Hydrothermal synthesis of (C6N2H14)2(UVI2UIVO4F12), a mixed-valent one-dimensional uranium oxyfluoride

BaWO2F4: a mixed anion X-ray scintillator with excellent photoluminescence quantum efficiency

A new self-activated X-ray scintillator, BaWO2F4, with an excellent photoluminescence quantum efficiency is reported. Hydrothermally grown single crystals, space group P2/n, exhibit a 3D framework structure containing isolated WO2F4 octahedra. BaWO2F4 exhibits green emission under UV light with a high quantum yield of 53% and scintillates when exposed to X-rays(Cu).

Flux crystal growth of uranium(v) containing oxyfluoride perovskites

Crystals of three new uranium(v) containing oxyfluorides were grown out of an alkali fluoride flux and adopt a perovskite-type structure and are examined by SXRD, PXRD, XANES, XPS, EDS, magnetic susceptibility measurements, DFT calculations, and UV-vis spectroscopy.

Anionic uranyl oxyfluorides as a bifunctional platform for highly selective ion-exchange and photocatalytic degradation of organic dyes

Anionic uranium oxyfluorides with tunable open-volumes were synthesized and they exhibit selective ion-exchange and photocatalytic properties toward methylene blue.

Insight into the Uranyl Oxyfluoride Topologies through the Synthesis, Crystal Structure, and Evidence of a New Oxyfluoride Layer in [(UO2)4F13][Sr3(H2O)8](NO3)·H2O

A new strontium uranyl oxyfluoride, [(UO₂)₄F₁₃][Sr₃(H₂O)₈](NO₃)·H₂O, was synthesized under hydrothermal conditions. The single-crystal X-ray structure was determined. This compound crystallizes in the triclinic space group P1̅ (No. 2), with unit cell parameters a = 10.7925(16) Å, b = 10.9183(16) Å, c = 13.231(2) Å, α = 92.570(8)°, β = 109.147(8)°, γ = 92.778(8)°, V = 1468.1(4) ų, and Z = 2. The structure is built from uranyl-containing [Formula: see text] chains of tetrameric units of corner-sharing UO₂F₅ pentagonal bipyramids. These chains are linked through trimeric strontium units to form strontium-uranyl oxyfluoride layers further assembled by nitrate groups. The interlayer space is occupied by free water molecules. This compound was characterized by spectroscopic methods, especially ¹⁹F NMR highlighting the many different fluoride sites. Structural relationships with other uranyl oxyfluorides were investigated through the different F/O ratios, the structural building unit, and the structural arrangement.

Nonlinear optical response mechanism of noncentrosymmetric lead borate Pb6[B4O7(OH)2]3with three crystallographically independent [B4O7(OH)2]4−chains

Pb₆[B₄O₇(OH)₂]₃features three unique [B₄O₇(OH)₂]⁴⁻chains while lead cations and π-conjugated BO₃groups make contribution to the nonlinear optical effect.

Hydrothermal syntheses and characterization of uranyl tungstates with electro-neutral structural units

Two uranyl tungstates, (UO2)(W2O7)(H2O)3 (1) and (UO2)3(W2O8)F2(H2O)3 (2), were synthesized under hydrothermal conditions at 220°C and were structurally, chemically, and spectroscopically characterized. 1 Crystallizes in space group Pbcm, a = 6.673(5) Å, b = 12.601(11) Å, c = 11.552 Å; 2 is in C2/m, a = 13.648(1) Å, b = 16.852(1) Å, c = 9.832(1) Å, β = 125.980(1)°. In 1 the U(VI) cations are present as (UO2)2+ uranyl ions that are coordinated by five oxygen atoms to give pentagonal bipyramids. These share two edges with two tungstate octahedra and single vertices with four additional octahedra, resulting in a sheet with the iriginite-type anion topology. Only water molecules are located in the interlayer. The structural units of 2 consist of (UO2)2+ uranyl oxy-fluoride pentagonal bipyramids present as either [UO2F2O3]–6 or [UO2FO4]–5 , and strongly distorted tungstate octahedra. The linkage of uranyl pentagonal bipyramids and tungstate octahedra gives a unique sheet anion topology consisting of pentagons, squares and triangles. In 2, the uranyl tungstates sheets are connected into a novel electro-neutral three-dimensional framework through dimers of uranyl pentagonal bipyramids. These dimers connecting the sheets share an edge defined by F anions. 2 is the first example of a uranyl tungstate oxy-fluoride, and 1 and 2 are rare examples of uranyl compounds containing electro-neutral structural units.

