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Magnetochemistry, Volume 4, Issue 3 (September 2018) – 13 articles

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Cover Story (view full-size image) This communication describes the first example of colloidal nanoparticles comprising [...] Read more.
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Open AccessArticle
How to Make a Better Magnet? Insertion of Additional Bridging Ligands into a Magnetic Coordination Polymer
Magnetochemistry 2018, 4(3), 41; https://doi.org/10.3390/magnetochemistry4030041 - 15 Sep 2018
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Abstract
A three-dimensional cyanide-bridged coordination polymer based on FeII (S = 2) and NbIV (S = 1/2) {[FeII(H2O)2]2[NbIV(CN)8]·4H2O}n (Fe2Nb) was modified [...] Read more.
A three-dimensional cyanide-bridged coordination polymer based on FeII (S = 2) and NbIV (S = 1/2) {[FeII(H2O)2]2[NbIV(CN)8]·4H2O}n (Fe2Nb) was modified at the self-assembly stage by inserting an additional formate HCOO bridge into its cyanide framework. The resulting mixed-bridged {(NH4)[(H2O)FeII-(μ-HCOO)-FeII(H2O)][NbIV(CN)8]·3H2O}n (Fe2NbHCOO) exhibited additional FeII-HCOO-FeII structural motifs connecting each of the two FeII centers. The insertion of HCOO was possible due to the substitution of some of the aqua ligands and crystallization water molecules in the parent framework by formate anions and ammonium cations. The formate molecular bridge not only shortened the distance between FeII ions in Fe2NbHCOO from 6.609 Å to 6.141 Å, but also created additional magnetic interaction pathways between the magnetic centers, resulting in an increase in the long range magnetic ordering temperature from 43 K for Fe2Nb to 58 K. The mixed-bridged Fe2NbHCOO also showed a much broader magnetic hysteresis loop of 0.102 T, compared to 0.013 T for Fe2Nb. Full article
(This article belongs to the Special Issue Multifunctional Molecule-based Magnetic Materials)
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Open AccessArticle
Effects of Vertical Magnetohydrodynamic Flows on Chiral Surface Formation in Magnetoelectrolysis
Magnetochemistry 2018, 4(3), 40; https://doi.org/10.3390/magnetochemistry4030040 - 06 Sep 2018
Cited by 2 | Viewed by 1200
Abstract
Magnetoelectrolysis (electrolysis in magnetic fields) has potential to produce chiral surfaces on metal films. The Lorentz force causes two types of magnetohydrodynamic (MHD) flows; a vertical MHD flow and micro-MHD vortices, and the combination of these MHD flows has been considered to produce [...] Read more.
Magnetoelectrolysis (electrolysis in magnetic fields) has potential to produce chiral surfaces on metal films. The Lorentz force causes two types of magnetohydrodynamic (MHD) flows; a vertical MHD flow and micro-MHD vortices, and the combination of these MHD flows has been considered to produce chiral surfaces. This paper shows the effects of vertical MHD flow on the chiral surface formation in magnetoelectrodeposition (MED) and magnetoelectrochemical etching (MEE) of copper films. To control the vertical MHD flows the working electrode was embedded in a tube wall with various heights of 2–12 mm, and the vertical MHD flows were expected to penetrate into the tubes with damping. In both MED and MEE experiments, the surface chirality diminished considerably at the wall height of 12 mm. When the penetrating MHD flow could not reach the electrode surface in the sufficiently tall wall, such an MHD flow could not affect the micro-MHD vortices. These results demonstrate that the vertical MHD flow plays a significant role in symmetry breaking of micro-MHD vortices. Full article
(This article belongs to the Special Issue Magnetic Fields in Microfluidic Systems)
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Open AccessFeature PaperArticle
Slow Relaxation of the Magnetization in Bis-Decorated Chiral Helicene-Based Coordination Complexes of Lanthanides
Magnetochemistry 2018, 4(3), 39; https://doi.org/10.3390/magnetochemistry4030039 - 05 Sep 2018
Cited by 5 | Viewed by 1319
Abstract
The complexes [Ln2(hfac)6(L)]·nC6H14 (Ln = Dy (1) n = 0, Yb (2) n = 1) with the L chiral 3,14-di-(2-pyridyl)-4,13-diaza[6]helicene ligand (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) have been synthesized in their [...] Read more.
