In the history of magnetochemistry development, lanthanide-transition (3d–4f) heterometallic compounds have been considered an attractive candidate for magnetic refrigerants. Herein, a series of heterometallic compounds have been designed and templated by C2O42− anions, that is, {[Ln2Ni(L)(C2O4)2(H2O)2]·H2O}n [Ln = GdIII (abbr. Gd2Ni) = SmIII (abbr. Sm2Ni) = TbIII (abbr. Tb2Ni), H2C2O4 = oxalic acid; H4L = ethylene diamine tetraacetic acid]. The structural analysis reveals that Ln2Ni compounds feature a C2O42−-templated wavy-shaped two-dimensional layer. Then, adjacent wavy-shaped layers are further aggregated by C2O42− anions, resulting in an innovative three-dimensional metal–organic framework. Magnetization analysis revealed that Gd2Ni exhibits a favorable −ΔS maxm of 38.0 J kg−1 K−1 at 2.0 K for 7.0 T. In addition, the effect of weak ferromagnetic exchange interactions in Gd2Ni contributes to a decent magnetocaloric effect at low fields (−ΔSm = 25.1 J kg−1 K−1 at 2.0 T for 2.0 K and −ΔSm = 14.5 J kg−1 K−1 at 1.0 T for 2.0 K), outperforming most 3d–4f heterometallic compounds reported previously. [ABSTRACT FROM AUTHOR]
Doudin, Bernard, Coey, Michael, and Cēbers, Andrejs
Subjects
Magnetochemistry, Magnetism in Life Science, Magnetohydrodynamics, Magnetic Soft Matter, Magnetic Flow Control, Magnetophoresis, Magnetic Separation, Magnetic Nano- and Microactuators, Exchange Dynamics, Magnetic Nanoparticles, Cytoskeletal Filaments, Magnetically Actuated Artificial Cilia, Magnetolithography, Magnetically-Actuated Membranes, Electricity, electromagnetism and magnetism, Electronics engineering, Electrochemistry and magnetochemistry, Engineering applications of electronic, magnetic, optical materials, Biophysics, Materials science
Abstract
This open access book presents the most recent advances in the novel, interdisciplinary field of magnetic microhydrodynamics. This emerging area of advanced research combines magnetism with the knowledge of bioinspired local flow control to create novel concepts and technological solutions that could revolutionize the field of microfluidics. Edited and authored by world-recognized leaders in this field, this book covers how the action of magnetic forces on soft matter can result in a richness of possible static and dynamic behavior. The contributions featured in this book introduce timely examples of novel concepts (new fluids and control), processes at interfaces (local probes, electrochemistry), and applications of magnetic soft matter in cell biology, cargo transport, and energy. This book is of great interest to scientists from various backgrounds looking to explore, learn of recent developments, and take part in laying the foundations of an entirely new and dynamic field of research.
The prediction of paramagnetic NMR (pNMR) chemical shifts in molecules containing heavy atoms presents a significant challenge to computational quantum chemistry. The importance of meeting this challenge lies in the central role that NMR plays in the structural characterisation of chemical systems. Hence there is a need for reliable assignment and prediction of chemical shifts. We have developed code in MATLAB that facilitates this, based on the decomposition of the magnetic moment matrices by irreducible tensor operators (ITO) as outlined in the work of van den Heuvel and Soncini. This work firstly presents a published paper that studies the effect of zero-field-splitting (ZFS). It is shown that the inclusion of ZFS can produce substantial shifts in the predicted chemical shifts. The computations presented are typically sufficient to enable assignment of experimental spectra. However for one case, in which the peaks are closely clustered, the inclusion of ZFS re-orders the chemical shifts making assignment quite difficult. We also observe, and echo, the previously reported importance of including the paramagnetic spin-orbit hyperfine interaction for carbon-13 and silicon-29 atoms, when these are directly bound to a heavy element and thus subject to heavy-atom-light-atom (HALA) effects. Then we study the magnetic properties of U(DOTA), and three axially substituted variants. This is achieved by calculating the main magnetic matrices and paramagnetic NMR (pNMR) spectra. U(DOTA) has two suggested assignments for its proton spectra and our calculations allow a definitive assignment. The complications due to large spin-orbit coupling (SOC) and the interchange between the square antiprism (SAP) and twisted square antiprism (TSA) conformers are discussed. The axial symmetry of the molecule allows the tensor decomposition technique to be used to model the Zeeman contribution, and this results in strong correlation between calculated and experimental results. Experimental assignments for the axially substituted variants do not distinguish between protons attached to the same carbon atom, and we are able to separate these. The binding of a water ligand has little effect on the calculated spectra, but binding an anionic ligand results in a compression of the spectral range which our results duplicate. Binding an anionic ligand also causes the anisotropy axis to rotate by 90 degrees. These effects are examined with reference to spin density. Finally carbon-13 spectra are predicted for future experimental verification. The applicability of the new method of calculating paramagnetic NMR shifts is extended to another class of very heavy element compounds --- some substituted actinocene complexes. The initial results aimed at assigning published experimental NMR data are presented and our implementation of the ITO model is considered as promising.
Boukhvalov, Danil W., Osipov, Vladimir Yu., Serikkanov, Abay, and Takai, Kazuyuki
Subjects
TRANSITION metal ions, MAGNETIC structure, DIAMOND surfaces, MAGNETIC moments, ELECTRON density, COPPER, GADOLINIUM
Abstract
In this study, we conducted a theoretical simulation to compare the effects of various factors on the atomic and electronic structures and the magnetic properties of copper and gadolinium ions bonded to carboxylated species of (111) diamond surfaces. It was experimentally found that in the temperature range above 120 K, the magnetic moments of chelated Gd3+ and Cu2+ equal 6.73 and 0.981 Bohr magnetons, respectively. In the temperature range from 12 to 2 K, these magnetic moments sharply decrease to 6.38 and 0.88 Bohr magnetons. Specifically, we examined the effects of the number of covalent adatom–diamond substrate bridges, coordination of water molecules, and shallow carbon-inherited spins in the substrate on the physical properties of the metal center. Our simulation predicted that increasing the number of bonds between the chelated metal ion and substrate while decreasing the number of coordinating water molecules corresponded to a decrease in the magnetic moment of metal ions in a metal–diamond system. This is due to the redistribution of the electron charge density in an asymmetric metal–diamond system. By comparing our theoretical results with experimental data, we proposed configurations involving one and, in a minor number of cases, two surface –COO− groups and maximum coordination of water molecules as the most realistic options for Cu- and Gd-complexes. [ABSTRACT FROM AUTHOR]
Chernavin, Platon A., Letyagin, Gleb A., Tolstikov, Svyatoslav E., Kolesnikov, Andrey E., Romanenko, Galina V., Smirnova, Kristina A., Borodulina, Alexandra V., Ovcharenko, Victor I., and Bogomyakov, Artem S.
