| 1. |
- Kosa, Ladislav, et al.
(författare)
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Phase transitions of K2TaF7 within 680-800 degrees C
- 2008
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066. ; 6:1, s. 27-32
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Tidskriftsartikel (refereegranskat)abstract
- Three thermal effects on heating/cooling of K2TaF7 in the temperature interval of 680-800 degrees C were investigated by the DSC method. The values determined for the enthalpy change of the individual processes are: Delta H-transII(m)(K2TaF7; 703 degrees C) = 1.7(2) kJ mol(-1), Delta H-transI(m)(K2TaF7; 746 degrees C) = 19(1) kJ mol(-1) and Delta H-transIII(m)(K2TaF7; 771 degrees C) = 13(1) kJ mol(-1). The first thermal effect was attributed to a solid-solid phase transition; the second to the incongruent melting of K2TaF7 and the third to mixing of two liquids. These findings are supported by in situ neutron powder diffraction experiments performed in the temperature interval of 654-794 degrees C.
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| 2. |
- Langer, Vratislav, 1949, et al.
(författare)
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2-{[(3-Fluorophenyl)amino]methylidene}-3-oxobutanenitrile and 5-{[(3-fluorophenyl)amino]methylidene}-2,2-dimethyl-1,3-dioxane-4,6-dione: X-ray and DFT studies
- 2010
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Ingår i: Acta Crystallographica Section C: Crystal Structure Communications. - 0108-2701 .- 1600-5759. ; C66:8, s. o392-o395
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Tidskriftsartikel (refereegranskat)abstract
- In the crystal structures of the title compounds, C11H9FN2O, (I), and C13H12FNO4, (II), the molecules are joined pairwise via different hydrogen bonds and the constituent pairs are crosslinked by weak C-H...O hydrogen bonds. The basic structural motif in (I), which is partially disordered, comprises pairs of molecules arranged in an antiparallel fashion which enables C-H...N≡C interactions. The pairs of molecules are crosslinked by two weak C-H...O hydrogen bonds. The constituent pair in (II) is formed by intramolecular bifurcated C-H...O/O' and combined inter- and intramolecular N-H...O hydrogen bonds. In both structures, F atoms form weak C-F...H-C interactions with the H atoms of the two neighbouring methyl groups, the H...F separations being 2.59/2.80 and 2.63/2.71 Å in (I) and (II), respectively. The bond orders in the molecules, estimated using the natural bond orbitals (NBO) formalism, correlate with the changes in bond lengths. Deviations from the ideal molecular geometry are explained by the concept of non-equivalent hybrid orbitals. The existence of possible conformers of (I) and (II) is analysed by molecular calculations at the B3LYP/6-31+G** level of theory.
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| 3. |
- Langer, Vratislav, 1949, et al.
(författare)
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2-Anilinomethylene-3-oxobutanenitrile: an X-ray and density functional theory study
- 2006
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Ingår i: Acta Crystallographica Section C: Crystal Structure Communications. - 0108-2701 .- 1600-5759. ; C62:9, s. o554-o546
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Tidskriftsartikel (refereegranskat)abstract
- Molecules of the title compound, C11H10N2O, are effectively planar. In the crystal structure, they are stabilized primarily by electrostatic interactions, as the dipole moment of the molecule is 4.56 D. In addition, the molecules are linked by weak C-H...N and C-H...O hydrogen bonds. An analysis of bonding conditions in the molecule was carried out using natural bond orbital (NBO) formalism.
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| 4. |
- Langer, Vratislav, 1949, et al.
(författare)
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Crystal and electronic structure of aqua(N-salicylidene-methylester-L-glutamato)Cu(II) monohydrate
- 2004
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Ingår i: Zeitschfrift für Kristallographie. - : Walter de Gruyter GmbH. - 0044-2968. ; 219:2, s. 112-116
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Tidskriftsartikel (refereegranskat)abstract
- The absolute structure of the title compound, CuNC13H17O7, has been determined. The crystal structure consists of the molecular units Cu(N-sal-5-met-L-glu)(H2O) connected by a three-dimensional network of hydrogen bonds. The coordination polyhedron in the complex is approximately square-pyramidal with a pentacoordinated Cu(II) atom. The base of the pyramid is formed by nitrogen and oxygen atoms belonging to the molecule, while the apex of the pyramid contains a weakly bonded oxygen atom of the carboxylic group of another molecule. The B3LYP/SVP method and basis set in Gaussian98 was used for quantum chemical calculation of the nature of CuX (X = O, N) bonds. While the calculated dissociation energy of the weakly bonded crystalline water is only 17.2 kJ/mol, the bonding energy of the water molecule coordinating to the Cu atom is 62.3 kJ/mol.
