Preparation and thermal decomposition of solid state cobalt, nickel, copper and zinc chelates of ethylenediaminetetraacetic acid

Solid state chelates of general formula H-2[M(EDTA)] . nH2O, where M is Co, Ni, Cu or Zn, and EDTA is ethylenediaminetetraacetate, were prepared. Thermogravimetry-derivative thermogravimetry (TG-DTG), differential thermal analysis (DTA) and complexometry were used to characterize and to study the thermal stability and thermal decomposition of these compounds.

Synthesis, characterisation and thermal behaviour of solid state compounds of 4-methylbenzylidenepyruvate with heavier trivalent lanthanides and yttrium(III)

Solid state Ln-4-Me-BP compounds, where Ln stands for heavier trivalent lanthanides (gadolinium to lutetium) and yttrium(III) and 4-Me-BP is 4-methylbenzylidenepyruvate (CH3-C6H4-CH=CH-COCOO-), have been synthesized. Elemental analysis, complexometry, X-ray powder diffractometry, infrared spectroscopy and simultaneous thermogravimetry-differential thermal analysis (TG-DTA), have been used to characterise and to study the thermal behaviour of these compounds. The results provided information concerning the stoichiometry, crystallinity, ligand's denticity, thermal stability and thermal decomposition. © 2002 Elsevier Science B.V. All rights reserved.

Solid-state 2-methoxybenzoates of light trivalent lanthanides : SSSynthesis, characterization and thermal behaviour

Solid-state LnL(3) compounds, where L is 2-metboxybenzoate and Ln is light trivalent lanthanides, have been synthesized. Thermogravimetry (TG), differential scanning calorimetty (DSC), X-ray powder diffractometry, infrared spectroscopy and elementary analysis were used to characterize and to study the thermal behaviour of these compounds. The results led to information on the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds. on heating these complexes decompose in three (Ce, Pr) or five (La, Nd, Sm) steps with the formation of the respective oxide: CeO2, Pr6O11 and Ln(2)O(3) (Ln=La, Nd, Sm) as final residues. The theoretical and experimental spectroscopic study suggests predominantly the ionic bond between the ligand and metallic center.

Preparation and thermal decomposition of solid state lanthanide(III) and yttrium(III) chelates of ethylenediaminetetraacetic acid

Solid state chelates of general formula H[Ln(EDTA)] · nH2O (Ln = trivalent lanthanide (except for promethium) or yttrium; EDTA = ethylenediaminetetraacetate) were prepared. Thermogravimetry, differential thermal analysis. X-ray diffraction and complexometry were used to characterize and study the thermal stability and thermal decomposition of these compounds. © 1993.

Thermal and crystalographic studies of mixture La2O3-SrO prepared via reaction in the solid state

The compound obtained via state solid reaction of the La2O3 and SrO oxides and expose the room atmosphere shows the crystallographic data of the compound reported as La2SrOx. However, thermogravimetric, differential thermal analysis and XRD with controlled temperature indicated that the stoichiometry of the compound is 2La(OH)(3)-SrCO3, which structural parameters were determined by using the Rietveld method. It was verified that when the compound exposed at room atmosphere, the mixture oxide absorbs H2O and CO2 producing hydroxide and carbonate of lanthanum and strontium, respectively, which thermal decomposition occurs by the same steps, producing the La2O3-SrO.

The preparation and thermal decomposition of some metal compounds of 4-dimethylaminobenzylidenepyruvate in the solid state

Solid M-DMBP compounds, where M represents Mg(II), Ca(II), Sr(II), Ba(II), Ni(II), Cu(II), Zn(II), Fe(III), La(III), Th(IV), and DMBP is 4-dimethylaminobenzylidenepyruvate, have been prepared. Thermogravimetry-derivative thermogravimetry (TG-DTG), differential scanning calorimetry (DSC) and other methods of analysis have been used to characterize and to study the thermal stability and thermal decomposition of these compounds. © 1995.

