The relationship between properties of fluorinated graphite intercalates and matrix composition

Inclusion compounds (intercalates) of fluorinated graphite matrix with butanone (C₂F_xBr_z·yCH₃COC₂H₅, x = 0.49, 0.69, 0.87, 0.92, z ≈ 0.01) were prepared by guest substitution from acetonitrile to butanone. The kinetics of the thermal decomposition (the 1st stage of filling → the 2nd stage of filling) was studied under isothermal conditions at 294–313 K. The relationship of the host matrices structure with inclusion compounds’ thermal properties and kinetic parameters is discussed.     

Preferential Solvation of Boscalid in Ethanol/Isopropanol + Ethyl Acetate Mixtures from the Inverse Kirkwood–Buff Integrals Method

The preferential solvation parameters (δx _1,3) of Boscalid in solvent mixtures of ethanol (1) + ethyl acetate (2), and isopropanol (1) + ethyl acetate (2) were derived from their available solubility data by means of the inverse Kirkwood–Buff integrals method. The values of δx _1,3 vary non-linearly with the solvent (1) proportion in the two solvent mixtures. For the ethanol (1) + ethyl acetate (2) system, the values of δx _1,3 are negative in ethanol-rich and ethyl acetate-rich mixtures, but positive in intermediate compositions; for the isopropanol (1) + ethyl acetate (2) system, the values of δx _1,3 are positive in ethyl acetate-rich mixtures and in intermediate compositions, but negative in isopropanol-rich mixtures. The δx _1,3 values are positive indicating that Boscalid is preferentially solvated by ethyl acetate. The magnitude of the preferential solvation of Boscalid by ethyl acetate is higher in isopropanol (1) + ethyl acetate (2) mixtures than in ethanol (1) + ethyl acetate (2) mixtures at 298.15, 308.15 and 313.15 K. The ethyl acetate action may be related to the disordered structure of ethanol or isopropanol molecules around the polar moieties of Boscalid, which increases the solvation, with maximum values near x ₁ = 0.40–0.45 for the two solvent mixtures.     

Synthesis and thermal properties of NiSbS–As doped phase

The substitution of Sb with As in the NiSbS intermetallic compound was studied in the framework of evaluating a possible increase of the thermoelectric properties. Different NiSb_1?xAs_xS samples were synthesized with increasing amounts of As (0 < x < 0.66) employing a simple synthetic route using a muffle furnace. Scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy was used to investigate the microstructure. X-ray powder diffraction techniques were employed in order to study the possible existence of a solid solution between NiSbS and NiAsS compounds, as well as to identify the crystal structure and determine the lattice parameters. All compounds were found to crystallise with the NiSbS prototype (cP12-P2₁3), with lattice parameters varying from a = 0.59341(7) nm (x = 0) to a = 0.56849(6) nm (x = 1). Good agreement with Vegard’s law was evidenced. Thermal measurements on NiSb_1?xAs_xS samples were carried out using DTA instruments to evaluate the thermal stability and the melting temperatures.     

Synthesis,thermal, spectral and biological properties of zinc(II) 4-hydroxybenzoate complexes

New zinc(II) 4-hydroxybenzoate complex compounds with general formula [Zn(4-OHbenz)₂L_n]·xH₂O, where 4-OHbenz = 4-hydroxybenzoate; L = isonicotinamide, N-methylnicotinamide, N,N-diethylnicotinamide, thiourea, urea, phenazone, theophylline, methyl-3-pyridylcarbamate; n = 2, 3; x = 0–3, 5, were synthesized and characterised by elemental analysis, thermal analysis and IR spectroscopy. The thermal behaviour of the prepared compounds was studied by TG/DTG and DTA methods in argon atmosphere. The thermal decomposition of hydrated compounds started with dehydration. During the thermal decomposition, organic ligand, carbon monoxide, carbon dioxide and phenol were evolved. The final solid product of the thermal decomposition was zinc or zinc oxide. The volatile gaseous product, solid intermediate products and the final product of thermal decomposition were identified by IR spectroscopy, mass spectrometry, qualitative chemical analyses and X-ray powder diffraction method. The antimicrobial activity of zinc(II) carboxylate compounds was tested against various strains of bacteria, yeasts and filamentous fungi (S. aureus, E. coli, C. parapsilosis, R. oryzae, A. alternata, M. gypseum). The presence of zinc in complexes led to the increase in their antimicrobial activity in comparison with free 4-hydroxybenzoic acid.     