Novel uranyl(vi) complexes incorporating propylene-bridged salen-type N2O2-ligands: a structural and computational approach

Synthesis of uranyl complex, [UO₂L(CH₃OH)] showing distorted pentagonal bipyramidal geometry and derived from a tetradentate dianionic ligand is reported. The computational study of the reported complex shows that its LUMO is featured with uranium f orbital character.

Exploring actinide materials through synchrotron radiation techniques

Synchrotron radiation (SR) based techniques have been utilized with increasing frequency in the past decade to explore the brilliant and challenging sciences of actinide-based materials. This trend is partially driven by the basic needs for multi-scale actinide speciation and bonding information and also the realistic needs for nuclear energy research. In this review, recent research progresses on actinide related materials by means of various SR techniques were selectively highlighted and summarized, with the emphasis on X-ray absorption spectroscopy, X-ray diffraction and scattering spectroscopy, which are powerful tools to characterize actinide materials. In addition, advanced SR techniques for exploring future advanced nuclear fuel cycles dealing with actinides are illustrated as well.

Actinides and Life's Origins

There are growing indications that life began in a radioactive beach environment. A geologic framework for the origin or support of life in a Hadean heavy mineral placer beach has been developed, based on the unique chemical properties of the lower-electronic actinides, which act as nuclear fissile and fertile fuels, radiolytic energy sources, oligomer catalysts, and coordinating ions (along with mineralogically associated lanthanides) for prototypical prebiotic homonuclear and dinuclear metalloenzymes. A four-factor nuclear reactor model was constructed to estimate how much uranium would have been required to initiate a sustainable fission reaction within a placer beach sand 4.3 billion years ago. It was calculated that about 1-8 weight percent of the sand would have to have been uraninite, depending on the weight percent, uranium enrichment, and quantity of neutron poisons present within the remaining placer minerals. Radiolysis experiments were conducted with various solvents with the use of uraniumand thorium-rich minerals (metatorbernite and monazite, respectively) as proxies for radioactive beach sand in contact with different carbon, hydrogen, oxygen, and nitrogen reactants. Radiation bombardment ranged in duration of exposure from 3 weeks to 6 months. Low levels of acetonitrile (estimated to be on the order of parts per billion in concentration) were conclusively identified in 2 setups and tentatively indicated in a 3(rd) by gas chromatography/mass spectrometry. These low levels have been interpreted within the context of a Hadean placer beach prebiotic framework to demonstrate the promise of investigating natural nuclear reactors as power production sites that might have assisted the origins of life on young rocky planets with a sufficiently differentiated crust/mantle structure. Future investigations are recommended to better quantify the complex relationships between energy release, radioactive grain size, fissionability, reactant phase, phosphorus release, and possible abiotic production of sugars, amino acids, activated phosphorus, prototypical organometallic enzymes, and oligomer catalysts at a single putative beach site.

Synthesis, Structure, and Upconversion Studies on Organically Templated Uranium Phosphites

Three new amine templated uranium phosphites, [C2N2H10][U2IVF6(HPO3)2], 1, [C4N2H12][U2IVF6(HPO3)2], 2, and [C4N2H12][(UVIO2)2F2(HPO3)2], 3, have been synthesized by hydrothermal methods. All of the compounds are built up from a connectivity between U(O/F)x (x = 7, 8) and HPO3 polyhedral units. The observation of a well-established secondary building unit, SBU-4, in 1 and 2 is noteworthy. In 1, the SBU-4 units are connected to form U-F-U chains, which are linked by U-O-P chains, forming the layered structure. In 2, the SBU-4 units are edge-shared and also interconnected forming the 3D structure. In 3, the connectivity between the building units forms a layer, the topology of which is similar to the mineral, johannite. To the best of our knowledge, this is the first observation of a well-known secondary building unit (SBU-4) in actinide framework compounds. Optical studies on 1 and 2, containing U(4+) species, indicate an intense blue emission through an upconversion process, and the magnetic susceptibility studies show antiferromagnetic behavior.

