue Review Papers on Magnetic Resonances)
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Open AccessArticle
Microstructure Evolution of Ag/TiO2 Thin Film
Magnetochemistry 2021, 7(1), 14; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010014 - 16 Jan 2021
Viewed by 392
Abstract
Ag/TiO2 thin films were prepared using the sol-gel spin coating method. The microstructural growth behaviors of the prepared Ag/TiO2 thin films were elucidated using real-time synchrotron radiation imaging, its structure was determined using grazing incidence X-ray diffraction (GIXRD), its morphology was [...] Read more.
Ag/TiO2 thin films were prepared using the sol-gel spin coating method. The microstructural growth behaviors of the prepared Ag/TiO2 thin films were elucidated using real-time synchrotron radiation imaging, its structure was determined using grazing incidence X-ray diffraction (GIXRD), its morphology was imaged using the field emission scanning electron microscopy (FESEM), and its surface topography was examined using the atomic force microscope (AFM) in contact mode. The cubical shape was detected and identified as Ag, while the anatase, TiO2 thin film resembled a porous ring-like structure. It was found that each ring that coalesced and formed channels occurred at a low annealing temperature of 280 °C. The energy dispersive X-ray (EDX) result revealed a small amount of Ag presence in the Ag/TiO2 thin films. From the in-situ synchrotron radiation imaging, it was observed that as the annealing time increased, the growth of Ag/TiO2 also increased in terms of area and the number of junctions. The growth rate of Ag/TiO2 at 600 s was 47.26 µm2/s, and after 1200 s it decreased to 11.50 µm2/s and 11.55 µm2/s at 1800 s. Prolonged annealing will further decrease the growth rate to 5.94 µm2/s, 4.12 µm2/s and 4.86 µm2/s at 2400 s, 3000 s and 3600 s, respectively. Full article
(This article belongs to the Special Issue Advances in Amorphous and Nanocrystalline Magnetic Materials)
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Open AccessArticle
Tuning the Magnetocaloric Properties of the La(Fe,Si)13 Compounds by Chemical Substitution and Light Element Insertion
Magnetochemistry 2021, 7(1), 13; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010013 - 14 Jan 2021
Viewed by 255
Abstract
LaFe13xSix compounds exhibit a giant magnetocaloric effect and they are considered as a good magnetocaloric working substance for an environmentally friendly cooling technique. Nevertheless as the Curie temperature TC is around 200 K, it is necessary to [...] Read more.
LaFe13xSix compounds exhibit a giant magnetocaloric effect and they are considered as a good magnetocaloric working substance for an environmentally friendly cooling technique. Nevertheless as the Curie temperature TC is around 200 K, it is necessary to tune TC near room temperature for magnetic refrigeration. In this work we present a review of the various methods of synthesis and shaping of the LaFe13xSix type compounds as well as the influence of chemical substitution, light element insertion or combination of both on TC, magnetic entropy and adiabatic temperature variation (ΔSM and ΔTad), and stability upon cycling. The advantages and drawbacks of each method of preparation and type of element substitution/insertion are discussed. The implementation of these NaZn13 type materials in active magnetic refrigerator is presented and their performances are compared to that of Gd in prototypes. Full article
(This article belongs to the Special Issue Magnetocaloric and Caloric Materials for Solid-State Cooling)
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Open AccessArticle
New Mononuclear Mn(III) Complexes with Hydroxyl-Substituted Hexadentate Schiff Base Ligands
Magnetochemistry 2021, 7(1), 12; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010012 - 13 Jan 2021
Viewed by 295
Abstract
This paper reports the syntheses, crystal structures and magnetic properties of Mn(III) hexadentate Schiff base complexes [Mn(4-OH-sal-N-1,5,8,12)]NO3(1) and [Mn(4-OH-sal-N-1,5,8,12)]ClO4(2), where (4-OH-sal-N-1,5,8,12)2− (4,4′-((1E,13E)-2,6,9,13-tetraazatetradeca-1,13-diene-1,14-diyl)bis(3-methoxyphenol) is a new hydroxyl-substituted hexadentate Schiff base ligand. The introduction of the (4-OH-sal-N-1,5,8,12)2− ligand [...] Read more.
