Deviation between the Structural Chemistry of Barium and Radium Halides: Synthesis and Characterization of RaX·HO and RaX·2HO (X = Cl and Br).

To develop the structural chemistry of radium, the halide compounds RaX·HO and RaX·2HO (X = Cl and Br) have been synthesized and characterized and serve as benchmarks for comparisons with more complex compounds in the future. In contrast with historic reports on the structural chemistry of radium, the Ra chlorides differ from their Ba analogues. For MCl·HO (M = Ba, Ra), the variance between the metal coordination environments manifests as a small, local distortion that becomes more apparent in the extended structure.

Comparison of Americium(III) and Neodymium(III) Monothiophosphate Complexes.

Mixed-donor ligands, such as those containing a combination of O/N or O/S, have been studied extensively for the selective extraction of trivalent actinides, especially Am and Cm, from lanthanides during the recycling of used nuclear fuel. Oxygen/sulfur donor ligand combinations also result from the hydrolytic and/or radiolytic degradation of dithiophosphates, such as the Cyanex class of extractants, which are initially converted to monothiophosphates. To understand potential differences between the binding of such degraded ligands to Nd and Am, the monothiophosphate complexes [M(OPS(OEt))(HO)] (M = Nd, Am) were prepared and characterized by single-crystal X-ray diffraction and optical spectroscopy and studied as a function of pressure up to ca.

Synthesis of Non-Aqueous Neptunium(III) Halide Solvates from NpO.

Two Np(III) halides, NpI (THF) and NpBr (THF) , have been prepared and isolated in high yields as described in this work. Starting with neptunia (NpO ), NpCl (DME) was first generated in an updated, higher yielding synthesis than what was previously reported by using HCl/HF. This material was then reduced with KC , followed by subsequent ligand exchange, to generate NpBr (THF) and NpI -(THF) .

Using Redox-Active Ligands to Generate Actinide Ligand Radical Species.

Using a redox-active dioxophenoxazine ligand, DOPO (DOPO = 2,4,6,8-tetra--butyl-1-oxo-1-phenoxazine-9-olate), a family of actinide (U, Th, Np, and Pu) and Hf tris(ligand) coordination compounds was synthesized. The full characterization of these species using H NMR spectroscopy, electronic absorption spectroscopy, SQUID magnetometry, and X-ray crystallography showed that these compounds are analogous and exist in the form M(DOPO)(DOPO), where two ligands are of the oxidized quinone form (DOPO) and the third is of the reduced semiquinone (DOPO) form. The electronic structures of these complexes were further investigated using CASSCF calculations, which revealed electronic structures consistent with metals in the +4 formal oxidation state and one unpaired electron localized on one ligand in each complex.

Pronounced Pressure Dependence of Electronic Transitions for Americium Compared to Isomorphous Neodymium and Samarium Mellitates.

The mellitate ion is relevant in spent nuclear fuel processing and is utilized as a surrogate for studying the interactions of f elements with humic acids. A wealth of different coordination modes gives the potential for diverse structural chemistry across the actinide series. In this study, an americium mellitate, Am[(C(COO)](HO)·2HO (), has been synthesized and characterized using structural analysis and spectroscopy at ambient and elevated pressures.

Compression of curium pyrrolidine-dithiocarbamate enhances covalency.

Curium is unique in the actinide series because its half-filled 5f  shell has lower energy than other 5f  configurations, rendering it both redox-inactive and resistant to forming chemical bonds that engage the 5f shell. This is even more pronounced in gadolinium, curium's lanthanide analogue, owing to the contraction of the 4f orbitals with respect to the 5f orbitals. However, at high pressures metallic curium undergoes a transition from localized to itinerant 5f electrons.

Pressure-Induced Spectroscopic Changes in a Californium 1D Material Are Twice as Large as Found in the Holmium Analog.

In this study, the synthesis, characterization, and pressure response of a 1D californium mellitate (mellitate = 1,2,3,4,5,6-benzenehexacarboxylate) coordination polymer, Cf(mell)(HO)·4HO (), are reported. The Cf-O lengths within the crystal structure are compared to its gadolinium () and holmium () analogs as well. These data show that the average Cf-O bond distance is slightly longer than the average Gd-O bond, consistent with trends in effective ionic radii.

Structural and Spectroscopic Investigation of Two Plutonium Mellitates.

The aqueous reaction of mellitic acid (Hmell) with PuBr·HO forms two plutonium mellitates, Pu(mell)(HO)·HO () and Pu(mell)(HO)·2HO (). These compounds are compared to the isomorphous lanthanide mellitates with similar ionic radii via bond length analysis. Both plutonium compounds form three-dimensional metal-organic frameworks, with having two unique metal centers and having one.