Solid-state compounds of 2-methoxybenzylidenepyruvate with some bivalent metal ions - Synthesis, characterization and thermal behavior studies

Solid-state M-2-MeO-BP compounds, where M represents bivalent Mn, Fe, Co, Ni, Cu, Zn and 2-MeO-BP is 2-methoxybenzylidenepyruvate have been synthesized. Simultaneous thermogravinietry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal stability and thermal decomposition of these compounds. The results led to information about the composition, dehydration, crystallinity and thermal decomposition of the isolated compounds.

The preparation and thermal decomposition of solid state compounds of 4-dimethylaminobenzylidenepyruvate and trivalent lanthanides and yttrium

Solid state Ln-DMBP compounds, where Ln represents trivalent lanthanides (except for promethium) and yttrium, and DMBP is 4-dimethylaminobenzylidenepyruvate, were prepared. Thermogravimetry (TG), differential thermal analysis (DTA), and other methods of analysis were used to characterize and to study the thermal stability and thermal decomposition of these compounds. © 1993.

Incorporation of PbF2 into Heavy Metal Oxide Borate Glasses. Structural Studies by Solid State NMR

A series of heavy metal oxide (HMO) glasses with composition 26.66B(2)O(3)-16GeO(2)-4 Bi2O3-(53.33-x)PbO-xPbF2 (0 <= x <= 40) were prepared and characterized with respect to their bulk (glass transition and crystallization temperatures, densities, molar volumes) and spectroscopic properties. Homogeneous glasses are formed up to x = 30, while crystallization of beta-PbF2 takes place at higher contents. Substitution of PbO by PbF2 shifts the optical band gap toward higher energies, thereby extending the UV transmission window significantly toward higher frequencies. Raman and infrared absorption spectra can be interpreted in conjunction with published reference data. Using B-11 and F-19 high-resolution solid state NMR as well as B-11/F-19 double resonance methodologies, we develop a quantitative structural description of this material. The fraction of four-coordinate boron is found to be moderately higher compared to that in glasses with the same PbO/B2O3 ratios, suggesting some participation of PbF2 in the network transformation process. This suggestion is confirmed by the F-19 NMR spectra. While the majority of the fluoride ions is present as ionic fluoride, similar to 20% of the fluorine inventory acts as a network modifier, resulting in the formation of four-coordinate BO3/2F- units. These units can be identified by F-19{B-11} rotational echo double resonance and B-11{F-19} cross-polarization magic angle spinning (CPMAS) data. These results provide the first unambiguous evidence of B-F bonding in a PbF2-modified glass system. The majority of the fluoride ions are found in a lead-dominated environment. F-19-F-19 homonuclear dipolar second moments measured by spin echo decay spectroscopy are quantitatively consistent with a model in which these ions are randomly distributed within the network modifier subdomain consisting of PbO, Bi2O3, and PbF2. This model, which implies both the features of atomic scale mixing with the network former borate species and some degree of fluoride ion clustering is consistent with all of the experimental data obtained on these glasses.

Transverse pseudo-nonlinear effects measured in solid-state laser materials using a sensitive time-resolved technique

We present a detailed study of the Baryscan technique, a new efficient alternative to the widespread Z-scan technique which has been demonstrated [Opt. Lett. 36:8, 2011] to reach among the highest sensitivity levels. This method is based upon the measurement of optical nonlinearities by means of beam centroid displacements with a position sensitive detector and is able to deal with any kind of lensing effect. This technique is applied here to measure pump-induced electronic refractive index changes (population lens), which can be discriminated from parasitic thermal effects by using a time-resolved Baryscan experiment. This method is validated by evaluating the polarizability variation at the origin of the population lens observed in the reference Cr3+:GSGG laser material.