This paper reports the syntheses, crystal structures and magnetic properties of Mn(III) hexadentate Schiff base complexes [Mn(4-OH-sal-N-1,5,8,12)]NO3(1) and [Mn(4-OH-sal-N-1,5,8,12)]ClO4(2), where (4-OH-sal-N-1,5,8,12)2− (4,4′-((1E,13E)-2,6,9,13-tetraazatetradeca-1,13-diene-1,14-diyl)bis(3-methoxyphenol) is a new hydroxyl-substituted hexadentate Schiff base ligand. The introduction of the (4-OH-sal-N-1,5,8,12)2− ligand induces more hydrogen bonding interactions, in addition to promoting the formation of intermolecular interactions among the cations. However, the close-packing structures of both complexes lead to their stabilization in the high-spin state in the temperature range of 2−300 K. Full article
(This article belongs to the Special Issue Molecular Magnetism 2021: Paradigmatic Landmarks and Horizons)
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Open AccessArticle
Enrichment of Rabbit Primitive Hematopoietic Cells via MACS Depletion of CD45+ Bone Marrow Cells
Magnetochemistry 2021, 7(1), 11; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010011 - 13 Jan 2021
Viewed by 242
Abstract
Hematopoietic stem and progenitor cells (HSC/HPCs) of human or few animal species have been studied for over 30 years. However, there is no information about rabbit HSC/HPCs, although they might be a valuable animal model for studying human hematopoietic disorders or could serve [...] Read more.
Hematopoietic stem and progenitor cells (HSC/HPCs) of human or few animal species have been studied for over 30 years. However, there is no information about rabbit HSC/HPCs, although they might be a valuable animal model for studying human hematopoietic disorders or could serve as genetic resource for the preservation of animal biodiversity. CD34 marker is commonly used to isolate HSC/HPCs. Due to unavailability of specific anti-rabbit CD34 antibodies, a novel strategy for the isolation and enrichment of rabbit HSC/HPCs was used in this study. Briefly, rabbit bone marrow mononuclear cells (BMMCs) were sorted immunomagnetically in order to remove all mature (CD45+) cells. The cells were depleted with overall purity about 60–70% and then cultured in a special medium designed for the expansion of CD34+ cells. Quantitative Polymerase Chain Reaction (qPCR) analysis confirmed the enrichment of primitive hematopoietic cells, as the expression of CD34 and CD49f increased (p < 0.05) and CD45 decreased (p < 0.001) at the end of culture in comparison to fresh BMMCs. However, cell culture still exhibited the presence of CD45+ cells, as identified by flow cytometry. After gating on CD45 cells the MHCI+MHCIICD38+CD49f+CD90CD117 phenotype was observed. In conclusion, rabbit HSC/HPCs might be isolated and enriched by the presented method. However, further optimization is still required. Full article
(This article belongs to the Special Issue Magnetic Cell Separation)
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Open AccessArticle
A Novel Computational Method to Identify/Analyze Hysteresis Loops of Hard Magnetic Materials
Magnetochemistry 2021, 7(1), 10; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010010 - 07 Jan 2021
Viewed by 329
Abstract
In this study, a novel computational method capable of reproducing hysteresis loops of hard magnetic materials is proposed. It is conceptually based on the classical Preisach model but has a completely different approach in the modeling of the hysteron effect. Indeed, the change [...] Read more.
