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  • 1
    Electronic Resource
    Electronic Resource
    Stability constants and thermodynamic data for complexes of 12-crown-4 with alkali metal and alkaline-earth cations in methanol solutions (1987)
    Springer
    Journal of solution chemistry 16 (1987), S. 181-190 
    Details
    ISSN: 1572-8927
    Keywords: Crown ethers ; cryptands ; calorimetry ; potentiometry ; conductometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation of 1:1- and 2:1-complexes of the crown ether 12C4 with mono- and bivalent cations was studied in methanol solutions by calorimetric, potentiometric and conductometric titrations. It is shown that not all donor atoms of the ligand 12C4 take part in complex formation. The accuracy of the three experimental methods are checked by comparing the results for the complexation of alkali ions with crown ether 18C6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646985
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of acetonitrile on complex formation of crown ethers containing different donor atoms (1988)
    Springer
    Journal of solution chemistry 17 (1988), S. 277-286 
    Details
    ISSN: 1572-8927
    Keywords: Acetonitrile ; crown ethers ; glymes ; alkali metal ions ; calorimetric titrations ; potentiometric titrations ; complex formation ; ligand solvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The complexation reactions of crown ethers with monovalent cations and Ba2+ were studied in acetonitrile solutions by means of calorimetric and potentiometric titration. The reaction enthalpies measured clearly demonstrate the influence of the interactions between 18-crown-6 and the acetonitrile solvent molecules. Changing the donor atoms or other substituents on the ligand molecule can exert a strong influence on the interactions with the solvent. Thus, all the reaction enthalpies measured for the reaction of 15-crown-5 with different cations are higher compared with 18-crown-6. On comparison with results in methanol, an approximate estimation is made of the influence of solvent molecules on the reaction enthalpies measured in acetonitrile. Due to the strong interaction between silver ion and acetonitrile, complex formation is only observed with crown ethers containing additional nitrogen or sulphur donor atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646180
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  • 3
    Electronic Resource
    Electronic Resource
    The complexation of alkali metal ions by crown ethers, aza crown ethers, and cryptands in propylene carbonate (1989)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 7 (1989), S. 581-588 
    Details
    ISSN: 1573-1111
    Keywords: Crown ethers ; cryptands ; solvent influence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reactions between alkali metal ions and crown ethers, aza crown ethers, and cryptands in propylene carbonate were studied by potentiometric and calorimetric titrations. The most stable complexes formed by macrocyclic and macrobicyclic ligands are when the ligand and cation dimensions are comparable. On comparing the complex stabilities of crown ethers and aza crown ethers of the same size, crown ethers were, on the whole, found to form the most stable complexes, with the exception of the lithium cation. Enthalpic factors are responsible. Substitution of the amino group protons of the aza crown ethers by benzyl groups leads to a high increase in values of the reaction enthalpy. This effect is partly compensated by entropic contributions. The bulky benzyl groups reduce the ligand solvent interactions and induce a ligand conformation with the lone pair of electrons from the nitrogen donor atoms which are more or less directed inside the cavity. The thermodynamic data for the transfer from methanol to propylene carbonate indicate that the ligands containing nitrogen show specific interactions with methanol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01084708
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  • 4
    Electronic Resource
    Electronic Resource
    Complexation of alkali- and alkaline-earth cations by poly(oxyethylene)s in methanol (1986)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 187 (1986), S. 423-430 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Stability constants and thermodynamic values for the reaction of alkali and alkaline-earth cations with poly(oxyethylene)s in methanol were measured by means of calorimetric titration. The apparent molecular weights of the ligands were determined by means of calorimetric end point titration. This method gives direct information on the composition of the complex formed in solution. The measured stability constants for a given ligand with K+, Rb+, Cs+, and Ba2+ ions are all of the same order of magnitude. Poly(oxyethylene)s with high molecular weight are able to surround cations completely. The reaction enthalpies for the reaction with poly(oxyethylene)s reach higher values as compared to crown ethers. From these data, the bond energies between a complexed cation and a single donor atom of the ligand were calculated for the first time.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1986.021870221
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  • 5
