Studies on 1,2-Bis(O-Aminophenoxy)Ethane-N,N,N′,N′;-Tetraacetic Acid Chelates of the Tripositive Lanthanide Ions |
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Authors: | Tong-Ming Hseu Kei-Lee Liu |
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Abstract: | The acid dissociation constants of 1,2-bis(cis-aminophenoxy)ethane-N,N,N′,N′;-tetraacetic acid (H4BAPAT or H4Z), and the stability constants of its chelates with tripositive rare-earth metal ions have been determined by the potentiometric titration and mercury indicator electrode methods at 15°, 25′ and 35°C and an ionic strength of 0.1 (KNO3). The existence of a monohydrogen chelate species, LnHZ, and the normal chelate, LnZ?, is illustrated. Enthalpy and entropy changes characterizing the formation of the normal chelates and the dissociation of the last two protons of chelating acid have been calculated at 25°C. These functions have been compared with corresponding values for related chelating agents. |
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Keywords: | Dissociation constants Formation constants: Thermodynamic Properties Ln(III)-BAPTA chelates |
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