Molar Magnetic Susceptibility Research Articles

<b>Synthesis, characterization, antibacterial and antifungal studies of some transition and rare earth metal complexes of N-benzylidene-2-hydroxybenzohydrazide</b>

The solid complexes of Cu(II), Co(II), Mn(II), La(III) and Ce(III) were prepared from bidentate Schiff base, N-benzylidene-2-hydroxybenzohydrazide. The Schiff base ligand was synthesized from 2-hyhdroxybenzohydrazide and benzaldehyde. These metal complexes were characterized by molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, FTIR, 1H-NMR, UV-Vis and mass spectroscopy. The analytical data of these metal complexes showed metal:ligand ratio of 1:2. The physico-chemical study supports the presence of square planar geometry around Cu(II) and octahedral geometry around Mn(II), Co(II), La(III) and Ce(III) ions. The IR spectral data reveal that the ligand behaves as bidentate with ON donor atom sequence towards central metal ion. The molar conductance values of metal complexes suggest their non-electrolyte nature. The X-ray diffraction data suggest monoclinic crystal system for these complexes. Thermal behavior (TG/DTA) and kinetic parameters calculated by Coats-Redfern method are suggestive of more ordered activated state in complex formation. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli and fungicidal activity against Aspergillus niger and Trichoderma.KEY WORDS: Bidentate Schiff base, Metal complexes, Thermal analysis, XRD, Antimicrobial study Bull. Chem. Soc. Ethiop. 2011, 25(3), 381-391.

Novel multiferroic La 0.95Sb 0.05FeO 3 orthoferrite

A series of La 1− x Sb x FeO 3 was prepared using the conventional solid state method. XRD revealed the formation of the orthorhombic structure with space group Pbnm. The data showed that, the molar magnetic susceptibility and coercive field H C were increased from 9.16 × 10 −3 to 26.9 × 10 −3 emu g −1 mol and 1196 to 5465 Oe from for LaFeO 3 to La 0.95Sb 0.05FeO 3, respectively. The coercive field ( H C) of the sample with x = 0.05 increased 6 times than that of the parent LaFeO 3 and the saturation magnetization ( M s) was increased from 0.1614 emu g −1 for the parent LaFeO 3 to 0.2654 emu g −1 for the doped sample . The dielectric constant ( ɛ′) was increased with increasing the Sb 3+ content. The ac conductivity ( σ) increases from 2.36 × 10 −3 Ω −1 m −1 for the LaFeO 3 to 30 × 10 −3 Ω −1 m −1 for the sample La 0.95Sb 0.05FeO 3 at T = 553 K and frequency 1 MHz. The sample La 0.95Sb 0.05FeO 3 is concluded to be a novel single phase multiferroic material.

Synthesis, structure and magnetism of a 2-D organic–inorganic hybrid tetra-CoII-substituted sandwich-type Keggin germanotungstate: {[Co(dap)2(H2O)]2[Co(dap)2]2[Co4(Hdap)2(B-α-HGeW9O34)2]}·7H2O

Abstract A novel 2-D organic–inorganic hybrid tetra-CoII-substituted sandwich-type Keggin germanotungstate {[Co(dap)2(H2O)]2[Co(dap)2]2[Co4(Hdap)2(B-α-HGeW9O34)2]}·7H2O (1) (dap = 1,2-diaminopropane) has been hydrothermally synthesized and structurally characterized by elemental analyses, IR spectrum, UV spectrum, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and single-crystal X-ray diffraction. Structural analysis shows that 1 displays a rare 2-D (4,4)-topological network constructed by tetra-CoII-substituted sandwich-type Keggin germanotungstate units and [Co(dap)2]2+ bridges. To our knowledge, 1 represents the first 2-D organic–inorganic hybrid cobalt-substituted sandwich-type polyoxotungstate. Magnetic preperties of 1 have been investigated. The decrease of the product of the molar magnetic susceptibility at higher temperatures results from the spin-orbit coupling of the CoII ion and/or the antiferromagnetic interactions whereas the maximum at the lower temperatures is indicative of the ferromagnetic interactions within the tetranuclear CoII spin cluster in the sandwich belt.

