Synthesis and properties of polymethylgermanosilanes and polymethylgermanocarbosilanes

A series of polygermanosilanes and polygermanocarbosilanes with methyl, hydride, and vinyl substituents was synthesized by the Wurtz-Kipping reaction through dechlorination of mixtures of R¹R²SiCl₂ or R¹R²SiClCH₂Cl (R¹ and R² = H, Me, vinyl) and Me₂GeCl₂ in the presence of ultrafine suspension of sodium in toluene. The effect of the nature of substituents in the initial monomers on the yield, composition, and structure of the final products was studied by means of X-ray fluorescence analysis; FTIR spectroscopy; and ¹H, ¹³C, and ²⁹Si NMR spectroscopy. By means of size-exclusion chromatography, it was shown that methyl-and hydride-containing polymers have a unimodal molecular mass distribution (the polydispersity index does not exceed 4). The use of vinyl-substituted monomers results in an increase in polydispersity (the polydispersity index becomes approximately 20). At the same time, the yield of inorganic residue during pyrolysis in an inert atmosphere at 1100°C increases from 20 to 40% according to dynamic TGA data.     

Configurations and conformations of cis- and trans-N-methyl- and -N-benzyl-4,5- and -5,6-tetramethylenetetrahydro-1,3-oxazines

The configurations and conformations of cis- and trans-N-methyl- and -N-benzyl-4,5- and -5,6-tetramethylenetetrahydro-1,3-oxazines were determined by ¹H and ¹³C NMR spectroscopy. The cis isomers are conformationally homogeneous, having the hetero atom attached to the cyclohexyl ring, in the axial and equatorial positions, respectively, in the 5,6- and 4,5-tetramethylene compounds, similar to the case of the 2-p-nitrophenyl-substituted analogues investigated previously.     

The chemical transport of molybdenum and tungsten and of their dioxides and sulfides

Experiments have been made and an extensive thermodynamic discussion has taken place concerning the chemical transport of Mo, W, MoO₂, WO₂, MoS₂ and WS₂ in the presence of iodine. Efforts have been made to find the species via which Mo and W can migrate within the gas phase.Results: In each case the transport proceeds via the oxide iodides MoO₂J₂ and WO₂J₂ respectively, as already known for the dioxides. Thus the chemical transport of Mo, W, MoS₂ and WS₂ needs not only J₂ but also H₂O, usually liberated from the wall of the quartz ampoule.By means of J₂ + H₂O, the metals can be transported into the high temperature region of the ampoule (e.g., 1050 → 1150°C), whereas the transport of the sulfides proceeds in the opposite direction (e.g., 900 → 700°C).For the sulfide-transport the influence of the ratio of the transport agents $\text{J}{}_2\text{H}{}_2\text{O}$ has been discussed.The water content of the quartz glass out of which the ampoules are made is an important source for water, influencing the reactions.The addition of graphite which considerably lowers the H₂O partial pressure prevents any transport of the metals or the sulfides, which proves that the use of J₂ alone as a transport agent is insufficient in these cases.The gaseous iodides MoJ_x and WJ_z are without any importance under the experimental conditions used for the transport of the metals, their dioxides and sulfides.The partial pressures of MoO₂(OH)₂ and WO₂(OH)₂ under the experimental conditions chosen may usually be neglected. But in the system $\text{MoO}{}_2\text{H}{}_2\text{O}$ the transport via MoO₂(OH)₂ (1000 → 800°C) has been observed.The synthesis of MoO₂ and WO₂, starting with the elements or with powder of metal and trioxide is promoted by the addition of J₂. The reaction steps involved are discussed.     

