Heat capacity and thermodynamic functions of ferrocenemethanol

The heat capacity (C _{p, m}) of ferrocenemethanol (FM) C₅H₅FeC₅H₄CH₂OH have been measured by the low-temperature adiabatic calorimetry method in the range 6–371 K. The triple point temperature, the enthalpy of fusion, and the purity of the substance under consideration have been determined. The ideal gas thermodynamic functions of FM—absolute entropy S _m(g) ⁰ and change in the enthalpy Δ ₀ ^T H _m at 298.15 K—have been derived from the heat capacity data and the known values of the saturation vapor pressure and enthalpy of sublimation. The ideal gas thermodynamic functions C _{p, m} ⁰ and S _m(g) ⁰ and the enthalpy of formation of FM have been calculated by the empirical difference method at T = 298.15 K. The experimental and calculated values of the thermodynamic functions are consistent within error limits, which proves their reliability.     

Sm–Sm<Subscript>2</Subscript>Se<Subscript>3</Subscript> phase diagram and properties of phases

A Sm–Sm2Se3 phase diagram has been studied from 1000 K until melting. This system forms three congruently melting compounds: SmSe (ST NaCl, a = 0.6200 nm, T_m = (2400 ± 50) K, and H = 2750 MPa), Sm₃Se₄ (ST Th₃P₄, a = 0.8925 nm, T_m = (2250 ± 30) K, and H = 3350 MPa), and Sm₂Se₃ (ST Th₃P₄, a = 0.8815 nm, T_m = (2150 ± 40) K, and H = 5300 MPa). There are eutectics between Sm and SmSe phases and between SmSe and Sm₃Se₄ phases at 2.5 at % Se, 1300 K and at 54.5 at % Se, 2100 K, respectively. Within the extent of Sm₂₊ Sm₂³⁺ Se4–Sm₂³⁺Se₃ solid solution (ST Th₃P₄), the experimentally determined percentages of Sm₂₊ ions correspond with the values calculated from the formula compositions of samples. The bandgap width for SmSe_1.45 and SmSe_1.48 phases is ΔE = (1.90 ± 0.05) eV.     

Solution Thermodynamics of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis><Superscript>/</Superscript>-Ethylenebis-(salicylideneiminato)-diaquochromium(III) Chloride in Aqueous Dimethylsulphoxide

The densities, viscosities and refractive indices of N,N ^/-ethylene-bis(salicylideneiminato)-diaquochromium(III) chloride, [Cr(salen)(H₂O)₂]Cl, in aqueous dimethylsulfoxide (DMSO) with different mass fractions (w ₂ = 0.20, 0.40, 0.60, 0.80 and 1.00) of DMSO were determined at 298.15, 308.15 and 318.15 K under atmospheric pressure. From measured densities, viscosities and refractive indices the apparent molar volumes (V _φ ), standard partial molar volume (V _φ ⁰ ), the slope (S _V ^* ), standard isobaric partial molar expansibility (φ _E ⁰ ) and its temperature dependence (?φ _E ⁰ /?T) _p , the viscosity B-coefficient, its temperature dependence (?B/?T), solvation number (S _n ) and apparent molar refractivity (R _D ^φ ), etc., were calculated and discussed on the basis of ion–ion and ion–solvent interactions. These results revealed that the solutions are characterized by ion–solvent interactions rather than by ion–ion interactions and the complex behaves as a long range structure maker. Thermodynamics of viscous flow was discussed in terms of transition state theory.     

Concentration,temperature, and isotopy effects on the heat capacity of aqueous urea

Relations for the apparent molar heat capacity ?_c of urea in an aqueous solution depending on the molality m and temperature were obtained. A transition to the relations ?_c(m,T) for D₂O-(ND₂)₂CO and T₂O-(NT₂)₂CO systems was effected by temperature scaling. At low temperatures, the isotherms of the molar heat capacity C _p(m) of the protium and deuterium systems have minima shifted to more dilute solutions at elevated temperatures. At m = 1, C _p of a solution does not depend on temperature in both systems. The dependences C _p(T) also have minima at constant concentrations. The temperature of the minimum heat capacity is most effectively lowered by small additions of urea. For m = 0.25, T _min is 7.5 K lower than T _min of pure water, and its heat capacity is 0.08 J/(mol K) higher. A transition from m = 1.5 to m = 2 lowers the temperature of the minimum heat capacity by 3.6 K; thus, the heat capacity of solutions differs by 0.02 J/(mol K) only.     