Characterization of a thermostable extracellular tannase produced under submerged fermentation by Aspergillus ochraceus

Background: Tannases are enzymes that may be used in different industrial sectors as, for example, food and pharmaceutical. They are obtained mainly from microorganisms, as filamentous fungi. However, the diversity of fungi stays poorly explored for tannase production. In this article, Aspergillus ochraceus is presented as a new source of tannase with interesting features for biotechnological applications. Results: Extracellular tannase production was induced when the fungus was cultured in Khanna medium with tannic acid as carbon source. The extracellular tannase was purified 9-fold with 2% recovery and a single band corresponding to 85 kDa was observed in SDS-PAGE. The native apparent molecular mass was estimated as 112 kDa. Optima of temperature and pH were 40 degrees C and 5.0, respectively. The enzyme was fully stable from 40 degrees C to 60 degrees C during 1 hr. The activity was enhanced by Mn2+ (33-39%) and NH4+ (15%). The purified tannase hydrolyzed tannic acid and methyl gallate with Km of 0.76 mM and 0.72 mM, respectively, and Vmax of 0.92 U/mg protein and 0.68 U/mg protein, respectively. The analysis of a partial sequence of the tannase encoding gene showed an open read frame of 567 bp and a sequence of 199 amino acids were predicted. TLC analysis revealed the presence of gallic acid as a tannic acid hydrolysis product. Conclusion: The extracellular tannase produced by A. ochraceus showed distinctive characteristics such as monomeric structure and activation by Mn2+, suggesting a new kind of fungal tannases with biotechnological potential. Further, it was the first time that a partial gene sequence for A. ochraceus tannase was described.

Molecular dynamics of poly(Ethylene Glycol) intercalated in clay, studied using 13C solid-state NMR

In this study, Cross-Polarization Magic-angle Spinning CP/MAS, 2D Exchange, Centerband-Only Detection of Exchange (CODEX), and Separated-Local-Field (SLF) NMR experiments were used to study the molecular dynamics of poly(ethylene glycol) (PEG) inside Hectorite/PEG intercalation compounds in both single- and double-layer configurations. The results revealed that the overall amplitude of the motions of the PEG chain in the single-layer configuration is considerably smaller than that observed for the double-layer intercalation compound. This result indicates that the effect of having the polymer chain interacting with both clay platelets is to produce a substantial decrease in the motional amplitudes of those chains. The presence of these dynamically restricted segments might be explained by the presence of anchoring points between the clay platelets and the PEG oxygen atoms, which was induced by the Na+ cations. By comparing the PEG motional amplitudes of the double-layered nanocomposites composed of polymers with different molecular weights, a decrease in the motional amplitude for the smaller PEG chain was observed, which might also be understood using the presence of anchoring points.

ScPdZn and ScPtZn with YAlGe type structure: group-subgroup relation and 45Sc solid state NMR spectroscopy

The intermetallic compounds ScPdZn and ScPtZn were prepared from the elements by high-frequency melting in sealed tantalum ampoules. Both structures were refined from single crystal X-ray diffractometer data: YAlGe type, Cmcm, a = 429.53(8), b = 907.7(1), c = 527.86(1) pm, wR2 = 0.0375, 231 F2 values, for ScPdZn and a = 425.3(1), b = 918.4(2), c = 523.3(1) pm, wR2 = 0.0399, 213 F2 values for ScPtZn with 14 variables per refinement. The structures are orthorhombically distorted variants of the AlB2 type. The scandium and palladium (platinum atoms) build up ordered networks Sc3Pd3 and Sc3Pt3 (boron networks) which are slightly shifted with respect to each other. These networks are penetrated by chains of zinc atoms (262 pm in ScPtZn) which correspond to the aluminum positions, i.e. Zn(ScPd) and Zn(ScPt). The corresponding group-subgroup scheme and the differences in chemical bonding with respect to other AlB2-derived REPdZn and REPtZn compounds are discussed. 45Sc solid state NMR spectra confirm the single crystallographic scandium sites. From electronic band structure calculations the two compounds are found metallic with free electron like behavior at the Fermi level. A larger cohesive energy for ScPtZn suggests a more strongly bonded intermetallic than ScPdZn. Electron localization and overlap population analyses identify the largest bonding for scandium with the transition metal (Pd, Pt).

