Quantum Chemical Study of Niobium and Tantalum M<Subscript>4</Subscript>O<Subscript>10</Subscript> Oxide Clusters and M<Subscript>4</Subscript>O<Stack><Subscript>10</Subscript><Superscript>–</Superscript></Stack> Anions

Structural parameters and vibrational frequencies of the clusters (T_d)–Nb₄O₁₀, (C_3v)-TaNb₃O₁₀, (D_2d)-Nb₄O ₁₀ ^– , and (C_s)-TaNb₃O ₁₀ ^– were calculated. According to the (U)DFT/SDD calculations with BLYP, B3LYP, and PBE0 functionals magnetization of the anion (D_2d)-Nb₄O ₁₀ ^– is distributed equally among four niobium atoms. In the anion (C_s)-TaNb₃O ₁₀ ^– unpaired electron presumably occupies niobium atoms. The distinction in contributions from Nb atoms in the magnetization of the tantalum-containing cluster grows with the exchange component of the DFT functional in the series of functionals BLYP < B3LYP < PBE0 < UHF.     

Electrical conductivity and ionic association of lithium and sodium perchlorates in tetrahydrofuran

The total limiting molar electrical conductivities of ions and triads of ions and the association constants of ions with the formation of ion pairs and triads of ions were calculated from the concentration dependences of the electrical conductivity of solutions of lithium and sodium perchlorates in tetrahydrofuran at 278.15–318.15 K with the use of the method specially developed earlier. The experimental total limiting electrical conductivities were used to calculate the limiting molar electrical conductivities and attraction friction factors of separate ions (Li⁺, Na⁺, ClO ₄ ^? , Li₂ClO ₄ ⁺ , Na₂ClO ₄ ⁺ , Li(ClO₄) ₂ ^? , and Na(ClO₄) ₂ ^? ). The constants of ion association into ion pairs were used to calculate the Gibbs energy of non-Coulomb interionic interaction (ΔG*_+?), and the constants of association into triads of ions, to determine the a ₃ distance parameter between the centers of the ion and the dipole of the ion pair. Positive ΔG*_+?), values and deviations of the experimental a ₃ value from the distance parameter calculated theoretically (a ₃ ⁰ ) for the triad of ions (Δa ₃ = a ₃ ? a ₃ ⁰ ) were related to non-Coulomb repulsion in the region of overlap of the solvation shells of ions and the influence of temperature and ion charge density on this repulsion.     

Molecular and ionic sublimation of neodymium tribromide polycrystals and single crystals

The molecular and ionic sublimation of polycrystals and single crystals under Knudsen effusion and Langmuir evaporation conditions is reported. In both sublimation regimes, the sublimation product at 780–1050 K contains neodymium tribromide monomer and dimer molecules, as well as the negative ions NdBr ₄ ^? , Nd₂Br ₇ ^? , and Br^?. The dimer-to-monomer flux ratio j(Nd₂Br₆)/j(NdBr₃)is larger in the molecular beam coming out of the effusion hole, while the ratio of the sublimation fluxes of the negative ions, j(Nd₂Br ₇ ^? )/j(NdBr ₄ ^? ), is independent of the sublimation conditions. The partial pressures of the neutral components of the vapor have been determined, and the enthalpies and activation energies of sublimation of neodymium tribromide as monomer and dimer molecules and NdBr ₄ ^? and Nd₂Br ₇ ^? ions have been calculated. The equilibrium constants of ion-molecule reactions have been measured, and the enthalpies of these reactions have been determined. Based on these data, values of the thermodynamic properties Δ _s H ⁰(298.15) and Δ _f H ⁰(298.15) are recommended for the monomer and dimer molecules and the NdBr ₄ ^? and Nd₂Br ₇ ^? ions.     

Theoretical study of oxoborate complexes with MO<Stack><Subscript>4</Subscript><Superscript><Emphasis Type="Italic">n</Emphasis>−</Superscript></Stack> tetraoxo anions in the inner and outer spheres of the B<Subscript>20</Subscript>O<Subscript>30</Subscript> cluster