Synthesis and characterization of thorium and uranium cyanoacetates and their coordination compounds

Tetracyanoacetates of thorium and uranium, M(NCCH₂COO)₄ (where M = Th or U) and dioxouranium (VI) dicyanoacetate [UO₂(NCCH₂COO)₂H₂O] and their coordination complexes with dimethyl sulphoxide (DMSO), dimethyl formamide (DMF), 1,10 phenanthroline (Phen) and 2,2′-bipyridyl (Bipy) have been synthesised and characterised by elemental analysis, molecular weight determination, molar conductance measurements, X-ray diffraction and infrared spectroscopic studies (4000–200cm⁻¹). Structural aspects of the compounds and the sites of bonding of the ligands to the central metal atom have been discussed in the light of shifts in thev(C ≡ N),v(COO),v(UO₂) and the metal-ligand stretching vibrations. Thermogravimetric analysis of the compounds have been carried out to study thermal decomposition modes.     

Preparation and properties of polyamides from 4-phenoxy- and 4-phenylthio-m-phenylenediamine and both aromatic and aliphatic diacids

New soluble aramids having pendant phenoxy and phenylthio groups were prepared in high molecular weights by the polycondensation of aromatic diacids with 4-phenoxy-m-phenylenediamine and 4-phenylthio-m-phenylenediamine, respectively. Glass transition temperatures (T_g) of these aramids were in the range 195–255°C, where T_gs of phenoxy pendant aramids were higher than those of phenylthio substituted aramids. These properties were compared with those of the parent aramids derived from m-phenylenediamine and aromatic diacids. Aromatic-aliphatic polyamides were also prepared by the reaction of these three diamines with aliphatic diacids having 4–10 methylene groups and were characterized in detail.     

Proton mobility and copper coordination in polysaccharide- and gelatin-based bioblends and polyblends

Polysaccharide- and gelatin-based bioblends and polyblends were synthesized and characterized by complex impedance spectroscopy, proton nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). Higher ionic conductivities of 7.9 × 10^?5 S/cm at room temperature and 2.5 × 10^?3 S/cm at 80 °C were obtained for the agar-chitosan polyblends. For all samples, the activation energies, calculated from the Arrhenius plot of ionic conductivity and from the onset of NMR line narrowing, are in the range 0.30–0.86 and 0.38–0.57 eV, respectively. The glass transition temperatures (T _g ^NMR ) varied from 200 to 215 K, depending on the sample composition. The temperature dependence of the ¹H spin–lattice relaxation revealed two distinct proton dynamics. The EPR spectra are characteristic of Cu² ions in tetragonally distorted octahedral sites. Quantitative analysis of the EPR spin Hamiltonian g _|| and A _|| parameters revealed copper ions complexed by nitrogens and oxygens in the samples containing chitosan or gelatin and only by oxygens in agar-based ones. The in-plane π bonding is less covalent for the gelatin and chitosan blends. Results suggest that natural bioblends and polyblends are interesting systems to be used in materials science engineering.     

Molecular DFT structure and packing effect of thiodipropionic and dithiodiglycolic acids and salts

Molecular and periodic DFT structure calculations of thiodipropionic and dithiodiglycolic acids, S_n[(CH₂)(COOR)]₂ (n = 1,2, R = H, Na), were performed. Computed structures were analyzed and compared to the experimental data (a C_s conformation is favored in solution than C₂ in solid state). Four close and low-energy optimized conformations were analyzed: C_2v, C₂, C_s and C₁. Small changes in the conformation stability (ΔG) and symmetry group were observed in polar medium. Periodic DFT-GGA approaches have been performed to determine the importance of weak interaction upon the crystal structure of the thiodipropionic acid, e.g., S–H and/or O–H hydrogen bonding. More SH and OH dispersed bands were observed in the optimized structure. Using a full analysis of the DOS of O–H or S–H bonding contributions, a notable interlayer bonding in the parent structure was revealed. Therefore, the presence of such weak interaction ONa⁺ or OH may thus change the point group symmetry of the crystal upon packing effect.     

