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  • 1
    Electronic Resource
    Electronic Resource
    Liquid membrane transport of supramolecular complexes of some amines and amino acids with macrocyclic ligands (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 23 (1995), S. 167-174 
    Details
    ISSN: 1573-1111
    Keywords: Amines ; amino acids ; liquid membrane ; macrocyclic ligands ; active transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transport of some amines in protonated form was studied (viz. methylamine, dimethylamine, diethylamine andn-propylamine) and α-amino acids (l-leucine,l-methionine,l-isoleucine,l-phenylalanine,l-valine,l-α-alanine andl-cysteine). The following macrocyclic ligands were used as carriers throughout the experiments: 15-crown-5 (15C5), 18-crown-6 (18C6), benzo-18-crown-6 (B18C6), dibenzo-18-crown-6 (DB18C6), diazacrown ether [2.2] (1,7,10,16-tetraoxa-4,13-diazacyclooctadecane) and cryptand [2.2.2] (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo [8.8.8] hexacosane). The active transport, assisted by pH gradient, of amino acids and amines in protonated form as ion pairs in the presence of picrate anion was performed. The experiments suggested the influence of the ligand size, the donor atom type, and the substituents on the transport phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00709574
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  • 2
    Electronic Resource
    Electronic Resource
    The Complexation of Amino Acids by Crown Ethers and Cryptands in Methanol (1998)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 30 (1998), S. 21-28 
    Details
    ISSN: 1573-1111
    Keywords: Amino acids ; crown ethers ; cryptands ; complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Complex formation between several crown ethers and the cryptand (222) and α-amino acids in methanol was studied by calorimetric titration. The ligand structure and the donor atoms of the ligands play an important role in determining the measured values of the reaction enthalpies and entropies. However, with the exception of the diaza crown ether (22) all stability constants are of the same order of magnitude. The enthalpic and entropic contributions to the stabilities of the complexes formed compensate each other. In methanolic solution the amino acids exist in their zwitterionic form. This equilibrium can be influenced. Under acidic, neutral or basic conditions different values of the reaction enthalpies are measured for the complexation of some amino acids with 18-crown-6. These results demonstrate that the concentration of the zwitterionic form of the α-amino acids can be influenced. Thus the reaction between macrocyclic and macrobicyclic ligands and amino acids should be described by at least two different reaction schemes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007941023186
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of complex stabilities with nearly insoluble host molecules. Part II. Complexation of alkali and alkaline earth metal cations with dibenzo crown ethers in aqueous solution (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 781-785 
    Details
    ISSN: 0894-3230
    Keywords: complex stabilities ; alkali metals ; alkaline earth metals ; dibenzo crown ethers ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---An experimental method was developed to determine the stability constants with nearly insoluble ligands in homogeneous solution. This method was tested using dibenzo crown ethers, which have a very low solubility in aqueous solution. The stability constants for the complexation of alkali and alkaline earth metal cations with different dibenzo crown ethers were determined in aqueous solution. Owing to the complex formation the total concentration of the ligand in solution increases. Dibenzo crown ethers absorb in the ultraviolet spectral range, hence the increase in the ligand concentration can be easily detected. Without the knowledge of the molar absorptivities of the ligands and of the corresponding complexes and of the solubilities, the stabilities of the complexes formed can be calculated under certain assumptions. To verify these assumptions, the solubilities of the dibenzo crown ethers and the molar absorptivities were determined. The kinetics of the solubilization process of the ligands was followed by spectrophotometric measurements. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of mono-, oligo- and polyamide-cucurbituril rotaxanesDedicated to Prof. Hartwig Höcker on the occasion of his 60th birthday (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 19 (1998), S. 59-63 
    Details
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mono-, oligo- and polyamide rotaxanes with the macrocycle cucurbituril are synthesized easily with high yields by interfacial condensation. The complex of cucurbituril with 1,6-hexanediammonium ion is used as preorganized structure. With different acid and diacid chlorides a great variety of amiderotaxanes and polyrotaxanes can be synthesized. The characterization is difficult due to the low solubility of cucurbituril and rotaxanes. But with the methods of IR, DTA, 1H NMR and elemental analyses, the existence of the rotaxanes is shown.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Modifizierung von Faseroberflächen durch die permanente Fixierung supramolekularer Komponenten, Teil 2: CyclodextrineAuszug aus der Dissertation von U. Denter, Universität Duisburg (eingereicht). (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 248 (1997), S. 165-188 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Cyclodextrin derivatives may be fixed permanently onto different fibre surfaces by suitable functional groups using conventional technologies of textile processing. As a result of the modification process the properties of the polymers are influenced. Some examples are discussed in detail. For several ligands it is illustrated that the fixed cavities do not lose their complexing power. Thus, special functional properties can be obtained by the inclusion of specific active agents.
