The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine and its phenoxyl and aminyl radicals

The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine Ph—NH—C₆H₄—OH (D _NH= 353.4, D _OH=339.3 kJ mol^–1) and its semiquinone radicals D _NH(Ph—NH—C₆H₄—O^·) = 273.6, D _OH(Ph—N^·—C₆H₄—OH) = 259.5 kJ mol^–1 were first estimated using the parabolic model and experimental data (rate constants) on two elementary reactions with participation of N-phenyl-1,4-benzoquinonemonoimine (2). One of the reactions, namely, that of 2 with aromatic amines, was studied in this work using a specially developed method.     

Elaboration and Characterisation of Hybrid Materials of Polymethylhydrosiloxane Modified by Diamines of Various Lengths

The polymethylhydrosiloxane (PMHS) modified by bifunctional organic compounds (diamines), offer the possibility of producing organic-inorganic hybrid materials. These materials present excellent opto-electronic properties and find numerous applications such as the manufacture of electroluminescent diodes and ion or radiation sensors.This work shows that monolithic and transparent hybrid gels were obtained by reaction at room temperature of PMHS with diamines in tetrahydrofuran, using hexachloroplatinic acid (H₂PtCl₆·6H₂O) as catalyst. The products have been characterized by infrared and ²⁹Si MAS-NMR spectroscopy. The results show that the diamines have reacted with the PMHS leading to the monolithic and transparent gels in which both organic-inorganic —Si—(H)N—(CH₂) _n —N(H)—Si— bridges are formed (n = 3, 4 and 6). The thermal analysis of the xerogels was determined by TGA and DTA. The structure and texture of the obtained materials, were studied by Chemical Analysis and the Brunauer-Emmett-Teller (BET) method.     

Crystal structure and thermal stability of Ni151.5Pb24S92. Search for selenium- and tellurium-containing analogs

The crystal structure of the subvalent nickel—lead sulfide, which has been described previously as Ni₆₀Pb₉S₃₁, was established and the composition of this sulfide was refined based on powder X-ray diffraction data. The true Ni_151.5Pb₂₄S₉₂ composition of this compound was confirmed by the EDX techniques. The temperature range of stability of this compound (490—578 °C) was refined by differential thermal analysis. In the search for analogs, the triangulation of the Ni—Pb—Se and Ni—Pb—Te systems at 540 °C was carried out for the first time. No new ternary phases were detected.     

Development of a New Alkali Resistant Coating

The effect of different new sol-gel BaO—TiO₂—SiO₂ and CaO—BaO—TiO₂—SiO₂ coatings on long-term durability of glass fiber reinforced cement (GRC) was examined. Flexural strength of GRC was measured after curing for 7 to 150 days. Significant improvement was observed for coated GRC in this study and discussed in terms of the hydrate formation at interface. Concerned with the alkali resistance, CaO—BaO—TiO₂—SiO₂ coating was more effective than BaO—TiO₂—SiO₂ coating. In special, the 10CaO—10BaO—60TiO₂—20SiO₂ coating, prepared by sol-gel method, was recommended for the highest flexural strength of GRC and least corrosion at surface of E-glass fiber.     

Determination of the Rheological Properties of Polypropylene Filled with Colemanite

Colemanite (Ca₂B₆O₁₁.H₂O) in powder form was filled to polypropylene (PP) at concentrations of 5, 7.5, 11.25, 16.875, and 25.312 wt%, and filled PP granules were obtained. To prevent oxidation, an antioxidant (Songnox 1010) was added to the colemanite‐filled polypropylene mixture at a ratio of 0.2 wt%. The rheological properties of the resulting composite material were determined using a Melt Flow Index testing device, at four separate pressure settings (298.2, 524, 689.5, and 987.4 kPa) and four separate temperature settings (190°C, 200°C, 210°C, and 220°C). The viscosity, shear rate, shear stress, and power law index (n) values of the colemanite‐filled PP were measured as part of the testing conducted. The study determined that viscosity values increased by approximately 60% in response to increasing colemanite content in the resulting filled material, while shear rate values decreased by 62%. The viscosity values were found to decrease with increasing temperature and pressure values, while shear rate values were found to increase. Additionally, Power Law Index value was found to vary between 0.561 and 0.687, with an average value of 0.608 based on the colemanite content used. Copyright © 2017 John Wiley & Sons, Ltd.     

