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The reaction of sodium N-morpholine acetate with selenic and sulfuric acid and uranyl nitrate results in the formation of two novel open-framework compounds, |Na(Hmfa)|[(UO2)2(SeO4)3(H2O)](H2O)2 (NaUSe) and [Na2(SO3OH)(Hmfa)]|(UO2)(SO4)2| (NaUS), respectively. Despite identical synthetic procedures, sulfate structure dramatically differs from selenate compound. Their common feature is an open-framework featuring two-dimensional system of channels occupied by protonated morpholino-N-acetic acid species. Coordination of Na atoms is different. In NaUSe, [(UO2)2 (SeO4)3(H2O)]2− layers are pillared by {Na2O8(H2O)2(Hmfa)2} complexes to form a microporous framework. In NaUS, UO7 and SO4 polyhedra of [(UO2)(SO4)2]2− chains share common oxygen atoms with Na-centered tetrameric complexes providing a three-dimensional integrity of the structure. Both of the compounds are characterized by IR spectroscopy. [ABSTRACT FROM AUTHOR]

Molal activity coefficients of uranyl nitrate and nitric acid in mixed solutions were calculated on the basis of Mikulin’s equations. Analytical equations for calculating these quantities at different concentrations were obtained. These equations are compatible with published activity coefficients for binary solutions, which allows their use for calculating the equilibria in uranium extraction from nitric acid solutions. [ABSTRACT FROM AUTHOR]

The structure and spectroscopic properties of two mixed-ligand uranyl complexes, [(CH3)4N]2· [(UO2)2(NO3)4(OH)2] and [(UO2)2(NO3)4(H2O)2]·2Im (Im = imidazole), were studied by single crystal X-ray diffraction and by vibrational and photoluminescence spectroscopy. The previously made assumption that the latter compound contains electrically neutral complexes [(UO2)2(NO3)4(H2O)2] was found to be erroneous; actually both compounds contain dimeric anions [(UO2)2(NO3)4(OH)2]2-. [ABSTRACT FROM AUTHOR]

Heterogeneous equilibria in the system Ca(HSiUO6)2 · 5H2O(c)-aqueous solution were studied over broad ranges of pH, ionic strength, and ionic composition of the solution, and the pH range of stability of Ca uranyl silicate is determined. Hydrolysis products of Ca uranyl silicate are identified, and their solubility is determined. The equilibrium constant of the dissolution reaction and the standard Gibbs function of formation of Ca(HSiUO6)2 · 5H2O are calculated from experimental data, and solubility curves of uranophane and equilibrium speciation diagrams for U(VI), Si(IV), and Ca(II) in coexisting aqueous solutions and solid phases are calculated. [ABSTRACT FROM AUTHOR]

A uranyl phosphonate framework, (UO2)2(1,3-pbp)(H2O)2·2H2O (UPF-1) (1,3-pbp = 1,3-phenylenebis(phosphonic acid)), experiences a thermally induced order–disorder transition, leading to a negative linear correlation between the photoluminescence intensity and temperature, and may find application as a luminescent thermometer. [ABSTRACT FROM AUTHOR]

A novel highly stable 3D luminescent uranyl coordination polymer, namely {[UO 2 (L)]·DMA} n ( 1 ), was assembled with uranyl salt and a glycine-derivative ligand [6-(carboxymethyl-amino)-4-oxo-4,5-dihydro-[1,3,5]triazin-2-ylamino]-acetic acid (H 2 L) under solvothermal reaction. Besides, It was found that complex 1 possesses excellent luminescent properties, particularly the efficient selectivity and sensitivity in the recognition of Ru 3+ , biomacromolecule bovine serum albumin (BSA), biological small molecules dopamine (DA), ascorbic acid (AA) and uric acid (UA) in the water solution based on a “turn-off” mechanism. Accordingly, the luminescent explorations also demonstrated that complex 1 could be acted as an efficient luminescent probe with high quenching efficiency and low detection limit for selectively detecting Ru 3+ and biomolecules (DA, AA, UA and BSA). It was noted that the framework structure of complex 1 still remains highly stable after quenching, which was verified by powder X-ray diffraction (PXRD). [ABSTRACT FROM AUTHOR]

The reduction of UVI uranyl halides or amides with simple LnII or UIII salts forms highly symmetric, linear, oxo-bridged trinuclear UV/LnIII/UV, LnIII/UIV/LnIII, and UIV/UIV/UIV complexes or linear LnIII/UV polymers depending on the stoichiometry and solvent. The reactions can be tuned to give the products of one- or two-electron uranyl reduction. The reactivity and magnetism of these compounds are discussed in the context of using a series of strongly oxo-coupled homo- and heterometallic poly(f-block) chains to better understand fundamental electronic structure in the f-block. [ABSTRACT FROM AUTHOR]

