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  • 1
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of crystalline β-cyclodextrin dodecahydrate at 293 K and 120 K (1987)
    Springer
    European biophysics journal 15 (1987), S. 211-224 
    Details
    ISSN: 1432-1017
    Keywords: β-cyclodextrin dodecahydrate ; molecular dynamics simulation ; hydrogen bonds ; empirical force field ; water molecule diffusion ; positional disorder
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Molecular dynamics (MD) simulations for crystalline β-cyclodextrin dodecahydrate (β-CD) at two different temperatures, 293 K and 120 K, have been performed using the GROMOS program package. The calculated structural properties are compared to those obtained from neutron diffraction studies of this system at the quoted temperatures. The simulation was carried out over a period of 20 ps on four unit cells containing 8 β-CD molecules and 96 water molecules, whereby all atoms were allowed to move. At room temperature, the experimental positions of the (non-hydrogen) glucose atoms are reproduced within 0.034 nm, a value which is smaller than the experimental (0.041 nm) or simulated (0.049 nm) overall root mean square (rms) positional fluctuation. The corresponding numbers for the low temperature study are 0.046 nm, 0.019 nm and 0.022 nm. At both temperatures the experimentally observed degree of anisotropy of the atomic motions is also found in the simulations. The comparison of a variety of structural properties leads to the conclusion that the molecular model and force field used are able to simulate the cyclodextrin system very well. Experimentally observed differences in properties as a function of number of glucose units in the CD molecule (α-CD, 6 versus β-CD, 7) and as a function of temperature are qualitatively reproduced by the simulations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577069
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  • 2
    Electronic Resource
    Electronic Resource
    A molecular dynamics simulation of crystalline α-cyclodextrin hexahydrate (1987)
    Springer
    European biophysics journal 15 (1987), S. 197-210 
    Details
    ISSN: 1432-1017
    Keywords: α-cyclodextrin hexahydrate ; molecular dynamics simulation ; empirical force field ; hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The structure of crystalline α-cyclodextrin (α-CD) hexahydrate, form I (C36H60O30·6H2O, space group P212121) is experimentally so well determined by X-ray and by neutron diffraction analyses that the positions of all the hydrogen atoms are available. This provides an opportunity for testing an empirical force field that is currently used in simulations of protein and nucleic acid structures by performing molecular dynamics studies employing the GROMOS program package on a system of 4 unit cells containing 16 α-CD molecules and 96 water molecules. A detailed comparison of the simulated and experimentally determined crystal structures shows that the experimental positions of the α-CD atoms are reproduced within 0.025 nm, well within the overall experimental accuracy of 0.036 nm; that the water molecules are on average within 0.072 nm from their experimental sites, with two thirds reproduced within experimental accuracy by the calculations; that high correlation is produced, between the occurrence of simulated and experimentally observed hydrogen bonds. The good agreement between simulated and experimental results suggests that the tested force field is reliable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00577068
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  • 3
    Electronic Resource
    Electronic Resource
    Zur Kenntnis der Chemie der Metallcarbonyle in flüssigem Ammoniak. IV. Über Neue Substitutionsprodukte des Cr(CO)6 mit aromatischen Aminen (1959)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 300 (1959), S. 51-60 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: By interaction of alkali pentacarbonyl chromates(-II) with aromatic mono-, di-, and triamines at room temperature only pentacarbonyl amine chromium(0) compounds are formed. Wheras m- and p-phenylene diamine are linked with two and 1, 3, 5-triaminobenzene with three Cr(CO)5-groups, o-phenylene diamine forms a corresponding compound with only one Cr(CO)5-group. Unlike ethylene diamine or cyclohexane diamine(1,2) o-phenylene diamine does not give a tetracarbonyl chromium(0) compound.