Uranyl Coordination in Ionic Liquids: The Competition between Ionic Liquid Anions, Uranyl Counterions, and Cl-Anions Investigated by Extended X-ray Absorption Fine Structure and UV−Visible Spectroscopies and Molecular Dynamics Simulations

The first coordination sphere of the uranyl cation in room-temperature ionic liquids (ILs) results from the competition between its initially bound counterions, the IL anions, and other anions (e.g., present as impurities or added to the solution). We present a joined spectroscopic (UV-visible and extended X-ray absorption fine structure)-simulation study of the coordination of uranyl initially introduced either as UO2X2 salts (X-=nitrate NO3-, triflate TfO-, perchlorate ClO4-) or as UO2(SO4) in a series of imidazolium-based ILs (C4mimA, A-=PF6-, Tf2N-, BF4- and C4mim=1-methyl-3-butyl-imidazolium) as well as in the Me3NBuTf2N IL. The solubility and dissociation of the uranyl salts are found to depend on the nature of X- and A-. The addition of Cl- anions promotes the solubilization of the nitrate and triflate salts in the C4mimPF6 and the C4mimBF4 ILs via the formation of chloro complexes, also formed with other salts. The first coordination sphere of uranyl is further investigated by molecular dynamics (MD) simulations on associated versus dissociated forms of UO2X2 salts in C4mimA ILs as a function of A- and X- anions. Furthermore, the comparison of UO2Cl(4)2-, 2 X- complexes with dissociated X- anions, to the UO2X2, 4 Cl- complexes with dissociated chlorides, shows that the former is more stable. The case of fluoro complexes is also considered, as a possible result of fluorinated IL anion's degradation, showing that UO2F42- should be most stable in solution. In all cases, uranyl is found to be solvated as formally anionic UO2XnAmClp2-n-m-p complexes, embedded in a cage of stabilizing IL imidazolium or ammonium cations.

[(CH3)2NH(CH2)2NH(CH3)2][(UO2)2F2(HPO4)2]: a new organically templated layered uranium phosphate fluoride - synthesis, structure, characterization, and ion-exchange reactions

A new organically templated layered uranium phosphate fluoride, [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)][(UO(2))(2)F(2)(HPO(4))(2)] has been synthesized by hydrothermal reaction of UO(3), H(3)PO(4), HF, and (CH(3))(2)NCH(2)CH(2)N(CH(3))(2) at 140 degrees C. [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)][(UO(2))(2)F(2)(HPO(4))(2)] has a layered crystal structure consisting of seven-coordinated UO(5)F(2) pentagonal bipyramids and four-coordinated HPO(4) tetrahedra. Each anionic layer containing three-, four-, and six-membered rings is separated by [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)](2+) cations. The [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)](2+) cations may be readily exchanged with the M(2+) ions (M = Ba, Sr and Ca) in water to give high crystalline AE(UO(2))(2)(PO(4))(2).6H(2)O (AE = Ca, Sr, Ba).

Synthesis, crystal structure and optical properties of [Ag(UO2)3(OAc)9][Zn(H2O)4(CH3CH2OH)2]: A novel compound containing closed-shell 3d10, 4d10 and 5d10 metal ions

[Ag(UO2)3 (OAc)9][Zn(H2O)4(CH3CH2OH)2] (, OAc = CH3COO-) crystallized from an ethanol solution and its structure was determined by IR spectroscopy, elemental analysis, 1H NMR, 13C NMR and X-ray crystallography; it is composed of [Zn(H2O)4(CH3CH2OH)2]2+ cations and [Ag(UO2)3(OAc)9]2- anions in which triuranyl [(UO2)(OAc)3]3 clusters are linked by the Ag ion.

