X-ray powder diffraction and IR study of NaMg(H2O)2[BP2O8]·H2O and NH4Mg(H2O)2[BP2O8]·H2O

NaMg(H₂O)₂[BP₂O₈]·H₂O was prepared by hydrothermal synthesis and was characterized by X-ray powder difraction and IR method. The title compound was synthesized from MgCl₂·6H₂O, NaBO₃·4H₂O, and (NH₄)₂HPO₄ with variable molar ratios using hydrothermal method by heating at 165 °C for 3 days. The X-ray powder diffraction data was indexed in hexagonal system, the unit cell parameters were found to be as a = 9.428, c = 15.82 Å, Z = 4 and the space group is P6₁22. It is isostructural with M^lM^ll(H₂O)[BP₂O₈] type compounds where M^l = Na, K; M^ll = Mg, Mn, Fe, Co, Ni and Zn. In addition NH₄Mg(H₂O)₂[BP₂O₈]·H₂O was also synthesized the first time in this research. Its unit cell parameters and hkl values were in good agreement with the sodium magnesium compound. The unit cell parameters are a = 9.529, c = 15.736 Å. The indexed X-ray powder diffraction data of both compounds which were not reported in the literature is presented in this work. The IR data of NaMg(H₂O)₂[BP₂O₈]·H₂O is also reported.     

Complexes with substituted 2,5-dihydroxy-p-benzoquinones: The inclusion compounds [Y(H2O)3]2 (C6Cl2O4)3·6.6H2O and [Y(H2O)3]2 (C6Br2O4)3·6H2O

Single crystal of [Y(H₂O)₃]₂ (C₆Br₂O₄)₃·6H₂O and [Y(H₂O)₃]₂ (C₆Cl₂O₄)₃·6.6H₂O were grown in aqueous silicagel. The compounds are in principle isostructural. In Y chloranilate one additional water site is occupied as verified by X-ray single crystal structure analysis. Y³⁺ is nine-coordinated by three water molecules and six oxygen atoms of the bischelating (C₆X₂O₄)²⁻ ions (XCl, Br). The coordination polyhedron is an only slightly distorted tri-capped trigonal prism. The connection of Y³⁺ with the dianions leads to infinite, corrugated layers. The layer stacking yields cage-like cavities in which water molecules are accomodated. Hydrogen bonds interlink adjacent layers. Further hydrogen bonds involve the entrapped water molecules. DSC measurements indicated a complicated dehydration process which caused right at the start destruction of the single crystals.     

Cobalt-mediated synthesis of 2-(4-pyridyl)benzimidazole. x-ray structures of Co[2-(4-pyridyl)benzimidazole]2(H2O)2(NO3)2 and [Co(isonicotinate)(4-pyridiniumcarboxylate)(H2O)(NO3)]∞

We have observed an unusual example of cobalt-mediated cyclization of 4-pyridinecarboxaldehyde and 2-nitroaniline to afford 2-(4-pyridyl)benzimidazole under hydro(solvo)thermal conditions. Reaction of Co(NO₃)₂·6H₂O with 4-pyridinecarboxaldehyde and 2-nitroaniline in ethanol at 120°C gave a cobalt(II) coordination compound, Co[2-(4-pyridyl)benzimidazole]₂(H₂O)₂(NO₃)₂, 1. In contrast, when the hydro(solvo)thermal reaction was carried out between Co(NO₃)₂·6H₂O and isonicotinic acid in the presence of 2-nitroaniline at 110°C, a one-dimensional Co(II) coordination polymer with the formula of [Co(isonicotinate)(4-pyridiniumcarboxylate)(H₂O)(NO₃)]_∞, 2, resulted. The X-ray single crystal structures of both 1 and 2 are described. Interestingly, the isonicotinic acid in 2 exists as a 4-pyridiniumcarboxylate tautomer, and the pyridinium hydrogen atom forms a very strong hydrogen bond to the carboxylate oxygen of the 4-pyridiniumcarboxylate on an adjacent metal center. 1 forms a three-dimensional polymeric network through hydrogen bonding interactions, while 2 exists as a 2-D bilayer polymeric network through hydrogen bonding interactions.     

