Synthesis, crystal structure, and absorption spectra of 2,2′-bipyridine complexes of benzoates of hexavalent U, Np, and Pu

Complex benzoates [{UO₂(C₁₀N₂H₈)C₆H₅COO}₂O₂], [NpO₂(C₁₀N₂H₈)(C₆H₅COO)₂], and [PuO₂(C₁₀N₂H₈)(C₆H₅COO)₂] (C₁₀N₂H₈ is 2,2??-bipyridine) were synthesized in the form of single crystals, and their structure was determined by X-ray diffraction analysis. The absorption spectra of the crystalline U(VI), Np(VI), and Pu(VI) complexes were measured and analyzed.     

Synthesis and study of complexes of Pu(V) and Np(V) propionates with α,α′-bipyridine

New complexes of Np(V) and Pu(V) with α,α′-bipyridine of the composition AnO₂(bipy) · OOCC₂H₅·H₂O (An = Np, Pu) were synthesized. They are isostructural to each other; however, they differ essentially in the structure and characteristics from the similar complexes of An(V) formates and acetates. The new compounds were characterized by powder X-ray diffraction, thermal analysis, electronic absorption spectroscopy, and IR spectroscopy.     

Complexation of hexavalent U,Np, and Pu with cyclopropanecarboxylate anions. Crystal structure of the uranyl complexes {[UO2(bipy)(cpc)]2O2} and [UO2(cpc)2(H2O)2] (bipy = 2,2′-Bipyridine,cpc− = cyclopropanecarboxylate anion)

The complexation of hexavalent U, Np, and Pu with cyclopropanecarboxylate anions, cpc^?, in aqueous solutions was studied. The stepwise concentration stability constants of the complexes PuO₂(cpc) _i ^2?i (i = 1, 2, 3) are as follows: logK _1,2,3 = 2.63 ± 0.20, 1.61 ± 0.20, 1.43 ± 0.20, respectively; the overall concentration stability constant of the complex PuO₂(cpc) ₃ ^? is logβ₃ = 5.67 ± 0.60. The complexing properties of the cpc^? anion are very close to those of butyrate and isobutyrate anions. Two crystalline uranyl compounds were synthesized: {[UO₂(bipy)(cpc)]₂O₂} (bipy = 2,2′-bipyridine) and [UO₂(cpc)₂(H₂O)₂]. The specific feature of the first complex is that it contains peroxide ion. Its appearance may be due to the formation of the cationic moiety via hydrolytic uranyl dimer. The second compound forms a 3D structure, with the complexes linked via hydrogen bonds.     

Interaction of An(VI) (An = U, Np, Pu) and Np(V) with 2,3-pyridinedicarboxylic (quinolinic) acid (H2Quin): Complexation in aqueous solutions, synthesis and structure of the complexes [UO2(HQuin)2], [(NpO2)2(HQuin)2(C6H4NO3)2]·2H2O, and [PuO2Quin(H2O)]

Complexation of An(VI) (An = U, Np, Pu), and Np(V) with 2,3-pyridinedicarboxylic (quinolinic, H₂Quin) acid in aqueous solutions was studied. Np(V) can form 1: 1 and 1: 2 complexes, and An(VI), also 1: 3 complexes (at pH ? 6 and [H₂Quin] ? 0.1 M). Quinolinate ion can coordinate to actinide(VI) and (V) ions in solutions in different modes. The apparent stability constants of the complexes in a wide pH range and the concentration stability constants of the An(VI) complexes were measured. In the series from Pu(VI) to U(VI), the stability of the complexes slightly increases. Crystalline complexes [UO₂(HQuin)₂], [(NpO₂)₂(HQuin)₂(HL)₂]·2H₂O (HL is N-protonated 2-hydroxypyridine-3-carboxylic acid anion), and [PuO₂Quin(H₂O)] were synthesized, and their structures were determined by single crystal X-ray diffraction. Different types of coordination of quinolinate ions to actinide ions are also observed in the crystalline complexes.     