The reaction of uranyl nitrate with cucurbit[6]uril (CB6) and carboxylic or sulfonic ligands under hydrothermal conditions and in the presence of additional metal cations (KI or CeIII) or cosolvents provided four complexes, which were crystallographically characterized. The compound [(UO2)2 K2(CB6)(adc)2(NO3)2(H2O)2]·5H2O (1), where H2adc is 1,3-adamantanedicarboxylic acid, crystallizes in the form of a central K2(CB6)2+ column surrounded by two one-dimensional (1D) polymeric UO2(adc)(NO3)- chains attached to the column by nitrate bridges, with a perfect match of the repeat lengths in the two subunits. The longer 1,3-adamantanediacetic acid (H2adac) gives the complex [(UO2)2(adac)2(HCOOH)2]·CB6·6H2O (2), in which the 1D uranyl-containing polymer and columns of CB6 molecules form a layered arrangement held by weak CH·O hydrogen bonds. The complex formed with the dipotassium salt of methanedisulfonic acid (K2mds), [(UO2)2K2(CB6)(mds)2- (OH)2(H2O)8]·4H2O (3), is a 1D polymer, in which K2(CB6)2+ units are connected to one another by doubly hydroxide-bridged uranyl dimers in which the disulfonates are terminal, chelating ligands; connection between the two subunits is solely through potassium oxo-bonding to uranyl. The complex [(UO2)2Ce2- (CB6)(C2O4)3(NO3)4(H2O)6]·2H2O (4) is a 1D polymer containing bridging oxalate ligands formed in situ, in which CB6 is coordinated to the lanthanide cations only; one nitrate ligand and one water ligand, hydrogen-bonded to each other, are included in the CB6 cavity, with the possible occurrence of interactions between nitrate oxygen atoms and ureido carbon atoms. [ABSTRACT FROM AUTHOR]

Alkaline earth metals and their oxides have an important role while deciding the postirradiation processing of irradiated fuels from the reactors. The reaction between uranyl oxalate and barium oxalate has been studied using thermogravimetric analysis. Oxalates of uranium and barium were prepared, and their thermal decomposition in argon environment has been studied. It has been observed that uranyl oxalate decomposes into mixture of UO and UO with the evolution of carbon monoxide, oxygen and carbon dioxide in the temperature range of 573-673 K, but beyond this temperature UO and UO appeared as intermediate and the final product has been found to be UO. In case of solid-state reaction of barium oxalates, it has been observed that the reaction pathway of its decomposition is altered in the presence of uranium oxide. Barium oxalate first decomposes to barium carbonate followed by the reaction with uranium oxide at a relatively high temperature during the next step in TG. XRD characterization of the intermediates and end products indicated that BaUO is formed which gets partially reduced to BaUO at elevated temperature. [ABSTRACT FROM AUTHOR]

Twelve new complexes were obtained from reaction of uranyl ions with the aliphatic dicarboxylic acids HOOC-(CH2)n−2-COOH (H2Cn; n = 7-10 and 12) under solvo-hydrothermal conditions, in the presence of 3d-block metal ions (Mn2+, Fe3+, Co2+, Ni2+, and Cu2+) and 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen). In contrast to previously reported triple-stranded helicates obtained with C92- and C122-, all these complexes crystallize as polymeric one-dimensional (1D) or two-dimensional (2D) species. [Fe(bipy)3][(UO2)2(C7)3]•3H2O (1), [Cu(phen)2]2[(UO2)3(C7)4(H2O)2]•2H2O (2), and [Cu(bipy)2]2[(UO2)2(C9)3] (6), in which the 3d cation was reduced in situ, are 1D ladderlike polymers displaying tetra- or hexanuclear rings, of sufficient width to encompass two counterions in 2 and 6. The three complexes [Co(phen)3][(UO2)3(C8)3(O)]•H2O (3), [Ni(phen)3][(UO2)3(C8)3(O)]•H2O (4) and [Co(phen)3][(UO2)3(C9)3(O)]•H2O (5) contain bis(μ3-oxo)-bridged tetranuclear secondary building units, and they crystallize as deeply furrowed 2D assemblies. Depending on the nature of the counterion, C102- gives [Ni(bipy)3][(UO2)2(C10)3]•2H2O (7), a 2D network displaying elongated decanuclear rings containing the counterions, or [Mn(phen)3][(UO2)2(C10)3]•6H2O (8), [Co(phen)3][(UO2)2(C10)3]•7H2O (9), and [Ni(phen)3][(UO2)2(C10)3]•7H2O (10), which consist of 2D assemblies with honeycomb topology; the hexanuclear rings in 8-10 are chairlike and occupied by one counterion and two uranyl groups from neighboring layers. Two complexes of the ligand with the longest chain, C122-, are reported. [UO2(C12)(bipy)] (11) is a neutral 1D species in which bipy chelates the uranyl ion and plays an important role in the packing through π-stacking interactions. Two polymeric units, 1D and 2D, coexist in the complex [Ni(bipy)3][(UO2)2(C12)3][UO2(C12)(H2O)2]•H2O (12); the 2D network has the honeycomb topology, but the hexanuclear rings are markedly convoluted, with local features akin to those in helicates, and the counterions are embedded in intralayer cavities. Emission spectra measured in the solid state show in most cases various degrees of quenching, with intense and well-resolved uranyl emission being observed only for complexes 2 and 11. [ABSTRACT FROM AUTHOR]