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 and Study of Sr[HSiUO6]2·2H2O and Ba[HSiUO6]2·2H2O

Uranosilicates of the general formula M^{I I}[HSiUO₆]₂·2H₂O (M^{I I} = Sr, Ba) were prepared by hydrothermal synthesis. Previously unknown intermediate crystal hydrates were separated and studied by X-ray diffraction (XRD), IR spectroscopy, and thermal analysis. Polymorphic transitions -Sr[HSiUO₆]₂ -Sr[HSiUO₆]₂ and -Ba[HSiUO₆]₂ -Ba[HSiUO₆]₂ were revealed at 700 and 780°C, respectively.     

Novel self-assembled decavanadate clusters forming 1D molecular chains and 2D molecular arrays: [HMTA-H···H2O][HMTA-CH2OH][H3V10O28{Na(H2O)4}]·4H2O and [Na2(H2O)10] [H3V10O28 {Na(H2O)2}]·3H2O

Two novel materials, [HMTA-H··H₂O] [HMTA-CH₂OH] [H₃V₁₀O₂₈[Na(H₂O)₄}]·4H₂O, 1 and [Na₂(H₂O)₁₀][H₃V₁₀O₂₈[Na(H₂O)₂}]·3H₂O, 2 containing decavanadate clusters interconnected through hydrated sodium cations forming 1D molecular chains and 2D molecular arrays have been self-assembled from acidified, aqueous vanadate solution in the presence of organic bases, hexamethylenetetramine and 1,3,5-triazine respectively.     

Synthesis and structure of actinide(VII) compounds Rb3NpO4(OH)2·3H2O and Rb3PuO4(OH)2·3H2O

Actinide(VII) salts Rb₃[NpO₄(OH)₂]·3H₂O (I) and Rb₃[PuO₄(OH)₂]·3H₂O (II) were prepared as single crystals and examined by X-ray diffraction. The compounds are isostructural and crystallize in the monoclinic system, space group C2/c, Z = 4; unit cell parameters: a = 12.1544(3), b = 10.9942(2), c = 7.789(2) ?, ?? = 91.0930(11)° for I and a = 12.1254(3), b = 10.9506(2), c = 7.7699(2) ?, ?? = 90.8253(12)° for II. The main structural elements of I and II are centrosymmetrical anions [AnO₄(OH)₂]^3? forming together with water molecules, owing to strong hydrogen bonding, chains oriented along [101]. In [AnO₄(OH)₂]^3? anions, the central An(VII) atom has a tetragonal-bipyramidal oxygen surrounding. The An-O(OH) interatomic distances decrease in going from I to II owing to actinide contraction by a factor of ??2 more strongly than the An-O bond lengths in the equatorial planes of the bipyramids. The previously studied structure of Cs₃[NpO₄(OH)₂]·3H₂O (III) was refined.     

Mechanism of decomposition of UO2(NO3)2·6H2O + Fe(NO3)3·9H2O mixture under the action of microwave radiation

Products of decomposition of the UO₂(NO₃)₂·6H₂O + Fe(NO₃)₃·9H₂O mixture under the action of microwave radiation (MWR) were studied by thermal gravimetric, X-ray phase, and chemical analyses. The results obtained were compared to the published data for various U and Fe compounds. The final products of decomposition of the UO₂(NO₃)₂·6H₂O + Fe(NO₃)₃·9H₂O mixture under the action of MWR for 3?C5 min (the maximal temperature of the process, equal to 140?C150°, is attained within 2?C3 min of irradiation), apart from gaseous products, are UO₂(OH)NO₃, UO₃, and Fe₂O₃. The action of MWR on the UO₂(NO₃)₂·6H₂O + Fe(NO₃)₃·9H₂O mixture under the examined conditions does not lead to the formation of uranyl ferrite.     

