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  • 1
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lifetime of cation selective carrier-PVC-membranes partially depends on the components' remaining in the membrane. An exchange of monomeric by polymeric plasticizers with low tendency to migrate lengthens the function time drastically. Other than for Na+ - and NH4+-selective membranes, it is essential for K+ - and Ca2+-selective membranes and optional for H+-selective membranes to incorporate lipophilic anions in order to make the phase transfer catalysis more efficient. The resistence to saponification of phthalic acid polyester gives H+-selective membranes a high stability of measured values even in the alkaline range.For anion selective PVC-membranes, instead of cation selective plasticizers the plasticizing qualities of a liquid charged ligand should be used.The tubular carrier-PVC-membranes of our ion selective flow through measuring systems are diffusion welded to the ends of two PVC-tubes [1] so that they are absolutely tight with no risk of potential leakage. Migration of the membrane components plasticizer and ionophore across this border as well as their extraction [2, 3] into the measuring solution [4] will naturally reduce the membrane's functionning time [5].
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted Alkinyles as Axial Ligands at Hemine Like Bound Iron(III) - Incorporation into a Spectrochemical Series.Substituted lithium alkynyles Li—C≡C—R (R = tBu, Ph, p-Cl—C6H4, Me3Si, iPr3Si, Ph3Si) react with the hemine like macrocyclic iron(III) complex 6,13-di(ethoxycarbonyl)-5, 14-dimethyl-1, 4, 8, 11-tetraazatetradeca-4,6,12,14-tetraenato[2-]iron(III)-iodide (formula 2;) in tetrahydrofuran to form anionic low-spin di-adducts [fe(C≡C—R)2]-. The incorporation of the alkynyles into a spectrochemical series of the axial ligands (studied by the sharp equatorial-ligand-to-metal CT absorption band) results in the wavelength-sequence (nm): OH- (≍ 510) « N3- (≍ 625) 〈 tBu—C≡C- (664) 〈 NH3 (666) 〈 Ph—C≡C- (692) 〈 Ph—NH2 (695) 〈 Me3Si—C≡C- (698) 〈 SCN- (713) 〈 Ph3Si—C ≡ C- (716) 〈 CN- (739) 〈 4-picoline (759) 〈 pyridine (765) 〈 nicotinamide (776) 〈 methylnicotinat (788) 〈 pyrazine (798) and points to a significant π-acceptor ability of the silyl substituents.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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