The ionothermal reactions of uranyl nitrate and 1,3-pbpH4 (1,3-pbpH4 = 1,3-phenylenebis(phosphonic acid) ligand in ionic liquids of [C4mim][Dbp], [C4mpyr][Br], and [Etpy][Br], respectively, afforded three new uranyl phosphonates, namely [C4mim][(UO2)2(1,3-pbpH)(1,3-pbpH)·Hmim] (1), [UO2(1,3-pbpH2)H2O·mpr] (2), and [Etpy][UO2(1,3-pbpH2)F] (3). Compound 1 exhibits a rare example of a chiral uranyl phosphonate 3D framework structure built from achiral building units of tetragonal bipyramidal uranium polyhedra and 1,3-pbp ligands. The structure adopts a network with channels extending along the b axis, which are filled with C4mim+ and protonated 1-methylimidazole. In sharp contrast, compounds 2 & 3 both show pillared topology composed of uranyl pentagonal bipyramid polyhedra and phosphonate ligands. The layers are neutral in compound 2 with N-methylpyrrole molecules in the interlayer space, while compound 3 adopts anionic layer, and the charge is compensated with N-ethyl-pyridinium cations between the layers. Although compounds 1, 2, and 3 were synthesized under identical conditions with sole variation of the ionic liquid species, the resulting structures show a rich diversity in the local coordination environment of uranyl ions, the protonation of the phosphonate ligand, the conformation of ionic liquid ions, and the overall arrangement of the structure. All compounds were characterized by absorption, temperature dependent fluorescence, as well as infrared and Raman spectroscopies. [ABSTRACT FROM AUTHOR]

Three urate chelations were obtained when uric acid was reacted with UO 2 (CH 3 COO) 2 H 2 O, VOSO 4 ·XH 2 O and ZrOCl 2 ·XH 2 O salts with neutralized with 0.1 M NaOH aqueous media. The 1:2 metal-to-ligand complexes [(UO 2 ) 2 (C 5 H 2 N 4 O 3 ) 2 ](H 2 O), [(ZrO) 2 (H 2 O) 2 (C 5 H 2 N 4 O 3 ) 2 ] and [VO((C 5 H 3 N 4 O 3 ) 2 ] were characterized by elemental analyses, molar conductivity, (infrared, Raman and UV–vis) spectra, effective magnetic moment in Bohr magnetons, and thermal analysis (TG/DTG). The urate ligand coordinates as mononegative bidentate donor towards the mononuclear central vanadium atom and coordinated as binegative tetradentate mode towards the binuclear dioxouranium and zirconyl centers. The antibacterial activity of the metal complexes were tested against some kind of bacteria and fungi strains and compared with uric acid. The ligand, ZrO(II) and UO 2 (II) complex showed a week potential degradation on calf thymus DNA, whereas VO(II) complex slightly degraded the DNA. [ABSTRACT FROM AUTHOR]

The mean particle size and size distribution of Ammonium Di-Uranate (ADU) particles, precipitated during the precipitation reaction of Uranyl Nitrate Pure Solution (UNPS) with ammonia play an important role on the sintered density of UO 2 pellets. The quality of precipitated ADU depends on number of process parameters viz. , pH of UNPS, concentration of uranium in UNPS, flow rate of ammonium hydroxide, temperature etc. However, the effects of the presence of free acid and entrained Tri-Butyl-Phosphate (TBP) in UNPS on the quality of ADU powder were not studied till date. Experiments were conducted to study the effect of free acidity and the presence of entrained TBP on the quality of precipitated ADU particles. It was found that as the concentration of free acid as well as the concentration of entrained TBP in UNPS increases, the particle size of precipitated ADU decreases. Based on the experimental results two correlations were developed to determine the mean particle size of ADU; one is based on the free acid content of UNPS and the other is based on the content of entrained TBP in UNPS, which is used for the precipitation. It was found that the correlated values are well fitted with the experimental data within ±3% errors for both the cases. Both these correlations are applicable when other process parameters remain constant. The experimental details and results are discussed in this paper. [ABSTRACT FROM AUTHOR]

Two uranyl complexes based on pyromellitic acid were hydrothermally synthesized, and their X-ray single-crystal diffraction structures were determined. Complex [UO2(Hbtec)]-(Himd)+ ·H2O ( 1) (H4btec = pyromellitic acid, imd = imidazole), is an ionic complex, which shows a typical (4, 4) topological structure in the space. A heterometallic complex, UO2Cu(btec)(phen) ( 2) (phen = 1,10-phenanthroline) results from the reaction of uranyl nitrate and copper(II) bromide with pyromellitic acid. The structure of complex 2 revealed that the chains of UO7 and CuO3N2 units were connected to each other through the carboxyl groups and U=O-Cu interactions to create a two-dimensional framework. [ABSTRACT FROM AUTHOR]

