Vol 62, No 12 (2017)

Our study deals with the preparation, characterization, and electric conduction properties of complex oxides of formula Bi₁₃Mo_5–xP_xO_34.5–d, which manifest oxygen-ion conductivity at medium-range temperatures.

Three mononuclear and one binuclear dioxomolybdenum(VI) complexes with disubstituted Z-salicylidene-2-furfurylimines (HLⁿ) have been prepared and characterized by IR spectroscopy, namely, MoO₂Cl₂ · 2HLⁿ [Z = 3-MeO-5-Br (n = 5); 3,5-Cl₂ (n = 7); 3,5-Br₂ (n = 8)] and [{MoO₂(L⁵)}₂(μ-O)] (I). The structure of complex I has been determined by X-ray diffraction. Each of the atoms Мо1 and Мо2 has coordination number 5, which is unusual for binuclear complexes of [{MoO₂(L)}₂(μ-O)]. The coordination polyhedron of each of the atoms Мо(1) or Мо(2) may be described either as a heavily distorted trigonal bipyramid (TBP) with two oxo ligands and the atom О(L⁵) in the equatorial plane and the atoms О_br, N(L⁵) in the axial sites, or as an intermediate between a TBP and a square pyramid (SP) (τ = 0.375 for Мо(1) and 0.470 for Мо(2)).

The spectral (UV–Vis, IR, and NMR ¹H) properties and the state of oxorhenium(V) complexes with 5,15-bis(4′-methoxyphenyl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphin H₂P (O=Re(X)P) in protic solvents have been studied depending on the axial trans-ligand X^– (X = Cl, OPh, or OH). The O=Re(Cl)P, O=Re(OPh)P, and O=Re(OH)P in AcOH and CF3COOH are subjected to reaction of substitution their axial ligands with solvent molecules or anions, while remaining stable to the dissociation of M–N bonds and to oxidation both to the macrocyclic ligand and to the central metal cation. Quantitative parameters of the coordination of molecular oxygen by O=Re(Cl)P in 17.4–18.2 M H₂SO₄ to form O=Re(O₂)P⁺ · Cl^– have been obtained, these parameters being independent of the initial H₂SO₄ concentration. The character of peripheral functional substituents in H₂P has been shown to be responsible for the stability of the studied oxo complexes to chemical oxidation in aerated acids.

A new dichloroplatinum(II) complex with 5-methyl-1,10-phenanthroline (1) has been obtained and characterized by X-ray diffraction. MTT assay was used for in vitro cytotoxicity evaluation of this complex, along with a similar complex with 4,7-diphenyl-1,10-phenanthroline (2) against normal and cancerous cell lines. Interestingly, the IC₅₀ values of the new complexes were higher for normal cells and in the case of complex 2, lower against all studied human cancer cells, in comparison with cisplatin.

The thermodynamics of the structural phase transition of H-bonded ferroelectric materials, Pb(H/D)PO₄, were considered in terms of the pseudo-spin Ising model with inclusion of tunneling and longrange effects. The pseudo-spin Hamiltonian parameters needed for analysis of the transition were determined by a procedure based on an independent quantum chemical method. A simplified scheme for the selection of model clusters was proposed, which allows the application of various quantum chemical methods, including high-level methods (CCSD/6-311+G** and so on), in the calculations of double-well potential profiles and Slater parameters. The calculation results were discussed in terms of two statistic models: molecular field approximation (MFA) and Bethe cluster method (BCM). The theoretical estimates of critical transition temperature for both systems are discussed and it is shown that the (semi)quantitative reproduction of experimental data is possible only in terms of BCM taking into account the tunneling effects. The explanation is given for the observed isotope effect caused by very pronounced increase in the critical transition temperature upon deuteration (ΔT_с ≈ 140 K). The crucial role belongs to the difference between tunneling effects in the ferroelectric crystals in question. It is emphasized that the observed differences between the crystal lattice and H/D bond geometries, including the mutual orientation of the bonds, must be accurately included in the calculations.

The geometric parameters of the molecular structures of (454)macrotricyclic M(II) complexes with a tetradentate chelating ligand with the (NSSN)-coordination of donor sites formed by the template reactions in the M(II)–thiosulfate anion S₂O₃^2-–ethylenediamine H₂N–CH₂–CH₂–NH₂ have been calculated by the hybrid OPBE/TZVP density functional theory (DFT) method. The standard enthalpies, standard entropies, and standard Gibbs energies of formation of these complexes have been calculated, and a conclusion has been drawn that the template synthesis in these systems is possible when carrying out appropriate reactions under common conditions (in solution of solid phase).

