Synthesis and Structure of the Np(VII) Complex with Guanidinium,Li[C(NH<Subscript>2</Subscript>)<Subscript>3</Subscript>]<Subscript>2</Subscript>[NpO<Subscript>4</Subscript>(OH)<Subscript>2</Subscript>]·6H<Subscript>2</Subscript>O

The previously unknown Np(VII) compound Li[C(NH₂)₃]₂[NpO₄(OH)₂]·6H₂O (I), containing organic cations, was synthesized and studied by single crystal X-ray diffraction. In contrast to the relatively numerous structurally characterized salts of [NpO₄(OH)₂]^3– anions with Na⁺, K⁺, Rb⁺, and Cs⁺ cations, which were prepared only from strongly alkaline media, crystals of I were isolated from solutions with a very low concentration of OH^– ions (about 0.1 M). The compound is relatively stable in storage in the dry form, but is strongly hygroscopic. In the structure of I, there are two independent Np(VII) atoms with the oxygen surrounding in the form of tetragonal bipyramids. In contrast to the other salts of the [NpO₄(OH)₂]^3– anions with singlecharged alkali metal cations, the C(NH₂) ₃ ⁺ ions and hydrated Li⁺ ions in I interact with the oxygen surrounding of Np(VII) only via hydrogen bonds of types O_w–H···O and N–H···O with the formation of a three-dimensional H-bond network.     

Double Np(V) Malonates with Co(NH3)6 3 + in the Outer Sphere

Light yellow crystalline products of the general formula Co(NH₃)₆(NpO₂L)₂A·xH₂O, where A = Cl, NO₃, or ClO₄, are precipitated with Co(NH₃)₆ ^{3 +} ions from weakly acidic chloride, nitrate, and perchlorate solutions of Np(V), containing up to 0.3 M CH₂(COO)₂ ^{2 -} (L^{2 -}). When only malonate ions are present in the solution, Np(V) precipitates in the form of Co(NH₃)₆(NpO₂L)₂HL·H₂O. These compounds are virtually insoluble in water and have similar X-ray patterns. Unlike oxalate and phthalate solutions, complex neptunyl(V) ion NpO₂L₂ ^{3 -} is not precipitated with Co(NH₃)₆ ^{3 +} ions from malonate media of the above composition.     

Synthesis and structure of crystalline complexes of Np(V) with 1,10-phenanthroline-2,9-dicarboxylic acid. Complexation in solution and spectral studies

Complexes of Np(V) with 1,10-phenanthroline-2,9-dicarboxylic acid, C₁₂H₆N₂(COOH)₂ (H₂PDA), of the compositions [(NpO₂)₂(PDA)(H₂O)₃]·H₂O (I), (NH₄)₂[NpO₂(PDA)]₂·3H₂O (II), and [C(NH₂)₃]₂[NpO₂·(PDA)]₂·4H₂O (III) were synthesized. The Np atoms in the crystal lattices of all the compounds have the pentagonal bipyramidal coordination surrounding, with the [C₁₂H₆N₂(COO)₂]^2? anions acting as chelate-bridging N,O-donor ligands. In the structure of I, two crystallographically independent NpO ₂ ⁺ dioxocations participate in the cation-cation interaction leading to the formation of tetrameric cation-cation complexes. The nonequivalence of the Np atoms is manifested in splitting of the main absorption band of Np(V) in the electronic spectrum of solid compound I. The structures of II and III are based on dimeric anionic complexes [NpO₂(C₁₂H₆N₂(COO)₂)] ₂ ^2? . Only one kind of complexes, NpO₂(PDA)^?, was detected in the solution, and high value of the concentration stability constant β, ～10¹² L mol^?1, is due to tetradentate coordination of the ligand.     

