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  • Chemistry  (3)
  • Analytical Chemistry and Spectroscopy
  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Structures of Rare Earth Homodinuclear Macrocyclic Complexes with the Polyamine Polycarboxylic Ligand 1,4,7,10,14,17,20,23-Octaazacyclohexacosane-1,4,7,10,14,17,20,23-octaacetic Acid (H8OHEC) in the Crystal and in Solution (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1735-1743 
    Details
    ISSN: 1434-1948
    Keywords: Crystal structure ; Solution structure ; Homodinuclear lanthanide complexes ; Lanthanides ; Macrocyclic ligands ; Polyamine polycarboxylic acid ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-state structures of the four homodinuclear chelate complexes, [Na2(Y2OHEC)(H2O)2] · 7 H2O · C2H5OH (1), [Na2(Gd2OHEC)(H2O)2] · 12 H2O (2), [Na2(Eu2OHEC)(H2O)2] · 11 H2O (3), and [Cs2(La2OHEC)(H2O)2] · 14 H2O (4) (H8OHEC = 1,4,7,10,14,17,20,23-octaazacyclohexacosane-1,4,7,10,14,17,20,23-octaacetic acid), were determined by X-ray crystal structure analysis. Each lanthanide(III) ion is ninefold coordinated by eight donor atoms of the ligand system and the oxygen atom of one water molecule. The structures are compared with those of DOTA- and TETA-coordinated complexes and the conformation of the OHEC ligand system with that of the parent amine and its dinuclear copper complex. NMR investigations of the diamagnetic complex 1indicate a very similar environment of the lanthanide cations in solution and in the solid state. Low-temperature and variable-temperature 1H-NMR measurements prove the existence of two isomers of 1 (3.5:1 ratio) which undergo conformational processes. The rate constants of these processes were deduced from a complete line shape analysis and were used to determine the activation parameters.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/99081_s.pdf or from the author.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of Schiff Base Chelates of Tetramic Acids as NMR Contrast Agents for micro imaging (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 642-646 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Novel Cu(II) complexes derived from N,N′ P-ethylene-bis-(1′,5′,5′-trimethyltetramic acid-3′-acetiminato)copper(II) aCu [1] were evaluated as contrast agents for NMR microscopy and therefore tested for penetration into living cells (Xenopus laevis oocytes). By in vitro 1H NMR relaxation (T1) and atomic absorption spectroscopy measurements (AAS) we confirmed, that independent of the complex isomers (Z/Z, Z/E, E/E, E/Z) compounds with alkyl substituents in R1 - R5 exclusively were able to penetrate the plasma membranes. It is noteworthy that compounds containing the tetramic acid moieties from both a penetrating and a non-penetrating complex most likely were accumulated in the plasma membrane and/or plasma membrane-associated vesicles, which was concluded from in vitro NMR measurements combined with AAS trace analyses. In this context the crystal and molecular structure of the ‘chimerical’ C17H22N4O4Cu · 3H2O kCu · 3H2O were determined by x-ray analysis. The x-ray structural parameters are discussed in detail.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199633801122
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  • 3
    Electronic Resource
    Electronic Resource
    1,4,7,10,13,16,19,22-Octaazacyclotetracosane-1,4,7,10,13,16,19,22-octaacetic Acid (H8OTEC) and 1,4,7,10,14,17,20,23-Octaazacyclohexacosane- 1,4,7,10,14,17,20,23-octaacetic Acid (H8OHEC): Synthesis and Characterization of Two Large Macrocyclic Polyamine Polycarboxylic Ligands and Some of Their Copper(II) and Lanthanide(III) Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 267-277 
    Details
    ISSN: 0009-2940
    Keywords: Macrocyclic ligands ; Lanthanides ; Copper ; Polyamines ; Polycarboxylic acids ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optimized synthesis of two new macrocyclic polyamine polycarboxylic ligands, 1,4,7,10,14,17,20,23-octaazacyclohexacosane-1,4,7,10,14,17,20,23-octaacetic acid (H8OHEC) (10) and 1,4,7, 10,13,16,19,22-octaazacyclotetracosane-1,4,7,10, 13,16,19,22-octaacetic acid (H8OTEC) (12), is presented. The key step in the synthesis of both is the high yield carboxymethylation of the corresponding macrocyclic amines using tert-butyl bromoacetate followed by acidic hydrolysis of the acetate protecting groups. The molecular structures of the intermediates 1,4,7,10,14,17,20,23-octaazacyclohexacosane (OHEC-amine) (8), and octa-tert-butyl 1,4,7,10,13,16,19,22- octaazacyclotetracosane-1,4,7,10,13,16,19,22-octaacetate (OTEC-ester) (11) are determined by X-ray crystal structure analysis. OHEC-amine 8 reacts with 2 equiv. of CuSO4 yielding the dinuclear complex [Cu2(OHEC-amine)](SO4)2 (13). Complex 13 crystallizes with 16 molecules of water. 13 · 16 H2O contains two copper atoms, which are coordinated in a strongly distorted octahedral fashion by four nitrogen atoms, one oxygen atom from the sulfate dianion and one oxygen atom from a water molecule. The new ligands 10 and 12 are fully characterized by 1D- and 2D-NMR spectroscopy. Both ligands form dinuclear lanthanide(III) chelates (Ln=Y, Sm, Eu, Gd, Yb, Lu), which are stable and highly water soluble. With lanthanum(III) only mononuclear complexes are formed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300221
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