Hygroscopic La[B5O8(OH)]NO3·2H2O: Insight into the evolution of borate fundamental building blocks

The crystal chemistry of plutonium(IV) borophosphate

In this work, we report the synthesis and characterization of a plutonium(IV) borophosphate, Pu(H2O)3[B2(OH)(H2O)(PO4)3] (1). The basic building unit of 1 has a B : P ratio of 2 : 3 with an equal number of BO4 and PO4 groups that assemble into 12-membered rings and take on a sheet topology due to presence of hydroxyl groups or a water molecule on one vertex of each BO4 tetrahedron. This unique borophosphate anion topology is not observed in other members of the borophosphate family; it is the plutonium(IV) metal centers, rather than borate or phosphate groups, that link the sheets to form an extended framework. The presence of boron in 1 was confirmed using single crystal X-ray diffraction, electron microprobe analysis, and infrared spectroscopy. Peaks corresponding to the tetrahedral BO45- and tetrahedral PO43- anions were all identified in the fingerprint region (500-1500 cm-1) of the infrared spectrum. Additionally, peaks in the higher wavenumber region corresponded to crystalline water and B-OH vibrations, providing further evidence for the water molecules surrounding plutonium in the structure and the protonation of the BO4 tetrahedron, respectively. This compound represents the first Pu(IV) borophosphate structure and a novel borophosphate anion topology. Furthermore, the long time-frame required for crystallization of 1 and the suspected leaching of boron from the borosilicate vial used during synthesis indicate that 1 could serve as a model for the crystalline materials that are expected to form during the corrosion of vitrified nuclear waste.

High-pressure synthesis of borate-nitrates: crystal structure of M 3B7O13(NO3) (M = Co2+, Ni2+, Cu2+, Zn2+, Cd2+)

The orthorhombic nitrate-boracites with the sum formula M 3B7O13NO3 (M = Co2+, Ni2+, Cu2+, Zn2+, Cd2+) were synthesized in a Walker-type multianvil apparatus under high-pressure/high-temperature conditions of 6 GPa and 800 °C, respectively. The crystal structures of the five isotypic substances, which crystallize in the space group Pca21, were determined via single-crystal X-ray diffraction and the structural features of the incorporated nitrate anions are discussed.

Ba2B5O8(OH)2(NO3)·3H2O: the design of an alkaline earth metal borate-nitrate optimized from a hydroxylic borate

The first alkaline earth metal borate-nitrate, namely Ba₂B₅O₈(OH)₂(NO₃)·3H₂O (BBNOH), has been synthesized by the hydrothermal method. BBNOH crystallizes in the space group of P2₁/c and shows two-dimensional (2D) ²_∞[B₅O₈(OH)₂]^3- borate anion layers, and the hydrated barium cations and the [NO₃]^- anions are located between the layers. The process of optimizing the structure of Ba₂B₅O₈(OH)₂OH to BBNOH has been discussed. The first principles calculation has been used to calculate the birefringence of Ba₂B₅O₈(OH)₂(NO₃)·3H₂O, and the value is 0.033@1064 nm, which is mainly originated from the borate anions and the π conjugated [NO₃]^- anions.

In situ Raman investigation of the phase transition of NaVO2F2 under variable temperature conditions

In this study, the phase transition of NaVO₂F₂ was measured at different temperatures via in situ Raman spectroscopy. The NaVO₂F₂ compounds were synthesized by a hydrothermal method and were identified to be monoclinic with the P2₁/c space group at room temperature by XRD. Accordingly, the variations of Raman shifts and intensities of the characteristic peaks for NaVO₂F₂ associated with temperature were obtained and investigated. It was confirmed that NaVO₂F₂ had three types of phase transitions, which occurred in the temperature region from 78 K to 573 K. Further, the results indicate that transition from a low-temperature phase (I) to another low-temperature phase (II), low-temperature phase (II) to P2₁/c phase and P2₁/c phase to P2₁/m phase occurred near the three temperature points of 93 K, 233 K, and 453 K, respectively, during the heating process. Therefore, a novel characterization method was provided for further research on the phase transition theory and performance of vanadate compounds.

In this study, the phase transition of NaVO₂F₂ was measured at different temperatures via in situ Raman spectroscopy.