The complexes [Ln2(hfac)6(L)]·nC6H14 (Ln = Dy (1) n = 0, Yb (2) n = 1) with the L chiral 3,14-di-(2-pyridyl)-4,13-diaza[6]helicene ligand (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonate) have been synthesized in their racemic form and structurally and magnetically characterized. Both complexes behave as field-induced single molecule magnets in the crystalline phase. These magnetic properties were rationalized by ab initio calculations. Full article
(This article belongs to the Special Issue Multifunctional Molecule-based Magnetic Materials)
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Open AccessArticle
Heterobimetallic One-Dimensional Coordination Polymers MICuII (M = Li and K) Based on Ferromagnetically Coupled Di- and Tetracopper(II) Metallacyclophanes
Magnetochemistry 2018, 4(3), 38; https://doi.org/10.3390/magnetochemistry4030038 - 25 Aug 2018
Cited by 1 | Viewed by 1219
Abstract
The synthesis, crystal structure and magnetic properties of the coordination polymers of formula [EDAP{Li6(H2O)8[(Cu2(μ-mpba)2)2(H2O)2]}]n (1) and [(EDAP)2{K(H2O)4[Cu2 [...] Read more.
The synthesis, crystal structure and magnetic properties of the coordination polymers of formula [EDAP{Li6(H2O)8[(Cu2(μ-mpba)2)2(H2O)2]}]n (1) and [(EDAP)2{K(H2O)4[Cu2(μ-mpba)2(H2O)2]}Cl·2H2O]n (2), in which mpba = N,N′-1,3-phenylenebis(oxamate) and EDAP2+ = 1,1′-ethylenebis(4-aminopyridinium) are described. Both compounds have in common the presence of the [Cu2(mpba)2]4− tetraanionic unit which is a [3,3] metallacyclophane motif in which the copper(II) ions are five-coordinate in a distorted square pyramidal surrounding. The complex anion in 1 is dimerized through double out-of-plane copper to outer carboxylate-oxygen atoms resulting in the centrosymmetric tetracopper(II) fragment [Cu4(μ-mpba)4(H2O)2]8− which act as a ligand toward six hydrated lithium(I) cations leading to anionic ladder-like double chains whose charge is neutralized by the EDAP2+ cations. In the case of 2, each dicopper(II) entity acts as a ligand towards tetraquapotassium(I) units to afford anionic zig zag single chains of formula {K(H2O)4[Cu2(μ-mpba)2(H2O)2]}n3n− plus EDAP2+ cations and non-coordinate chloride anions. Cryomagnetic measurements on polycrystalline samples 1 and 2 show the occurrence of ferromagnetic interactions between the copper(II) ions across the –Namidate–(C–C–C)phenyl–Namidate– exchange pathway [J = +10.6 (1) and +8.22 cm−1 (2)] and antiferromagnetic ones through the double out-of-plane carboxylate-oxygen atoms [j = −0.68 cm−1 (1), the spin Hamiltonian being defined as H = J ( S C u 1 · S C u 2 + S C u 2 i · S C u 1 i ) j ( S C u 2 · S C u 2 i ) ]. Full article
(This article belongs to the Special Issue Multifunctional Molecule-based Magnetic Materials)
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Open AccessCommunication
Magnetite–Corrole Hybrid Nanoparticles
Magnetochemistry 2018, 4(3), 37; https://doi.org/10.3390/magnetochemistry4030037 - 22 Aug 2018
Viewed by 1900
Abstract
This study describes the first example of a hybrid material comprising corrole- and silica-coated magnetite nanoparticles. Firstly, cuboid and spheroid magnetite nanoparticles were prepared using a simple hydrothermal route, followed by a silica coating. The hybrid nanoparticles were obtained by promoting a covalent [...] Read more.
This study describes the first example of a hybrid material comprising corrole- and silica-coated magnetite nanoparticles. Firstly, cuboid and spheroid magnetite nanoparticles were prepared using a simple hydrothermal route, followed by a silica coating. The hybrid nanoparticles were obtained by promoting a covalent link between a gallium (III)(pyridine) complex of 5,10,15-tris(pentafluorophenyl)corrole (GaPFC) and the surface of magnetite–silica core/shell nanoparticles (Fe3O4@SiO2), shaped both as cuboids and spheroids. The hybrids were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), ultraviolet-visible spectrophotometry (UV-Vis) and transmission electron microscopy (TEM). Preliminary studies on the capacity of singlet oxygen generation of the hybrid nanoparticles showed that these have lower efficiency values when compared to the pure corrole compound. Full article
(This article belongs to the Special Issue Magnetite Nanomaterials)
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Open AccessReview
Chiral Magneto-Electrochemistry
Magnetochemistry 2018, 4(3), 36; https://doi.org/10.3390/magnetochemistry4030036 - 18 Aug 2018
Cited by 5 | Viewed by 1525
Abstract
Magneto-electrochemistry (MEC) is a unique paradigm in science, where electrochemical experiments are carried out as a function of an applied magnetic field, creating a new horizon of potential scientific interest and technological applications. Over time, detailed understanding of this research domain was developed [...] Read more.
