A hydrogen-bonded,one-dimensional complex of cadmium(II) ions with 3,5-dinitrobenzoate and radicals: synthesis,characterization and crystal structure

A novel one-dimensional complex, [Cd(NIT4py)₂(DTB)₂(H₂O)₂] (1), (where NIT4py is 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and DTB is 3,5-dinitrobenzoate) has been synthesized and characterized by elemental analyses, IR and electronic spectra, single-crystal X-ray diffraction and magnetic measurements. The Cd(II) ion lies in a distorted octahedral environment with two nitrogen atoms from two NIT4py ligands and two oxygen atoms from two DTB molecules in the basal plane, and two oxygen atoms from two water molecules in axial positions. [Cd(NIT4py)₂(DTB)₂(H₂O)₂] units are connected to form one-dimensional chains by intermolecular hydrogen bonds. The complex exhibits intramolecular antiferromagnetic interactions.     

Four inorganic–organic hybrid complexes built from tetravanadate and macrocyclic oxamide

Four inorganic–organic hybrid compounds, [M₂(CuL)₄(V₄O₁₂)]·2H₂O (M?=?Co (1), Mn (2)), [Mn₂(NiL)₄(V₄O₁₂)]·2H₂O (3), and [Zn₂(CuL)₄(V₄O₁₂)]·2CH₃OH·2H₂O (4) (M′L, H₂L?=?2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien), have been synthesized and characterized by elemental analysis, IR, UV, fluorescence spectra, and X-ray diffraction analysis. Single-crystal X-ray analysis reveal that both [V₄O₁₂]^4? and M₂V₄ adapt a chair-like configuration in four structures. The cyclovanadate group [V₄O₁₂]^4? is a tetradentate bridging ligand linking two [M(M′L)₂]²⁺ fragments, producing centroantisymmetric heterometallic hexanuclear [M₂M′₄] complexes. The variable-temperature magnetic susceptibility measurements (2–300?K) of 1 and 2 show weak antiferromagnetic interactions.     

Novel Mixed-Valence μ-Oxo-Bridged Trinuclear Manganese Complexes [Mn3O(O2CR)6L3] (R=4-Cl-C6H4OCH2, 3-Cl-C6H5, BrCH2, L=3-Methylpyridine or Water): Structures and Magnetic Properties

Preparation of three new mixed-valence oxo-centered trinuclear manganese complexes [Mn₃O(O₂CR)₆L₃] (R=4-Cl-C₆H₄OCH₂, 1, 3-Cl-C₆H₅, 2, BrCH₂, 3; L=3-methylpyridine or water), by reaction of N-n-Bu₄MnO₄ with appropriate reagents in ethanol and 3-methelpyridine is reported. The crystal structure of 1 has shown to have an oxo-centered Mn₃O unit with peripheral ligands provided by bridging carboxylate and terminal 3-methylpyridine groups, and with an approximate 3-fold symmetry axis for the whole cluster. Variable temperature magnetic susceptibilities of the complexes in the range 1.5-300 K have been measured and are interpreted in terms of the Kambe vector-coupling method and Van Vleck equation; J (cm^?1), J' (cm^?1), g, and R parameters obtained are -8.2, -10.9, 2.04, 2.15 x 10^?3 (1); -7.3, -11.1, 2.20, 3.32 x 10^?3 (2); -2.1, -4.1, 1.97, 2.34 x 10^?3 (3). There is weak antiferromagnetic exchange between manganese ions. Effects of bridging and terminal ligands on the J, J' values and spin ground state are discussed.     

3D Heterometallic 3d–4f coordination polymers based on organodisulfonate ligand with isonicotinic acid as a co-ligand: synthesis,crystal structures,photoluminescent and magnetic properties

The hydrothermal reaction of rare earth nitrates, CuCN, 2,7-naphthalenedisulfonate (2,7-nds), and isonicotinic acid (Hina) affords a new family of 3-D heterometallic 3d–4f coordination polymers, [Ln₂Cu(2,7-nds)₂(ina)₄(H₂O)₄]·4H₂O (Ln = Nd (1), Sm (2), Eu (3), Gd (4); 2,7-nds = 2,7-naphthalenedisulfonate, Hina = isonicotinic acid). Complexes 1–4 are structurally characterized by single crystal X-ray diffraction, elemental analysis, FT-IR spectroscopy (IR), powder X-ray diffraction, and thermogravimetric analyses. X-ray crystal structure analyses reveal that 1–4 are isomorphous with dinuclear subunit [Sm₂(ina)₄] binding Cu ions to generate 2-D networks. Such 2-D networks are pillared by linking 2,7-nds ligands to result in the 3-D layer-pillared Ln(III)–Cu(II) coordination architectures. The valence of Cu salts changed in the reaction. In addition, the luminescence properties of 1–3 and the magnetic properties of 3 and 4 have also been investigated.     

