Crystal structure of copper ammonium oxalate dihydrate, Cu(NH 4)2(C2O4)2.2H 2O

The crystal structure of copper ammonium oxalate dihydrate (space group P1̃) has been derived from a refinement of the two-dimensional (hk0) and (0kl) x-ray data using the atomic coordinateis of the isomorphous salt CuK 2(C2O4)2.2H2O as the starting point of the analysis. In contrast to the chromium complexes of oxalic acid the C-C bonds in both the two nonequivalent oxalate ions in the unit cell are single bonds (1.58 and 1.61 Å) consistent with the conclusion of Jeffrey and Parry that the carboxyl groups of the oxalate ion are separated by a pure a bond with little or no π conjugation across the molecule. Both the oxalate ions are slightly nonplanar. The copper ions occupy the special positions (0, 0, 0) and 0, 1/2, 0) and their coordination is of the distorted octahedral type with four nearest oxygen neighbors ( ≃ 2 Å) at the corners of a square and two more distant atoms along the octahedral bond direction. The environment of the NH4+ ions consists of eight nearest oxygen atoms at a mean distance of 3 Å.

Stimulation by thyrotropin, long-acting thyroid stimulator, and dibutyryl 3′, 5′-adenosine monophosphate of protein and ribonucleic acid synthesis and ribonucleic acid polymerase activities in porcine thyroid in Vitro

The in vitro incorporation of [3H]uridine into RNA and [3H]leucine into protein in slices of porcine thyroid was studied. Thyrotropin (10-500 mU/ml of medium), when added with [3H]uridine, inhibited incorporation into RNA, but as little as 10 mU of thyrotropin per ml stimulated incorporation of [3H]orotic acid into RNA. Uridine kinase (EC 2.7.1.48) was found to be inhibited in slices incubated with thyrotropin whereas UMP 5′ nucleotidase (EC 2.1.3.5) was not. Preincubation of slices with thyrotropin (5-50 mU/ml) led to enhanced incorporation of subsequently added [3H]uridine and [3H]leucine. When slices were preincubated with long-acting thyroid stimulator-IgG (2.5 or 5 mg per ml of medium) incorporation of [3H]uridine and [3H]leucine was similarly enhanced, with the smaller concentration being more effective. Without preincubation these stimulatory effects were mimicked by 1 mM dibutyryl 3′,5′-AMP and, to a lesser extent, 1 mM 3′,5′-AMP. AMP and ATP also stimulated [3H]uridine incorporation in this system but only after more prolonged periods of incubation than were required for the other nucleotides. RNA polymerase (EC 2.7.7.6) activity measured in isolated thyroid nuclei had two components, one Mg2+-stimulated and the other requ ring Mn2+ and high salt content [0.4 M (NH4)2SO4]. These activities, and particularly the former, were enhanced if thyroid slices were incubated with thyrotropin (5-100 mU/ml of medium), 2.5 mg or 5.0 mg of long-acting thyroid stimulator-IgG per ml, or 1 mM dibutyryl 3′,5′-AMP, before isolatior of the nuclei and measurement of enzyme activities; 1 mM AMP, ADP, or 2′,3′-GMP had no influence. Added directly to the nuclei, thyrotropin, long-acting thyroid stimulator-IgG, and dibutyryl 3′,5′-AMP had no effect on RNA polymerase activities. These data are seen as affording evidence for mediation by 3′,5′-AMP of effects of thyrotropin and long-acting thyroid stimulator on thyroid RNA and protein synthesis, at least in part through an indirect stimulation of nuclear RNA polymerase activities.

Raman spectra of crystalline double sulphates Part II. Ammonium double sulphates

Raman spectra of single crystals of (NH4)2M(SO4)2·6 H2O where M=Mg, Zn Ni or Co have been recorded using λ 2537 excitation. Interesting results concerning the substitution of the divalent atoms in the double sulphate lattice on the sulphate and ammonium frequencies are observed. The spectra of these double sulphates are discussed in the light of the known crystal structure details and in relation, to the spectra of the corresponding potassium double sulphates, reported recently by the author. The Raman spectrum of NaNH4SO4·2 H2O has also been recorded for the first time and the results obtained are also included.

