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  • 1
    ISSN: 0948-5023
    Keywords: Molecular mechanics ; Structure of intercalates ; Vanadyl phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular mechanics simulations using Cerius2 combined with X-ray diffraction and supported with vibrational spectroscopy have been used to investigate the layered structure of vanadyl phosphate VOPO4 intercalated with ethanol. This intercalated structure exhibits certain degree of disorder, which affects the diffraction diagram and obstructs the conventional structure analysis based on diffraction methods only. Present structure analysis is focused to the crystal packing in the interlayer space and layer stacking in the intercalate. The bilayer arrangement of ethanol molecules in the interlayer has been found, giving the basal spacing d = 13.21 Å, experimental d-value obtained from X-ray diffraction is 13.17 Å. One half from the total number of CH3CH2OH molecules is anchored with their oxygens to VOPO4 layers to complete vanadium octahedra and their orientation is not very strictly defined. The second half of ethanoles is linked with hydrogen bridges to the anchored etahanoles and sometimes also to the layer oxygens. Positions and orientations of these unachored ethanoles with respect to VOPO4 layers exhibit certain degree of disorder, resulting in the disorder in layer stacking. Molecular mechanics simulations revealed the character of this displacement disorder in layer stacking and enabled to determine the components of the displacement vector.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular modeling 6 (2000), S. 9-15 
    ISSN: 0948-5023
    Keywords: Keywords Vanadyl phosphate-alkanol intercalates, Molecular mechanics, Structure analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular mechanics simulations supported by X-ray powder diffraction measurements have been used to investigate the structure of vanadyl phosphate intercalated with 1-alkanols CnH2n+1OH for n = 2, 3, 4. Modeling revealed the specific features and differences in arrangement of alkanol molecules with different chain length, depending on the relation between the parameters of active sites network and size of guest molecules. This result enabled us to explain the irregularities in dependence of basal spacing on the chain length. The comparison of experimental dexp and calculated dcalc values of basal spacing showed the good agreement of modeling with x-ray powder diffraction. While we obtained dcalc(Univ) = 13.05 Å for vanadyl phosphate-ethanol using the Universal force field (dexp=13.17 Å), for vanadyl phosphate-propanol and vanadyl phosphate-butanol better agreement with experiment was obtained using the Tripos force field. In the case of vanadyl phosphate-propanol the calculated basal spacing dcalc(Tripos) = 14.49 Å, compared with an experimental value of dexp=14.36 Å. For vanadyl phosphate-butanol dcalc(Tripos) = 17.71 Å and dexp=17.90 Å.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 20 (1994), S. 381-391 
    ISSN: 1573-1111
    Keywords: Intercalation ; X-ray powder diffraction ; vanadyl phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The course of intercalation of water into α1-VOPO4 has been studied by thermomechanical analysis and X-ray diffraction. Neither formation of vanadyl phosphate monohydrate nor staging were observed during the intercalation. The broadening and the shift of the positions of the lines in the diffractograms have been explained by the random stacking of intercalated and nonintercalated layers in the sample.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 26 (1996), S. 311-319 
    ISSN: 1573-1111
    Keywords: Intercalation ; X-ray powder diffraction ; thermomechanical analysis ; volumetry ; vanadyl ; phosphate ; ethanol ; kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The course of intercalation of ethanol into VOPO4 has been studied by X-ray diffraction, thermomechanical analysis and a volumetric method. In all cases the kinetic curves were observed to have a sigmoidal shape. A model, based on the Avrami equation, has been proposed for description of the kinetic behavior. The activation energy of intercalation based on this model has been determined. The existence of the advancing phase boundary in the system during intercalation has been confirmed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 33 (1999), S. 391-402 
    ISSN: 1573-1111
    Keywords: intercalation ; 1-alkanols ; vanadyl phosphate ; mixed layer-type complexes ; x-ray powder diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mixed intercalates VOPO4.C2H5 OH.C4 H9OH, VOPO4.C3H7 OH.C5H11OH, VOPO4.C3H7 OH.C6H13OH and VOPO4.C4H9 OH.C6H13OH have been prepared by reaction of polycrystalline vanadyl phosphate dihydrate with liquid mixtures of the 1-alkanols in a microwave field. The same mixed layer-type complexes were also obtained as intermediary products of exchange reactions consisting in substitution of one alkanol bound in the solid intercalate by another alkanol introduced in the form of vapour. The composition of products has been determined, and the basal spacing of all the mixed layer-type complexes prepared has been found by diffraction. A structural principle is suggested which governs the depositing of two kinds of 1-alkanol molecules (differing in the lengths of their aliphatic chains) while acting as guests in the layered structure of vanadyl phosphate.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 14 (1992), S. 19-24 
    ISSN: 1573-1111
    Keywords: Intercalation ; layered lattice ; interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The paper deals with the relations between host lattices and guest molecules. Several types of interaction of the guest molecules and the host material are explained and some conclusions are made about the arrangement of various guest molecules in the van der Waals' gap.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 31 (1998), S. 275-286 
    ISSN: 1573-1111
    Keywords: intercalation ; mechanism ; kinetics ; vanadyl phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Recent knowledge of the kinetics and intercalation mechanisms are summarized and accompanied by examples of intercalation reactions of water and ethanol into anhydrous vanadyl phosphate and redox intercalation of alkali metal cations into vanadyl phosphate dihydrate. Three possible mechanisms of intercalation are presented which are based on: (i) a concept of exfoliation of layers; (ii) the formation of stages and randomly stacked layers; (iii) co-existence of intercalated and non-intercalated parts of crystals of the host separated by an advancing phase boundary. The corresponding kinetic curves are ascribed to mechanisms (ii) and (iii).
