Remarkable Enhancement in Extraction of Trivalent f-Block Elements Using a Macrocyclic Ligand with Four Diglycolamide Arms: Synthesis, Extraction, and Spectroscopic and Density Functional Theory Studies

Abstract

A multiple diglycolamide (DGA)-containing ligand having four DGA arms tethered to a tetraaza-12-crown-4 ring, viz. 2, 2′,2′′,2′′′-(((1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetrakis(2-oxoethane-2,1-diyl)) tetrakis (oxy)) tetrakis(N,N-dioctylacetamide) (T12C4ODGA), was synthesized and evaluated for the extraction of different actinide and lanthanide ions, viz. Am 3+ , Eu 3+ , Pu 4+ , Np 4+ , and UO 2 2+ . The extraction efficiency of the present ligand was found to be the highest reported so far, more specifically for the trivalent metal ions Am 3+ and Eu 3+ , when one considers the very low ligand concentration used in the present study, compared to that of the various previously reported multiple DGA-based ligands. The nature of the complexes formed during the extraction of Eu 3+ was investigated using time-resolved fluorescence (TRFS) and extended X-ray absorption fine structure (EXAFS) spectroscopy. Both the solvent extraction and TRFS studies indicated the presence of 1:1 and 1:2 complexes during the extraction of Am 3+ and Eu 3+ having three inner-sphere water molecules in the 1:1 complex. Density functional theoretical (DFT) studies were performed on the Am 3+ and Eu 3+ complexes of both T12C4ODGA and an analogous compound having methyl groups in place of the n-octyl groups, and the DFT results of the T12C4ODGA nicely explain the extraction behavior of Am 3+ and Eu 3+ .

Role of diluent in the unusual extraction of Am3+ and Eu3+ ions with benzene-centered tripodal diglycolamides: local structure studies using luminescence spectroscopy and XAS

“…2). 2,24 The addition of phase modifiers leads to a change in the physical/chemical parameters of the solvent, such as water or acid uptake, polarity etc., which can also influence the extraction of Ln 3+ /An 3+ with a given ligand. 33,34 For both ligands the acid and water uptake appeared to be very much similar (Table 1).…”

“…The complex chemistry of diglycolamide (DGA) ligands with lanthanide (Ln)/actinide (An) metal ion extraction is quite fascinating. [1][2][3][4][5][6][7] Although they are quite similar to malonamides/glutaramides (Fig. 1) as both have two amide groups for complexation, the 'ether' linkage present at the centre of the DGA makes it a stronger complexing agent and, hence, extracting agent.…”

Complexation and Separation of Trivalent Actinides and Lanthanides by a Novel DGA Derived from Macrocyclic Crown Ether: Synthesis, Extraction, and Spectroscopic and Density Functional Theory Studies

“…Subsequently, 2,2′,2″,2‴-(((1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)-tetrakis­(2-oxoethane-2,1-diyl))­tetrakis­(oxy))­tetrakis­( N , N -dioctylacetamide) (T12C4ODGA, Figure ) has been reported. Compared with T9C3ODGA, the ability of this ligand to extract trivalent lanthanide/actinide metal ions was significantly improved ( n -dodecane, D Am > 500, D Eu > 10 3 ) . According to the experimental and theoretical results, the ligands T9C3ODGA and T12C4ODGA formed the same type of extraction complex (M/L = 1:1 and 1:2), and the 1:2 species was the optimal structure during the extraction process.…”

Effect of diluent on the extraction of europium(iii) and americium(iii) with N,N,N′,N′-tetraoctyl diglycolamide (TODGA)

“…The family of diglycolamides are known extracting agents for trivalent lanthanides and actinides in solvent extraction, with expected application in partitioning and transmutation of a nuclear fuel [22][23][24][25] and in radiopharmaceutical industry for 225 Ac production. [26][27][28][29] While the behavior of diglycolamides with respect to equilibrium distribution ratios, acid extraction and kinetics was extensively evaluated, [30][31][32][33][34][35][36][37][38][39][40][41][42] the effect of the diluent on the extraction was evaluated only in a few studies. [42][43][44][45][46][47] From the available data, correlations of diluent properties against the distribution ratios seems rather difficult.…”