Polarization reversal studies in ferroelectric taap

Telluric Acid Ammonium Phosphate (Te(OH)62(NH4)H2PO4(NH4)2HPO4) reffered to as TAAP is a recently discovered class m ferroelectric.1 It undergoes FE-PE transition at 48°C. Switching studies in this crystal has been carried out in the temperature range -14°C to 39°C by applying fields up to 4 kV/cm. Measurements were carried out on (101) plates cut from the crystals grown from solution. X-ray irradiation was carried out at room temperature by means of an x-ray tube operating at 25 kV and 15 mA with copper target. Air drying silver paste was used as electrodes. Samples were checked for hysteresis loop using a modified Sawyer-Tower circuit. The Ps value obtained from the loop is 2.1 μC/cm2 which is comparable to the earlier reported value. It was however noticed that the loop was slightly shifted to right with respect to the origin indicating the presence of a small internal bias which was 100 V/cm in the virgin crystal. This bias could not be removed even after repeated crystallization. On irradiation the internal biasing field increased which was indicated by a further shift of the hysteresis loop. The bias seems to saturate at about 750 V/cm for which the crystal had to be irradiated for about 3 hours.

Dielectric behaviour and ferroelectricity in alums

Introduction The alum family of double salts with the general formula M1+M3+(RO4)2.12H2O where M1+ is a monovalent ion (M1+ = K, Rb, Cs, Tl, NH4, CH3NH3, NH3OH3 NH3NH2, etc.) and M3+ is a trivalent metal such as Al, Fe, Cr, V, In, Ga, etc. and R is S or Se, form an isomorphous series and their general features indicate a common cubic space group Pa3. Lipson1 showed subsequently that there exist three different structure types agr, β and γ and the structure of a particular alum is dependent on the radius of the monovalent atom. The agr structure is typical of medium sized ions, the β of the larger ones and the γ of the small Na atom.2 Ferroelectricity has been reported only in alums containing NH4, CH3NH3, NH3NH3 and NH3OH. Their hindered rotations as well as the influence of sulphate group disorder on the dielectric behaviour of alums is still not clear.3 No study of the temperature dependence of the low frequency dielectric constant of some of the alums, particularly those of Cs, Rb and Tl, have been made so The present investigation was undertaken to correlate their dielectric behaviour with their composition and structural differences. Under the same experimental conditions, methyl ammonium and ammonium alums also were studied and compared with the known data.

Preparation and characterization of hydrazine derivatives. Part-II: Reaction of transition metal ammonium double sulphates with hydrazine hydrate

Transition metal ammonium double sulphates (NH4)2M(SO4)2· 6H2O, where M = Fe, Co and Ni react with hydrazine hydrate in air giving crystalline compounds of the general formula (N2H5) [M(N2H3COO)3] H2O. The reaction proceeds through (N2H5)2 M(SO4)2, · 3N2H4, (N2H5)2 [M(OH)4 · (N2H4)2], M(N2H3COO)2 · (N2H4)2 and N2H5 [M(N2 H3 COO)3] intermediates. The reaction sequence is followed by chemical analysis and infrared spectra. A possible reaction mechanism has been suggested.

Dehydrogenation of ammonia borane in fluoro alcohols

Dehydrogenation of ammonia borane was carried out in fluor alcohol solvent in order to obtain compounds that are more likely candidates suitable for regeneration. Even though ammonia borane undergoes self-dissociation in 2,2,2-trifluoroethanol to liberate H-2, decent hydrogen release rates were obtained by using Co-Co2B, Ni-Ni3B, and Co-Ni-B nanocomposites as catalysts. These catalysts are magnetic in nature and hence can be separated from the reaction mixture using a magnet for re-use. The final by-product NH4+ B(OCH2CF3)(4)(-) obtained after the catalytic dehydrogenation of ammonia borane was thoroughly characterized using H-1, B-11, and C-13 NMR and IR spectroscopies. The FTIR data showed that the B-O bond in NH4+ B(OCH2CF3)(4)(-) is slightly weaker compared to boric acid. Preliminary investigations on the regenerative routes for ammonia borane from the by-product NH4+ B(OCH2CF3)(4)(-) showed indications of the formation of BNHx species. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

Synthesis of Layered Perovskite Oxides, ACa2-xLaxNb3-xTix010 (A = K, Rb, Cs), and Characterization of New Solid Acids, HCa2-xLaxNb3-xTixOlo (0 < x d 2), Exhibiting Variable Bronsted Acidity?

Layered perovskite oxides of the formula ACa~,La,Nb3-,Ti,010 (A = K, Rb, Cs and 0 < x d 2) have been prepared. The members adopt the structures of the parent ACazNb3010. Interlayer alkali cations in the niobium-titanium oxide series can be ion-exchanged with Li+, Na+, NH4+, or H+ to give new derivatives. Intercalation of the protonated derivatives with organic bases reveals that the Bronsted acidity of the solid solution series, HC~ ~ , L ~ ,N~ ~ , T ~ ,dOep~eOnd, s on the titanium content. While the x = 1 member (HCaLaNbzTiOlo) is nearly as acidic as the parent HCazNb3010, the x = 2 member (HLazNbTizOlo) is a weak acid hardly intercalating organic bases with pKa - 11.3. The variation of acidity is probably due to an ordering of Nb/Ti atoms in the triple octahedral perovskite slabs, [Ca~,La,Nb~,Ti,0~0], such that protons are attached to NbO6 octahedra in the x = 1 member and to Ti06 octahedra in the x = 2 member.