Interaction of U(VI), Np(VI), Pu(VI), and Np(V) with benzenetricarboxylic acids: Complexation in aqueous solutions, synthesis, and crystal structure of uranyl complexes [UO2(H2O)2{C6H3(COO)2(COOH)}]2·2H2O and [(UO2)3(H2O)4{C6H3(COO)3}2]

The complexation of U(VI), Np(VI), and Pu(VI) and of Np(V) with 1,2,3- and 1,2,4-benzenetricarboxylic acids (BTC) in aqueous solutions was studied in wide ranges of pH and actinyl ion concentrations. The compositions of the forming hexavalent actinide complexes were determined. Their apparent stability constants β₁′ depend on pH of the solution: in the pH range 2–4, logβ₁′ from 2 to 4 for the complexes of U(VI), Np(VI), and Pu(VI) with 1,2,3-BTC and from 1.5 to 3.5 for the complexes with 1,2,4-BTC. For Np(V), the β₁′ values are close with both acids, and at equal pH values the Np(V) complexes are less stable than the An(VI) complexes (An = U, Np, Pu). With an increase in pH from ～3 to 6.2–6.9, logβ₁′ of the Np(V) complexes increases approximately from 0.5 to 3. Solid U(VI) complexes with 1,2,3- and 1,2,4-benzenetricarboxylic acids were synthesized by the hydrothermal method, their crystal structure was determined, and the IR spectra were examined.     

Crystal Structure of An(VI) Complexes with Succinate Anions, [PuO2(C4H4O4)(H2O)] and Cs2[(AnO2)2(C4H4O4)3]·H2O (An = U,Np, Pu)

Radiochemistry - Actinide(VI) complexes with succinate anions [PuO2(succ)(H2O)] and Cs2[(AnO2)2(succ)3]·H2O (An = U, Np, Pu), where succ = [C4H4O4]2 ?, were synthesized and studied by...     

Synthesis and crystal structure of cesium actinide(VI) tricarbonate complexes Cs4AnO<Subscript>2</Subscript>(CO<Subscript>3</Subscript>)<Subscript>3</Subscript>·6H<Subscript>2</Subscript>O,An(VI) = U,Np, Pu

Tricarbonate complexes of hexavalent U, Np, and Pu with outer-sphere cesium cations, Cs₄AnO₂·(CO₃)₃·6H₂O, were synthesized and studied by single crystal X-ray diffraction analysis. Crystals of Cs₄AnO₂·(CO₃)₃·6H₂O consist of [AnO₂(CO₃)₃]^4– complex anions and hydrated Cs⁺ cations. The coordination polyhedron (CP) of An(VI) atoms is a distorted hexagonal bipyramid with three CO ₃ ^2– anions arranged in the equatorial plane. Four independent Cs+ cations have the coordination surrounding in the form of 11-, 10-, and 9-vertex polyhedra formed by the O atoms of CO ₃ ^2– anions, AnO ₂ ²⁺ cations, and water molecules. Six crystallographically independent water molecules in the structure of Cs₄AnO₂(CO₃)₃·6H₂O form a three-dimensional system of hydrogen bonds in which the O atoms of carbonate ions and water molecules act as proton acceptors. The “yl” oxygen atoms of AnO ₂ ²⁺ cations are not involved in hydrogen bonding. The lengths of the An–O_carb bonds in the equator of the U, Np, and Pu hexagonal bipyramids are noticeably influenced by incorporation of the O atoms of the CO ₃ ^2– anions in the coordination polyhedra of Cs⁺ ions and by involvement of these atoms in hydrogen bonding.     

Interpenetrating covalent and noncovalent nets in the crystal structures of [M(4,4′-bipyridine)2(NO3)2]·3C10H8 (M = Co,Ni)

The synthesis and crystal structures of [M(4,4′-bipyridine)₂(NO₃)₂]·3naphthalene (M = Co, 1·3naphthalene; Ni, 2·3naphthalene) are reported. 1·3naphthalene and 2·3naphthalene are isostructural and represent rare examples of interpenetrating planar networks that are chemically and topologically different. It appears that the networks coexist because the (4,4) topology of the cobalt and nickel square grids is complementary to the (6,3) topology of the naphthalene honeycomb network, resulting in an inclined interpenetrated 3D architecture. This observation is discussed in the context of rational design strategies for hybrid solids.     

