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Issue 6, 2003
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Hydrogen-bond forming ionophore for highly efficient transport of phosphate anions across the nitrobenzene–water interface

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Abstract

Thiourea-based hydrogen-bond forming ionophore 2, α,α′-bis(N′-p-nitrophenylthioureylene)-m-xylene, is synthesized and investigated by using ion transfer polarography for the facilitated transfers of H2PO4, HPO42− and Cl across the nitrobenzene–water interface. Bis-thiourea 2 has a significant ability to assist H2PO4 transfer across the interface whereas its counterpart, N-(p-nitrophenyl)-N′-propylthiourea (ionophore 3), cannot facilitate the transfer of this hydrophilic anion. The H2PO4 transfer assisted by 2 is based on the formation of a 2:1 complex between H2PO4 and ionophore, and the transfer reaction is more stable by over −12 kJ mol−1 than the case of 3. The stabilization of the H2PO4 transfer for 2 is even stronger by −11 kJ mol−1 than that for bis-thiourea 1, 2,7-di-t-butyl-4,5-bis(N′-butylthioureylene)-9,9-dimethylxanthene, which forms a 1:1 complex through the formation of four hydrogen bonds. Bis-thiourea 2 is also able to facilitate transfers of HPO42− and Cl by the formation of 1:1 complex. As compared to bis-thiourea 1, HPO42− transfer by 2 is significantly stabilized by −27 to −31 kJ mol−1 while the stabilization of the Cl transfer is relatively moderate (−6.1 kJ mol−1). These binding properties of bis-thiourea 2 are discussed for the design of phosphate-selective ionophores for use in two-phase distribution systems such as ion-selective electrodes.

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Publication details

The article was received on 28 Jan 2003, accepted on 26 Mar 2003 and first published on 17 Apr 2003


Article type: Paper
DOI: 10.1039/B301141K
Citation: Analyst, 2003,128, 663-669
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    Hydrogen-bond forming ionophore for highly efficient transport of phosphate anions across the nitrobenzene–water interface

    S. Nishizawa, T. Yokobori, R. Kato, K. Yoshimoto, T. Kamaishi and N. Teramae, Analyst, 2003, 128, 663
    DOI: 10.1039/B301141K

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