Structure of the hexanuclear Cu(II) β-diketonate complex

The structure of the hexanuclear copper(II) β-diketonate complex with gfa (hexafluoroacetylacetone) and dpm (dipivalylmethanate) ligands was studied by low-temperature (T = 100 K) X-ray diffraction. Crystal data for Cu₆(gfa)₄(dpm)₄(OH)₄ [C₆₄H₈₄Cu₆F₂₄O₂₀]: a = 28.2364(7) Å, b = 12.8072(3) Å, c = 24.7199(7) Å, β= 115.900(1)°, V = 8041.5(4) ų, space group C2/m, Z = 4, d _calc 1.661 g/cm³. The coordination polyhedra of the copper atoms — squares and octahedra — are formed by the oxygen atoms of the gfa and dpm ligands and groups. In all cases, the Cu-O distances vary from 1.89 Å to 2.13 Å. The complexes follow the sites of the rhombohedral sublattice with the parameters a _c ≈ 14.4 Å and a _c ≈ 61.5°.     

Thermal polymerization of styrene: New data on the conversion dependence of the initiation rate

With the aid of new acceptors of free radicals usable at high temperatures (T > 100°C), the rate of initiation w _i has been measured experimentally for the thermal polymerization of styrene at 122.5°C in a wide range of conversions C = 0–80%. It has been shown that the value of w _i tends to increase in the course of polymerization transformation in agreement with the w _i = f(C) relationship calculated from the kinetic data on the thermal polymerization of styrene in the absence of counters of free radicals. Hypothetical reasons for this non-trivial tendency have been formulated. The experimental dependence w _i = f(C) has been measured for the first time and has been invoked to refine currently available mathematical models for the thermal polymerization of styrene that assume that w _i remains invariable in the course of polymerization transformation.     

DFT study on oxidation of HS(CH<Subscript>2</Subscript>)<Subscript> <Emphasis Type="Italic">m</Emphasis> </Subscript>SH (<Emphasis Type="Italic">m</Emphasis> = 1–8) in oxidative desulfurization

Density functional theory was employed for calculation of HS(CH₂)_mSH (m = 1–8) and its derivatives at B3LYP method at 6-31++g (d,p) level. Using eigenvalues of LUMO and HOMO for HS(CH₂)_mSH, the standard electrode potentials were estimated by a stepwise multiple regression techniques (MLR), and obtained as E° = 1.500 + 7.167 × 10^–3 HOMO–0.229 LUMO with high correlation coefficients of 0.973 and F values of 43.973.     

The assignment of signals in the EPR spectra of axially symmetrical quintet dinitrenes

Fine structure levels in an external magnetic field and angular dependences of resonance magnetic fields on the direction of an external magnetic field were calculated for two axially symmetrical quintet dinitrenes with the zero-field splitting parameters D _q = 0.260 cm^?1, E _q = 0.000 and D _q = 0.243 cm^?1, E _q = 0.003 cm^?1. The EPR spectra of such dinitrenes contained lines of only three xy transitions (xy ₁, xy ₂, and xy ₄), two Δm _s = ±2 transition lines between the W _?2 and W ₀ sublevels, and three additional lines from noncanonically oriented molecules whose magnetic axis Z made an angle of 12°–16° or 52°–54° with an external magnetic field.     

Kinetics of thermal reaction HOCl ⇄ H(<Superscript>2</Superscript><Emphasis Type="Italic">S</Emphasis>) + OCl(<Emphasis Type="Italic">X</Emphasis><Superscript>2</Superscript>Π<Subscript><Emphasis Type="Italic">i</Emphasis></Subscript>) in gas phase

The kinetics of gas reaction \(HOCl\underset{{k_r }}{\overset{{k_f }}{\longleftrightarrow}}H(^2 S) + OCl(X^2 \Pi _i )\) was analyzed by the MP4 method. In the temperature range of 100–373 K the rate constants k _f and k _r and equilibrium constant K were changed from 1.10 × 10^?220 to 1.17 × 10^?52 s^?1, from 2.89 × 10^?16 to 1.68 × 10^?5s^?1 and from 3.80 × 10^?205 to 6.96 × 10^?48 respectively. In the above temperature range, the activation energy of the forward reaction (E _f) is 105.05 kcal/mol. In the same temperature interval there are two kinetic domains for the reverse reaction with activation energies (E _r1 = 5.53 kcal/mol when T is 100–273 K and E _r2 = 14.50 kcal/mol when T is 273–373 K, respectively.     

