Molar Magnetic Susceptibility Research Articles

Ni(II) Complex of N2O3 Donor Unsymmetrical Ligand and Its Use for the Synthesis of NiII-MnII Complexes of Diverse Nuclearity: Structures, Magnetic Properties, and Catalytic Oxidase Activities.

A new mononuclear Ni(II) complex [NiL] (1) of an unsymmetrically dicondensed N2O3 donor ligand, H2L ( N-α-methylsalicylidene- N'-3-methoxysalicylidene-1,3-propanediamine), has been synthesized. Complex 1 on reaction with Mn(ClO4)2·6H2O and NaN3 in different molar ratios yielded three novel heterometallic NiII-MnII complexes, [(NiL)2Mn(N3)](ClO4) (2), [(NiL)2Mn2(N3)2(μ1,1-N3)2(CH3OH)2] (3), and [{(NiL)2Mn}2(μ1,3-N3)(H2O)]·(CH3OH),(ClO4)3 (4). The single crystal structure analyses show a trinuclear NiII2MnII structure for complex 2 and a tetranuclear NiII2MnII2 structure where two dinuclear NiIIMnII units are connected via μ1,1-azido and phenoxido bridges for complex 3. Complex 4 possesses a hexanuclear structure where two trinuclear NiII2MnII units are connected via a μ1,3-azido bridge. The temperature-dependent dc molar magnetic susceptibility measurements reveal that complexes 3 and 4 are antiferromagnetically coupled with the exchange coupling constants ( J) of -4.97, -0.14, -0.55 cm-1 for 3 and -3.94 cm-1 for 4. All complexes 2-4 show biomimetic catalytic oxidase activities. For catecholase like activity, the turnover numbers ( Kcat) are 768, 1985, and 2309 h-1 for complexes 2-4, respectively, whereas for phenoxazinone synthase like activity, the turnover numbers are 3240, 3360, and 13 248 h-1 for complexes 2-4, respectively. This difference in catalytic efficiencies is attributed to the variations in structures of the complexes and formation of active NiII-MnII species in solution during catalysis. The mass spectral analyses suggest the probable intermediate formation and cyclic voltammetry measurement suggest the reduction of Ni(II) to Ni(I) during catalytic reaction. The very high catalytic efficiencies for aerial dioxygen activation of all these heterometallic complexes as well as the highest activity of 4 is attributed to the coordinatively unsaturated penta-coordinated geometry or hexa-coordinated geometry with a solvent water molecule around Mn(II).

Structural, spectroscopic and quantum chemical studies on copper(II) complex of 4-ethoxy-2-methyl-5-(4-morpholinyl)-3(2H)-pyridazinone

The Cu(II) complex compound (Cu(C11H17N3O3)2Cl2(H2O)2) was synthesized from reaction between the copper(II) chloride dihydrate and the 4-ethoxy-2-methyl-5-(4-morpholinyl)-3(2H)-pyridazinone. The Cu(II) complex compound in octahedral geometry was characterized using elementel analysis, FT-IR and UV–Vis. spectroscopic techniques. The molar conductance and magnetic susceptibility of the Cu(II) complex were experimentally investigated to confirm octahedral geometry. The quantum chemical computations for molecular geometric parameters, vibrational wavenumber, UV–Vis. parameters, HOMO-LUMO investigations and NBO analysis of the complex compound were performed by using UHSEh1PBE functional in DFT method at the LanL2DZ basis set. The vibrational analysis was performed to determine metal-ligand bond and ligand vibrations. The HOMO and LUMO analyses were investigated to understand charge transfers and electronic transitions in the complex. The electronic configuration, natural charge and coordination environment of the Cu(II) metal ion was investigated via NBO analysis. The experimental results were compared with computed data.