Thermal,Spectral and Antimicrobial Properties of New Zinc(II) Isobutyrate Compounds: Part I. Papaverine,Phenazone

Zinc carboxylate complexes with N-donor ligands exhibit antimicrobial and antifungal effects. The preparation and thermal properties of complex compounds Zn(isobut)₂ and Zn(isobut)₂L(isobut=(CH₃)₂CHCOO^–, L=papaverine — pap, phenazone — phen) are described in this paper. The newly synthesized compounds were characterized by elemental analysis, IR spectroscopy and TG/DTG, DTA methods.During the thermal treatment it was found that the release of organicligands (pap, phen) was followed by pyrolysis of zinc(II) isobutyrate. (C₃H₇)₂CO and CO₂ were found as gaseous products and zinc oxide as the final product of thermal decomposition. Gaseous and solid products of thermal decomposition were confirmed by chemical analysis, IR spectra and X-ray powder diffraction.This revised version was published online in November 2005 with corrections to the Cover Date.     

Heteroorganic betaines. 6. Structure and reactivity of silicon-containing organophosphorus betaines with the –S—Si—C—P+ fragment: a DFT study

The structures of silicon-containing organophosphorus betaines ^–S—SiR¹ ₂—CR² ₂—P⁺R³ ₃ and their ylide isomers were calculated using the density functional approach with the gradient-corrected PBE functional and extended TZ2P basis set. Three possible pathways of thermal decomposition of these betaines were analyzed. These are (i) cleavage of the central C—Si bond with the formation of a Wittig ylide and silanethione, (ii) intramolecular nucleophilic S _N-substitution with elimination of phosphine PR³ ₃ and the formation of silathiirane (the Corey—Chaikovscky transformation), and (iii) a Wittig-type decomposition followed by the formation of substituted silaethylene.The structures of products and transition states of these reactions were calculated. The cis-gauche conformation of the ^–S—Si—C—P⁺ fragment of betaines was found to be the most stable. This is in agreement with the results of X-ray diffraction study and can be rationalized by strong Coulomb attraction between the cationic and anionic centers. The betaines are stable toward retro-Wittig thermal decomposition. The Corey—Chaikovscky formation of thiirane is preferable under conditions of thermal decomposition. Retro-Wittig-type decomposition of betaines followed by the formation of silanethione is favored by intra- and intermolecular coordination of donor ligands.     

A Chiral Coordination Polymer of Silver(I) with Saccharinate and Pyridine: Synthesis,Spectral, Thermal,and Structural Characterization of [Ag(sac)(py)]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>

The first silver(I) complex of saccharinate (sac) with pyridine (py), [Ag(sac)(py)]_n has been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffractometry. The complex crystallizes in chiral, trigonal space group P3₁21 (No. 152) with unit cell parameters of a = 11.2605(2) Å, c = 17.3300(4) Å, V = 1903.02(6) ų and Z = 6. [Ag(sac)(py)]_n contains monomeric [Ag(sac)(py)] units linked into infinite helices by way of Ag⋅sAg interactions [d(Ag⋅sAg) = 2.909(2) and 2.985(1) Å]. The distorted square-planar environment of Ag is completed by an N-bonded sac [Ag—N = 2.084(2) Å] and a py molecule [Ag—N = 2.116(2) Å]. The N_sac—Ag—N_py angle is 173.85(10)^∘. The one-dimensional chains are crosslinked by C—H⋅sO interactions involving the carbonyl and sulfonyl O atoms of sac and aromatic-ring hydrogen atoms of both sac and py. The thermal stability of the title complex was investigated using thermogravimetry and differential thermal analysis in a static atmosphere of air. The first decomposition stage between 90 and 160^∘C corresponds to removal of the py molecule in a single stage, while the degradation of the sac moiety occurs at two stages in the temperature range 370–515^∘C, giving an end product of metallic Ag.     

