A new uranyl(VI) complex of rigid V-shaped carboxylate ligand: Synthesis,structure and properties

Reaction of uranium oxynitrate hexahydrate with 4, 4″-Dicarboxyl-(1,1′,3′,1″)-Terphenyl (H₂L) by liquid diffusion method resulted in a complex {[UO₂(L)(DMF)]·H₂O}_n. Single-crystal diffraction analysis shows that the uranyl ion is in a pentagonal bipyramid coordination environment. Five oxygen atoms of L^2? ligands and DMF constructed the equatorial plane. Two oxygen atoms of uranyl occupy the two axial positions. The complex got the two-dimensional layered structure by π–π interactions. The thermal analysis verifies the component and the structure of the complex. The UV/vis measurement exhibits that the complex has strong absorption in the UV and visible region.     

Supramolecular assemblages from uranyl complexes of calixarenes and potassium complexes of 18-crown-6 or dibenzo-18-crown-6

Reaction of uranyl nitrate with p-tert-butyl[3.1.3.1]homocalixarene (L¹H₄) or p-tert-butylcalix[8]arene (L²H₈) has been carried out in the presence of KOH and 18-crown-6 (18C6) or dibenzo-18-crown-6 (db18C6), giving the supramolecular assemblages [K(db18C6)(H₂O)₂]₃ [{UO₂(L¹)}₂K(H₂O)₅] (1) and [K(18C6)(OH)₂][{(UO₂)₂(L²H₅)(OH)}{K(18C6)}] (2). Compound 1 comprises a sandwich, “complex-within-complex” assemblage in which two uranyl/calixarene complexes encompass a potassium/crown ether guest. A direct bond between uranyl and K(18C6) is present in 2, in which a columnar arrangement of alternate dimetallic calixarene complexes and potassium/crown ether species is formed.     

Dioxouranium complexes with ‘Jaeger-type’ ligands

Azomethine ligands with electron-withdrawing groups such as bis{N,N^′-(2-ethoxycarbonyl-3-oxo-but-1-en(1)yl)-1,2-diaminobenzene (H₂L¹) or N-(2-ethoxycarbonyl-3-oxo-but-1-en(1)yl)-2-aminophenol (H₂L²) react with uranyl nitrate under deprotonation and formation of chelate complexes. The composition of the products can be controlled by the reaction conditions and the denticity of the ligands. Structure determinations have been performed on [NEt₃H][UO₂(L¹)(OMe)], [UO₂(L¹)(DMSO)] and [NEt₃H]₂[{UO₂(L²)}₃(μ₃-O)].     

Uranyl complex with phenolate–sulphonate and diphenyldiazenecarbohydrazonate ligands

Reaction of uranyl nitrate hexahydrate with 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxybenzenesulfonic acid (H₃L) and bis((E)-phenyldiazenyl)methanone (bpm) yields mononuclear zwitterionic uranyl complex, [UO₂(HL)(bpm)(H₂O)₂]∙3H₂O (1), which was characterized by IR, ESI-MS spectroscopies, and elemental and X-ray single-crystal analyses. In 1, the uranium center is in distorted pentagonal bipyramidal geometry with HL^2 − and bpm ligands coordinated in equatorial plane. The coordination to uranyl and intramolecular hydrogen bonding assist the tautomerization of bpm and formation of zwitterion.     

A new clover-shaped trinuclear uranium(VI) complex: Synthesis,structure and photoluminescence property

A new clover-shaped trinuclear uranium(VI) complex of the formula [(UO₂)₃(phen)₃(μ₃-O)(μ₂-OH)₂(NO₂)]·NO₃·3DMF·H₂O (1) (phen = 1,10-phenanthroline, DMF = N,N′-dimethylformamide) was prepared by reaction of UO₂(NO₃)₂·6H₂O and phen under ultrasonic condition. X-ray single-crystal diffraction analysis shows that each U(VI) ion is in a seven-coordinated pentagonal–bipyramidal environment, with two O atoms in axial positions forming a uranyl ion. Each uranyl ion in 1 is coordinated by one chelating phen ligand and three O atoms at the equatorial plane. Interestingly, one central μ₃-oxo incorporates two μ₂-OH^? and one NO₂^? to link uranyl ions into a clover-shaped motif. The molecules of 1 are packed within the space through hydrogen bonds, π···π and lone-pair···π interactions. The solid diffuse-reflectance UV/vis and photoluminescence spectra of 1 were measured and discussed.     