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-1111
    Keywords: Intercalation ; rate of intercalation ; observing intercalation processes ; change of volumes of intercalating systems ; vanadyl phosphate ; vanadyl sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new experimental method is suggested for the kinetic measurements of intercalation reactions in systems formed by a polycrystalline layered host and a liquid molecular guest. The method is based on the fact that the molecular guest decreases its molar volume on entering the space between the host layers. Hence the volume of the system in which an intercalation process takes place is measurably decreased. The time course of the intercalation process can thus be monitored by measuring the volume change of the system. The method has been used to obtain kinetic data about heterogeneous intercalations of some liquid aliphatic compounds into layered structures of anhydrous vanadyl phosphate and sulfate.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 36 (2000), S. 301-309 
    ISSN: 1573-1111
    Keywords: vanadyl phosphate ; niobyl phosphate ; intercalation ; alkanediols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Intercalation compounds of VOPO4and NbOPO4 with 1,2-alkanediols (from C3 to C16)have been prepared. The diol molecules are placedbetween host layers in a bimolecular way with theiraliphatic chains tilted at an angle of 70°. Itwas found that the intercalates contain 1.5 moleculesof diol per formula unit. Three ways of bonding of thediol molecules to the host layers are proposed. Twomolecules of diol are coordinated to the metal atomsby their first and second oxygen, respectively. Thethird diol molecule is anchored in the interlayerspace by H-bonds.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1434-1948
    Keywords: Vanadyl arsenate ; Hydrates ; Layered compounds ; Vibrational spectroscopy ; X-ray scattering ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The course of the intercalation and deintercalation of water molecules in vanadyl arsenate has been studied by X-ray diffraction analysis and by infrared and Raman spectroscopies. The formation of VOAsO4 hydrates at ambient temperature has been found to depend on relative humidity (r.h.): VOAsO4 · 5 H2O (basal spacing c = 10.48 Å) is formed at r.h. above 76%, VOAsO4 · 3 H2O (c = 8.03 Å) at 43-76% r.h., VOAsO4 · 2 H2O (c = 7.33 Å) at 11-43% r.h.; dehydrated VOAsO4 (c = 4.18 Å) exists near 0% r.h. Like the thermal dehydration of VOPO4 · 2 H2O, the thermal dehydration of VOAsO4 · 3 H2O proceeds in a stepwise manner so that the dihydrate and monohydrate are formed en route to the anhydrous compound. The arsenate monohydrate is gradually dehydrated over a broad temperature range. The broad diffraction lines observed can be explained in terms of the existence of a disordered phase containing monohydrated and anhydrous forms of vanadyl arsenate. A similar phenomenon has been observed during the dehydration of VOAsO4 · 3 H2O over phosphorus pentoxide at ambient temperature. The hydration of VOAsO4 is different from that of VOPO4. The first step, i.e. the insertion of water that coordinates to the vanadium atoms, is very slow. On the contrary, the uptake of further water molecules with the formation of higher hydrates is fast. It thus seems likely that the filling of one interlayer space with water facilitates the intercalation of further water into neighboring interlayer spaces. Therefore, only higher hydrates together with the original anhydrous phase are observed. Impedance spectral measurements indicate that the conductivity of the trihydrate has a mixed ionic/electronic character.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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