Y. Elerman

Conformational study and structure of N-(2,5-methylphenyl)salicylaldimine

Abstract N-(2,5-methylphenyl)salicylaldimine (C15H15NO) has been investigated by X-ray analysis and AM1 semi-empirical quantum mechanical method. The crystal is in the orthorhombic space group P212121 with a = 6.839(1), b = 7.720(4), c = 23.183(3) A , V = 1224.1(2) A 3 , Z = 4, Dc = 1.222 g cm−3 and μ(Mo Kα) = 0.076 mm−1. The title structure was solved by direct methods and refined to R = 0.0364 for 1489 reflections [I > 2σ(I)] by full-matrix anisotropic least-squares methods. The title compound is photochromic and the molecule is not planar. There is a strong intramolecular hydrogen bond of distance 2.604(2) A between the hydroxyl oxygen atom and imine nitrogen atom, the hydrogen atom essentially being bonded to the oxygen atom. Minimum energy conformations from AM1 were calculated as a function of three torsion angles, θ1 (C8N1C7C6), θ2 (C9C8N1C7) and θ3 (N1C7C6C5), varied every 10°. The optimized geometry of the crystal structure corresponding to non-planar conformation is the most stable conformation in all calculations. The results strongly indicate that the minimum energy conformation is primarily determined by non-bonded hydrogen-hydrogen repulsions.

Structure and conformation of N-(2-methyl-5-chlorophenyl)salicylaldimine

Abstract N-(2-methyl-5-chlorophenyl)salicylaldimine (C14H12ClNO) has been studied by X-ray analysis and AM1 molecular orbital methods. It crystallises in the orthorhombic space group P212121 with a = 7.474(1) A , b = 12.155(1) A , c = 13.378(1) A , V = 1215.3(2) A 3 , Z = 4, Dc = 1.343 g cm−3 and μ(Mo Kα) = 0.296 mm−1. The structure was solved by direct methods and refined to R = 0.0374 for 1689 reflections [I > 2σ(I)]. The title compound is photochromic and the molecule is not planar. There is a strong intramolecular hydrogen bond of distance 2.604(3) A between the hydroxyl oxygen atom and imine nitrogen atom, the hydrogen atom essentially being bonded to the oxygen atom. Minimum energy conformations from AM1 were calculated as a function of the three torsion angles θ1(C8N1C7C6), θ2(C9C8N1C7) and θ3(N1C7C6C5), varied every 10°. The optimised geometry of the crystal structure corresponding to a non-planar conformation is the most stable conformation in all calculations.

Gold-Coated Iron Composite Nanospheres Targeted the Detection of Escherichia coli

We report the preparation and characterization of spherical core-shell structured Fe3O4–Au magnetic nanoparticles, modified with two component self-assembled monolayers (SAMs) consisting of 3–mercaptophenylboronic acid (3–MBA) and 1–decanethiol (1–DT). The rapid and room temperature synthesis of magnetic nanoparticles was achieved using the hydroxylamine reduction of HAuCl4 on the surface of ethylenediaminetetraacetic acid (EDTA)-immobilized iron (magnetite Fe3O4) nanoparticles in the presence of an aqueous solution of hexadecyltrimetylammonium bromide (CTAB) as a dispersant. The reduction of gold on the surface of Fe3O4 nanoparticles exhibits a uniform, highly stable, and narrow particle size distribution of Fe3O4–Au nanoparticles with an average diameter of 9 ± 2 nm. The saturation magnetization value for the resulting nanoparticles was found to be 15 emu/g at 298 K. Subsequent surface modification with SAMs against glucoside moieties on the surface of bacteria provided effective magnetic separation. Comparison of the bacteria capturing efficiency, by means of different molecular recognition agents 3–MBA, 1–DT and the mixed monolayer of 3–MBA and 1–DT was presented. The best capturing efficiency of E. coli was achieved with the mixed monolayer of 3–MBA and 1–DT-modified nanoparticles. Molecular specificity and selectivity were also demonstrated by comparing the surface-enhanced Raman scattering (SERS) spectrum of E. coli-nanoparticle conjugates with bacterial growth media.

Inverse magnetocaloric effect of epitaxial Ni-Mn-Sn thin films

Epitaxial Ni-Mn-Sn thin films of 200 nm thickness were prepared by magnetron sputtering and deposited onto MgO(100) substrate. They reveal an inverse magnetocaloric effect with a martensitic phase transition around 260 K. The resulting magnetocaloric properties of these films have been determined performing magnetization measurements in the temperature range between 10 and 330 K applying different magnetic fields. The maximum values of entropy change and relative cooling power are 1.6 J kg−1 K−1 and 36.5 J kg−1 for cooling and 1.5 J kg−1 K−1 and 33.9 J kg−1 for heating in μ0ΔH=1 T, respectively. These data are comparable with bulk values of Ni-Mn-Sn Heusler alloys.