Magneto-electrochemistry (MEC) is a unique paradigm in science, where electrochemical experiments are carried out as a function of an applied magnetic field, creating a new horizon of potential scientific interest and technological applications. Over time, detailed understanding of this research domain was developed to identify and rationalize the possible effects exerted by a magnetic field on the various microscopic processes occurring in an electrochemical system. Notably, until a few years ago, the role of spin was not taken into account in the field of magneto-electrochemistry. Remarkably, recent experimental studies reveal that electron transmission through chiral molecules is spin selective and this effect has been referred to as the chiral-induced spin selectivity (CISS) effect. Spin-dependent electrochemistry originates from the implementation of the CISS effect in electrochemistry, where the magnetic field is used to obtain spin-polarized currents (using ferromagnetic electrodes) or, conversely, a magnetic field is obtained as the result of spin accumulation. Full article
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Open AccessArticle
Magneto-Optic Surface Plasmon Resonance Ti/Au/Co/Au/Pc Configuration and Sensitivity
Magnetochemistry 2018, 4(3), 35; https://doi.org/10.3390/magnetochemistry4030035 - 17 Aug 2018
Cited by 6 | Viewed by 1616
Abstract
Magneto-optic surface plasmon resonance (MOSPR)-based sensors are highly attractive as next-generation biosensors. However, these sensors suffer from oxidation leading to degradation of performance, reproducibility of the sensor surface, because of the difficulty of removing adsorbed materials, and degradation of the sensor surface during [...] Read more.
Magneto-optic surface plasmon resonance (MOSPR)-based sensors are highly attractive as next-generation biosensors. However, these sensors suffer from oxidation leading to degradation of performance, reproducibility of the sensor surface, because of the difficulty of removing adsorbed materials, and degradation of the sensor surface during surface cleaning and these limit their applications. In this paper, I propose MOSPR-based biosensors with 0 to 15 nm thick inert polycarbonate laminate plastic as a protective layer and theoretically demonstrate the practicability of my approach in water-medium for three different probing samples: ethanol, propanol, and pentanol. I also investigate microstructure and magnetic properties. The chemical composition and layered information of the sensor are investigated using X-ray reflectivity and X-ray diffraction analyses and these show distinct face-centered-cubic (fcc)-Au (111) phases, as dominated by the higher density of conduction electrons in Au as compared to Co. The magnetic characterization measured with the in-plane magnetic field to the sensor surface for both the as-deposited and annealed multilayers showed isotropic easy axis magnetization parallel to the multilayer interface at a saturating magnetic field of <100 Oersted (Oe). The sensor showed a maximum sensitivity of 5.5 × 104%/RIU (refractive index unit) for water–ethanol media and the highest detection level of 2.5 × 10−6 for water-pentanol media as the protective layer is increased from 0 to 15 nm. Full article
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Open AccessArticle
Abrupt Spin Crossover Behavior in a Linear N1,N2-Triazole Bridged Trinuclear Fe(II) Complex
Magnetochemistry 2018, 4(3), 34; https://doi.org/10.3390/magnetochemistry4030034 - 07 Aug 2018
Viewed by 1358
Abstract
The synthesis, structures and magnetic properties of a new trinuclear spin crossover complex [FeII3(pyrtrz)6(TsO)6]·10H2O·2CH3OH (C2) and its analogue binuclear [FeII2(pyrtrz)5(SCN)4 [...] Read more.