Synthesis and Structure of Mixed-Cation Salts with [PuO<Subscript>4</Subscript>(OH)<Subscript>2</Subscript>]<Superscript>3–</Superscript> Anions

Mixed-cation salts of the composition NaM₂[PuO₄(OH)₂]·4H₂O, where M = Rb (I) and Cs (III), and NaRb₅[PuO₄(OH)₂]₂·6H₂O (II) were synthesized and structurally characterized. The central Pu atom in [PuO₄(OH)₂]^3– anions has oxygen surrounding in the form of a tetragonal bipyramid with oxygen atoms of hydroxide ions in apical positions. The hydrated Na⁺ cations have oxygen surrounding in the form of a distorted octahedron. In the structure of I, there are two independent Rb⁺ cations with 10- and 12-vertex coordination polyhedra (CPs), and in the structure of II, three independent Rb⁺ cations with the 12-, 11-, and 13-vertex CPs. In the structure of III, the Cs⁺ cation has a 12-vertex CP. Frameworks of large Rb⁺ or Cs⁺ cations can be distinguished in the structure. The CPs of the Pu and Na atoms (I, III) sharing a common edge or the isolated CPs of the Pu and Na atoms (II) are incorporated in these frameworks. Hydrogen bonds influence the crystal packing and the geometric characteristics of the [PuO₄(OH)₂]^3– anions.     

Synthesis of New Crystalline Pu(V) Compounds from Solutions: VI. Malonates Co(NH3)6[PuO2C3H2O4]2A · nH2O, A = HCOO, CH3COO, C2H5COO, and C3H3O4

New crystalline compounds of the general composition Co(NH₃)₆[PuO₂L]₂A · nH₂O, where L = CH₂(COO)₂ and A = HCOO, CH₃COO, C₂H₅COO, and HL, were prepared by adding a small excess of Co(NH₃) ₆ ³⁺ ions to freshly prepared neutral Pu(V) malonate solutions containing single-charged organic anions. The complexes are sparingly soluble in water and fairly stable when stored in air; they have a similar structure. Previously unknown double Np(V) malonates Co(NH₃)₆[NpO₂L]₂A · nH₂O, where A = HCOO, CH₃COO, and C₂H₅COO, isostructural with the corresponding Pu(V) compounds, were also prepared. The IR spectra of the new compounds were measured, and their behavior at heating was examined. __________ Translated from Radiokhimiya, Vol. 47, No. 5, 2005, pp. 423–426. Original Russian Text Copyright ? 2005 by Krot, Bessonov, Charushnikova, Grigor'ev, Makarenkov     

Preparation of hydroxyapatite ceramics by hydrothermal hot-pressing method at 300 °C

Hydroxyapatite (HA) ceramics were prepared by a hydrothermal hot-pressing (HHP) method at a low temperature (300 °C). DCPD (CaHPO₄·2H₂O) + Ca(OH)₂, OCP (Ca₈H₂(PO₄)₆·5H₂O) + Ca(OH)₂, DCPD + NH₃·H₂O, OCP + NH₃·H₂O or α-TCP (Ca₃(PO₄)₂) + NH₃·H₂O were used as the precursors. The mixture was treated by HHP under a condition of 300 °C/40 MPa. In sample DCPD + Ca(OH)₂ and OCP + Ca(OH)₂, the HA ceramics obtained showed a porous and homogenous microstructure, and the bending strength were 9.9 MPa and 10.9 MPa, respectively. In sample α-TCP+NH₃·H₂O, rod-like HA crystals produced. When the starting materials were DCPD + NH₃·H₂O, OCP + NH₃·H₂O, the HA particles produced exhibited plate-like features. It appeared that the plate-like HA particles stacked into a lamellar structure. The formation of the lamellar structure leads to a noticeable improvement in fracture property of the HA ceramic. The bending strength and the fracture toughness of the sample prepared from OCP and ammonia water reach 90 MPa and 2.3 MPam^1/2, respectively.     

