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Issue 24, 2017
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Thermodynamic analysis of alkali metal complex formation of polymer-bonded crown ether

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Abstract

The complex formation of two crown ethers with colored alkali metal salts was investigated by UV/Vis spectroscopy. Complexation was accomplished with free benzo-15-crown-5 (B15C5) and 15-crown-5 bonded to a diblock copolymer (Poly15C5). The diblock copolymer was synthesized by two controlled polymerization techniques and copper(I)-catalyzed azide–alkyne cycloaddition. Depending on the inserted cation, 1 : 1- or 1 : 2-complexes are formed. A significant difference of the stability constants was determined by concentration dependence solvent extraction with sodium or potassium salt. For Poly15C5 the stability constants increase for both salts compared to the stability constants of B15C5, which suggests a more effective complexation. Evaluation of the thermodynamics (ΔH, ΔS, ΔG) of cation complexation was achieved by temperature dependence phase extraction on the basis of established thermodynamic equations. Remarkably, in all cases the entropic gain seems to be the major propulsion facilitating the complexation between alkali metal salts and crown ethers. Indeed, by using Poly15C5 a more pronounced dependency of enthalpy and entropy on the complex formation is calculated.

Graphical abstract: Thermodynamic analysis of alkali metal complex formation of polymer-bonded crown ether

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Publication details

The article was received on 22 Apr 2017, accepted on 31 May 2017 and first published on 01 Jun 2017


Article type: Paper
DOI: 10.1039/C7CP02651J
Citation: Phys. Chem. Chem. Phys., 2017,19, 15924-15932
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    Thermodynamic analysis of alkali metal complex formation of polymer-bonded crown ether

    A. Bey, O. Dreyer and V. Abetz, Phys. Chem. Chem. Phys., 2017, 19, 15924
    DOI: 10.1039/C7CP02651J

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