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  • 1
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands, VIPart V see [1].. The role of substituents on the complexation rate of transition metal ions with several 1,4,7,10-tetraazacyclotridecanes (1975)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 58 (1975), S. 1358-1366 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 12,12-Dimethyl-1,4,7,10-tetraazacyclotridecane (I), 11,13-dimethyl-1,4,7,10-tetraazacyclotridecane (II), 11,11,13-trimethyl-1,4,7,10-tetraazacyclotridecane (III) and 1,4,7,10,12,12-hexamethyl-1,4,7,10-tetraazacyclotridecane (IV) have been synthesized and their properties are described.While the Ni2+ and Cu2+ complexes of I-III have square planar geometries, those of IV are pentacoordinate according to their absorption spectra. Similarly, while the Co2+ complex of I is octahedral and readily oxygenated, the analogous complex with IV is pentacoordinate and not sensitive to oxygen.The rate of complexation of these ligands with Cu2+ and Ni2+ decreases in the order I 〉 II 〉 III ≫ IV, indicating that the number as well as the position of the methyl groups are important. Finally for Cu2+ the formation of the thermodynamic stable end product is slown down by methyl substitution in α-position to the coordinating nitrogen atoms (ligand II and III) so that an intermediate can be observed, whereas with I Cu2+ directly forms the end product.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19750580514
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  • 2
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands. XPart IX, see [1].. On the metal complexation kinetics of two N4-macrocycles containing a pyridine ring (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 2291-2296 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complexation kinetics of the two macrocycles 1 and 2 with Co2+, Ni2+, Cu2+ and Zn2+ have been measured by pH-stat techniques. The rates are first order in metal and ligand concentration and depend upon the pH. This results from the different reactivities of the various protonated species of the macrocyclic tetraamines. The resolved rate constants are given in Table 2.In comparison with other 14-membered cyclic aliphatic tetraazasystems 1 and 2 react more slowly with metal ions. This might be a consequence of the more rigid structure induced by the pyridine ring.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610702
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  • 3
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands. XIPart X, see [1].. Ring size effect on the complexation rates with transition metal ions (1978)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 61 (1978), S. 2296-2306 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 12-16 membered tetraazamacrocycles 1-6 were synthesized, their protonation constants and complexation kinetics measured at 25° and I = 0.50. The results of Table 1 Show that pK3H is strongly influenced by the ring size whereas pK2H and pK1H are relatively insensitive to it. This can be understood in terms of electrostatic interactions of the positive charges when located on adjacent amino groups.The kinetics of complex formation between the macrocyclic ligands and several transition metal ions have been studied by pH-stat and stopped-flow techniques and the results have been analyzed as bimolecular reactions between the metal ion and the different protonated species of the ligands. The rate constants, given in Table 2, show that the macrocycles react less rapidly than analogous open chain amines. However, for a given protonated species of the ligand the rate of complexation follows the order Cu2+ 〉 Zn2+ 〉 Co2+ 〉 Ni2+ which parallels the sequence of their water exchange rates. For the diprotonated tetraamines LH22 reacting with Cu2+ the slower rates seem to be mainly a consequence of electrostatic interactions, since a correlation between logkLH2Cu and pK3H exists. For LH+, however, the complexation rates of a metal ion with the different macrocycles are all in one order of magnitude and do not depend in a regular way on the ring size or the basicity of the ligand. It is therefore suggested that in this case other factors such as unfavourable preequilibria must be considered as important.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19780610703
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Stability, Formation and Dissociation Kinetics of the Pentacoordinate Ni2+ and CO2+ Complexes with 1,5-Diazacyclooctane-N,N′-diacetic Acid (1975)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 58 (1975), S. 1881-1886 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stability constants of the Ni2+ and Co2+ complexes with 1,5-diazacyclooctane-N,N′-diacetic acid (H2DACODA) have been determined potentiometrically in 0.5M KNO3 at 25°. Only M(DACODA) and M(DACODA)OH- were observed.In addition the formation and dissociation kinetics of the pentacoordinate complexes M(DACODA) has been studied in aqueous solution using a stopped-flow technique. Formation follows the rate law vf = kf [M2+] [HDACODA-]/[H+], which can be interpreted as a bimolecular process either between M2+ and DACODA2- (kM,LML) or between MOH+ and HDACODA- (kMOH,HLML). The second order rate constants kM,LML are much higher than those expected from water exchange and can only be explained by a strong internal conjugate base effect. In the limiting case, however, this is equivalent to the second possible explanation, which assumes MOH+ and HDACODA- as reactive species. The dissociation rate is given by vd = (kML + kHML [H+]) · [M(DACODA)].
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19750580703
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  • 6
    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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  • 7
    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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  • 8
    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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