Thermal decomposition of uranyl sulphate hydrate

The thermal decomposition of uranyl sulphate hydrate (UO₂SO₄-3H₂O) has been investigated by thermogravimetry, differential thermal analysis, X-ray diffraction and infrared spectrophotometry. As a result, it is concluded that uranyl sulphate hydrate decomposes thermally.     

Syntheses,structures, and properties of two dinuclear palladium (II) complexes of a single macrocyclic hexaaza ligand with two hydroxyethyl pendants

Two dinuclear palladium (II) complexes, trans-[Pd₂LCl₂](ClO₄)₂ · 2H₂O and cis-[Pd₂LCl₂]Cl₂ · 2H₂O, of a single macrocyclic ligand with two hydroxyethyl pendants, L (L = 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)tricyclo[22,2,2,2^11,14]triaconta-1,11,13,24,27,29-hexaene), have been synthesized as “inorganic proteases” and analyzed by X-ray diffraction method. The two complexes-mediated hydrolytic cleavage of amide bond in acetyl methionyl alanine has been monitored by ¹H NMR, showing a moderate hydrolytic rate at 50 °C and pH ca. 1.0. The pendent hydroxyl group is responsible for the hydrolytic reaction.     

An organic–inorganic hybrid uranyl nicotinate molybdate polymer and its fluorescent property

A uranyl nicotinate molybdate polymer [UO₂(nicot)(MoO₃OH)]_n (Hnicot = nicotinic acid, NC₅H₄CO₂H) was synthesized by the hydrothermal reaction of uranyl nitrate [UO₂(NO₃)₂ · 6H₂O], phosphomolybolic acid (H₃PMo₁₂O₄₀) and nicotinic acid. Its crystal structure and fluorescent property were measured. The results show that the crystal packs in the 1D chains of uranyl molybdates with strong fluorescence at the range of 470–520 nm.     

A novel uranyl complex UO2(tci)(C3H5N2) · H2O: Synthesis,crystal structure and characterization

Reaction of uranium oxynitrate hexahydrate with tris(2-carboxyethyl)isocyanurate (tciH₃) in acidic aqueous solution (pH ～4–5) yields the compound UO₂(tci)(C₃H₅N₂) · H₂O. X-ray diffraction shows that the uranyl ion is in a hexagonal bipyramid structure. Uranium ion in the complex is found to be ligated with three chelating COO^? groups at the equatorial plane, two oxygen atoms linking to uranium atom formed the vertical axis. The complex has the layered topology structure in the space. The thermal analysis verifies the component and the structure of the complex.     

Uranyl Coordination Polymers Incorporating η5-Cyclopentadienyliron-Functionalized η6-Phthalate Metalloligands: Syntheses,Structures and Photophysical Properties

The reaction of two η⁵-cyclopentadienyliron(II)-functionalized terephthalate and phthalate metalloligands, namely [(η⁵-C₅H₅)Fe^II(η⁶-1,4-HO₂CC₆H₄CO₂H)][(η⁵-C₅H₅)Fe^II(η⁶-1,4-HO₂CC₆H₄CO₂)][PF₆] and [(η⁵-C₅H₅)Fe^II(η⁶-1,2-HO₂CC₆H₄CO₂H)][(η⁵-C₅H₅)Fe^II(η⁶-1,2-HO₂CC₆H₄CO₂)][PF₆]—hereafter [H₂ CpFeTP][HCpFeTP][PF₆] and [H₂ CpFeP][HCpFeP][PF₆], respectively—with [UO₂(NO₃)₂]·6H₂O under hydrothermal conditions yielded four new coordination polymers; (1) [(UO₂)F(HCpFeTP)(PO₄H₂)]·2H₂O, (2) [(UO₂)₂(CpFeTP)₄]·5H₂O, (3) [(UO₂)₂F₃(H₂O)(CpFeP)], and (4) [H₂ CpFeP][UO₂F₃]. The use of metalloligands has proven to be a viable route towards the incorporation of a secondary metal center into uranyl bearing materials. Depending upon the protonation state, the iron sandwich metalloligands may vary from zwitterionic neutral or monoanionic coordinating species as observed in compounds 1–3, or a positively charged species that hydrogen bonds with anionic [UO₂F₃]^? chains as observed in 4. Further, the hydrolysis of the charge balancing PF₆ ^? anion increases the diversity of UO₂ ²⁺ coordinating species by contributing both F^? and PO₄ ^3? anions (1, 3, 4). The luminescent properties of 1–4 were also studied and revealed the absence of uranyl emission, suggestive of a possible energy transfer from the uranyl cation to the iron(II) metal center.     

