Magnetochemistry

Two carboxylate-bridged one-dimensional chain complexes, {[Mn^II(MeOH)₂][Fe^III(L)₂]₂}_n (1) and {[Mn^II(DMF)₂][Mn^III(L)₂]₂·DMF}_n (2) [H₂L = ((2-carboxyphenyl)azo)-benzaldoxime], containing a low-spin [Fe^III(L)₂]⁻ or [Mn^III(L)₂]⁻ unit were synthesized. Magnetic measurements show that the adjacent high-spin Mn^II and low-spin M^III ions display weak antiferromagnetic coupling via the syn–anti carboxyl bridges, with J = −0.066(2) cm⁻¹ for complex 1 and J = −0.274(2) cm⁻¹ for complex 2. Full article

Magnetic fluids based on single-domain magnetic spinel ferrite nanoparticles dispersed in various liquid media are of particular practical and scientific interest. This paper presents a muon spectroscopy study of a ferrofluid based on magnetic nanoparticles of CoFe₂O₄ molecules dispersed in water (H₂O) with a nanoparticle concentration of 3%. In this study, it was determined that the structure and magnitude of the magnetization of a ferrofluid depend on the viscosity of the liquid itself. It was shown that, at room temperature (290 K) and under an external magnetic field of 527 G, the observed additional magnetization was ~20 G. In a small fraction of the sample under study (~20%), negative magnetization (diamagnetism) was observed. At low temperatures (~30 K), the sample acted as a paramagnet in a magnetic field. For the first time, the magnetic field inside and in the immediate vicinity of a CoFe₂O₄ nanoparticle has been measured experimentally using the μSR method: the value was 1.96 ± 0.44 kG; thus, direct measurement of the magnetization of a nanoscale object was performed. Full article

Peter Day was one of the most asiduous participants of the NoSIC (Not Strictly Inorganic Chemistry) meetings, where he showed his interest in, and knowledge of, historical, sociological and other non-scientific aspects of the research activities in the institutions led by him as well as in those he visited worldwide, both as a lecturer and as an active participant. This article tries to stress that side of his personality, reflected also in his three autobiographical books, and in his motto “the past is another country”, a quotation from L.P. Hartley. Full article

Efficient shielding materials are extremely important to minimize the effect of electromagnetic interference. Currently, various composite materials are being investigated with different shielding efficiencies reported. In this paper, a flexible and free-standing sodium-based chitosan (CH/Na) polymer with copper selenide (CuSe) filler was prepared for electromagnetic shielding. The CH/Na/CuSe polymer matrix was prepared via the direct casting technique at different wt% of CuSe, varying from 2 to 20 wt%. The polymer matrix was then characterised by using Fourier transform infrared (FTIR) spectroscopy to confirm the interaction between the CH/Na and CuSe. The XRD results revealed that the CH/Na/CuSe polymer was successfully formed. Improvement in the electrical conductivity was confirmed by an impedance spectroscopy measurement. The highest electrical conduction recorded was at 3.69 × 10⁻⁵ S/cm for CH/Na/CuSe polymer matrix with 20 wt% CuSe. An increase in total electromagnetic interference (EMI) shielding efficiency (SE_T) of up to 20 dB (99% EM power shield) was achieved, and it can be increased up to 34 dB (99.9% EM power shield) with the thickness of the polymer increased. Full article

A comparative study of the unreacted and reacted uniaxially strained Pt(111) and the layered (111)-Pt/Ni/Pt₃Ni and (111)-Pt/Ni/PtNi₃ surfaces has been performed using density functional theory (DFT). An in-depth study of the unreacted surfaces has been performed to evaluate the importance of geometric, magnetic and ligand effects in determining the reactivity of these different Pt surfaces. An analysis of the binding energies of oxygen and hydrogen over the high-symmetry binding positions of all surfaces has been performed. The study has shown that O and H tend to bind more strongly to the (111)-Pt/Ni/Pt₃Ni surface and less strongly to the (111)-Pt/Ni/PtNi₃ surface compared to binding on the equivalently strained Pt(111) surfaces. Changes in the surface magnetisation of the surfaces overlaying the ferromagnetic alloys during adsorption are discussed, as well as the behaviour of the d-band centre across all surfaces, to evaluate the potential mechanisms for these differences in binding. An accompanying comparison of the accessible density functionals has been included to estimate the error in the computational binding energies. Full article