Synthesis and properties of N3 and CN delivery compounds and related precursors for nitride and ceramic fabrication

The simple azido and cyano compounds Cl₂AsN₃, Br₂AsN₃, (C₆H₅)SiH₂N₃, (C₆H₅)SiH₂CN and p‐(tolyl)SiH₂CN have been prepared for the first time by metathesis reactions involving the corresponding halides and NaN₃, LiN₃ and LiCN. These compounds represent a highly reactive and efficient family of delivery reagents for the preparation of N₃ and CN molecular precursors to bulk ceramics and nitride thin films. They are isolated as low volatility liquids and characterized by spectroscopic methods and chemical analysis. Ab initio simulations were used to elucidate the structural and vibrational properties of the simpler, fully inorganic Cl₂AsN₃ and Br₂AsN₃ species. This theoretical treatment was extended to include the hypothetical H₂AsN₃ and HClAsN₃ derivatives which are particularly desirable as single‐source low‐temperature As? N sources for the formation of highly sought after, metastable GaAs_1?xN_x materials for solar cell applications. The practical utility of the title molecules is also demonstrated by synthesizing several representative compounds of B, Be, Ga and Al, which are of interest for the development of open frameworks, optoelectronic nitrides and refractory B? C? N hybrids. The cyanide derivatives (C₆H₅)SiH₂CN and p‐(tolyl)SiH₂CN react readily with Be and B halides to yield crystalline Be(CN)₂ and amorphous B? C? N. The latter is crystallized upon heating to form graphite‐like polymorphs with homogeneous nanoscale morphologies. The azide derivatives Cl₂AsN₃, Br₂AsN₃ and (C₆H₅)SiH₂N₃ react readily with GaBr₃, GaCl₃ and BBr₃ to produce high yields of the previously reported Br₂GaN₃, Cl₂GaN₃ and Br₂BN₃, respectively. The latter is shown to possess a trimeric molecular structure in which the α‐nitrogen of the azide group bridges the boron atoms to form cyclohexane‐like B₃N₃ rings. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and properties of ansa-titano- and ansa-zirconocenes

A series of methyl and allyl derivatives of ansa-titano- and ansa-zirconocenes with isopropylidene or dimethylsilyl bridging groups were synthesized. A dinuclear complex, [Me₂C(C₅H₄)₂]₂Ti₂O₂, resulting from the thermal decomposition of the corresponding dimethyl derivative of ansa-titanocene in the air, was characterized by X-ray diffraction analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 967–969, May, 1993.     

Preparation and photolysis of poly-p-ethylacrylophenone and poly-p-chloroacrylophenone and their copolymers with styrene and methyl methacrylate

Poly-p-ethylacrylophenone (PPEtAP) and poly-p-chloroacrylophenone (PPClAP) and their copolymers with styrene (PEtAP/S) and (PClAP/S) and with methyl methacrylate (PEtAP/MMA) and (PClAP/MMA) were prepared. Quantum yields of main-chain scissions at 366 nm at room temperature in benzene solution are of the same order as those of the unsubstituted polyacrylophenone and its copolymers. Substitution with chlorine and ethyl group in the para position compared to the unsubstituted polyacrylophenone and its copolymers leads to an increase of the lifetime for the n–π^* excited triplet state, as is evident from the measured quenching constants of photolysis. The low-temperature emission spectra of the copolymers are similar to the spectra of the model compounds in a polymer film. For the homopolymer, however, the character of the emission spectrum changes considerably.     

Organosilicon Amidophosphates and Their Eu and Er Complexes in Solutions and Films: Spectral and Luminescence Properties

Fluorescence and fluorescence excitation spectra of phosphorus-containing organosilicon ligands O = PX₂NHR (X = NMe₂, OPh; R = CH₂CH₂CH₂Si(Oet)₃ and their Eu(III) complexes in acetonitrile solutions and in films are studied. In UV region (285–420 nm), bis(dimethylamido)triethoxysilylpropylamidophosphate (X = NMe₂) and diphenyltriethoxysilylpropylamidophosphate (X = OPh) exhibit two emission bands, whose position and intensity depend on the nature of substituents at the phosphorus atom. The Eu complexes show the ligand and the cation luminescence. The emission bands of coordinated ligands are shifted to long-wave region. The cation luminescence appears as three or four bands due to f-f transitions from the excited ⁵ D ₀ level to the lower ⁷ F _1–4 levels. The most intense transition is ⁵ D ₀ → ⁷ F ₂. The emission band in a region of 420 nm appears in solutions and films prepared from both pure ligands and their Eu(III) complexes. This band is due to luminescence of spatially crosslinked nanoparticles of sesquioxane structure. The intensity ratio of the Eu³⁺ emission bands changes when going from solutions to films, the emission intensity increases in a range of 420 nm. Films containing incorporated Er complexes with amidophosphates show intense luminescence of a matrix at 430 nm and a series of weak narrow bands due to the Er³⁺ cation at 550–700 nm.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 550–558.Original Russian Text Copyright © 2005 by Semenov, Cherepennikova, Klapshina, B. Bushuk, S. Bushuk, Douglas.     