In this study, a novel computational method capable of reproducing hysteresis loops of hard magnetic materials is proposed. It is conceptually based on the classical Preisach model but has a completely different approach in the modeling of the hysteron effect. Indeed, the change in magnetization caused by a single hysteron is compared here to the change in velocity of two disk-shaped solids elastically colliding with each other rather than the effect of ideal geometrical entities giving rise to so-called Barkhausen jumps. This allowed us to obtain a simple differential formulation for the global magnetization equation with a significant improvement in terms of computational performance. A sensitivity analysis on the parameters of the proposed method has indeed shown the capability to model a large class of hysteresis loops. Moreover, the proposed method permits modeling of the temperature effect on magnetization of neodymium magnets, which is a key point for the design of electrical machines. Therefore, application of the proposed method to the hysteresis loop of a real NdFeB magnet has been proven to be very accurate and efficient for a large temperature range. Full article
(This article belongs to the Special Issue Advances in Computational Electromagnetics)
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Open AccessArticle
Evaluation of the Effect of Silica Fume on Amorphous Fly Ash Geopolymers Exposed to Elevated Temperature
Magnetochemistry 2021, 7(1), 9; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010009 - 06 Jan 2021
Cited by 1 | Viewed by 475
Abstract
The properties of amorphous geopolymer with silica fume addition after heat treatment was rarely reported in the geopolymer field. Geopolymer was prepared by mixing fly ash and alkali activator. The silica fume was added in 2% and 4% by weight. The geopolymer samples [...] Read more.
The properties of amorphous geopolymer with silica fume addition after heat treatment was rarely reported in the geopolymer field. Geopolymer was prepared by mixing fly ash and alkali activator. The silica fume was added in 2% and 4% by weight. The geopolymer samples were cured at room temperature for 28 days before exposed to an elevated temperature up to 1000 °C. The incorporation of 2% silica fume did not cause significant improvement in the compressive strength of unexposed geopolymer. Higher silica fume content of 4% reduced the compressive strength of the unexposed geopolymer. When subjected to elevated temperature, geopolymer with 2% silica fume retained higher compressive strength at 1000 °C. The addition of silica fume in fly ash geopolymer caused a lower degree of shrinkage and expansion, as compared to geopolymer without the addition of silica fume. Crystalline phases of albite and magnetite were formed in the geopolymer at 1000 °C. Full article
(This article belongs to the Special Issue Advances in Amorphous and Nanocrystalline Magnetic Materials)
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Open AccessFeature PaperArticle
Single-Ion Magnet and Photoluminescence Properties of Lanthanide(III) Coordination Polymers Based on Pyrimidine-4,6-Dicarboxylate
Magnetochemistry 2021, 7(1), 8; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010008 - 04 Jan 2021
Viewed by 419
Abstract
Herein, we report the magnetic and photoluminescence characterization of coordination polymers (CP) built from the combination of lanthanide(III) ions, pyrimidine-4,6-dicarboxylate (pmdc) ligand and a co-ligand with formula {[Dy(μ-pmdc)(μ-ox)0.5(H2O)3]·2H2O}n (1-Dy), {[Dy(μ3-pmdc)(μ-ox) [...] Read more.
