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  • Electronic Resource  (17)
  • 1975-1979  (8)
  • 1970-1974  (8)
  • 1965-1969  (1)
  • 1945-1949
  • Organic Chemistry  (17)
  • 1
    Electronic Resource
    Electronic Resource
    Metal complexes with macrocyclic ligands. XIIIPart XII, see [1].. The complexation of Cu2+ with triazacycloalkanesHerrn Prof. Dr. E. Giovannini zum 70. Geburtstag gewidmet (1979)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 1089-1096 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potentiometric study of the complexation of Cu2+ with 1,4,7-triazacyclononane (1), 1,4,8-triazacyclodecane (2) 1,5,9-triazacyclododecane (3) has shown that CuL, CuL2 and (CuLOH)2 are the main species present in solution. Their stabilities (Table 1) and their absorption spectra (Table 2) indicate facial coordination of the cyclic triamines in a distorted octahedral geometry.The formation and dissociation kinetics have been measured by stopped-flow techniques. The formation in acetate buffer can be described by the reaction of Cu2+ and CuAcO+ with the monoprotonated species of the ligand. The bimolecular rate constants for these complexations (Table 3) decrease when the ring size increases. In contrast the dissociation induced by acid is only little affected by the ring size. Thus for these complexes the rate of formation and not that of the dissociation determines the overall stability.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19790620417
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  • 2
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands. IXFor part VIII see [1].. Synthesis and properties of a new class of branched N4-macrocycles with an additional ligating group in the side chain (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 1376-1387 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of Ni2+ the template reaction between 2,6-diacetylpyridine and 4-(2-dimethylaminoethyl)- or 4-(2-hydroxyethyl)-1, 7-diamino-4-azaheptane yields the complexes of either the open-chain ligand (3 and 11) or of the macrocycle (4 and 12). Reduction of the imino group in 4 and 12 with PtO2/H2 gives 5 and 13, respectively. In the case of the dimethylamino derivative 5 a mixture of at least four isomers was obtained. These were partially separated by chromatography on Sephadex SP-25 cation exchanger. Through demetalation of the Ni2+ complexes by cyanide the new macrocycles 7 and 14 were isolated, from which the corresponding Zn2+ and Cu2+ complexes were prepared.The macrocyclic Ni2+-complexes 4, 12, 5 and 13 can exist in two forms depending on the pH of the solution. At low pH protonation of the dimethylamino or hydroxy group in the side chain occurs. The metal ion is then bound to the four nitrogen atoms of the macrocycle in a square planar ligand field. At higher pH, however, the dimethylamino or hydroxy group (the last one also in its deprotonated form) can coordinate to one of the axial positions, whereby pseudooctahedral coordination geometry is induced. This reaction can be quantitatively described by a reversible acid-base equilibrium, the pKH of which greatly depends on the nature of the functional group, the degree of unsaturation of the macrocycle and the metal ion.The acid-base reaction and the concomitant structural change are a direct consequence of the unique combination of the rigid and kinetically stable structure of the macrocycle and of the flexible and kinetically labile functional group of the side chain.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610421
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  • 3
    Electronic Resource
    Electronic Resource
    Metal Complexes of Macrocyclic Ligands. XIIPart XI, see [1].. A Complexone-like Tetraazamacrocycle (1979)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 683-688 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexone-like tetraazamacrocycle 1 (LH4) forms a series of metal complexes with Co2+, Ni2+, Cu2+ and Zn2+ (M2+) of the type MLH2, ML2- and M2L, which have been isolated and characterized by VIS., IR. and NMR. spectroscopy. Based on these results tentative structures for the different species are proposed.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19790620306
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  • 4
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands. XIV. Formation, dissociation and metal exchange with an N2S2-macrocyclePart XIII, see [1]. (1979)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 62 (1979), S. 2562-2568 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 10, 10, 12-Trimethyl-3,4-benzo-1,6-dithia-9,13-diazacyclopentadecen-dihydrochloride (LH22+, 2) and its Ni2+ complex were synthesized and their reactivity studied. The formation kinetics of 2 with Cu2+ were found to be a second order reaction between Cu2+ or CuACO+ and the monoprotonated form of the ligand LH+. The rate constant kCuLH = 29 M-1S-1 is 105-106 times smaller than those of monoprotonated tetraazamacrocycles either because of second bond formation or because of a strong electrostatic interaction between the positive charges of the Cu2+ and the ammonium group. The metal-metal exchange between NiL+ and Cu2+ was also investigated. The reaction is independent of [Cu2+] and has the same rate and activation parameters as the dissociation of NiL2+. In contrast to open chain ligands, no mixed complex CuNiL4+ as intermediate was observed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19790620809
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  • 5