A series of pyridyl‐substituted nitronyl nitroxides was synthesized and structurally characterized. A comprehensive magnetochemical and quantum chemical study of extended raw of the nitroxides with different substituents R in the pyridine fragment was performed. It was shown, that temperature‐dependent magnetic properties are determined by the short contacts between nitroxide groups of adjacent molecules as well as between nitroxide group and methyl substituents in the pseudo axial positions of imidazoline fragments. Quantum chemistry allows to select the appropriate model of exchange cluster for analysis of experimental magnetic data and evaluation of the exchange interaction parameters. For NN–PyCl the "order‐disorder" transition was detected by means of low temperature XRD. The difference in the experimental and calculated exchange interaction energies may serve as an indicator of temperature‐induced structural rearrangements. For instance, for methyl substituted nitronyl nitroxide NN‐PyMe structural transformations and significant changes in exchange interaction energies were observed. [ABSTRACT FROM AUTHOR]
Kragskow, Jon, Chilton, Nicholas, and Mills, David
Subjects
Spin-phonon coupling, Computational chemistry, Magnetochemistry, Single Molecule Magnets, Chemistry
Abstract
Single-molecule magnets (SMMs) are molecules which retain their magnetic moment without the need for an applied magnetic field. Their development has reached a rapid pace in the last few years, though their properties are only able to be exploited far below room temperature. Popular models exist, and are routinely employed, to maximise the potential magnetic properties of novel compounds, though these rely on a static viewpoint of an inherently dynamic process. To fully model magnetic relaxation in SMMs one must understand the coupling of a molecule's electronic spin with its spatial degrees of freedom (vibrational/phonon modes) since this dictates the operational temperature of an SMM. In order for this spin-phonon or vibronic coupling to be controlled through molecular design we must have a solid understanding of, and ability to calculate, the underlying physics of SMMs. This thesis describes the development of protocols and computer code for carrying out calculations of spin-phonon coupling in a range of lanthanide SMMs. The resulting coupling values are critically assessed by comparison to data obtained from both magnetometry and spectroscopy experiments. Throughout this process, structure-property relationships are uncovered in wellknown SMM families, and some simple design protocols are formulated, paving the way for a more comprehensive understanding of spin-phonon coupling in SMMs.
Danil W. Boukhvalov, Vladimir Yu. Osipov, Abay Serikkanov, and Kazuyuki Takai
Subjects
diamond surface, chelate complexes, 3d and 4f transition metal ions, electron density distribution, magnetization, magnetochemistry, Organic chemistry, QD241-441
Abstract
In this study, we conducted a theoretical simulation to compare the effects of various factors on the atomic and electronic structures and the magnetic properties of copper and gadolinium ions bonded to carboxylated species of (111) diamond surfaces. It was experimentally found that in the temperature range above 120 K, the magnetic moments of chelated Gd3+ and Cu2+ equal 6.73 and 0.981 Bohr magnetons, respectively. In the temperature range from 12 to 2 K, these magnetic moments sharply decrease to 6.38 and 0.88 Bohr magnetons. Specifically, we examined the effects of the number of covalent adatom–diamond substrate bridges, coordination of water molecules, and shallow carbon-inherited spins in the substrate on the physical properties of the metal center. Our simulation predicted that increasing the number of bonds between the chelated metal ion and substrate while decreasing the number of coordinating water molecules corresponded to a decrease in the magnetic moment of metal ions in a metal–diamond system. This is due to the redistribution of the electron charge density in an asymmetric metal–diamond system. By comparing our theoretical results with experimental data, we proposed configurations involving one and, in a minor number of cases, two surface –COO− groups and maximum coordination of water molecules as the most realistic options for Cu- and Gd-complexes.
Three novel five-coordinated bis-dioxolene cobalt complexes were synthesized and characterized by single crystal X-ray diffractometry and magnetochemistry. Structural study indicates square-pyramidal coordination geometry around cobalt ion. Structural parameters of coordinated dioxolenes together with magnetic measurements and DFT calculation data characterize compounds as mixed valence catecholato-semiquinonate derivatives of low spin cobalt(III). Magnetic moment of complex based on methoxy-substituted dioxolene grows at the temperatures above 260 K that can be interpreted as valence tautomeric/spin-crossover transition. This transition is not completed at the temperature 350 K. [ABSTRACT FROM AUTHOR]
The focus of this dissertation is the thorough analysis of the effects of dipolar coupling on magnetic relaxation behavior within erbium-based molecular magnets. Utilizing the Er-COT unit as the starting point and building block, we investigate intra- and inter-molecular dipolar coupling motifs generated with analogous highly anisotropic building block units. Each chapter holds a specific focus, organized as follows: Chapter 1 offers a brief introduction to molecular magnetism, followed by an overview of topics necessary towards understanding magnetic relaxation in the scope of this work, including energy perturbations, relaxation dynamics, and anisotropy; an introduction to the Er-COT unit and coupling schemes in lanthanide-based molecular magnetism, and the motivation for investigating dipolar coupled systems. The chapter concludes with extended chapter summaries for the remainder of this work.Chapter 2 focuses on the role and effects of intramolecular dipolar coupling in a series of compounds of increasing nuclearity. This work demonstrates the ability of intramolecular dipolar coupling to control quantum tunnelling of magnetization, and thus the rate and mechanism of magnetic relaxation. This chapter utilizes an expanded frequency space magnetometry technique to garner new insights into magnetic relaxation by visualizing, fitting, and analyzing multiple relaxation regimes. The chapter concludes with an intuitive model of thought based on a simple vector addition model, within which spin interactions can be estimated directly from a crystal structure.Chapter 3 discusses the effects of intermolecular dipolar coupling within a series of identical single-ion magnets within varied crystal packing environments. This work depicts the propensity of intermolecular dipolar coupling to drive dramatic differences in resulting magnetic behavior and seeks to shed light on the relationship between single-ion magnetism and solid-state magnetism. This chapter applies a novel fitting methodology to quantify additional parameters from isothermal magnetization data for downstream analysis. Chapter 4 presents the analysis of a highly symmetric, near-tetrahedral tetranuclear single-molecule magnet to discuss the effects of crystallographic symmetry on the resulting dipole-coupled spin-space symmetry. This chapter discusses the ensuing available rhombic dodecahedral quantum space of this molecule, composed of octahedral and cubic subspaces, and makes connections to theoretically proposed quantum Cayley networks upon hypercubes.
