掺La3+纳米钴铁氧体的制备、表征、磁性及其Peg-20000复合物的导电性研究

纳米铁氧体材料的许多电磁性质和光学性质已经有了一些研究[1]。为了改善其性能,有研究者将稀土Ce3 掺入铁氧体材料进行改性,发现其磁导率有明显改变[2]。纳米CoFe2O4因为具有较高的矫顽力、适中的饱和磁化强度、适中的机械强度和化学性质稳定而作为硬磁材料[3]。有研究表明,在CoFe2O4体系中掺入过渡金属离子可以改变其磁性[4],加入稀土Yb3 ,La3 可以使晶格发生畸变,增强磁光效应[5]。因此,本工作研究CoFe2O4体系中掺入La3 引起磁性的变化。磁性纳米粒子掺杂到导电聚合物中可制备高性能吸波材料[6]。因为单一的铁氧体在吸波过程中虽无…     

Liquid crystalline heteronuclear complexes with a ferrocene-containing Schiffs base

A series of new heteronuclear complexes of a ferrocene-containing Schiffs base (LH) with Ni^II, Pd^II, V^IVO, and Fe^III as the central atoms has been obtained. PdL₂, VOL₂ FeL₂Cl, and [FeL₂]₂O complexes manifest liquid-crystalline properties and NiL₂ is nonmesomorphic. The structures of the complexes synthesized have been established by magnetic measurements and IR and ESR spectroscopy. All of them except PdL₂ are paramagnetic. The antiferromagnetic exchange interactions have been observed in the Fe^III complexes. The correlation of liquid-crystalline properties with the geometry of the chelate centers is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 941–945, May, 1994.     

Encapsulation of the ferritin protein in sol-gel derived silica glasses

A significant recent development in sol-gel science has been the encapsulation of biomolecules such as proteins and enzymes in optically transparent silica glasses. This paper reports on the encapsulation of an iron (Fe) storage protein, ferritin, to develop a magnetic silica glass. Native ferritin, which has a nanometer-sized microcrystalline Fe oxide core, was encapsulated in optically transparent silica glasses using the sol-gel process. Fe could be released from ferritin but could not be reconstituted into apoferritin when the protein was trapped in the pores of the glass. Transmission electron microscopy of ferritin-doped aged silica gels indicated that crystallinity of the Fe oxide core was retained upon sol-gel encapsulation. Magnetic measurements on ferritin-doped silica gels indicated the material to be paramagnetic, but not superparamagnetic.     

Strong Antiferromagnetic Exchange Interactions in Cobalt(II) Complexes with 2-Pyridyl Substituted Nitronyl Nitroxide Ligand

Three new complexes, [Co(hfac)₂(NIToPy)] (1), [CoCl₂(NIToPy)₂] (2), and [Co(NIToPy)₃](ClO₄)₂ (3), with NIToPy = 2-(2-Pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-oxy-3-oxide, and hfac = hexafluoroacetylacetonate, have been synthesized. The compound 3 crystallized in the monoclinic space group P2₁, with two molecules in a unit cell of dimensions a = 10.565(4) Å, b = 14.714(9) Å, c = 14.596(7) Å, and β = 107.10(4)°. The temperature-dependent magnetic susceptibility measurements (4.2 K-300 K) for the complexes demonstrated strong antiferromagnetic exchange interaction between cobalt(II) ion and NIToPy radical spins with J = ?140.1 cm^?1 for 1, J = ?94.2 cm^?1 for 2, and J = ?161.8 cm^?1 for 3, respectively. The magneto-structural correlation in these complexes has been discussed.     

Theoretical study of the magnetic exchange coupling behavior substituting Cr(III) with Mo(III) in cyano‐bridged transition metal complexes

Molecular magnetism in a series of cyano‐bridged first and second transition metal complexes has been investigated using density functional theory (DFT) combined with the broken‐symmetry (BS) approach. Several exchange‐correlation (XC) functionals in the ADF package were used to investigate complexes I [?(Me₃tacn)₂(cyclam)NiMo₂(CN)₆]²⁺, II [?(Me₃tacn)₂(cyclam)Ni‐Cr₂(CN)₆]²⁺, III [(Me₃tacn)₆MnMo₆(CN)₁₈]²⁺, and IV [(Me₃tacn)₆MnCr₆(CN)₁₈]²⁺ (Me₃tacn = N,N′,N?‐trimethyl‐1,4,7‐triazacyclononane). For models A (the molded structure of complex I) and B (the modeled structure of complex II), all the XCs given qualitatively reasonable results and predict ferromagnetic coupling character between M (M = Mo^III for A or Cr^III for B) and Ni^II in coincidence with the experimental results (see Tables I and II ). The calculated using Operdew, OPBE, O3LYP, and B3LYP functionals and experimental J values show that substituting Cr^III with Mo^III will enhance the ferromagnetic exchange coupling interactions. But VWN, PW91, PBE, VSXC, and tau‐HCTH functionals have no way to differentiate the relative strength of the intramolecular magnetic exchange coupling interactions of A and B correctly. For models C (the modeled structure of complex III) and D (the modeled structure of complex IV), all the XCs in ADF and B3LYP in Gaussian 03 with several basis sets show that substituting Cr^III with Mo^III will enhance the antiferromagnetic exchange coupling interactions. From the above calculations, the substitution of Cr^III by Mo^III will enhance the magnetic coupling interactions, whether the magnetic coupling interactions are ferro‐ or antiferromagnetic. Moreover, Kahn's model was applied to investigate the above facts. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Magnetic structure and properties of Cu3(OH)4SO4 made of triple chains of spins s=1/2