Structural Studies on Saturated Aqueous Solutions of Manganese(II), Cobalt(II), and Nickel(II) Chlorides by X-ray Diffraction

As a part of our studies on crystallization processes of electrolytes, the structure of aqueous solutions of MCl₂ (M = Mn, Co, Ni) equilibrated with hydrate crystals, MCl₂ · mH₂O (m = 6, 4, 2), was investigated by means of X-ray diffraction at 25, 40, 55, and 70°C. The complexes formed in MnCl₂ solutions, were found to be mixed–ligand chloroaqua octahedral complexes of M²⁺ ions with the Mn—O and Mn—Cl distances of about 220 and 251 pm, respectively. The average number of Mn—Cl and Mn—O interactions increased from 1.2 to 1.9 and decreased from 4.8 to 4.1, respectively, with changing MnCl₂ solutions from Mn25 (MnCl₂ solution at 25°C) to Mn70 (MnCl₂ solution at 70°C). In the octahedral species of Co²⁺, the Co—O and Co—Cl distances were found to be about 211 and 240 pm, respectively. With an increase in the saturated concentration by changing temperature from 25 to 70°C, the average coordination number of the Co—Cl contact per Co²⁺ increased from 0.5 to 1.2, and the average number of Co—O interactions decreased from 5.5 to 4.8. The structural analysis was carried out by taking into consideration the existence of the tetrahedral species in the solutions saturated at 40, 55, and 70°C, on the assumption of the existence of [CoCl₄]^2–. The Co—Cl distance was found to be 228 pm, while the number of Co—Cl interactions in the [CoCl₄] complex was calculated to be 3.7 by the least-squares calculations. The Ni—O and Ni—Cl distances were estimated to be about 206 and 237 pm, respectively. The frequency factor n of the Ni—O and Ni—Cl interactions decreased monotonously from 5.6 to 5.0 and increased from 0.4 to 1.0, respectively, with increasing NiCl₂ concentration. The n values of the Co—Cl and Ni—Cl interactions of the octahedral complexes increased sharply with concentration at higher concentrations. Comparing structures of the complexes in the saturated solutions and the hydrate crystals of these metal ions, we discussed a role of the complexing species on crystallization of the hydrates.     

Solid state synthesis of calcium borohydroxyapatite

Calcium borohydroxyapatite was synthesized by the solid-state reaction of colemanite (Ca₂B₆O₁₁·5H₂O) and diamonium hydrogenphosphate ((NH₄)₂HPO₄) at 1200 °C for 12 h. X-ray diffraction pattern showed only the formation of calcium borohydroxyapatite. The experimental analysis assigned the chemical formula as Ca₁₀[(PO₄)_5.80(BO₃)_0.20](OH)₂. It was indexed in the hexagonal system with the refined unit cell parameters of a = 9.557(3) Å, c = 6.926(8) Å and space group P6₃/m. The experimental results verified that if colemanite was used as a primary reactant for both calcium and boron source, the calcium borohydroxyapatite could be obtained.     

Thermal oxidation of poly(1-trimethylsilylprop-1-yne) studied by IR spectroscopy

Thermal oxidation of poly(1-trimethylsilylprop-1-yne) was studied by IR spectroscopy in the 20—245 °C temperature interval. In the 20—160 °C temperature range, the reaction proceeds predominantly at the C—Me group as revealed by the decrease in the intensity of the bands of the methyl group bound to the C atom and the appearance of the bands of the hydroperoxide and methylene groups. The decomposition of hydroperoxides produces aldehydes and ethers. At 160—200 °C, oxidation occurs via two routes: at the C—Me and C=C groups, while the Me₃Si group remains unchanged. At 230—240 °C, the rate of the reaction occurring at the C=C bond is higher than the rates of the processes involving the MeC and Me₃Si groups. The relative content of the structural units was calculated for the samples oxidized at different temperatures. Plausible mechanisms of thermal oxidation of poly(1-trimethylsilylprop-1-yne) were considered on the basis of the data obtained.     

