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Unfolding the complexation and extraction of Am3+ and Eu3+ using N-heterocyclic aromatic diphosphonic acids: a combined experimental and DFT study

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Abstract

Phosphonate based ligands are well known for the extraction of ‘f’ block elements. Three N,O-donor N-heterocyclic aromatic diphosphonate ligands were evaluated in the present work for the extraction/separation studies of Am3+ and Eu3+. Complexation studies in aqueous medium using luminescence titration indicated the formation of anionic complexes in the case of Eu3+. Two phase liquid–liquid extraction studies were, therefore, carried out by employing Aliquat-336 as the liquid anion exchanger. The results indicated the formation of a species with a metal–ligand stoichiometry of 1 : 3 in the case of pyridine-2,6-diphosphonic acid (PyPOH). In the case of 2,2′-bipyridine-6,6′-diphosphonic acid (BipyPOH), however, a 1 : 2 complex was extracted and 1,10-phenanthroline-2,9-diphosphonic acid (PhenPOH) extracts the Am3+ and Eu3+ ions by forming both 1 : 2 and 1 : 3 complexes. Formation of these kinds of anionic complexes was further confirmed using electrospray ionization mass spectrometry (ESI-MS). DFT calculations predicted the structure of the anionic complexes. The non-selectivity of these kinds of ligands between Am3+ and Eu3+ was attributed to the presence of unfavorable covalent interactions in the metal–ligand bonds.

Graphical abstract: Unfolding the complexation and extraction of Am3+ and Eu3+ using N-heterocyclic aromatic diphosphonic acids: a combined experimental and DFT study

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Publication details

The article was received on 22 Aug 2019, accepted on 02 Oct 2019 and first published on 02 Oct 2019


Article type: Paper
DOI: 10.1039/C9DT03422F
Dalton Trans., 2019, Advance Article

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    Unfolding the complexation and extraction of Am3+ and Eu3+ using N-heterocyclic aromatic diphosphonic acids: a combined experimental and DFT study

    A. Bhattacharyya, S. A. Ansari, P. I. Matveev, G. G. Zakirova, N. E. Borisova, V. G. Petrov, T. Sumyanova, P. K. Verma, S. N. Kalmykov and P. K. Mohapatra, Dalton Trans., 2019, Advance Article , DOI: 10.1039/C9DT03422F

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