The energies and structural and spectroscopic characteristics of endohedral (MO₄©B₂₀O ₃₀ ^n? ) and exohedral (MO₄ · B₂₀O ₃₀ ^n? ) isomers of oxoborate complexes with MO ₄ ^n? tetraoxo anions with 32 valence electrons located in the inner and outer spheres of the B₂₀O₃₀ cluster have been calculated by the density functional theory method (B3LYP). It has been demonstrated that, among the endohedral MO₄©B₂₀O ₃₀ ^n? clusters with strong multiply charged anions (VO ₄ ^3? , CrO ₄ ^2? , PO ₄ ^3? , SO ₄ ^2? , AsO ₄ ^3? , SeO ₄ ^2? , etc.), the isomer in which a “guest” tetrahedron MO₄ is located at the center of the B₂₀O₃₀ cage and bonded to it through internal oxygen bridges M-O*-B is the most favorable one. Among the exohedral analogues MO₄ · B₂₀O ₃₀ ^n? , two most favorable isomers contain the “capping” MO₄ tetrahedron bonded to the B₂₀O₃₀ cage through two and three external M-O-B bridges. For the complexes with doubly charged SO ₄ ^2? and SeO ₄ ^2? anions, the third exohedral isomer in which the sulfite or selenite group MO₃ is bidentately coordinated to the oxidized B₂₀O₂₉(OO) cage with one peroxide bridge turns out to be close in energy to the above two isomers. For the systems with high negative charge n, the exohedral isomers are much more favorable than the endohedral isomer; however, with decreasing charge, the difference in energy between them decreases to ~10–18 kcal/mol, so that the exo–endo transition between them can require moderate energy inputs. For the endohedral complexes with singly charged ClO ₄ ^? and BrO ₄ ^? anions, two isomers with close energies are preferable in which the central atoms of the guest tetrahedra are reduced to the state of singly charged ions, while the oxoborate cage is oxidized to B₂₀O₂₆(OO)₄ with four peroxide groups B-O-O-B and retains its closed (closo) structure. In the most favorable isomer of the complexes with multicharged ortho-anions BO ₄ ^5? , CO ₄ ^4? , and NO ₄ ^3? , the outersphere anion is reduced to, respectively, borate, carbonate, and nitrate bidentately coordinated to the oxidized B₂₀O₂₉(O)₂ cage with an open structure and two strongly elongated terminal B-O bonds. The results are compared with the data of previous calculations of endohedral and exohedral vanadate complexes MO₄©V₂₀O ₅₀ ^n? and MO₄ · V₂₀O ₅₀ ^n? with the same guest anions MO ₄ ^n? .     

Reduction kinetics of glycinate complexes of palladium(II) on a dropping-mercury electrode in acid perchlorate solutions

Polarograms for the reduction of glycinate complexes of palladium(II) (5 × 10^?5 M) are obtained in equilibrium solutions of pH 0.8–3.0 with different protonated-glycine concentrations c _Hgly (supporting electrolyte, 0.5 M NaClO₄). It is established that the irreversible wave of reduction of complexes Pd(gly)₂ corresponds to the diffusion limiting current I _d ⁽²⁾ . A similar wave at pH 1.5 and c _Hgly = 0.005 M, as well as at pH 1.0 and c _Hgly = 0.05–0.5 M is preceded by the diffusion limiting current I _d ⁽¹⁾ . Values of the I _d ⁽²⁾ /I _d ⁽¹⁾ ratio are close to the ratio between equilibrium concentrations of Pd(gly)₂] and [Pdgly⁺], calculated using the step stability constant for Pd(gly)₂. This fact testifies to the reduction of complexes Pdgly⁺ in the vicinity of I _d ⁽¹⁾ and complexes Pd(gly)₂, in the vicinity of I _d ⁽²⁾ . At pH 0.8–1.2 and [H₂gly⁺] = 1 × 10^?4 to 5 × 10^?3 there is observed the diffusion-kinetic limiting current of the first wave I ₁ ⁽¹⁾ , which increases with increasing [H⁺] and decreasing [H₂gly⁺]. The nature of the slow preceding chemical stage that occurs during the reduction of complexes Pdgly⁺ is discussed.     

Synthesis and crystal structure of dibenzo-18-crown-6 oxonium perchlorate

An ionized crystalline adduct of dibenzo-18-crown-6, perchloric acid, and water (H₃O)[DB 18K6](ClO₄) is synthesized and structurally studied by X-ray diffraction. The crystals are triclinic: a = 8.582 Å, b = 10.486 Å, c = 26.293 Å, α = 79.45°, β = 82.00°, γ = 79.36°, Z = 4, space group P \(\bar 1\). The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.098 for 5936 independent reflections (CAD4 automated diffractometer, λMoK _α radiation). The structure contains two independent DB18C6 molecules, two independent H₃O⁺ ions, and two independent ClO ₄ ^? ions. The H₃O⁺ ions each lie in the cavity of each of the two DB18C6 molecules and are retained there by three strong hydrogen bonds. Two DB18C6 molecules have close geometric parameters and a butterfly conformation with approximate symmetry C _2v . One of the two independent ClO ₄ ^? anions is disordered over two orientations.     

