ESR study of some Cu(II)-4-substituted-2-Thiazolylhydrazone complexes

The Cu(II) complexes with 2-N-acetyl-salicylidene-hydrazino-4-chlor-methyl thiazole (L.) and 2-N-acetyl salicylidene-hydrazioo-4-thiazolyl acetic ester (L_II) were prepared and investigated by ESR measurements. The powder ESR spectrum at room temperature of CuL_IICl is quasi-isotropic (g=2.113), while for CuL_IICl is characteristic of monomeric species with axial symmetry (g _II)=2.234,g ₁=2.073). The isotropic ESR spectra of the CuLCl compounds in DMSO solution suggest the presence of pseudo-tetrahedral monomeric species. The anisotropic spectra were obtained for adsorbed CuLCl DMSO solutions on NaY zeolite. The parallel hyperfine structure shows the coexistence of two magnetic nonequivalent monomeric species. The estimation of some LCAO-MO coefficients using Kivelson and Neiman’s approximation reveals a dominant ionic character for copper-ligand bonds.     

Magnetocaloric and magnetoresistance properties of La2/3Sr1/3Mn1−xCoxO3 compounds

Structural, magnetic, magnetoresistance and magnetocaloric studies on La_2/3Sr_1/3Mn_1−xCo_xO₃ compounds were reported. The samples were prepared by the conventional ceramic method. X-ray analysis showed the presence of one phase only, in all studied samples. From electrical resistance measurements it was found that the samples show large negative magnetoresistance behavior. The magnetic measurements were performed in a large temperature range, 4.2–750 K and external magnetic fields up to 5 T. The adiabatic magnetic entropy changes, |ΔS|, were determined from magnetization data. Large magnetocaloric effect (MCE) has been obtained in all studied samples.     

Magnetic properties and magnetocaloric effects in ferrimagnetic compounds

Magnetic properties and magnetocaloric effects were studied in (Gd_xY_1?x)₃Co₁₁B₄ ferrimagnetic compounds. Rather high values of the entropy changes were shown in large temperature ranges. The ΔS values were correlated with high temperature dependences of resultant magnetizations determined mainly by the gadolinium sublattice one. Large relative cooling power was also shown.     

SERS assessment of the cancer-specific methylation pattern of genomic DNA: towards the detection of acute myeloid leukemia in patients undergoing hematopoietic stem cell transplantation

In this label-free surface-enhanced Raman scattering (SERS) study of genomic DNA, we demonstrate that the cancer-specific DNA methylation pattern translates into specific spectral differences. Thus, DNA extracted from an acute myeloid leukemia (AML) cell line presented a decreased intensity of the 1005 cm⁻¹ band of 5-methylcytosine compared to normal DNA, in line with the well-described hypomethylation of cancer DNA. The unique methylation pattern of cancer DNA also influences the DNA adsorption geometry, resulting in higher adenine SERS intensities for cancer DNA. The possibility of detecting cancer DNA based on its SERS spectrum was validated on peripheral blood genomic DNA samples from n = 17 AML patients and n = 17 control samples, yielding an overall classification of 82% based on the 1005 cm⁻¹ band of 5-methylcytosine. By demonstrating the potential of SERS in assessing the methylation status in the case of real-life DNA samples, the study paves the way for novel methods of diagnosing cancer.

Graphical abstract

     

μSR Investigation of magnetic phases in R1−xSrxCoO3 oxides (R=Pr, Nd)

We report results of our muon spin relaxation measurements in the series of polycrystalline compounds Pr_1−xSr_xCoO₃ (x=0.3, 0.4 and 0.5) and Nd_1−xSr_xCoO₃ (x=0.3 and 0.5). For the Pr-based samples our data clearly indicate the existence of two magnetic transitions, as also inferred from macroscopic measurements. While the high temperature transition is typical for cobaltites (∼200 K), the low temperature one is unusual. In our experiments it occurs below about 120 K and it manifests itself as a change in the slope of the temperature variation of the muon spin depolarization rate λ(T). For the Nd-based samples we found an increase of the muon spin depolarization rate below 45 K, temperature at which the sample is ferrimagnetic, when the Nd sublattice coupled antiparallel to the Co lattice. No phase separation could be evidenced in our samples by μSR experiments.     

ESR study of some Cu(II)-oxazepam complexes

The CuL₂X₂ (L = 7-chlor-l,3-dihydro-3-hydroxi-5-phenyl-2H-l,4-benzodiazepin-2-one, also known as oxazepam, X = Cl, Br) complexes were prepared and investigated by ESR (electron spin resonance) method. Powder ESR spectra of CuL₂X₂ compounds at room temperature show the presence of monomeric species having an axial symmetry with a small rhombic distortion. In case of compounds with Cl there is a superposition of two nonequivalent mononuclear species, one with ad_{x² - y²} d_{x^2 - y^2 } ground state and another with ad_z² d_{z^2 } ground state. In pyridine (Py) and dimethylformamide (DMF) solutions the monomeric species prevail. Two different monomeric species, one with pseudotetrahedral (T_d) and the other with elongated tetrahedral-octahedral symmetry, were evidenced in DMF solutions adsorbed on NaY zeolite. In Py-DMF solutions two monomeric species were also identified. Dimeric species appear in DMF and Py solutions adsorbed on NaY zeolite through the coordination of two Cu(II) ions at the same keto-oxygen from one oxazepam molecule.     

The effect of lanthanide impurities on the physical properties of half-metallic ferromagnet Co2MnSi

The paper reports some preliminary results on possible incorporation of Ho in Co₂MnSi lattice. In addition, the effect of holmium substitution on Mn sites is analyzed on the basis of self-consistent electronic structure calculations.     

Low-temperature magnetic ordering in the perovskites Pr1−xAxCoO3 (A=Ca,Sr)

The magnetic and electrical properties of polycrystalline Pr_1?xA_xCoO₃ cobaltites with A=Ca, Sr and 0≤x≤0.5 were studied in the temperature range 4 K≤T≤1000 K and field up to 7 T. The X-ray analyses show the presence of only one phase having monoclinic or orthorhombic symmetry. The magnetic measurements indicate that the Ca-doped samples have at low temperatures, similar properties to the frustrated magnetic materials. PrCoO₃ is a paramagnetic insulator in the range from 4 to 1000 K. The Sr-doped cobaltites exhibit two phase transitions: a paramagnetic–ferromagnetic (or magnetic phase separated state) phase transition at about 240 K and a second one at about 100 K. The magnetic measurements suggest the presence of magnetic clusters and a change in the nature of magnetic coupling between Co ions at low temperatures. A semiconducting type behavior and high negative magnetoresistance was found for the Ca-doped samples, while the Sr-doped ones were metallic and with negligible magnetoresistance. The results are analyzed in the frame of a phase separation scenario in the presence of the spin-state transitions of Co ions.