Herein, we report the magnetic and photoluminescence characterization of coordination polymers (CP) built from the combination of lanthanide(III) ions, pyrimidine-4,6-dicarboxylate (pmdc) ligand and a co-ligand with formula {[Dy(μ-pmdc)(μ-ox)0.5(H2O)3]·2H2O}n (1-Dy), {[Dy(μ3-pmdc)(μ-ox)0.5(H2O)2] ~2.33H2O}n (2-Dy), {[Dy23-pmdc)(μ4-pmdc)(μ-ox)(H2O)3]·5H2O}n (3-Dy), {[Ln(μ3-pmdc)(μ-ox)0.5(H2O)2]·H2O}n (where Ln(III) = Nd (4-Nd), Sm (4-Sm), Eu (4-Eu) and Dy (4-Dy)) and {[Dy(μ4-pmdc)(NO3)(H2O)]·H2O}n (5-Dy). It must be noted the presence of oxalate anion acting as ditopic co-ligand in compounds 1-Dy, 2-Dy, 3-Dy and 4-Ln, whereas in 5-Dy the nitrate anion plays the role of terminal co-ligand. Direct current measurements carried out for the dysprosium-based CPs reveal almost negligible interactions between Dy3+ ions within the crystal structure, which is confirmed by computed values of the exchange parameters J. In addition, alternating current measurements show field-induced single-molecule magnet (SMM) behavior in compounds 1-Dy, 2-Dy, 4-Dy and 5-Dy, whereas slight-frequency dependence is also observed in 3-Dy. Solid state emission spectra performed at room temperature for those compounds emitting in visible region confirm the occurrence of significant ligand-to-lanthanide charge transfer in view of the strong characteristic emissions for all lanthanide ions. Emission decay curves were also recorded to estimate the emission lifetimes for the reported compounds, in addition to the absolute quantum yields. Among them, the high quantum yield of 25.0% measured for 4-Eu is to be highlighted as a representative example of the good emissive properties of the materials. Full article
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Open AccessFeature PaperArticle
The Microstructural Model of the Ferromagnetic Material Behavior in an External Magnetic Field
Magnetochemistry 2021, 7(1), 7; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010007 - 01 Jan 2021
Cited by 1 | Viewed by 353
Abstract
In this paper, the behavior of a ferromagnetic material is considered in the framework of microstructural modeling. The equations describing the behavior of such material in the magnetic field, are constructed based on minimization of total magnetic energy with account of limitations imposed [...] Read more.
In this paper, the behavior of a ferromagnetic material is considered in the framework of microstructural modeling. The equations describing the behavior of such material in the magnetic field, are constructed based on minimization of total magnetic energy with account of limitations imposed on the spontaneous magnetization vector and scalar magnetic potential. This conditional extremum problem is reduced to the unconditional extremum problem using the Lagrange multiplier. A variational (weak) formulation is written down and linearization of the obtained equations is carried out. Based on the derived relations a solution of a two-dimensional problem of magnetization of a unit cell (a grain of a polycrystal or a single crystal of a ferromagnetic material) is developed using the finite element method. The appearance of domain walls is demonstrated, their thickness is determined, and the history of their movement and collision is described. The graphs of distributions of the magnetization vector in domains and in domain walls in the external magnetic field directed at different angles to the anisotropy axis are constructed and the magnetization curves for a macrospecimen are plotted. The results obtained in the present paper (the thickness of the domain wall, the formation of a 360-degree wall) are in agreement with the ones available in the current literature. Full article
(This article belongs to the Special Issue Advances in Computational Electromagnetics)
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Open AccessFeature PaperArticle
Fabrication of Dy2O3 Transparent Ceramics by Vacuum Sintering Using Precipitated Powders
Magnetochemistry 2021, 7(1), 6; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010006 - 28 Dec 2020
Viewed by 424
Abstract
As a kind of promising material for a Faraday isolator used in the visible and near infrared range, Dy2O3 transparent ceramics were prepared by vacuum sintering from the nano-powders synthesized by the liquid precipitation method using ammonium hydrogen carbonate as [...] Read more.