The thermodynamic characteristics of vaporization in the NaI-PrI<Subscript>3</Subscript> system

The vaporization of the NaI-PrI₃ quasi-binary system was studied by high-temperature mass spectrometry over the whole concentration range. At 623–994 K, saturated vapor contained not only (NaI) _n and (PrI₃) _n molecules (n = 1, 2) and Na⁺(NaI) _n (n = 0–4) and I^?(PrI₃) _n (n = 1–2) ions but also mixed molecular and ionic associates recorded for the first time (NaPrI₄, Na₂PrI₅, NaPrI ₃ ⁺ , Na₂PrI ₄ ⁺ , Na₃PrI ₅ ⁺ , Na₄PrI ₆ ⁺ , NaPrI ₅ ^? , and NaPr₂I ₈ ^? ). The partial vapor pressures of molecules were calculated, and the equilibrium constants of the dissociation of neutral and charged associates were measured. The enthalpies of molecular and ion-molecular reactions were determined, and the enthalpies of formation of gaseous molecules and ions were obtained.     

X-ray photoelectron spectroscopic study of the interaction of supported metal catalysts with NO<Subscript>x</Subscript>

The reactions of the platinum and rhodium model catalysts applied to aluminum oxide with NO_x (10 Torr NO + 10 Torr O₂) were studied by X-ray photoelectron spectroscopy. The reaction conducted at room temperature formed on the surface of the oxide support the NO _3,s ^? nitrate ions characterized by the N1s line at 407.4 eV and O1s line at 533.1 eV and the NO _2,s ^? nitrite ions characterized by the N1s line with a binding energy of 404.7 eV. At the same time, the Pt4f and Rh3d lines of the supported platinum particles are shifted toward higher binding energies by 0.5–1.0 eV and 0.7–1.2 eV, respectively. It is assumed that the binding energies increase due to changes in the chemical state of the platinum metal in which oxygen is dissolved. The reaction of NO_x with Pt/Al₂O₃ at 200°C forms platinum oxide defined by the Pt4f _7/2 line with a binding energy of 72.3 eV.     

Investigation of Chloride Ion Substitution Equilibria in AuCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> with Ethylenediamine and 1,3-Diaminopropane Using Capillary Zone Electrophoresis

Substitution of chloride ions in AuCl ₄ ^? with ethylenediamine (en) and propylenediamine (tn) is studied by capillary zone electrophoresis at I = 0.05 M and T = 25°C. The substitution constants are determined: AuenCl ₂ ⁺ + en = Auen ₂ ³⁺ + 2Cl^–, logK₂ = 10.4; AuCl ₄ ^? + tn = AutnCl ₂ ⁺ + 2Cl^–, logK₁ = 16.1; AutnCl ₂ ⁺ + tn = Autn³⁺₂ + 2Cl^–, logK₂ = 12.0.     

Crystal structure of Ba<Subscript>3</Subscript>[UO<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>(NCS)]<Subscript>2</Subscript> · 9H<Subscript>2</Subscript>O

Single crystals of Ba₃[UO₂(C₂O₄)₂(NCS)]₂ · 9H₂O are synthesized and studied by X-ray diffraction. The crystals are orthorhombic, space group Fddd, Z = 16, and the unit cell parameters are a = 16.253(3) Å, b = 22.245(3) Å, c = 39.031(6) Å. The main crystal structural units are mononuclear complex groups [UO₂(C₂O₄)₂NCS]^3? of the crystal-chemical family (AB ₂ ⁰¹ M¹ (A = UO ₂ ²⁺ , B⁰¹ = C₂O ₄ ^2? , M¹ = NCS^?) of the uranyl complexes linked into a three-dimensional framework by electrostatic interactions and hydrogen bonds involving oxalate ions and water molecules.     