Nickel(II) complex with 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane

A nickel(II) complex, [Ni(taetacn)](ClO₄)₂ ? H₂O, where taetacn = 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane was synthesized. The crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. The complex crystallizes in the orthorhombic space group Pna2₁ with a = 16.004(2) Å, b = 10.186(1) Å, c = 13.937(2) Å, V = 2271.9(5) ų, D_x = 1.56 g cm^?3, D_m = 1.59 g cm^?3 (floatation method), and Z = 4. The R₁ [I > 2σ(I)] and wR₂ (all data) values are 0.0636 and 0.1672, respectively, for all 4845 independent reflections. The compound is composed of octahedral nickel(II) cation with three 2-aminoethyl pendant groups of taetacn, tetrahedral ClO ₄ ^? anion, and a water molecule of crystallization. Electronic spectra are consistent with the octahedral geometry. Temperature dependence of the magnetic susceptibility (4.5–300 K) can be interpreted considering the zero-field splitting of the nickel(II) ion (g = 2.14, D = 3.72 cm^?1, and Nα = 300 × 10^?6 cm³ mol^?1). Cyclic voltammetry in DMF showed quasi-reversible and irreversible oxidation waves (E_pa = 0.54 V, E_pc = 0.45 V; E_pa = 1.16 V, E_pc = 0.71 V vs. Ag/Ag⁺).     

Thermodynamic parameters of phase transitions of perfluoro-N-(4-methylcyclohexyl)piperidine

The heat capacity of perfluoro-N-(4-methylcyclohexyl)piperidine (PMCP) was measured by low-temperature adiabatic calorimetry. The purity of the substance (N ₁ = 99.66 mol %), triple point temperature (T _tp = 293.26 K), and enthalpy of fusion (Δ_fus H _m ^° = 8.32 kJ/mol) were determined. The enthalpy of vaporization was measured by calorimetry at 298.15 K (Δ_vap H _m ^° (298.15 K) = 56.56 kJ/mol). The temperature dependence of the saturated vapor pressure of PMCP over the pressure range 6.2–101.6 kPa was determined by comparative ebulliometry. The normal boiling point (T _n.b. = 460.74 K), ehthalpies of vaporization (at various temperatures), and critical parameters of PMCP were calculated. The calculated and experimental values of Δ_vap H _m ^° (298.15 K) agree to within measurement errors, which proves the reliability of these values and pT parameters used in calculations.     

Chromium ion incorporation in the crystal structure of BGO

Comprehensive investigations have been performed by EPR and optical spectroscopy for Bi₃GeO₄ crystals doped with chromium ions. It is demonstrated that the known optical absorption spectrum for chromium ions, specifically, the triplet in the region 600–900 nm has an analog in the EPR spectra — the center with electron spin S = 1. The spectrum is described by the spin-Hamiltonian with the parameters D = 550 G, E = 10 G, g _xx = g _yy = 1.915, g _zz = 1.932. The EPR spectrum is dictated by Cr⁴⁺ incorporation at the germanium sites. Luminescence observed in the region 1.2–1.7 μm is also caused by transitions of Cr⁴⁺ with tetrahedral surroundings to germanium sites. Original Russian Text Copyright ? 2005 N. V. Chernei, V. A. Nadolinnyi, N. V. Ivannikova, V. A. Gusev, I. N. Kupriyanov, V. N. Shlegel, and Ya. V. Vasiliev __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 3, pp. 444–450, May–June, 2005.     

Vapor pressure and heat capacities of perfluoro-<Emphasis Type="Italic">N</Emphasis>-(4-methylcyclohexyl)piperidine

Heat capacities of perfluoro-N-(4-methylcyclohexyl)piperidine (PMCP) have been measured by low-temperature adiabatic calorimetry. The purity of the compound, its triple-point temperature, and its enthalpy and entropy of fusion have been determined. The saturated vapor pressure was determined by comparative ebulliometry as a function of temperature in the 6.2–101.6 kPa pressure range and 374.2–460.9 K temperature range. The calorimetric enthalpy of vaporization at T = 298.15 K has been measured. The following thermodynamic properties were calculated for PMCP: normal boiling temperature, enthalpy of vaporization Δ_vap H _m ⁰ (T) as a function of temperature, and critical parameters. The enthalpies of vaporization at 298.15 K obtained experimentally and by calculation methods match within their error limits, which validates their adequacy and the adequacy of the Δ_vap H _m ⁰ = f(T) equation as an extrapolation.     