Synthesis and study of properties of linear permethylpoly(silane-siloxanes)

Heterofunctional polycondensation of ,-dichloropermethyloligosilanes Cl(Me₂Si) _m Cl (m = 2—6) with 1,5-dihydroxyhexamethyltrisiloxane was used to synthesize linear permethylpoly(silane-siloxanes) with the regular structure —[(SiMe₂) _m O(SiMe₂O)₃] _n —, which are soluble, unlike polydimethylsilane, in common organic solvents. The use of Py instead of Et₃N as an acceptor of HNl results in an increase in the yield, molecular weight, and characteristic viscosity of the copolymers. The molecular weight and viscosity characteristics, oxidative and thermal stabilities, and spectral properties of the synthesized copolymers were studied. The dependence of the oxidative and thermal stabilities of the synthesized copolymers on the number of the SiMe₂ units in the oligosilane fragment of the main chain was established.     

Mass spectrometric study of 4-azafluorenes

The dissociative ionization of 4-azafluorene and its methyl and phenyl derivatives was investigated. The relative intensity of the [M — CH₃]⁺ ion peak depends on the position of the CH₃ group in the 4-azafluorene ring. It was established that the loss of an RCN particle (R=H, CH₃, and C₆H₅) for unsubstituted 4-azafluorene takes place from the M⁺ and [M — H]⁺ ion, exclusively from the [M — H]⁺ ion for the methyl-substituted compounds, and from the [M — H]⁺ and [H — 2H]⁺ fragments for the phenyl-substituted derivatives. Randomization of the deuterium ions in the 9,9-d₂-4-azafluorene molecular ion was observed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 246–250, February, 1978.     

Synthesis,characterization and antimicrobial activity of cobalt(II), nickel(II)and copper(II) complexes with new asymmetrical Schiff base ligands derived from 7-formyanil-substituted diamine-sulphoxine and acetylacetone

Asymmetric 7-formyanil-substituted-imino-4-(4-methyl-2-butanone)-8-hydroxyquinoline-5-sulphonic acid (Schiff bases), react with Co^II, Ni^II and Cu^II ions to give 1:2, 1:1 and 2:1 complexes as established by conductometric titrations in 1:1 DMF:H₂O. The complexes were investigated by elemental analyses, molecular weight determinations, molar conductance, magnetic moments, thermal analysis, i.r., u.v.–vis. and e.s.r. spectra. The complexes have an octahedral crystal structure and general formula [ML·(OH₂)₂], where M^II = Co, Ni and Cu, and L = Na[7—X—HL], (—X— = (CH₂)₂, (CH₂)₃, p-C₆H₄, o-C₆H₄). Antimicrobial activity of these new ligands and their transition metal complexes has been screened in vitro on common fungi and bacteria.     

Thermal Property and Phase Transition of the Synthesized New Cubic Leucite-type Compounds

New cubic leucite-type compounds, CsMSi₂O₆ (M=B_0.2Al_0.8,Al_0.2Fe_0.8), Cs₂MSi₅O₁₂ (M=Cd, Mg, Ni, Zn) have been synthesized by the two-stage heat treatment of the solid-state reaction. The thermal expansion properties of the synthesized leucite-type compounds have been studied with HTXRD and LTXRD in the temperature range of 123 to 1273 K. The thermal expansion rate of CsB_0.2Al_0.8Si₂O₆ was found to be considerably smaller than that of CsAlSi₂O₆, while the thermal expansion property of Cs₂MSi₅O₁₂ (M=Mg, Zn, Cd) was found to have a linear relationship in the temperature range of 298 to 1273 K. By using Rietveld analysis it was found that the thermal expansion rate decreased with increasing the Si—O—M(Si) angle for cubic leucite-type compounds at 298 K, and that the phase transitions of CsAlSi₂O₆ and Cs_0.9Al_0.9Si_2.1O₆ were due to the relationship between the bond angle of Si—O—M(Si) of the three-dimensional framework structure and the space ratio in the unit cell at 298 K.This revised version was published online in November 2005 with corrections to the Cover Date.     