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| 5. |
- Langer, Vratislav, 1949, et al.
(författare)
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Dipotassium heptafluorotantalate(V), β-K2TaF7, at 509 K
- 2006
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Ingår i: Acta Crystallographica Section E: Structure Reports Online. - 1600-5368. ; E62:4, s. i91-i93
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Tidskriftsartikel (refereegranskat)abstract
- Upon heating to 509 K, monoclinic α-K2TaF7 (P21/c) transforms to orthorhombic β-K2TaF7 (Pnma) which is composed of discrete K+ cations and TaF72- anions. In the anion, the Ta atom is sevenfold coordinated by F atoms, with the Ta-F distance varying from 1.88(2) to 1.965(19) Å. The two independent K+ cations are surrounded by F atoms positioned within 2.740(17)-2.979(10) and 2.989(17)-3.15(5) Å. Ta, both K and one of the four F atoms are located on a mirror plane, Wyckoff position 4c.
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| 6. |
- Langer, Vratislav, 1949, et al.
(författare)
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(E)-Methyl 2-[(2-fluorophenyl)aminomethylene]-3-oxobutanoate: X-ray and density functional theory (DFT) study
- 2009
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Ingår i: Acta Crystallographica Section C: Crystal Structure Communications. - 0108-2701 .- 1600-5759. ; C65:4, s. o183-o185
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Tidskriftsartikel (refereegranskat)abstract
- The title compound, C12H12FNO3, a potential precursor for fluoroquinoline synthesis, is essentially planar, with the most outlying atoms displaced from the best-plane fit through all non-H atoms by 0.163(2) and 0.118(2) Å. Molecules are arranged in layers oriented parallel to the (011) plane. The arrangement of the molecules in the structure is controlled mainly by electrostatic interactions, as the dipole moment of the molecule is 5.2 D. In addition, the molecules are linked by a weak C-H...O hydrogen bond which gives rise to chains with the base vector [1,1,1]. Electron transfer within the molecule is analysed using natural bond orbital (NBO) analysis. Deviations from the ideal molecular geometry are explained by the concept of non-equivalent hybrid orbitals.
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| 7. |
- Langer, Vratislav, 1949, et al.
(författare)
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Ethyl 1-ethyl-7-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate: X-ray and DFT studies
- 2011
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Ingår i: Acta Crystallographica Section C: Crystal Structure Communications. - 0108-2701 .- 1600-5759. ; 67:10, s. o421-o424
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Tidskriftsartikel (refereegranskat)abstract
- The basic building unit in the structure of the title compound, C14H14FNO3, is pairs of molecules arranged in an antiparallel fashion, enabling weak C-H...O interactions. Each molecule is additionally involved in π-π interactions with neighbouring molecules. The pairs of molecules formed by the C-H...O hydrogen bonds and π-π interactions form ribbon-like chains running along the c axis. Theoretical calculations based on these pairs showed that, although the main intermolecular interaction is electrostatic, it is almost completely compensated by an exchange-repulsion contribution to the total energy. As a consequence, the dominating force is a dispersion interaction. The F atoms form weak C-F...H-C interactions with the H atoms of the neighbouring ethyl groups, with H...F separations in the range 2.59-2.80 Å.
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| 8. |
- Langer, Vratislav, 1949, et al.
(författare)
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Pseudo-merohedrally twinned praseodymium hexacyanoferrate(III) tetrahydrate
- 2004
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Ingår i: Acta Crystallographica Section C: Crystal Structure Communications. - 0108-2701 .- 1600-5759. ; C60:11, s. i104-i106
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Tidskriftsartikel (refereegranskat)abstract
- Crystals of the title compound, diaquahexa-mu-cyano-ferrate(III)praseodymium(III) dihydrate, Pr[Fe(CN)6]·4H2O or [PrFe(CN)6(H2O)2]·2H2O, are twinned with three components. The Pr atom is coordinated by eight atoms, viz. six N and two symmetry-related water O atoms. The Pr polyhedron (Pr has site symmetry m2m, Wyckoff position 4c) is linked to an FeC6 octahedron (Fe located on a site with imposed 2/m symmetry, Wyckoff position 4b) through N atoms, forming an infinite array. The second (symmetry independent) water molecule lies on a mirror plane, is not included in coordination and is weakly hydrogen bonded to N atoms.