    Notes: Bei der Umsetzung von Alkali-pentacarbonyl-chromaten(-II) mit wäßrigen Lösungen von aromatischen Mono-, Di- und Triaminen bei gewöhnlicher Temperatur erhält man stets Pentacarbonyl-amin-chrom(0)-verbindungen, die sich als echte Substitutions-produkte des Cr(CO)6 erweisen. Während m- und p-Phenylendiamin zwei und 1,3,5-Triaminobenzol drei Cr(CO)5-Gruppen zu binden vermögen, erhält man im Falle des o-Phenylendiamins eine entsprechende Verbindung mit nur einer Cr(CO)5-Gruppe. Insbesondere entsteht bei letzterem - im Gegensatz zum Äthylendiamin - keine Tetracarbonyl-chrom(0)-verbindung. Eine solche bildet sich hingegen, wenn man an Stelle des o-Phenylendiamins das hydrierte o-Phenylendiamin, also Cyclohexandiamin(1,2), zur Reaktion bringt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19593000105
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  • 4
    Electronic Resource
    Electronic Resource
    Das erste Inselgallat mit unterschiedlichen Gegen-Kationen: Li3Na2[GaO4] (1982)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 495 (1982), S. 7-15 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The First Nesogallate with Different Counter-cations: Li3Na2[GaO4]We prepared hitherto unknown Li3Na2[GaO4] [Heating mixtures of Na8Ga2O7 and Li2O gives single crystals (Ag-cylinders, 700°C, 14 d), from binary oxides Li2O, Na2O and β-Ga2O3 the compound is obtained as powder (like above, 680°C, 7 d)]. The single crystals are colourless and transparent, the powders are white. A new type of structure is found. The single crystal data are: Pnnm, a = 8.260, b = 7.946, c = 6.515 Å, Z = 4, dx = 3.117, dpyk = 3.073 g · cm-3 [4-circle-diffractometer data, MoKα, 679 from 709 I0(hkl), R = 3.97% and RW = 3.88%, Parameter see text, anisotropic refinement]. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.
    Notes: Neu dargestellt wurde Li3Na2[GaO4] [Tempern inniger Gemenge von Na8Ga2O7 mit Li2O liefert Einkristalle (Ag-Bömbchen, 700°C, 14 d), aus den binären Oxiden Li2O, Na2O und β-Ga2O3 erhält man entsprechende Pulverpräparate (wie oben, 680°C, 7 d)]. Die Einkristalle sind farblos und transparent, die Pulver weiß. Der neue Strukturtyp wird durch Einkristalldaten belegt: Pnnm; a = 8,260, b = 7,946, c = 6,515 Å; Z = 4; drö = 3,117, dpyk = 3,073 g · cm-3 [Vierkreisdiffraktometerdaten PW 1100, MoKα; 679 von 709 I0(hkl); R = 3,97% und RW = 3,88%; Parameter siehe Text; anisotrope Verfeinerung].Der Madelunganteil der Gitterenergie, MAPLE, wird berechnet und diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19824950102
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  • 5
    Electronic Resource
    Electronic Resource
    Das erste Oxid vom Formeltyp K5[MO4]: K5[TIO4] [1] (1984)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 517 (1984), S. 67-74 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The First Oxide with the Formula Type K5[MO4]: K5[TlO4]Light yellow powder and pale yellow transparent single crystals of K5[TlO4] were newly prepared from mixtures of binary oxides (K2O/Tl2O3) preheated and levigated several times [closed Ag-cylinder, 580°C, 24 h and 600°C, 20 d]. Space group Pbca with a = 1170.4(3), b = 686.1(1), c = 2079.2(5) pm, Z = 8 [four-circle-diffraktometer data, 997 I0(hkl), R = 7.87%, Rw = 5.63%, MoKα] (parameter s. text). The crystal structure belongs to the Na5[GaO4] type. Structural aspects, ECoN and MAPLE are discussed.
