The allylpalladium [Pd(η3-C3H5)(L)](BF4) (L = L1 (1), L2 (2), L3 (3), L4 (4)) complexes with
pyridylpyrazole ligands 2-(5-phenyl-1H-pyrazol-3-yl)pyridine (L1), 2-(1-ethyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L2), 2-(1-octyl-5-phenyl)-1H-pyrazol-3-yl)pyridine (L3), and 2-(5-phenyl-3-(pyridin-2-yl)pyrazol-1-yl)ethanol (L4) were synthesized from the appropriate pyridylpyrazole ligand and [Pd(η3-C3H5)Cl]2 in the presence of AgBF4. The cationic complex 1 was converted into the neutral complex 5
under basic conditions. These complexes were characterized, and the crystal and molecular structure of
[Pd(η3-C3H5)(L2)](BF4) (2) was resolved by X-ray diffraction. Also, we have studied the apparent allyl
rotation, observed as Hsyn−Hsyn and Hanti−Hanti interconversions. The influences of the solvent, the traces
of water, and the N1 substituent have also been studied.
Neptunium(V) and uranium(VI) are precipitated from an
aqueous potassium–sodium-containing
carbonate-rich solution, and the solid phases are investigated. U/Np
M4,5-edge high-energy resolution X-ray absorption near
edge structure (HR-XANES) spectroscopy and Np 3d4f resonant inelastic
X-ray scattering (3d4f RIXS) are applied in combination with thermodynamic
calculations, U/Np L3-edge XANES, and extended X-ray absorption
fine structure (EXAFS) studies to analyze the local atomic coordination
and oxidation states of uranium and neptunium. The XANES/HR-XANES
analyses are supported by ab initio quantum-chemical computations
with the finite difference method near-edge structure code (FDMNES).
The solid precipitates are also investigated with powder X-ray diffraction,
scanning electron microscopy–energy dispersive X-ray spectroscopy,
and Raman spectroscopy. The results strongly suggest that K[NpVO2CO3](cr), K3[NpVO2(CO3)2](cr), and K3Na[UVIO2(CO3)3](cr) are the predominant neptunium and uranium
solid phases formed. Despite the 100 times lower initial neptunium(V)
concentration at pH 10.5 and oxic conditions, neptunium(V)-rich phases
predominately precipitate. The prevailing formation of neptunium(V)
over uranium(VI) solids demonstrates the high structural stability
of neptunium(V) carbonates containing potassium. It is illustrated
that the Np M5-edge HR-XANES spectra are sensitive to changes
of the Np–O axial bond length for neptunyl(V/VI).
The long-term safety assessment for nuclear waste repositories requires a detailed understanding of actinide (geo)chemistry. Advanced analytical tools are required to gain insight into actinide speciation in a given system. The geochemical conditions in the vicinity of a nuclear repository control the redox state of radionuclides, which in turn has a strong impact on their mobility. Besides the long-lived radionuclides plutonium (Pu) and neptunium (Np), which are key elements in high level nuclear waste, iron (Fe) represents a main component in natural systems controlling redox-related geochemical processes. Measuring the oxidation state distribution for redox sensitive radionuclides and other metal ions is challenging at trace concentrations below the detection limit of most available spectroscopic methods (≥10(-6) M). Consequently, ultrasensitive new analytical techniques are required. Capillary electrophoresis (CE) is a suitable separation method for metal cations. CE hyphenated to inductively coupled plasma sector field mass spectrometry (CE-ICP-SF-MS) was used to measure the redox speciation of Pu (III, IV, V, VI), Np (IV, V, VI), and Fe (II, III) at concentrations lower than 10(-7) M. CE coupling and separation parameters such as sample gas pressure, make up flow rate, capillary position, auxiliary gas flow, as well as the electrolyte system were optimized to obtain the maximum sensitivity. We obtain detection limits of 10(-12) M for Np and Pu. The various oxidation state species of Pu and Np in different samples were separated by application of an acetate-based electrolyte system. The separation of Fe (II) and Fe (III) was investigated using different organic complexing ligands, EDTA, and o-phenanthroline. For the Fe redox system, a limit of detection of 10(-8) M was calculated. By applying this analytical system to sorption studies, we were able to underline previously published results for the sorption behavior of Np in highly diluted concentrations, and we monitored the time-dependent reduction of Pu(VI) by Fe(II). This study clearly shows that CE-ICP-SF-MS is a suitable separation method for the redox states of Pu, Np, and Fe.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.