Aqueous coordination complexes of neptunium

The First Structural and Spectroscopic Characterization of a Neptunyl Polyoxometalate Complex

“…Solid Na 8 HPW 9 O 34 was then added in a 1:1 PW 9 :Np molar ratio, and the mixture was dissolved in 0.2 M NaCl to yield a deep straw colored solution. The UV/vis/nIR electronic absorption spectrum of this solution (Figure 1a) reveals the dominant 5f f 5f transition for NpO 2 + at 980 nm, the most commonly observed position for this peak in the presence of a range of ligands, 8,9 and a second major absorption peak at 1005 nm, which we attribute to the neptunyl PW 9 complex. From the extinction coefficient of the peak at 980 nm (398 M -1 cm -1 ), 8 we estimate that at least 90% of the NpO 2 + is complexed by the polyoxometalate anion.…”

“…10 Spectra were recorded from 300 to 1250 nm with high-intensity O f W charge-transfer bands observed below 350 nm but no evidence for either Np(IV) or (VI). 9 An excess of NaCl was then added to the solution, which was clarified by centrifuging, and cooled to 3 °C to yield lime green crystals (hexagonal plates) of Na 14 [Na 2 (NpO 2 ) 2 (A-PW 9 O 34 ) 2 ]. [15H 2 O] (1).…”

Highly efficient diglycolamide-functionalized dendrimers for the sequestration of tetravalent actinides: solvent extraction and theoretical studies

“…For the computation of K ex 0 , the value of K Nit was taken as 40.5 and 105 for Np(IV) and Pu(IV), respectively, at 3 M HNO 3 . [29][30][31] The value of 2.78 was used for the [NO 3 À ], calculated using a K a value of 23 for the dissociation of HNO 3 . 28 The values of the thermodynamic parameters DG, DH O and TDS were calculated as mentioned above.…”

Neptunium(V) Isothiocyanate Complexes with 4′-Aryl-Substituted 2,2′:6′,2″-Terpyridines and N,N-Dimethylacetamide as Molecular Ligands

“…Reported data on neptunium coordination chemistry are very limited because of the formidable challenges arising during such works . The coordination abilities of neptunium cations follow the order Np­(IV) > Np­(VI) > Np­(V) . The less coordinative Np­(V) is the most stable in aqueous solutions in the form of NpO 2 + and inextractable by conventional phosphine oxide ligands .…”

“…3 The coordination abilities of neptunium cations follow the order Np(IV) > Np(VI) > Np(V). 6 The less coordinative Np(V) is the most stable in aqueous solutions in the form of NpO 2 + and inextractable by conventional phosphine oxide ligands. 5 Hence, our work is devoted to the coordination chemistry of Np(V) with organic ligands aimed to extract actinides from nuclear waste.…”