The magnetic properties of Co-Mo-S coatings by electrodeposition

The nano-coated Co-s-Mo alloys were electrodeposited from electrolytic solutions containing CoSO4, Na2MoO4, ascorbic acid, thiourea, and hexamine. The coated Co-S-Mo alloys were obtained evolving to hard magnetic behaviour. The coatings characterised by metallic lustre. The surface morphology of the coating was investigated by scanning electron microscope (SEM). The many alloys were electrodeposited using these baths. Phase structure of the coatings was analyzed by the X-ray diffraction (XRD), the XRD patterns show sharp peaks for face-cantered cubic fcc (112) and hexagonal close packed hcp (110) structures. The molar magnetic susceptibility and effective magnetic moment were measured using Faraday's method. The composition and magnetic properties of the coatings greatly depended on the composition of the electrolytic bath mainly [] / [Co2+] ratio. The drastic modification of the magnetic properties of the coatings was closely related to the presence of the additives and inclusion of sulphur in the coatings, the increase of sulphur leads to decrease of the molar magnetic susceptibility. Key word: Co-S-Mo alloys, electrodeposition, magnetic properties.

Luminescent and magnetic properties of europium compounds with cinnamic acid

The temperature dependences of the molar magnetic susceptibility of luminescent europium compounds with cinnamic acid [Eu(Cin)3]n and Eu(Cin)3 · 2D · H2O (where Cin is the cinnamic acid anion and D is phen (1,10-phenanthroline) or dipy (2,2-dipyridyl)) were studied at temperatures from 300 to 2 K. The molar magnetic susceptibility of the compounds increased in the series Eu(Cin)3 · 2dipy · H2O < Eu(Cin)3 · 2phen · H2O < [Eu(Cin)3]n. The energy distances λlum between the 7F0 ground level and the 7F1 state in the luminescence spectra correlated well with λmagn obtained from magnetochemical data.

Bond-order wave phase of the extended Hubbard model: Electronic solitons, paramagnetism, and coupling to Peierls and Holstein phonons

The bond order wave (BOW) phase of the extended Hubbard model (EHM) in one dimension (1D) is characterized at intermediate correlation $U = 4t$ by exact treatment of $N$-site systems. Linear coupling to lattice (Peierls) phonons and molecular (Holstein) vibrations are treated in the adiabatic approximation. The molar magnetic susceptibility $\chi_M(T)$ is obtained directly up to $N = 10$. The goal is to find the consequences of a doubly degenerate ground state (gs) and finite magnetic gap $E_m$ in a regular array. Degenerate gs with broken inversion symmetry are constructed for finite $N$ for a range of $V$ near the charge density wave (CDW) boundary at $V \approx 2.18t$ where $E_m \approx 0.5t$ is large. The electronic amplitude $B(V)$ of the BOW in the regular array is shown to mimic a tight-binding band with small effective dimerization $\delta_{eff}$. Electronic spin and charge solitons are elementary excitations of the BOW phase and also resemble topological solitons with small $\delta_{eff}$. Strong infrared intensity of coupled molecular vibrations in dimerized 1D systems is shown to extend to the regular BOW phase, while its temperature dependence is related to spin solitons. The Peierls instability to dimerization has novel aspects for degenerate gs and substantial $E_m$ that suppresses thermal excitations. Finite $E_m$ implies exponentially small $\chi_M(T)$ at low temperature followed by an almost linear increase with $T$. The EHM with $U = 4t$ is representative of intermediate correlations in quasi-1D systems such as conjugated polymers or organic ion-radical and charge-transfer salts. The vibronic and thermal properties of correlated models with BOW phases are needed to identify possible physical realizations.

Tetranuclear, Oxygen Centered Copper(II) Clusters Linked Together with Guanidine-Guanidinate Ligands

The reaction of copper(I) chloride with Htbo (1,4,6-triazabicyclo[3.3.0]oct-4-ene) under reflux in THF with oxidation by oxygen, produces a neutral cluster comprising two oxo-tetra-copper(II) units connected by six tbo− bridges three of them bind two and the other three bind four metals; each unit also contains three chlorine bridges and a Htbo terminal ligand. Two different X-ray crystal structures (1a, 1b) have been determined and the magnetic behavior has been studied. The molar magnetic susceptibility measurements indicate strong exchange interactions within an oxo cluster with coupling constants of J 1 = −163 cm−1 and J 2 = −1.1 cm−1, and a weak interaction across the guanidinate bridges of J 3 = −5.2 cm−1 of the octa-CuII cluster.

