Russian Journal of Inorganic Chemistry最新文献

A critical review of studies on attempts to synthesize FeF₄ molecules and mass spectrometric investigations of the proposed reaction equilibria involving them does not provide a definitive answer regarding the existence of this compound. However, when combined with the results of infrared spectroscopy studies in noble gas matrices and quantum-mechanical calculations, reliable values for the bond dissociation energy (D_{0}^{ circ })(FeF₃ – F) = 195 ± 10 kJ/mol and the standard enthalpy of formation of gaseous iron(IV) fluoride Δ_fH°(FeF₄, 0) = –843 ± 10 kJ/mol can be recommended. A comparison with the thermodynamic characteristics of similar tetrafluorides is provided.

The heat capacity of β-pyrochlore CsTeMoO₆ and CsV_0.625Te_1.375O₆ complex oxide was investigated by adiabatic vacuum calorimetry and differential scanning calorimetry in the temperature range T = 5–500 K. The standard thermodynamic functions (heat capacity (C_{{text{p}}}^{ circ }), enthalpy [H°(T) − H°(0)], absolute entropy [S°(T)], and Gibbs free energy [G°(T) − H°(0)] were calculated for the range from T → 0 to 500 K based on the obtained experimental data. The low-temperature (T < 50 K) heat capacity was analyzed in terms of the multifractal model, and the layered–chain structure topology of the studied compounds was established.

The compound Bi_1.3Yb_0.7O₃ was prepared by solid-phase reactions. The compound had a cubic structure, space group Fm3m, with the unit cell parameter a = 0.54202 nm. The solution enthalpy of Bi_1.3Yb_0.7O₃ as measured by solution calorimetry in 2 M HCl was Δ_solH ⁰ = −227.8 ± 6.3 kJ/mol. The measured enthalpy of solution was used to calculate the standard enthalpy of Bi_1.3Yb_0.7O₃ formation as Δ_fH ⁰ = −996.0 ± 7.9 kJ/mol. The lattice enthalpy for Bi_1.3Yb_0.7O₃ was calculated using the Born–Haber cycle as Δ_latH ⁰ = −13278 kJ/mol.

Cyclic trinuclear silver(I) complex, [AgPz]₃ (Pz = 3,5-bis(trifluoromethyl)pyrazolate), serves as a versatile platform for binding to chelating N^N-donor aromatic ligands. In this work, we have proposed derivatives of pyrazolyl-1H-pyridine (L) as ligands of this type, including 2-(3-phenyl-1H-pyrazol-5-yl)pyridine (L¹) and 2-methyl-6-(3-phenyl-1H-pyrazol-5-yl)pyridine (L²). It has been found that complex of the composition [AgPzL₁] (1 : 1 : 1) forms in solution regardless of reactants stoichiometry. The crystallization of the prepared compounds from toluene results in binuclear complexes with the composition [AgPz₂Ln]₂ per one solvent molecule. The formation of these compounds is caused by hydrogen bonding between the NH groups of pyrazolylpyridines (Lⁿ) and the unshared electron pair of the nitrogen atom of the pyrazolate ligand. Shortened Ag…Ag contacts (3.143–3.197 Å) have been observed in the complex, which leads to additional stabilization of the structure. The prepared compounds exhibit ligand-centered phosphorescence in solid state at ambient temperature.

Hitherto undescribed copper(II) hexamethylenetetramine (HMTA) complexes of tungstophosphate metalates Rb₅[PW₁₁O₃₉Cu(H₂O)]‧9H₂O (I), Rb₅[PW₁₁O₃₉Cu(C₆H₁₂N₄)]‧10H₂O (II), Rb₅[PW₁₁O₃₉Zn_0.95Cu_0.05(H₂O)]‧9H₂O (III), and Rb₅[PW₁₁O₃₉Zn_0.95Cu_0.05(C₆H₁₂N₄)]‧10H₂O (IV) were prepared and characterized by IR and electronic spectroscopies, X-ray powder diffraction, and electron paramagnetic resonance (EPR). The copper-ion absorption peak in the spectrum shifts to the longer wavelengths in going from [Cu(H₂O)₆]²⁺ through [PW₁₁O₃₉Cu(H₂O)]^5– [PW₁₁O₃₉Zn_0.95Cu_0.05(H₂O)]^5–, and [PW₁₁O₃₉Cu(C₆H₁₂N₄)]^5–, to [PW₁₁O₃₉Zn_0.95Cu_0.05(C₆H₁₂N₄)]^5– because of the changing ligand-field strength in the inner sphere of the complex. Electron paramagnetic resonance showed a significant difference between the magnitudes of the ligand field around the octahedrally coordinated Cu²⁺ ions in complexes (III) and (IV): the height of the crystal field potential barrier at the location of the Cu²⁺ ion differs more than twofold due to the replacement of a water molecule by an HMTA molecule C₆H₁₂N₄. The results of the studies can be helpful in the preparation and structure determination of other tungstate polyoxometalates with inner-sphere paramagnetic ions.

