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  • Inorganic Chemistry  (19)
  • Polymer coating  (3)
  • Industrial Chemistry  (2)
  • hydrogen bonds  (2)
  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    New polymer coated anion-exchange HPLC-phases: Immobilization of poly (2-hydroxy, 3N-ethylenediamino) butadiene on silica and alumina (1987)
    Springer
    Chromatographia 23 (1987), S. 435-441 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion-exchange stationary phases ; Polymer coating ; Cross-linking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary PHEB=POLY(2-hydroxy, 3N-ethylenediamino)butadiene has been synthesized. This unsaturated pre-polymer can be immobilized on different, preferably inorganic supports of suitable porosity such as silica or alumina by cross-linking. Weak anion-exchange phase are obtained. Such phases do not have the disadvantages of organic polymeric phases, regarding pressure stability and swelling by solvent influence. The ion-exchange capacity and the retentivity of IE-separations can deliberately be varied via the thickness of the cross-linked polymer layer. Alumina can also be coated with PHEB applying the same cross-linking procedure. Such phases exhibit an exceptional chemical stability even when operated with mobile phases at very high pH-values. Separations of excellent selectivity are achieved for inorganic anions, as well as with mixtures of aliphatic and aromatic free acids also including hydroxy- (mono- or poly)carboxylic acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02311821
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  • 4
    Electronic Resource
    Electronic Resource
    HPLC-separation of enantiomers using quinine, covalently bonded to silica as stationary phase (1988)
    Springer
    Chromatographia 25 (1988), S. 265-271 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral phases ; Polymer coating ; Quinine substituted polysiloxanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Stationary phases for chiral separations have been synthesized by chemical modification of porous small particle silica using new procedures of fixation of the chiral moiety. So called pre-polymers of the methylpolysiloxane polysiloxane type are immobilized on silica surfaces by different procedures. These pre-polymers are substituted by chiral groups. Their synthesis is done externally i.e. not in-situ on the support surface. The immobilization on the silica surface is achieved by crosslinking and/or by chemical bonding. Anchor groups within the pre-polymer (e.g. SiH) as well as on the silica surface (SiOH) give rise to the chemical bonding therewith. Chiral phases with quinine as the chiral moiety were obtained which show high separation efficiency as well as chemical stability, in addition to the enantiomeric selectivity required for the separation of certain types of aliphatic and aromatic alcohols.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02324699
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  • 5
    Electronic Resource
    Electronic Resource
    Polymer-coated cation-exchange stationary phases on the basis of silica (1987)
    Springer
    Chromatographia 23 (1987), S. 465-472 
    Details
    ISSN: 1612-1112
    Keywords: Cation-exchange LC ; Polymer coating ; Silica-based stationary phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The procedure of polymer coating of preferably inorganic porous particle support materials for LC has been applied to the preparation of a new type of weak cationexchange phases. A special copolymer of butadiene and maleic acid could be immobilized on silica by cross-linking effected with radical starters such as peroxides or γ-radiation. The chromatographic properties of such materials proved to be excellent regarding efficiency, ion-exchange capacity and selectivity, as well as chemical stability also in comparison to other, commercially available, materials. Test measurements were successfully performed with ionic or ionizable inorganic and organic solutes over the entire applicable pH-range of the mobile phase which also contained organic modifiers. A special feature of the new type of cation-exchange phase is the minor contribution of hydrophobic (lipophilic) interaction to the retention mechanism besides the actual ion-exchange process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02309412
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  • 6
    Electronic Resource
    Electronic Resource
    Retrofit-Design und Kostenoptimierung einer großtechnisch realisierten Extraktivrektifikation (1997)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 69 (1997), S. 1229-1230 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330690920
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  • 7
    Electronic Resource
    Electronic Resource
    39. Mehrgrößenregelkonzepte für Rektifikationskolonnen auf Basis von Betriebsdaten und stationären Modellen (1996)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 68 (1996), S. 1088-1088 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330680941
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  • 8
    Electronic Resource
    Electronic Resource
    Darstellung, Strukturen und Eigenschaften von SmBeF4 und SrBeF4  -  ungewöhnliche Varianten der BarytstrukturIn memoriam Professor Wilhelm Klemm (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 179-186 
    Details
    ISSN: 0044-2313
    Keywords: Strontium beryllium tetrafluoride ; samarium beryllium tetrafluoride ; structure ; divalent Samarium ; luminescence ; magnetism ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation, Structures, and Properties of SmBeF4 and SrBeF4 - Unusual Variants of the Baryt Type StructureSmBeF4 has been obtained as orange-yellow crystals and SrBeF4 as colourless crystals while heating mixtures of SmF3, Sm-powder, BeF2 (2 : 1 : 3) and SrF2 and BeF2 (1 : 1), respectively, under Ar after 7-10 d at about 700°C. SmBeF4 crystallizes in Pna21 (No. 33) with a = 846.1(5), b = 676.9(5), c = 524.1(4) pm and SrBeF4 in P21/n (Nr. 14) with a = 529.5(5), b = 830.9(2), c = 678.8(4) pm and β = 90.0°.The structures of SmBeF4 and the room temperature modification of SrBeF4 are related to the baryt type structure. The differences to the structure BaSO4 are mutual rotations of the BeF4 tetrahedra and their shift with respect to the Sm and Sr framework, respectively. According to the refinement of the structure of SmBeF4 at -174°C these effects are enhanced at low temperatures. SmBeF4 exhibits sharp luminescence lines at around 690nm. Measurements of the magnetic susceptibility show the temperature dependence typically found for Sm2+. The Madelung parts of the lattice energy for SmBeF4 und SrBeF4 have been calculated and discussed.