Crystal structure and magnetic properties of the novel compound Sc5Pd2In4

The novel intermetallic indide Sc5Pd2In4 was synthesized by arc-melting technique, and its crystal structure was determined using the single-crystal X-ray diffraction data (R1 = 0.0233, wR2 = 0.0687). The compound was found to crystallize with an orthorhombic structure of the Lu5Ni2In4 type (space group Pbam), with the lattice parameters: a = 17.4748(7), b = 7.6674(3) and c = 3.3815(2) Å. The magnetic behaviour in Sc5Pd2In4 was studied in the temperature range 1.72–400 K. The compound was established to be a Pauli paramagnet with the molar magnetic susceptibility of about 3.4 × 10−4 emu/mol.

Tri- and hexa-nuclear NiII-MnII complexes of a N2O2 donor unsymmetrical ligand: synthesis, structures, magnetic properties and catalytic oxidase activities.

A new mononuclear Ni(ii) complex, [NiL] (1) of an unsymmetrically dicondensed N2O2 donor ligand, H2L (where H2L = N-α-methylsalicylidene-N'-salicylidene-1,3-propanediamine), has been synthesized. Complex 1, on reaction with Mn(ii) in the presence of different co-anions, yielded three heterometallic NiII-MnII complexes, [(NiL)2Mn(NCS)2]·CH3CN (2), [(NiL)2Mn(N3)(H2O)](ClO4)·H2O (3) and [{(NiL)2Mn(H2O)}2(μ1,3-N3)](ClO4)3 (4). Single crystal structural analyses show that complexes 2 and 3 contain similar bent trinuclear NiII2MnII structures, with the difference that in complex 2 two SCN- ions and in 3, one N3- and one H2O molecule are coordinated to the Mn(ii) centre. Complex 4 possesses a hexanuclear structure, in which two trinuclear NiII2MnII units are connected via a single μ1,3-azido bridge. Variable temperature dc molar magnetic susceptibility measurements reveal that the two Mn(ii) centres in complex 4 are antiferromagnetically coupled with an exchange coupling constant (J) of -3.73 cm-1. Among the three heterometallic complexes, only 3 and 4 show bio-mimetic catalytic oxidase activities. For catecholase like activity, the turnover numbers (Kcat) of complexes 3 and 4 are 984 and 2081 h-1, respectively, whereas for phenoxazinone synthase-like activity, the turnover numbers of complexes 3 and 4 are 6351 and 10 545 h-1, respectively. The high catalytic oxidase activities of complexes 3 and 4 in contrast to the inactivity of complex 2 are attributed to the coordination of a water molecule to the Mn(ii) centre in the former structures, which facilitates the binding of the substrate with the catalyst. Mass spectral analyses suggest the probable formation of a complex-substrate intermediate in these catalytic reactions and cyclic voltammetry measurements show that Ni(ii) is reducible to Ni(i).

Synthesis and Characterization of New Bidentate Schiff Base Ligand Type (NO) Donor Atoms Derived from Isatin and 3-Amino Benzoic Acid and Its Complexes with Co(II), Cu(II), Cd(II) and Hg(II) Ions

New bidentate Schiff base ligand (L) namely [(Z)-3-(2-oxoindolin-3ylildeneamino)benzoic acid] type (NO) was prepared via condensation of isatin and 3-amino benzoic acid in ethanol as a solvent in existence of drops of (glac. CH3COOH). The new ligand (L) was characterized base on elemental microanalysis, FT-IR, UV-Vis, 1H-NMR spectra along with melting point. Ligand complexes in general formula [M(L)2Cl2]. H2O, where: MII = Co, Cu, Cd, and Hg; L= C15H10 N2O3 were synthesized and identified by FT-IR, UV-Vis, 1H-NMR (for Cd complex only) spectra, atomic absorption, chloride content along with molar conductivity and magnetic susceptibility. It was found that the ligand behaves as bidentate on complexation via (N) atom of imine group and (O) atom of carbonyl group of five member ring. The electronic spectral data and µeff values (Co, Cu) of the complexes exhibited octahedral geometry around CoII, CuII, CdII, HgII metal ions. The results of antibacterial activity showed that only Hg(II) complex has high activity (35 mm) for staphylococcus aureas.