Micro- and semimicrodetermination of carbon and hydrogen

Summary Experiences in the determination of carbon and hydrogen with different methods are dealt with and an apparatus is described which uses a new method for vaporization of the sample, a new tube filling, and modified absorption tubes. Tapered ground joints, flat ground joints, ball and socket ground joints and flexible metal tubes are used to ascertain tightness of the apparatus without introducing risk of breakage. The accuracy for microanalyses with samples between 2 and 5 mg is 0,1% for hydrogen and 0,3% for carbon, for semimicroanalyses with samples between 10 and 20 mg 0,05% for hydrogen and 0,2 for carbon.

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Zusammenfassung Erfahrungen mit verschiedenen Methoden zur Bestimmung von Kohlenstoff und Wasserstoff werden mitgeteilt. Eine neue Apparatur für ein neuartiges Verfahren zur Vergasung der Analysensubstanz mit neuer Rohrfüllung und abgeänderten Absorptionsröhrchen wird beschrieben. Kegel-Flach-und Kugelschliffe sowie biegsame Metallröhren gewährleisten eine gasdichte Apparatur, ohne deren Bruchsicherheit zu mindern. Die Genauigkeit der Resultate bei Mikrobestimmungen mit 2 bis 5 mg Einwaage beträgt 0,1% für Wasserstoff und 0,3% für Kohlenstoff, bei Halbmikroanalysen mit Einwaagen von 10 bis 20 mg 0,05% für Wasserstoff und 0,2% für Kohlenstoff.

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Résumé On met en uvre des expériences pour le dosage du carbone et de l'hydrogène par différentes méthodes et décrit un appareil qui utilise un nouveau procédé de vaporisation de l'échantillon, un nouveau remplissage du tube à combustion et des tubes d'absorption modifiés. On emploie des rodages côniques, plans, sphériques et des tubes de métal flexibles pour assurer l'étanchéité de l'appareil sans introduire de risque de casse. La précision des microanalyses avec des prises d'échantillon allant de 2 à 5 mg est 0,1% pour l'hydrogène et 0,3% pour le carbone; pour les semi-micro analyses, avec des prises allant de 10 à 20 mg, on trouve 0,05% pour l'hydrogène et 0,2% pour le carbone.

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With 4 figures.     

Synthesis and Structure of YbCuGe and YbIrGe

Summary. The equiatomic ytterbium–transition metal–germanides YbCuGe and YbIrGe were synthesized in single crystalline form from CuGe and IrGe master alloys and ytterbium via the Bridgman technique and they were characterized through their X-ray powder patterns. The structures were refined from X-ray single crystal diffractometer data: NdPtSb type, P6₃mc, a=421.36(8), c=703.9(1) pm, wR2=0.0234, 210 F² values, 11 variable parameters, BASF=0.35(9) for YbCuGe and TiNiSi type, Pnma, a=671.09(6), b=421.55(5), c=757.16(7) pm, wR2=0.0782, 519 F² values, 20 variable parameters for YbIrGe. The copper (iridium) and germanium atoms build up [CuGe] and [IrGe] networks. In YbCuGe the two-dimensional [CuGe] network consists of puckered layers of Cu₃Ge₃ hexagons (247pm Cu–Ge) that are charge balanced and separated by the ytterbium atoms. In contrast, the ordered Ir₃Ge₃ hexagons show a strong orthorhombic distortion and the [IrGe] network is three-dimensional with a distorted tetrahedral germanium coordination around iridium with almost equal Ir–Ge distances (252–259pm). The ytterbium atoms fill cages within this network. The cell volumes of YbCuGe and YbIrGe are indicative for purely trivalent ytterbium.     