Hydrothermal synthesis and characterization of the praseodymium borate-nitrate Pr[B5O8(OH)(H2O)0.87]NO3·2H2O

The praseodymium borate-nitrate Pr[B5O8(OH)(H2O)0.87]NO3·2H2O was obtained in a hydrothermal synthesis. It crystallizes monoclinically in the space group P21/n (no. 14) with four formula units (Z=4) and unit cell parameters of a=641.9(3), b=1551.8(7), c=1068.4(5) pm, with β=90.54(2)° yielding V=1.0643(8) nm3. The defect variant constitutes the missing member in the series of isostructural, early rare earth borate-nitrates of the composition RE[B5O8(OH)(H2O) x ]NO3·2H2O [RE=La (x=0; 1), Ce (x=1), Nd (x=0.85), Sm (x=0)]. In addition to powder and single-crystal X-ray diffraction data, the novel borate-nitrate was characterized through IR and Raman spectroscopy.

Synthesis and characterization of the alkali borate-nitrates Na3–x K x [B6O10]NO3 (x=0.5, 0.6, 0.7)

Three novel mixed alkali borate-nitrates Na3−x K x [B6O10]NO3 (x=0.5, 0.6, 0.7) were synthesized hydrothermally; their crystal structures were determined through Rietveld analyses, and supported through EDX as well as vibrational spectroscopy. The phases represent solid solutions of the alkali borate-nitrate Na3(NO3)[B6O10], which was reported in 2002 as a “New type of boron-oxygen framework in the Na3(NO3)[B6O10] crystal structure” (O. V. Yakubovich, I. V. Perevoznikova, O. V. Dimitrova, V. S. Urusov, Dokl. Phys. 2002, 47, 791). Only two of the three crystallographically independent Na+ positions in the new structures are partially substituted by K+; a pure potassium borate-nitrate was not formed until now. The cell parameters of the novel phases vary from a=1261.72(5)–1267.12(5), b=1004.19(5)–1007.96(4), c=770.55(3)–774.38(3) pm, and V=0.97630(6)–0.98905(6) nm3 in the orthorhombic space group Pnma (no. 62), in alignment with increasing K+ content.

Hydrogen bond-assisted crystallization: structure, growth and characterization of a new mixed-anion transition metal fluoride Na3NH4(TiF6)(SO4)·H2O

A new type of mixed-anion TM fluoride was grown with a size up to 5.0 × 2.5 × 1.0 mm³ by a facile hydrothermal method.

Polymorphism of NaVO2F2: a P2₁/c superstructure with pseudosymmetry of P2₁/m in the subcell

The ADDSYM routine in the program PLATON [Spek (2015). Acta Cryst. C71, 9-18] has helped researchers to avoid structures of (metal-)organic compounds being reported in an unnecessarily low symmetry space group. However, determination of the correct space group may get more complicated in cases of pseudosymmetric inorganic compounds. One example is NaVO2F2, which was reported [Crosnier-Lopez et al. (1994). Eur. J. Solid State Inorg. Chem. 31, 957-965] in the acentric space group P2₁ based on properties but flagged by ADDSYM as (pseudo)centrosymmetric P2₁/m within default distance tolerances. Herein a systematic investigation reveals that NaVO2F2 exists in at least four polymorphs: P2₁, (I), P2₁/m, (II), P2₁/c, (III), and one or more low-temperature ones. The new centrosymmetric modification, (III), with the space group P2₁/c has a similar atomic packing geometry to phase (I), except for having a doubled c axis. The double-cell of phase (III) arises from atomic shifts from the glide plane c at (x, ¼, z). With increasing temperature, the number of observed reflections decreases. The odd l reflections gradually become weaker and, correspondingly, all atoms shift towards the glide plane, resulting in a gradual second-order transformation of (III) into high-temperature phase (II) (P2₁/m) at below 493 K. At least one first-order enantiotropic phase transition was observed below 139 K from both the single-crystal X-ray diffraction and the differential scanning calorimetry analyses. Periodic first-principles calculations within density functional theory show that both P2₁/c superstructure (III) and P2₁ substructure (I) are more stable than P2₁/m structure (II), and that P2₁/c superstructure (III) is more stable that P2₁ substructure (I).

A facile strategy to adjust the density of planar triangle units in lead borate–nitrates

Three novel lead(ii) borate–nitrates were obtained through a facile hydrothermal reaction by adjusting the concentrations of the starting materials.

Synthesis and characterization of mixed-valence manganese fluorophosphate and analogues with clathrate-like structures: MnIII6F12(PO3(OH))8[Na8(Kx(H3O)4−x(H2O)2)MIV(OH)6] (MIV = Mn, Ti, Ge)

A water-deficient hydrothermal method has been applied to synthesize the first-ever, mixed- and high-valence manganese (Mn³⁺/Mn⁴⁺) fluorophosphate with a clathrate-like structure.