As a kind of promising material for a Faraday isolator used in the visible and near infrared range, Dy2O3 transparent ceramics were prepared by vacuum sintering from the nano-powders synthesized by the liquid precipitation method using ammonium hydrogen carbonate as precipitant with no sintering aids. The synthesized precursor was calcinated at 950 °C–1150 °C for 4 h in air. The influences of the calcination temperature on the morphologies and phase composition of Dy2O3 powders were characterized. It is found that the Dy2O3 powder calcinated at 1000 °C for 4 h is superior for the fabrication of Dy2O3 ceramics. The Dy2O3 transparent ceramic sample prepared by vacuum sintering at 1850 °C for 10 h, and subsequently with air annealing at 1400 °C for 10 h, from the 1000 °C-calcined Dy2O3 powders, presents the best optical quality. The values of in-line transmittance of the optimal ceramic specimen with the thickness of 1.0 mm are 75.3% at 2000 nm and 67.9% at 633 nm. The Verdet constant of Dy2O3 ceramics was measured to be −325.3 ± 1.9 rad/(T·m) at 633 nm, about 2.4 times larger than that of TGG (Tb3Ga5O12) single crystals. Full article
(This article belongs to the Special Issue Magneto-Optical Ceramics)
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Open AccessReview
Magnetic Resonance and CT Imaging Biomarkers for Prediction of Acute and Chronic Radiation-Induced Xerostomia
Magnetochemistry 2021, 7(1), 5; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010005 - 24 Dec 2020
Viewed by 462
Abstract
Xerostomia is a common adverse effect of radiation therapy at the head and neck area. Radiation-induced xerostomia can be severe and detrimental for the quality of life. Clinicians and radiologists have focused on the prevention of xerostomia as feasible, which has been significantly [...] Read more.
Xerostomia is a common adverse effect of radiation therapy at the head and neck area. Radiation-induced xerostomia can be severe and detrimental for the quality of life. Clinicians and radiologists have focused on the prevention of xerostomia as feasible, which has been significantly improved in the recent decades with the use of the contemporary radiation technology. However, radiation-induced xerostomia still remains one of the most devastating side effects of radiation therapy. Clinical risk factors have been identified, but the variation of its incidence and presentation has turned the focus on the investigation of parameters that would be able to predict the onset of acute or chronic xerostomia for each individual patient. Recently, potential imaging parameters and biomarkers are investigated in order for early prediction of the incidence and severity of xerostomia. Here, we compile the resulting imaging biomarkers as have been identified in the recent literature based on MRI and CT performed in correlation with radiation therapy. The identification of such biomarkers is very promising for the prevention and control of xerostomia in the head and neck radiation setting. Full article
(This article belongs to the Special Issue Review Papers on Magnetic Resonances)
Open AccessArticle
Comparison between XY Spin Chains with Spin 1/2 or 1 Interacting with Quantized Electromagnetic Field by One and Two Photon Jaynes-Cummings Model
Magnetochemistry 2021, 7(1), 4; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010004 - 23 Dec 2020
Viewed by 348
Abstract
This paper describes two cases of interaction between a quantized electromagnetic field and two different XY spin molecules; one with spins ½, and the other with spins 1. Both interact with a quantized electromagnetic field, with one of the spins in the chain [...] Read more.
This paper describes two cases of interaction between a quantized electromagnetic field and two different XY spin molecules; one with spins ½, and the other with spins 1. Both interact with a quantized electromagnetic field, with one of the spins in the chain interacting with the electromagnetic field. The interaction between the field mode and the spin chain with spins 1 is described by the one- and two-photon Jaynes-Cummings model (JC model). On the other hand, the interaction between the spins ½ and the electromagnetic field is described only by the one-photon Jaynes-Cummings model. Analytical and numerical calculations were made for the case of a different number of photons in the field mode, a different number of spins, and a different position of spin, interacting with the electromagnetic field. The invariant and block structures of such a chain are shown with a comparison made between the evolution of the magnetic moment and the number of photons in both cases. Full article
(This article belongs to the Special Issue Recent Advances in Solid State Physics Devices)
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Open AccessFeature PaperArticle
Synthesis, NMR Characterization, and Antileukemic Activity of N-Nonanoylpiperazinyl-5α-Androstane-3α,17β-Diol A-Ring Derivatives
Magnetochemistry 2021, 7(1), 3; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010003 - 23 Dec 2020
Viewed by 411
Abstract
The combination of an androstane-3,17-diol nucleus and a 2β-N-alkylamidopiperazino sidechain is important for the anticancer activity of a new family of steroid derivatives. As the structure-activity relationship studies have so far been limited to the beta orientation of the substituent at [...] Read more.