    Notes: Mit herkömmlichen Verfahrenstechniken der Textilveredlung werden ausgewählte Cyclodextrinderivat über geeignete funktionelle Gruppen permanent auf verschiedenen Fasermaterialien fixiert. Einige der durch die Oberflächenmodifizierung beeinflußten Eigenschaften der Polymeren werden im einzelnen diskutiert. Insbensondere kann für mehrere Liganden gezeigt werden, daß die verankerten molekularen Hohlräume nicht die Fähigkeit verlieren, hydrophobe organische Verbindungen zu komplexieren. Somit lassen sich durch den Einschluß spezifischer Wirksubstanzen spezielle funktionelle Eigenschaften erzielen.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052480111
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  • 6
    Electronic Resource
    Electronic Resource
    Modifizierung von Faseroberflächen durch die permanente Fixierung supramolekularer Komponenten, Teil 1: GrundlagenAuszug aus der eingereichten Dissertation von U. Denter, Universität Duisburg 1997. (1997)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 248 (1997), S. 153-163 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: A new conception for modification of textile surfaces by permanent fixation of supramolecular components is explained. The principle of selective complexation is illustrated. Cyclodextrins, aza crown ethers, calixarenes, cyclotriveratrylenes and fullerenes are mainly suggested as suitable ligands for that procedure. The chemical structure and the complexation behaviour of the substances are described. Some surface properties which may be obtained with the ligands are especially emphasized.
    Notes: Ein neues Konzept zur Modifizierung von Faseroberflächen durch permanente Fixierung supramolekularer Verbindungen wird vorgestellt, und das Prinzip der selektiven Komplexierung wird erklärt. Als für die Behandlung grundsätzlich geeignete Liganden werden insbesondere Cyclodextrine, Azakronenether, Calixarene, Cyclotriveratrylene und Fullerene hinsichtlich ihrer chemischen Struktur sowie ihrer komplexierenden Eigenschaften beschrieben. Einige erreichbare Oberflächeneffekte werden hervorgehoben.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1997.052480110
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  • 7
    Electronic Resource
    Electronic Resource
    Unusual Complexation Behavior of Metallomacrocycles Based on Isothiosemicarbazides with Respect to Alkali and Alkaline Earth Metal Ions: Novel 2:1 Associates (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 1089-1093 
    Details
    ISSN: 0009-2940
    Keywords: Metallomacrocycles ; Nickel complexes ; Complexation reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions between alkali and alkaline earth metal ions and nickel(II) macrocycles based on S-alkylated isothiosemi-carbazides with different crown ether cavity size were studied in propylene carbonate by spectrophotometric and calorimetric titrations. Metallomacrocycles 1 and 2 exhibit normal behavior on 1:1 complexation with alkali- and alkaline earth metal ions and resemble in this respect 15C5 and 18C6, respectively. The most stable complexes are formed by these “ligands” when the diameter of the cation and the crown ether hole have approximately the same size. The most striking feature of the complexation processes studied is the formation of 1:2 metal-ligand associates even in the case of the smallest cations. These associates are very different from “normal” crown ether sandwich complexes. In reality, the particle formed is an associate between a 1:1 complex, in which the corresponding metal ion is well accommdated inside the ligand cavity, and a second metallomacrocyclic ligand. Their formation is disfavored by enthalpic contributions. A special kind of “switch” from these associates to normal sandwich complexes takes place in the case of 1, when the cation diameter compared to hole size increases. The macrocycle 2 forms this kind of associates with all akali and alkaline earth ions.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951281106
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