Role of A Cation Vacancy in the Exchange-Biased LaFeO3 Multiferroic Nanocrystals

Multiferroic samples with the chemical formula La $_{1-x}\square _{x}$ FeO3 (0.0 ≤ x ≤ 0.03) were successfully prepared in nanoscale by citrate nitrate combustion method. XRD data reveals crystallized single-phase orthorhombic symmetry for the prepared nanopowder. All measured magnetic parameters point to the antiferromagnetic character with weak ferromagnetic moment. The value of the molar magnetic susceptibility (χ M ) for La $_{\mathrm {0.99}}\square _{\mathrm {0.01}}$ FeO3 reaches 3.5 times that of the undoped sample. The saturation magnetization of the samples La $_{\mathrm {0.99}}\square _{\mathrm {0.01}}$ FeO3 and La $_{\mathrm {0.97}}\square _{\mathrm {0.03}}$ FeO3 increased two times as compared with that of the parent one. The exchange bias (EB) effect was observed for 1st time at room temperature and originated from antiferromagnetic–ferromagnetic (AFM-FM) interface effect. Ferroelectric hysteresis loop was observed at room temperature for the samples which highlighted the presence of the ferroelectric ordering. A huge enhancement in the saturation (P s), the remnant polarization (P r), and the coercive electric field (E c) of the sample La $_{\mathrm {0.98}}\square _{\mathrm {0.02}}$ FeO3 by 7.5, 24, and 12 times, respectively, when compared with the parent sample LaFeO3. Based on the obtained results, the investigated samples are categorized in type I multiferroics.

Synthesis, Spectral Characterization, Antitumor, Antioxidant, and Antimicrobial Studies of New Potential ONS Schiff Base Complexes

Novel Co(II), Ni(II), Cu(II), and Zn(II) complexes derived from 2‐aminopyridine‐3‐thiol and 4‐oxo‐4H‐chromene‐3‐carbaldehyde were synthesized and characterized by spectroscopic (IR, 1H NMR, UV–vis, ESR, and MS) and other analytical methods. Molar conductance data and magnetic susceptibility measurements provide evidence for the monomeric and monobasic nature of the complexes. The molar conductance measurement of the complexes in DMSO corresponds to their non‐electrolytic nature. All the complexes are of high‐spin type. On the basis of the different spectral studies, the six‐coordinated geometry may be assigned for all the complexes. IR spectral studies indicate the binding sites of the ligand with the metal ion. The Schiff base acts as tridentate ligand coordinated through deprotonated thiolic (SH) sulfur, azomethine (─CH═N─) nitrogen, and carbonyl (−C═O) oxygen atoms. The ligand field parameters were calculated for Co(II) and Ni(II) complexes and their values were found to be in the range reported for an octahedral structure. The data show that the complexes have an ML2‐type composition. The activation thermodynamic parameters are calculated using the Coast–Redfern, Horowitz–Metzger (HM), Piloyan–Novikova (PN), and Broido equations. The X‐ray diffraction data suggest a triclinic system for all compounds. Different surface morphologies were identified from SEM micrographs. Human tumor cell lines A427 (lung cancer cell line), LCLC‐103H (large cell lung cancer), SISO (uterine adenocarcinoma), and 5637(human bladder carcinoma) grown in RPMI‐1640 medium were elevated. The biological screening data show that the complexes show growth inhibitory activity against various microorganisms. The octahedral geometry of the complexes is confirmed using density functional theory (DFT) from DMOL3 calculations, electronic and magnetic moment measurements, ESR, and ligand field parameters.