Organically templated uranium(iv) fluorooxalates with layer structures: (H4TREN)[U2F6(C2O4)3]·4H2O (TREN = tris(2-aminoethyl)amine) and (H4APPIP)[U2F6(C2O4)3]·4H2O (APPIP = 1,4-bis(3-amino-propyl)piperazine)

Two organically-templated layered uranium(IV) fluorooxalates, (H(4)TREN)[U(2)F(6)(C(2)O(4))(3)].4H(2)O (1) (TREN = tris(2-aminoethyl)amine) and (H(4)APPIP)[U(2)F(6)(C(2)O(4))(3)].4H(2)O (2) (APPIP = 1,4-bis(3-aminopropyl)piperazine), have been synthesized by hydrothermal methods and structurally characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility. Both structures consist of anionic [U(2)F(6)(C(2)O(4))(3)](4-) layers separated by organic ammonium cations and lattice water molecules. The UF(3)O(6) polyhedra are connected by oxalate ligands in different ways within the layers. They are the first examples of organically-templated uranium fluorooxalates. Crystal data for compound 1 follow: monoclinic, P2(1)/c (No. 14), a = 19.1563(5) A, b = 8.9531(2) A, c = 16.6221(4) A, beta = 114.633(1) degrees, and Z = 4. Crystal data for compound are the same as those for 1 except a = 10.3309(8) A, b = 15.564(1) A, c = 17.537(1) A, and beta = 95.430(4) degrees.

UF3(H2O)(C2O4)0.5: A Fluorooxalate of Tetravalent Uranium with a Three-Dimensional Framework Structure

A new uranium(IV) fluorooxalate, UF3(H2O)(C2O4)0.5, has been synthesized by a hydrothermal method and structurally characterized by single-crystal X-ray diffraction, infrared spectroscopy, and thermogravimetric analysis. The structure consists of two-dimensional layers of corner- and edge-sharing tricapped trigonal prisms with the composition UF(4/2)F(2/2)O3 linked by bisbidentate oxalate ligands to form a three-dimensional framework. Magnetic susceptibilities were measured to confirm the tetravalent state of uranium. Crystal data: monoclinic, space group C2/c, a = 17.246(3) Angstroms, b = 6.088(1) Angstroms, c = 8.589(2) Angstroms, beta = 95.43(3) degrees, and Z = 8.

Hydrothermal Synthesis and Characterization of [(UO2)2F8(H2O)2Zn2(4,4‘-bpy)2]·(4,4‘-bpy), a Mixed-Metal Uranyl Aquofluoride with a Pillared Layer Structure

A mixed-metal uranyl aquofluoride, [(UO2)2F8(H2O)2Zn2(4,4'-bpy)2].(4,4'-bpy), has been synthesized under hydrothermal conditions and has been structurally characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, emission spectroscopy, and solid-state NMR spectroscopy. It is one of the few uranium fluoride-organic framework solids in which an organic molecule is directly incorporated into the extended structure of the metal fluoride and is the first example of mixed-metal uranium oxyfluoride incorporating an organic ligand. The structure consists of neutral layers of edge- and corner-sharing uranium-centered pentagonal bipyramids and zinc-centered octahedra, which are linked through 4,4'-bpy ligands into a 3-D framework. The 1H MAS NMR spectrum is in support of the conclusion that the occluded 4,4'-bpy molecules in the structural channels are not protonated. Crystal data: monoclinic, space group P2(1)/c, a = 9.4630(5) A, b = 22.384(1) A, c = 16.7534(8) A, beta = 91.899(2) degrees , V = 3546.7(4) A(3) and Z = 4.

