K. V. Zherikova

Thermochemistry of Dihalogen-Substituted Benzenes: Data Evaluation Using Experimental and Quantum Chemical Methods

Temperature dependence of vapor pressures for 12 dihalogen-substituted benzenes (halogen = F, Cl, Br, I) was studied by the transpiration method, and molar vaporization or sublimation enthalpies were derived. These data together with results available in the literature were collected and checked for internal consistency using structure-property correlations. Gas-phase enthalpies of formation of dihalogen-substituted benzenes were calculated by using quantum-chemical methods. Evaluated vaporization enthalpies in combination with gas-phase enthalpies of formation were used for estimation liquid-phase enthalpies of formation of dihalogen-substituted benzenes. Pairwise interactions of halogens on the benzene ring were derived and used for development of simple group additivity procedures for estimation of vaporization enthalpies, gas-phase, and liquid-phase enthalpies of formation of dihalogen-substituted benzenes.

Benzoic Acid and Chlorobenzoic Acids: Thermodynamic Study of the Pure Compounds and Binary Mixtures With Water

Benzoic acid is a model compound for drug substances in pharmaceutical research. Process design requires information about thermodynamic phase behavior of benzoic acid and its mixtures with water and organic solvents. This work addresses phase equilibria that determine stability and solubility. In this work, Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was used to model the phase behavior of aqueous and organic solutions containing benzoic acid and chlorobenzoic acids. Absolute vapor pressures of benzoic acid and 2-, 3-, and 4-chlorobenzoic acid from literature and from our own measurements were used to determine pure-component PC-SAFT parameters. Two binary interaction parameters between water and/or benzoic acid were used to model vapor-liquid and liquid-liquid equilibria of water and/or benzoic acid between 280 and 413 K. The PC-SAFT parameters and 1 binary interaction parameter were used to model aqueous solubility of the chlorobenzoic acids. Additionally, solubility of benzoic acid in organic solvents was predicted without using binary parameters. All results showed that pure-component parameters for benzoic acid and for the chlorobenzoic acids allowed for satisfying modeling phase equilibria. The modeling approach established in this work is a further step to screen solubility and to predict the whole phase region of mixtures containing pharmaceuticals.

Chemical vapor deposition of electrolyte thin films based on yttria-stabilized zirconia

Gas-tight electrolyte films are obtained by chemical vapor deposition for solid oxide fuel cells from yttria-stabilized zirconia (YSZ) with a thickness of 4–15 μm on supporting porous ceramic anodes (YSZ/NiO). Volatile metal complexes with dipivaloylmethane Zr(dpm)4 and Y(dpm)3 are used as precursors. On the basis of an analysis of thermal properties of the starting compounds, parameter ranges in deposition processes are determined. Dependences of the structure, composition, and electrical characteristics on deposition conditions are found for YSZ electrolyte films. Electrochemical solid oxide fuel cells that operate at low temperatures with an open circuit voltage of 0.98–1.08 V and specific power up to 440 mW/cm2 at 1073 K and 1200 mW/cm2 at 1173 K are constructed.

Synthesis, structure, and thermal properties of fluorinated cesium beta-diketonates

Four fluorinated cesium beta-diketonates, Cs(CF3COCHCOCF3) (Cs(hfac)), Cs(CF3COCHCOCH3) (Cs(tfac)), Cs(OH2)((Me)3CCOCHCOCF3) (Cs(OH2)(ptac)), and Cs(OH2)(PhCOCHCOCF3) (Cs(OH2)(btfac)), were synthesized by interaction of the corresponding beta-diketone and Cs2CO3 in Et2O. The formation of Сs(CF3C(OH)2CH2C(OH)2CF3)(CF3COO) or Cs(CF3C(OH)2CH2COCH3)(tfac) was shown to be dependent on the reaction conditions. The compounds were characterized by elemental analysis, single crystal X-ray diffraction, and TG/DTA analysis. All compounds have ionic structures organized into pseudo chains (in the case of Cs(hfac) and Cs(CF3C(OH)2CH2COCH3)(tfac)) or pseudo layers (in other cases). According to the TG data Cs(hfac), Cs(tfac), Cs(OH2)(ptac,) and Cs(OH2)(btfac) decompose in inert atmosphere within the temperature range 30–550 °C.