Synthesis and crystal structure of Rb<Subscript>2</Subscript>[(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)] · 1.33H<Subscript>2</Subscript>O

The single crystals of Rb₂[(UO₂)₂(C₂O₄)₂(SeO₄)] · 1.33H₂O were synthesized and studied by X-ray diffraction. The crystals are monoclinic, space group P2₁/m, Z= 2, the unit cell parameters: a = 5.6537(8), b = 18.736(3), c = 9.4535(15) Å, β = 98.440(5)°, V = 990.6(3) ų, R ₁ = 0.0506. The main structural units of the crystal are infinite layers of [(UO₂)₂(C₂O₄)₂(SeO₄)]^2?, corresponding to the crystal chemical group A₂K ₂ ⁰² B² (A = UO ₂ ²⁺ , K⁰² = C₂O ₄ ^2? , B² = SeO ₄ ^2? ) of uranyl complexes. The uranium-containing layers are united into a three-dimensional framework through the electrostatic interactions with the outer-sphere rubidium ions and the hydrogen bonding system involving the outer-sphere water molecules.     

Calculation of the thermodynamic characteristics of ions in vapor over sodium fluoride

The geometric parameters, normal vibration frequencies, and thermochemical characteristics of the ions present in vapor over sodium fluoride, Na₂F⁺, Na₃F ₂ ⁺ , NaF ₂ ^? , and Na₂F ₃ ^? , were calculated ab initio by the Hartree-Fock method and taking into account electron correlation. The main equilibrium configuration of all ions was found to be the linear configuration of D _∞h symmetry. Pentaatomic ions could also exist as two isomers, planar cyclic of C _2v symmetry and bipyramidal of D _3h symmetry. Their energies were higher than that of the D _∞h isomers, and their contents in vapor were negligibly low. The energies and enthalpies of dissociation of the ions with the elimination of the NaF molecule were calculated. The enthalpies of formation of the ions were obtained.     

Structure and Magnetic Properties of a New Lattice System of the Heterometallic Decanuclear Ce<Subscript>6</Subscript>Mn<Subscript>4</Subscript> Aggregate

In this paper, we present a mixed valence f–d Ce₆Mn ₄ ^III compound having formula [Ce ₆ ^IV Mn ₄ ^III (μ₄-O)₄ (μ₃-O)₄(O₂C^tBu)₁₂(ea)₄(OAc)₄]·H₂O (1), which is obtained by the reaction of hydrated lanthanide nitrate, pivalic acid, and ethanolamine in MeCN as a solvent. The single crystal X-ray diffraction analysis demonstrates that the central core consists of an octahedron with four triangular pyramids added to four related faces or as an octahedron encapsulated in a tetragon. The fitting of magnetization data using the anisotropic model gives D = 2.13 cm^–1 and g = 1.97 (D is the axial zero-field splitting parameter).     

The synthesis and thermodynamic properties of strontium fluoromanganite Sr<Subscript>2.5</Subscript>Mn<Subscript>6</Subscript>O<Subscript>12.5 − δ</Subscript>F<Subscript>2</Subscript>

The existence of the [SrF_0.8O_0.1]_2.5[Mn₆O₁₂] = Sr_2.5Mn₆O_{12.5 ? δ}F₂ compound was established in the SrO-Mn₂O₃-SrF₂ system at 900°C and p(O₂) = 1 atm. The crystal structure of strontium fluoromanganite was determined from the X-ray powder diffraction data, electron diffraction, and high-resolution electron microscopy. It can be described in the monoclynic system with four Miller hklm indices: hklm: H = h a* + k b* + l c ₁ ^* + m q ₁, q ₁, q ₁ = c ₂ ^* = γc ₁ ^* , γ ≈ 0.632, a ≈ a ≈ 9.72 Å, b ≈ 9.55 Å, c ₁ ≈ 2.84 Å, c ₂ ≈ 4.49 Å, monoclinic angle γ ≈ 95.6°. The electromotive force method with a solid fluorine ion electrolyte was used to refine the composition of fluoromanganite and determine the thermodynamic functions of its formation from phases neighboring in the phase diagram (SrMn₃O₆, Mn₂O₃, SrF₂, and oxygen), ΔG°, kJ/mol = ?(111.7 ± 1.9) + (89.5 ± 1.5) × 10^?3 T.     

Nucleophilic activity of peroxyhydrocarbonate and peroxocarbonate ions relative to 4-nitrophenyl diethyl phosphonate

Peroxocarbonate ions HCO ₄ ^? and CO ₄ ^2? , which are formed in the H₂O₂/NH₄HCO₃/HO^? system, react with 4-nitrophenyl diethyl phosphonate (I) through a nucleophilic mechanism with rate constants \(k_{HCO_4^ - } = 0.008\) and \(k_{CO_4^{2 - } } = 0.13 L/mol \cdot s\). Comparison of these constants with the corresponding constants of other inorganic anions in their reaction with I in the framework of the Brönsted equation indicates that HCO ₄ ^? and CO ₄ ^2? are typical α-nucleophiles.     