The synthesis, structures and magnetic properties of a new trinuclear spin crossover complex [FeII3(pyrtrz)6(TsO)6]·10H2O·2CH3OH (C2) and its analogue binuclear [FeII2(pyrtrz)5(SCN)4]·7H2O (C1), are reported here. These two compounds are synthesized based on the pyrrolyl functionalized Schiff base 1,2,4-triazole ligand 4-((1H-pyrrol-2-yl)methylene-amino)-4H-1,2,4-triazole (pyrtrz), which represent rare discrete multi-nuclear species, with µ2-N1,N2-triazole bridges linking the FeII centers. DC magnetic susceptibility measurements revealed an abrupt single-step spin crossover (SCO) behavior for compound 2 on the central FeII site and single-crystal X-ray diffraction (173 K) showed that this compound crystallizes in the monoclinic space group (P21/c), and multiple intramolecular interactions were found responsible for the abrupt transition. Compound 1 is a binuclear complex with thiocyanate as terminal ligands. This compound stays in high spin state over the whole temperature range and displays weak antiferromagnetic exchange coupling. Full article
(This article belongs to the Special Issue Spin-Crossover Beyond the Immediate Tribute)
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Open AccessArticle
Analysis of Artifacts Caused by Pulse Imperfections in CPMG Pulse Trains in NMR Relaxation Dispersion Experiments
Magnetochemistry 2018, 4(3), 33; https://doi.org/10.3390/magnetochemistry4030033 - 30 Jul 2018
Cited by 1 | Viewed by 1890
Abstract
Nuclear magnetic resonance relaxation dispersion (rd) experiments provide kinetics and thermodynamics information of molecules undergoing conformational exchange. Rd experiments often use a Carr-Purcell-Meiboom-Gill (CPMG) pulse train equally separated by a spin-state selective inversion element (U-element). Even with measurement parameters carefully set, however, parts [...] Read more.
Nuclear magnetic resonance relaxation dispersion (rd) experiments provide kinetics and thermodynamics information of molecules undergoing conformational exchange. Rd experiments often use a Carr-Purcell-Meiboom-Gill (CPMG) pulse train equally separated by a spin-state selective inversion element (U-element). Even with measurement parameters carefully set, however, parts of 1H–15N correlations sometimes exhibit large artifacts that may hamper the subsequent analyses. We analyzed such artifacts with a combination of NMR measurements and simulation. We found that particularly the lowest CPMG frequency (νcpmg) can also introduce large artifacts into amide 1H–15N and aromatic 1H–13C correlations whose 15N/13C resonances are very close to the carrier frequencies. The simulation showed that the off-resonance effects and miscalibration of the CPMG π pulses generate artifact maxima at resonance offsets of even and odd multiples of νcpmg, respectively. We demonstrate that a method once introduced into the rd experiments for molecules having residual dipolar coupling significantly reduces artifacts. In the method the 15N/13C π pulse phase in the U-element is chosen between x and y. We show that the correctly adjusted sequence is tolerant to miscalibration of the CPMG π pulse power as large as ±10% for most amide 15N and aromatic 13C resonances of proteins. Full article
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Open AccessArticle
Structure Confirmation and Evaluation of a Nonsteroidal Inhibitor of 17β-Hydroxysteroid Dehydrogenase Type 10
Magnetochemistry 2018, 4(3), 32; https://doi.org/10.3390/magnetochemistry4030032 - 23 Jul 2018
Cited by 3 | Viewed by 1124
Abstract
17β-Hydroxysteroid dehydrogenase type 10 (17β-HSD10) is a steroidogenesis enzyme known for its potential role in Alzheimer’s disease. For comparison purposes between steroidal and nonsteroidal 17β-HSD10 inhibitors 1 and 2, respectively, we attempted the chemical synthesis of benzothiazole phosphonate derivative 2. Instead [...] Read more.
17β-Hydroxysteroid dehydrogenase type 10 (17β-HSD10) is a steroidogenesis enzyme known for its potential role in Alzheimer’s disease. For comparison purposes between steroidal and nonsteroidal 17β-HSD10 inhibitors 1 and 2, respectively, we attempted the chemical synthesis of benzothiazole phosphonate derivative 2. Instead of a one-pot synthesis, we report a two-step synthesis with characterization of both imine intermediate 5 and final compound 2. Furthermore, complete assignation of 1H and 13C nuclear magnetic resonance (NMR) signals of 2 is provided, as we observed a divergence of NMR data with those published previously. Finally, biological assays showed that 1 and 2 inhibited the oxidation of estradiol (E2) into estrone (E1) by the 17β-HSD10 recombinant protein. However, in human embryonic kidney (HEK)-293 intact cells transfected with 17β-HSD10, only the steroidal inhibitor 1 induced a dose-dependent inhibition of E2 to E1 transformation. Full article
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Open AccessArticle
Supervised Learning to Predict Sperm Sorting by Magnetophoresis
Magnetochemistry 2018, 4(3), 31; https://doi.org/10.3390/magnetochemistry4030031 - 02 Jul 2018
Viewed by 1731
Abstract
Machine learning is gaining popularity in the commercial world, but its benefits are yet to be well-utilised by many in the microfluidics community. There is immense potential in bridging the gap between applied engineering and artificial intelligence as well as statistics. We illustrate [...] Read more.