Geometrical structures, thermal properties and spectroscopic studies of Schiff base complexes: Correlation between ionic radius of metal complexes and DNA binding

A novel series of transition metal complexes of Cu(II), Co(II), Ni(II), Mn(II) and Cd(II) were prepared from Schiff base derived from 4-aminoantipyrine and quinoline-2-carbaldehyde to give 4-((quinolin-2-yl)methyleneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (QMP). The structural features were derived from elemental analysis, mass spectroscopy, X-ray, IR, 1H NMR, electronic spectra, molar conductance magnetic susceptibility and thermogravimetric studies. On the basis of the studies the coordination sites were proven to be through oxygen of the ring CO and nitrogen of the azomethine (HCN) group. The thermodynamic parameters were calculated using Coats–Redfern and Horowitz–Metzger methods. From the values of the thermal activation energy of decomposition (Ea) of Schiff base (QMP) and its metal complexes (1–5), it was found that the Ea value for the complex (3) is higher compared to the other complexes. The Gibbs free energy of decomposition (ΔG⁎) for Schiff base (QMP) and its metal complexes is positive value which indicates that the processes are non-spontaneous. The interaction between Schiff base (QMP) and its metal complexes and calf thymus DNA shows hypochromism effect coupled with obvious bathochromic shift. From the values of binding constant (Kb) we noted that the highest value of Kb is belong complex (3) and these indicated that the Ni(II) is highly binding with CT-DNA and these due to the lower ionic radius. Furthermore, quantum chemical parameters of Schiff base and its complexes were calculated and discussed. The antimicrobial activity of Schiff base (QMP) and its M(II) complexes were studied and compared with the standard antibacterial and antifungal drugs.

Dicobaloxime/organodicobaloximes bridged by different axial groups: synthesis, characterization, spectroscopy, and catalysis

In this study, the various ligands axially coordinated to two cobalt center bound to the N4-oxime core in 12 new dicobaloxime/organodicobaloxime (1–12) complexes have been synthesized and characterized by NMR (1H and 13C), UV–Visible, FT-IR, LC–MS, molar conductivity analysis, melting point, and magnetic susceptibility experiments with elemental analysis. These spectroscopic results indicate that the formation of new dicobaloxime/organodicobaloxime (1–12) complexes. The (C=N–OH) peaks disappeared in the 1H-NMR spectrum of dicobaloxime/organodicobaloxime (1–12) complexes, while new peaks were observed at range 20.18–18.33 ppm, indicating that the groups of ligands have been transformed to intramolecular H-bridge (O–H⋯O). The dicobaloxime (1–6) species give a better cyclic voltammogram as compared to its organodicobaloxime derivatives (7–12) due to cyclic voltammograms of the organodicobaloximes (7–12) were poor. This is possibly due to the enhanced σ donation by R groups in the organocobaloximes which are substantially stabilized. The organodicobaloxime (10) showed much better catalytic activity compared to the other cobaoxime complexes. The different dicobaloxime (1–6) and organodicobaloximes (7–12) have been synthesized for the first time. Their redox properties were investigated using cyclic voltammetric (CV) techniques in a DMSO solution. These dicobaloximes/organodicobaloximes have been used as homogeneous catalyst for synthesis of cyclic carbonates presence of DMAP as co-catalyst.

Unusual saccharin-N,O (carbonyl) coordination in mixed-ligand copper(II) complexes: Synthesis, X-ray crystallography and biological activity

Three tridentate Schiff bases containing N and S donor atoms were synthesized via the condensation reaction between S-2-methylbenzyldithiocarbazate with 2-acetyl-4-methylpyridine (S2APH); 4-methyl-3-thiosemicarbazide with 2-acetylpyridine (MT2APH) and 4-ethyl-3-thiosemicarbazide with 2-acetylpyridine (ET2APH). Three new, binuclear and mixed-ligand copper(II) complexes with the general formula, [Cu(sac)(L)]2 (sac = saccharinate anion; L = anion of the Schiff base) were then synthesized, and subsequently characterized by IR and UV/Vis spectroscopy as well as by molar conductivity and magnetic susceptibility measurements. The Schiff bases were also spectroscopically characterized using NMR and MS to further confirm their structures. The spectroscopic data indicated that the Schiff bases behaved as a tridentate NNS donor ligands coordinating via the pyridyl-nitrogen, azomethine-nitrogen and thiolate-sulphur atoms. Magnetic data indicated a square pyramidal environment for the complexes and the conductivity values showed that the complexes were essentially non-electrolytes in DMSO. The X-ray crystallographic analysis of one complex, [Cu(sac)(S2AP)]2 showed that the Cu(II) atom was coordinated to the thiolate-S, azomethine-N and pyridyl-N donors of the S2AP Schiff base and to the saccharinate-N from one anion, as well as to the carbonyl-O atom from a symmetry related saccharinate anion yielding a centrosymmetric binuclear complex with a penta-coordinate, square pyramidal geometry. All the copper(II) saccharinate complexes were found to display strong cytotoxic activity against the MCF-7 and MDA-MB-231 human breast cancer cell lines.