Magnetic properties of PrMn2-xFexGe2 compounds

Abstract The structure and magnetic properties of the PrMn 2− x Fe x Ge 2 (0.0≤ x ≤1.0) compounds have been investigated by means of X-ray diffraction and magnetic measurements. All compounds crystallize in the ThCr 2 Si 2 -type structure with the space group I 4/ mmm . The lattice constants and the unit cell volume obey Vegard’s law. The samples with x ≤0.4 are ferromagnetic and show an additional increase in the magnetization due to magnetic ordering of the Pr sublattice at low temperatures. Reentrant ferromagnetism has been observed for x =0.6. The compounds with x =0.8 and x =1.0 are antiferromagnetic. The results lead to the construction of the partial x −T magnetic phase diagram.

Magnetic properties of Nd1−xGdxMn2Ge2 compounds

Abstract The magnetic properties of polycrystalline Nd 1− x Gd x Mn 2 Ge 2 (0≤ x ≤1) compounds have been investigated by means of X-ray diffraction and measurements of the DC magnetization. All compounds crystallize in the ThCr 2 Si 2 -type structure with the space group I 4/ mmm . Lattice parameters and the unit cell volume obey Vegard’s law. The samples with x ≤0.6 are ferromagnetic and have spin reorientation temperature. In the case of 0.7≤ x x =0.8 and x =0.85. As a result, the magnetic phase diagram has been constructed.

Magneto-structural characterization of tetranuclear copper(II) complex [Cu4(pz)4L2]·(ClO4) (LH=1,3-diamino-2-propanol, Hpz=pyrazole)

Abstract The title compound C18H30ClCu4N12O6 has been synthesized and its crystal structure and magnetic properties determined. The compound contains a tetranuclear copper(II) complex in which two dimeric units are bridged by two pyrazolate ligands and a perchlorate anion which is bound to the tetrameric unit by hydrogen bonds in the asymmetric unit. In each dimeric moiety the two copper(II) ions are bridged by the alkoxo group of the ligand and an additional pyrazolate ligand, these dimers are then bridged by two pyrazolate ions to form the tetranuclear complex. Magnetic susceptibilities for the compound in the solid state are measured over the temperature range 4.5–306.8 K. The experimental magnetic susceptibilities were fitted to the Bleaney–Bowers equation for a spin-coupled S=1/2 system in which the singlet–triplet separation is 2J. The title compound shows weak antiferromagnetic coupling with a best fit J value −98.5 cm−1. The alkoxo oxygen bridge is one of the principal pathways for the super-exchange interaction and the weak antiferromagnetic coupling of the complex is interpreted in terms of the countercomplementary effect of the different bridging ligands which participate in the super-exchange interactions. The ab initio restricted Hartree–Fock molecular orbital calculation has shown that the pyrazolate bridge contributes to magnetic interaction countercomplementarily to the alkoxide bridge.

Giant magnetocaloric effect in the Gd 5 Ge 2.025 Si 1.925 In 0.05 compound

The magnetocaloric properties of the Gd5Ge2.025Si1.925In0.05 compound have been studied by x-ray diffraction, magnetic and heat capacity measurements. Powder x-ray diffraction measurement shows that the compound has a dominant phase of monoclinic Gd5Ge2Si2-type structure and a small quantity of Gd5(Ge,Si)3-type phase at room temperature. At about 270 K, this compound shows a first order phase transition. The isothermal magnetic entropy change (ΔSM) is calculated from the temperature and magnetic field dependences of the magnetization and the temperature dependence of MCE in terms of adiabatic temperature change (ΔTad) is calculated from the isothermal magnetic entropy change and the temperature variation in zero-field heat-capacity data. The maximum ΔSM is −13.6 Jkg−1K−1 and maximum ΔTad is 13 K for the magnetic field change of 0–5 T. The Debye temperature (θD) of this compound is 149 K and the value of DOS at the Fermi level is 1.6 states/eVatom from the low temperature zero-field heat-capacity data. A considerable isothermal magnetic entropy change and adiabatic temperature change under a field change of 0–5 T jointly make the Gd5Ge2.025Si1.925In0.05 compound an attractive candidate for a magnetic refrigerant.

N-(2-Hydroxyphenyl)salicylaldimine

The title compound, 2-(salicylideneamino)phenol, C 13 -H 11 NO 2 , a potential tridentate ligand, has two crystallographically independent molecules in the asymmetric unit, one of which is disordered. Intramolecular hydrogen bonds occur between the pairs of atoms 0(16) and N(8) [2.625 (7) A], and O(1) and 0(16) [3.571(7) A], the H atoms essentially being bonded to the O atoms.

Investigation of the crystal structure and magnetic properties of Nd1-xGdxMn2Si2 compounds

constants and the unit cell volume. In the x(T ) curves above room temperature, all samples show a clear peak coinciding with the Neel temperature due to antiferromagnetic coupling of the ferromagnetic Mn layers. At low temperatures below about 60 K, the rare earth sublattice orders and also the antiferromagnetic coupling of the ferromagnetic Mn layers becomes ferromagnetic. The samples with x50.2 and 0.6 exhibit a spin reorientation phenomenon. In terms of the mean field two-sublattice model, the values of the intrasublattice coupling constant n and the intersublattice coupling constant n for the antiferromagnetic phase have been derived from the 11 12 temperature dependence of the magnetic susceptibility.