Thermoresponsive behavior of water-salt solutions of a graft copolymer with a main polyimide chain and side poly(<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylamino-2-ethyl methacrylate) side chains

The water-salt solutions of the graft copolymer bearing a polyimide main chain and poly(N,N-dimethylamino-2-ethyl methacrylate) side chains (M = 4.7 × 10⁵, the density of grafting with side chains z = 0.44) are studied by static and dynamic light scattering and turbidimetry. The solutions are investigated in a tenfold range of NaCl concentrations (from 0.015 to 0.15 mol/L) at the polymer concentration from 0.002 to 0.015 g/cm³ and pH from 8 to 12. The temperature dependences of the intensity of scattered light, optical transmission, hydrodynamic radius of scattering objects, and their concentrations in solutions are derived. The temperatures of phase separation onset T ₁ and end T ₂ are determined. It is shown that an increase in the salt content in solution leads to reduction in the polymer solubility and in temperatures T ₁ and T ₂. The watersalt solutions retain all the regularities of phase-separation temperature variation observed for aqueous solutions with change in the concentration of solution and pH of a medium: the values of T ₁ and T ₂ increase upon dilution and growth of acidity.     

Electronic Structure and Relative Stabilities of 10- and 12-Vertex. <Emphasis Type="Italic">Closo</Emphasis>and <Emphasis Type="Italic">Nido</Emphasis>-Heteroborane Clusters of Ga,Ge, and As Elements

A DFT method with the B3LYP functional and the 6-311++G(d,p) diffuse basis set is used to predict geometries, relative stabilities, electronic structures, and the bonding of closo- and nido-Ga_mB_n–mH _n ^2? , Ge_mB_n–mH _n ^m?2 , and As_mB_n–mH _n ^{2 m?2} (n = 10, 12 and m = 1, 2) Clusters are obtained by replacing BH with isolobal GaH, GeH⁺, and AsH²⁺ fragments, keeping the same skeleton electron pairs (SEP). Based on the polyhedral skeletal electron pairs theory (PSEPT), closo and nido structures are predicted and can be of significant interest for experimentalists working in the field of heteroboranes. Different cluster stabilities are studied according to Gimarc′s and Williams′ rules, where our calculations show that the monosubstituted clusters deviate from these rules, giving rise to open structures. As₂B₈H _n ²⁺ as 10-vertex structures lead to nido-type clusters, however, Ge_mB_n–mH _n ^m?2 (n = 10, 12 and m = 1, 2) give rise to closo isomers with close energies. All optimized structures exhibit large HOMO–LUMO gaps suggesting a good kinetic stability, thus predicting their isolation and characterization.     

Structure elucidation and X-ray crystallographic study of 3-(naphth-1-ylmethyl)indole

Synthesis and structure determination of 3-(naphth-1-ylmethyl)indole are reported. The molecular and crystal structures together with the molecular formula were determined by spectral and single crystal X-ray studies. X-ray crystallography revealed the presence of two conformers arising from the flipping of the naphthalene unit. The crystal of the compound belongs to the triclinic crystal system and space group \(P\bar 1\). Crystal data are as follows: a = 10.302(5) Å, b = 12.522(4) Å, c = 13.383(4) Å, α = 111.9(1)°, β = 116.86(6)°, γ = 71.65(5)°; V = 1726.429 ų; Z = 4. The final R and Rw are R = 0.0744 (on observed F′s); R = 0.0924 (all F data), R _w = 0.1757 (observed F ²) and R _w = 0.1834 (all F ² data).     

The relation between the potential of zero charge and work function for <Emphasis Type="Italic">sp</Emphasis>-metals

It is shown that for numerous sp-metals there exists no unified work function (W _e) dependence of the potential of zero charge E _{q = 0} and the potential drop characterizing the metal lyophilic behavior Δ _M ^Hg E _chem) _{q = 0}. The reason is that the metal work function is by no means the only factor affecting the value of E _{q = 0}. The quantities E _{q = 0} and (Δ _M ^Hg E _chem) _{q = 0} depend also on the distance of the solvent dipoles’ closest approach to metal surfaces (d _ms) in the absence of the metal-solvent chemisorption interaction. When the metal-solvent chemisorption interaction is involved, this distance affects the degree of overlapping of the metal’s acceptor levels and the upper occupied donor levels in the solvent molecules. To reliably investigate the effect of any of these factors on E _{q = 0}, the other one should be fixed up. It is shown, by example of Ga-, Bi-Gaand Sn-Ga-electrodes, as well as Pb-Ga-, In-Ga-, and Cd-Ga-electrodes demonstrating very close values of the “electrochemical work function” that the metal-solvent chemisorption interaction becomes stronger with the decreasing of d _ms. The influence of this factor is intensified with the increasing of the solvent’s donor number DN. The W _e dependence of E _{q = 0} and (Δ _M ^Hg E _chem) _{q = 0} can be traced by example of metals with nearly equal d _ms values, e.g., Tl-Ga, In-Ga, and Ga. In all studied solvents, the deviation of E _{q = 0} from W _e increased in the series Tl-Ga < In-Ga < Ga, that is, with the increasing of the metal’s work function in vacuum. The effect is intensified with the increasing of the solvent’s DN. The obtained results agree with the concept of donor-acceptor nature of the metal-solvent chemisorption interaction.     