Stability of diammine and chloroammine gold(I) complexes in aqueous solution

The substitution equilibria AuCl ₂ ^? + iNH ₄ ⁺ = Au(NH₃)_iCl_{2 ? i} + iCl^? + iH⁺, β _i ^* . were studied pH-metrically at 25°C and I = 1 mol/L (NaCl) in aqueous solution. It was found that logβ ₁ ^* = ?5.10±0.15 and logβ ₂ ^* = ?10.25±0.10. For equilibrium AuNH₃Cl_solid = AuNH₃Cl, log K _s = ?3.1±0.3. Taking into account the protonation constants of ammonia (log K _H = 9.40), the obtained results show that for equilibria AuCl ₂ ^? + iNH₃ = Au(NH₃)_iCl_{2 ? i} + iCl^?, logβ₁ = 4.3±0.2, and logβ₂ = 8.55±0.15. The standard potentials E ₀ ^1/0 of AuNH₃Cl⁰ and Au(NH₃) ₂ ⁺ species are equal to 0.90±0.02 and 0.64±0.01 V, respectively.     

New method for calculating the moments of thermally averaged densities of distribution of internuclear distances in polyatomic molecules using the Bloch integral equation

A convenient method is suggested for calculating thermally averaged powers of the normal vibrational coordinates Q _i by iteratively solving the Bloch integral equation with an anharmonic function of potential energy using multidimensional Hermite polynomials. Analytical formulas of the first approximation regarding anharmonicity constant have been obtained for the following moments of thermally averaged density: 〈Q ₁〉, 〈 Q ₁ ² 〉, 〈Q ₁ Q ₂〉, 〈Q ₁ ³ 〉 〈Q ₁ ³ 〉, 〈Q ₁ Q ₂ Q ₃〉, 〈Q ₁ ⁴ 〉, 〈Q ₁ ² Q ₂ ² 〉, 〈Q ₁ Q _2/3〉, 〈Q ₁ Q ₂ Q ₃ ² 〉, 〈 Q 1 Q ₂ Q ₃ Q ₄〉.     

Crystal structure of magnesio-ferri-hornblendite □Ca<Subscript>2</Subscript>(Mg<Subscript>4</Subscript>Fe<Superscript>3+</Superscript>)[(Si<Subscript>7</Subscript>Al)O<Subscript>22</Subscript>](OH)<Subscript>2</Subscript> as a potentially new mineral of the amphibole supergroup

A sample of magnesio-ferri-hornblendite, a potential new mineral of the amphibole supergroup, was studied by X-ray diffraction and IR spectroscopy. The crystal chemical formula is (Z = 2): ^AK_0.04^M(4) (Ca_1.92Na_0.08) ^C[^M(1)(Mg_1.78Fe_0.22⁴⁺) ^M(2)(Mg_1.62Fe_0.26³⁺Al_0.12) ^M(3)(Mg_0.64Fe_0.32²⁺Mn_0.04)] [^T(Si_7.44Al_0.56)O₂₂] ^W(OH)₂. The monoclinic unit cell parameters are a = 9.855(1) Å, b = 18.084(1) Å, c = 5.289(1) Å, β = 104.853(2)°; V = 911.1(2) ų; space group C2/m; Z = 2. The crystal structure was refined to R = 2.82% in the anisotropic approximation for atomic displacement parameters using 1166 reflections with I > 2σ(I). The magnesio-ferri-hornblendite structure is generally similar to the structures of other monoclinic calcium amphiboles, and its key distinctive features are the predominance of Мg among C²⁺ cations and Fe³⁺ among C³⁺ cations.     

Structure of the Oxonium Compound of Pefloxacinium Hexachloridostannate(IV)

The structure of tris{hexachloridostannate(IV)}-hexachloride-tetrakis(pefloxacinium)-tetraoxonium undecahydrate (CCDC 1551760) 4PefH ₃ ²⁺ , 4H₃O⁺, 3SnCl ₆ ^2? , 6Cl^?, 11H₂O (I), (PefH is pefloxacin) is determined. The I crystals are triclinic: a = 13.5474(10) Å, b = 15.2859(11) Å, c = 15.6586(11) Å, α = 94.467(1)°, β = 105.477(1)°, γ = 111.560(1)°, V = 2849.9(4) ų, space group Pī, Z = 1. The structure is stabilized by multiple intermolecular hydrogen bonds and π–π-interactions between the PefH₃²⁺ ions.