


Vol 62, No 3 (2017)
- Year: 2017
- Articles: 18
- URL: https://journal-vniispk.ru/0036-0236/issue/view/10221
Synthesis and Properties of Inorganic Compounds
The effect of the synthesis method on the morphological and luminescence characteristics of α-Zn2V2O7
Abstract
A promising yellow phosphor, α-Zn2V2O7, was synthesized at temperatures below the phase transition temperature (610 ± 5°C) by three different methods: solid-phase and microwave processes and thermolysis of a water–salt composition. According to powder X-ray diffraction, the structures of all samples belonged to space group C/2c. Depending on the method of synthesis, the particle size varied from 500 nm (thermolysis of a water–salt composition) to 5–8 μm (ceramic and microwave methods). The excitation spectra of all samples are in the UV region (220–400 nm) and the emission spectra are in the 400–750 nm wavelength range. The photoluminescence spectra of the samples are non-elementary, which is caused by specific features of the electronic charge transfer in the structural VO4 tetrahedra.



Extraction-pyrolytic synthesis and luminescent properties of europium and terbium polytantalates
Abstract
The promise of synthesis of europium and terbium polytantalates MTaxOy, where М = Eu, Tb; x = 7, y = 19; x = 5, y = 14; x = 3, y = 9 by low-temperature extraction-pyrolytic method has been shown. Luminescent properties of the prepared polytantalates have been assessed from excitation and luminescence spectra at 300 K. The dependence of luminescent characteristics of the studied rare earth metal polytantalates on the temperature and time of precursor pyrolysis has been established.



Effect of the degree of doping on the size and magnetic properties of nanocrystals La1 – xZnxFeO3 synthesized by the sol–gel method
Abstract
Nanopowders La1–xZnxFeO3 (nominal degree of doping xnom = 0, 0.05, 0.075, 0.1, 0.15, 0.2, 0.3, and 0.4) were synthesized by the sol–gel method using aqueous ammonia as a precipitator and were then annealed at 950°C for 60 min. From the data of X-ray powder diffraction analysis and local electron probe microanalysis, the maximum actual limit of doping of lanthanum ferrite with zinc was determined: x = 0.072. The dependence of the particle size on the Zn2+ content was found to be nonmonotonic. The magnetic characteristics (specific magnetization J, coercivity Hc, and magnetic susceptibility χ) of samples at temperatures of 300 and 100 K in fields of up to 1300 kA/m. It was shown that, with increasing degree of doping, J increases from 0.188 A m2/kg (at x = 0) to 0.245 A m2/kg (at x = 0.072), and χ varies nonmonotonically from 11.5 × 10–6 (at x = 0) to 15.3 × 10–6 (at x = 0.072) (at 300 K). With decreasing measurement temperature to 100 K, the magnetization and susceptibility monotonically increase.



Coordination Compounds
Cholesteric ester of p-nitrobenzoic acid: Mesomorphic properties, crystal and molecular structures
Abstract
The mesomorphic properties of cholesteric ester of p-nitrobenzoic acid С34Н49NO4 were studied by differential scanning calorimetry and polarizing thermomicroscopy. Its thermal stability was determined using TGA data. The molecular and crystal structures were characterized by single-crystal X-ray diffraction. Crystals were monoclinic, а = 10.7023(4) Å, b = 10.0995(4) Å, с = 14.1563(6) Å, β = 101.499(1)°, space group Р21, Z = 2. An extensive molecule contained three different structural moieties: p-nitrobenzoic acid moiety, a cholesteric core consisting of four conjugated rings of different conformation, and a hydrocarbon chain of six carbon atoms. A molecule was chiral and “left” with a torsion angle of 2.6°.



Tetraphenylantimony aroxides Ph4SbOAr (Ar = C6H4C6H7, C6H2(Br2-2,6)(tert-Bu-4), C6H3(NO2)2-2,4, C6H2(Br2-2,6)(NO2-4)): Synthesis and structure
Abstract
Tetraphenylantimony aroxides Ph4SbOAr, where Ar = C6H4C6H7 (I), C6H2(Br2-2,6)(tert-Bu-4) (II), C6H2(Br2-2,6)(NO2-4) (III), and C6H3(NO2)2-2,4 (IV), have been synthesized by the reaction of pentaphenylantimony with 4-cyclohexadienylphenol, 2,6-dibromo-4-tert-butylphenol, 2,6-dibromo-4-nitrophenol, and 2,4-dinitrophenol. The antimony atoms in molecules of complexes I–IV have a differently distorted trigonal bipyramidal coordination to the oxygen atoms of aroxy groups in axial positions. The OSbС angles are 177.63(13)° (I), 174.29(7)° (II), 177.8(6)° (III), and 174.01(7)° (IV). The Sb–O bond length is 2.117(3) Å (I), 2.2613(15) Å (II), 2.409(11) Å (III), and 2.4296(15) Å (IV).