Uranyl adsorption on (001) surfaces of kaolinite: A molecular dynamics study

The aim of the present paper is to investigate the adsorption of uranyl species (UO₂)^2 +(H₂O)₅ onto kaolinite (001) surfaces. To this end we have employed molecular dynamic simulations based on CLAYFF force field potential. Various types of surface model for inner-sphere adsorption complexes and one model for outer-sphere adsorption complexes were optimized. In order to have a neutral structure, the uranyl (UO₂)^2 +(H₂O)₅ or the kaolinite was deprotonated to form the outer-sphere or inner-sphere adsorption complexes. Both singly protonated and partially deprotonated states of the Al(0) kaolinite surface were considered for adsorption in the model of inner-sphere complexes. The first uranyl coordination shell exhibits pentagonal bi-pyramidal symmetry with the pentagonal formed by 5 water molecules. We show that the average U–OW distances are between 2.49 and 2.57 Å for water molecules. The bond of uranyl with deprotonated O⁻ center is always short because of the charge attraction. The obtained results agree well with density functional calculations and EXAFS measurements, and show how and why the adsorption of uranyl appears on the surface of kaolinite.     

X-ray photoelectron spectroscopy study of anodically oxidized SIMFUEL surfaces

The surface composition of anodically oxidized SIMFUEL (doped uranium dioxide) has been determined as a function of applied potential over the range −500 to +500 mV (versus SCE). Cathodically cleaned UO₂ specimens were anodically oxidized for 1 h and subsequently analyzed by XPS. Using published binding energies, the U (4f_7/2) and O (1s) peaks were resolved into contributions from U^IV, U^V, U^VI, O^II, OH⁻ and H₂O. It was shown that over the potential range −500 to approximately +50 mV a thin surface layer of U^IV/U^V oxide (UO_2+x) formed. At more positive potentials, a U^VI hydrated oxide (UO₃·yH₂O) was deposited on the electrode surface. At very positive potentials (≥400 mV) the rapid anodic formation and hydrolysis of UO₂²⁺ led to local acidification in pores in the deposited UO₃·yH₂O layer and its subsequent re-dissolution.     

Rate of Adsorption of Uranium from Seawater with a Calix[6]arene Adsorbent

Abstract

The rate of complex formation between calix[6]arene-p-hexasulfonate and uranyl ion is studied over a wide range of carbonate ion concentrations. The presence of carbonate ion decreases the complexation rate. The distribution of various uranyl species is calculated from a set of mass balances of participating ions with their stability constants. UO₂(CO₃)₃ ^4? has the highest concentration, followed by UO₂(OH)₃ ^? and UO₂(CO₃)₂ ^2?. Other uranyl species are negligible. The complexation rate is proportional to the 0.27–1.0 power of the total concentration of uranyl species other than UO₂(CO₃)₃ ^4?. This implies that the rate-determining step of the complexation is the reaction between calix[6]arene-p-hexasulfonate and UO₂(OH)₃ ^? or UO₂(CO₃)₂ ^2?.     

Two uranyl–organic frameworks with pyridinecarboxylate ligands. A novel heterometallic uranyl–copper(II) complex with a cation–cation interaction

Reaction of uranyl nitrate with pyridine-2-carboxylic acid (HL¹) under hydrothermal conditions gives the complex [(UO₂)₃(L¹)₄(NO₃)₂], 1, which differs from the previously reported molecular complex, obtained at room temperature, by the absence of water, coordinated and free, and the extended carboxylate bridging. Although the trimetallic basic unit is similar in both cases, 1 crystallizes as a two-dimensional assembly. A heterometallic complex results from the reaction of uranyl nitrate and copper(II) trifluoromethanesulfonate with nicotinic acid (pyridine-3-carboxylic acid, HL²), [UO₂Cu(L²)₂(NO₃)₂], 2, in which copper nicotinate two-dimensional subunits are bridged by uranyl nitrate groups to give a three-dimensional framework. The copper atom environment geometry is elongated octahedral, with one of the axial donors being a uranyl oxo group (cation–cation interaction).     

