High-temperature, high-pressure hydrothermal synthesis, crystal structure, and solid state NMR spectroscopy of a lead borosilicate with boron-silicon mixing: Pb6B2Si8O25.

A new lead(ii) borosilicate, Pb6B2Si8O25 (1), has been synthesized by a high-temperature, high-pressure hydrothermal reaction at 480 °C and 990 bar. Its structure was determined by single-crystal X-ray diffraction. The reaction product was phase-pure as indicated by powder X-ray diffraction and whole pattern fitting using the Pawley method. Compound 1 has a 2D layer structure with the lead ions being located at interlayer regions. Each layer is formed of corner-sharing BO4 or SiO4 tetrahedra and contains an eight-ring window. The layer consists of a new fundamental building block (FBB) with the formula T8O23 (T: B or Si) formed by two (B(1)0.8Si(1)0.2)O4 tetrahedra and six (Si(2)0.933B(2)0.067)O4 tetrahedra. The FBB can be described as double open-branched triple tetrahedra. Another interesting structural feature of 1 is boron-silicon mixing which is uncommon in borosilicates. There are three unique tetrahedra in the structure: B(1)O4 tetrahedra with 20% substitution of Si for B, Si(2)O4 tetrahedra with 6.67% substitution of B for Si, and Si(3)O4 tetrahedra without substitution. We have applied 11B and 29Si MAS NMR spectroscopy to study the substitutional disorder. The NMR study results not only confirm the mixing of B and Si atoms in the structure, but also verify quantitatively the results from single-crystal X-ray diffraction. The reasons for boron-silicon mixing in the structure are discussed. Crystal data for 1: trigonal, R3[combining macron]c (no. 167), a = 9.5090(2) Å, c = 42.3552(8) Å, V = 3316.7(2) Å3, Z = 6, R1 = 0.0147, and wR2 = 0.0309.

Hydrothermal synthesis, crystal structures, and X-ray photoelectron spectroscopy of lead tellurium(IV) and tellurium(VI) oxycompounds: Ba3PbTe6O16 and Na2Pb9(µ6-O)2(Te2O10)2.

An exploratory study of the lead-tellurium-oxygen phase space led to two new compounds, Ba3PbTe6O16 (BPTO) and Na2Pb9(µ6-O)2(Te2O10)2 (NPTO), which were synthesized under hydrothermal conditions at 550 °C and 210 °C, respectively, and characterized by single-crystal X-ray diffraction, infrared and X-ray photoelectron spectroscopy. BPTO adopts a layer structure. The Te4+ cation in BPTO is bonded to four oxygen atoms at about 2.0 Å with two more oxygens at about 3.0 Å. The seesaw-shaped TeO4 units share corners to form 2D layers containing six-membered rings and the Ba2+ and Pb2+ cations are situated in the interlayer region. The structure of NPTO contains dimers of edge-sharing Te6+O6 octahedra, which are connected through five-coordinate Pb2+ cations. A unique six-coordinate O atom is at the center of the octahedron formed by five Pb2+ and one Na+ cations. BPTO is one of the few metal tellurites which were synthesized under supercritical hydrothermal reaction conditions. The Pb2+ cation in NPTO shows pronounced stereochemical effects of the lone electron pair. In contrast, BPTO shows no stereochemical evidence of the inert pair.

High-temperature, high-pressure hydrothermal synthesis, crystal structure, and infrared and NMR spectroscopy of a barium lead borate with a 2D layer structure: [Ba3Pb(H2O)][B11O19(OH)3].

With a high-temperature, high-pressure hydrothermal technique, a new barium lead borate, [Ba3Pb(H2O)][B11O19(OH)3] (1), has been synthesized and characterized by single-crystal X-ray diffraction, and infrared and solid-state NMR spectroscopy. The structure of 1 contains planar thick layers of borates with the Ba2+ cations at sites in the inter- and intralayer space. Each layer consists of three single sheets. The central sheet is very corrugated and is built up from the fundamental building block (FBB) 2Δ3□:Δ2□-Δ2□. On both sides of the central sheet there are borate single chains formed of the very rare FBB 2Δ4□:Δ2□-3â–¡Δ via corner-sharing. This FBB was first observed in a high-pressure polymorph of CaB2O4. These chains are linked into a sheet by PbO5(H2O) polyhedra, which are further linked to the central sheet by sharing vertices between triangles and tetrahedra to form a thick layer. The IR spectrum shows the presence of hydroxyl groups of HBO4, water molecules, BO3 triangles, and BO4 tetrahedra. The presence of BO3 and BO4 polyhedra was also confirmed by 11B MAS NMR spectroscopy.