Cobalt(III) tetrabenzoporphyrin: Synthesis, spectral and coordination properties
Abstract
Comparison of tetrabenzoporphyrin complexation reactions and transmetalation of cadmium(II) tetrabenzoporphyrinate with cobalt(II) acetate and chloride in dimethylformamide (DMF) has been carried out Cobalt(III) tetrabenzoporphyrinate has been prepared and identified. Acido ligands displacement in Co(III) tetrabenzoporphyrinate by pyridine, imidazole, and quinuclidine molecules has been studied.



Theoretical Inorganic Chemistry
Effect of sodium borohydride dihydrate aggregation on the barrier to elimination of hydrogen molecule: Quantum-chemical modeling
Abstract
The successive elimination of Н2 from NaBH4 ∙ 2Н2O, (NaBH4 ∙ 2Н2O)2, (NaBH4 ∙ 2Н2O)4, and (NaBH4 ∙ 2Н2O)4 · Н2O complexes has been modeled in the framework of the cluster approach with the use of the 6-31G* basis set and hybrid density functional (B3LYP). Computations show that combination of NaBH4 ∙ 2Н2O into clusters and addition of one water molecule lead to a decrease in potential barriers to elimination of molecular hydrogen to 0.8–0.9 eV. Transformation of two OH groups of the В(OН)4- anion to give a В=O double bond with elimination of water molecule in the tetramer (NaB(OH)4)4 has been considered.



Topology of subsolidus sections of phase diagrams of quaternary reciprocal systems without solid solutions
Abstract
A problem of constructing subsolidus isobaric–isothermal sections of phase diagrams of quaternary reciprocal systems with constant-composition compounds and limited solid solutions was considered. Relations between the topological characteristics of such sections were derived. Their topological classification was proposed. An algorithm for constructing sections using the theory of finite graphs was developed. A problem of enumerating sections for diagrams with a given set of classification characteristics was solved.



A density-functional theory of hydrogen adsorption on indium nitride nanotubes
Abstract
First-principles calculations based on density functional theory (DFT) are used to study the chemisorption properties of one, two, and four hydrogen atoms on the zigzag and armchair single-walled InN nanotubes (InNNTs).The results indicate that the H atom is strongly bounded to the exterior wall of (4, 4) InNNTs compared with the (7, 0) InNNTs, while the chemisorption energies corresponding to the most stable configuration of H2 dissociation and a single H atom are found to be–3.85 and–3.26 eV, respectively. Furthermore, the effect of the hydrogen storage on the geometries and electronic properties of related InN nanotubes were also discussed. The computed density of states (DOS) indicates that the energy gap of the zigzag and armchair InN nanotubes on hydrogen adsorptions are significantly decreased which can increase the electrical conductance of the tubes. Therefore, InN nanotubes due to the high binding energy can be used for hydrogen storage.



Models of molecular structures of aluminum–iron clusters AlFe3, Al2Fe3, and Al2Fe4 according to quantum-chemical DFT calculations
Abstract
The geometrical parameters of molecular structures of three types of aluminum–iron clusters containing in total four, five, and six Al and Fe atoms in structural units have been calculated by the OPBE/TZVP density functional theory (DFT) method with the Gaussian09 program package. It has been found that the AlFe3, Al2Fe3, and Al2Fe4 clusters can have four, eight, and nine structural modifications, which significantly differ in stability and geometric parameters. Bond lengths and bond and torsion (dihedral) angles are reported for each of these modifications.



The universal relationship between the energy and length of a covalent bond derived from the theory of generalized charges
Abstract
A relationship between the energy and length of a covalent bond is derived from the theory of generalized charges, the asymptotic approximation of quantum mechanics for interatomic forces, which relies upon the model of multicomponent electron gas. The new relationship for the ground state of diatomic molecules is obtained in the form of analytical expressions without empirical coefficients; characteristics of electronic configuration are its parameters. Fairly good agreement between the results of a priori calculations and the experimental data for various molecules is demonstrated.