Thermal behavior of furosemide

Data from theoretical, thermal, and spectroscopic methods were compared in order to map a possible mechanism for the thermal decomposition of furosemide, a diuretic compound, in solid state. TG/DTG curves suggested a two-stage decomposition process. The first product of decomposition is water (m/z = 18), released due to a dimerization resulting in the formation of an amide. Then carbon dioxide (m/z = 44), nitroxide (m/z = 30), and 2-methyl-furanyl ion (m/z = 81) are released in the second stage. The chlorine substituted benzene ring, due to the double bond conjugated system, being the last fraction to decompose. Theoretical calculations presented are in agreement with experimental results.     

Structural, electrical, and thermal properties in Ca-doped fresnoite ceramics

Polycrystalline ceramic samples of Ca-doped fresnoite of general formula Ba_2?x Ca _x TiSi₂O₈ (x = 0.0, 0.2, 0.4, 0.8, and 1) have been prepared by standard solid state reaction technique using high purity oxides and carbonates. The formation of the single phase compound and its structural parameters were investigated by X-ray diffraction followed by Rietveld refinement using non-centrosymmetric space group P4bm. The bond distances between atoms in a unit cell for all the compounds were also calculated which supports the structural results analyzed by Rietveld analysis. The frequency and temperature dependent dielectric constant and ac conductivity of all the compounds have been measured. The real and imaginary parts of the dielectric constant increases with the increase of temperature. The activation energy (E _a) calculated from ac conductivity increases from x = 0.0 to 0.4 and then decreases from x = 0.8 to 1.0. The modulated differential scanning calorimetry has been used to investigate the effect of substitution on the specific heat, heat flow, and other thermal parameters of the compounds.     

The relationship between properties of fluorinated graphite intercalates and matrix composition

Inclusion compounds (intercalates) of fluorinated graphite matrix with methylene dichloride (C₂F _x Br _z ·yCH₂Cl₂, x = 0.49, 0.69, 0.87, 0.92, z ≈ 0.01) were synthesized by guest substitution from acetonitrile to methylene dichloride. The kinetics of the thermal decomposition (the first stage of filling → the second stage of filling) was studied under isothermal conditions at 291–303 K. The relationship between the structure of host matrices with thermal properties and kinetic parameters of inclusion compounds is discussed.     

Anatase–rutile transformation at the synthesis of rutile pigments (Ti,Cr,Nb)O2 and their color properties

Synthesis of rutile pigments is based on solid state reaction and on Hedvall effect, i.e., phase transformation from anatase to rutile. Therefore, it is important to know the thermal behavior of these compounds (the temperature of this change). The goal was to prepare rutile pigments of type Ti_1?3xCr_xNb_2xO_2+x/2 by conventional solid state method from titanium dioxide TiO₂ (AV-01, anatase), to determine an influence of composition (x = 0, 0.05, 0.10, 0.20, 0.30, 0.50) and calcination temperature (850; 900; 950; 1,000; 1,050; 1,100; 1,150 °C) on color properties of these compounds and to analyze other starting compounds of titanium (hydrated anatase paste TiO₂·nH₂O, titanyl sulfate dihydrate TiOSO₄·2H₂O (VKR 611), hydrated sodium titanium oxide paste Na₂Ti₄O₉·nH₂O) and their reaction mixtures for x = 0.05 by simultaneous TG–DTA analysis. According to the highest chroma C of color, the optimal conditions for synthesis of these pigments are concentration x = 0.05 and calcination temperature 1,050 °C and higher. It was observed that initial temperature 760–830 °C is needful for a formation of rutile structure. This temperature is the lowest for hydrated Na₂Ti₄O₉ paste (760 °C) and similar for other starting compounds of titanium.     