Thermal properties of volatile ruthenium(III) complexes

Complexes of ruthenium(III) with the following beta-diketone derivatives: 2,4-pentanedione (Ru(acac)3), 1,1,1,6,6,6-hexafluoro-2,4-pentanedione (Ru(hfac)3), and 2-methoxy-2,6-dimethyl-3,5-heptanedione (Ru(mdhd)3) were synthesized, purified, and identified by chemical analysis and melting points. By difference-scanning calorimetry (DSC) in vacuum the thermodynamic characteristics of melting processes were defined. Using the static method with quartz membrane zero-manometer, the temperature dependencies of saturated and unsaturated vapor pressure were obtained for Ru(hfac)3. The standard thermodynamic characteristics of vaporization processes enthalpy ∆HT* and entropy ∆S°T* were determined.

Novel N-Containing Precursors of Nickel(II) for Film Deposition by MOCVD

The synthesis of volatile nickel(II) complexes with Ncontaining ligands like R(O,N)C(CH3)CH2C(CH3)NR (R – H, radical group) was carried out in inert atmosphere. The substances were characterized by means of elemental analysis, IRand NMR-spectroscopy, melting point, mass spectrometry. The thermal behavior of the compounds in the solid state was investigated by the method of thermogravimetry and difference-scanning calorimetry (DSC) in vacuum and helium. The thermodynamic characteristics of the melting processes (m.p., ∆meltHm.p., ∆meltSm.p.) were also determined by DSC: m.p. 157.5 ± 2 and 247.2 ± 1,2oC, ∆meltHm.p. = 25 ± 2 and 41,7 ± 0,3 kDj/mol, ∆meltSm.p. = 58 ± 5 and 80,1 ± 1,2 Dj/mol K for Ni(N(Me)C(CH3)CHC(CH3)N(Me))2 and Ni(OC(CH3)CHC(CH3)NH)2 respectively. Using the Knudsen method with mass spectrometric registration of gas phase and static method with quartz zero-manometer the temperature dependences of saturated vapor pressure of complexes were studied, the standard thermodynamic parameters of enthalpy and entropy of sublimation process were determined (Fig.1). The standard thermodynamic parameters of ones of evaporation process were calculated from data on sublimation and melting processes. It was shown that complex with ketoamine ligand is more thermodynamically stable in solid state than diimine analogue whereas the last one is more volatile that O-containing compound. By means of in situ high temperature mass spectrometry the thermodecomposition process of Ni(N(Me)C(CH3)CHC(CH3)N(Me))2 vapor was studied in vacuum temperature range of destruction and gas byproducts were determined (Fig.2). At temperatures 130– 250oC the first step of decrease of ion current intensity for metal-containing ion is observed that is apparently connected with forming of oligomers on surface being accompanied by isolation of 2-methylamino-4methylimino-2-pentene to gas phase. The decomposition of just formed on surface structures is hypothetically beginning at temperatures upper 250oC and is accompanied by isolation of products pointed on Fig.2. to gas phase. On account of the analysis of temperature behavior of reaction products the scheme of mechanism of chemical transformation on heated surface was proposed. The complexes have been used as precursors for the Ni-containing film formation by Metal-Organic Chemical Vapor Deposition. The film decomposition conditions were chosen on the base of information about thermal behavior of complexes. The experiments were carried out in hydrogen at substrate temperature 320– 370oC. The films obtained were investigated by using different methods: SEM, XRD etc. 1,9 2,0 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8 2,9 -3,5 -3,0 -2,5 -2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0

Structure-property relationships in halogenbenzoic acids: Thermodynamics of sublimation, fusion, vaporization and solubility.