Synthesis,crystal structure and magnetic properties of new MnIII–CuII heterometallic aggregates based on multidentate Schiff-base ligands

Reaction of copper powder, manganese(II) nitrates and multidentate Schiff-base ligands in hot methanol solution led to the isolation of two new Mn^III–Cu^II heterometallic aggregates, [Mn₂ ^IIICu₂ ^II(H₂L)₄] · (NO₃)₂ · 2CH₃OH (1) (H₄L=2-[(2-hydroxy-benzylidene)-amino]-2-hydroxymethyl-proane-1,3-diol) and [Mn^IIICu^II ₃(sae)₄(MeOH)(H₂O)₃] · NO₃ · MeOH (2) (H₂sae = salicylidene-2-ethanolamine). Both compounds were characterized by elemental analysis, IR, XPS, EPR, XRPD and single crystal X-ray diffraction. Compound 1 crystallizes in the triclinic space group P 1 with a = 11.1268(4) Å, b = 11.6153(4) Å, c = 11.8129(5) Å, α = 88.435(10)°, β = 80.203(10)°, γ = 77.572(10)°, V = 1469.13(10) ų, Z = 1, R1(wR2) =0.0300(0.0771). Compound 2 crystallizes in the monoclinic space group P2₁/n with a = 18.1715(7), b = 12.9931(5), c = 19.5903(8) Å, β = 97.1980(10)°, V = 4588.9(3) ų, Z = 4, R1(wR2) = 0.0667 (0.1998). The magnetic susceptibilities of 1 and 2 display the antiferromagnetic interactions in both compounds.     

Dzyaloshinskii-Moriya interactions in systems with fabrication induced strain gradients: An ab-initio study

The Dzyaloshinskii-Moriya (DM) vectors arising from a fabrication induced perpendicular strain gradient in a film of bcc Fe are calculated by a combination of the ab initio density functional electron theory with a micromagnetic model. It is shown that even for large strain gradients the absolute values of the DM vectors are 1-2 orders of magnitude smaller than those calculated recently for a Fe bilayer on W(1 1 0). The breaking of the symmetry of the static and dynamic properties of a magnetic vortex with respect to its polarization is discussed for systems with DM interactions.     

First Principles Study on FeAs Single Layers

在广义梯度近似(GGA)和GGA+U的框架下,用第一性原理方法研究了用FeAs单层的简单模型来研究LaFeAsO和BaFe2As2的合理性. 对未掺杂的FeAs单层,优化的几何结构及其对应的电子结构与本体的性质差异较大,并且在单层中没有发现体相中的共线反铁磁基态. 另外,在单层中,As与Fe层之间在z方向的间距随电子和空穴掺杂浓度的变化也与实验结果不符,这些结果表明,在LaFeAsO和BaFe2As2中,FeAs层与其他层之间的相互作用是不可忽略的,用简单的FeAs单层来处理Fe基超导体需要考虑更多的修正     

Microstructure-controlled enhancement of magnetoimpedance in nanocrystalline FeSiNbBCu alloys

Rapidly solidified amorphous Fe_68.5Si_18.5Nb₃B₉Cu₁ ribbon has been subjected to heat treatment at a temperature of 550 °C for different time periods. All the annealed ribbons show the precipitation of nanocrystalline Fe₃Si phase from the amorphous phase. The estimated crystallite size from X-ray diffraction peak analysis was in the range of 15-25 nm. While the surface studies confirm the presence of a distribution of spherical nanostructures in amorphous matrix. Both magnetoimpedance and longitudinal permeability ratios are found to increase with annealing time, and attain a maximum value for 60 min annealed ribbon and decrease on further increase in the annealing time. The enhanced magnetic properties and magnetoimpedance on suitable heat treatment is attributed to the change of magnetic parameters such as anisotropy and magnetostriction, due to change in microstructure. Analysis of permeability and impedance data taken under similar conditions suggests a strong correlation between them.     

Electronic structure, magnetism and superconductivity of layered iron compounds

The layered iron superconductors are discussed using electronic structure calculations. The four families of compounds discovered so far, including Fe (Se, Te) have closely related electronic structures. The Fermi surface consists of disconnected hole and electron cylinders and additional hole sections that depend on the specific material. This places the materials in proximity to itinerant magnetism, both due to the high density of states and due to nesting. Comparison of density functional results and experiment provides strong evidence for itinerant spin fluctuations, which are discussed in relation to superconductivity. It is proposed that the intermediate phase between the structural transition and the SDW transition in the oxy-pnictides is a nematic phase.     

Metastable magnetic configurations of (V, Cr, Mn and Fe) on Ir(0 0 1) surfaces

We present a theoretical study of the electronic and magnetic structure of the 3d-transition metals (M = V, Cr, Mn and Fe) in several overlayer systems. The electronic as well as magnetic structures are investigated for pseudomorphic overlayers (M/Ir(0 0 1)), ordered alloyed overlayers of the type M_0.5Ir_0.5/Ir(0 0 1) and ordered binary surface alloys of V, Cr, Mn and Fe transition metals on Ir(0 0 1) substrates. The calculations are performed with a self-consistent tight-binding method using the unrestricted Hartree-Fock approximation within the Hubbard model. We obtained metastable c(2 × 2) configurations for V, Cr and Mn and a p(1 × 1) configuration for Fe pseudomorphic overlayers. However, ferrimagnetic configuration has been obtained for the ordered surface alloys M_0.5Ir_0.5 and the binary alloyed overlayers on Ir(0 0 1) surfaces.