The combination of an androstane-3,17-diol nucleus and a 2β-N-alkylamidopiperazino sidechain is important for the anticancer activity of a new family of steroid derivatives. As the structure-activity relationship studies have so far been limited to the beta orientation of the substituent at position 2 of the steroid nucleus, a series of analogs (compounds 14) were synthesized to investigate the impact on biological activity of A-ring substitution. Nuclear magnetic resonance (NMR) analysis, especially using a series of 2D experiments, such as correlation spectroscopy (COSY), homonuclear Overhauser effect spectroscopy (NOESY), heteronuclear single-quantum correlation (HSQC), and heteronuclear multiple-bond correlation (HMBC) provided crucial information that was found essential in confirming the sidechain position and orientation of compounds 14. Assessment of their antiproliferative activity on leukemia HL-60 cells confirmed the best efficiency of the 2β-sidechain/3α-OH orientation (compound 1) compared to the other configurations tested (compounds 24). Full article
(This article belongs to the Section Magnetic Resonances)
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Open AccessArticle
Oscillations of EPR Signals Accompanying Belousov–Zhabotinsky Reaction
Magnetochemistry 2021, 7(1), 2; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010002 - 23 Dec 2020
Viewed by 298
Abstract
Periodical transformation of ferroin to ferriin is accompanied by changes in magnetic properties of liquids during Belousov–Zhabotinsky (BZ) reaction malonic acid, sodium bromide, sodium bromate, ferroin, and sulfuric acid. Instead of the earlier studied oscillation of microwave conductivity accompanying an oscillating reaction, we [...] Read more.
Periodical transformation of ferroin to ferriin is accompanied by changes in magnetic properties of liquids during Belousov–Zhabotinsky (BZ) reaction malonic acid, sodium bromide, sodium bromate, ferroin, and sulfuric acid. Instead of the earlier studied oscillation of microwave conductivity accompanying an oscillating reaction, we propose a flash technique to interrupt the BZ reaction by rapid freezing. Rapid cooling of a solution during chemical oscillations results in a frozen system with a fixed concentration of paramagnetic centers Fe3+. EPR spectrum recorded at different stages of the interrupted reaction corresponds to the exact concentration of the ferroin and ferriin components. Following unfreezing unblocks the BZ reaction, and oscillations are still observed. A simulated spectrum allows one to distinguish two groups of Fe3+ ions of different symmetries. The obtained results are important to explain the earlier observed effect of inhomogeneous magnetic field on BZ reaction front velocity. Full article
(This article belongs to the Special Issue Stimuli-Responsive Magnetic Molecular Materials)
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Open AccessReview
High-Coordinate Mononuclear Ln(III) Complexes: Synthetic Strategies and Magnetic Properties
Magnetochemistry 2021, 7(1), 1; https://0-doi-org.brum.beds.ac.uk/10.3390/magnetochemistry7010001 - 22 Dec 2020
Viewed by 418
Abstract
Single-molecule magnets involving monometallic 4f complexes have been investigated extensively in last two decades to understand the factors that govern the slow magnetization relaxation behavior in these complexes and to establish a magneto-structural correlation. The prime goal in this direction is to suppress [...] Read more.
Single-molecule magnets involving monometallic 4f complexes have been investigated extensively in last two decades to understand the factors that govern the slow magnetization relaxation behavior in these complexes and to establish a magneto-structural correlation. The prime goal in this direction is to suppress the temperature independent quantum tunneling of magnetization (QTM) effect via fine-tuning the coordination geometry/microenvironment. Among the various coordination geometries that have been pursued, complexes containing high coordination number around Ln(III) are sparse. Herein, we present a summary of the various synthetic strategies that were used for the assembly of 10- and 12-coordinated Ln(III) complexes. The magnetic properties of such complexes are also described. Full article
(This article belongs to the Special Issue From Magnetic Anisotropy to Molecular Magnets: Theory and Experiments)
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