Chloroplastic glutamine synthetase from normal and water stressed safflower (Carthamus tinctorius L.) leaves

The chloroplastic isoform of glutamine synthetase (GS(2), EC 6.3.1.2) from normal and water stressed safflower (Carthamus tinctorius L. cv.A-300) leaves has been purified to apparent electrophoretic homogeneity by a procedure involving anion-exchange, hydrophobic and size-exclusion chromatography followed by electroelution of the protein from preparative polyacrylamide gels. The observed molecular weight of the native protein varied from 305-330 kDa depending on the sizing column employed. The native protein is composed of 44 kDa subunits. Under conditions of saturating ammonium and at ATP levels of 0.1-10 mM, double-reciprocal plots with respect to glutamate are biphasic and concave downward at high concentrations of the varied substrate for normal enzyme but are linear for enzyme from water-stressed plants. Under subsaturating ATP levels, K-Glu is over 18-fold lower for enzyme from stressed leaves. The K-m, (ATP) varies with Mg2+ levels in the assay mixture. Double-reciprocal plots of initial velocity with respect to ATP at changing fixed levels of NH4+ are linear for normal enzyme but are curved upwards for enzyme from stressed leaves. Initial velocity data of 1/v vs. 1/ammonium for the enzyme from both the sources are non-linear (curved upwards) when ATP is saturating. At subsaturating ATP levels, the data are linear for normal enzyme but are still non-linear for the enzyme from stressed leaves. The results obtained suggest positively cooperative binding of NH4+ A V-max(/2) value of 3.6 mM for Mg2+ was obtained at 5 mM ATP. The isoelectric point of the native protein from normal and stressed leaves was determined to be, respectively, 5.6 and 6.1. The mixed competitive and competitive inhibitors, methionine sulfoximine and ADP and K-i values of 0.086 mM (0.017 for the enzyme from stressed leaves) and 2.15 mM (1.70 for the enzyme from stressed leaves), respectively. Enzyme from stressed leaves is not inhibited by 5 mM proline. The observed kinetic constants of GS(2) from normal and water stressed safflower seedlings are discussed in relation to the known water-stress tolerance of this crop plant.

Studies on pyridinium hexafluorostannate and its derivatives

Pyridinium hexafluorostannate, (C5H5NH)2SnF6, has been prepared by the reaction of stannous chloride or tin metal with pyridinium poly(hydrogen fluoride), PPHF, and identified by chemical analysis, IR and NMR (H-1, F-19, C-13). Making use of (C5H5NH)2SnF6 as a precursor, the following important hexafluorostannate salts have been synthesized in high yields at room temperature by ionic exchange: M2SnF6 (M = NH4, Na, K, Rb, Cs) and BaSnF6. These salts have been characterised by chemical analysis and infrared spectroscopy. Indexed powder X-ray diffraction data for Na2SnF6, Rb2SnF6 and Cs2SnF6 have been reported.

Pyridinidm Hexafluorotitanate and its Derivatives

Pyridinium hexafluorotitanate, (C5H5NH)(2)TiF6, has been prepared by the reaction of titanium metal with pyridinium poly(hydrogen fluoride), PPHF, at room temperature. Making use of (C5H5NH)(2)TiF6 as a precursor, ammonium and alkali metal hexafluorotitanates, M(2)TiF(6) (M = NH4, Na, K, Rb and Cs) have been synthesized by metathesis. These hexafluorotitanates have been characterized by chemical analyses, infrared and NMR (H-1 and F-19) spectroscopy and powder X-ray diffraction methods. Indexed powder X-ray diffraction data for Rb2TiF6 and Cs2TiF6 have been reported.

Phase transitions in triammonium hydrogen disulphate: Crystal structure of an intermediate stable phase at-90 degrees C

Triammonium hydrogen disulphate, (NH4)(3)H(SO4)(2), belongs to the family of crystal structures M3H(XO4)(2) (with M = NH4, K, Rb, Cs, and X = S, Se) which display super protonic phases at elevated temperatures, while at room temperature these are relatively poor proton conductors. The crystal structure of triammonium hydrogen disulphate has been determined by X-ray diffraction at -90 degrees C and the variation in the characteristics of the hydrogen bond is discussed in comparison with that of the structures at -110 degrees C and room temperature. It is concluded that the mechanics involving the proton migration in such systems is realised in terms of the variations in the hydrogen bond features with temperature.