The relationship between properties of fluorinated graphite intercalates and matrix composition

Inclusion compounds: intercalates of fluorinated graphite matrix with acetonitrile (C₂F_xBr_z·yCH₃CN, x=0.92, 0.87, 0.69 and 0.49, z≈0.01) were synthesized. The kinetics of the thermal decomposition (the 1^st stage of filling→the 2^nd stage of filling) was studied under isothermal conditions. The relationship between intercalates properties and composition and structure of the matrix is discussed. The online version of the original article can be found at     

The relationship between properties of fluorinated graphite intercalates and matrix composition

Inclusion compounds (intercalates) of fluorinated graphite matrix with acetone (C₂F _x Br _z ·y(CH₃)₂CO, x = 0.49, 0.69, 0.87, 0.92, z ≈ 0.01) were prepared by guest substitution from acetonitrile to acetone. The kinetics of the thermal decomposition (the first stage of filling → the second stage of filling) was studied under isothermal conditions at 292–313 K. The relationship of the host matrices structure with inclusion compounds thermal properties and kinetic parameters is discussed.     

Structural relaxation of PbO–WO3–P2O5 glasses

The structural relaxation of three compositional series of PbO–WO₃–P₂O₅ glasses with composition (0.5 ? x/2)PbO·xWO₃·(0.5 ? x/2)P₂O₅, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5; 0.5PbO·xWO₃·(0.5 ? x)P₂O₅, x = 0, 0.1, 0.2, and 0.3; and (0.5 ? x)PbO·xWO₃·0.5P₂O₅, x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5 was studied by thermomechanical analysis. The structural relaxation was studied in the transformation region using the Tool–Narayanaswamy–Moynihan’s and Tool–Narayanaswamy–Mazurin’s models. The relaxation function of Kohlrausch Williams and Watts was used. The parameters of both models were calculated by nonlinear regression analysis of thermodilatometric curves measured by thermomechanical analyzer under the constant load. Both models very well describe the experimental data. It was found that the modulus is increasing with increasing amount of WO₃ in all glasses. On the contrary, the width of the spectrum of relaxation times is decreasing with increasing amount of WO₃ in all studied glasses. Both models possess the values of metastable melt thermal expansion coefficient equal to their experimental value.     

Application of heating microscopy to the study of thermal behaviour of ZnO–P2O5–WO3 glasses

The effect of WO₃ on thermal behaviour and thermal stability of ZnO–P₂O₅–WO₃ glasses prepared in compositional series (100 ? x)[0.5ZnO–0.5P₂O₅] ? xWO₃ (x = 0–60) was investigated by heating microscopy and the results were correlated with the results determined by conventional thermodilatometry and differential thermal analysis. Thermoanalytical studies showed that the glass transformation temperature and dilatation softening temperature increase with increasing WO₃ content while thermal expansion coefficient decreases. The highest stability towards crystallization possess glasses containing 20–30 mol% WO₃. Major compounds formed by the crystallization of the glasses were Zn(PO₃)₂, WO₃ and W₁₈P₂O₅₉. The values of sphere temperature, hemisphere temperature and flow temperature obtained using heating microscopy were strongly influenced by the degree of crystallization process at the sintering.     

Thermal behaviour and spectroscopic investigation of some methyl 2-pyridyl ketone complexes

Pyridine derivative complexes are widely employed as biological active materials especially as antibacterial agents. Five transition metal(II) mpk complexes (mpk = methyl 2-pyridyl ketone) were synthesized and investigated using elemental analysis, spectroscopic techniques (IR and UV–Vis–NIR) and conductometric measurements. The general formulae established from experimental data were found to be [M(mpk)₂(NO₃)₂]·xH₂O (x = 0 for M = Cd(II), Zn(II), x = 2 for M = Cu(II)) and [M(mpk)₂(H₂O)₂](NO₃)₂ (M = Co(II), Ni(II)). These compositions were further confirmed by thermal analysis and their thermal stability in dynamic air atmosphere investigated.     