Self-assembly of uranyl peroxide polyoxometalates (POMs) in alkaline peroxide solutions has been known for almost a decade, but in these dynamic solutions that contain high concentrations of base and peroxide the reaction pathway could never be discerned, mixed species are obtained, and reproducibility is sometimes a challenge. Here we elucidate the reaction mechanisms utilizing self-assembly of the U24 cluster, [UO2(O2)(OH)]2424-, from monomers as a model system. Using Raman as our main spectroscopic probe, we learned that the monomeric species is persistent in water at room temperature indefinitely. However, if a redox-active transition metal catalyst (copper (Cu2+) or cobalt (Co2+)) is added, self-assembly is accelerated in a significant manner, forming U24 peroxide clusters in several hours, which is a good time scale for studying reaction mechanisms. From semiquantitative treatment of the spectroscopic data, we elucidate reaction mechanisms that are consistent with prior structural and computational studies that suggest uranyl peroxide rings templated by alkalis are the building units of clusters. By understanding aqueous speciation and processes, we are moving toward assuming control over cluster self-assembly that has been mastered for decades now in the analogous transition-metal POM systems. [ABSTRACT FROM AUTHOR]

Determination of trace uranyl ions was performed by using mixed micellar system and spectrophotometric determination. The method is based on cloud point extraction of uranyl ions after formation of an ion-association complex in the presence of Celestine Blue and sodium dodecyl sulfate. Then, the formed complex was extracted to non-ionic surfactant phase of Triton X-114 at pH 8.0. The optimal extraction and reaction conditions (e.g. concentrations and types of surfactants, concentration of complex forming agent, incubation conditions) were studied and analytical characteristics of the method (e.g. limit of detection, linear range, pre-concentration factor) were obtained by experimental studies. Linearity was obeyed in the range of 50-1,500 ng mL for uranium(VI) ion and the detection limit of is 14.20 ng mL. The interference effects of common ions were also tested and validation studies were performed by using recovery test. The method was applied to the determination of uranium(VI) in several real samples. [ABSTRACT FROM AUTHOR]

Ionothermal methods were employed in the synthesis of two novel uranyl coordination compounds: [C5H6N]2 [UO2(C7H7SO3)4(H2O)] (1) and UO2(HAsO4)(NC5H11O2)(2), using pyridiniumand betainiumclass ionic liquids. The results show novel ionic liquid incorporation and uranyl structural topologies, providing insight into the development of low-dimensionality uranyl complexes beyond traditional hydrothermal methods. [ABSTRACT FROM AUTHOR]

Ionothermal reactions of uranyl salts in several ionic liquids containing cyclic cations produced single crystals of five new uranyl compounds. (C4H7N2)[(UO2)(AsO4)] (1), (C8H15N2)2[(UO2)4(SeO3)5](2), (C6H11N2)2[(UO2)3(C2H5PO4)4](3), and (C5H5N)2[(UO2)2(SeO4)3](4) are each comprised of two-dimensional structural units. (C4H7N2)[(UO2)5(PO4)3(HPO4)(H2O)2]⋅3H2O(5) is composed of a three-dimensional network. While the uranyl structural units in all five compounds are directly related to ones found in either uranyl minerals or compounds produced in aqueous media, each contain cyclic ionic liquid constituents as charge-balancing agents. These results suggest that the cation selectivity of these structural units is low, even under various solvation conditions and templating effects from cyclic cations donated from ionic liquid media. [ABSTRACT FROM AUTHOR]