Physical Methods of Investigation
Binuclear copper(II) complexes based on acyldihydrazones of imino-, oxo-, and thiodiacetic acids and 2-hydroxyacetophenone
Abstract
The results of studying the binuclear copper(II) complexes with acyldihydrazones of amino-, oxo-, and thiodiacetic acids and 2-hydroxyacetophenone were described. The temperature variations of the EPR spectra of solutions with a seven-line hyperfine structure indicating an exchange character of interaction between unpaired electrons and the two equivalent nuclei of copper atoms were studied.



Tetra(hexamethylphosphoric triamide) solvate with ammonium tetrakis(isothiocyanato)diamminechromate(III): Synthesis and crystal structure
Abstract
Ammonium tetrakis(isothiocyanato)diamminechromate(III) crystalline solvate (NH4)[Cr(NH3)2(NCS)4] ∙ 4((CH3)2N)3PO (I) has been synthesized and structurally characterized. Crystals of solvate I are tetragonal, space group P\(\overline{4}\)21c, a = 15.8594(3) Å, c = 11.1675(2) Ǻ, V = 2808.86(9) Ǻ3, Z = 2, ρcalcd = 1.245 g/cm3, ρmeas = 1.21 g/cm3. Cations, solvate molecules, and anions form chains in a crystal by means of intermolecular hydrogen bonds.



Magnetic diagram of CuCr2 – xSbxSе4 solid solutions
Abstract
Temperature-dependent magnetization was measured for CuCr2–xSbxSе4 solid solutions in the range 300–5 K in a weak field (50 Oe) and a strong field (10 kOe) and in an ac magnetic field having a frequency of 100–10000 Hz and an amplitude of Н = 1 Oe. The type and character of magnetic transitions under investigation in the system were determined, and its magnetic phase diagram was constructed.



Synthesis of gold nanoparticles and thin films with the use of micellar solution of Brij 30
Abstract
Gold nanoparticles (NPs) with the average core diameter dAu = 6.8 ± 1.6 nm have been synthesized in reverse micelles of the oxyethylated surfactant Brij 30. It has been shown that thin NP films can be produced directly from a micellar solution with the use of glass substrates functionalized with aminosilane. Synthesis of NPs and film formation have been studied by UV-Vis spectroscopy, photon correlation spectroscopy, X-ray diffraction, TEM, SEM, and AFM.



Preparation of a disperse Fe–Al–Mo system and production of bulk materials on its base
Abstract
We show the feasibility to prepare a disperse Fe–Al–Mo polymetal system by contact exchange in chloride-containing aqueous solutions. Reaction schemes are suggested to describe the processes that proceed on aluminum microparticles in aqueous solutions where the relevant metal ions are contained. The system is shown to be a precursor for intermetallic compounds, which are generated by high-temperature processes, e.g., spark plasma sintering (SPS).



Physicochemical Analysis of Inorganic Systems
Phase equilibria and critical phenomena in the cesium nitrate–water–pyridine ternary system
Abstract
The solubilities of components, phase equilibria, and critical phenomena in the cesium nitrate–water–pyridine ternary system are studied in the 5–100°C temperature range by the visual–polythermal method. Cesium nitrate is found to exhibit a salting-out effect at temperatures above 79.9°C causing phase separation in homogeneous water–pyridine solutions. The temperature of formation of the critical monotectic tie line (79.9°C) and the compositions of solutions corresponding to the liquid–liquid critical points at three temperatures are determined. The pyridine distribution coefficients between the aqueous and organic phases of the monotectic state at 85.0, 90.0, and 100.0°C are calculated. Their values demonstrate that salting-out of pyridine from aqueous solutions by cesium nitrate increases at higher temperatures. The plotted isotherms of phase diagrams confirm the fragment of the scheme of topological transformation of the phase diagrams of salt–binary solvent ternary systems with salting-in and salting-out phenomena.



Study of the NaF–NaBr–Na2SO4 system
Abstract
The NaBr–D (Na3FSO4) quasi-binary system and the NaF–NaBr–Na2SO4 ternary system were studied by differential thermal analysis. The melting points and compositions of eutectic mixtures were determined, and in-, mono-, and divariant equilibrium states were described.