Synthesis, Thermal Behavior, and Antimicrobial Activity of a Novel Macrocycle and its Transition Metal Complexes Derived from Thiosemicarbazide

ABSTRACT The present study reports the synthesis of Co(II), Ni(II), Mn(II), Cu(II), and Zn(II) complexes with a new macrocyclic ligand (L2)- 1,2,8,9,11,14-hexaazacyclopentadeca-12,13-dioxo-10,15-dithione-2,7-diene. The macrocycle was derived from thiosemicabazone (L1) and diethyloxalate that were prepared by the reaction of thiosemicarbazide and glutaraldehyde in the ratio of 2:1. The synthesized complexes and ligands were characterized by elemental analysis and molar conductance, magnetic susceptibility, 1HNMR, IR, electronic, and thermogravimetric analyses. The molar conductance values confirmed that the Ni(II), Cu(II), Zn(II), Mn(II) and Co(II) complexes were 1:2 electrolytes. On the basis of electronic spectral studies and molar conductance measurements, the authors proposed an octahedral structure for Ni(II), Mn(II), and Co(II) complexes, tetrahedral geometry for Zn(II) complex, and square planar geometry for Cu(II) complex. The thermal behavior of the compounds was studied by TGA in a nitrogen atmosphere up to 750°C at the rate of 20°C/min. The TGA results revealed that the complexes had higher thermal stability than the macrocycle. All the synthesized compounds were screened against 4 bacteria (i.e., Streptococcus aureus, Escherichia coli, Bacillus subtillis, Salmonella typhimurium) and 2 fungi (i.e., Fusarium oryzae, Candida albicans). The results showed that the metal complexes inhibited the growth of bacteria to a greater extent as compared to the ligand.

Sol-gel synthesis, surface and magnetic properties of nanocrystalline SmAlO 3

Nanocrystals of single-phase samarium monoaluminate (SmAlO 3) were synthesized and studied for the first time. Malic acid was employed as a new complexing agent in the sol-gel process. The material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), specific surface area and density. The lowest size of the nanoparticles was about 50-60 nm and some of them formed agglomerates. The binding energies of core-level electrons of Sm (3d, 4d, 4f, 5p, 5s), Al (2s, 2p) and O (1s, 2s) in nanocrystalline SmAlO 3 were obtained by X-ray photoelectron spectroscopy (XPS) and found shifted in respect to the corresponding values for the same elements. The temperature dependence of the AC magnetic susceptibility of the substance was determined between 2.5 and 250 K. The experimental molar magnetic susceptibility was compared with the theoretical one of Sm 3+ ions. The nanomaterial was found paramagnetic in the specified temperature range with Curie-type paramagnetism below 12 K.

Pyrophosphate-Bridged CuII Chain Magnet: {[Na3Cu(P2O7)(NO3)]·3H2O}n

A Cu(II)...Cu(II) pyrophosphate-bridged compound of formula {[Na(3)Cu(P(2)O(7))(NO(3))].3H(2)O}(n) (1) has been characterized. X-ray diffraction measurements show that it crystallizes in the monoclinic space group P2(1)/m, with unit cell dimensions a = 7.2492(5) A, b = 8.2446(6) A, c = 9.9050(7) A, beta = 107.123(1) degrees, and Z = 2. The structure consists of chains of Cu(II) cations at inversion symmetry sites bound to four equatorial oxygen atoms provided by two pyrophosphate anions halved by a symmetry plane and two axial oxygen atoms of nitrate anions. The molar magnetic susceptibility chi(0) of a powdered sample was measured in the temperature range 2 K < T < 273 K, and an isothermal magnetization curve, M(B(0),T), was obtained at T = 30 K, with the magnetic field B(0) between 0 and 5 T. Fitting a spin-chain model to the susceptibility data, we evaluate an antiferromagnetic exchange coupling 2J = -24.3(1) cm(-1) (defined as H(ex) = -2JS(i)S(j)) between Cu(II) neighbors. For any orientation of B(0), single-crystal electron paramagnetic resonance (EPR) spectra obtained at 9.8 and 33.9 GHz at 300 K display a single signal having a g matrix with orthorhombic symmetry, arising from the merger produced by the exchange interaction of the resonances corresponding to the two rotated Cu(II) sites. The g matrices of the individual molecules calculated assuming axial symmetry yielded principal values g(parallel) = 2.367(1) and g(perpendicular) = 2.074(1) at both frequencies, indicating a d(x(2)-y(2)) ground-state orbital for the Cu(II) ions. The angular variation of the EPR line width suggests exchange narrowing in a system with one-dimensional spin dynamics, as expected from the structure and susceptibility data. The results, discussed in terms of the crystal and electronic structures and of the spin dynamics of the compound, are compared with those obtained in other materials.