Some animals are known to be able to react to very small changes in the magnetic field (a thousand times smaller than the geomagnetic field) and to use this ability to navigate the Earth's magnetic landscape. However, the nature of the molecular sensor of the magnetic field remains uncertain, though it has been established that the magnetic sense is associated with vision. A magnetochemical reaction is believed to underlie the functioning of the magnetic sensor. The cryptochromes of photoreceptors lining the retina contain photoinduced spin-correlated pairs of radicals which are involved in forming nerve impulses and are sensitive to magnetic fields. On this basis, animals may sense the magnetic field as changes in brightness over large visual fields, and orient themselves in terms of the contrast of these fields. However, the sensitivity of individual sensors – radical pairs – is very low. It has previously been supposed that this difficulty is overcome by a statistical increase in contrast sensitivity due to the parallel processing by the brain of the primary signals of millions of photoreceptors. We report here testing of this hypothesis. The threshold sensation of brightness contrast was found to depend almost linearly on the logarithm of the angular size of the contrasting stimulus, which is typical for the physiology of sensations obeying the Weber–Fechner law. Contrast sensitivity increases with increases in the number of photoreceptors involved in stimulus recognition, though this increase is quantitatively insufficient to provide a confident explanation of magnetic navigation in animals. [ABSTRACT FROM AUTHOR]
Magnetic effects across biochemistry, molecular biology and environmental chemistry: Genes, brain and cancer under magnetic control provides an overview of the influence of magnetism upon molecular and biochemical processes and its impact on disease, health and organisms.This book provides an understanding of key concepts behind magnetic fields before exploring their biological significance. It elucidates when and why magnetic effects arise, how they function, and how they can be utilized. Molecular mechanisms underlying magnetic effects and the impact of magnetism on genes are explored. Additionally, magnetic control in treatment of diseases, including cancer, heart disease, and neurological disease is investigated. This book explores a rapidly developing and intriguing field of science, providing a basis for future study in the field of magneto-biology, and is a useful reference for researchers across biochemistry, molecular biology, biophysics and related fields.• Explores the mechanisms of magnetic fields and magnetic isotope effects at a molecular and biochemical level • Identifies key background concepts and function of magnetic fields across biology and chemistry • Covers magnetic control in the context of genes, including key processes such as DNA synthesis, magnetically induced DNA damage, and magnetic control of DNA repair • Demonstrates a new, radical pair mechanism as a means to stimulate ATP synthesis in living organisms for prevention of diseases
Claisen and Cope rearrangements are [3,3]-sigmatropic rearrangements thermally activated that occur through six-membered transition states. Although extensively investigated for decades, little is known about the magnetochemistry of these rearrangements. In view of this, we carried out an investigation based on chemical-computational models through methods based on Density Functional Theory, QTAIM, Multicenter Bond Order, NCI, GIAO, and GIMIC. We demonstrated that CCR mechanisms are concerted in which the 6-membered cyclic transition states present high aromaticity character. The molar and anisotropic susceptibility, NICS(1), and NICSzz signals were verified to have a good correlation with J (nA T−1). However, these indices demonstrated insufficient to evaluate the magnitudes of aromaticity in these transition states. Among the magnetic and topological descriptors applied in this work, the magnetically induced current density (J) proved, this to be an excellent strategy for theoretically estimative of the aromaticity of the transition states involved in the investigated rearrangements. Among the rearrangements with chair conformation, it was noted that the higher aromaticity is associated with the less favoured kinetics. For chair conformations, Claisen rearrangement (TS2) presents J = 8.63 nA T−1 and Cope (TS4) presents J = 10.43 nA T−1. However, the following order of aromaticity TS4 > TS2 > TS3 > TS1, with high paramagnetic currents in the boat conformations reducing the total current in the ring, suggests that it is not possible to establish a direct correlation between aromaticity and the kinetics of the Cope and Claisen rearrangements, since the most stable transition estate geometries are not necessarily the most aromatic. [ABSTRACT FROM AUTHOR]
Cu(II), Ni(II), Zn(II), Co(II), Fe(II), Mn(II) carboxylates containing a pharmacophoric glycoluril fragment were obtained for the first time. The proposed structure of the complexes was established using elemental analysis, spectral methods, and magnetochemistry. Structure of one of the copper(II) complexes was proved by X-ray diffraction analysis. Antibacterial and fungicidal activity of all the compounds was studied. It was shown that the starting acids are inactive, while some complexes exhibit antibacterial activity. [ABSTRACT FROM AUTHOR]
Thanks to the efforts of our reviewers in 2022, the median time to first decision was 14 days and the median time to publication was 36 days. Regardless of whether the articles they examined were ultimately published, the editors would like to express their appreciation and thank the following reviewers for the time and dedication that they have shown I Magnetochemistry i : HT
A. I Magnetochemistry i was able to uphold its high standards for published papers due to the outstanding efforts of our reviewers. [Extracted from the article]
New heteroligand cobalt(III) bis-3,6-di-tert-butyl-o-benzosemiquinone complexes with p-tolyl-substituted formazan ligands Co(3,6-SQ)2Ln (L1H is 1,5-diphenyl-3-p-tolylformazan (I), L2H is 1,3,5-tri-p-tolylformazan (II), and L3H is 3-nitro-1,5-di-p-tolylformazan (III)) are synthesized and characterized. The molecular structures of compounds I, II, and III in the crystalline state are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2161722 (I), 2167094 (II), and 2167095 (III)). According to the XRD results and magnetic and spectral measurement data, compounds I–III are complexes of low-spin cobalt(III) bound to two radical anion o-semiquinone ligands and one formazan anion. The magnetic behavior of the complexes in a temperature range of 2–300 K is characterized by intramolecular antiferromagnetic exchange interactions between the o-semiquinone ligands. The replacement of the phenyl substituents by p-tolyl groups in positions 1 and 5 of the diamagnetic formazanate ligand results in a significant enhancement of the exchange between the radical centers. [ABSTRACT FROM AUTHOR]
The book covers the entire spectrum of magnetic nanomaterials and their highly interesting properties. Keywords: Magnetic Nanomaterials, Analytical Chemistry, Biomedical Science, Spintronics, Electrochemistry, Energy Storage, Energy Conversion, Membranes, Fuel Cells, Bio-Sensors, Electrocatalysis, Separation Processes, Hydrogen Storage, Supercapacitors, SERS Effect.