Crystal structure of new complexes of Np(V) and Pu(V) propionates with 2,2’-bipyridine, [AnO2(C10H8N2)(OOCC2H5)(H2O)]

The crystal structure of new complexes of Np(V) and Pu(V) propionates with 2,2’-bipyridine (Bipy) was studied. The compounds are isostructural. Their crystals are built of electrically neutral complexes [AnO₂ (C₁₀H₈N₂)(OOCC₂H₅)(H₂O)] (An = Np, Pu). The equatorial surrounding of the actinyl(V) group consists of two nitrogen atoms of Bipy, two oxygen atoms of the propionateion, and oxygen atom of the water molecule. The coordination surrounding of the An(V) atom is a pentagonal bipyramid. In going from Np(V) to Pu(V), the actinide contraction is manifested in a regular decrease in the bond lengths in the pentagonal bipyramids. The water molecule in the An(V) coordination sphere forms strong hydrogen bonds with “yl” oxygen atoms of the adjacent complexes [AnO₂(Bipy)(OOCC2H₅)(H₂O)]. As a result, the complexes in the crystal are bound in infinite chains oriented along the [100] direction.     

Synthesis,crystal structure,photoluminescence and dielectric properties of a new organic–inorganic compound: tetrachlorocadmate (II) 2.2′-bipyridinium

Single crystals of a new organic–inorganic compound (C₁₀H₁₀N₂) CdCl₄ were grown by the slow evaporation technique and characterized by X-ray diffraction, Hirshfeld surface, Infrared absorption, Solid state ¹³C NMR, photoluminescence (PL) properties, differential scanning calorimetry (DSC) and dielectric measurements. The title compound belongs to the monoclinic space group P2₁/c with the following unit cell parameters: a?=?7.29420(1), b?=?13.9206(3), c?=?14.3880(3) Å, β?=?100.247(2)° and Z?=?4. The structure can be described by the alternation of two different cationic-anionic layers. It consists of isolated [CdCl₄]^2? tetrahedral anions and 2.2′ bipyridinium (C₁₀H₁₀N₂)²⁺ cations, which are connected via N–H?Cl hydrogen bonds. The Hirshfeld surface analysis was conducted to investigate intermolecular interactions and associated 2D fingerprint plots, revealing the relative contribution of these interactions in the crystal structure quantitatively. Furthermore, the room temperature infrared (IR) spectrum of the title compound was recorded and analyzed on the basis of detailed vibrational studies found in the literature; the detailed assignment confirms the presence of the organic groups. Solid state ¹³C NMR spectrum shows four signals, confirming the solid state structure determined by X-ray diffraction. Besides, photoluminescence measurements showed a strong emission line at 2.95 eV associated with radiative recombinations of excitons confined within the [CdCl₄]^2? which were investigated at room temperature. Finally, the thermal analysis studies were performed, and phase transition was found in the temperature range between 300 and 550 K, while the electrical measurements were performed to discuss the phase-transition mechanism.     

Synthesis and characterization of lanthanide(III) complexes with a mesogenic Schiff-base,N,N′-di-(4-decyloxysalicylidene)-2′,6′-diaminopyridine

A mesogenic Schiff-base, N,N′-di-(4-decyloxysalicylidene)-2′,6′-diaminopyridine, H₂ddsdp (abbreviated as H₂L³) that exhibits nematic mesophase, was synthesized and its structure studied by elemental analysis, mass spectrometry, NMR & IR spectral techniques. The Schiff-base, H₂L³, upon condensation with hydrated lanthanide(III) nitrates, yields Ln^III complexes of the general composition [Ln₂(L³H₂)₃(NO₃)₄](NO₃)₂, where Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy and Ho. Among the metal complexes, only that of Ho^III is found to be mesogenic with smectic-X and nematic phases. The IR and NMR spectral data imply a bi-dentate bonding of the Schiff-base in its zwitterionic form (as L³H₂) to the Ln^III ions through two phenolate oxygens, rendering the overall geometry of the complexes to seven-coordinated polyhedron, possibly distorted mono-capped octahedron.     

Synthesis,crystal structure,and properties of new actinide(VI) arsenates (H<Subscript>3</Subscript>O)[(AnO<Subscript>2</Subscript>)(AsO<Subscript>4</Subscript>)]·3H<Subscript>2</Subscript>O (An = U,Np, Pu)

Previously unknown arsenates of hexavalent U, Np, and Pu, (H₃O)[(UO₂)(AsO₄)]·3H₂O (I), (H₃O)· [(NpO₂)(AsO₄)]·3H₂O (II), and (H₃O)[(PuO₂)(AsO₄)]·3H₂O (III), were synthesized under hydrothermal conditions. The crystal structure of the compounds was determined, and their absorption spectra were measured. The compounds crystallize in tetragonal space group P4/nmm.     