Structure and thermal properties of volatile copper(II) complexes with β-diimine derivatives of acetylacetone and the structure of 2-(methylamino)-4-(methylimino)-pentene-2 crystals

Copper(II) chelates with β-diimine derivatives of acetylacetone that have a general formula of Cu(R¹C(NR²)CHC(NR²)R¹)₂, where R¹, R² are alkyl substituents, are synthesized. The complexes were identified using elemental analysis, melting point measurements, and high-temperature mass spectrometry data. Knudsen technique is employed to determine the vapor pressure temperature dependence, and standard thermodynamic parameters of sublimation ΔH _T ⁰ and ΔS _T ⁰ are derived. A single crystal X-ray diffraction study is carried out for copper(II) complexes of Cu(CH₃-C(NCH₃)-CH-C(NCH³)-CH₃)₂ (a = 10.363(1) Å, b = 11.978(1) Å, c = 12.653(1) Å, V = 1570.6(3) ų, space group Pnc2, Z = 4, d _calc = 1.328 g/cm³, R = 0.027), Cu(CH₃-C(NC₂H₅)-CH-C(NC₂H₅)-CH₃)₂ (a = 11.782(4) Å, b = 13.951(8) Å, c = 25.591(8) Å, V = 4206(3) ų, space group C222¹, Z = 8, d _calc = 1.169 g/cm³, R = 0.10), and also 2-(methylamino)-4-(methylimino)-pentene-2 CH₃-(C=(NCH₃))-CH=(C-(NHCH₃))-CH₃ (a = 12.129(2) Å, b = 12.034(2) Å, c = 5.692(1) Å, β = 107.05(3)°, V = 794.3(3) ų, space group Cc, Z = 4, d _calc = 1.055 g/cm³, R = 0.06). Van der Waals lattice energy E _cryst is calculated for the cooper(II) complexes by the atom-atom potential technique. The calculated values are compared to experimental sublimation enthalpies Δ H _T ⁰ .     

High-temperature heat capacity and thermodynamic properties of pyrovanadate Pb<Subscript>2</Subscript>V<Subscript>2</Subscript>O<Subscript>7</Subscript> and orthovanadate Pb<Subscript>3</Subscript>(VO<Subscript>4</Subscript>)<Subscript>2</Subscript>

The heat capacities of Pb₂V₂O₇ and Pb₃(VO₄)₂ as a function of temperature in the range 350–965 K have been studied by the differential scanning calorimetry method. The C_P = f(T) curve for Pb₂V₂O₇ is described by the equation C_p = (230.76 ± 0.51) + (73.60 ± 0.50)×10^-3T ? (18.38 ± 0.54)×10⁵T^-2 in the entire temperature range. For Pb₃(VO₄)₂, there is a well-pronounced extreme point in the C_P = f(T) curve at T = 371.5 K, which is caused by the existence of a structural phase transition. The thermodynamic properties of the oxide compounds have been calculated.     

Thermodynamic Properties of Zincate-Manganites of LaM<Subscript>2</Subscript> <Superscript>II</Superscript>ZnMnO<Subscript>6</Subscript> (М<Superscript>II</Superscript> = Mg,Ca, Sr,Ba) Composition

Temperature dependences of the heat capacity of new zincate-manganites of LaM₂^IIZnMnO₆ (M^II = Mg, Ca, Sr, Ba) composition are studied via experimental calorimetry in the interval of 298.15–673 K. It is found that all compounds have λ-shape effects on the curve of dependence C_p° ~ ?(T) with respect to phase transitions of the second kind. Equations for the temperature dependence of the heat capacity are derived with allowance for phase transition temperatures, and thermodynamic functions H°(T) ? H°(298.15), S°(T) and Φ^xx(T) are calculated on the basis of experimental data on C_p°(T) and the calculated S°(298.15) value.