Machine learning is gaining popularity in the commercial world, but its benefits are yet to be well-utilised by many in the microfluidics community. There is immense potential in bridging the gap between applied engineering and artificial intelligence as well as statistics. We illustrate this by a case study investigating the sorting of sperm cells for assisted reproduction. Slender body theory (SBT) is applied to compute the behavior of sperm subjected to magnetophoresis, with due consideration given to statistical variations. By performing computations on a small subset of the generated data, we train an ensemble of four supervised learning algorithms and use it to make predictions on the velocity of each sperm. Our results suggest that magnetophoresis can magnify the difference between normal and abnormal cells, such that a sorted sample has over twice the proportion of desirable cells. In addition, we demonstrated that the predictions from machine learning gave comparable results with significantly lower computational costs. Full article
(This article belongs to the Special Issue Magnetic Fields in Microfluidic Systems)
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Open AccessCommunication
Solid-State NMR Characterization of the Structure of Self-Assembled Ile–Phe–OH
Magnetochemistry 2018, 4(3), 30; https://doi.org/10.3390/magnetochemistry4030030 - 29 Jun 2018
Cited by 2 | Viewed by 1622
Abstract
Solid-state nuclear magnetic resonance (NMR) spectroscopy provides significant structural information regarding the conformation and dynamics of a variety of solid samples. In this study, we recorded the 13C and 15N solid-state NMR spectra of a self-assembled isoleucine-phenylalanine (Ile–Phe–OH) dipeptide. Immediately after [...] Read more.
Solid-state nuclear magnetic resonance (NMR) spectroscopy provides significant structural information regarding the conformation and dynamics of a variety of solid samples. In this study, we recorded the 13C and 15N solid-state NMR spectra of a self-assembled isoleucine-phenylalanine (Ile–Phe–OH) dipeptide. Immediately after the addition of hexane to a solution of concentrated peptide in ethyl acetate, the peptide visually aggregated into a nanofiber. Then, we obtained well-resolved 13C and 15N NMR signals of the natural, isotopic-abundant Ile–Phe–OH peptide in the nanofiber. Furthermore, we calculated the chemical shift values of the reported crystal structure of the Ile–Phe dipeptide via the density functional theory (DFT) calculation and compared these results with the experimental values. Notably, the two sets of values were in good agreement with each other, which indicated that the self-assembled structure closely reflected the crystal structure. Therefore, herein, we demonstrated that solid-state NMR characterization combined with DFT calculations is a powerful method for the investigation of molecular structures in self-assembled short peptides. Full article
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Open AccessArticle
Synthesis, Crystal Structures, and Magnetic Properties of Lanthanide (III) Amino-Phosphonate Complexes
Magnetochemistry 2018, 4(3), 29; https://doi.org/10.3390/magnetochemistry4030029 - 22 Jun 2018
Cited by 2 | Viewed by 1546
Abstract
Two isostructural lanthanide amino-phosphonate complexes [Ln103-OH)3(µ-OH)(CO3)2(O2CtBu)15(O3PC6H10NH2)3(O3PC6H10NH3)2(H2 [...] Read more.
Two isostructural lanthanide amino-phosphonate complexes [Ln103-OH)3(µ-OH)(CO3)2(O2CtBu)15(O3PC6H10NH2)3(O3PC6H10NH3)2(H2O)2][Et2NH2] (Ln = Gd(III), 1 and Tb(III), 2) have been obtained through reflux reactions of lanthanide pivalates with, a functionalized phosphonate, (1-amino-1-cyclohexyl)phosphonic acid and diethylamine (Et2NH) in acetonitrile (MeCN) at 90 °C. Both compounds have been characterized with elemental analysis, single-crystal X-ray diffraction methods, and magnetic measurements. The molecular structure of compounds 1 and 2 reveal two highly unsymmetrical complexes comprising ten lanthanide metal centers, where the lanthanide metal ion centers in the cages are linked through pivalate units and further interconnected by CPO3 tetrahedra to build the crystal structure. The magnetic behavior of 1 and 2 was investigated between ambient temperature and ca. 2 K, the magnetic measurements for compound 1 suggests antiferromagnetic interactions between the Gd(III) metal ion centers at low temperatures. The large number of isotropic Gd(III) ions comprising 1 makes it a candidate for magnetocaloric applications, thus the magnetocaloric properties of this molecular cage were investigated indirectly through isothermal magnetisation curves. The magnetic entropy change was found to be 34.5 J kg−1K−1, making 1 a plausible candidate in magnetic cooling applications. Full article
(This article belongs to the Special Issue A Themed Issue in Honor of Late Professor Samiran Mitra)
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