Crystal structure of mixed-valent Np(IV)/Np(V) chloride, [Np(NpO2)6(H2O)8(OH)Cl9]·H2O

A new mixed-valent Np(IV)/Np(V) chloride, [Np(NpO₂)₆(H₂O)₈(OH)Cl₉]·H₂O, was synthesized, and its crystal structure was determined. The crystals consist of NpO ₂ ⁺ and Np⁴⁺ cations, of Cl^? and OH^? anions, of coordination-bonded water molecules, and of water molecules of crystallization. The Np(V) atom, Np(1), has pentagonal bipyramidal coordination surrounding with O atoms in the apical position and with the equatorial plane formed by three Cl^? anions, O atom of the adjacent NpO ₂ ⁺ cation, and O atom of water molecule. The mutual coordination of the neptunyl(V) ions, cation-cation (CC) interaction, links the Np(1) coordination polyhedra via common vertices into rings around sixfold axes, with the Np(V)?Np(V) distance in these fragments of 4.276 Å. The ring fragments are linked with each other via common equatorial edges of the bipyramids into layers perpendicular to c-axis. The Np(IV) atom, Np(2), has coordination surrounding in the form of tricapped trigonal prism (CN 9) with the tetragonal lateral faces formed by the O atoms of the NpO ₂ ⁺ cations and the capping positions occupied by the O atoms of two water molecules and one hydroxy group. The Np(2) atoms act in CC interactions as coordination center for six NpO ₂ ⁺ ions, with the Np(IV)?Np(V) distance of 4.183 Å. The Np(2) polyhedra are arranged in the crystal between layers of the Np(1) coordination polyhedra, linking them with each other.     

Synthesis and crystal structure of a new Np(V) oxalate, Na4(NpO2)2(C2O4)3·6H2O

A new oxalate complex, Na₄(NpO₂)₂(C₂O₄)₃·6H₂O, with the Np:C₂O₄ ratio of 2:3 was synthesized and studied by single crystal X-ray diffraction. In the crystal, the NpO ₂ ⁺ cations and oxalate anions are bound in open networks [(NpO₂)₂(C₂O₄)₃] _n ^4n- parallel to the bc plane. The Na(1) cations are accommodated in large voids of the neptunyl oxalate networks with the formation of crimped mixed-cation layers of the composition [Na₂(NpO₂)₂(C₂O₄)₃] _n ^2n- . The negative charge of the layers is compensated by the Na(2) cations arranged between the layers. The Np atoms have a pentagonal bipyramidal coordination surrounding with the equatorial plane formed by the oxygen atoms of three oxalate anions. The structure contains tridentate-bridging and tetradentate-bridging oxalate anions.     

Synthesis and Study of Uranium-Containing Aluminum Compounds Al[BVUO6]2[OH]·nH2O (BV = P,As)

A procedure was developed for preparing aluminum hydroxouranophosphate and hydroxourano- arsenate. The structural features and thermal decomposition pathways of the compounds were studied by X-ray diffraction, IR spectroscopy, and thermal analysis.     

Crystallization of salts M3[NpO4(OH)2]·nH2O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures. Synthesis and structure of a new Np(VII) compound, Na3[NpO4(OH)2]·6H2O