Vadapalli Chandrasekhar, Fabrice Pointillart, Vadapalli Chandrasekhar, and Fabrice Pointillart
Subjects
Organometallic compounds, Magnetochemistry
Abstract
This volume highlights the recent advances and state of art in the experimental and theoretical studies of organometallic magnets. A plethora of organic ligands such as Mannich-base derivatives, redox-active chromophores, cyanides, Schiff base among others are used to coordinate to 3d transition metals, 4f lanthanides and 5f actinides to design the molecular magnets. Deep analysis of the coordination sphere symmetry, electronic distribution, luminescence are investigated to perform magneto-structural correlation leading to a better understanding of the magnetic properties. Furthermore, the rationalization of the magnetic behavior can be reached using ab initio calculations. The multiple applications that these molecular magnets offer could revolutionize the high-density data storage, spintronics and quantum computing technologies. This volume provides a discussion of these topics from leading international experts and will be a useful reference for researchers working in this field.
Keywords: 2,5-dihydroxy-1,4-quinone; cyclic voltammetry; phoshine; phosphinyl; X-ray structures EN 2,5-dihydroxy-1,4-quinone cyclic voltammetry phoshine phosphinyl X-ray structures 531 541 11 07/18/22 20220701 NES 220701 1 Introduction Coordination complexes built around the structural motif of 2,5-bis(phosphine) I p i -hydroquinone are relatively rare. SP 31 sp P NMR (C SB 6 sb D SB 6 sb ): I i = 73.3 (s). 4.3.4 Syntheses of 2,5-bis(diphenylphosphinyl)-3,6-hydroquinone (4a) and 2,5-bis(diisopropylp... Both compounds were synthesized by the same procedure, thus a detailed description of only one of them ( B 4a b ) is provided. Reported herein are syntheses and investigations for two of such compounds, 2,5-bis(diphenylphosphinyl)-3,6-dihydroxy-quinone ( B 4a b ) and 2,5-bis(diisopropylphosphinyl)-3,6-dihydroxy-quinone ( B 4b b ) (Figure 2). Thus, crystals of 2,5-dihydroxy-1,4-quinone and 2,5-dihydroxy 3,6-dichloro-1,4-quinone contain I intermolecular i hydrogen bonding between hydroxy groups and oxygens of quinone functionalities [[28]]. [Extracted from the article]
Gautam, Bishal, Nabat Al-Ajrash, Saja M., Hasan, Mohammad Jahid, Saini, Abhishek, Watzman, Sarah J., Ureña-Benavides, Esteban, and Vasquez-Guardado, Erick S.
Subjects
MAGNETIC suspension, THERMAL conductivity, MAGNETOCHEMISTRY, NANOCOMPOSITE materials, THERMOGRAVIMETRY
Abstract
This document is a correction notice for an article titled "Experimental Thermal Conductivity Studies of Agar-Based Aqueous Suspensions with Lignin Magnetic Nanocomposites" published in the journal Magnetochemistry. The correction addresses a unit error in Figure 5, where the x-axis label should have been in Kelvin (K) instead of Celsius (°C). The authors apologize for any inconvenience caused and assure that the scientific conclusions remain unaffected. The corrected figure has been included in the updated publication. [Extracted from the article]
EFFECT of radiation on skin, MAGNETOCHEMISTRY, FREE convection, RADIATION chemistry, NANOFLUIDS
Abstract
The document titled "Comment on Vishalakshi et al. MHD Hybrid Nanofluid Flow over a Stretching/Shrinking Sheet with Skin Friction: Effects of Radiation and Mass Transpiration" criticizes two errors in a previous publication. The first error is related to an incorrect gravity term in an equation, which violates the known physics principle that gravity acts in the vertical direction. The second error involves a dimensional inconsistency in an equation, where some parameters are dimensionless while one parameter is dimensional. The document concludes by stating that the authors have no conflicts of interest. [Extracted from the article]
van Leusen, Jan, Speldrich, Manfred, Kögerler, Paul, Beller, Matthias, Series Editor, Dixneuf, Pierre H., Series Editor, Dupont, Jairton, Series Editor, Fürstner, Alois, Series Editor, Glorius, Frank, Series Editor, Gooßen, Lukas J., Series Editor, Nolan, Steven P., Series Editor, Okuda, Jun, Series Editor, Oro, Luis A., Series Editor, Willis, Michael, Series Editor, Zhou, Qi-Lin, Series Editor, Chandrasekhar, Vadapalli, editor, and Pointillart, Fabrice, editor
[Display omitted] This survey describes recent achievements in creating a new type of materials – nanodiamonds grafted with atoms of transition metals. Structural features of some selected chelate complexes studied by density functional theory, their scope and limitations as well as possible applications are discussed. Using the example of copper ions, their location relative to subsurface defects of detonation diamond is investigated by the method of electron paramagnetic resonance (EPR). [ABSTRACT FROM AUTHOR]
Complexes [Сu2L4(MeOH)2] (I) and [СoL2] (II) are synthesized by the reactions of copper(II) and cobalt(II) acetates with 3-[5-p-tolyl)-1,3,4-oxadiazol-2-yl]acrylic acid (HL). The crystal structure of complex I is determined by X-ray diffraction (XRD) (CIF file CCDC no. 2052347). The crystals are monoclinic, space group C2/c, a = 26.056(4), b = 19.677(3), c = 13.998(2) Å, β = 91.571(3)°, V = 7175(2) Å3, ρcalc = 1.026 g/cm3, Z = 4. In a molecule of complex I, the pair of centrosymmetric copper atoms is bound by four bridging carboxyl groups. The intramolecular Cu...Cu distance is 2.654(2) Å. The coordination polyhedron CuO5 is a distorted square pyramid. The magnetic interactions between the copper(II) ions in complex I are shown to be antiferromagnetic (2J = –185 cm–1). In the case of complex II, the application of an external magnetic field decreases the magnetic relaxation rate. The Raman mechanism and direct mechanism are the most probable route for magnetization relaxation. Unlike the copper(II) complex, complex II is probably mononuclear in both the solution and solid phase. [ABSTRACT FROM AUTHOR]
Researchers at Zhejiang University in Hangzhou, China, have developed a new method to optimize the magnetic separation and cleaning module in fully automated chemiluminescence immunoassay analyzers. By arranging spliced rectangular magnets with the same polarity facing each other and implementing a three-stage magnetic bead collection method, they were able to significantly reduce magnetic bead loss rate, cleaning time, and improve cleaning efficiency. This innovative approach enhances the accuracy of disease biomarker detection in CLIA analyzers and provides a reference for similar modules in the future. [Extracted from the article]