Sol-Gel Synthesis and Pyrolysis Study of Oxyfluoride Silica Gels

Silicon oxyfluoride materials are synthesized by the sol-gel method using triethoxyfluorosilane as precursor, bearing the Si—F bond. SiO_(2–0.5x) F _x gel preparation requires peculiar experimental control of hydrolysis and condensation reactions. Maintenance of the Si—F bond during gelling, heating and aging was studied in the case of processes carried out under an argon atmosphere or in air. Fluorine contents in resulting samples were quantified by FT-IR and X-ray photoelectron spectroscopy (XPS); specific surface area and porosity of powdered samples were determined by N₂ adsorption. The thermal stability of oxyfluoride gels was studied by thermogravimetric-mass spectrometric (TG-MS) coupled analyses during heat treatment, under He flow. Mass spectra recorded during principal weight losses indicate the release of variously fluorinated silicon species resulting from Si—F/Si—O exchange reactions. The evolution of these species was observed at different temperatures, depending on gelling conditions. In particular, degradation of Si—F moieties was prominent for gels aged in air, whereas samples processed under an argon atmosphere preserve the Si—F bond up to 300°C.     

R?ntgenstrukturanalyse als unentbehrliches Hilfsmittel bei der absoluten Konfigurationszuordnung einiger Iridoidglucoside sowie daraus synthetisierter 12-epi-Prostaglandine

Ohne Zusammenfassung

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X-ray-structure-analysis as indispensable tool in structure elucidation of some iridoidglucosides as well as 12-epi-prostaglandines derived from them

Abkürzungen C(OH)₄ -d-Glucopyranosyl - Ac CH₃—CO - Ts p-CH₃—C₆H₄—SO₂ - Cin C₆H₅—CH=CH—CO - HCin C₆H₅—CH₂—CH₂—CO—O - DME Dimethoxyethan     

Synthesis,crystal structure and magnetic properties of a two-dimensional mixed-valence assembly [Fe(salen)]2[Fe(CN)5NO]

A cyanide-bridged Fe^III–Fe^II mixed-valence assembly, [Fe^III(salen)]₂[Fe^II(CN)₅NO] [salen = N,N-ethylenebis(salicylideneiminato)dianion], prepared by slow diffusion of an aqueous solution of Na₂[Fe(CN)₅NO] · 2H₂O and a MeOH solution of [Fe(salen)NO₃] in an H tube, has been characterized by X-ray structure analysis, i.r. spectra and magnetic measurements. The product assumes a two-dimensional network structure consisting of pillow-like octanuclear [—Fe^II—CN—Fe^III—NC—]₄ units with dimensions: Fe^II—C = 1.942(7) Å, C—N = 1.139(9) Å, Fe^III—N = 2.173(6) Å, Fe^II—C—N = 178.0(6)°, Fe^III—N—C = 163.4(6)°. The Fe^II—N—O bond angle is linear (180.0°). The variable temperature magnetic susceptibility, measured in the 4.8–300 K range, indicates the presence of a weak intralayer antiferromagnetic interaction and gives an Fe^III–Fe^III exchange integral of –0.033 cm^–1.     

Thermal Decomposition of (4,4′-Dimethyl-2,2′-Bipyridine) Tris(Benzoate) Europium(III): Non-isothermal kinetics

The thermal behavior of[Eu₂(BA)₆(dmbpy)₂] (BA=C₇H₅O ₂ ^– , benzoate; dmbpy=C₁₂H₁₂N₂, 4,4-dimethyl-2,2-bipyridine) and its kinetics were studied under the non-isothermal condition in a static air atmosphere by TG-DTG, IR and SEM methods. Thermal decomposition of [Eu₂(BA)₆(dmbpy)₂] occurred in four consecutive stages at T _P 232, 360, 455 and 495°C. The kinetic parameters were obtained from analysis of the TG-DTG curves by Achar and Madhusudanan—Krishnan—Ninan (MKN) methods. The most probable mechanisms for the first stage was suggested by comparing the kinetics parameters.This revised version was published online in November 2005 with corrections to the Cover Date.     

Mass-spectrometric behavior of isomeric nitro- and nitroaminoindolizines and indoles

Peaks of [M — NO]⁺ and [M — NO₂]⁺ ions are characteristic for the mass spectra of nitroindolizines, whereas peaks of ions of the indole type, viz., [M — HCN]⁺ and [M- H,- HCN]⁺ (for alkylindoles), are not characteristic. In the mass spectra of nitroindoles the latter ions give more intense peaks, while the loss of a nitro group or its rearrangement is a considerably less significant process. When a dialkylamino group is introduced in the nitroindolizine molecule, the primary processes in the fragmentation of such compounds are due to fragmentation of the alkylamino group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 765–768, June, 1982.