Monometallic (UO)(X)(L) (L = pyridine (py), X = F ( 1), Cl ( 2), Br ( 3) and I ( 4); L = tetrahydrofuran (thf), X = Cl ( 5); L = pyrrole (pl), X = Cl ( 6)) as well as bimetallic [(UO)(μ-X)(X)(L)] (L = py, X = F ( 7), Cl ( 8), Br ( 9) and I ( 10); L = thf, X = Cl ( 11); L = pl, X = Cl ( 12); μ = doubly bridged) were examined using relativistic density functional theory. With changing from F, Cl, Br to I irregardless of in mono- or bis-uranyl complexes, bond lengths of U = O were calculated to be decreasing, resulting from strengthening of axial U = O bonds while weakening equatorial X → U coordination. This is further evidenced by calculated bond orders of U = O and stretching vibrational frequencies. A similar situation was is found in 2, 5 and 6 as well as in 8, 11 and 12, where N/O ligands are varied but the chlorine atoms are retained. The present study reveals that all these complexes have U( f)-character low-lying unoccupied orbitals, and their π*(U = O) antibonds are located on higher-energy orbitals. Complex 1 was calculated to show σ(U = O) bonding character for HOMO, and pyridine-character for other occupied orbitals; the fluorine ligand occurs in a relatively low-energy region. In contrast, the π( p) characters of heavier halogen atoms significantly contribute to most frontier molecular orbitals of 2, 3 and 4. Unlike this electronic feature of 2, complexes 5 and 6 exhibit mainly thf and pyrrole characters, respectively, for their high-lying occupied orbitals. Electronic structures of bisuranyl complexes 7- 12, albeit a little more complicated, are revealed to be similar to those of the corresponding monouranyl complexes. Finally, energies of formation reactions of the above complexes were calculated and compared with available experimental results. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The chemiluminescence (CL) kinetics in U(IV) oxidation by atmospheric oxygen in aqueous HClO has been investigated. The CL quantum yield (η, E/(mol U(IV))) in this reaction is 1.4 × 10. The elementary event generating the CL emitter, which is the electronically excited uranyl ion *(UO), is electron transfer from the uranyl ion UO to the oxidizer (OH radical). The Ag ion quenches CL, and the Cu ion enhances CL. [ABSTRACT FROM AUTHOR]

We present here two systems of [dabcoH2]2+–uranyl–oxalate and [pipH2]2+–uranyl–oxalate in which [dabcoH2]2+and [pipH2]2+arecations ofdoubly protonated 1,4-diazabicyclo-[2.2.2]-octane (dabco) andpiperazine (pip), respectively. Each system yielded two differentcrystals and showed the reversible crystal-to-crystal transformationsbetween them in aqueous solutions, controlled by the ratio of reactantsor building blocks in the reaction systems. The four compounds inpairs are [dabcoH2][UO2(C2O4)2(H2O)]·2H2O (dabco1) and [dabcoH2][(UO2)2(C2O4)3(H2O)2]·2H2O (dabco2), and [pipH2][UO2(C2O4)2(H2O)]·4H2O (pip1) and [pipH2][(UO2)2(C2O4)3(H2O)2]·2H2O (pip2). Besides the cations and lattice water, dabco1and pip1contain mononuclear anions of [UO2(C2O4)2(H2O)]2–, whereas dabco2and pip2possess dinuclearanions of [(UO2)2(C2O4)3(H2O)2]2–, and in all structures, the uranium ion shows a pentagonal bipyramidenvironment made up of equatorial oxalate, water, and apical oxygen.The needle crystals of dabco1belong to the chiral spacegroup P6522. In the structure, the [UO2(C2O4)2(H2O)]2–anions form anionic helixes alongthe 65axis and they are further linked by N–H···Ohydrogen bonds between the interhelix [dabcoH2]2+cation and oxalates of the anion. Disorder of lattice waterand the [dabcoH2]2+cation is observedin dabco1. The thin plate crystals of pip1in space group P1̅ possess a lamellar structure,with dense layers of [pipH2]2+·2[UO2(C2O4)2(H2O)]2–pillared by other crystallographicallyunique [pipH2]2+cations, and the structurecontains lattice water forming branched zigzag water chains. Blockcrystals of dabco2and pip2, in monoclinicspace groups C2/cand P21/c, respectively, are of similar layer-likestructures, possessing the dinuclear [(UO2)2(C2O4)3(H2O)2]2–anion with one tetradentate oxalatebridge. The anions and ammonium cations form chains by N–H···Ohydrogen bonds between them and then further form stacked layers viaO–H···O hydrogen bonds among the coordinatedand lattice water and the oxalate ligands. The ratio of diammonium/uranyl/oxalatein the reaction systems controlled the final outcomes and the occurrenceof transformation, no transformation, and reverse transformation.The thermal stability; UV–vis, IR, and Raman spectra; and luminescencewere also investigated. [ABSTRACT FROM AUTHOR]