Although nanotechnology advances have been exploited for a myriad of purposes, including cancer diagnostics and treatment, still there is little discussion about the mechanisms of remote control. Our main aim here is to explain the possibility of a magnetic field control over magnetic nanocomplexes to improve their delivery, controlled release and antitumor activity. In doing so we considered the nonlinear dynamics of magnetomechanical and magnetochemical effects based on free radical mechanisms in cancer development for future pre-clinical studies. [ABSTRACT FROM AUTHOR]
New heteroligand cobalt(III) bis-3,6-di-tert-butyl-o-benzosemiquinone complexes with 1-(p-X-phenyl)-3,5-diphenylformazan ligands Co(3,6-SQ)2LX (Х is fluorine (I), chlorine (II), bromine (III), iodine (IV), and methyl (V)) are synthesized. The molecular structures of compounds I, II, and IV are determined by X-ray structure analysis (CIF files CCDC nos. 2060727 (I), 2052592 (II), and 2060728 (IV)). The coordination environment of the central cobalt ion in the studied complexes is a weakly distorted octahedron, and the degree of distortion insignificantly changes depending on the substituent. According to the X-ray structure data and results of magnetic and spectral studies, compounds I–V are low-spin complexes of cobalt(III) bound to two radical anion o-semiquinone ligands and one formazan anion. The magnetic behavior of complexes I–V in a temperature range of 50–300 K is characterized by the predomination of intramolecular exchange interactions of the antiferromagnetic type, whereas in the range lower than 50 K complexes II–V exhibit ferromagnetic ordering caused by intermolecular exchange interactions between the paramagnetic ligands. [ABSTRACT FROM AUTHOR]
Tupolova, Yu. P., Popov, L. D., Borodkin, S. A., Borodkin, G. S., Vlasenko, V. G., Zubavichus, Ya. V., Shcherbakov, I. N., Chetverikova, V. A., and Ivannikova, E. V.
The complex formation properties of the product 2-oxo-1,2-dihydroquinoline-3-carbaldehyde condensation with stearic acid hydrazide towards Cu(II) and Ni(II) ions has been studied. Composition and structure of the complexes has been found dependent on the nature of the metal and acid residue. The obtained compounds have been investigated by spectral methods, the temperature dependence of the magnetic susceptibility in constant magnetic field has been measured. Quantum-chemical simulation of possible isomers of N'-acylhydrazone in a solution has been carried out. [ABSTRACT FROM AUTHOR]
Vasilchenko, I. S., Vlasenko, V. G., Kuzmenko, T. A., Divaeva, L. N., Borodkin, G. S., Levchenkov, S. I., Zaichenko, S. B., Korshunova, E. V., Chalsev, B. V., and Burlov, A. S.
Abstract
New azomethine 1-(2-hydroxybenzylidenamino)benzimidazolinone-2 and Cu(II), Co(II) and Zn(II) complexes based on it are synthesized and studied. The structure of azomethine and metal complexes is found from the data of elemental analysis, infrared (IR) spectroscopy, 1H NMR spectroscopy, X-ray absorption spectroscopy, and magnetochemistry. It is shown that all complexes have a mononuclear structure with the general formula M(HL)2. For the copper complex, the weak antiferromagnetic-type exchange between copper ions is observed due to the formation of intermolecular hydrogen bonds N–H···O=C. [ABSTRACT FROM AUTHOR]
Smith, Charlene Amanda, Collison, David, and Layfield, Richard
Subjects
546, Magnetochemistry, Lanthanide Metal, Transition Metal, Single Molecule Mganets, Single Ion Magnets, Organometallics, Soft Ligands
Abstract
The introductory Chapter to this thesis outlines fundamental aspects of 4f lanthanide(III) coordination chemistry, in particular compounds that possess the intriguing properties of slow relaxation of magnetisation, (or the ability to behave as single-molecule magnets, SMMs). The recent renaissance into the study of the magnetic behaviour of 4f-coordination complexes has led to the consideration of utilising organometallic precursors for the development of novel lanthanide containing compounds, which may possess interesting magnetic properties, subsequently forming the basis of Chapter Two. In Chapter Two, the syntheses and structures of the novel lithiated thiolate ligand, lithium triphenylsilylthiolate, (Ph3SiS-Li) (2.1), and the sulfur-bridged, dimetallic dysprosium(III) and gadolinium(III) complexes [(MeCp)2Dy(µ-SSiPh3)]2 (2.2) and [(MeCp)2Gd(µ-SSiPh3)]2 (2.3), are described in detail. The structural and physical properties of these compounds are analysed through NMR, elemental analysis and SQUID magnetometry, alongside supporting theoretical calculations to reveal that compound 2.2 is the first dimetallic, sulfur-bridged SMM reported, giving an energy barrier to the reversal of magnetisation of Ueff = 192 ± 5 K.56bChapter Three reports on the structural development of a series of lanthanide monomers, exhibiting the general motif [Ln(OSiPh3)3(THF)3] (where Ln = Dy(3.4), Er(3.5), Ho(3.6), Gd(3.7), Tb(3.8)), exploiting the siloxide ligand Ph3SiOH through two novel synthetic routes. This Chapter also provides new analytical insight to these complexes by exploring their magnetic properties through a series of SQUID measurements and through the analysis of their electronic properties using air sensitive, variable temperature optical absorption spectroscopy. Compounds 3.4 and 3.5 were revealed to be SMMs, with 3.5 having a much higher thermal barrier to the reversal of magnetisation, Ueff = ~ 28 K, than 3.4, which are supported by theoretical analysis. Chapter Four describes the utility of ligand 2.1 and Ph3SiOH in the context of 3d transition metal cyclopentadienyl chemistry, outlining the syntheses and structures of three distinct compounds; the trimetallic, [Cp2Mn3(µ-OSiPh3)4](4.7), the hetero-cubane tetramer [CpMn(µ-SSiPh3)]4 (4.8) and the dimetallic thiolate-bridged [CpCr(µ-SSiPh3)]2 (4.9) compound. These compounds were formed in reactions exploiting organometallic manganocene and chromocene precursors. Magnetic susceptibility measurements were conducted on these compounds to gain further insight into their structural properties. The magnetic exchange coupling constants for Mn(II) compounds 4.7 and 4.8 were J = - 4.4 cm-1 and J = - 3.0 cm-1 respectively. Furthermore, having demonstrated the use of metal-cyclopentadienyl building blocks in the synthesis of novel SMMs, Chapter Five discusses the possibility of further advancement on the development of this class of magnetic molecules.