    Notes: Orangegelbe Kristalle von SmBeF4 und farblose Kristalle von SrBeF4 wurden durch Erhitzen entsprechender Gemenge von SmF3, Sm-Pulver, BeF2 (2 : 1 : 3) bzw. SrF2 und BeF2 (1 : 1) unter Ar nach 7-10 d bei ca. 700°C erhalten. SmBeF4 kristallisiert in Pna21 (Nr. 33) mit a = 846,1(5), b = 676,9(5), c = 524,1(4) pm und SrBeF4 in P21/n (Nr. 14) mit a = 529,5(5), b = 830,9(2), c = 678,8(4) pm und β = 90,0°.Die Strukturen von SmBeF4 und der Raumtemperaturmodifikation von SrBeF4 sind mit dem Baryttyp verwandt. Die Unterschiede zur Barytstruktur bestehen in gegenseitigen Verdrehungen der BeF4-Tetraeder und deren Verschiebung gegenüber dem Sm- bzw. Sr-Teilgerüst. Die Bestimmung der Tieftemperaturstruktur von SmBeF4 (-174°C) zeigt eine Verstärkung die ser Effekte. SmBeF4 zeigt die für Sm2+ charakteristischen intensiven Lumineszenzbanden bei etwa 690 nm sowie eine für Sm2+ typische Temperaturabhängigkeit der magnetischen Suszeptibilität. Die Madelunganteile der Gitterenergie für SmBeF4 und SrBeF4 wurden berechnet und diskutiert.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220126
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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    LiSmAlF6  -  das erste Fluoroaluminat mit zweiwertigem Samarium (1991)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 606 (1991), S. 169-176 
    Details
    ISSN: 0044-2313
    Keywords: Lithium samarium hexafluoroaluminate ; preparation ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: LiSmAlF6  -  the First Fluoroaluminate with Divalent SamariumLiSmAlF6, the first quaternary fluoride with Sm2+ that has been obtained as red transparent single crystals, is formed while heating corresponding mixtures of the starting materials in niobium or tantalum crucibles under argon after 7-10 d at about 800°C. Orange-red, microcrystalline powder samples of LiSmAlF6 could be prepared at T ≤ 700°C after 1-2 d under the same conditions.LiSmAlF6, crystallizes as a new structure type in P6322 (Nr. 182) with a = 507.9(1), c = 1 040.5(1) pm and Z = 2 (CAD4, 2 512 Io, Rw = 2,3%). The crystal structure of LiSmAlF6 is related to the LiCaAlF6 structure type whereby the essential difference lies in the coordination of the M2+ ions. Ca2+, as well as Sr2+ in LiSrAlF6, exhibit octahedral coordination, whereas Sm2+ has, surprisingly, trigonal prismatic coordination to F-. The two triangles of the SmF6 prism are twisted by 8.3° with respect to each other.Measurements of the magnetic susceptibility show the temperature dependence typically found for Sm2+. The Madelung part of the lattice energy has been calculated and is discussed.
    Notes: LiSmAlF6, das erste in Form roter, transparenter Einkristalle erhaltene quaternäre Fluorid mit Sm2+, bildet sich beim Erhitzen geeigneter Ausgangsmenge in Niob- oder Tantaltiegln unter Ar nach 7-10 d bei ca. 800°C. Orangerote, mikrokristalline Pulverproben von LiSmAlF6 können bei T ≤ 700°C bereits nach 1-2 Tagen unter sonst gleichen Bedingungen dargestellt werden.LiSmAlF6 kristallisiert in einem neuen Strukturtyp in P6322 (Nr. 182) mit a = 507,9(1), c = 1 040,5(1) pm und Z = 2(CAD4, 2 512 Io, Rw = 2,3%). Die Kristallstruktur von LiSmAlF6 ist dem LiCaAlF6-Typ verwandt, zeigt aber den wesentlichen Unterschied in der Umgebung für M2+ : Ca2+, wie auch Sr2+ in LiSrAlF6, werden oktaedrisch, Sm2+ jedoch überraschenderweise trigonal-prismatisch von F- koordiniert. Die beiden Dreiecke des SmF6-Prismas sind um 8,3° gegeneinander verdreht.Messungen der magnetischen Suszeptibilität zeigen die für Sm2+ typische Temperaturabhängigkeit. Der Madelunganteil der Gitterenergie wurde berechnet und diskutiert.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19916060117
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