An X-ray diffraction study of Rb[UO2(SeO4)F]·H2O

An X-ray diffraction study of Rb[UO₂(SeO₄)F]·H₂O (I) was performed. The compound crystallizes in the rhombic system with the following unit cell parameters: a = 8.4753(6), b = 13.5234(9), c = 13.5296(9) Å, space group Pnma, Z = 8, V = 1550.7(2) ų; R = 0.0248. The principal structural units of crystals of I are [UO₂(SeO₄)F]^? layers belonging to crystal-chemical group AT³M² (A = UO ₂ ²⁺ , T³ = SeO ₄ ^2? , M² = F^?) of uranyl complexes. The uranium-containing layered units are combined via electrostatic interaction with Rb cations and via a system of hydrogen bonds involving outer-sphere water molecules.     

Synthesis and characterization of a new organic sulphate, [2,3-(CH3)2C6H3NH3]HSO4·H2O

Crystals of a new hybrid compound C₈H₁₂N⁺, HSO₄^?·H₂O were synthesized in aqueous solution and characterized by X-ray diffraction and IR absorption spectroscopy. This compound crystallizes in the orthorhombic non-centrosymmetrical space group P2₁2₁2₁ and an unit cell with a = 5.74(2) Å, b = 9.17(2) Å, c = 21.34(4) Å, V = 1124(6) Å³, and Z = 4. Its crystal structure is a packing of alternated inorganic and organic layers parallel to (a,b) planes. The different components are connected by a bi-dimensional network of strong OH…O and NH…O hydrogen bonds. Then, in order to detect phase transitions and watch changes in the conductivity behaviour, investigations by DTA–TG and differential scanning calorimetry (DSC) and electrical conductivity measurements were carried out.     

A single crystal X-ray diffraction study of Na4(UO2)4(i-C4H9COO)11(NO3)·3H2O

Synthesis and the results of IR and single crystal X-ray diffraction study of Na₄(UO₂)₄(i-C₄H₉COO)₁₁·(NO₃)·3H₂O are reported. The crystals are monoclinic; the unit cell parameters at 100 K are as follows: a = 13.697(2), b = 20.285(3), c = 15.991(3) Å, β = 103.760(3)°, space group P2₁, Z = 2, R = 0.0650. The uraniumcontaining structural units are mononuclear moieties [UO₂(i-C₄H₉COO)₃]^? and [UO₂(NO₃)(i-C₄H₉COO)₂]^?, belonging to crystal-chemical group AB ₃ ⁰¹ (A = UO ₂ ²⁺ , B⁰¹ = i-C₄H₉COO^? and NO ₃ ^? ) of uranyl complexes. The IR data are consistent with the results of the single crystal X-ray diffraction study. The influence of the carboxylate ligand volume on the structure of Na[UO₂L₃]·nH₂O crystals (L = acetate, n-butyrate, isovalerate ion) is analyzed.     

Photocatalytic Properties of the MgHPO4·3H2O and MgKPO4·6H2O Phosphates

Inorganic Materials - Magnesium double phosphates, MgHPO4·3H2O and MgKPO4·6H2O, isostructural with the minerals newberyite and struvite-K have been synthesized in powder form via...     

Conductivity of (NH4)3[CrMo6O24H6]·7H2O Treated by Nd Chemistry-Heated Diffused Permeation

Rare earth co-permeation of (N H4)3 [CrMo6 O24 H6]·7H2O was reported and the conductivity of (N H4)3 [CrMo6O24 H6]was improved by 6.734× 109 times. X-ray fluorescence spectrometry (XRF), thermogravimetry-differential thermal sample. Experimental results showed that Nd could be permeated into the body of this sample and the XRD patterns showed great difference between (NH4)3[CrMo6O24H6]·7H2O and permeated sample. The structure of (NH4)3[CrMo6O24H6]·7H2O was destroyed and new compound MoN perhaps formed.     