This thesis describes the synthesis and characterisation of metal complexes that contain chemically reduced bipyridyl ligands. The crystal structures of twenty-six novel complexes are reported alongside detailed discussions on the electronic and spectroscopic effects and trends associated with the different oxidation states within these species. Chapter One introduces the isomers of bipyridine and their redox chemistry, the concept of non-innocent ligands and the spectroscopic techniques that are currently used in determining ligand oxidation states. Subsequently, examples of main group, transition metal, lanthanide and actinide species that contain or may contain reduced forms of the ligand are discussed. Chapter Two details the synthesis and structural characterisation of alkali metal salts of singly and doubly reduced forms of the three commercially available bipyridine isomers. The effects of this reduction are investigated with the aim of developing diagnostic fingerprints for each of the ligand oxidation states. Chapter Three discusses the synthesis of an homologous series of compounds of the form [M(2,2'-bipy)(mes)2]n– where M = Cr, Mn, Fe, Co, Ni and n = 0, 1. Trends in magnetism, bonding and electronic structure are investigated with reference to theoretical calculations and the diagnostic fingerprints identified in the previous chapter. Chapter Four describes the synthesis and characterisation of three compounds containing the isostructural motif [Zn2(4,4'-bipy)(mes)4]n– where n = 0, 1, 2. Structural and spectroscopic changes are discussed and com- pared to theoretical calculations. Chapter Five contains descriptions of the spectroscopic techniques employed in the above research and synthesis routes to all compounds featured in this thesis.
Summary: The chemical reactions involving excited-state radical pairs (RPs) of parallel/anti-parallel spin configurations are sensitive to magnetic field, leading to the possibilities of magnetically controlled synthesis of chemical compounds. Here we show that the reaction of anthraquinone (AQ) in sodium dodecyl sulfate (SDS) micellar solution under UV excitation is significantly influenced by applying external field. The steady state and time-resolved spectroscopies reveal that the reaction intermediate (pairs of AQH-SDS radicals) can undergo two distinct pathways depending on whether it is spin singlet or triplet, and the field is beneficial to the conversion between spin configurations of RPs. The applied field not only affects the reaction rate constant but also changes the final products. Besides, the aggregation of AQ molecules would change the population of singlets and triplets and thus enhance magnetic field effect. This work represents a promising way of controlling chemical reaction and improving reaction selectivity via magnetic field methods.
MAGNETOCHEMISTRY, MAGNETIC moments, METAL complexes, TWENTIETH century, PHYSICISTS
Abstract
The spin-only magnetic moment formula, widely used for calculating the magnetic moment of some particular metal complexes, was developed by Debendra Mohan Bose, one of the pioneering physicists of the early twentieth century in India. The formula later became popular as the 'Bose-Stoner formula' as Edmund C. Stoner provided some theoretical explanations of its origin. [ABSTRACT FROM AUTHOR]
The propensity of the new, phenylphosphonate‐stabilized polyoxotungstate [(C6H5PVO)2P4W24O92]16− to act as a precursor for new 3d metal‐functionalized polyanions has been investigated. Reactions with MnII and CuII induce the formation of the previously unknown polyoxotungstate archetype {P4W27}, isolated as salts of the polyanions [Na⊂{MnII(H2O)}{WO(H2O)}P4W26O98]13− (1) and [K⊂{CuII(H2O)}{W(OH)(H2O)}P4W27O99]14− (2), which were characterized in the solid state (single‐crystal X‐ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry). [ABSTRACT FROM AUTHOR]
[Display omitted] Niobium carbide composites were obtained by sintering niobium powder and detonation nanodiamond at high pressure (7 GPa) and high temperature (∼1990 °C) for several tens of seconds. The resulting composites demonstrate a set of distinct reflections from the NbC phase in the X-ray diffraction pattern and exhibit superconducting properties at temperatures below 11.4 K. [ABSTRACT FROM AUTHOR]
Complexes of Cu (II), Ni (II), and Co (II) with hydrazone derivatives of salicylic acid hydrazide and 3,5-di-tert-butyl salicylic aldehyde (LH) were synthesized and the structure of these compounds studied by means of elemental analysis methods, IR and electronic spectroscopy, magnetochemistry and thermal analysis. It revealed that the complexes are monomeric and have a composition [MLXSoI] where M is a metal ion, L is a ligand, X is an inorganic anion, and Sol is a solvent molecule. LH- in the complexes behaves like a monoanionic tridentate ligand. It found that the resulting complexes exhibit noticeable inhibitory and urease activity. [ABSTRACT FROM AUTHOR]
Magnetochemistry, Electromagnetism--Physiological effect, Magnetic fields--Physiological effect, Magnetic fields--Health aspects, Human body--Magnetic fields
Abstract
Life is controlled by chemistry. Chemistry is not the whole life but the life is totally chemistry. Chemistry is a key to biology. Nothing in biology can be understood without chemistry and chemical reactions. There are many factors controlling biochemical reactions, however the most intriguing is the magnetic field. The ability to respond to magnetic fields is ubiquitous and universal among the five kingdoms of organisms. Magneto-biology is a field of knowledge which considers phenomena accompanying the influence of magnetic fields, permanent and alternating, on the biological systems at all levels: molecular, cellular, and whole organism. There is no doubt that magnetic fields do the human health and feeling of well-being; the latter is a key factor stimulating both social and scientific interest in magneto-biology. This book considers numerous biological and biomedical effects of the two magnetic fields: internal fields created by magnetic nuclei, and external magnetic fields, both permanent and oscillating. It critically summarizes magnetic effects on the biological clocks, biological compass for orientation and navigation of migrating animals, the influence of cells phones on the health. It demonstrates magnetic and isotope effects on the food chains and metabolism, ecology and epidemiology. It explains the origin of trans-cranial magnetic stimulation of cognitive processes to prevent neurodegenerative disorders; it enlightens magnetic stimulation of the ATP synthesis and protein phosphorylation, magnetic control of the DNA synthesis and gene expression. It shows how magnetic fields can be used to eliminate ATP deficiency at cardiac diseases and how to use magnetic stable isotope ions as the medical agents against hypoxia and cardiac insufficiency, as a means for controlling cell proliferation and stimulating destruction and apoptosis of the cancer cells. The uniqueness of this book is that it is focused on the chemical biology and medicine, on the discovery and analysis of chemical magneto-dependent mechanisms. This book gives a collection of scattered information, its critical analysis, generalization and explanation of physics and chemistry of magneto-biological effects as a basis for the deliberate usage in medicine (for the trans-cranial magnetic stimulation of cognitive processes and genetics, in particular).