Influence of Co content on the characterization and magnetic properties of magnetite

Preparation of nanosized Co x Fe 3− x O 4; 0.05 ≤ x ≤ 0.20 particles from metal nitrates solution through citrate–precursor method was performed. XRD pattern of all prepared systems showed single phase with cubic spinel structure. The crystallite size was determined from TEM and found to agree with that calculated from Sherrer's equation (60–76 nm) The magnetic constants such as molar magnetic susceptibility ( χ M), Curie temperature ( T C) and saturation magnetization ( M S) were measured and the results indicated that, at x = 0.2 the values of χ M, M S, remanent magnetization ( M r,) and coercive field ( H c) are 23 emu/g mol, 77.62 emu/g, 33.17 emu/g and 574.5 Oe, respectively .

Magnetic properties of NiCuZn ferrite nanoparticles synthesized using egg-white

A new process to prepare single-phase nano-sized ferrites, Ni 0.8− x Cu 0.2Zn x Fe 2O 4 with x = 0.1–0.7, was developed using egg-white precursors. TG measurement showed that, the precursors must be calcined at 550 °C. XRD patterns indicated the formation of single-phase cubic ferrites with particle size in the range 28.7–48.4 nm. TEM image gave particle size agrees well with that estimated using XRD. FT-IR spectroscopy showed the characteristic ferrite bands. Hysteresis loops measurements exhibited an increase in the saturation magnetization value ( M s) up to zinc content of 0.2 followed by unexpected decrease, which suggests the preference of Zn 2+ ions to occupy octahedral sites. The decrease in the coercivity ( H c) with increasing zinc content is attributed to the lower magneto-crystalline anisotropy of Zn 2+ ions compared to Ni 2+ ions. Temperature dependence of the molar magnetic susceptibility ( χ M) suggested a ferrimagnetic behavior of the investigated samples and showed a decrease in the value of the Curie temperature ( T C) with increasing zinc.

Magnetic and Magneto-Transport Measurements of 57Fe-doped SrCoO3 and Sr1−x Cd x CoO3 Perovskites

In this article, the magneto-transport features of 57Fe isotope (1%) doped SrCoO3 (referred to as SrCo0.9957Fe0.01O3) perovskite compound have been investigated. The compound crystallized in cubic symmetry undergoes ferromagnetic transition around ∼270 K. The isothermal magnetization data collected at low temperature (1.8 K) indicates a characteristic of soft ferromagnet with saturation moment, Ms∼1.81 μB/Co. Interestingly, the electrical resistivity, ρ(T), measurements indicate semiconducting properties while metallic nature is seen for the pristine compound. The SrCo0.9957Fe0.01O3 sample shows temperature and field dependence of magnetoresistance, MR, around 1.5%, which is rather smaller than of the pristine perovskite. The second part of the present work reports the attempt to dope Cd on Sr-site in the perovskite structure, Sr1−xCdxCoO3, under extreme conditions. A minimum amount of about x=0.05, 0.1 is tested for solid solution in the Sr1−xCdxCoO3 structure. However, the structural data indicate that Cd is not fully doped in the matrix for x=0.05, 0.1 samples; some of the CdO is intact as an impurity and it did not show major impact on the physical properties of the samples. The ρ(T) data reveal metallic nature for both x=0.05 and 0.1 samples with relatively low resistivity at low temperature regions, and they exhibit −MR ∼4% around ∼250 K. For x=0.05 the molar magnetic susceptibility of the sample shows ferromagnetic transition at Tc=244 K, whereas x=0.1 sample exhibits ferromagnetism at Tc=264 K. The effective Bohr magnetron parameter, peff, determined for x=0.05 and 0.1 samples is found to be 3.10 μB/Co and 3.25 μB/Co, respectively, and these data suggest intermediate spin state for Co4+ ion for both the samples. The M(H) data for both the samples reveal soft ferromagnetism. The Ms of x=0.05 reaches 1.9 μB/Co and of x=0.1 reaches 1.86 μB/Co at 1.8 K and 70 kOe conditions.

Electrocatalytic evolution of hydrogen on a novel SrPdO 3 perovskite electrode

SrPdO 3 was prepared for the first time by the citrate method. XRD, SEM and TGA characterizations were carried out. The catalytic activity toward hydrogen evolution reaction (HER) was investigated, the activation energy, and reaction order and reaction mechanism have been determined using Tafel polarization and impedance techniques. The modified surface showed up to 100 times more efficiency towards electrocatalytic production of hydrogen. Adsorption of hydrogen on the catalyst was the rate-determining step and the reaction order at the surface of the catalyst is 0.86. The molar magnetic susceptibility was measured using Faraday's method and anti-ferromagnetic character was observed.