New double complex salts [Co(NH₃)₅Cl][Cu(H₂O)(C₂O₄)₂] and [Co(en)₃]₂[Cu(H₂O)(C₂O₄)₂]₂[Cu(H₂O)₂(C₂O₄)₂]·10H₂O (en is ethylenediamine) have been prepared and their thermal properties have been studied. The compounds have been characterized by physicochemical methods of analysis (single crystal and powder X-ray diffraction, IR spectroscopy and elemental analysis). It has been found using thermal analysis and powder X-ray diffraction that decomposition of the complex salts leads to formation of metastable Co_xCu_1–x solid solutions with high mutual solubility of metals. Formation of metastable solid solutions in Co–Cu system has been shown.

New mixed-ligand organometallic frameworks based on zinc terephthalate (bdc), 2‑iodoterephthalate (bdc-I), and 1,4-diazabicyclo[2.2.2]octane (dabco) were obtained: [Zn₂(bdc)_1.67(bdc-I)_0.33dabco] (I), [Zn₂(bdc)_1.46(bdc-I)_0.54dabco] (II), [Zn₂(bdc)_1.12(bdc-I)_0.88dabco] (III), [Zn₂(bdc)_0.80(bdc-I)_1.2dabco] (IV), [Zn₂(bdc)_0.46(bdc-I)_1.54dabco] (V). Their structures and composition were determined by single-crystal and powder X-ray diffraction, as well as elemental analysis. Compounds I–V are isostructural with [Zn₂(bdc)₂(dabco)], but not with [Zn₂(bdc-I)₂(dabco)], which we have not described previously, which is confirmed by X-ray powder diffraction data. Experiments on the sorption of diiodine vapors are consistent with the idea that the presence of a larger amount of 2-iodoterephthalate in the MOF should lead to a decrease in pore volume: the greatest amount of I₂ is absorbed by I, and the smallest by is absorbed V.

New bimetallic complexes of the composition [MHg(C₆H₆N₂O)₂(SCN)₄] have been synthesized, where M = Mn²⁺ (I), Fe²⁺ (II), Cd²⁺ (III) and C₆H₆N₂O is nicotinamide (NA). The compounds were obtained from aqueous solutions and studied by CHNS/O analysis, IR spectroscopy, inductively coupled plasma optical emission spectrometry (ICP-OES), and single-crystal X-ray diffraction. Compounds I–III are isostructural and crystallize in the monoclinic syngony (space group C2/c). The coordination environment of the M²⁺ atom is formed by two donor nitrogen atoms of two monodentately coordinated NA and four nitrogen atoms of the SCN groups, which form bridges between the M²⁺ and Hg²⁺ ions, connecting them into a three-dimensional framework. Hg²⁺ ions have a tetrahedral coordination environment consisting of four S atoms of four SCN groups.

A new method for obtaining K₂Ce(PO₄)₂·xH₂O (space group I4₁/amd, a = b = 6.8300(2) Å, c = 17.8488(4) Å, V = 832.63(4) ų, Z = 4) under hydrothermal conditions has been developed. It has been established that the thermolysis of this compound proceeds through three stages of mass loss with the formation of CePO₄ and K₄P₂O₇ as intermediate products, which upon further heating form a mixture of CePO₄ and K₃Ce(PO₄)₂. The calculated values of the sun protection factor and UV-A protection factor for K₂Ce(PO₄)₂·xH₂O were 2.1 and 2.0, respectively. In relation to the human keratinocyte cell line (HaCaT), a photoprotective effect of K₂Ce(PO₄)₂·xH₂O was recorded. For the first time, the photoactive properties of KCe₂(PO₄)₃ and K₂Ce(PO₄)₂·хH₂O in the decomposition reaction of methylene blue were evaluated. A significant slowdown in the decomposition reaction of an organic dye was demonstrated when using K₂Ce(PO₄)₂·хH₂O.

The paper discusses the results of a study of the structural and thermophysical characteristics of polycrystalline ceramics produced from the InFeZnO₄ nanoparticles. It was found that the bulk density of the resulting material is ~86% of the theoretical one. Scanning electron microscopy has shown that it has a dense microcrystalline structure consisting of randomly oriented grains with dimensions of 5–20 µm. The thermal diffusivity of InFeZnO₄ ceramics was studied using the laser flash method. It was found that as the temperature increases from 299 to 1273 K, it decreases from 1.29 to 0.44 mm²/s. Using adiabatic and differential scanning calorimetry, the temperature dependence of the heat capacity of InFeZnO₄ was studied for the first time. It was established that the measured curve has no signs of the existence of phase transitions in the range from 83 to 923 K. Using experimental data on thermal diffusivity, heat capacity, and density, an equation for the dependence describing the change in thermal conductivity of the material under study in the range from 299 to 1273 K was obtained. It was revealed that ceramics produced from InFeZnO₄ nanoparticles obtained by the polymer-salt method have a higher thermal conductivity compared to those synthesized by standard ceramic technology from a mixture of In₂O₃, Fe₂O₃, and ZnO oxides. The results obtained allow us to recommend InFeZnO₄ as a basis for the creation of thermally stable functional materials with low thermal conductivity at high temperatures.