    Electronic Resource
    Electronic Resource
    Komplexierung von Blei(II) durch Azakronenether und Kryptanden in Methanol (1985)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 3408-3412 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexation of Lead(II) by Aza Crown Ethers and Cryptands in MethanolThe stability of PbII complexes with the mono- and bicyclic ligands 1 - 5 in methanol was determined by potentiometric titrations using an ion-selective lead(II) electrode. Reaction enthalpies ΔH were measured by calorimetric titrations. Substitution of the protons at the nitrogen atoms of aza crown 1b by the long decyl chains in 1d leads to a great increase in ΔH, whereas the complex stability is scarcely influenced. Benzo anellands (3, 4) reduce the ligand flexibility and cause a decrease in reaction enthalpies. The reaction entropies are nearly unchanged.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19851180837
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  • 6
    Electronic Resource
    Electronic Resource
    Stabilitätskonstanten und thermodynamische Werte für die Bildung von 1:1- und 2:1-Komplexen von Kronenethern mit Alkali- und Erdalkali-Ionen in Methanol (1985)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 2746-2756 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Stability Constants and Thermodynamic Values for the Formation of 1:1- and 2:1-Complexes of Crown Ethers with Alkali and Alkaline-earth Ions in MethanolThe determination of stability constants and thermodynamic values for the reaction of crown ethers with alkali-, alkaline-earth ions, and the silver ion was achieved by calorimetric titration in methanol. Through modification of the experimental conditions it is possible to measure separately the formation of 1:1- and 2:1-complexes (ratio of ligand to cation). With the exception of Ag+ and Ca2+ all ions examined form both kinds of complexes with the various 15 C 5 ligands. The complex stabilities are influenced by enthalpic and entropic contributions. 18 C 6 and DC 18 C 6, having a bigger diameter than 15 C 5, show a definite increase of the stability of 1:1-complexes. Only the Cs+ ion with the largest radius forms 2:1-complexes. A good agreement is found with values determined potentiometrically for the 1:1- and 2:1-complex formation of Na+.
    Notes: Die Komplexstabilitäten und thermodynamischen Werte für die Reaktion von Kronenethern mit Alkali-, Erdalkali-Ionen und dem Silber-Ion in Methanol wurden mittels kalorimetrischer Titrationen bestimmt. Durch Veränderung der experimentellen Bedingungen ist es möglich, sowohl die Bildung von 1:1- als auch 2:1-Komplexen (Verhältnis von Ligand zu Kation) getrennt voneinander zu messen. Mit Ausnahme von Ag+ und Ca2+ bilden alle untersuchten lonen beide Arten von Komplexen mit den verschiedenen 15 K 5-Liganden. Die Komplexstabilitäten werden von enthalpischen und entropischen Faktoren beeinflußt. 18 K 6 und DC 18 K 6, die einen größeren Durchmesser als 15 K 5 besitzen, zeigen einen deutlichen Anstieg der Stabilität der 1:1-Komplexe. 2:1-Komplexe bildet nur noch das Cs+ -Ion mit dem größten Radius. Ein Vergleich mit potentiometrisch bestimmten Daten für die 1:1- und 2:1-Komplexbildung von Na+ zeigt gute Übereinstimmung.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19851180717
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  • 7
    Electronic Resource
    Electronic Resource
    Komplexierung von AgI durch Kronenether mit unterschiedlichen Donoratomen und strukturell variierten Kryptanden in Methanol (1985)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 4297-4302 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Complexation of AgI by Crown Ethers with Different Donor Atoms and Structural Varied Cryptands in MethanolThe complex stability of AgI with mono- and bicyclic ligands 1-6 was measured by potentiometric titrations in methanol. The reaction enthalpies were estimated by means of calorimetric titrations. All examined monocyclic ligands not only containing oxygen as donor atoms form - with one exception - more stable complexes than crown ethers. Ligands with a cavity too small for Ag+ ions are able to complex the cation with a ratio of ligand to cation of 2:1. Reducing the cavity size of cryptands by benzo anellands (4, 5) leads to a small decrease in complex stability. Other structural changes at the bicyclic ligands do not influence the complex formation.
    Notes: Die Komplexstabilität von AgI mit mono- und bicyclischen Liganden 1-6 wurde durch potentiometrische Titrationen in Methanol gemessen. Mit Hilfe kalorimetrischer Titrationen wurden die Reaktionsenthalpien bestimmt. Alle monocyclischen Liganden, die neben Stickstoff auch Sauerstoff und Schwefel als Donoratome enthalten, bildeten - mit einer Ausnahme - stabilere Komplexe als reine Kronenether. Liganden, deren Durchmesser kleiner ist als der von Ag+, sind in der Lage Komplexe zu bilden, deren Zusammensetzung Ligand zu Kation 2:1 ist. Die Verkleinerung des Hohlraumes der Kryptanden durch Benzo-Anellanden (4,5) führt nur zu einer kleinen Abnahme der Komplexstabilität. Andere strukturelle Veränderungen an den bicyclischen Liganden beeinflussen die Komplexbildung nicht.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19851181102
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