Synthesis and characterization of a tetraaza macrocyclic ligand and its Cobalt(II), Nickel(II) and Copper(II) complexes

Co(II), Ni(II), and Cu(II) complexes with a tetradentate nitrogen donor [N4] macrocyclic ligand, viz 1,5,8,13-tetraaza-2,9-dimethyl-4,11- diphenylcyclotetradeca-2,4,4,11-tetraene were synthesized. Their structures were determined based on elemental analyses; molar conductance and magnetic susceptibility measurements; and IR, 1H-NMR (ligand), and electronic spectral studies. Based on analytical and molar conductance data, the complexes may be formulated as [M(L)Cl2] and [M?(L)]Cl2 [where M = Co(II) and Cu(II), and M? = Ni(II)] due to their non-electrolytic and 1:2 electrolytic nature. Based on spectral studies, an octahedral geometry was assigned for the Co(II) complex, whereas square-planar and tetragonal geometry were proposed for the Ni(II) and Cu(II) complexes, respectively. The synthesized ligand and its complexes were screened for fungicidal activity against two pathogenic fungi (i.e., Fusarium. moniliformae and Rhizoctonia solani) to assess their growth inhibiting potential.

Luminescence and magnetic properties of mixed-ligand europium trifluoroacetates

The luminescence and magnetic properties of mixed-ligand europium trifluoroacetates with nitrogen- and phosphorus-containing neutral ligands [Eu(TFA)3 · 3H2O]2 and Eu(TFA)3 · 2D · nH2O were studied (here TFA is the trifluoroacetic acid anion, and D is Phen (1,10-phenanthroline), n = 1; DMF (dimethylformamide), n = 1; or TPPO (triphenylphosphine oxide), n = 3). The molar magnetic susceptibility increased in the series of complex compounds Eu(TFA)3 · 2Phen · H2O < [Eu(TFA)3 · 3H2O]2 < Eu(TFA)3 · 2DMF · H2O < Eu(TFA)3 · 2TPPO · 3H2O. Correlations were found between the luminescent and magnetic characteristics of the complex compounds.

Crystal Growth, Transport, and the Structural and Magnetic Properties of Ln4FeGa12 with Ln = Y, Tb, Dy, Ho, and Er

Ln(4)FeGa(12), where Ln is Y, Tb, Dy, Ho, and Er, prepared by flux growth, crystallize with the cubic Y(4)PdGa(12) structure with the Im3m space group and with a = 8.5650(4), 8.5610(4), 8.5350(3), 8.5080(3), and 8.4760(3) A, respectively. The crystal structure consists of an iron-gallium octahedra and face-sharing rare-earth cuboctahedra of the Au(3)Cu type. Er(4)Fe(0.67)Ga(12) is iron-deficient, leading to a distortion of the octahedral and cuboctahedral environments due to the splitting of the Ga2 site into Ga2 and Ga3 sites. Further, interstitial octahedral sites that are unoccupied in Ln(4)FeGa(12) (Ln = Y, Tb, Dy, and Ho) are partially occupied by Fe2. Y(4)FeGa(12) exhibits weak itinerant ferromagnetism below 36 K. In contrast, Tb(4)FeGa(12), Dy(4)FeGa(12), Ho(4)FeGa(12), and Er(4)Fe(0.67)Ga(12) order antiferromagnetically with maxima in the molar magnetic susceptibilities at 26, 18.5, 9, and 6 K. All of the compounds exhibit metallic electric resistivity, and their iron-57 Mossbauer spectra, obtained between 4.2 and 295 K, exhibit a single-line absorption with a 4.2 K isomer shift of ca. 0.50 mm/s, a shift that is characteristic of iron in an iron-gallium intermetallic compound. A small but significant broadening in the spectral absorption line width is observed for Y(4)FeGa(12) below 40 K and results from the small hyperfine field arising from its spin-polarized itinerant electrons.