Syntheses, structures and fluorescent properties of two novel coordination polymers in the U–Cu–H3pdc system

Two novel coordination polymers, UO2(C5H2N2O4)(H2O) (1) and (UO2)Cu(C5H2N2O4)2(H2O)2 (2), have been prepared by the hydrothermal reaction of uranyl nitrate hexahydrate [(UO2(NO3)2.6H2O], 3,5-pyrazoledicarboxylic acid (H3pdc) and copper(II) nitrate hemipentahydrate (Cu(NO3)2.2.5H2O) and characterized by single-crystal X-ray diffraction, thermogravimetric analyses (TGA) and fluorescence spectroscopy. Compound 1 (monoclinic, P2(1)/c, a=6.9556(6)A, b=11.302(1)A, c= 10.5288(9)A, beta=90.057(2) degrees and Z=4) consists of a two-dimensional sheet containing uranyl hexagonal bipyramids. Compound 2 (triclinic, P-1, a=5.1014(7)A, b=7.6067(11)A, c=10.2910(15)A, alpha=72.380(3) degrees, beta=86.796(3) degrees, gamma=84.447(3) degrees and Z=1) consists of two-dimensional sheets. Both structures contain the linear UO2(2+) moiety and have extended networks built up from the H3pdc ligand. Compound 1 exhibits the characteristic UO(2)2+ emission spectra when it is excited at the ligand or uranium excitation wavelength. With the addition of the copper metal center in compound 2, the uranium emission is absent regardless of the excitation wavelength.

[N(CH2CH2NH3)3][U3O2F13]·2H2O: A Novel Organically Templated Mixed-Valent Uranium Oxyfluoride with a Hybrid Network Structure

The synthesis and characterization of a novel mixed-valent uranium oxyfluoride is described; the inorganic network consists of 2-D [U(2)F(10)](2)(-) sheets constructed from corner- and edge-sharing U(IV)F(9) tricapped trigonal prisms and 1-D [UO(2)F(3)](-) chains constructed from edge-sharing U(VI)O(2)F(5) pentagonal bipyramids with the organic cations and water molecules between the sheets. This is the first example with a hybrid network structure in the system of uranium fluoride or oxyfluoride. The variable-temperature magnetic susceptibility confirms the oxidation state of the uranium ions. Crystal data follow: C(6)H(25)N(4)O(4)F(13)U(3), monoclinic, space group P2(1) (No. 4); a = 8.6876(4) A, b = 7.3158(4) A, c = 16.3376(8) A, beta = 93.7285(9) degrees , V = 1036.2(2) A(3), and Z = 2.

[(Th2F5)(NC7H5O4)2(H2O)][NO3]: An Actinide−Organic Open Framework

We believe [(Th2F5)(NC7H5O4)2(H2O)][NO3] is the first three-dimensionally connected, actinide-organic framework solid. The structure is composed of thorium oxyfluoride chains, each of which connected to pyridinedicarboxylate groups to give a 3D cross-linked network with cavities containing nitrate anions.

[NC4H12]2[(UO2)6(H2O)2(SO4)7]: the first organically templated actinide sulfate with a three-dimensional framework structure

[NC4H12][(UO2)6(H2O)2(SO4)7] is the first organically templated actinide sulfate with a three-dimensional framework structure; it has channels of dimensions 8.5 A x 8.5 A, running along the [001] direction, containing tetramethylammonium cations.

The first organically templated thorium compounds, [C4N2H12]0.5[ThF5] and [C5N2H14][ThF6].0.5H2O

Organically templated thorium compounds were synthesized for the first time under hydrothermal conditions; the piperazine containing compound consists of 2-D layers, while the 2-methylpiperazine phase contains unprecedented 1-D chains of face-sharing ThF9 polyhedra.