Temperature dependences of vapor pressures for 2-, 3-, and 4-bromobenzoic acid, as well as for five isomeric bromo-methylbenzoic acids were studied by the transpiration method. Melting temperatures and enthalpies of fusion for all isomeric bromo-methylbenzoic acids and 4-bromobenzoic acid were measured with a DSC. The molar enthalpies of sublimation and vaporization were derived. These data together with results available in the literature were collected and checked for internal consistency using a group-additivity procedure and results from X-ray structural diffraction studies. Specific (hydrogen bonding) interactions in the liquid and in the crystal phase of halogenbenzoic acids were quantified based on experimental values of vaporization and sublimation enthalpies. Structure-property correlations of solubilities of halogenobenzoic acids with sublimation pressures and sublimation enthalpies were developed and solubilities of bromo-benzoic acids were estimated. These new results resolve much of the ambiguity in the available thermochemical and solubility data on bromobenzoic acids. The approach based on structure property correlations can be applied for the assessment of water solubility of sparingly soluble drugs.

Thermal Properties of Some Volatile Titanium (IV) Precursors

The tensimetric study was carried out for TTIP, Ti[OEt]4 and Ti[DMAP]4 by means of static method with a quartz membrane zero-manometer and flow method using He as gas-carrier (the compounds were assumed to vaporize in a monomolecular form) in a wide range of temperatures. Temperature dependencies of saturated vapor pressure were measured; the evaporation thermodynamic parameters have been calculated (Table 1). Data obtained for TTIP can be compared with values calculated from literature data [1, 2].

Crystal structures of hafnium(IV) and zirconium(IV) complexes with β-diketones

Preparation methods are developed for a number of 7- and 8-coordinated derivatives of Hf(IV) and Zr(IV) with β-diketonate ligands (R1-CO-CH-CO-R2). The complexes obtained are examined by IR spectroscopy, mass spectrometry, and X-ray crystallography. All structures are molecular. The M-O distances fall within 2.09–2.28 Å. In the crystals, the molecules are joined only by van der Waals interactions. It is demonstrated that the series of hafnium(IV) and zirconium(IV) chelates with identical ligands are isostructural, and the introduction of CF3- or tert-butyl groups in the terminal positions of the ligand as well as chlorine substitution for one of the ligands do not essentially affect the basic geometric characteristics of the ligand in the complexes.

Crystal structures of tris-hexafluoro-acetylacetonates of aluminum and scandium

The structures of tris-hexafluoroacetylacetonates Al(hfa)3 and Sc(hfa)3·H2O are determined by single crystal X-ray crystallography (Bruker-Nonius X8 Apex diffractometer, MoKα radiation, T = 150(2) K). The Al(hfa)3 complex is trigonal, a = 17.8944(11) Å, c = 12.4061(11) Å, P-3c1 space group, V = 3440.3(4) Å3, Z = 6, R = 0.076. The Sc(hfa)3·H2O complex is monoclinic, a = 16.0926(4) Å, b = 14.7980(3) Å, c = 24.4020(5) Å, β = 125.641(1)°, P21/c space group, V = 4722.54(18) Å3, Z = 8, R = 0.060. The structures of the complexes are formed by neutral molecules; the coordination environment of the metal atom involves six oxygen atoms of three β-diketone ligands (Al(hfa)3) and, additionally, a water oxygen atom (Sc(hfa)3·H2O). The shortest Al...Al distance is 6.203(6) Å. The Sc(hfa)3·H2O molecules are joined in dimers by hydrogen bonds with Sc...Sc separations of 5.6992(8) Å and 5.6853(8) Å. In the crystals, the molecules are joined by van der Waals interactions, moreover, there are intermolecular contacts F...H ∼ 2.5 Å in the structure of Sc(hfa)3·H2O.