Stoichiometry of An(iii)–DMDOHEMA complexes formed during solvent extraction. Issue 32 (25th July 2018)

• Record Type: Journal Article
• Authors: Weßling, Patrik; Trumm, Michael; Geist, Andreas; Panak, Petra J.
• Is Part Of: Dalton transactions. Volume 47:Issue 32(2018)
• Page Start: 10906
• Page End: 10914
• Publication Date: 2018-07-25
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c8dt02504e
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : N, N ′-Dimethyl, N, N ′-dioctylhexylethoxymalonamide (DMDOHEMA) is used to separate An(iii ) and Ln(iii ) from fission products in several liquid–liquid extraction processes that aim at recycling actinides. Abstract : N, N ′-Dimethyl, N, N ′-dioctylhexylethoxymalonamide (DMDOHEMA) is used to separate An(iii ) and Ln(iii ) from fission products in several liquid–liquid extraction processes that aim at recycling actinides. The stoichiometry of the extracted complexes is important for a complete understanding of the processes. The presented work focuses on the complexation of Cm(iii ) with DMDOHEMA studied by TRLFS in mono- and biphasic (solvent extraction) systems. The formation of [Cm(DMDOHEMA) n ] 3+ ( n = 1–3) in 1-octanol containing 1.7 mol L −1 of water with log β ′1 = 2.6 ± 0.3, log β ′2 = 4.0 ± 0.5, log β ′3 = 4.3 ± 0.5 was confirmed. In addition, fluorescence lifetime measurements indicated the formation of a 1 : 4 complex. Furthermore, solvent extraction experiments were performed, varying the proton and nitrate concentrations. TRLFS measurements of organic phases confirmed the existence of two species, [Cm(DMDOHEMA)3 (NO3 )(H2 O)1–2 ] 2+ (dominant at high proton and nitrate concentrations) and [Cm(DMDOHEMA)4 (H2 O)] 3+ (dominant at low proton and nitrate concentrations). To support the proposed stoichiometries, vibronic side-band spectroscopy (VSBS) was employed, allowing the observation of vibrations of functional groups coordinated to the probed metal ion. Clear differences between the vibronic side bands of the 1 : 3 and 1 : 4 complex in the range of 900–1300 cm −1 were observed. Vibrational spectra calculated by DFT complimented the experimental data and confirmed the proposed stoichiometries. They revealed a monodentate coordination mode of the nitrate and two water molecules in the 1 : 3 complex.