Magnetophoresis offers many advantages for manipulating magnetic targets in microsystems. The integration of micro-flux concentrators and micro-magnets allows achieving large field gradients and therefore large reachable magnetic forces. However, the associated fabrication techniques are often complex and costly, and besides, they put specific constraints on the geometries. Magnetic composite polymers provide a promising alternative in terms of simplicity and fabrication costs, and they open new perspectives for the microstructuring, design, and integration of magnetic functions. In this review, we propose a state of the art of research works implementing magnetic polymers to trap or sort magnetic micro-beads or magnetically labeled cells in microfluidic devices. Full article

The collective magnetic behavior of photoswitchable 11 nm cyanide-bridged nanoparticles based of the Prussian blue analogue CsCoFe were investigated when embedded in two different matrices with different concentrations. The effect of the intensity of light irradiation was studied in the less concentrated sample. Magnetization studies and alternating magnetic susceptibility data are consistent with a collective magnetic behavior due to interparticle dipolar magnetic interaction for the two compounds, even though the objects have a size that place them in the superparamagnetic regime. Full article

Stability of the DNA molecule is essential for the proper functioning and sustainability of all living organisms. In this study, we investigate the effect of gamma radiation (γ-radiation) on spin-selective electron transfer through double strand (ds)DNA molecules. Self-assembled monolayers (SAMs) of 21-base long DNA are prepared on Au-coated Ni thin film. We measure the spin polarization (%) of the SAMs of ds-DNA using the spin-dependent electrochemical technique. We use a Cs-based γ-radiation source to expose the SAMs of ds-DNA immobilized on thin films for various time intervals ranging from 0–30 min. The susceptibility of DNA to γ-radiation is measured by spin-dependent electrochemistry. We observe that the efficiency of spin filtering by ds-DNA gradually decreases when exposure (to γ-radiation) time increases, and drops below 1% after 30 min of exposure. The change in spin polarization value is related either to the conformational perturbation in DNA or to structural damage in DNA molecules caused by ionizing radiation. Full article

Three new ionic salts containing [M(CN)₈]⁴⁻ (M = Mo^IV and W^IV) were prepared using large complex cations based on a non-conventional motif built with the tris(2-aminoethyl)amine (noted hereafter tren) ligand, [{M’(tren)}₃(μ-tren)]⁶⁺ (M’ = Cu^II and Zn^II). The crystal structures of the three compounds show that the atomic arrangement is formed by relatively isolated anionic and cationic entities. The three compounds were irradiated with a blue light at low temperature, and show a significant photomagnetic effect. The remarkable properties of these compounds are (i) the long-lived photomagnetic metastable states for the [Mo(CN)₈]⁴⁻-based compounds well above 200 K and (ii) the rare efficient photomagnetic properties of the [W(CN)₈]⁴⁻-based compound. These photomagnetic properties are compared with the singlet-triplet conversion recently reported for the K₄[Mo(CN)₈]·2H₂O compound. Full article

Nuclear Magnetic Resonance is particularly sensitive to the electronic structure of matter and is thus a powerful tool to characterize in-depth the magnetic properties of a system. NMR is indeed increasingly recognized as an ideal tool to add precious structural information for the development of Single Ion Magnets, small complexes that are recently gaining much popularity due to their quantum computing and spintronics applications. In this review, we recall the theoretical principles of paramagnetic NMR, with particular attention to lanthanoids, and we give an overview of the recent advances in this field. Full article