This first introduction to the rapidly growing field of molecular magnetism is written with Masters and PhD students in mind, while postdocs and other newcomers will also find it an extremely useful guide. Adopting a clear didactic approach, the authors cover the fundamental concepts, providing many examples and give an overview of the most important techniques and key applications. Although the focus is one lanthanide ions, thus reflecting the current research in the field, the principles and the methods equally apply to other systems. The result is an excellent textbook from both a scientific and pedagogic point of view.
Popov, L. D., Levchenkov, S. I., Lukov, V. V., Gishko, K. B., Borodkin, S. A., Tupolova, Y. P., Askalepova, O. I., Vlasenko, V. G., Spiridonova, D. V., Lazarenko, V. A., Burlov, A. S., and Shcherbakov, I. N.
Subjects
*NUCLEAR magnetic resonance spectroscopy, *X-ray diffraction, *POTENTIOMETRY, *MAGNETOCHEMISTRY, *COMPLEX compounds
Abstract
The novel hydrazone, a condensation product of 2-N-tosylaminobenzaldehyde and Girard T reagent, as well as the Cu(II), Ni(II), Co(II) and Fe(III) complexes on its base were synthesized. The ligand structure and properties were studied with IR, UV, 1H NMR spectroscopy, mass-spectrometry, and potentiometry method. Structure of nickel(II) complex was determined by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]
New heteroligand cobalt(II), iron(II), and manganese(II) complexes of the M(3,6-SQ)2L type bearing 3,6-di-tert-butyl-o-benzosemiquinonato ligands (3,6-SQ) and 2,2'-biquinoline or 1,4-di-tert-butyl-1,4-diazabutadiene-1,3 as neutral ligands (L) have been synthesized and characterized. It was shown on the basis of the magnetic susceptibility measurements and spectroscopic studies that all complexes contain metal(II) ions in the high-spin state and two radical-anionic o-semiquinonato ligands. It was found in the result of analysis of magnetic susceptibility temperature dependence by magnetic coupling parameters modeling that the antiferromagnetic ligand-ligand coupling takes place in the cobalt(II) and iron(II) complexes, while antiferromagnetic metal-ligand interactions dominate in the manganese(II) complexes. [ABSTRACT FROM AUTHOR]
The pentanuclear nickel(II) complex [Ni5(saltagBr)2(tptz)4] (Ni5) with the tritopic triaminoguanidine‐derived Schiff‐base ligand H5saltagBr (1,2,3‐tris[(5‐bromosalicylidene)amino]guanidine) and tptz (2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine) as capping ligands is reported. Ni5 crystallizes in the triclinic space group P1 with the central nickel(II) ion linking two triangular arrangements of nickel(II) ions supported by two tritopic triaminoguanidine ligands. The octahedral coordination of the four peripheral nickel(II) ions is complemented by capping tridentate tptz ligands. By variation of the synthesis also the corresponding trinuclear nickel(II) complex [Ni3(saltagBr)(tptz)3]NO3 (Ni3) is accessible. Magnetic measurements for Ni3 and Ni5 reveal a singlet ground state with antiferromagnetic coupling between the nickel(II) ions, which in the case of Ni5 can only be simulated assuming a two‐J exchange coupled spin topology. For both complexes significant zero‐field splitting for the nickel(II) ions is evident from the measured magnetic data, which can be verified by theoretical studies revealing a magnetic anisotropy with strong rhombic distortion due to the presence of the tptz co‐ligands in both compounds. [ABSTRACT FROM AUTHOR]
The reaction of metal hexafluoroacetylacetonates M(hfac)2, where M = Fe, Mn, and Co, with 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) in the inert atmosphere of a dry box is found to yield mixed-ligand complexes [M(hfac)2(3,6-Q)]. When the synthesis is performed under ambient conditions or the [M(hfac)2(3,6-Q)] mother liquor is kept in air in the case of Mn(II) and Co(II), crystals of [M(hfac)2(H2O)2](3,6-Q) aqua complexes precipitate into the solid phase, in which cis-coordinated H2O molecules are hydrogen bonded to o-quinone O atoms. Single crystal X-ray diffraction data for compounds, which correlate with the results of quantum chemical calculations, show that solid [M(hfac)2(3,6-Q)] and [M(hfac)2(H2O)2](3,6-Q), where M = Co(II) and Mn(II), contain initial o-quinone molecules. In the interaction of Fe(hfac)2 with 3,6-Q, there is an intramolecular redox process during which Fe(II) is oxidized to Fe(III) and o-quinone is reduced to the respective semiquinonate radical anion, which leads to the formation of [FeIII(hfac)2(3,6-SQ)]. According to the data of magnetic measurements, a strong antiferromagnetic exchange between high-spin Fe(III) unpaired electrons and SQ provide an almost complete compensation of spin of one of the unpaired electrons of the metal ion by SQ spin. For Co a complex with 3,5-di-tert-butyl-o-benzoquinone [Co(hfac)2(3,5-Q)] is also synthesized and its structure and magnetic properties are studied. The latter prove to be similar to those of [Co(hfac)2(3,6-Q)]. [ABSTRACT FROM AUTHOR]
*MAGNETOCHEMISTRY, *POLYCRYSTALS, *GADOLINIUM, *PHYSIOLOGICAL effects of temperature, *LANTHANUM
Abstract
A procedure has been developed to directly measure the adiabatic temperature change of amorphous melt-spun Fe-based ribbons displaying attractive room temperature magnetocaloric properties. Polycrystalline Gd ribbons are used as a reference material to compensate for the contribution of the sample holder to the experimental values. Fe78B12Cr8Ce2 and Fe75B12Cr8Ce5 melt-spun ribbons exhibited a peak adiabatic temperature change (ΔTadpk) ∼ 58% larger than Co82.9Si5.9Fe4.5Cr4B2.7 amorphous ribbons. The ΔTadpk in Fe78B12Cr8Ce2, Fe75B12Cr8Ce5, and Fe79B12Cr8La1 ribbons displayed ∼ 18-33% enhanced ΔTadpk compared to a GdAl2 alloy. [ABSTRACT FROM AUTHOR]