Glass transition, fragility, and structural features of amorphous nickel–tellurate–vanadate samples

The experimental FTIR spectra and DSC curves of the ternary 40TeO₂–(60?x)V₂O₅–xNiO glasses with 0 ≤ x ≤ 30 (in mol%) have been investigated. The glass transition properties that have been measured and reported in this paper, include the glass transition temperature (T _g), glass transition width (ΔT _g), heat capacity change at glass transition (ΔC _P) and Fragility (F). Thermal stability, fragility, and glass-forming tendency of these glasses have been estimated. Also, Poisson’s ratio (μ) and IR spectra of the presented systems have been investigated, to determine relationship between chemical composition and the thermal stability or to interpret the structure of glass. In addition, Makishima and Makenzie’s theory was applied for determination of Young’s modulus, bulk modulus, and shear modulus, indicating a strong relation between elastic properties and structure of glass. In general, results of this work show that glasses with x = 0 and 30 have the highest shear and young’s modulus which make them as suitable candidate for the manufacture of strong glass fibers in technological applications; but it should be mentioned that glass with x = 30 has higher handling temperature and super resistance against thermal shock.     

Chelating behavior, thermal studies and biocidal efficiency of tioconazole and its complexes with some transition metal ions

New seven metal complexes of tioconazole drug with the general formulae [MCl₂(L)₂(H₂O)_x].yH₂O (where, x = 0 and y = 1 for M = Mn(II) or x = 2, y = 2 for M = Co(II)), and x = 0, y = 3 for M = Cu(II), Ni(II), Zn(II)) and [MCl₂(L)₂(H₂O)₂]Cl.3H₂O (where M = Cr(III) and Fe(III)) have been prepared and characterized based on elemental analyses, IR, magnetic moment, molar conductance, and thermal analyses techniques. From molar conductance data bivalent metal chelates are non-electrolytes while Cr(III) and Fe(III) chelates are electrolytes and of 1:1 type. According to the IR spectral data, TCNZ is coordinated to the metal ions in a neutral unidentate manner with N donor site of the imidazole–N. All the complexes are octahedral except Mn(II) complex has tetrahedral structure. TCNZ drug and its metal complexes were also screened for their biological activity.     

The influence of concentration of doping elements on anatase–rutile transformation at the synthesis of rutile pigments (Ti,Cr,Nb)O2 and their pigmentary properties

An analysis of the effects of dopants concentration and different starting titanium compounds on the anatase to rutile phase transformation at the synthesis of rutile pigments Ti_1?3xCr_xNb_2xO_2±δ is presented in this study. The main goal was to analyze reaction mixtures for x = 0.05 (previous study) and 0.30 by simultaneous TG–DTA analysis and to determine the temperature of anatase–rutile transition. For x = 0.05, initial temperatures 760–830 °C are needful for a formation of rutile structure. The temperature is the lowest for the hydrated Na₂Ti₄O₉ paste (760 °C) and similar for other starting compounds of titanium. But for x = 0.30, the anatase–rutile transition begins at higher temperatures 910–1,030 °C because of high-Nb content, which is the inhibitor of this modification change. In addition, we found the influence of calcination temperatures (850, 900, 950, 1000, 1050, 1100, and 1150 °C) on color properties and particle size distribution of these materials prepared from anatase TiO₂ and with x = 0.30. Selected pigments were also analyzed by X-ray powder diffraction.     