Synthesis and crystal structure of double Ln(III) malonates with Co(NH3) 6 3+ in the outer sphere

Double Ln(III) malonates of two different compositions crystallize from malonate solutions containing [Co(NH₃)₆]³⁺ ions. Lanthanides of the beginning of the series form compounds of the composition [Co(NH₃)₆][Ln(mal)₂]₃·6H₂O (I) (Ln = La, Ce, Pr, Nd; mal = C₃H₂O^2?), and those of the end of the series form compounds of the composition [Co(NH₃)₆]₂[Ln₃(mal)₇(Hmal)(H₂O)₄]·nH₂O (II) (Ln = Tb, Ho, Er, Tm). Structure I is based on trimeric anionic complexes [Ln₃(mal)₆]^3? linked with each other to form a branched 3D network with [Co(NH₃)₆]³⁺ cations and water molecules accommodated in large voids. The coordination mode of malonate ions in I with the coordination capacity equal to 5 was unknown previously for lanthanide malonate compounds. The Ln(1) atom has the maximum possible for malonate compounds coordination number (CN) 12, and the Ln(2) atom has CN 9. The structure of II consists of anionic chains [Ln₃(mal)₇(Hmal)(H₂O)₄] _n ^3? between which the [Co(NH₃)6]₃₊ cations and water molecules are arranged. One independent malonate ion in the structure is coordinated in the bidentate chelate fashion to the Ln(1) atom, and the other independent chelate-bridging ligand is coordinated in the bidentate fashion to the Ln(2) atom and in the monodentate fashion to the Ln(1) atom. As a result, tetrameric fragments linked in anionic chains are formed in the structure of II. The Ln(1) and Ln(2) atoms have CN 8.     

Partially ordered organic-inorganic nanocomposites in the system UO<Subscript>2</Subscript>SeO<Subscript>4</Subscript>-H<Subscript>2</Subscript>O-NH<Subscript>3</Subscript>(CH<Subscript>2</Subscript>)<Subscript>9</Subscript>NH<Subscript>3</Subscript>

The compound [NH₃(CH₂)₉NH₃]₂[(UO₂)₃(SeO₄)₅(H₂O)₂](H₂O)_x (1) was prepared by isothermal evaporation from aqueous uranyl selenate solutions containing 1,9-diaminononane. A structural study showed that the compound is a partially ordered organic-inorganic nanocomposite. The structural model of the inorganic complex was determined by single crystal X-ray diffraction a = 19.5572(5), c = 47.878(2) Å, V= 15859.1(9) ų, Z= 12; R₁ = 0.1318, wR₂ = 0.3186 for 2808 reflections with |F_o| ≥ 4σ_F). The structure consists of double hydrogen-bonded [(UO₂)₃(SeO₄)₅(H₂O)₂]^2- layers parallel to the (001) plane. The disordered protonated 1,9-diaminononane molecules and water molecules are arranged between the layers. The inorganic layered complex [(UO₂)₃(SeO₄)₅(H₂O)₂]^2- belongs to a new type that was not observed previously in the structures of inorganic and organometallic compounds.     

Synthesis and Crystal Structures of New Layered Uranyl Compounds Containing Dimers [(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>O<Subscript>8</Subscript>] of Edge-Linked Pentagonal Bipyramids

Two new U(VI) compounds, [((CH₃)₂CHNH₃)(CH₃NH₃)][(UO₂)₂(CrO₄)₃] (1) and [CH₃NH₃][(UO₂)· (SO₄)(OH)] (2), were prepared by combining hydrothermal synthesis with isothermal evaporation. Compound 1 crystallizes in the monoclinic system, space group Р2₁, a = 9.3335(19), b = 10.641(2), c = 9.436(2) Å, β = 94.040(4)°. Compound 2 crystallizes in the rhombic system, space group Рbca, a = 11.5951(8), b = 9.2848(6), c = 14.5565(9) Å. The structures of the compounds were solved by the direct methods and refined to R₁ = 0.041 [for 5565 reflections with Fo > 4σ(Fo)] and 0.033 [for 1792 reflections with Fo > 4σ(Fo)] for 1 and 2, respectively. Single crystal measurements were performed at 296 and 100 K for 1 and 2, respectively. The crystal structure of 1 is based on [(UO₂)₂(CrO₄)₃]^2– layers, and that of 2, on [(UO₂)(SO₄)(OH)]^– layers. Both kinds of layers are constructed in accordance with a common principle and are topologically similar. Protonated isopropylamine and methylamine molecules are arranged between the layers in 1, and protonated methylamine molecules, in 2. Compound 1 is the second known example of a U(VI) compound templated with two different organic molecules simultaneously.     