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| 9. |
- Langer, Vratislav, 1949, et al.
(författare)
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Redetermination of Na3TaF8
- 2010
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Ingår i: Acta Crystallographica Section C: Crystal Structure Communications. - 0108-2701 .- 1600-5759. ; C66:9, s. i85-i86
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of trisodium octafluoridotantalate,Na3TaF8, has been redetermined using diffractometer data collected at 153 K, resulting in more accurate bond distances and angles than obtained from a previous structure determination based on film data. The structure is built from layers running along [101], which are formed by distorted [TaF8] antiprisms and [NaF6] rectangular bipyramids sharing edgesand corners. The individual layers are separated by eightcoordinated Na ions. Two atoms in the asymmetric unit are in special positions: the Ta atom is on a twofold axis in Wyckoff position 4e and one of the Na ions lies on an inversion centre in Wyckoff site 4d.
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| 10. |
- Langer, Vratislav, 1949, et al.
(författare)
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Second-degree twinning and dynamic disorder in the crystal structure of deca-dodecasil 3R
- 2005
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Ingår i: Acta Crystallographica Section B: Structural Science. - 0108-7681 .- 1600-5740. ; B61:6, s. 627-634
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Tidskriftsartikel (refereegranskat)abstract
- The structure of deca-dodecasil 3R (DD-3R), Si120O240, a very well suited material for the synthesis of inorganic/organic composites structured on a nanometer level, has been investigated in detail. So far, a highly complicated twinning has hampered its structure description at a desirable level of accuracy. This twinning has now been resolved and a new structure determination is presented. Structure refinement in the R-3 space group revealed a large, unusually shaped atomic displacement ellipsoid for oxygen-bridging units (tetrahedra), bridging Si-O bonds shorter than expected and the linear Si-O-Si' bond angle dictated by special positions at a threefold axis. A structure model based on a statistically disordered bridging O atom improved the accuracy of the Si-O bonds of interest, but provided unacceptable O-O contacts. To solve this dilemma, ab initio NVT molecular dynamics calculations were performed to study the possible configurations. Wavelet analysis of the time variations of selected Si-O distances pointed to a synchronous shift of the whole building units (tetrahedra). Low-frequency features of the calculated phonon density of states agree well with the published INS (inelastic neutron scattering) spectra of several silica polymorphs, indicating that the nature of the disorder in DD-3R is dynamic rather than static.
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| 11. |
- Langer, Vratislav, 1949, et al.
(författare)
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Static and dynamic structure of deca-dodecasil 3R
- 2005
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Ingår i: Book of Abstracts, 2nd Algerian Crystallography Congress, Constantine, 17-21 April 2005. ; , s. 29-
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Konferensbidrag (refereegranskat)abstract
- The structure of calcined deca-dodecasil 3R (DD3R), with formula Si120O240, a very well-suited material for the synthesis of inorganic/organic composites structured on a nanometer level, was investigated in details. So far, a highly complicated twinning has hampered its structure description on a desirable level of precision and accuracy. This twinning has been resolved and a new structure determination was completed. Structure refinement done in the R-3 space group revealed a rather large Ueq of a bridging oxygen (O), shorter than expected bridging Si - O bonds and the straight Si-O-Si bond angle dictated by the atom positions at a threefold axis. A structure model based on statically displaced bridging O-atom on one hand improved accuracy of Ueq s and of the Si-O bonds of interest, but provided unacceptable O-O contacts. To explain this dilemma ab initio molecular dynamics calculations were done in order to inspect possible configurations. The finite-temperature simulations of the dynamical properties were done at 300 K and a canonical ensemble with a Nosé thermostat procedure was used. The Verlet velocity algorithm with (i) a time step ∆t = 1fs (fast sampling) and simulation time of 4 ps and (ii) ∆t = 4fs (slow sampling) and simulation time of 20 ps were used. The x,y coordinates of Si-O-Si atoms corresponded to the time-averaged structure with all three atoms are on a threefold axis. It was thus evident, that structure analysis itself cannot provide a completely true picture of DD-3R structure. To reveal possible dynamic disorder in the structure and to analyze the spatial distribution of the atoms during a longer time interval, the 20ps MD simulation was used. To un-reveal basic features hidden in such a time series wavelet denoising and non-decimating wavelet transform were applied. Synchronous changes of both Si-O distances pointed to synchronous movement of the whole building units (tetrahedra). To calculate the frequency of such a Si-O-Si bending vibration total and partial vibrational density of states were calculated from atom velocities. The interpretation of calculated spectra could be based on INS spectra of various silica polymorphs collected by several authors. It can be concluded that a good agreement of the low frequency features in the INS spectra with our results from MD indicate, that the nature of disorder in DD-3R is dynamic rather than static.
