ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By mixing acidic solutions of 1,4,8,11-tetraazacyclotetradecane (Cy) with CuX2 (X = Cl-, Br-), either the hexahalocuprates of the tetraprotonated form of the macrocycle ([CyH4] [CuX6]) or the tetrahalocuprates of its Cu2+ complex ([CuCy] [CuX4]) are obtained. The structures of the chloro derivatives are established by X-ray diffraction analysis. In [CyH4] [CuCl6], the Cu2+ is in a tetragonally distorted octahedral geometry with four short and two long Cu—Cl bonds. The tetraprotonated macrocycle is centrosymmetric, and its conformation is exodentate, so that the four ammonium groups are as far as possible from each other to minimize the electrostatic repulsion. In [CuCy] [CuCl4], the Cu2+ ion complexed by the macrocycle is surrounded by four N-atoms in a square-planar arrangement. In addition, the axial positions are occupied by two Cl- ions of two CuCl42- units, which act as bridges. The macrocycle is in the trans-III-configuration. The other Cu2+ ion is coordinated by four Cl- ions in a distorted tetrahedral geometry. IR and VIS spectra of the chloro and bromo derivatives are used to discuss the structure of the bromo species.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three N2S2 macrocycles (3, 10, 12) carrying an amino group as a pendant arm have been synthesized and their complexation properties towards Ni2+ and Cu2+ studied. The crystal structures of the Cu2+ complexes with 10-methyl-1,4-dithia-7,10-diazacyclododecane-7-ethanamine (3) and 11-methyl-1,4-dithia-8,11-diazacyclotetradecane-8-ethanamine (10) show that, in both cases, the Cu2+ is pentacoordinated by the four donor atoms of the macrocycle and the amino group of the side chain. In aqueous solution, however, two forms of the complexes with stoichiometries [MLH] and [ML] (M = Cu2+ or Ni2+) have been observed. In [MLH], the amino group is protonated and does not bind to the metal ion, whereas in [ML] the amino group is bound, and a pentacoordinated geometry results. The pKa values for the equilibrium [ML] + H+⇌[MLH]+ decrease in the order 12 〉 10 〉 3, indicating that the 2-aminoethyl side chain binds better to the Cu2+ than the 3-aminopropyl side chain. Cyclic voltammetry for the Cu2+/Cu+ pair shows that the 2-aminoethyl pendant arm stabilizes the Cu2+ oxidation state, when the metal ion is in the 14-membered ring (10), whereas it stabilizes Cu+ for the 12-membered macrocycle (3).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two bis-macrocycles 4 and 5 in which the tetraaza units are separated by a chain of different length, have been synthesized using 1,4,7-tritosyl-1,4,7,11-tetraazacyclotetradecane as starting compound and bifunctional alkylating agents. The bis-macrocycles give binuclear complexes with Ni2+ and Cu2+, the properties of which have been studied to obtain information about the interaction of the two subunits as a function of the distance. The VIS spectra of the Ni2+ and Cu2+ complexes indicate that both metal ions are in a square-planar geometry as expected from the results of the analogous complexes with 1,4,7,11-tetraazacyclotetradecane 7. Cyclic voltammetry and differential pulse polarography of the binuclear Ni2+complexes in CH3CN show a single two-electron step for ligand 5, whereas two distinct one-electron redox processes can be observed for ligand 4, indicating that the two metal ions interact with each other when the chain length is shorter. Similarly, the EPR studies of frozen solutions of the binuclear Cu2+ complexes clearly show that a magnetic dipolar interaction between the two paramagnetic centers exists, and that the strength of it depends upon the length of the bridge. Finally, from the X-ray structures of the binuclear Ni2+ complexes with 4 and 5, it is seen that the two rings are kept apart as far as possible, the distances between the two metal ions determined in the solid correlate well with the observations in solution.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1841-1857 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Entirely different product distributions were observed when the bisdiazo compound 1 was irradiated by a conventional lamp (254 nm) on the one hand and by a pulsed excimer laser (248 nm) on the other. Continuous photolysis gave a complex reaction mixture (Scheme 2), of which eight products were identified. Pulsed laser photolysis gave (11E)-dibenzocyclooctatriene 20 as a new product in 49% yield (Scheme 4). We postulate that compound 20 is formed via the biscarbene intermediate 18 which results from the sequential absorption of two photons by a single molecule within a single laser pulse.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1325-1333 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of N2S2-macrocycles with ring sizes varying between 12 and 16, as well as two 12-membered N2S2-rings with a pendant carboxylic and amino group, respectively, were synthesized. Their complexation properties towards Ag+ were studied by pH titrations and by potentiometry with a silver electrode. The observation that 1:1 ([AgLH2]3+, [AgLH]2+, [AgL]+) and 1:2 species ([AgL2H2]3+, [AgL2H]2+, [AgL2]+) were formed is interpreted by postulating that Ag+ can bind either to the S-donors only, or to both the N- and S-atoms. The most stable complex [AgL]+ in the series of the nonfunctionalized macrocycles was found for the 12-membered N2S2-ring 3. The stability of it increased when an additional donor group was introduced into the side chain. The highest formation constant (logβ110 = 14.43(1)) was obtained with the 12-membered ring 12 carrying the ethanamine side chain. In view of a radiochemical application, all Ag+ complexes were tested in blood serum for their stability, but were not stable enough against transmetallation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 46 (1963), S. 2285-2297 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Es wird die Aufnahme von Gleichspaiinungspolarogrammen von Blei aus wässerigen Chlorid-, Bromid-, Nitrat- und Acetatlösungen an intermittierend polarisierten Silber-, Gold- und Platinelektroden beschrieben.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...