Protonation of amino and hydroxypyrimidines. NMR-spectra and structures of mono and dications

Proton-NMR. spectra of amino- and hydroxypyrimidines including biologically important bases have been measured in four solvents: CF₃COOH, CF₃COOH? SO₂, FSO₃H and FSO₃H? SbF₅–SO₂ at 27° and ?55°C. In CF₃COOH mono-cations are formed, whereas in FSO₃H and FSO₃H? SbF₅–SO₂ double protonation occurs. In each case the structures of the protonated species are derived from the chemical shifts of CH, NH and OH protons and proton-proton spin coupling constants. A combination of the measurements described leads to a complete assignment of all proton resonances of the protonated pyrimidines. This approach is also recommended for the structural determination of heterocyclic compounds.     

Hirshfeld surface analysis and spectroscopic and DFT studies of p-acetotoluidide and p-thioacetotoluidide

The Hirshfeld surface analysis, theoretical calculation, and IR and Raman spectra of p-acetotoluidide and p-thioacetotoluidide were reported. Hirshfeld surfaces and fingerprint plot have been used for visualizing, exploring, and quantifying intermolecular interactions in the crystal lattice of the title compounds. The packing of the molecules in the crystal structure of p-acetotoluidide and p-thioacetotoluidide forms the chains of N–H···O and N–H···S hydrogen bonds, respectively. The close contacts are also dominated by H···H and H···C/C···H interactions. The analysis of Hirshfeld surface has been well correlated with the spectroscopic studies. Theoretical calculations of the title compounds’ isolated molecule have been carried out using DFT at the B3LYP level.     

Synthesis and characterisation of cobaltite and ferrite spinels using thermogravimetric analysis and X-ray crystallography

The synthesis for a series of ferrite (M^IIFe₂O₄) and cobaltite (M^IICo₂O₄) spinels was investigated where M^II is Mg, Co, Ni, Cu or Zn. The ferrites were prepared at a calcination temperature of 800 °C; the cobaltites at 500 °C. TG–MS indicated that reduction of Co^III to Co^II occurs at ca. 800 °C, hence, the lower calcination temperature. For both the ferrites and the cobaltites, the evolution of water and CO₂ during the calcination suggests the presence of both species in the precipitates. The observed mass losses indicated that the precursor basic carbonate precipitates for the cobaltite synthesis were predominantly carbonate, while the precursor basic carbonate precipitates for ferrite synthesis were predominantly hydroxide in character. XRD data showed successful synthesis of the ferrites with minimal contamination from the parent oxides, while the cobaltites were observed to be predominantly of the spinel structure.     

Synthesis and Structure of YbCuGe and YbIrGe

The equiatomic ytterbium–transition metal–germanides YbCuGe and YbIrGe were synthesized in single crystalline form from CuGe and IrGe master alloys and ytterbium via the Bridgman technique and they were characterized through their X-ray powder patterns. The structures were refined from X-ray single crystal diffractometer data: NdPtSb type, P6₃mc, a=421.36(8), c=703.9(1) pm, wR2=0.0234, 210 F² values, 11 variable parameters, BASF=0.35(9) for YbCuGe and TiNiSi type, Pnma, a=671.09(6), b=421.55(5), c=757.16(7) pm, wR2=0.0782, 519 F² values, 20 variable parameters for YbIrGe. The copper (iridium) and germanium atoms build up [CuGe] and [IrGe] networks. In YbCuGe the two-dimensional [CuGe] network consists of puckered layers of Cu₃Ge₃ hexagons (247pm Cu–Ge) that are charge balanced and separated by the ytterbium atoms. In contrast, the ordered Ir₃Ge₃ hexagons show a strong orthorhombic distortion and the [IrGe] network is three-dimensional with a distorted tetrahedral germanium coordination around iridium with almost equal Ir–Ge distances (252–259pm). The ytterbium atoms fill cages within this network. The cell volumes of YbCuGe and YbIrGe are indicative for purely trivalent ytterbium.     

