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  • International Union of Crystallography  (1)
  • Wiley-Blackwell  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1911-1918 
    ISSN: 1434-1948
    Schlagwort(e): Macrocycles ; Photochemistry ; Fluorescence spectroscopy ; Coordination chemistry ; Zinc ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The macrocyclic ligands L2 and L3, containing a triethylenetetraamine and a tetraethylenepentaamine moiety linked to the methyl groups of 2,9-dimethyl-1,10-phenanthroline, bind H+ and Zn2+ ions giving rise to modulation of the fluorescence emission intensity. The equilibrium constants and the enthalpy changes for ligand protonation were determined by means of pH-metric and microcalorimetric methods in 0.1 M Me4NCl solutions at 298.1±0.1 K. Also the stability constants of the Zn2+ complexes were determined under the same experimental conditions. L2 forms only mononuclear complexes, while L3 also forms dizinc(II) species. The phenanthroline group has fluorescence emission properties, but interaction with the lone pairs of benzylic nitrogen atoms produces an efficient quenching of the emission. Such a quenching effect can be avoided by deactivation of the benzylic nitrogen atoms by means of protonation or Zn2+ complexation. Hence, L2 and L3 behave as chemosensor for H+ and Zn2+, the photochemical properties of the ligands being modulated by the formation of different protonated and complexed species. In the case of L3, the fluorescence emission is also controlled by the metal to ligand molar ratio, because of the formation of an emissive binuclear complex.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2019-01-15
    Beschreibung: Metoprolol {systematic name: (RS)-1-isopropylamino-3-[4-(2-methoxyethyl)phenoxy]propan-2-ol}, C15H25NO3, is a cardioselective β1-adrenergic blocking agent that shares part of its molecular skeleton with a large number of other β-blockers. Results from its solid-state characterization by single-crystal and variable-temperature powder X-ray diffraction and differential scanning calorimetry are presented. Its molecular and crystal arrangements have been further investigated by molecular modelling, by a Cambridge Structural Database (CSD) survey and by Hirshfeld surface analysis. In the crystal, the side arm bearing the isopropyl group, which is common to other β-blockers, adopts an all-trans conformation, which is the most stable arrangement from modelling data. The crystal packing of metoprolol is dominated by an O—H...N/N...H—O pair of hydrogen bonds (as also confirmed by a Hirshfeld surface analysis), which gives rise to chains containing alternating R and S metoprolol molecules extending along the b axis, supplemented by a weaker O...H—N/N—H...O pair of interactions. In addition, within the same stack of molecules, a C—H...O contact, partially oriented along the b and c axes, links homochiral molecules. Amongst the solid-state structures of molecules structurally related to metoprolol deposited in the CSD, the β-blocker drug betaxolol shows the closest analogy in terms of three-dimensional arrangement and interactions. Notwithstanding their close similarity, the crystal lattices of the two drugs respond differently on increasing temperature: metoprolol expands anisotropically, while for betaxolol, an isotropic thermal expansion is observed.
    Digitale ISSN: 2053-2296
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Standort Signatur Erwartet Verfügbarkeit
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