Three new potassium uranyl borates, K12[(UO2)19(UO4)(B2OS)2(BO3)6(BO2OH)O10] nH2O (TPKBUO-l), K4[(UO2)5(BO3)2O4]-H2O (TPKBUO-2), and K15[(UO2)18(BO3)7O15] (TPKBUO-3), were synthesized under high-temperature/high-pressure conditions. In all three compounds, the U/B ratio exceeds 1. Boron exhibits BO3 coordination only, which is different from other uranyl borates prepared at room temperature or under mild hydrothermal conditions. A rare uranium(Vl) tetraoxide core UO4O2, which is coordinated by two BO3 groups, is observed in the structure of TPKBUO-l. Both structures of TPKBUO-l and TPKBUO-3 contain three different coordination environ-ments of uranium, namely, UO4O2, UO2O4, and UO2O5 and UO2O4 UO2O5, and UO2O6 bipyramids in TPKBUO-l and TPKBUO-3, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of triuranyl diphosphate tetrahydrate precursor (UO2)3(PO4)2(H2O)4 with a CsI flux at 750°C yields a yellow single crystals of new compound Cs3(UO2)2(PO4)O2. The crystal structure (monoclinic, space group C2/c, a=13.6261 (13)Å, b=8.1081(8)Å, c=12.3983(12)Å, β=114.61(12)°, V=1245.41(20)Å3 with Z=4) has been solved using direct methods and Fourier difference techniques. A full-matrix least-squares refinement on the basis of F 2 yielded R1=0.028 and wR2=0.071 for 79 parameters and 1352 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a charge-coupled device detector. The crystal structure is built by two independent uranium atoms in square bipyramidal coordination, connected by two opposite corners to form infinite chains and by one phosphorus atom in a tetrahedral environment PO4. The two last entities and PO4 are linked by sharing corners to form a three-dimensional structure presenting different types of channels occupied by Cs+ alkaline cations. Their mobility within the tunnels were studied between 280 and 800°C and compared with other tunneled uranyl minerals. The infrared spectrum shows a good agreement with the values inferred from the single crystal structure analysis of uranyl phosphate compound. [Copyright &y& Elsevier]

Abstract: Sorption of U(VI) on sepiolite and HDTMA–sepiolite was studied by investigating sorption isotherms and the influence of pH on sorption percentage P for initial U(VI) concentrations of 0.0001–0.001mol/dm3. Sorption isotherms were linear both for nitrates and acetate solutions, which was explained as a consequence of the precipitation of U(VI) hydroxycomplexes on the surface of the mineral. pH>9 was optimal for U(VI) sorption on HDTMA–sepiolite, and this fact was related to the sorption of U(VI) anionic complexes on the positively charged surface of the sorbent. The respective chemical reactions for the sorption of different species were proposed. [Copyright &y& Elsevier]

The reaction of uranyl nitrate hexahydrate with 2-sulfobenzoate (SB2-) in the presence of various amines gave the series of complexes [UO2(SB)(H2O)] (I), [UO2(SB)(H2O)]2-pyz (2), [2,2'-bipyH]2- [UO2(SB)2(H2O)]-4H2O (3), [4,4'-bipyH2]2[UO2(SB)2]2 (4), [4,4'-bipy-H]2[(UO2)2(SB)3(H2O)]-4H2O (5), [NMe4]2[(UO2)2(SB)3(H2O)us]-1.35H2O (6), [NMe4]2[(UO2)3(SB)2O2] (7), and [H2DABCO]2-[(UO2)5(SB)4O2(OH)2]-4H2O (8), where pyz = pyrazine, bipy = bipyridine, and DABCO = l,4-diazabicyclo[2.2.2]octane, with all compounds but 5 having been obtained under hydrothermal conditions. The crystal structures of these complexes display a common motif in which uranyl is chelated by the carboxylate and sulfonate groups of SB, giving a seven-membered ring. Structure-directing effects due to the amine and the presence in 7 and 8 of additional μ3-oxo or μ2-hydroxo bridges result in much structural variety, with different bridging by the carboxylate and sulfonate groups giving rise to zero-(3,4), one- (1, 5--8), or two-dimensional (2) assemblies. Some unusual uranyl secondary building units are observed, such as the pentanudear [(U02)5O2(OH)2] discrete motif. Addition of 3d-block metal cations (Cu2+, Ni2+) in the presence of nitrogen donors gave the heterometallic molecular complex [UO2Cu(SB)2(2,2'-bipy)2]2-2H2O (9), the heterogeneous compound [Cu(4,4'-bipy)(H2O)3]2[UO2(SB)2]2 2H2O (1O), in which molecular uranyl dimers are encompassing copper-containing chains, and the heterometallic one-dimensional polymers [(UO2)2Cu2(SB)4(bipym)(H2O)4] (11) and [UO2Ni(SB)2(bipym)-(H2O)2]-3H2O (12), where bipym = bipyrimidine. The latter two complexes display two different arrangements: in 11, bipym bridges two [UO2Cu(SB)2] chains to give a ladderlike assembly, while the uranyl cations are merely decorating species in 12. In contrast to those of phosphonates, the actinide complexes of sulfonates in the solid state have been little investigated up to now. The present results show that sulfocarboxylates such as 2-sulfobenzoate, in which sulfonate coordination is promoted by chelate effects, are of interest in the synthesis of uranyl--organic coordination polymers. [ABSTRACT FROM AUTHOR]

Combined collision-induced dissociation mass spectrometry experiments with DFT and MP2 calculations were employed to elucidate the molecular structures and energetics of dissociation reactions of uranyl species containing acetone and diacetone alcohol ligands. It is shown that solutions containing diacetone alcohol ligands can produce species with more than five oxygen atoms available for coordination. Calculations confirm that complexes with up to four diacetone alcohol ligands can be energetically stable but that the effective number of atoms coordinating with uranium in the equatorial plane does not exceed five. Water elimination reactions of diacetone alcohol ligands are shown to have two coordination-dependent reaction channels, through formation of mesityl oxide ligands or formation of alkoxide and protonated mesityl oxide species. The present results provide an explanation for the implausible observation of "[UO2(ACO)6,7,8]2+" in and observed water-elimination reactions from purportedly uranyl-- acetone complexes (Rios, D.; Rutkowski, P. X.; Van Stipdonk, M. J.; Gibson, J. K. Inorg. Chem. 2011, 50, 4781). [ABSTRACT FROM AUTHOR]

