Pivotal role of Tc NMR spectroscopy in solid-state and molecular chemistry.

The radioelement Technetium (element 43) pertains to various domains including the nuclear enterprise (i.e., spent nuclear fuel (SNF) reprocessing and nuclear waste remediation) and nuclear medicine (i.

Digging into the Intrinsic Negative Thermal Expansion of Uranium Tetrafluoride.

The intrinsic negative thermal expansion of UF below room temperature was examined. A redetermination of the structure of UF by single-crystal X-ray diffraction at 100, 200, and 300 K accompanied by an evaluation of the atomic displacement parameters (ADPs) of the F atoms was performed. The structure of UF was described as the stacking of two subnetworks, respectively, constituted by the U(1) and U(2) atoms.

Tailoring Triuranium Octoxide into Multidimensional Uranyl Fluoride Micromaterials.

Uranium microstructured materials with controlled size and shape are relevant to the nuclear industry and have found applications as targets for medical isotope production, fuels for nuclear reactors, standards for nuclear forensics, and energy sources for space exploration. Until now, most studies at the microscale have focused on uranium microspheres (oxides, nitrides, carbides, and fluorides), while micromaterials of uranium halides, carbides, and pnictides with other morphologies are largely unknown. A promising method to shape the morphology of uranium micromaterials is the replacement of O by F atoms in oxide materials using a solid-gas reaction.

Speciation of Technetium Dibutylphosphate in the Third Phase Formed in the TBP/HNO Solvent Extraction System.

The speciation of technetium in the nitric acid/dibutylphosphoric acid (HDBP)--dodecane system was studied by extended X-ray absorption fine structure (EXAFS) spectroscopy and theoretical methods. Tetravalent technetium, produced by the hydrazine reduction of TcO in 3 M HNO, was extracted by HDBP in -dodecane (30% by volume). During extraction, the splitting of the organic phase into a heavy phase and a light phase was observed.

Structural Investigation of Technetium Dibutylphosphate Species Using X-ray Absorption Fine Structure Spectroscopy.

The speciation of Tc after the extraction of Tc(IV) from HO and 1 M HNO by dibutylphosphoric acid (HDBP) in dodecane has been studied by X-ray absorption fine structure (XAFS) spectroscopy. Results show the formation of dimeric species with TcO and TcO units, and the formulas [TcO(DBP·HDBP)] (1) and [TcO(NO)(DBP)(DBP·HDBP)] (2) were, respectively, proposed for the species extracted from HO and 1 M HNO. The interatomic Tc-Tc distances found in the TcO and TcO units [2.

Synthesis and Morphological Control of UOF Particulates.

Uranium-based microspheres are of interest due to their potential applications as targets for medical isotopes production, as fuel for nuclear reactors, and as standardized materials for nuclear forensics. Here, for the first time, UOF microspheres (1-2 μm) have been prepared from the reaction between UO microspheres and AgHF in an autoclave. In this preparation, a new fluorination method has been applied, and HF-produced from the thermal decomposition of AgHF and NHHF-was used as the fluorinating agent.

Pressure-induced metallization and 3d-like behavior in TcS.

TcS undergoes a charge transfer insulator to metal transition above 28 GPa. Laser annealing reveals a kinetically hindered high pressure arsenopyrite phase that is recoverable to ambient. The new phase is similar to the Mn-dichalcogenides rather than the expected Re-dichalcogenides and involves the formation of S-S and Tc-Tc bonds.

Synthetic diversity in the preparation of metallic uranium.

Uranium metal is associated with several aspects of nuclear technology; it is used as fuel for research and power reactors, targets for medical isotope productions, explosive for nuclear weapons and precursors in synthetic chemistry. The study of uranium metal at the laboratory scale presents the opportunity to evaluate metallic nuclear fuels, develop new methods for metallic spent fuel reprocessing and advance the science relevant to nuclear forensics and medical isotope production. Since its first isolation in 1841, from the reaction of uranium chloride and potassium metal, uranium metal has been prepared by solid-state reactions and in solution by electrochemical, chemical and radiochemical methods.

Thermal Analysis of Benzotriazolium Perrhenate and Its Implication to Rhenium Metal.

The thermal analysis behavior of CHN[ReO] was studied by simultaneous thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) up to 700 °C under argon. Such analysis afforded rhenium metal, which was characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. XRD peak broadening due to crystallite size and lattice strain was analyzed by both Williamson-Hall (W-H) and Debye-Scherrer (D-S) methods.

Synthesis and chemical stability of technetium nitrides.

We demonstrate the synthesis and phase stability of TcN, TcN, and a substoichiometric TcN from 0 to 50 GPa and to 2500 K in a laser-heated diamond anvil cell. At least potential recoverability is demonstrated for each compound. TcN adopts a previously unpredicted structure identified via crystal structure prediction.

A 70-Year-Old Mystery in Technetium Chemistry Explained by the New Technetium Polyoxometalate [H O ] [Tc O ] ⋅ 4H O.

[H O ] [Tc O ] ⋅ 4H O [1] was prepared from an aqueous Tc O solution concentrated over anhydrous H SO . [Tc O ] is the first polyanionic species to be reported for Tc. The unit cell contains one centrosymmetric [Tc O ] polyanion as well as hydronium ions and water molecules.

