Comparing the 2,2′‐Biphenylenedithiophosphinate Binding of Americium with Neodymium and Europium

Advancing our understanding of the minor actinides (Am, Cm) versus lanthanides is key for developing advanced nuclear‐fuel cycles. Herein, we describe the preparation of (NBu₄)Am[S₂P(^tBu₂C₁₂H₆)]₄ and two isomorphous lanthanide complexes, namely one with a similar ionic radius (i.e., Nd^III) and an isoelectronic one (Eu^III). The results include the first measurement of an Am?S bond length, with a mean value of 2.921(9) Å, by single‐crystal X‐ray diffraction. Comparison with the Eu^III and Nd^III complexes revealed subtle electronic differences between the complexes of Am^III and the lanthanides.     

Key Experimental Results of the PYROSMANI Project

The presented key results were obtained in the course of experiments carried out within the PYROSMANI (PYROchemical processes Study for Minor ActiNIdes recycling in molten salt chlorides and fluorides) Project supported by Rosatom. The individual and joint solubility of UF₄, PuF₃ and CeF₃ in ternary LiF–NaF–KF and LiF- ThF₄-UF₄ melts was measured by method of isothermal saturation for the temperature range 550-800°C. The solubility measurement technique based on isothermal saturation was verified in LiF–NaF–KF eutectics for praseodymium trifluoride by the reflectance spectroscopy. The process under investigation was the extraction of lanthanum, neodymium, europium and samarium trifluorides from 73LiF-27BeF₂ melt (mole %) into liquid bismuth at 600-610°C. There were defined temperature dependences of kinematic viscosity and melting temperatures for molten 46.5LiF–11.5NaF–42KF; 73LiF-27BeF₂; 85LiF-15AlF₃ and 43.5LiF–24.3NaF–32.2UF₄ salt mixtures from liquidus temperature to 840°C.     

Application of Multi-step Excitation Schemes for Detection of Actinides and Lanthanides in Solutions by Luminescence/Chemiluminescence Laser Spectroscopy

The use of laser radiation with tunable wavelength allows the selective excitation of actinide/lanthanide species with subsequent registration of luminescence/chemiluminescence for their detection. This work is devoted to applications of the time-resolved laser-induced luminescence spectroscopy and time-resolved laser-induced chemiluminescence spectroscopy for the detection of lanthanides and actinides. Results of the experiments on U, Eu, and Sm detection by TRLIF method in blood plasma and urine are presented. Data on luminol chemiluminescence in solutions containing Sm(III), U(IV), and Pu(IV) are analyzed. It is shown that appropriate selectivity of lanthanide/actinide detection can be reached when chemiluminescence is initiated by transitions within 4f- or 5f-electron shell of lanthanide/actinide ions corresponding to the visible spectral range. In this case chemiluminescence of chemiluminogen (luminol) arises when the ion of f element is excited by multi-quantum absorption of visible light. The multi-photon scheme of chemiluminescence excitation makes chemiluminescence not only a highly sensitive but also a highly selective tool for the detection of lanthanide/actinide species in solutions.     

Extraction and coordination behavior of diphenyl hydrogen phosphine oxide towards actinides

Extraction behavior of some selected actinides like U(VI), Th(IV), and Am(III) was investigated with three different H-phosphine oxides, viz. diphenyl hydrogen phosphine oxide (DPhPO), dihexyl hydrogen phosphine oxide (DHePO) and diphenyl phosphite (DPP). The H-phosphine oxides exhibited a dual nature towards the extraction of actinides where the ligand not only extracts the metals by cation exchange but also by coordination with the phosphoryl group at lower and higher acidic concentrations, respectively. Among all ligands employed, DPhPO showed highest extraction with actinides with a substituent dependent trend as follows: DPhPO > DHePO > DPP. This trend emphasizes the importance of substituents around the phosphine oxide towards their extraction of actinides. The coordination behavior of DPhPO was studied by investigating its corresponding complexes with Th(NO₃)₄ and UO₂(NO₃)₂. The metal complexes of these actinides were characterized using FT-IR, ¹H and ³¹P NMR spectroscopic techniques. Density Functional Theory (DFT) calculations were also performed to understand the electronic and geometric structure of the ligand and the corresponding metal complexes.     

Evaluation of bonding,electron affinity,and optical properties of M@C28 (M = Zr,Hf, Th,and U): Role of d‐ and f‐orbitals in endohedral fullerenes from relativistic DFT calculations

The experimentally characterized endohedral metallic fullerenes involving the small C₂₈ cage, has shown to be able to encapsulate zirconium, hafnium, and uranium atoms, among other elements. Here, we explore the formation and nature of concentric bonds from purely d‐ to f‐block elements, given by Zr, Hf, and uranium, along a borderline metal between such blocks, thorium. We explore the interplay of d‐ and f‐orbitals in the chemistry of the early actinides, where the features of a d‐ or f‐block metal can be mixed. Our results indicate that the bonding of Th@C₂₈ involves contributions from both d‐ and f‐type bonds, as characteristic of this early actinide element. Even uranium in U@C₂₈, also exhibits a contribution from d‐type bonds in addition to its relevant f‐block character. Electron affinity and optical properties were evaluated to gain more insights into the variation of these molecular properties in this small endohedral fullerene, along Zr, Hf, Th, and U. The current results, allows to unravel the role of (n − 1)d and (n − 2)f orbitals in confined elements ranging from d‐ to f‐blocks, which can be useful to gain a deeper understanding of the bonding situation in other endohedral species. © 2016 Wiley Periodicals, Inc.     

Experimental and Computational Studies on a Base-Free Terminal Uranium Phosphinidene Metallocene

The first stable base-free terminal uranium phosphinidene metallocene is presented; and its structure and reactivity have been studied in detail and compared to that of the corresponding thorium derivative. Salt metathesis reaction of the methyl iodide uranium metallocene Cp’’’₂U(I)Me ( 2 , Cp’’’=η⁵-1,2,4-(Me₃C)₃C₅H₂) with Mes*PHK (Mes*=2,4,6-(Me₃C)₃C₆H₂) in THF yields the base-free terminal uranium phosphinidene metallocene, Cp’’’₂U=PMes* ( 3 ). In addition, density functional theory (DFT) studies suggest substantial 5f orbital contributions to the bonding within the uranium phosphinidene [U]=PAr moiety, which results in a more covalent bonding between the [Cp’’’₂U]²⁺ and [Mes*P]²⁻ fragments than that for the related thorium derivative. This difference in bonding besides steric reasons causes different reactivity patterns for both molecules. Therefore, the uranium derivative 3 may act as a Cp’’’₂U(II) synthon releasing the phosphinidene moiety (Mes*P:) when treated with alkynes or a variety of hetero-unsaturated molecules such as imines, thiazoles, ketazines, bipy, organic azides, diazene derivatives, ketones, and carbodiimides.