The hydrothermal reaction of uranyl nitrate and 1,4-benzenebisphosphonicacid in the presence of monovalent and divalent metal hydroxides resultsin the formation of four new uranyl coordination polymers: Ag2{(UO2)[C6H4(PO3H)2]2} (AgUbbp), Cs{(UO2)[C6H4(PO3H0.5)2]} (CsUbbp), [Ba(H2O)3]{(UO2)3[C6H4(PO3)2]2(O)}·5(H2O) (BaUbbp), and [Sr(H2O)3]{(UO2)2[C6H4(PO3)2](OH)2(H2O)}·3(H2O) (SrUbbp). AgUbbpand CsUbbpcomplexes are constructedfrom UO6units with tetragonal bipyramidal coordinationgeometries, whereas BaUbbpand SrUbbpcomplexescontain UO7units with pentagonal bipyramidal coordinationenvironments. The pH and the monovalent/divalent metal cations havesignificant effects on the topology of these structures. These compoundsfluoresce at room temperature owing to emission from the uranyl units. [ABSTRACT FROM AUTHOR]

Abstract: 2,3-Dimethyl-2,3-butanediol (pinacol, L1) reacted with uranyl nitrate and acetate hydrates to give [UO2(NO3)2(L1)]·L1 (1·L1) and [UO2(OAc)2(L1)] (2), while 2,5-dimethyl-3,4-di-iso-propyl-3,4-hexanediol (L2) was found to undergo a pinacol rearrangement into the ketone R3CCOR (R= iPr) in the presence of uranyl complexes. Treatment of [UO2(NO3)2(H2O)2]·4H2O with tetrahydrofurfuryl alcohol (L3) and α,α-ditertiobutyltetrahydrofurfuryl alcohol (L4) led to the formation of [UO2(NO3)2(L3)]·H2O (3·H2O) and [UO2(NO3)2(L4)] (4). The crystal structures show that the metal coordination is similar in the 1,2-diol and ether–alcohol complexes but, in contrast to 1·L1, 2 and 3·H2O which form one- or two-dimensional hydrogen bonded assemblages, the structure of 4 is composed of discrete molecules, due to the lack of intermolecular hydrogen bonds. The crystal structure of uncomplexed L2 is also described. [Copyright &y& Elsevier]

A uranyl triazole (U02)2[U04(trz)2](OH)2 (1) (trz = 1,2,4-triazole) was prepared using a mild solvothermal reaction of uranyl acetate with 1,2,4-triazole. Single-crystal X-ray diffraction analysis of 1 revealed it contains sheets of uranium-oxygen poledra and that one of the U(VI) cations is in an unusual coordination polyhedron that is intermediate between a tetraoxido core and a uranyl ion. This U(VI) cation also forms cation--cation interactions (CCIs). Infrared, Raman, and XPS spectra are provided, together with a tlierraogravimetric analysis that demonstrates breakdown of the compoimd above 300 °C. The UV--vis-NIR spectrum of 1 is compared to those of another compound that has a range of U(Vl) coordination enviromments. [ABSTRACT FROM AUTHOR]

Ion populations formed from electrospray of uranyl nitrate solutions containing different amides vary depending on ligand nucleophilicity and steric crowding at the metal center. The most abundant species were Ion pair complexes having the general formula [UO2(NO3)(amide)n=2,3]+; however, singly charged complexes containing the amide conjugate base and reduced uranyl UO2+ were also formed as were several doubly charged species. The formamide experiment produced the greatest diversity of species resulting from weaker amide binding, leading to dissociation and subsequent solvent coordination or metal reduction. Experiments using methyl formamide, dimethyl formamide, acetamide, and methyl acetamide produced ion pair and doubly charged complexes that were more abundant and less abundant complexes containing solvent or reduced uranyl. This pattern is reversed in the dimethylacetamide experiment, which displayed lower abundance doubly charged complexes, but augmented reduced uranyl complexes. DFT investigations of the tris-amide ion pair complexes showed that interligand repulsion distorts the amide ligands out of the uranyl equatorial plane and that complex stabilities do not increase with increasing amide nucleophilicity. Elimination of an amide ligand largely relieves the interligand repulsion, and the remaining amide ligands become closely aligned with the equatorial plane in the structures of the bis-amide ligands.The studies show that the phenomenological distribution of coordination complexes in a metal-ligand electrospray experiment is a function of both ligand nucleophilicity and interligand repulsion and that the latter factor begins exerting influence even in the case of relatively small ligands like the substituted methyl-formamide and methyl-acetamide ligands. [ABSTRACT FROM AUTHOR]