Molecular self-assembly of cadmium-triazolate complexes via hydrogen bonding: Synthesis, structures and photoluminescent properties

Two new cadmium coordination polymers namely Cd(HAmTrz-COO)(4)(NH4+)(2)] 1; and Cd(HAmTrz)(2)I-2](n) 2; (HAmTrz-COOH = 3-amino-1,2,4-triazole-5-carboxylic acid), have been prepared based on HAmTrz-COOH as ligand. The crystal structures of 1 and 2 have been determined by single-crystal X-ray diffraction technique. In coordination-complex 1 four triazole ligands coordinate via N1 nitrogen leading to a tetrahedral geometry around cadmium ion, while in 2 the ligand prefers to coordinate to the metal in a bidentate bridging mode. The structures of both the coordination polymers can be envisaged as 3D hydrogen bonded networks. Thermogravimetric analysis shows that 2 is more stable than 1 owing to different coordination numbers of cadmium atoms. Photoluminescence properties of both the compounds have been investigated in the solid state. (C) 2011 Elsevier B.V. All rights reserved.

Synthesis of acicular hydrogoethite (alpha-FeOOH center dot xH(2)O; 0.1 < x < 0.22) particles using morphology controlling cationic additives and magnetic properties of maghemite derived from hydrogoethite

A method for the preparation of acicular hydrogoethite (alpha -FeOOH.xH(2)O, 0.1 < x < 0.22) particles of 0.3-1 mm length has been optimized by air oxidation of Fe( II) hydroxide gel precipitated from aqueous (NH4)(2)Fe(SO4)(2) solutions containing 0.005-0.02 atom% of cationic Pt, Pd or Rh additives as morphology controlling agents. Hydrogoethite particles are evolved from the amorphous ferrous hydroxide gel by heterogeneous nucleation and growth. Preferential adsorption of additives on certain crystallographic planes thereby retarding the growth in the perpendicular direction, allows the particles to acquire acicular shapes with high aspect ratios of 8-15. Synthetic hydrogoethite showed a mass loss of about 14% at similar to 280 degreesC, revealing the presence of strongly coordinated water of hydration in the interior of the goethite crystallites. As evident from IR spectra, excess H2O molecules (0.1- 0.22 per formula unit) are located in the strands of channels formed in between the double ribbons of FeO6 octahedra running parallel to the c- axis. Hydrogoethite particles constituted of multicrystallites are formed with Pt as additive, whereas single crystallite particles are obtained with Pd (or Rh). For both dehydroxylation as well as H-2 reduction, a lower reaction temperature (similar to 220 degreesC) was observed for the former (Pt treated) compared to the latter (Pd or Rh) (similar to 260 degreesC). Acicular magnetite (Fe3O4) was prepared either by reducing hydrogoethite (magnetite route) or dehydroxylating hydrogoethite to hematite and then reducing it to magnetite (hematite- magnetite route). According to TEM studies, preferential dehydroxylation of hydrogoethite along < 010 > leads to microporous hematite. Maghemite (gamma -Fe2O3 (-) (delta), 0 < <delta> < 0.25) was obtained by reoxidation of magnetite. The micropores are retained during the topotactic transformation to magnetite and finally to maghemite, whereas cylindrical mesopores are formed due to rearrangement of the oxygen sublattice from hexagonal to cubic close packing during the conversion of hydrogoethite to magnetite and then to maghemite. Accordingly, three different types of maghemite particles are realized: strongly oriented multicrystalline particles, single crystalline acicular particles with micropores or crystallites having mesopores. Higher values of saturation magnetization (<sigma>(s) = 74 emu g(-1)) and coercivity (H-c = 320 Oe) are obtained for single crystalline mesoporous particles. In the other cases, the smaller size of particles and larger distribution of micropores decreases sigma (s) considerably ( < 60 emu g(-1)) due to relaxation effects of spins on the surface atoms as revealed by Mossbauer spectroscopy.

The irradiation of 1:1 mixture of ammonia:carbon dioxide ice at 30 K using 1 kev electrons

In this Letter the results of an experimental investigation of 1 keV electron irradiation of a 1:1 ice mixture of NH3:CO2 at 30 K was made under ultrahigh vacuum (10(-9) mbar) conditions. Molecular products formed within the ice were detected and monitored using FTIR spectroscopy. The formation of ammonium ions (NH4+), cyanate ions (OCN-), CO was observed leading to the synthesis of ammonium carbamate (NH4NH2CO2). The consequences of these results for prebiotic chemistry in the interstellar medium and star forming regions are discussed. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.