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| 12. |
- Mahmoudkhani, Amir Hussein, et al.
(författare)
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Layered strontium phenylphosphonate: synthesis, thermal properties and crystal structure from X-ray powder diffraction data
- 2002
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Ingår i: Solid State Sciences. - 1293-2558. ; 4:6, s. 873-878
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Tidskriftsartikel (refereegranskat)abstract
- Strontium phenylphosphonate, Sr(PhPO3H)2, was synthesized by the reaction of strontium carbonate and phenylphosphonic acid. The compound was structurally characterized by Rietveld refinement on X-ray powder diffraction data. It consists of a layered structure with inorganic framework of SrO8 polyhedra from which phenyl groups are pointing out. The compound is isomorphous with the already known calcium and barium phenylphosphonates. Infrared spectroscopy analysis shows the presence of (P-)O-H...O hydrogen bonds in the solid material. The thermal behavior of the compound in the range 30650°C, studied by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray powder thermodiffractometry, revealed that strontium phenylphosphonate is stable up to 330°C. The compound undergoes consequent thermal decomposition and phase transitions above 330°C temperatures until it converts to crystalline Sr(PO3)2 above 570°C.
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| 13. |
- Pritula, Ondrej, et al.
(författare)
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Neutron and X-ray Rietveld quantitative phase analysis of industrial Portland cement clinkers
- 2004
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Ingår i: Materials Structure in Chemistry, Biology, Physics and Technology. - 1211-5894. ; 11:1a, s. 181-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Weight fractions of four dominant phases (C3S, C2S, C4AF and C3A) present in five industrial clinkers were estimated by a series of neutron and X-ray Rietveld refinements. Calculated powder patterns were derived from the structural data for triclinic and monoclinic C3S, monoclinic C2S, orthorhombic C4AF and cubic C3A. Neutron diffraction data were collected with the high resolution E9 diffractometer (BENSC) using the wavelengths of 1.797Å and 2.816Å, X-ray diffraction data with a high resolution transmission diffractometer using CoKα1 radiation. Elemental composition of the samples obtained by ESEM/EDX technique were in a good agreement with the data delivered by the producers. Convergence of the refinements was remarkably different for X-ray and for neutron data. Several refinements were not completed due to numerical instabilities. Neutron refinements were found to be more stable than X-ray, but there was not any notable difference in the final estimated phases' compositions. Calculated absolute deviates of phases' weight fractions were mostly within ±10%, which for the less abundant phases corresponded to relative deviations within ±50%.
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| 14. |
- Pritula, Ondrej, et al.
(författare)
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X-ray and neutron Rietveld quantitative phase analysis of industrial Portland cement clinkers
- 2004
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Ingår i: Powder Diffraction. ; 19:3, s. 232-239
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Tidskriftsartikel (refereegranskat)abstract
- Weight fractions of four dominant phases (C3S, C2S, C4AF, and C3A) present in five industrial clinkers were estimated by a series of neutron and X-ray Rietveld refinements. Calculated powder patterns were derived from the structural data for monoclinic and triclinic C3S, monoclinic C2S, orthorhombic C4AF, cubic C3A and MgO. Neutron diffraction data were collected with the high resolution E9 diffractometer (BENSC) using two different wavelenghts, X-ray diffraction data with a high resolution transmission diffractometer. Elemental composition of the samples obtained by ESEM/EDX technique were in good agreement with the data delivered by the producers. Convergence of the refinements was remarkably different for X-ray and for neutron data. Several refinements were not completed due to numerical instabilities. Neutron refinements were found to be more stable tha X-ray, but there was not any notable difference in the final estimated phases' compositions. Calculated absolute deviates of phases' weight fractions were mostly within +-10%, which for the less abundant phases corresponded to relative deviations within +-50%.
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| 15. |
- Scholtzová, Eva, et al.