Precipitation of salts M₃[NpO₄(OH)₂]·nH₂O (M = Na, K, Rb, Cs) from concentrated alkali solutions at low temperatures (about ?10°C) was studied. From solutions with [OH^?] > 9.5 M, these compounds are isolated as coarse black crystals in high yield without impurity of other phases. The K, Rb, and Cs salts crystallize in the form of the previously studied compounds K₃[NpO₄(OH)₂]·2H₂O and M₃[NpO₄(OH)₂]·3H₂O (M = Rb, Cs). In the case of Na, a new hydrate Na₃[NpO₄(OH)₂]·6H₂O was obtained, and its crystal structure was determined. Crystals of the hexahydrate consist of centrosymmetrical tetragonal-bipyramidal anions [NpO₄(OH)₂]^3?, crystallographically independent Na(1) and Na(2) cations, and water molecules. The coordination surrounding of the Np atom is characterized by noticeable difference (Δ = 0.0203 Å) in the Np-O bond lengths in the equatorial plane of the bipyramid. The [NpO₄(OH)₂]^3? anions are combined with the Na(2) cations to form infinite chains [Na(2)NpO₄(OH)₂(H₂O)₂]^2? in such a manner that the lateral edges of the anion are simultaneously the lateral edges of the Na(2) coordination polyhedron. Incorporation of one of the two crystallographically independent O atoms of the NpO₄ group into the Na(2) coordination surrounding is responsible for a noticeable difference in the Np-O bond lengths in the equator of the [NpO₄(OH)₂]^3? anion. The types of hydrogen bonding in the structures of Na3[NpO₄(OH)₂]·nH₂O (n = 0, 2, 4, 6) are compared.     

Synthesis and structure of Cs3[UO2(CH3COO)3]2(NCS)·H2O

The compound Cs₃[UO₂(CH₃COO)₃]₂(NCS)·H₂O (I) was synthesized and studied by IR spectroscopy and single crystal X-ray diffraction. Compound I crystallizes in the monoclinic system with the following unit cell parameters: a = 7.8286(9), b = 19.892(2), c = 20.050(2) Å, β = 94.527(2)°, space group P2₁/c, Z = 4, R = 0.0387. The uranium-containing structural units in crystals of I are mononuclear complexes [UO₂(CH₃COO)₃]^? belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?) of uranyl complexes.     

Synthesis,structure and photocatalysis properties of two 3D Isostructural Ln (Ⅲ)-MOFs based 2,6-Pyridinedicarboxylic acid

Two new 3 D metal-organic frameworks(MOFs) named [Pr_2(PDA)3-3 H_2 O]-H_2 O(1) and[Nd_2(PDA)3-3 H_2 O] H_2 O(_2) [2,6-Pyridinedicarboxylic acid(H2 PDA)] were synthesized by solvothermal method. They were characterized by elemental analyses(EA), infrared spectroscopy(FT-IR), thermogravimetric analysis(TG), photocatalysis performance and single crystal X-ray diffraction studies(XRD).The XRD analysis indicated that MOFs(1) and(2) both belong to the monoclinic system with space group P2(1)/C. The structural model were drawn by the diamond software, and the structure revel that MOFs(1) and(2) adopt three-dimensional(3 D) frameworks constructed by cross-linking of one-dimensional(1 D) infinite chain secondary building unit(SBU) by 2,6-Pyridinedicarboxylic acid and hydrogen bond as linker. These frameworks feature channels inside which coordinated H_20 solvent molecules are located. Thermogravimetric analysis showed that both MOFs are thermally stable, the photocatalytic evaluation showed the materials have a good prospect in degration methylene blue. As for complex1, the decomposition efficiency of Methylene blue was about 91.08% after 130 min and the complex 2 reach 90.45% after 160 min under the sun light.     

Synthesis of poly(ethylene glycol) functionalized MWNTs and their inclusion complexes with α-cyclodextrin

Poly(ethylene glycol) (PEG) functionalized multiwalled carbon nanotubes (MWNTs), prepared by coupling of isocyanate-decorated MWNTs with PEG of different molecular weights (M _n = 400, 1000, 2000, and 4000 g/mol), were used to form inclusion complexes (ICs) with α-cyclodextrin (α-CD) through the grafted PEG chains being threaded with α-CD rings in aqueous solution. The FTIR, TGA, UV-Vis, and scanning electron microscopy (SEM) techniques were employed to characterize the formed ICs. The ICs formation time was monitored by UV-Vis spectroscopy, and the results indicated that the inclusion interaction between MWNT surface anchored PEG chains and α-CD was dependent on the molecular weight of PEG. The grafted PEG with molecular weights of 4000 and 2000 g/mol, respectively, can form ICs with α-CD, while the grafted PEG with molecular weights of 1000 and 400 g/mol, respectively, are difficult to form ICs with α-CD due to the steric hindrance from nanotubes. The stoichiometry value determined by TGA indicated that the ratio of ethylene glycol (EG) unit to α-CD in the resulted ICs was about 15:1. In addition, the morphology of the ICs was observed by SEM and transmission electron microscopy (TEM).