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands, IVPart III, see [1].. Synthesis, Properties and Kinetics of Complexation with Three N-methyl Substituted 1,4,8,11-tetraazacyclotetradecanes (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 1035-1042 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, properties and complexation of 1-methyl-1,4,8,11-tetraazacyclotetradecane (1-MeCyclam-14), 1,5-dimethyl-1,5,8,12-tetraazacyclotetradecane (2-MeCyclam-14) and 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4-MeCyclam-14) are described.While the Ni2+ and Cu2+ complexes of 1-MeCyclam-14 and 2-MeCyclam-14 exhibit square planar geometries, 4-MeCyclam-14 forms Ni2+ and Cu2+ complexes, whose absorption spectra are best explained by assuming pentaco-ordination of the metal ions.The complexation rate of the three N-methyl substituted macrocycles with Cu2+ and Ni2+ is slower than can be accounted for by water exchange and little affected by introducing methyl groups at the nitrogens. Both results are in contrast to what is known for open chain amine ligands. A mechanism for the complexation is proposed, which also explains why the products of the reaction of 4-MeCyclam-14 with Cu2+ and Ni2+ are pentaco-ordinated.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570409
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  • 6
    Electronic Resource
    Electronic Resource
    Vitamin D3 Metabolites IIPart I, see [1].. Further Syntheses of 25-Hydroxycholesterol (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 771-781 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zwei weitere Synthesen von 25-Hydroxycholesterin (10) ausgehend von Pregnenolon (1) bzw. O-acetylpregnenolon (13) werden beschrieben. Dabei wird jedesmal auch das noch unbekannte 20(S)-25-Hydroxycholesterin (11) erhalten. Fernerhin wird ein Zusammenhang zwischen der chemischen Verschiebung der NMR.-Signale der C(21)-Methylgruppe und der Stereochemie am C(20) festgestellt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570331
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  • 7
    Electronic Resource
    Electronic Resource
    Die absolute Konfiguration von Carquejol und verwandten o-Menthan-Derivaten (1969)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 52 (1969), S. 1253-1258 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of carquejol is amended to that of cis-3-hydroxy-o-mentha-1(7),4,8-triene; the chirality has been confirmed as 2 R, 3 S by correlation with the (-)-cis-o-menthane obtained from carquejol and that from (+)-verbenene of known absolute configuration.The two double bonds of the dihydrocarquejol system (15 and 16) constitute a helical system, that especially in the case of the acetate (16) fixes the isopropenyl group in such a way that a very high Δ∊ value in the CD. curve is observed. The conformational significance of this phenomenon is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19690520511
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  • 8
    Electronic Resource
    Electronic Resource
    Mass Spectrometry and Organic Analysis, part 14.For part 13, see [1]. The photolysis and mass spectra of medium and large ring ketones from C9 to C16Dedicated to Dr. Roger Firmenich on the occasion of his 65th birthday (1971)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 54 (1971), S. 1759-1767 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photolysis of cyclic ketones from C9 to C16 has been carried out, and formation of cyclobutanols observed in only C11 to C16. Although in the mass spectrometer cyclobutanols are not formed, an initial transfer of a γ-hydrogen atom to the carbonyl group is shown to occur in the mass spectra of all cyclic ketones higher than C10.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19710540703
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  • 9
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands, VPart IV see [1].. Formation and dissociation kinetics of the pentaco-ordinated Ni2+, Cu2+, Co2+ and Zn2+ complexes with 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 1328-1333 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation and dissociation kinetics of the pentaco-ordinated Cu2+, Ni2+, Co2+ and Zn2+ complexes with 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (4-MeCyclam-14) was studied by pH-stat techniques and spectrophotometrically. The rates of the reactions between 4-MeCyclam-14 and each of the four metal ions, although slower than normal complexations by a factor of 103-104, closely follow the order Cu2+ 〉 Zn2+ 〉 Co2+ 〉 Ni2+, found for the rate of water exchange. This implies that beside water exchange an other constant factor plays an important role in the rate determing step. The dissociation of the pentaco-ordinated 4-MeCyclam-14 complexes is acid catalyzed. The limiting rate for acid dissociation is not reached even in 2.5M HNO3 in the case of Ni(4-MeCyclam-14)2+. From the formation and dissociation rates stability constants have been calculated, which do not show any macrocyclic effect.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570509
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  • 10
    Electronic Resource
    Electronic Resource
    Transition Metal Ions and Amides, VIPart V, s.[1].. Complexation of the neutral and the anionic forms of 3, 7-diazanonanedioic acid diamide and 3, 7-diazanonanedioic acid diethylamide with Cu2+ and Ni2+ (1974)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 286-293 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two tetradentate ligands, 3, 7-diazanonanedioic acid diamide (DANA) and 3, 7-diazanonanedioic acid diethylamide (DANEA) have been synthesized and their complexes with Cu2+ and Ni2+ studied potentiometrically and spectrophotometrically. Three monomeric species, ML, MH-1L, and MH-2L, are formed. In ML, the two carbonyl oxygens are bound to the metal ions. Whilst Cu2+ gives complexes CuH-1DANA+ and CuH-1DANEA+ with one deprotonated amide group, the corresponding Ni2+ chelates do not exist in detectable concentrations. CuH-2DANA and NiH-2DANA are formed below pH 9. In the case of the diethyl derivative DANEA, however, steric interaction strongly hinders coordination of two deprotonated amide groups.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19740570203
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