(författare)
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Crystal Structure, Infrared Spectra and DFT Study of Benzyl 2,3-Anhydro-β-D-Ribopyranoside
- 2011
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Ingår i: Journal of Chemical Crystallography. - 1074-1542 .- 1572-8854. ; 41:2, s. 167-174
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Tidskriftsartikel (refereegranskat)abstract
- The crystal structure of benzyl 2,3-anhydro-β-D-ribopyranoside is orthorhombic, P212121, Z = 4. The pyranose ring adopts the EO conformation distorted considerably to the 5HO direction. The molecules of the title compound are linked into infinite chains running along the a-axis by bifurcated O–H···O hydrogen bonds. Interaction energies of these hydrogen bonds are significantly different, ~−5.4 for the bond with the smaller and ~−1.1 kcal/mol for the bond with the larger O···O separation. The hydrogen-bond pattern is completed by the two weaker C–H···O intermolecular hydrogen bonds, aiming at the epoxy oxygen atom. IR vibrational spectrum was interpreted by means of comparison with the full list of vibrational modes predicted using DFT method in the solid state. While till 1495 cm−1 the individual bands can be reconciled with single calculated modes, the region below this limit is populated by heavily overlapped HCH, HCO, HOC, COC and HCC bending modes merged with few ν(CC) and ν(CO) modes. The respective “red” shifts of the positions of the ν(OH) bands correlate well with the size of the O···O separation.
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| 16. |
- Sladkovicova, Mariana, et al.
(författare)
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DFT and neutron diffraction study of 1,6-anhydro-beta-D-glucopyranose (levoglucosan)
- 2007
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Ingår i: Central European Journal of Chemistry. - : Walter de Gruyter GmbH. - 1895-1066. ; 5:1, s. 55-70
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Tidskriftsartikel (refereegranskat)abstract
- Geometries of 27 generated conformers of levoglucosan were optimized in vacuo at DFT level of theory combining several functionals with high quality basis sets. For the sake of comparison a reference molecular and crystal geometry obtained from 30 K single crystal neutron diffraction data was used. Analysis of the conformers' geometries revealed that in all stable conformers intramolecular two- or three centre hydrogen bonds were formed. Relative energy of the conformer, which approximated the molecule in the crystal structure the most, was only similar to 3 kcal/mol higher, than the energy of the most stable conformer in vacuo. The largest discrepancies between the geometries calculated in vacuo and experimental geometry concentrated in the vicinity of anomeric C1. These differences were reduced by involving O1 to intermolecular hydrogen bond using a simple model of the respective hydrogen bond in the crystal.
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| 17. |
- Smrcok, Lubomir, et al.
(författare)
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Intramolecular hydrogen bond and proton transfer in 3-(2-benzimidazolylthio)-2,4-pentanedione. Crystallographic evidence and theoretical calculations
- 2002
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Ingår i: Zeitschfrift für Kristallographie. - : Walter de Gruyter GmbH. - 0044-2968. ; 217:5, s. 217-222
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Tidskriftsartikel (refereegranskat)abstract
- Crystal structure of the title compound is orthorhombic, Pbca, a=7.8689(2)Å, b=9.6519(3)Å, c=31.3579(9)Å. The structure was solved by direct methods and refined by a full-matrix least squares procedure to final R (all)=0.0682 for 2853 unique diffractions merged from 24459 measured at 183(2)K. The molecule is formed by two planar moieties joined through an atom of sulphur. The short intramolecular O...O contact is 2.430(2)Å, the intramolecular hydrogen bond is slightly asymmetric. Theoretical ab initio calculations done at B3LYP/SVP and ONIOM(MP2/SVP:B3LYP/SVP) levels showed that the experimental geometry of pentanedione pseudoring is close to the geometry corresponding to a transition state on the asymmetric potential energy curve. Calculated energy difference between two minima is only 4.72 kJ/mol and the energy barrier 6.02 kJ/mol, which agrees well to ~6.6kJ/mol found in microwave spectroscopic study of malonaldehyde.
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| 18. |
- Smrcok, Lubomir, et al.
(författare)
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On hydrogen bonding in 1,6-anhydro-β-D-glucopyranose (levoglucosan): X-ray and neutron diffraction and DFT study
- 2006
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Ingår i: Acta Crystallographica Section B: Structural Science. - 0108-7681 .- 1600-5740. ; B62:5, s. 912-918
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Tidskriftsartikel (refereegranskat)abstract
- The geometry of hydrogen bonds in 1,6-anhydro-β-D-glucopyranose (levoglucosan) is accurately determined by refinement of time-of-flight neutron single-crystal diffraction data. Molecules of levoglucosan are held together by a hydrogen-bond array formed by a combination of strong O-H...O and supporting weaker C-H...O bonds. These are fully and accurately detailed by the neutron diffraction study. The strong hydrogen bonds link molecules in finite chains, with hydroxyl O atoms acting as both donors and acceptors of hydroxyl H atoms. A comparison of molecular and solid-state DFT calculations predicts red shifts of O-H and associated blue shifts of C-H stretching frequencies due to the formation of hydrogen bonds in this system.
