Crystal structure and properties ofcatena-poly[manganese(II)-μ-dichloro-μ-L-proline-k 2 o,o′] monohydrate

The crystal structure and some physico-chemical properties of MnCl₂·Pro·H₂O (Pro=L-proline) were studied. This compound is stable up to approximately 313 K. Upon heating the complex loses a molecule of water and is transformed into the oxide in two steps. The IR spectrum was recorded. The compound crystallizes in the orthorhombic space groupP2₁2₁2₁ witha=7.112(2) Å,b=10.196(2) Å,c=13.249(3) Å andZ=4. The manganese atoms in the polymeric chain are bridged by two chlorine atoms and oxygen atoms from the carboxylate group of L-proline. The Mn?Cl bond distances range from 2.535(1) Å to 2.581(1) Å, the Mn?O bond distances range from 2.135(2) Å to 2.153(2) Å and Mn?Mn bond distances are 3.556(1) Å. One molecule of water is hydrogen-bonded with a nitrogen atom of the L-proline ring.     

Multilayer graphene stacks grown by different methods-thickness measurements by X-ray diffraction, Raman spectroscopy and optical transmission

X-ray diffraction, Raman spectroscopy and Optical absorption estimates of the thickness of graphene multi layer stacks (number of graphene layers) are presented for three different growth techniques. The objective of this work was focused on comparison and reconciliation of the two already widely used methods for thickness estimates (Raman and Absorption) with the calibration of the X-ray method as far as Scherer constant K is concerned and X-ray based Wagner-Aqua extrapolation method.     

Urea-glutaric acid (2∶1) structural aggregates as building blocks for crystal engineering

The crystal structure of a 21 urea-glutaric acid cocrystal has been determined. The crystal is monoclinic:C2lc,a=11.954(5),b=10.932(1),c=9.078(3) Å, =97.86(3)°, withZ=4. The formula unit is a hydrogen-bonded heterotrimeric aggregate consisting of one acid subunit locked between two identical urea subunits. The symmetric arrangement from both sides of the acid allows for retaining the twofold axis primary inherent for the glutaric acid. An additional symmetry element (inversion center) is introduced during the aggregate self-association into one-dimensional chains, which are further organized through glide operations into a well-defined three-dimensional, hydrogen-bonded crystal network.Deceased on June 10, 1992.     

The influence of the growth rate and V/III ratio on the crystal quality of InGaAs/GaAs QW structures grown by MBE and MOCVD methods

The influence of the growth rate and V/III ratio on the crystal quality of In_0.2GaAs/GaAs quantum well structures was examined. The investigated heterostructures were grown by molecular beam epitaxy (MBE) and metalorganic chemical vapour deposition (MOCVD). Reflection high energy electron diffraction (RHEED), photoluminescence measurements (PL), high-resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM) were applied for evaluation of the interfaces smoothness and the overall layer quality. Comprehensive characterisation of InGaAs/GaAs structures allowed us to establish optimal values of analysed technological parameters. Moreover, the comparison between the results obtained for samples grown by two different epitaxial techniques allowed us to find, which of the analysed growth parameters has the strongest influence on the quality of MBE and MOCVD grown structures. In contrast with the growth temperature and the interruption time, which in different manner impact on the crystal quality of QWs obtained by different method, the growth rate and the V/III ratio play similar role in both epitaxial techniques.     

Structure of phosphonium rhenates(VII)

Four phosphonium rhenates(VII) were prepared and crystallized: (A) 1,2-bis (triphenylphosphonium)ethane rhenate(VII) (Pī, a=8.298(2), b=10.638(3), c= 11.242(3) ?, α=64.96(2), β=80.49(2), γ=88.17(2)°), (B) methyltriphenylphosphonium rhenate(VII) (Pca2₁, a=15.096(3), b=12.627(3), c=19.353(3) ?), (C) benzyltriphenylphosphonium rhenate(VII) (Pī, a=9.648(2), b=11.689(2), c=20.806(3) ?, α=88.44(2), β=84.63(2), γ=77.33(3)°), and (D) orthorhombic form of (iodomethyl)triphenylphosphonium rhenate(VII) (Pca2₁, a=14.952(3), b=13.120(3), c=20.603(4) ?). Each crystal structure consists of separate phosphonium cations and rhenate(VII) anions. In A centrosymmetric 1,2-bis(triphenylphosphonium)ethane cations form layers perpendicular to [011]. In B the cations are set in chains along [100] forming layers perpendicular to [001]. In C two symmetrically-independent cations form double columns along [100] and these columns are arranged in puckered layers perpendicular to [001]. D is almost isomorphous to B. The crystal structures are stabilised by weak C–H⋯O hydrogen bonds as well as phenyl rings interactions. In all crystal structures supramolecular motifs of phenyl rings embraces could be distinguished.     