A new oxoanion: [IO]3- containing I(V) with a stereochemically active lone-pair in the silver uranyl iodate tetraoxoiodate(V), Ag4(UO2)4(IO3)2(IO4)2O2

The hydrothermal reaction of elemental Ag, or water-soluble silver sources, with UO3 and I2O5 at 200 degrees C for 5 days yields Ag4(UO2)4(IO3)2(IO4)2O2 in the form of orange fibrous needles. Single-crystal X-ray diffraction studies on this compound reveal a highly complex network structure consisting of three interconnected low-dimensional substructures. The first of these substructures are ribbons of UO8 hexagonal bipyramids that edge-share to form one-dimensional chains. These units further edge-share with pentagonal bipyramidal UO7 units to create ribbons. The edges of the ribbons are partially terminated by tetraoxoiodate(V), [IO4]3-, anions. The uranium oxide ribbons are joined by bridging iodate ligands to yield two-dimensional undulating sheets. These sheets help to form, and are linked together by, one-dimensional chains of edge-sharing AgO7 capped octahedral units and ribbons formed by corner-sharing capped trigonal planar AgO4 polyhedra, AgO6 capped square pyramids, and AgO6 octahedra. The [IO4]3- anions in Ag4(UO2)4(IO3)2)(IO4)2O2 are tetraoxoiodate(V), not metaperiodate, and contain I(V) with a stereochemically active lone-pair. Bond valence sum calculations are consistent with this formulation. Differential scanning calorimetry measurements show distinctly different thermal behavior of Ag4(UO2)4(IO3)2(IO4)2O2 versus other uranyl iodate compounds with endotherms at 479 and 494 degrees C. Density functional theory (DFT) calculations demonstrate that the approximate C2v geometry of the [IO4]3- anion can be attributed to a second-order Jahn-Teller distortion. DFT optimized geometry for the [IO4]3- anion is in good agreement with those measured from single-crystal X-ray diffraction studies on Ag4(UO2)4(IO3)2(IO4)2O2.

Excision of uranium oxide chains and ribbons in the novel one-dimensional uranyl iodates K(2)[(UO(2))3(IO(3))(4)O(2)] and Ba[(UO(2)2(IO(3))(2)O(2)](H(2)O)

The alkali metal and alkaline-earth metal uranyl iodates K(2)[(UO(2))(3)(IO(3))(4)O(2)] and Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O) have been prepared from the hydrothermal reactions of KCl or BaCl(2) with UO(3) and I(2)O(5) at 425 and 180 degrees C, respectively. While K(2)[(UO(2))(3)(IO(3))(4)O(2)] can be synthesized under both mild and supercritical conditions, the yield increases from <5% to 73% as the temperature is raised from 180 to 425 degrees C. Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O), however, has only been isolated from reactions performed in the mild temperature regime. Thermal measurements (DSC) indicate that K(2)[(UO(2))(3)(IO(3))(4)O(2)] is more stable than Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O) and that both compounds decompose through thermal disproportionation at 579 and 575 degrees C, respectively. The difference in the thermal behavior of these compounds provides a basis for the divergence of their preparation temperatures. The structure of K(2)[(UO(2))(3)(IO(3))(4)O(2)] is composed of [(UO(2))(3)(IO(3))(4)O(2)](2)(-) chains built from the edge-sharing UO(7) pentagonal bipyramids and UO(6) octahedra. Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O) consists of one-dimensional [(UO(2))(2)(IO(3))(2)O(2)](2)(-) ribbons formed from the edge sharing of distorted UO(7) pentagonal bipyramids. In both compounds the iodate groups occur in both bridging and monodentate binding modes and further serve to terminate the edges of the uranium oxide chains. The K(+) or Ba(2+) cations separate the chains or ribbons in these compounds forming bonds with terminal oxygen atoms from the iodate ligands. Crystallographic data: K(2)[(UO(2))(3)(IO(3))(4)O(2)], triclinic, space group P_1, a = 7.0372(5) A, b = 7.7727(5) A, c = 8.9851(6) A, alpha = 93.386(1) degrees, beta = 105.668(1) degrees, gamma = 91.339(1) degrees, Z = 1; Ba[(UO(2))(2)(IO(3))(2)O(2)](H(2)O), monoclinic, space group P2(1)/c, a = 8.062(4) A, b = 6.940(3) A, c = 21.67(1), beta= 98.05(1) degrees, Z = 4.