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| 19. |
- Smrcok, Lubomir, et al.
(författare)
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X-ray, synchrotron, and neutron diffraction analysis of Roman cavalry parade helmet fragment
- 2010
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Ingår i: Crystal Research and Technology. - : Wiley. - 0232-1300 .- 1521-4079. ; 45:10, s. 1025-1031
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Tidskriftsartikel (refereegranskat)abstract
- A partially corroded fragment of the neck guard of a Roman cavalry helmet excavated in the former military camp of Gerulata, a part of the Limes Romanus on the River Danube, was analysed by laboratory X-ray, synchrotron and neutron powder diffraction. The approximate phase composition determined by the neutron diffraction of the bulk, 82% (wt) of the copper alloy phase, 12 % (wt) of cuprite and 6% of nantokite indicate a significant degree of corrosion of the artefact. Elemental EDX analysis of cleaned surface showed that the chemical composition of the original alloy is 78 to 82 % (wt) of Cu and 21.4 to 16.5 % of Zn with minute amounts of Sn, Si and S. High contents of Cu and Zn with the negligible amount of Sn showed that the body of the helmet was made of brass and not of bronze as expected before. The amount of zinc in the copper alloy calculated from the refined lattice parameter agrees fairly well with the value determined by EDX. The most abundant phase in the synchrotron powder diffraction pattern of the corrosion products scrapped from the artefact is cuprite, but presence of atacamite, malachite, brochantite, nantokite, mixed Cu-Zn hydroxyl carbonates and probably also of simonkolleite (Zn5(OH)8Cl2·H2O) have been detected. In contrast, the X-ray pattern taken directly from the surface of the artefact is dominated by atacamite with some traces of malachite and quartz. Because the penetration depth of laboratory X-rays is in order of tens of microns, the phase analysis based only on a diffraction pattern taken from a surface can lead to erroneous conclusions concerning the phase composition of the patina.
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| 20. |
- Smrcok, Lubomir, et al.
(författare)
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γ-Alumina: a single-crystal X-ray diffraction study
- 2006
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Ingår i: Acta Crystallographica Section C: Crystal Structure Communications. ; C62:9, s. i83-i84
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Tidskriftsartikel (refereegranskat)abstract
- The structure of γ-alumina (Al21+1/3◊2+2/3O32) crystals obtained as a product of a corrosion reaction between β-sialon and steel was refined in the space group Fd-3m. The oxygen sublattice is fully occupied. The refined occupancy parameters are 0.83(3), 0.818(13), 0.066(14) and 0.044(18) for Al ions in 8a, 16d, 16c and 48f positions, respectively. The Al ions are distributed over octahedral and tetrahedral sites ina 63:37 ratio, with 6% of all Al ions occupying non-spinelpositions.
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| 21. |
- Smrcok, L'ubomir, et al.
(författare)
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1,4-diazabicyclo[2.2.2]octane-1,4-diium dihydrogen phosphate monohydrate from X-ray and neutron data
- 2009
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Ingår i: Zeitschrift fur Kristallographie. - : Walter de Gruyter GmbH. - 0044-2968. ; 224:3, s. 174-178
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Tidskriftsartikel (refereegranskat)abstract
- The three-dimensional skeleton of the structure of the title compound is formed by the chains of the hydrogen phosphate units running approximately parallel to the c-axis. The units are coupled to the chains by three types of hydrogen bonds: strong symmetric O-H-O (O center dot center dot center dot O = 2.424(4) and 2.425(4) angstrom) and the moderate P-O-H center dot center dot center dot O-P and P-O center dot center dot center dot(H2O)center dot center dot center dot O-P, respectively. Molecules of the doubly protonated 1,4-diazabicyclo[2.2.2]octane moieties are placed in the voids and in addition for electrostatic interactions they are also hydrogen bonded to the chains of PO4 tetrahedra. The DC conductivity measured at the room temperature along the b-axis is very low (approximate to 7 x 10(-11) S cm(-1)), while in the perpendicular plane it is for more than two or three orders higher and the nonlinear current vs. potential dependence was registered.
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