Fabrication of hexagonal MgO and its precursors by a homogeneous precipitation method

The platelet-like and assembled hexagonal Mg₅(CO₃)₄(OH)₂·4H₂O have been prepared via a homogenous precipitation reaction between MgCl₂ and (CH₂)₆N₄. The pH variation of initial solutions results in different nucleation rates, which further leads to various morphology changes from platelets to assembled structures. The similar morphology of magnesium oxide (MgO) samples can be obtained by calcination of their corresponding Mg₅(CO₃)₄(OH)₂·4H₂O samples. In addition, the novel self-assembled MgO crystals with a flowerlike morphology have been obtained by calcination of MgO precursor, which is synthesized via a homogenous precipitation reaction between MgCl₂ and CO(NH₂)₂. A possible self-assembly process of flowerlike crystals is proposed by arresting a series of intermediate morphologies during the shape evolution from the submicrometer-sized petal to the flowerlike morphology.     

Crystal structure and in situ investigation of a mechanochemical synthesized 3D zinc <Emphasis Type="Italic">N</Emphasis>-(phosphonomethyl)glycinate

The mechanochemical synthesis of the zinc N-(phosphonomethyl)glycinate Zn(O₃PCH₂NH₂CH₂CO₂)·H₂O (1) is presented. The structure was solved from powder X-ray diffraction (PXRD) data. In the three-dimensional pillared structure, the Zn atoms are coordinated tetrahedrally. In situ investigations of the reaction process with synchrotron PXRD and Raman spectroscopy reveal a two-step process including the formation of an intermediate.     

Reactive Atmosphere Synthesis of Polymer‐Derived Si–O–C–N Aerogels and Their Cr Adsorption from Aqueous Solutions

Polymer derived ceramic (PDCs) aerogels belonging to the Si–O–C–N system are synthesized by crosslinking a preceramic polymer in a diluted solution followed by supercritical or atmospheric drying and pyrolysis in inert (N₂) or reactive (NH₃/CO₂) atmosphere. Accordingly, aerogels with hierarchical porosity ranging from some microns to few nanometers together with high specific surface area in the range 30–400 m² g^?1 have been obtained. Moreover, their surface contains a broad range of moieties (Si–OH, Si–NH, C=O, etc.) that can interact and bind metal ions thanks to electrostatic interactions. This combination of hierarchical porosity, high SSA, and broad range of chemical functionalities makes these PDCs aerogels interesting candidates for water purification. In this work, SiOC and SiCN aerogels have been tested as adsorbents for Cr(III)/(VI) ions from aqueous solutions with promising results for the SiOC aerogel pyrolyzed in N₂ and the SiCN treated in NH₃. Correlations and similarities among the Cr(VI)/(III) adsorption capacity with the main features of the porous substrates (SSA, N₂ TPV, amount of free C, bulk density, isoelectric point, main IR peaks (Si–OH, OH, NH, C=O, C=C, Si–O, C–N, Si–N) have been investigated by applying the Principal Component Analysis (PCA).