The effects of V doping on field-cooled magnetization MFC(T), zero-field-cooled magnetization MZFC(T), resistivity ρ, thermoelectric power S, and thermal conductivity κ in manganites CaMn1-xVxO3 (0.02<=x<=0.08) have been investigated systematically. As the V doping level exceeds 0.02, an anomalous “diamagnetism” has been observed. It is suggested that the force generated by the orbit rotation of eg electron in Mn3+O6 octahedron makes the spin tilt, as a result, the vector sum of individual spins may be along or opposite to the direction of the applied magnetic field, and macroscopically, the average magnetization exhibits positive or negative values. In addition, the transport mechanism in the high and low temperature ranges is dominated by the small polaron conduction and the variable-range-hopping conduction, respectively, according to the fitting analysis of the temperature dependence of Seebeck coefficient S(T) and resistivity ρ(T). Both S and κ peaks appearing at low temperature is gradually suppressed by V doping. Additionally, obvious magnetothermoelectric power and magnetothermal conductivity are observed in the temperature region which an anomalous diamagnetism appears. The results are discussed based on spin-orbital coupling and spin-phonon coupling induced due to V doping, respectively. Moreover, the large thermoelectric figure of merit Z=S2/ρκ for the slightly V-doped sample suggests that the V-doped manganite may be a good candidate for thermoelectric materials. [ABSTRACT FROM AUTHOR]
Despite the huge magnetic-field-induced strain (MFIS) of up to 9.5% exhibited by certain Ni–Mn–Ga alloys, their usefulness in applications is severely hindered by the electromagnet device needed for driving the alloys with a magnetic field and orthogonal loading stress. In this paper we present macroscopic measurements obtained from a single crystal of Ni50Mn28.7Ga21.3 which demonstrate a large reversible MFIS of -4100 ppm when the alloy is driven with quasistatic magnetic fields and fixed compressive stresses applied collinearly along the [001] axis. This collinear configuration marks a fundamental difference with prior research in the field and points to the existence in this alloy of stable bias or residual stresses—likely associated with pinning sites in the alloy—which provide the energy necessary to restore the original variant state when the field is reversed. We present macroscopic magnetomechanical measurements which show a decrease of the MFIS with increasing stress loading and a stiffening of the alloy with increasing dc fields. The latter behavior is phenomenologically similar to the ΔE effect in magnetostrictive materials. The large reversible MFIS and tunable stiffness properties exhibited by this alloy could enable practical Ni–Mn–Ga actuators for high-deflection, low-force applications which due to being driven by a solenoid transducer are more compact, energy efficient, and faster than their electromagnet counterpart. A thermodynamic model is presented which qualitatively characterizes the decay in MFIS with increasing compressive external load and provides a starting point for the characterization, design, and control of the proposed Ni–Mn–Ga devices. [ABSTRACT FROM AUTHOR]
We report the effect of progressive reduction of the annealing temperature on the magnetocaloric effect (MCE) of La[sub 2/3]Ca[sub 1/3]MnO[sub 3-δ] nanoparticles synthesized by the sol-gel technique. With this method, we are able to obtain particle diameters ranging form 60 to 500 nm. The peak in the MCE at the ferromagnetic to paramagnetic phase transition is strongly reduced as annealing temperature does, due to loss of the intrinsic first-order magnetic phase transition. This opens up a new way in which to tune the intrinsic properties of mixed-valence manganites, most of which are associated with the first-order character of the magnetic transition. [ABSTRACT FROM AUTHOR]
Organic materials with extraordinary magnetic properties promise a wide range of light, flexible, and inexpensive alternatives to familiar metal-based magnets. Individual organic molecules with high magnetic moments will be the foundation for design and fabrication of these materials.This book provides a systematic understanding of the structure and properties of organic magnetic molecules. After a summary of the phenomenon of magnetism at the molecular level, it presents a survey of the challenges to theoretical description and evaluation of the magnetic character of open-shell molecules, and an overview of recently developed methods and their successes and shortfalls. Several fields of application, including very strong organic molecular magnets and photo-magnetic switches, are surveyed. Finally, discussions on metal-based materials and simultaneously semiconducting and ferromagnetic extended systems and solids point the way toward future advances.The reader will find a comprehensive discourse on current understanding of magnetic molecules, a thorough survey of computational methods of characterizing known and imagined molecules, simple rules for design of larger magnetic systems, and a guide to opportunities for progress toward organic magnets.
A new approach for synthesis of copper(II) complexes with 1-methyltetrazole based on oxidative dissolution of metallic powdercopper in ethanol – HCl (ammonium thiocyanate) was developed. Composition and structure of the complexes prepared were studied by elemental analysis, X-ray diffraction and infrared spectroscopy in the middle (4000–400 cm–1) and long wave (400–50 cm–1) field. In all complexes ligand shows monodentate coordination. Polymeric structure of complexes studied is formed due to bridging coordination of anions. Magnetochemical studies revealed that copper(II) chloride complexes a low-temperature ferromagnetic.