Mixed-Cation Molybdate Complex of Neptunium(V), Li2Na[NpO2(MoO4)2]·4H2O

Radiochemistry - A new mixed-cation complex Li2Na[NpO2(MoO4)2]·4H2O with NpO2+ : MoO42– = 1 : 2 has been synthesized and structurally characterized. The coordination environment of Np(V)...     

Synthesis of Double Uranyl Phthalates of the M4[(UO2)4(μ3-O)2(C6H4C2O4)4] ⋅ nH2O Type with M = NH4, K, and Cs. Crystal Structure of K4[(UO2)4O2(C6H4C2O4)4] ⋅ 3H2O

Double U(VI) phthalates with NH ₄ ⁺ , K⁺, and Cs⁺ ions in the outer sphere were synthesized. The X-ray phase analysis shows that their structures are similar. Single crystals were prepared and the structure of K₄[(UO₂)₄(μ₃-O)₂(C₆H₄C₂O₄)₄] ? 3H₂O was solved. In the [(UO₂)₄O₂(C₆H₄C₂O₄)₄]^4? anions forming the main structural motif, each bridging oxygen atom μ₃-O combines one pentagonal and two hexagonal bipyramids, which, in turn, are combined in centrosymmetrical tetramers. The phthalate ions have coordination capacity equal to 3; each ligand coordinates U(1) in the bidentate fashion via one carboxy group and U(2) in the bidentate fashion to form a planar seven-membered chelate ring.     

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.     

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.     

Framework materials containing polyoxovanadates as building units: synthesis and characterization of (N2H5)2[M3(H2O)12V18O42(EO4)]·24H2O (M = Mg,Ca) and Li6[Mn3(H2O)12V18O42(EO4)]·24H2O (E = V,S)

The reaction of an aqueous solution of lithium vanadate with hydrazinium sulfate results in a dark-colored solution that reacts with magnesium sulfate heptahydrate, calcium sulfate dihydrate, and manganese(II) chloride tetrahydrate to yield single crystals of (N₂H₅)₂[M₃(H₂O)₁₂V₁₈O₄₂(EO₄)]·24H₂O (M = Mg, Ca) and Li₆[Mn₃(H₂O)₁₂V₁₈O₄₂(EO₄)]·24H₂O (E = V, S), respectively. The crystal structures of the new solids consist of interpenetrating three-dimensional networks of {V₁₈O₄₂(EO₄)} clusters interlinked via bridging {M(H₂O)₄} (M = Mg, Ca, Mn) groups. The voids in these structures are occupied by lattice water and ion exchangeable cations.     

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.     

Influence of hydrothermal treatment on the microstructure and oxidation resistance of a Zn4B2O7·H2O (4ZnO·B2O3·H2O) coating for C/C composites

Antioxidant modification for C/C composites by in situ hydrothermal synthesise at 140 °C of a 4ZnO·B₂O₃·H₂O crystallite coating has been successfully achieved. The influence of hydrothermal time on the phase composition, microstructure of the as-prepared Zn₄B₂O₇·H₂O (4ZnO·B₂O₃·H₂O), and its antioxidant modification for C/C composites were investigated. Samples were characterised by XRD, SEM, isothermal oxidation test and TG-DSC. Results show that, 4ZnO·B₂O₃·H₂O crystalline coating is achieved on the surface of C/C composites after the hydrothermal treatment at 140 °C for time in the range of 2–12 h. A smooth and crack-free 4ZnO·B₂O₃·H₂O layer can be obtained when the hydrothermal time reaches 8 h. Isothermal oxidation test demonstrates that the oxidation resistance of C/C composites is improved. The as-modified composites exhibit only 1.52 g·cm^?2 weight loss after oxidation at 600 °C for 15 h, while the non-modified one shows a 6.57 g·cm^?2 weight loss after only 10 h oxidation. For the uncoated C/C composite the oxidation rate is approximately linear with time (non-protective oxidation), thus at 15 h exposure one can estimate the mass loss to be 6.57 g·cm^?2 after 10 h for direct comparison with the coated samples.