     

2D Electrocatalysts for Converting Earth-Abundant Simple Molecules into Value-Added Commodity Chemicals: Recent Progress and Perspectives

The electrocatalytic conversion of earth-abundant simple molecules into value-added commodity chemicals can transform current chemical production regimes with enormous socioeconomic and environmental benefits. For these applications, 2D electrocatalysts have emerged as a new class of high-performance electrocatalyst with massive forward-looking potential. Recent advances in 2D electrocatalysts are reviewed for emerging applications that utilize naturally existing H₂O, N₂, O₂, Cl⁻ (seawater) and CH₄ (natural gas) as reactants for nitrogen reduction (N₂ → NH₃), two-electron oxygen reduction (O₂ → H₂O₂), chlorine evolution (Cl⁻ → Cl₂), and methane partial oxidation (CH₄ → CH₃OH) reactions to generate NH₃, H₂O₂, Cl₂, and CH₃OH. The unique 2D features and effective approaches that take advantage of such features to create high-performance 2D electrocatalysts are articulated with emphasis. To benefit the readers and expedite future progress, the challenges facing the future development of 2D electrocatalysts for each of the above reactions and the related perspectives are provided.     

Synthesis of co-ordination networks from flexible bis-(4-pyridyl) ligands and cadmium salts.

Crystallisation of flexible dipyridyl ligands with Cd(NO₃)₂·4H₂O, Cd(ClO₄)₂·xH₂O or Cd(NO₃)₂·4H₂O and KSCN gives co-ordination networks of composition [Cd(ClO₄)₂(Py₂C₃H₆)₂(H₂O)₂]·Py₂C₃H₆ 1 (Py₂C₃H₆ =1,3-bis(4-pyridyl)propane); [Cd(ClO₄)₂(Py₂C₂H₄)₃] 2 (Py₂C₂H₄ =1,2-bis(4-pyridyl)ethane); [Cd(NCS)₂(Py₂C₃H₆)] 3; [Cd₂(NO₃)₄(o-C₆H₄(CH₂CH₂4-Py)₂)₄] 4 (o-C₆H₄(CH₂CH₂Py)₂ =1,2-bis[2-(4-pyridyl)ethyl] benzene and [Cd(NO₃)₂(PyCH₂CH₂CH=CHCH₂CH₂Py)₃] 5 (PyCH₂CH₂CH=CHCH₂CH₂Py =1,6-bis(4-pyridyl)hex-3-ene). The compounds were characterised by X-ray single crystal diffraction studies which revealed the presence of different polymeric motifs. Structures 1 and 5 consist of 1-D polymeric chains, structure 4 consists of a 2-D polymeric network and structure 3 is a 3-D polymeric network. None of these exhibit lattice interpenetration. However structure 2 consists of three identical but independent interpenetrating 3-D lattice networks.     

Synthesis and Structure of Mixed-Cation Salts with [NpO<Subscript>4</Subscript>(OH)<Subscript>2</Subscript>]<Superscript>3–</Superscript> Anions

Mixed-cation salts of the general composition NaM₂[NpO₄(OH)₂]·4H₂O, where M = Rb (I, II) and Cs (III), were synthesized and structurally characterized. The compounds differ from each other in the structural organization. The Np central atom in [NpO₄(OH)₂]^3– anions has oxygen surrounding in the form of a tetragonal bipyramid with the O atoms of hydroxide ions in the apical positions. The hydrated Na⁺ cations have oxygen surrounding in the form of a distorted octahedron. In the structure of I, there are two independent Rb cations with 10- and 12-vertex coordination polyhedra, and in the structures of II and III the framework of large cations is built of 12-vertex Rb and Cs polyhedra. The coordination polyhedra of the Np and Na atoms, sharing a common edge (I, III), or chains of the coordination polyhedra of the Np and Na atoms, sharing common vertices (II), are accommodated in the channels of the frameworks. Hydrogen bonds influence the crystal packing and the geometric characteristics of the [NpO₄(OH)₂]^3– anions.     

A Niccolite Structural Multiferroic Metal–Organic Framework Possessing Four Different Types of Bistability in Response to Dielectric and Magnetic Modulation

Multiple switchable physical properties have been demonstrated in one single niccolite structural metal–organic framework, [(CH₃CH₂)₂NH₂][Fe^IIIFe^II(HCOO)₆] ( 1 ), including (i) a reversible ferroelastic phase transition triggered by freezing the disordered (CH₃CH₂)₂NH₂⁺ cations, (ii) a thermally switchable dielectric constant transition accompanied by phase transition, and (iii) thermal and positive magnetic field driven magnetic poles reversal at low temperatures, attributed to different responses of the magnetization of Fe^II and Fe^III sublattices to external stimuli. More interestingly, the exchange anisotropy between the two sublattices can also give rise to tunable positive and negative exchange bias fields. Straightforwardly, such diverse demonstrations of bistability in one single material (depending on the specific tuning way) will provide extra freedom and flexibility for the design of switcher devices.     