Linear and Star-Shaped Extended Di- and Tristyrylbenzenes: Synthesis,Characterization and Optical Response to Acid and Metal Ions

Two linear 1,4-distyrylbenzenes and five star-shaped 1,3,5-tristyrylbenzene derivatives ( L_2a and L_2b , Y₀–Y₃ and Y_NBu ) were synthesized and spectroscopically characterized. The photophysical properties, optical response to acid and metal ions were investigated. Upon backbone extension of linear distyrylbenzenes or the introduction of dibutylanilines, the electronic spectra are redshifted. Incorporation of electron-deficient pyridyl units does not significantly affect the optical properties. Variation of the number of pyridine rings and substitution pattern tune the fluorescence response to acids and metal ions. The novel arenes discriminate Al³⁺, Mn²⁺, Fe³⁺, Fe²⁺, Cd²⁺, Ag⁺ and Hg²⁺.     

Organo-soluble and transparent polyimides containing phenylphosphine oxide and trifluoromethyl moiety: Synthesis and characterization

A series of aromatic polyimides (PI-II_a-d) containing lateral phenylphosphine oxide (PPO) and trifluoromethyl (-CF₃) moiety were prepared from an aromatic diamine, 2,5-bis[(4-amino-2-trifluoromethylphenoxy)phenyl]diphenyl-phosphine oxide (BATFDPO) and various aromatic dianhydrides via a two-step chemical imidization procedure. In parallel, for comparison, another series of polyimides (PI-I_a-d) without trifluoromethyl were synthesized from a diamine, 2,5-bis[(4-aminophenoxy)-phenyl]diphenylphosphine oxide (BADPO) and the same dianhydrides. It was found that both of the two series of polyimides (PIs) were soluble in polar aprotic solvents, such as N-methyl-2-pyrrolidinone (NMP) and the solubility of PI-II_a-d was highly enhanced by the introduction of the bulky -CF₃ group. Flexible and tough PI films with tensile strengths higher than 70 MPa were cast from the PI solution. The introduction of -CF₃ moiety slightly sacrificed the thermal stability and mechanical properties of the PI films. For example, PI-II_a-d showed 5% weight loss at 472-476 ^°C, which was about 50 ^°C lower than those of their PI-I_a-d analogues. However, -CF₃ group apparently improved the optical transparency and decreased the refractive indices of the PI films. PI-II_d derived from BATFDPO and 4,4’-hexafluoroisopropylidenediphthalic anhydride (6FDA) exhibited the highest optical transparency with the transmittance of 90% at 400 nm and the refractive index as low as 1.5511 at 1310 nm.     

Preparation and thermal reactivity of some rare earth and uranyl hydrazinesulfinates and sulfite hydrazinates

Hydrazinesulfinate and sulfite hydrazinate derivatives of rare earth elements of composition Ln(N₂H₃SOO)₃(H₂O) and Ln₂(SO₃)₃(N₂H₄)_x(H₂O)_y, respectively, where Ln=La, Ce, Pr, Nd and Sm, have been prepared and characterized by chemical analysis and infrared spectra. The uranyl complexes of the composition UO₂(N₂H₃SOO)₂, UO₂(N₂H₃SOO)₂(N₂H₄) and UO₂SO₃(N₂H₄)(H₂O) have also been prepared under different reaction conditions and studied by different physicochemical techniques. Thermal properties of all these complexes have been studied by thermogravimetry, and differential scanning calorimetry. The hydrazinesulfinate derivatives of rare earth elements undergo thermal decomposition in multisteps to give the respective metal sulfate as the residue. The other series of complexes, viz., rare earth sulfite hydrazinates gave a mixture of metal sulfate and metal oxide as the end products. However, all the uranyl complexes undergo decomposition in air to give UO₂SO₃ as the final product.