The reaction of [UO2I2(THF)3] with KC5R5 (R = H, Me) or K2C8H8 in pyridine gave crystals of [{UO2(py)5}{KI2(py)2}]. (1), which were desolvated under vacuum into pulverulent [UO2(py)2.2KI2] (2). Similar reactions with [UO2(OTf)2] afforded [UO2(py)2.3K(OTf)2] (3) as a powder and crystals of [{UO2(py)5}2{K3(OTf)5}.py]. (4.py), which were also obtained together with crystals of [{UO2(py)5}2{K(OTf)2(py)2}][OTf].py (5.py) by treating [UO2(OTf)2] with KC4Me4P. Crystals of 6.py, the thallium analogue of 5.py, were isolated from the reaction of [UO2(OTf)2] and TlC5H5. Treatment of [UO2I2(THF)3] with LiCH2SiMe3 in pyridine afforded crystals of [{UO2(py)5}{LiI(py)2}][I] (7) while [UO2(OTf)2] reacted with the alkyllithium reagent in acetonitrile to give crystals of [{UO2(py)5}{Li2(OTf)3}]. (8) in pyridine. The crystal structures of 1, 4.py, 5.py, 6.py, 7 and 8 revealed the presence of U=O→M interactions (M = Li, K, Tl), and the rich diversity of these structures, from dinuclear (7) to 3D polymeric (4), is related to the distinct coordination numbers of the M+ ion and ligation modes of the bridging iodide and triflate ligands as well as the presence of U=O→M interactions. The mononuclear complexes [UO2(OTf)(THF)n] (9) and [UO2(OTf)(Et2O)0.5] (10) were respectively obtained by reaction of [UO2(OTf)2] with KC5R5 in THF or LiCH2SiMe3 in Et2O, and were transformed into [UO2(OTf)(py)2] (11) in pyridine. Treatment of [UO2I2(THF)3] with TlC5H5 in pyridine afforded crystals of [UO2(py)5][I].py (12.py) which were desolvated under vacuum into the powder of [UO2I(py)2.5] (14). The same reaction in THF gave [UO2I(THF)2.7] (13) in powder form. Crystals of [UO2(CyMe4BTBP)(py)][OTf].1.5py (15.1.5py) and the powder of [UO2I(CyMe4BTBP)] (16) were obtained by treating [UO2(CyMeBTBP)X2] (X= OTf, I) with KC5Me5 or TlC5H5, respectively. The uranyl(V) chloride and nitrate compounds [UO2Cl(py)3] (17) and [UO2(NO3)(py)3] (18) were prepared by reaction of the uranyl(VI) precursors with TlC5H5 in pyridine; complex 18 was also obtained by treating 13 with TlNO3. Crystals of the neutral mononuclear complex [UO2(OTf)(py)4] (19) were isolated from reaction of [UO2(OTf)2] with Me3SiC5H5 in acetonitrile. Similar reaction with [UO2Cl2(THF)2]2 in pyridine gave crystals of [UO2Cl2(py)3]. The crystal structures of 12.py, 15.1.5py and 19 were determined; the structure of 15 was compared with that of the uranyl(VI) counterpart. All the uranyl(V) compounds are remarkably stable in pyridine solution; the IR absorption at 816 cm-1 is attributed to the nasym(U=O) of the ubiquitous [UO2(py)5]+ species. [ABSTRACT FROM AUTHOR]

The reaction between [UO2(ReO4)2*H2O] and two equivalents of either tri-n-butyl phosphine oxide (TBPO) or tri-iso-butyl phosphate (TiBP) results in the formation of [UO2(µ2-ReO4)(ReO4)(TBPO)2]2 (1) and [UO2(µ2-ReO4)(ReO4)(TiBP)2]2 (2) respectively. Both complexes crystallise as two structurally similar centrosymmetric dimers, the cores containing two uranyl moieties linked by bridging perrhenates. Two P=O donor ligands and one monodenatate perrhenate complete the pentagonal bipyramidal coordination sphere at each metal centre. Both complexes have also been characterised in the solid state by vibrational and absorption spectroscopy. Solution spectroscopic characterisation indicates that both perrhenate and phosphine oxide (1) or phosphate (2) remain coordinated, although it is not possible to state conclusively that the dimeric species remain intact. A low resolution structural study of a minor product from the reaction that yielded 2 revealed a monomeric complex with only monodentate perrhenate coordi- nation, [UO2(ReO4)2(H2O)(TiBP)2] (2'). These results represent the first structural evidence for the bridging coordination mode of perrhenate on coordination to an actinide and yields further insight into the possible solvent phase pertechnetate complexes that may exist in PUREX process phosphate rich solvent. [ABSTRACT FROM AUTHOR]