SSEA-4 antigen can be mainly found in embryos and embryonic stem cells. However, its expression has been observed also in adult stem and progenitor cells, or even in some differentiated cells. Moreover, we found a considerable number of SSEA-4 positive (SSEA-4⁺) cells within the rabbit peripheral blood and bone marrow mononuclear cells (PBMCs and BMMCs) in our previous study. Since no information about such cells can be found anywhere in the literature, the aim of this study was to identify their origin. At first, phenotypic analyses of fresh rabbit PBMCs and BMMCs were performed using flow cytometry and specific antibodies against SSEA-4 and leukocyte subsets. Then, SSEA-4⁺ were enriched using magnetic activated cell sorting (MACS) and analyzed for their phenotype using qPCR. We found significant SSEA-4⁺ cell population in PBMCs (~50%) and BMMCs (~20%). All those cells co-expressed CD45 and a majority of them also expressed B-cell marker (IgM; 50% of SSEA-4⁺ PBMCs and 60% of SSEA-4⁺ BMMCs). Increased (p < 0.05) expression of SSEA-4, CD45 and B-cell markers (IgM, CD79α and MHCII) were also noticed by qPCR in SSEA-4⁺ cells enriched via MACS (with efficiency over 80%). Both methods did not detect significant expression of monocyte or T-cell markers. In conclusion, SSEA-4⁺ cells in rabbit blood and bone marrow are of hematopoietic origin and probably belong to B-lineage cells as possessing the phenotype of B lymphocytes. However, the true function of SSEA-4 antigen in these cells should be explored by further studies. Full article

Here, we review the different series of (super)conducting and magnetic radical salts prepared with organic donors of the tetrathiafulvalene (TTF) family and oxalato-based metal complexes (ox = oxalate = C₂O₄²⁻). Although most of these radical salts have been prepared with the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF = ET), we also include all the salts prepared with other TTF-type donors such as tetrathiafulvalene (TTF), tetramethyl-tetrathiafulvalene (TM-TTF), bis(ethylenediseleno)tetrathiafulvalene (BEST), bis(ethylenedithio)tetraselenafulvalene (BETS) and 4,5-bis((2S)-2-hydroxypropylthio)-4′,5′-(ethylenedithio)tetrathiafulvalene (DMPET). Most of the oxalate-based complexes are monomers of the type [M^III(C₂O₄)₃]³⁻, [Ge(C₂O₄)₃]²⁻ or [Cu(C₂O₄)₂]²⁻, but we also include the reported salts with [Fe₂(C₂O₄)₅]⁴⁻ dimers, [M^II(H₂O)₂[M^III(C₂O₄)₃]₂]⁴⁻ trimers and homo- or heterometallic extended 2D layers such as [M^IIM^III(C₂O₄)₃]⁻ and [M^II₂(C₂O₄)₃]²⁻. We will present the different structural families and their magnetic properties (such as diamagnetism, paramagnetism, antiferromagnetism, ferromagnetism and even long-range magnetic ordering) that coexist with interesting electrical properties (such as semiconductivity, metallic conductivity and even superconductivity). We will focus on the electrical and magnetic properties of the so-called Day series formulated as β″-(BEDT-TTF)₄[A⁺M^III(C₂O₄)₃]·G, which represents the largest family of paramagnetic metals and superconductors reported to date, with more than fifty reported examples. Full article

Over the years, various techniques have been utilized to study the function and phenotype of antigen-binding B cells in the primary repertoire following immunization, infection, and development of autoimmunity. Due to the low frequency of antigen-reactive B cells (<0.05% of lymphocytes) in the periphery, preliminary enrichment of cells is necessary to achieve sufficient numbers for statistically sound characterization, especially when downstream analytic platform use, e.g., CyTOF, is low throughput. We previously described a method to detect and enrich antigen-reactive B cells from peripheral blood and tissues using biotinylated antigens in conjunction with magnetic nanoparticles, preparative to a downstream analysis by ELISPOT and flow cytometry. While mass cytometry (CyTOF) enables high dimensional immunophenotyping of over 40 unique parameters on a single-cell level, its low throughput compared to flow cytometry and requirement for removal of metal contaminants, such as nanoparticles, made it particularly unsuitable for studies of rare cells in a mixed population. Here we describe a novel CyTOF-compatible approach for multiplexed enrichment of antigen-reactive B cells, e.g., insulin and tetanus toxoid, using cleavable magnetic nanoparticles. This method allows improved monitoring of the phenotype and function of antigen-reactive B cells during the development of disease or after immunization while minimizing the amount of sample and run times needed. Full article