A study on Cu substituted Ni–Cu–Zn ferrites synthesized using egg-white

This paper examines the effect of copper substitution on the structural and magnetic properties in nano-crystalline ferrite series of nominal composition; Ni0.7−xCuxZn0.3Fe2O4 (where x = 0.1–0.6) synthesized by a simple method using metal nitrates and freshly extracted egg-white. X-ray diffraction measurements (XRD) confirmed the formation of single-phase cubic spinel structure. The average crystallite size was calculated using XRD pattern and confirmed by transmission electron microscope (TEM). The nearly constant lattice parameters obtained with Cu substitution was attributed to the small difference in the ionic radius between Ni2+ and Cu2+ ions. FT-IR spectra showed two absorption bands assigned to the tetrahedral and octahedral complexes. The effect of Cu concentration on the magnetic properties was investigated using vibrating sample magnetometer (VSM) and molar magnetic susceptibility measurements. The decrease in the saturation magnetization and the Curie temperature values with increasing Cu content was explained in terms of the magnetic moments and magnetic exchange interaction existing between the antiparallel uncompensated electron spin of A and B sublattices. The magnetic measurements also proved that the entire preparation method has a great effect on enhancing the magnetic properties of the system.

Synthesis, Characterization, and Magnetism of Divalent Aryl Transition-Metal Complexes of the Simplest Dialkylamide, NMe2: Rare T-Shaped Coordination at Chromium

The synthesis and characterization of a series of first-row aryl transition metal derivatives of the simplest dialkylamido ligand NMe(2) are reported. The complexes Cr{Ar'Cr(mu-NMe(2))(2)}(2) (1) and {Ar'M(mu-NMe(2))}(2) (M = Mn (2), Fe (3); Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2)) were obtained by reaction of the aryl metal halides {Ar'M(mu-X)}(2) (M = Cr, X = Cl; M = Fe, X = Br) or {Li(THF)Ar'MnI(2)}(2) with LiNMe(2) in a 1:2 ratio. A similar reaction of {Ar(#)Co(mu-I)}(2) (Ar(#) = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2)) and LiNMe(2) in hexanes gave the unusual complex {Ar(#)Co(mu-I)(eta(1)-CH(2) horizontal lineNCH(3))}(2) (4), in which the NMe(2) ligand is dehydrogenated to afford a complexed imine. Complexes 1-4 were characterized by X-ray crystallography, UV-vis spectroscopy, and magnetic measurements. In the unique trinuclear complex 1, the central chromium(II) ion is bound to four NMe(2) groups in a square planar fashion. The NMe(2) groups also bridge to the two outer chromium(II) ions, which are bound to a terminal Ar' group to yield a rare example of three-coordinate T-shaped geometry at these atoms. In the dimers 2 and 3, each metal center is coordinated to a terminal terphenyl ligand and two bridging NMe(2) groups to give a distorted trigonal planar geometry. In contrast, the reaction of LiNMe(2) with {Ar(#)Co(mu-I)}(2) in a 2:1 ratio did not yield an amido product; instead, the NMe(2) ligand underwent hydrogen elimination. As a result, in the dimeric structure of 4, each cobalt ion is coordinated to a terphenyl ligand, two bridging iodides, and a neutral methylimine ligand, CH(2) horizontal lineNCH(3), to yield a very distorted tetrahedral cobalt(II) coordination environment. The magnetic properties of 1-4 revealed antiferromagnetic exchange coupling between the metal ions with J = -47(1) cm(-1) and J(13) = -25(1) cm(-1) for 1, J = -38(1) cm(-1) for 2, J = -75(3) cm(-1) for 3, and J = -32(4) cm(-1) for 4; the latter compound exhibited an unusually large temperature independent contribution to its molar magnetic susceptibility.

Structural and Electrochemical Characterization of Li2MnSiO4 Cathode Material

The candidate cathode material Li2MnSiO4 for lithium-ion cells was synthesized by an all-acetate precursor sol/gel method under a reducing atmosphere at 600, 700, and 800 °C. The material prepared at 700 °C was a pure phase and had the structural order of Li3PO4 orthorhombic (S.G. Pmn21) phase. The temperature dependence of the molar magnetic susceptibility of Li2MnSiO4 was found to be consistent with an antiferromagnetic material with a Neel temperature of 12 K. The calculated effective moment confirmed that the observed magnetic behavior involves Mn2+ ions in a high spin configuration in tetrahedral sites. Scanning electron microscopy of Li2MnSiO4 showed large aggregates (10 to 50 μm) composed of nanosized particles (100−200 nm). The as-prepared material was almost electrochemically inactive despite the presence of 15 wt % carbon additive. The material was treated by carbon coating using cellulose carbon source precursor and particle size reduction using high-energy ball milling. In coin-cell tests, the...