Synthesis, characterization and antibacterial activity evaluation of trinuclear Ni(II) complexes with N-substituted salicylhydrazide ligands

Three novel trinuclear Ni(II) complexes, [Ni3(L1)2(py)4] (1), [Ni3(L2)2(H2O)2(DMA)2] (2) and [Ni3(L3)2(py)4] (3), with trianionic pentadentate ligands derived from salicylhydrazide with N-acyl substituents [H3L1=N2-crotonoylsalicylhydrazide, H3L2=N2-(3,3-dimethylacryloyl)salicylhydrazide, H3L3=N2-cinnamoylsalicylhydrazide] were synthesized and characterized by elemental analysis, spectroscopic techniques, like UV–Vis, FT-IR and NMR, molar conductivity and magnetic susceptibility measurements, and single crystal X-ray diffraction. The solid state structures of the complexes reveal the binding modes of the different ligands via ONO donor atoms. Complex 1 crystallises in the triclinic system while complexes 2 and 3 crystallise in the monoclinic system with space groups P1¯ (1) and P21/c (2 and 3). Computational studies were performed using Density Functional Theory (DFT) to obtain physical properties of all three complexes. The ligands and their metal complexes were screened for antibacterial activity to assess their inhibition potential against two Gram positive bacteria; Staphylococcus aureus and Bacillus subtilis and two Gram negative bacteria; Escherichia coli and Pseudomonas aeruginosa by the well diffusion method using gentamicin as a positive control. Antibacterial screening data reveals that the trinuclear Ni(II) complexes have significantly enhanced inhibitory activities compared to the ligands.

Synthesis, Characterization and Biological Approach of N’-(3-(Hydroxy Imino) Butan-2-ylidene)-2-Oxo-2H-Chromene-3-Carbohydrazide Complexes

A series of metal complexes of Cu(П), Co(П), Ni (П), Cd(П) and Hg(П) complexes with N’-(3-(hydroxyimino) butan- 2-ylidene)-2-oxo-2H-chromene-3-carbohydrazide (H2L) were prepared. The structures illuminated by elemental and thermal analysis, besides spectroscopic methods (IR, 1H NMR, and UV-visible, MS) and physical measurements (molar conductance and magnetic susceptibility). In addition, DFT method used to approve the geometry of solid complexes. From conductmetric measurements, all complexes were non-electrolytic and formed by molar ratio 1:2 expect Hg(П) complexes by 1:1. Moreover, the biological activity (Antibacterial, antifungal and DNA binding) performed for all prepared compounds.

Physiochemical and Antibacterial Activity Investigation on Noble Schiff Base Cu(II) Complex

Schiff base ligand and its Cu(II) complex had been synthesized by the condensation reaction of isatin with amino acids (cysteine / glycine / leucine / alanine ). The Structure and spectral properties of ligand and complex were confirmed by UV, FT-IR and some physiochemical measurements. The spectral properties showed that it was a distorted tetrahedral geometry with a tridentate ligand and chloride ion. IR spectral studies show the binding sites of the Schiff base ligand with the metal ion. Molar conductance data and magnetic susceptibility measurements give evidence for monomeric and non-electrolytic nature of the complexes. The Schiff base Cu(II) complex was subjected to antimicrobial studies screened by employing the Disc Diffusion method. All the synthesized complexes showed strong antibacterial activity.

Cis-Thioindigo (TI) - a new ligand with accessible radical anion and dianion states. Strong magnetic coupling in the {[TI-(μ2-O),(μ-O)]Cp*Cr}2 dimers.