The stereochemistry of quaternary N-methyl sparteinium cations, their derivatives, stereoisomers and analogues : Part II. Molecular and crystal structure, and IR spectra of methiodide and methperchlorate of 2-oxosparteine

The crystal and molecular structures of two quarternary salts of 2-oxosparteine (II), the methiodide (IICH⁺₃ • I⁻) and the methperchlorate (IICH⁺₃ • ClO⁻₄) have been determined on the basis of X-ray and IR data. The studies were performed by analogy to previously investigated quaternary salts of sparteine (I), the methiodide (ICH⁺₃ • I⁻) and the methperchlorate (ICH⁺₃ • ClO⁻₄). As expected, the configurations and conformations of cationic parts within the two pairs of quaternary salts are identical, except for the structure of their A/B fragments, which in ICH⁺₃ cations have the character of tertiary amines, but in IICH⁺₃ that of lactams.

On the basis of accumulated X-ray and IR data the similarities and differences in the modes of interaction of perchlorate and iodide anions with quaternary cations, and especially with their N⁺---CH₃ groups are discussed. In this discussion are also included the methiodide and methperchlorate of -isosparteine: IIICH⁺₃ • X⁻ (X⁻ = I⁻ or ClO⁻₄) where N⁺---CH₃ groups are cisoidally oriented to the basic nitrogen atoms. The most interesting observations are as follows: (i) When N⁺---CH₃ groups are easily accessible for direct quasi hydrogen bonding interactions with counter anions and when other positive charged groups, for instance lactam groups, are absent in quaternary cations, perchlorate anions interact more strongly than the iodide anions and in consequence introduce conformational changes into the ring with N⁺---CH₃ group as well as into further rings. (ii) Perchlorate and iodide anions interact with N⁺---CH₃ groups similarly and very weakly if at all, when the N⁺---CH₃ groups are for steric reasons inaccessible to counter anions or when in quaternary cations there are additional groups which attract the counter anions electrostatically. The last mechanism operates in both quaternary salts of 2-oxosparteine and this is the reason why their monocrystals are isosteric and IR spectra almost identical. (iii) The sterically hindered N⁺---CD₃ groups in both IIICD⁺₃ • X⁻ salts give rise in their IR spectra to two doubles of sharp, well resolved bands which indicate the presence of two different rotamers stabilized by two modes of weak intramolecular hydrogen bonds with basic N atoms. (iv) In IIICH⁺₃ • X⁻ and IIICD⁺₃ • X⁻ salts the perchlorate and iodide anions do not interact at all with the rotating and vibrating N⁺---CH₃ (N⁺---CD₃) group but the structures of these salts are not isosteric since the perchlorate anions interact more strongly than iodide anions with the A/B fragment of the IIICH⁺₃ cations. This is visible from the shapes and intensities of the so-called “trans” band in the IR spectra of both salts.     

Analysis of poly-β-hydroxybutyrate in environmental samples by GC-MS/MS

Application of gas chromatography-mass spectrometry (GC-MS) can significantly improve trace analyses of compounds in complex matrices from natural environments compared to gas chromatography only. A GC-MS/MS technique for determination of poly-β-hydroxybutyrate (PHB), a bacterial storage compound, has been developed and used for analysis of two soils stored for up to 319 d, fresh samples of sewage sludge, as well as a pure culture of Bacillus megaterium. Specific derivatization ¶of β-hydroxybutyrate (3-OH C_4?:?0) PHB monomer units by N-tert-butyl-dimethylsilyl-N-methyltrifluoracetamide (MTBSTFA) improved chromatographic and mass spectrometric properties of the analyte. The diagnostic fragmentation scheme of the derivates tert-butyldimethylsilyl ester and ether of β-hydroxybutyric acid (MTBSTFA-HB) essential for the PHB identification was shown. The ion trap MS was used, therefore the scan gave the best sensitivity and with MS/MS the noise decreased, so the S/N was better and also with second fragmentation the amount of ions increased compared to SIM. The detection limit for MTBSTFA-HB by GC-MS/MS was about 10^–13 g μL^–1 of injected volume, while by GC (FID) and GC-MS (scan) it was around 10^–10 g μL^–1 of injected volume. Sensitivity of GC-MS/MS measurements of PHB in arable soil and activated sludge samples was down to 10 pg of PHB g^–1 dry matter. Comparison of MTBSTFA-HB detection in natural soil sample by GC (FID), GC-MS (scan) and by GC-MS/MS demonstrated potentials and limitations of the individual measurement techniques.     

Azinyl sulfides. L.

The title compound, C₁₉H₁₃N₃S, is folded, with the central ring in a boat conformation. The folding angle between the two quinoline rings is 150.2 (1)°. The 14‐methyl substituent is in a quasi‐axial orientation with respect to the thia­zine ring. The S?N—C_methyl angle is 120.1 (1)°.     

Flotation—spectrophotometric determination of osmium with thiocyanate and methylene blue

A sensitive flotation—spectrophotometric method, based on the ion associate formed by the anionic thiocyanate complex of osmium with the basic dye methylene blue (MB) is described. The ion associate precipitates when the aqueous solution is shaken with toluene, and the separated and washed compound is dissolved in acetone. The molar absorptivity is 2.2 × 10⁵ l mol^-1 cm^-1 at 655 nm. Beer's law is obeyed. The molar ratio of Os:SCN:MB in the separated and washed ion associate is 1:6:3. Ruthenium reacts similarly. The method is applied to the determination of traces of osmium in crucible platinum after separation of osmium by distillation as tetroxide.