Coprecipitation of <Superscript>137</Superscript>Cs, <Superscript>90</Superscript>Sr,and <Superscript>90</Superscript>Y from aqueous and organic solutions with triethylenediamine complexes of <Emphasis Type="Italic">d</Emphasis>-element nitrates

Coprecipitation of ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y with low-soluble complexes of nitrates of d elements (Cu²⁺, Ni²⁺, Zn²⁺) with triethylenediamine [(CH₂-CH₂)₃N₂] from aqueous and aqueous-organic solutions was studied. ¹³⁷Cs and ⁹⁰Sr do not noticeably coprecipitate with precipitates of complexes of Cu²⁺, Ni²⁺, and Zn²⁺ with (CH₂-CH₂)₃N₂ in water; in the process, the radionuclide recovery into the precipitate phase does not exceed 10%. At the same time, the degree of recovery of ⁹⁰Y reaches 65% depending on the experimental conditions. In C₂H₅OH and CH₃CN containing 9 and 5% H₂O, respectively, ¹³⁷Cs, ⁹⁰Sr, and ⁹⁰Y coprecipitate with the complexes to a greater extent, with the degree of recovery varying from 30 to 97% at the molar ratio M²⁺: (CH₂-CH₂)₃N₂ = 1 : 1.     

Sorption of CH<Subscript>3</Subscript><Superscript>131</Superscript>I from water vapor-air medium on porous inorganic sorbents containing triethylenediamine and <Emphasis Type="Italic">d</Emphasis> element nitrates

Sorption of CH₃ ¹³¹I from a water vapor-air medium on porous inorganic sorbents based on silica gel of KSKG grade and containing triethylenediamine (CH₂-CH₂)₃N₂ and d element nitrates was studied. The sorbents prepared by impregnation with (CH₂-CH₂)₃N₂ and Zn, Ni, and Cu nitrates from aqueous solution recover CH₃ ¹³¹I from a water vapor-air flow poorly (degree of recovery <10%). Calcination of the sorbents at temperatures exceeding 250°C does not noticeably affect their sorption power. Heating of the complex Ag(NO₃)(OH)·(CH₂-CH₂)₃N₂H to 160°C causes its exothermic decomposition with a large heat release and formation of metallic silver. Thermal decomposition of the complex of Cu²⁺ with (CH₂-CH₂)₃N₂, synthesized from an aqueous solution at the molar ratio Cu(NO₃)₂: (CH₂-CH₂)₃N₂ = 1: 2, occurs similarly.     

Preparation of new zirconium phosphates by solvothermal reaction

Two types of new zirconium phosphates, [enH₂]Zr(OH)(PO₄)(HPO₄) (en; ethylene diamine) and (NH₄)₅[Zr₃(OH)₉(PO₄)₂(HPO₄)] were prepared under solvothermal condition using diethylene glycol as a solvent and their crystal structures were determined by using single crystal X-ray diffraction data. The former compound has the layer structure similar to that of γ-Zr(PO₄)(H₂PO₄) · 2H₂O, and protonated ethylene diamines were located in the interlayer space. At elevated temperatures, this compound decomposed by releasing protonated ethylene diamines and finally changed to ZrP₂O₇. The interlayer space was soft-chemically inactive unlike α-Zr(HPO₄)₂ · H₂O and γ-Zr(PO₄)(H₂PO₄) · 2H₂O. The later compound has the tunnel structure built up by corner-sharing ZrO₆ octahedra and PO₄ tetrahedra, and NH₄ ⁺ ion was located in the tunnel.