An organic anion, 2-bromoethanesulfonate (BrC₂H₄SO₃⁻), provides one bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and two bis(ethylenedithio)tetraselenafulvalene (BETS) salts, the compositions of which are β’’-β’’-(BEDT-TTF)₂BrC₂H₄SO₃ (1), β’’-β’’-(BETS)₂BrC₂H₄SO₃ (2), and θ-(BETS)₂BrC₂H₄SO₃ (3), respectively. Compound 1 shows a metal–insulator transition at around 70 K. Compound 2 is isomorphous to 1, and 3 is polymorphic with 2. Compounds 2 and 3 show metallic behavior at least down to 4.2 K. The pressure dependence of the electrical resistivity of 1 is also reported. Full article

Peter Day’s research group reported the first molecular superconductor containing paramagnetic metal ions in 1995, β″-(BEDT-TTF)₄(H₃O)Fe(C₂O₄)₃·C₆H₅CN. Subsequent research has produced a multitude of BEDT-TTF-tris(oxalato)metallate salts with a variety of structures and properties, including 32 superconductors to date. We present here the synthesis, crystal structure, and conducting properties of the newest additions to the Day series including the first superconductor incorporating the diamagnetic tris(oxalato)aluminate anion, β″-(BEDT-TTF)₄(H₃O)Al(C₂O₄)₃·C₆H₅Br, which has a superconducting T_c of ~2.5 K. β″-(BEDT-TTF)₄(H₃O)Co(C₂O₄)₃·C₆H₅Br represents the first example of a β″ phase for the tris(oxalato)cobaltate anion, but this salt does not show superconductivity. Full article

The behavior of spin for incoherently hopping carriers is critical to understand in a variety of systems such as organic semiconductors, amorphous semiconductors, and muon-implanted materials. This work specifically examined the spin relaxation of hopping spin/charge carriers through a cubic lattice in the presence of varying degrees of energy disorder when the carrier spin is treated classically and random spin rotations are suffered during the hopping process (to mimic spin–orbit coupling effects) instead of during the wait time period (which would be more appropriate for hyperfine coupling). The problem was studied under a variety of different assumptions regarding the hopping rates and the random local fields. In some cases, analytic solutions for the spin relaxation rate were obtained. In all the models, we found that exponentially distributed energy disorder led to a drastic reduction in spin polarization losses that fell nonexponentially. Full article

Methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF (1) and dimethyl-ethylenedithio-tetrathiafulvalene (DM-EDT-TTF (2) are valuable precursors for chiral molecular conductors, which are generally obtained by electrocrystallization in the presence of various counter-ions. The number of the stereogenic centers, their relative location on the molecule, the nature of the counter-ion and the electrocrystallization conditions play a paramount role in the crystal structures and conducting properties of the resulting materials. Here, we report the preparation and detailed structural characterization of the following series of radical cation salts: (i) mixed valence (1)₂AsF₆ as racemic, and (S) and (R) enantiomers; (ii) [(S)-1]AsF₆·C₄H₈O and [(R)-1]AsF₆·C₄H₈O where a strong dimerization of the donors is observed; (iii) (1)I₃ and (2)I₃ as racemic and enantiopure forms and (iv) [(meso)-2]PF₆ and [(meso)-2]XO₄ (X = Cl, Re), based on the new donor (meso)-2. In the latter, the two methyl substituents necessarily adopt axial and equatorial conformations, thus leading to a completely different packing of the donors when compared to the chiral form (S,S)/(R,R) of 2 in its radical cation salts. Single crystal resistivity measurements, complemented by thermoelectric power measurements in the case of (1)₂AsF₆, suggest quasi-metallic conductivity for the latter in the high temperature regime, with σ_RT ≈ 1–10 S cm^–1, while semiconducting behavior is observed for the (meso)-2 based salts. Full article