    Notes: Neu dargestellt wurden hellgelbes Pulver und blaßgelbe durchsichtige Einkristalle von K5[TIO4] aus mehrmals innig verriebenen, vorgetemperten Gemengen der binären Oxide (K2O/Tl2O3) [geschlossenes Ag-Bömbchen, 580°C, 24 h bzw. bei 600°C, 20 d]. Es liegt die Raumgruppe Pbca mit a = 1170,4(3), b = 686,1(1), c = 2079,2(5) pm, Z = 8 vor. [Vierkreisdiffraktometerdaten, 997 I0(hkl), R = 7,87%, Rw = 5,63%, MoKα] (Parameter s. Text). K5[TlO4] ist isotyp zu Na5[GaO4]. Strukturelle Aspekte, ECoN und MAPLE werden diskutiert.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19845171005
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  • 6
    Electronic Resource
    Electronic Resource
    Berichtigung (1985)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 521 (1985), S. 240-240 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19855210228
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  • 7
    Electronic Resource
    Electronic Resource
    Na3Al2Nb34O64 und Na (Si, Nb) Nb10O19: Clusterverbindungen mit isolierten Nb6-OktaedernProfessor Rudolf Hoppe zum 65. Geburtstage am 29. Oktober 1987 gewidmet (1987)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 553 (1987), S. 106-122 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Na3Al2Nb34O64 and Na (Si, Nb) Nb10O19. Cluster Compounds with Isolated Nb6-OctahedraHexagonal ormolu coloured plates of the new compounds Na3Al2Nb34O64 (I) and Na(Si, Nb)Nb10O19 (II) were prepared by heating pellets of NaF, Al2O3, NbO2 and NbO (3:1:8:2) and NaF, NbO2 and NbO (1:4:2), respectively, at approx. 850°C. I was contained in a sealed gold capsule, II in a silica tube. The Si incorporated in II originates from the container material. Both compounds crystallize in R 3, I with a = 784.4(1), c = 7065(1) pm, Z = 3 and II with a = 784.1(1), c = 4221.8(5) pm, Z = 6. I and II represent new structure types. They contain the same characteristic structural units, namely discrete Nb6O12 clusters (dNb-Nb = 283 ± 4 pm) and Nb2O10 units with Nb-Nb dumbells (dNb-Nb ≍ 269 pm) in edgesharing coordination octahedra. In addition NbO6 octahedra containing Nb in the oxidation state + 5 and NaO12 cube-octahedra occur in both compounds besides AlO4 and SiO4 tetrahedra in I and II, respectively. The structures can be described in terms of a common closepacking of O and Na atoms together with Nb6 octahedra.
    Notes: Hexagonale, altgoldfarbene PlättChen der neuen Verbindungen Na3Al2Nb34O64 (I) bzw. Na(Si, Nb) Nb10O19 (II) wurden durch Erhitzen von zu Pillen gepreßten Gemengen aus NaF, Al2O3, NbO2 und NbO (3:1:8:2) bzw. NaF, NbO2 und NbO (1:4:2) bei etwa 850°C dargestellt. I war in einem geschlossenen Au-Rohr, II in einer Quarzampulle eingeschlossen; das in II eingebaute Si stammt aus der Gefäßwand. Beide Verbindungen kristallisieren in R 3, I mit a = 784,4(1), c = 7065(1) pm und Z = 3, II mit a = 784,1(1), c = 4221,8(5) pm und Z = 6.I und II bilden jeweils einen neuen Strukturtyp. Beide enthalten als charakteristische Baugruppen diskrete Nb6O12-Cluster (dNb-Nb = 283 ± 4pm) sowie Nb2O10-Einheiten mit Nb-Nb-Paaren (dNb-Nb ≍ 269 pm) und kantenverknüpften Koordinationsoktaedern. Ferner liegen NbO6-Oktaeder mit Nb in der Oxidationsstufe + 5, und NaO12-Kuboktaeder sowie in I AlO4-bzw. in II SiO4-Tetraeder vor. Die Strukturen lassen sich mit gemeinsam dichten Packungen von O-Atomen, Na-Atomen und Nb6-Oktaedern beschreiben.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19875531013
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  • 8
    Electronic Resource
    Electronic Resource
    Na(V3-xNbx)Nb6O14 - ein neues Oxoniobat mit [Nb6O12]- und [M2O9]-Clustern (1989)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 568 (1989), S. 8-21 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Na(V3-xNbx)Nb6O14  -  A Novel Oxoniobate with [Nb6O12] and [M2O9] ClustersGoldcolored single crystals and black powders of Na(V3-xNbx)Nb6O14 have been prepared by heating a pellet containing a mixture of NaNbO3, NbO2, NbO, VO2 and NaF or Na2B4O7 (as mineralizers) at 900°C in a sealed gold capsule. The analytically determined Nb : V ratio is 5 : 1 and means that x is about 1.5. The compound crystallizes in P63/m with a = 603.4(1), c = 1807.9(5) pm and Z = 3.The crystal structure can be described in terms of common close packing of sheets of O and Na atoms together with Nb6 octahedra. Characteristic building groups of the new structure type are [Nb6O12] clusters, [M2O9] clusters and NbO5 bipyramids. V atoms are distributed only on the positions of the Nb atoms within the trigonal bipyramids or the [M2O9] clusters. The [Nb6O12] clusters show characteristicaly short distances dNb-Nb = 279.4 and 281.3 pm, respectively. In the [M2O9] units, which are built from two MO6 octahedra that share a common face, V or Nb atoms form M-M dumbbells with dM-M = 255.9 pm. The electronic structure is discussed using Extended Hückel calculations.