para-Substituted iron meso-triphenylcorrole derivatives [Fe(ms-p-R-Ph)₃Cor] containing electron- donating (R = OMе) and electron-drawing (R = NO₂) groups in phenyl rings are synthesized and characterized by ¹H NMR, electronic absorption spectroscopy, and mass spectrometry. The effect of the nature of functional groups within iron complexes on the redox processes involving these complexes in water–alkaline solutions is analyzed. Electronic transitions in the ligand (E_red/ox = 0.820–0.850 V) and the metal (E_red/ox =–0.005 to–0.190 and–0.790 to–0.870 V for the Fe⁴⁺ ↔ Fe³⁺ and Fe³⁺ ↔ Fe²⁺ transitions, respectively) were found in the cyclic voltammograms. Iron in the synthesized complexes I–IV under the conditions under study exists in the +4 oxidation state. The activity of iron complexes in electroreduction of molecular oxygen significantly depends on the nature of a substituent, increases in the series: Fe(ms-p-NO₂Ph)₃Cor (II) < Fe(ms-p-MeOPh)₃Cor (I) < Fe(β-Br)₈(ms-Ph)₃Cor (IV) < Fe(ms-Ph)₃Cor (II) and is caused by the fact that low-energy redox electron transitions occur in the molecules. The electrocatalytic activity of iron corroles is much higher than that of metal porphyrins with a similar structure.

The crystal structures of the first prepared EuLnAgS₃ (Ln = Gd and Ho) compounds, which have two polymorphs, were determined by X-ray powder diffraction. α-EuLnAgS₃ phases are isostructural to BaErAgS₃ (monoclinic crystal system, space group C2/m): a = 17.3168(10) Å, b = 3.9683(2) Å, c = 8.3174(4) Å, β = 103.94° (EuGdCuS₃); a = 17.1729(12) Å, b = 3.9367(3) Å, c = 8.2905(6) Å, β = 103.9° (EuHoCuS₃). β-EuLnAgS₃ phases belong to the AgBiS₂ structure type (cubic crystal system, space group Fm-3m): a = 5.739(2) Å (EuGdCuS₃) and a = 5.678 Å (EuHoCuS₃). In the α-EuLnAgS₃ crystal structure, LnS₆ octahedra and AgS₅ trigonal bipyramids share edges to form a three-dimensional (3D) structure with channels accommodating Eu²⁺ ions. A decrease in Ln³⁺ ionic radius gives rise to the crystal-chemical contraction of the 3D structure.

The formation of metastable Cd₃Ge₂As₄ was established using a set of physicochemical analysis methods. The annealing of this compound at temperatures ≥450°C was shown to lead to the formation of the stable binary eutectic Cd₃As₂–СdGeAs₂ and ternary eutectic Cd₃As₂–СdGeAs₂–CdAs₂ with the following composition (at %): Cd, 42.20; Ge, 15.69; As, 42.11; and Cd, 42.70; Ge, 15.06; As, 42.24, respectively.

The PbSb₂Se₄–Pb₅Bi₆Se₁₄ section of the Sb₂Se₃–PbSe–Bi₂Se₃ quasi-ternary system was studied by integrated physicochemical analysis methods, and the state diagram of this section was constructed. The PbSb₂Se₄–Pb₅Bi₆Se₁₄ section was found to be a partially quasi-binary section of the Sb₂Se₃–PbSe–Bi₂Se₃ quasi-ternary system. A region of solid solutions based on PbSb₂Se₄ at room temperature was detected at 10 mol % Pb₅Bi₆Se₁₄. At a ratio between the initial components of 1: 1, congruently melting quaternary compound Pb₆Sb₂Bi₆Se₁₈ forms. Its single crystals were produced by the method of chemical transport reactions. Pb₆Sb₂Bi₆Se₁₈ crystallizes in the rhombic system with the unit cell parameters a = 14.43 Å, b = 21.42 Å, c = 3.90 Å, V⁰ = 1205 ų, Z = 4, and space group Pnnm. The thermodynamic functions of Pb₆Sb₂Bi₆Se₁₈ were calculated: the standard entropy S₂₉₈⁰ = 1472.8 J mol^–1 K^–1, the enthalpy ΔH₂₉₈⁰ =–1215.8 kJ mol^–1, and the Gibbs free energy of formation ΔG₂₉₈⁰ =–1193.6 kJ mol^–1.

Complexes of lithium salts with benzo-15-crown-5 and its derivatives have been prepared. Their structure has been established by X-ray diffraction analysis. On the basis of obtained data, the dependence of partition function ratios for isotopic forms (β factors) of these compounds on the type of extracted salt anion and other factors has been analyzed. Taking into account previously calculated value of β factor for aqua complex of lithium ion, single isotope extraction separation factors (α) for Li⁶–Li⁷ pair have been determined. Quantum chemical calculations for vibrational frequencies of isotope forms of complexes with crown ethers have been performed with the aid of Firefly (PC GAMESS) software. Lithium cation complexes with crown ethers have been calculated using RHF/6-311++G** basis set. Isotope extraction separation factors have been shown to be independent of lithium ion concentration in aqueous phase and the type of extracted salt anion but depend only on the type and size of crown ether ring.