Influence of Ca2+ substitution on thermal,structural, and conductivity behavior of Bi1−xCaxFeO3−y (0.40 ≤ x ≤ 0.55)

Bi_1?xCa_xFeO_3?y (0.40 ≤ x ≤ 0.55) perovskite oxides have been synthesized by solid-state reaction method to study their properties as a cathode material for intermediate temperature solid oxide fuel cells. The as prepared samples were characterized by X-ray diffraction, differential thermal analyzer/thermogravimetry, dilatometer, and impedance spectroscopy to study their structural, thermal, and electrical properties. The Rietveld refinement results confirmed that all the samples exhibit tetragonal structure with P4mm space group. In addition to this, sample x = 0.55 exhibits Ca₂Fe₂O₅ as a secondary phase. It has been observed that lattice parameters decrease with increase in calcium content. The thermal expansion coefficient and ionic conductivity increases with increase in calcium content up to x = 0.50. The highest ionic conductivity is observed for Bi_0.5Ca_0.5FeO_3?y i.e. 1.71 × 10^?2 S cm^?1.     

Synthesis, spectral and thermal studies of new copper (II) complexes with 1,2-di(imino-2-aminomethylpyridil)ethane

New copper (II) complexes of Schiff bases with 1,2-di(imino-2-aminomethylpyridil)ethane with the general composition CuLX _m (H₂O) _x , [L = Schiff base, X = Cl^?, Br^?, NO₃ ^?, ClO₄ ^?, CH₃COO^?, m = 2; X = SO₄ ^2?, m = 1] were prepared by template synthesis. The complexes were characterized by elemental analysis, conductivity measurements, magnetic moments, IR, UV–VIS and EPR spectra. The thermal behavior of complexes was studied using thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Infrared spectra of all complexes are in good agreement with the coordination of a neutral tetradentate N₄ ligand to the cooper (II) through azomethinic and pyridinic nitrogen. Magnetic, EPR and electronic spectral studies show a monomeric distorted octahedral geometry for all Cu(II) complexes. Conductance measurements suggest the non-electrolytic nature of the compounds, except for copper (II) nitrate and perchlorate complexes which are 1:2 electrolytes. Heats of decomposition, ΔH, associated with the exothermal effects were also determined.     

A Sensitive LC–ESI–MS–MS Method for the Determination of Huperzine A in Human Plasma: Method and Clinical Applications

A sensitive and specific liquid chromatography–electrospray ionization–tandem mass spectrometry method has been developed and validated for the quantification of huperzine A in human plasma. After the addition of trimetazidine, the internal standard (IS) and sodium hydroxide, plasma samples were extracted using 5 mL ethyl acetate. The compounds were separated on an Agilent Zorbax SB C₁₈ column (100 mm × 2.1 mm ID, dp 3.5 μm) using an elution system of 10 mM ammonium acetate solution–methanol–formic acid (18:82:0.1, v/v) as the mobile phase. The quantification of target compounds was obtained by using multiple reaction monitoring (MRM) transitions: m/z 243.1, 210.1 and 267.2, 166.0 were measured in positive mode for huperzine A and IS. Linearity was established for the range of concentrations 0.01–4.0 ng mL^?1 with a coefficient of correlation (r) of 0.9991. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.01 ng mL^?1. The method has been successfully applied to study the pharmacokinetics of huperzine A in healthy male Chinese volunteers.     

Isolation, structural, spectral, and thermal studies of imperatorin micro-crystals from Prangos pabularia

Imperatorin (mol. formula = C₁₆H₁₄O₄, mol. mass = 270) micro-crystals were isolated from ethyl acetate extract of the root parts of the plant Prangos pabularia. The composition related structural, spectral, and thermal properties were investigated. All the crystals were found to have single phase with orthorhombic structure. UV–Visible spectrum showed both direct forbidden transition and indirect allowed transition. The calculated optical band gaps (E _g) were 3.64 and 3.70 eV for direct forbidden and indirect allowed transitions, respectively. From the thermal studies of these crystals, melting point, stability, and other relevant information was obtained, ensuring the suitability of the material for application in any device where the crystals may have to withstand this range of temperature.