Separation of Uranium from Aqueous Solutions Using Al3+‐ and Fe3+‐modified Titanium‐ and Zirconium Phosphates

Abstract

The ability of four amorphous Al³⁺‐ and Fe³⁺‐doped titanium and zirconium sorbents to separate U(VI) from acidic aqueous solutions (pH_init=3, ionic strength 0.1 M established by NaNO₃) was investigated using a batch technique and instrumental neutron activation analysis. All investigated sorbents were found to be chemically stable and remove considerable amounts of uranium from acidic aqueous solutions (pH_init=3). The scanning electron microscopic and powder‐X‐ray diffraction examination of the grains of the two investigated titanium phosphates after contacting the uranium solutions revealed the formation of sodium autunite (Na₂(UO₂)₂(PO₄)₂ · 6‐8H₂O) accompanied, in the case of the Fe³⁺‐doped titanium phosphate, by iron uranyl phosphate hydroxide hydrate (Fe(UO₂)₂(PO₄)₂(OH) · 7H₂O). No crystal formation was observed in the cases of uranium sorbed by zirconium phosphates indicating the different sorption mechanism involved.     

Nickel(II) Coordination Polymers Supported by Bis-pyridyl-bis-amide and Angular Dicarboxylate Ligands: Role of Ligand Flexibility in Iodine Adsorption

Reactions of N‚N’-bis(3-pyridylmethyl)oxalamide (L¹), N‚N’-bis(4-pyridylmethyl)oxalamide (L²), or N,N’-bis(3-pyridylmethyl)adipoamide) (L³) with angular dicarboxylic acids and Ni(II) salts under hydro(solvo)thermal conditions afforded a series of coordination polymers: {[Ni(L¹)(OBA)(H₂O)]·H₂O}_n (H₂OBA = 4,4-oxydibenzoic acid), 1, {[Ni(L¹)(SDA)(H₂O)₂]·H₂O·CH₃OH}_n (H₂SDA = 4,4-sulfonyldibenzoic acid), 2, {[Ni(L²)(OBA)]·C₂H₅OH}_n, 3, {[Ni(L²)(OBA)]·CH₃OH}_n, 4, {[Ni₂(L²)(SDA)₂(H₂O)₃]·5H₂O}_n, 5, {[Ni₂(L²)(SDA)₂(H₂O)₃]·H₂O·2C₂H₅OH}_n, 6, {[Ni(L³)(OBA)(H₂O)₂]·2H₂O}_n, 7, {[Ni(L³)(SDA)(H₂O)₂]·2H₂O}_n, 8, and {[Ni(L³)₀.₅(SDA)(H₂O)₂]·0.5C₂H₅OH}_n, 9, which have been structurally characterized by using single-crystal X-ray crystallography. Complex 1 exhibits an interdigitated 2D layer with the 2,4L2 topology and 2 is a 2D layer with the sql topology, while 3 and 4 are 3D frameworks resulting from polycatenated 2D nets with the sql topology and 5 and 6 are 2-fold interpenetrated 3D frameworks with the dia topology. Complexes 7 and 8 are 1D looped chains and 9 is a 2D layer with the 3,4L13 topology. The various structural types in 1–9 indicate that the structural diversity is subject to the flexibility and donor atom position of the neutral spacer ligands and the identity of the angular dicarboxylate ligands, while the role of the solvent is uncertain. The iodine adsorption of 1–9 was also investigated, demonstrating that that the flexibility of the spacer L¹–L³ ligands can be an important factor that governs the feasibility of the iodine adsorption. Moreover, complex 9 shows a better iodine adsorption and encapsulates 166.55 mg g⁻¹ iodine in the vapor phase at 60 °C, which corresponded to 0.38 molecules of iodine per formula unit.     

Surface electrochemistry of UO2 in dilute alkaline hydrogen peroxide solutions

The reaction of H₂O₂ on SIMFUEL electrodes has been studied electrochemically and under open circuit conditions in 0.1 mol l⁻¹ NaCl (pH 9.8). The composition of the oxidized UO₂ surface was determined by X-ray photoelectron spectroscopy (XPS). Peroxide reduction was found to be catalyzed by the formation of a mixed U^IV/U^V (UO_2+x) surface layer, but to be blocked by the formation of U^VI (UO₂²⁺) species on the electrode surface. The formation of this U^VI layer blocks both H₂O₂ reduction and oxidation, thereby inhibiting the potentially rapid H₂O₂ decomposition process to H₂O and O₂. Decomposition is found to proceed at a rate controlled by desorption or reduction of the adsorbed O₂ species. Reduction of O₂ is coupled to the slow oxidative dissolution of UO₂ and formation of a corrosion product deposit of UO₃·yH₂O.     

