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  • clathrate  (2)
  • 42.65.Ky  (1)
  • Chemistry  (1)
  • Werner complex  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Microfacetting of Au(110) electrodes: An optical second-harmonic generation study (1995)
    Springer
    Applied physics 60 (1995), S. 121-125 
    Details
    ISSN: 1432-0630
    Keywords: 42.65.Ky
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The formation and lifting of microfacetting at an Au(110) electrode surface was studied by using in-situ optical Second-Harmonic Generation (SHG). In contrast to the unreconstructed (1×1) Au(110) surface which has aC 2v symmetry, the reconstructed surface exhibits aC s symmetry due to essentially (111)-oriented microfacets. Hence, it shows SHG-anisotropy patterns fundamentally different to those of a non-reconstructed surface. Apparently, the nonlinear susceptibility tensor contains an additional threefold symmetry element. Its amplitude was determined using Fourier analysis of SHG-anisotropy curves and, thus, served as a measure of microfacetting of the Au(110) surface. We observed that adsorption of an organic molecule, such as pyridine, has little effect on the electrode-surface crystallography. In contrast, adsorption of bromide ions results in the lifting of microfacetting as indicated by the disappearence of the threefold symmetry term. Potential-step experiments gave time constants for the lifting of microfacetting in the range of 〈 τ1/2〈150 ms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538235
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  • 2
    Electronic Resource
    Electronic Resource
    Phase and structural study of clathrate formation in the [Zn(MePy)2(NCS)2]-MePy system (MePy=4-methylpyridine) (1994)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 17 (1994), S. 305-316 
    Details
    ISSN: 1573-1111
    Keywords: Phase diagram ; clathrate ; X-ray structure ; 4-methylpyridine ; Zn(II) isothiocyanate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A phase diagram of the [Zn(MePy)2(NCS)2]-MePy binary system has been studied by DTA and solubility methods. Two compounds melting incongruently (at 63 and 57°C) have been discovered in the system. They have been obtained as separate phases with crystals of different shape (needles and octahedra). Their composition has been determined by analytical methods and verified by X-ray structural analysis: [Zn(MePy)4(NCS)2]·0.67 MePy·xH2O, wherex depends on the synthesis conditions, and [Zn(MePy)4(NCS)2]·MePy, respectively. The preliminary X-ray study of the first compound (at −100°C) has shown it to be isostructural with the known clathrates of the common formula [M(MePy)4(NCS)2]·0.67MePy·xH2O, where M=Cu, Mn, Mg andx=0–0.33. The unit cell parameters are as follows:a=27.20(1),c=11.202(4) Å, space group $$R\bar 3$$ ,Z=9. The X-ray study of [Zn(MePy)4(NCS)2]·MePy (at−50°C) has shown it to be analogous to the ‘organic zeolite’ β-phase with the guest MePy molecules located in the channels formed by molecular packing of the [Zn(MePy)4(NCS)2]host. The cell is tetragonal, the space groupI41/a,a=16.845(6),c=23.496(7) Å,V=6667(4) Å3,Z=8,D calc=1.289 g cm−3,R=0.074. The zinc cation is surrounded by a slightly irregular octahedron of six nitrogen atoms of the MePy and NCS ligands. The crystallisation field of the host [Zn(MePy)4(NCS)2] complex in the temperature range concerned is absent in the phase diagram. It suggests contact stabilization of the [Zn(MePy)4(NCS)2] molecule by the guest in the clathrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707126
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  • 3
    Electronic Resource
    Electronic Resource
    Two clathrates of bis(isothiocyanato)tetrakis(4-methylpyridine)magnesium(II) as a host with 4-methylpyridine as a guest (1994)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 18 (1994), S. 317-329 
    Details
    ISSN: 1573-1111
    Keywords: Crystal structure ; clathrate ; Werner complex ; isothiocyanate ; 4-methylpyridine ; Mg(II)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two clathrate modifications of the title host with 4-methylpyridine (4-CH3C5H4N) as a guest have been determined at −50°C. [Mg(4-CH3C5H4N)4(NCS)2] · 2/3(4-CH3C5H4N) · 1/3H2O is trigonal, space group $$R\bar 3$$ , witha=27.630(7),c=11.219(3) ÅV=7417(4) Å3,Z=9,D calc=1.171 g cm−3,μ(CuK α)=18.506 cm−1, finalR=0.064. [Mg(4-CH3C5H4N)4(NCS)2] · (4-CH3C5H4N) is tetragonal, space group I4l/a, witha=16.944(7),c=23.552(9)Å,V=6762(5) Å,Z=8,D calc=1.191 g cm−3, μ(CuK α)=18.200 cm−1, finalR=0.071. The structures consist of molecular packings of the same host complex units and the guest species. The Mg(II) cation is octahedrally coordinated to theN-atoms of four 4-methylpyridine and twotrans-coordinated isothiocyanato ligands in the host molecule. The conformations of the molecule are considerably different both in symmetry and in geometry in these two structures. The guest 4-methylpyridine molecules are disordered into channels which have different topology in these two clathrates resulting in different thermal stability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707381
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  • 4
    Electronic Resource
    Electronic Resource
    Host-guest interactions of calix[4]resorcinarenes with benzene derivatives in conditions of reversed-phase high-performance liquid chromatography. Determination of stability constants (1998)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 426-437 
    Details
    ISSN: 0894-3230
    Keywords: calix[4]resorcinarenes ; organophosphorus compounds ; solvatophobic interactions ; host-guest complexation ; high-performance liquid chromatography ; x-ray analysis ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reversed-phase high-performance liquid chromatography [LiChrosorb RP-18,UV detection at 254 nm and acetonitrile-water (86:14,v/v) as mobile phase] was applied to studies of the host-guest complexation of tetraalkylcalix[4]resorcinareneoctols and their upper rim phosphoryl, sulfonyl and dialkylaminomethyl derivatives with some aromatic guests in the mobile phase. It was shown that the formation of the inclusion complexes results in changes in the retention of aromatic guests and improves their separation. Stability constants of the complexes were calculated from the dependences of the l/k′ values of the aromatic guest on the concentration of the calix[4]resorcinarene in the mobile phase. The molecular structure of 4,6,16,18-tetrahydroxy-10,12,22,24-tetrakis(dipropoxyphosphoryloxy)-2,8,14,20-tetramethylcalix[4]resorcinarene (12) was determined. Crystal data for 12 are P21/n, a  =  16.708(9) Å, b  =  18.683(6) Å, c  =  20.243(5) Å, β  =  95.75(3)°, V  =  6287(4) Å3 and Z  =  4. Compound 12 exists in a boat conformation, in which two opposite unsubstituted resorcinol rings of the macrocyclic skeleton lie in the plane formed by four methine bridges and two diphosphorylated rings are perpendicular to the plane. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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