Coexistence of metamagnetism and slow relaxation of magnetization in ammonium hexafluoridorhenate.

The (NH)[ReF] (1) salt was studied by X-ray diffraction, Raman spectroscopy, theoretical calculations, and magnetic measurements. 1 crystallizes in the trigonal space group 3̄1 (Re-F = 1.958(5) Å).

An Americium-Containing Metal-Organic Framework: A Platform for Studying Transplutonium Elements.

The synthesis, structure, and spectroscopic characterization of the first transplutonium metal-organic framework (MOF) is described. The preparation and structure of Am-GWMOF-6, [Am (C H O ) (H O) ][(C H N )], is analogous to that of the isostructural trivalent lanthanide-only containing material GWMOF-6. The presented MOF architecture is used as a platform to probe Am coordination chemistry and guest-enhanced luminescent emission, whereas the framework itself provides a means to monitor the effects of self-irradiation upon crystallinity over time.

An unexpected rhenium(IV)-rhenium(VII) salt: [Co(NH)][ReO][ReF]·6HO.

The title hydrated salt, tris-[hexa-amminecobalt(III)] tetraoxidorhenate(VII) tetra-kis-[hexa-fluorido-rhenate(IV)] hexa-hydrate, arose unexpectedly due to possible contamination of the KReF starting material with KReO. It consists of octa-hedral [Co(NH)] cation (Co1 site symmetry 1), tetra-hedral [ReO] anions (Re site symmetry 1) and octa-hedral [ReF] anions (Re site symmetries 1and ). The [ReF] octa-hedral anions (mean Re-F = 1.

Structures and Phase Transitions in Pertechnetates.

The temperature dependence of the structures of four pertechnetates (TcO = Ag, Tl, Rb, Cs) from 90 K to their melting points is described. Synchrotron X-ray diffraction measurements show that RbTcO undergoes a 4/ to 4/ transition near 530 K that is associated with a change in the orientation of the TcO tetrahedra about the scheelite axis. AgTcO also exhibits a tetragonal scheelite type structure, and this is retained between 90 and 750 K, above which it melted.

Ultrafast Laser Filament-induced Fluorescence Spectroscopy of Uranyl Fluoride.

Uranyl fluoride (UOF) is a compound which forms in the reaction between water and uranium hexafluoride, a uranium containing gas widely used for uranium enrichment. Uranyl fluoride exhibits negligible natural background in atmosphere; as a result, its observation implies the presence and active operation of nearby enrichment facilities and could be used as a tracer for treaty verification technologies. Additionally, detection of UOF has a potential application in guiding remediation efforts around enrichment facilities.

Syntheses, Raman spectroscopy and crystal structures of alkali hexa-fluorido-rhenates(IV) revisited.

The [ReF] ( = K, Rb and Cs) salts are isotypic and crystallize in the trigonal space group type [Formula: see text] 1, adopting the K[GeF] structure type. Common to all [ReF] structures are slightly distorted octa-hedral [ReF] anions with an average Re-F bond length of 1.951 (8) Å.

Zirconium tetrachloride revisited.

Zirconium tetrachloride, ZrCl, is a strategic material with wide-ranging applications. Until now, only one crystallographic study on ZrCl has been reported [Krebs (1970). Z.

Unraveling the mystery of "tech red" - a volatile technetium oxide.

We show that a TcO molecular species is the likely identity of an unknown volatile oxide which has remained uncharacterized for 50+ years. Exploration of this molecule's absorption spectra and intermolecular self-interactions provides a close match to experimental data and an explanation for volatility and resistance to crystallization.

Expanding the Chemistry of Rhenium Metal-Metal Bonded Fluoro Complexes: Facile Preparation and Characterization of Paddlewheel Complexes.

Quadruply bonded rhenium(III) dimers with the stoichiometry ReLF (1, L = hexahydro-2H-pyrimido[1,2a]pyrimidinate (hpp); 2, L = diphenyl formamidinate (dpf)) were prepared from the solid-state melt reactions (SSMRs) between (NH)[ReF]·2HO and HL. Those compounds were characterized in the solid state by single-crystal X-ray diffraction and in solution by UV-visible spectroscopy and cyclic voltammetry. The compound [Re(hpp)F]PF (3) was prepared from the one-electron oxidation of Re(hpp)F with [CpFe]PF.

Thermal Expansion Behavior in TcO. Toward Breaking the Tc-Tc Bond.

The structure of TcO between 25 and 1000 °C has been determined in situ using X-ray powder diffraction methods and is found to remain monoclinic in space group P2/c. Thermal expansion in TcO is highly anisotropic, with negative thermal expansion of the b axis observed above 700 °C. This is the result of an anomalous expansion along the a axis that is a consequence of weakening of the Tc-Tc bonds.

Molecular and Electronic Structures of MO (M = Mn, Tc, Re).

The molecular and electronic structures of the group 7 heptoxides were investigated by computational methods as both isolated molecules and in the solid-state. The metal-oxygen-metal bending angle of the single molecule increased with increasing atomic number, with ReO preferring a linear structure. Natural bond orbital and localized orbital bonding analyses indicate that there is a three-center covalent bond between the metal atoms and the bridging oxygen, and the increasing ionic character of the bonds favors larger bond angles.