Reaction of decamethylchromocene (Cp*2Cr) with thioindigo (TI) yields a coordination complex {[TI-(μ2-O), (μ-O)]Cp*Cr}2·C6H14 (1) in which one Cp* ligand in Cp*2Cr is substituted by TI. TI adopts cis-conformation in 1 allowing the coordination of both carbonyl groups to chromium. Additionally, one oxygen atom of TI becomes a μ2-bridge for two chromium atoms to form {[TI-(μ2-O), (μ-O)]Cp*Cr}2 dimers with a CrCr distance of 3.12 Å. According to magnetic data, diamagnetic TI2- dianions and two Cr3+ atoms with a high S = 3/2 spin state are present in a dimer allowing strong antiferromagnetic coupling between two Cr3+ spins with an exchange interaction of -35.4 K and the decrease of molar magnetic susceptibility below 140 K. Paramagnetic TI˙- radical anions with the S = 1/2 spin state have also been obtained and studied in crystalline {cryptand[2,2,2](Na+)}(TI˙-) (2) salt showing that both radical anion and dianion states are accessible for TI.

Study the effect of Gd3+ incorporation into nanocrystalline (Ni–Ti) substituted Mn–Zn ferrites on its structure and functional properties

Ferrite samples with general chemical formula Mn0.9Zn0.1Ni0.05Ti0.05GdtFe1.9−tO4; (0.0≤ t≤0.05; step 0.01) were prepared using solid state reaction technique and the effect of Gd3+ ions incorporation on its physical properties has been studied. From the obtained results, XRD analysis reveals that the samples have a cubic spinel single phase structure for 0.0≤ t≤0.02; while for t≥0.03 a small peak of secondary phase (Gd3Fe5O12) appears and becomes more noticeable with increasing Gd content. The lattice parameter (a) of the prepared samples was found to be initially increases and then decreases with increasing Gd content which may be attributed to the difference in the ionic radii of the cations involved and the solubility limit of Gd3+ ions. The crystallite size of the samples was estimated using Scherrer's equation and ranged from 96nm to 107nm. A vibrating sample magnetometer (VSM) was used at room temperature in order to study the effect of Gd content on the magnetic hysteresis parameters of the prepared ferrites such as saturation magnetization and coercivity. DC molar magnetic susceptibility (χM) for the prepared samples was measured using Faraday's method as a function of temperature and the Curie temperature was calculated from the magnetic susceptibility measurements. Also the DC resistivity of the samples was measured at room temperature. The obtained results show that, the substitution by Gd3+ ions improves the electrical properties of the samples by increasing it DC electrical resistivity by 118% and consequently decreases it eddy current loss while the saturation magnetization slightly decreased by 14% only. The sample of t=0.01 shows a high dc magnetic susceptibility, high saturation magnetization (43.1emu/g), high electric resistivity 12×103Ω.m and high Curie temperature (496K), which is useful in some technological applications such as transformer and inductor cores.

"Particle-Free" Magnetic Actuation of Droplets on Superhydrophobic Surfaces Using Dissolved Paramagnetic Salts.

Magnetic actuation is a droplet manipulation mechanism in digital microfluidics (DMF), where droplets can be actuated over a (super)hydrophobic surface with a magnetic force. Superparamagnetic particles or ferromagnetic liquids are added to the droplets to provide a "handle" by which the magnet can exert a force on the droplet. In this study, we present a novel method of magnetic manipulation, where droplets instead contain paramagnetic salts with molar magnetic susceptibilities (χm) approximately ≈10 000× < that for superparamagnetic particles. Droplet actuation is facilitated by low surface friction on fluorous silica nanoparticle-based superhydrophobic coatings, where <2 μN is required for reproducible droplet actuation. Different paramagnetic salts with χm from ≈4500 to 72 000 (× 10-6 cm3 mol-1) were used to make aqueous solutions of different concentration and tested for droplet actuation and sliding angle using permanent magnets (1.8-2.1 kG). Paramagnetic salts are compared in terms of solubility, minimum required concentration, and maximum droplet velocity before disengagement. There is a strong correlation between the magnetic susceptibility of the salt solution, its concentration, and ease of actuation. As an application example, droplets containing a paramagnetic salt and doxorubicin (leukemia drug) are magnetically actuated and interrogated using laser-induced fluorescence. Signal attenuation due to the MnCl2 salt was examined, and the Stern-Volmer quenching constant was determined.