    Notes: Goldgelb glänzende Einkristalle und schwarze Pulver von Na(V3-xNbx)Nb6O14 wurden durch Tempern eines zu einer Pille gepreßten Gemenges aus NaNbO3, NbO2, NbO, VO2 und NaF oder Na2B4O7 (als Mineralisatoren) bei 900°C in einem geschlossenen Goldrohr dargestellt. Das analytisch ermittelte Verhältnis Nb : V ist ungefähr 5 : 1, so daß x bei etwa 1,5 liegt. Die Verbindung kristallisiert in P63/m mit a = 603,4(1), c = 1807,9(5) pm und Z = 3.Die Kristallstruktur baut sich aus gemeinsam dicht gepackten Schichten von O-Atomen, Na-Atomen und Nb6-Oktaedern auf. Charakteristische Baugruppen des neuen Strukturtyps sind [Nb6O12]- und [M2O9]-Cluster sowie NbO5-Bipyramiden. Die V-Atome verteilen sich nur auf die Positionen der Nb-Atome in den trigonalen Bipyramiden und den [M2O9]-Cluster. Innerhalb der [Nb6O12]-Cluster liegen charakteristisch kurze Abstände dNb-Nb = 279,4 bzw. 281,3 pm vor. In [M2O9]-Einheiten, zwei über Flächen verknüpften MO6-Oktaedern, bilden V- und Nb-Atome M-M-Hanteln mit dM-M = 255,9 pm. Die Bindungsverhältnisse werden unter Zuhilfenahme von Extended-Hückel-Rechnungen diskutiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19895680103
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  • 9
    Electronic Resource
    Electronic Resource
    High resolution electron microscopy studies of Ba4Nb14O23Dedicated to Professor Harald Schäfer on his 80th Birthday (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 133-137 
    Details
    ISSN: 0044-2313
    Keywords: Barium niobium oxide, Ba4Nb14O23 ; cluster ; electron microscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Untersuchungen an Ba4Nb14O23 mittels hochauflösender Elektronenmikroskopie.Die neue Verbindung Ba4Nb14O23, wurde durch Tempern von Gemengen von Ba5Nb4O15, Nb2O5 und Nb bei 1 450°C unter Ar erhalten. Ba4Nb14O23 wurde durch Untersuchungen mittels hochauflösender Elektronenmikroskopie und Röntgenpulveruntersuchungen charakterisiert. Die Verbindung kristallisiert orthorhombisch C-zentriert mit a=20.782(4), b=12.448(3), c=4.147(1) Å und Z=2. Die Kristallstruktur von Ba4Nb14O23 kann als intergrowth zwischen BaNbO3 und NbO beschrieben werden. Charakteristische Baueinheiten sind Dreierketten spitzenverknüpfter Nb6-Oktaeder, die über Stränge perowskitartiger Baugruppen zu einem dreidimensionalen Netzwerk verknüpt sind.
    Notes: The new compound, Ba4Nb14O23, has been prepared by heating mixtures of Ba5Nb4O15, Nb2O5 and Nb at 1 450°C under Ar. Ba4Nb14O23 has been studied by means of high resolution electron microscopy and X-ray powder diffraction techniques. It has a C-centered orthorhombic unit cell with a=20.782(4), b=12.448(3), c=4.148(1) Å and Z=2. The structure of Ba4Nb14O23 can be considered as being an intergrowth between BaNbO3 and NbO. Characteristic building units are triple chains of corner sharing Nb6 octahedra which are connected via columns of the perovskite type structure to a three dimensional network.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190122
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  • 10
    Electronic Resource
    Electronic Resource
    Das erste Oligo-Oxo-Aluminat: Na14[Al4O13] (1984)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 512 (1984), S. 240-240 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19845120525
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