Cu₃(OH)₄SO₄, obtained by hydrothermal synthesis from copper sulfate and soda in aqueous medium, is isostructural with the corresponding antlerite mineral, orthorhombic, space group Pnma (62), with a=8.289(1) b=6.079(1) and c=12.057(1) Å, V=607.5(2) ų, Z=4. Its crystalline structure has been refined from X-ray single crystal and powder neutron diffraction data at room temperature. It consists of copper (II) triple chains, running in the b-axis direction and connected to each other by sulfate groups. The magnetic structure, solved from powder neutron diffraction data at 1.4 K below the transition at 5 K evidenced by susceptibility and specific measurements, reveals that, inside a triple chain, the magnetic moments of the copper ions (μ_B=0.88(5) at 1.4 K) belonging to outer chains are oriented along the c-axis of the nuclear cell, with ferromagnetic order inside a chain and antiferromagnetic order between the two outer chains. No long-range magnetic order is obtained along the central chain with an idle spin behavior.     

Synthesis,structure, and NO-donor activity of the paramagnetic complex [Fe<Subscript>2</Subscript>(SC<Subscript>3</Subscript>H<Subscript>5</Subscript>N<Subscript>2</Subscript>)<Subscript>2</Subscript>(NO)<Subscript>4</Subscript>] as a model of nitrosyl [2FE-2S] proteins

The neutral dinuclear iron nitrosyl complex [Fe₂(SC₃H₅N₂)₂(NO)₄] (1) of the “g = 2.03” family with a ligand analogous to natural mercaptohistidine was synthesized by the metathesis reaction of the thiosulfate ligands in the [Fe₂(S₂O₃)₂(NO)₄]²⁻ anion with imidazolidine-2-thiolate ligands. The electrochemical determination of nitrogen oxide in solution showed that compound 1 has a lower NO-donor ability compared to the iron complexes with 1-methylimidazole-2-thiol and imidazole-2-thiol synthesized earlier. Study of the magnetic properties of polycrystals of 1 demonstrated that the effective magnetic moment at room temperature is ca. 2.45 μ_B and corresponds to a molecule containing a pair of the noninteracting spins S = 1/2. This is evidence that each iron coordination unit in complex 1 contains one unpaired electron, and the iron atom is in the low-spin state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 28–34, January, 2007.     

Synthesis and magnetic studies of phthalato-bridged oxovanadium(IV) binuclear complexes

Six new μ-phthalato binuclear oxovanadium(IV) complexes, namely [(VO)₂(PHTH)-(L)₂]SO₄ (L denotes 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂ bpy); 5-nitro-1,10-phenanthroline (NO₂-phen); 5-chloro-1,10-phenanthroline (Cl-phen) and 5-methyl-1,10-phenanthroline (CH₃-phen), where PHTH is the phthalate dianion), have been synthesized and characterized by elemental analyses, IR, electronic spectra, magnetic moments at room temperature and molar conductivity measurements. The temperature dependence of the magnetic susceptibility of complexes [(VO)₂(PHTH)(phen)₂]SO₄ (1) and [(VO)₂(PHTH)(CH₃-phen)₂]SO₄ (2) was measured in 4—300 K range and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, ?=?2J?₁·?₂, giving the exchange integrals J=?12.8 cm^?1 for 1 and J=?7.9 cm^?l for 2. This indicates an antiferromagnetic spin-exchange interaction between the metal ions within each molecule.     

Tight binding prediction of the α-Gd2S3 magnetic structure

Spin-dependent extended Hückel tight binding (EHTB) calculations were carried out for the magnetic solid Gd₂S₃ by considering 20 different variations in the ordering of the 4f⁷ moments. The tight-binding calculations are used to interpolate the band structure of a nonmagnetic congener (Y₂S₃) and the 4f/5d,6s exchange interactions are introduced as perturbations via the introduction of spin-dependent H_dd and H_ss parameters. The calculations predict that Gd₂S₃ adopts an antiferromagnetic ordering of the 4f⁷ moments that is consistent with published neutron diffraction results. Our attempt to account for the calculated energies of the spin patterns using an Ising model was unsuccessful.     

Das erste quaternäre Oxocobaltat(I): CsK2[CoO2]

The First Quaternary Oxide of Monovalent Cobalt: CsK₂[CoO₂] Dark-red single crystals of CsK₂[CoO₂] were obtained via ?reaction with the cyliner surface”? by heating powders of Cs₂K₂Cd₃O₅ in closed Co-cylinders at 500°C during 48 d. Structure solution and refinement (four-circle diffractometer data, MoKα , 147 independent I_o(hkl), none was omitted, R = 3.42%, R_w = 2.24%) show close relationship with RbNa₂[NiO₂] [2]. The lattice-constants are: (powder data, standard deviations in parentheses) MAPLE calculations, investigations of magnetism and EPR measurement add to the monovalence of Co.