SYNTHETIC AND SPECTRAL STUDIES OF COMPLEXING BEHAVIOR OF ISOTHIO CYANATO COMPLEXES OF 4 [N-4-ETHOXY BENZALIDINE AMINO] ANTIPYRINE (C20H21N3O2)

Trivalent Lanthanides behave as hard acid and thus are expected to form stronger stable complexes with ligands having N-donor atoms. Coordination number less than six are uncommon for the lanthanides. Substituted Pyrazolones have been reported to posses’ strong pharmaceutical properties.Complexes were prepared by adding 40 ml hot ethanolic solution of ligand (3M mol) to ethanolic solution of lanthanide (III) isothiocyanate (1M mol). Molar conduction, molecular weight, magnetic susceptibility, infrared and electronic spectroscopy were used to characterization of newly synthesized complexes

Magnetic properties of Co3O4 polycrystal powder

The results of investigations of magnetic properties of Co3O4 polycrystals in powder morphology with average crystallite size of 10µm are presented. The temperature dependence of the magnetic susceptibility, measured in a wide temperature interval (1.5≤T≤400K) using SQUID magnetometer, as well as electron spin resonance (ESR) spectra measured at X-band and Q-band frequency ranges have been studied. Antiferromagnetism with a Néel temperature TN at about 39K was observed from the analysis of evolution of molar magnetic susceptibility and ESR intensity as a function of temperature. ESR parameters namely g-factor, intensity (IESR), g-value, and linewidth ΔH for powder Co3O4 have been obtained. Some deviations from the expected values of some magnetic properties were determined and discussed.

Separation of Contributions from the Ion Core and Free Charge Carriers to the Magnetic Susceptibility of an Anisotropic Semiconductor Bi2Te3–Sb2Te3 Crystal

A technique is presented, by which the magnetic susceptibility χ | of the ion core of an anisotropic semiconductor Bi2Te3–Sb2Te3 crystal is determined from experimental data on the magnetic susceptibility χ ∥ and χ ⊥ obtained with allowance for the orientation of the magnetic field vector H with respect to the trigonal C3 axis of the crystal in accordance with the expression χ ∥/χ ⊥ = (χ ∥ + χ G )/(χ ⊥ + χ G ).In this expression, the value of the magnetic susceptibility of free charge carriers χ ∥ and χ ⊥ depending on their effective masses m ∥ * and m ⊥ * known from the experiment is calculated within the framework of the Pauli and Landau- Peierls approaches. The found value of χ | for Bi2Te3–Sb2Te3 crystals is in good agreement with experimental data, as well as with the estimates obtained in the framework of the Larmor approach explaining, in particular, a linear dependence of the molar magnetic susceptibility on the number of electrons in the molecule observed for a large number of compounds. The proposed technique can be extended to other anisotropic semiconductors.

Silica-supported perchloric acid (HClO4/SiO2) as efficient catalyst for the synthesis of tetraazamacrocyclic complexes of transition metals

Silica-supported perchloric acid (HClO4/SiO2) was used to catalyze the synthesis of tetraazamacrocyclic complexes of Co(II), Ni(II), Cu(II), and Zn(II) from the corresponding metal chlorides, nitrates, or acetates, isatin, and benzene-1,2-diamine in ethanol. The use of HClO4/SiO2 as catalyst allowed the reaction to be performed under stirring at room temperature instead of traditional reflux and completed in two hours. The synthesized complexes were characterized by molar conductance and magnetic susceptibility measurements, IR, electronic, 1H NMR, and mass spectra, and thermogravimetric and X-ray powder analyses. On the basis of these data, six-coordinate octahedral geometry was proposed for all complexes. The synthesized complexes were also tested for antimicrobial activity.