Heteronuclear recoupling methods in solid-state NMR

This thesis is focused on the development of heteronuclear correlation methods in solid-state NMR spectroscopy, where the spatial dependence of the dipolar coupling is exploited to obtain structural and dynamical information in solids. Quantitative results on dipolar coupling constants are extracted by means of spinning sideband analysis in the indirect dimension of the two-dimensional experiments. The principles of sideband analysis were established and are currently widely used in the group of Prof. Spiess for the special case of homonuclear 1H double-quantum spectroscopy. The generalization of these principles to the heteronuclear case is presented, with special emphasis on naturally abundant 13C-1H systems. For proton spectroscopy in the solid state, line-narrowing is of particular importance, and is here achieved by very-fast sample rotation at the magic angle (MAS), with frequencies up to 35 kHz. Therefore, the heteronuclear dipolar couplings are suppressed and have to be recoupled in order to achieve an efficient excitation of the observed multiple-quantum modes. Heteronuclear recoupling is most straightforwardly accomplished by performing the known REDOR experiment, where pi-pulses are applied every half rotor period. This experiment was modified by the insertion of an additional spectroscopic dimension, such that heteronuclear multiple-quantum experiments can be carried out, which, as shown experimentally and theoretically, closely resemble homonuclear double-quantum experiments. Variants are presented which are well-suited for the recording of high-resolution 13C-1H shift correlation and spinning-sideband spectra, by means of which spatial proximities and quantitative dipolar coupling constants, respectively, of heteronuclear spin pairs can be determined. Spectral editing of 13C spectra is shown to be feasible with these techniques. Moreover, order phenomena and dynamics in columnar mesophases with 13C in natural abundance were investigated. Two further modifications of the REDOR concept allow the correlation of 13C with quadrupolar nuclei, such as 2H. The spectroscopic handling of these nuclei is challenging in that they cover large frequency ranges, and with the new experiments it is shown how the excitation problem can be tackled or circumvented altogether, respectively. As an example, one of the techniques is used for the identification of a yet unknown motional process of the H-bonded protons in the crystalline parts of poly(vinyl alcohol).

Structure and dynamics of supramolecular assemblies studied by advanced solid-state NMR spectroscopy

Ziel der vorliegenden Arbeit ist die Aufklärung von Struktur und Dynamik komplexer supramolekularer Systeme mittels Festkörper NMR Spektroskopie. Die Untersuchung von pi-pi Wechselwirkungen, welche einen entscheidenden Einfluss auf die strukturellen und dynamischen Eigenschaften supra- molekularer Systeme haben, hilft dabei, die Selbst- organisationsprozesse dieser komplexen Materialien besser zu verstehen. Mit dipolaren 1H-1H and 1H-13C Wiedereinkopplungs NMR Methoden unter schnellem MAS können sowohl 1H chemische Verschiebungen als auch dipolare 1H-1H und 1H-13C Kopplungen untersucht werden, ohne dass eine Isotopenmarkierung erforderlich ist. So erhält man detaillierte Informationen über die Struktur und die Beweglichkeit einzelner Molekül- segmente. In Verbindung mit sogenannten nucleus independent chemical shift (NICS) maps (berechnet mit ab-initio Methoden) lassen sich Abstände von Protonen relativ zu pi-Elektronensystemen bestimmen und so Strukturvorschläge ableiten. Mit Hilfe von homo- und heteronuklearen dipolaren Rotationsseitenbandenmustern könnenaußerdem Ordnungs- parameter für verschiedene Molekülsegmente bestimmt werden. Die auf diese Weise gewonnenen Informationen über die strukturellen und dynamischen Eigenschaften supramolekularer Systeme tragen dazu bei, strukturbestimmende Molekül- einheiten und Hauptordnungsphänomene zu identifizieren sowie lokale Wechselwirkungen zu quantifizieren, um so den Vorgang der Selbstorganisation besser zu verstehen.