Syntheses and Structural Characterization of Co(II) Coordination Polymers Supported by Bis(<Emphasis Type="Italic">N</Emphasis>-benzimidazolyl)methane and Bis(<Emphasis Type="Italic">N</Emphasis>-imidazolyl)methane

[Co₂(L¹)₂(NCS)₄]·4MeOH 1, [Co(L²)₂(H₂O)₂](Sal)₂·4H₂O (Sal = salicylate) 2 were obtained from self-assembly of the cobalt salts with bis(N-benzimidazolyl)methane (L¹), and bis(N-benzimidazolyl)methane (L²), and their structures were characterized by IR and X-ray diffraction analysis. Complex 1 exhibits a two-dimensional grid structure, whereas complex 2 is a coordination polymer having a one-dimensional linear chain structure. The grid in 1 lies parallel to the crystallographic ab plane and exhibits intra-grid M–M separations of 10.508 × 10.508 Å. Hydrogen bonds hold the cationic chains in 2 together leading to a three-dimensional network structure.     

Two self-interpenetrating magnetic Mn(II) metal-organic frameworks assembled from rigid or flexible tripodal multicarboxylate ligands

Assembly of two tripodal multicarboxylic ligands, namely rigid 3,4-bis(4-carboxyphenyl)-benzoic acid (H₃L¹) and flexible 3,5-bis(4-carboxyphenoxy)-benzoic acid (H₃L²) with MnCl₂ under hydrothermal conditions afforded two distinct metal-organic frameworks (MOFs), {[Mn₃(L¹)₂(H₂O)₄](H₂O)₂}_n (1) and {[Mn₃(L²)₂(H₂O)₄](H₂O)₄}_n (2), respectively. Interestingly, both complexes possess different 3D networks of novel self-interpenetrating prototype, constructing from different 2D [Mn(COO)₂]_n polymeric motifs. Furthermore, the thermal and magnetic properties of 1 and 2 are studied.     

Hydrogen Bonds,Topologies, Energy Frameworks and Solubilities of Five Sorafenib Salts

Sorafenib (Sor) is an oral multi-kinase inhibitor, but its water solubility is very low. To improve its solubility, sorafenib hydrochloride hydrate, sorafenib hydrobromide and sorafenib hydrobromide hydrate were prepared in the mixed solvent of the corresponding acid solution, and tetrahydrofuran (THF). The crystal structures of sorafenib hydrochloride trihydrate (Sor·HCl.3H₂O), 4-(4-{3-[4-chloro-3-(trifluoro-methyl)phenyl]ureido}phenoxy)-2-(N-methylcarbamoyl) pyridinium hydrochloride trihydrate, C₂₁H₁₇ClF₃N₄O₃⁺·Cl⁻.3H₂O (I), sorafenib hydrochloride monohydrate (Sor·HCl.H₂O), C₂₁H₁₇ClF₃N₄O₃⁺·Cl⁻.H₂O (II), its solvated form (sorafenib hydrochloride monohydrate monotetrahydrofuran (Sor·HCl.H₂O.THF), C₂₁H₁₇ClF₃N₄O₃⁺·Cl⁻.H₂O.C₄H₈O (III)), sorafenib hydrobromide (Sor·HBr), 4-(4-{3-[4-chloro-3-(trifluoro-methyl)phenyl]ureido}phenoxy)-2-(N-methylcarbamoyl) pyridinium hydrobromide, C₂₁H₁₇ClF₃N₄O₃⁺·Br⁻ (IV) and sorafenib hydrobromide monohydrate (Sor·HBr.H₂O), C₂₁H₁₇ClF₃N₄O₃⁺·Br⁻.H₂O (V) were analysed. Their hydrogen bond systems and topologies were investigated. The results showed the distinct roles of water molecules in stabilizing their crystal structures. Moreover, (II) and (V) were isomorphous crystal structures with the same space group P2₁/n, and similar unit cell dimensions. The predicted morphologies of these forms based on the BFDH model matched well with experimental morphologies. The energy frameworks showed that (I), and (IV) might have better tabletability than (II) and (V). Moreover, the solubility and dissolution rate data exhibited an improvement in the solubility of these salts compared with the free drug.