Correction: Ca10Na10[Te9O42](H2O): a hydrothermally synthesized quaternary tellurium(vi) oxide containing edge-sharing octahedral trimers.

Correction for 'Ca10Na10[Te9O42](H2O): a hydrothermally synthesized quaternary tellurium(vi) oxide containing edge-sharing octahedral trimers' by Li-Yun Zhang, et al., Dalton Trans., 2019, DOI: 10.1039/c9dt03521d.

Ca10Na10[Te9O42](H2O): a hydrothermally synthesized quaternary tellurium(vi) oxide containing edge-sharing octahedral trimers.

A new tellurium(vi) oxycompound, Ca10Na10[Te9O42](H2O), was synthesized by a high-temperature, high-pressure hydrothermal reaction at 550 °C, its structure determined by single-crystal X-ray diffraction, and further characterized by energy dispersive, infrared, and X-ray photoelectron spectroscopy. The compound crystallizes in the centrosymmetric trigonal space group R3[combining macron]c (no. 167) with a = 9.743(2), c = 66.337(13) Å, and Z = 6. The structure consists of discrete linear edge-sharing octahedral trimers with the composition Te3O1410-, which is a new type of finite Te-O oligomer with Te6+ only. The large complex anions form a hexagonal close-packed lattice with the octahedral and tetrahedral interstices being filled with Ca2+ and Na+ cations and water molecules. The octahedral trimers in every other h.c.p. layer rotate around the 31 screw axis for 120°; therefore the unit cell has a very long c axis. This work is one of the few examples of the synthesis of metal tellurates by supercritical hydrothermal techniques.

Edge-Sharing BO4 Tetrahedra in the Structure of Hydrothermally Synthesized Barium Borate: α-Ba3[B10O17(OH)2].

Two polymorphs of a new barium borate, α- and ß-Ba3[B10O17(OH)2], have been synthesized through hydrothermal reactions at 500 °C and 1000 bar and their structures determined by single-crystal X-ray diffraction. The 3D framework structure of the α-form is formed of two different fundamental building blocks (FBB) with the descriptors 4Δ6□:[⧄⧅]-<3□>-<2Δ□>|-<3□>-<2Δ□>| and 2Δ3□:<Δ2□>-<Δ2□>. The former FBB is unique and contains unusual edge-sharing BO4 tetrahedra. The ß-form has a double layer structure which is formed of two stereoisomers of a pentaborate polyanion with the descriptor 2Δ3□:<Δ2□>-<Δ2□>. Within a double layer, one sheet composed of FBBs in l configuration is connected by sharing tetrahedral vertices to the other sheet of FBBs in d configuration. The α-form is the first compound with edge-sharing BO4 tetrahedra synthesized in aqueous solution under hydrothermal conditions.

High-Temperature, High-Pressure Hydrothermal Synthesis of Ba3[B6O10(OH)2](CO3) and Ba6[B12O21(OH)2](CO3)2, Two Barium Borate Carbonates with 2D Layer and 3D Framework Structures.

Two new barium borate carbonates, Ba3[B6O10(OH)2](CO3) (1) and Ba6[B12O21(OH)2](CO3)2 (2), have been synthesized by high-temperature, high-pressure hydrothermal methods at 460 °C and 600 bar and structurally characterized by single-crystal X-ray diffraction, TGA, IR, and MAS 11B NMR spectroscopy. The descriptors of the fundamental building blocks (FBB) of both structures are 2Δ4□:⟨Δ2□⟩=⟨4□⟩=⟨Δ2□⟩. The FBB of 1 has a chair conformation, and the FBBs of 2 have both chair and boat conformations. Compound 1 adopts a noncentrosymmetric 2D layer structure with the Ba2+ cations and CO32- anions between the layers, whereas compound 2 has a centrosymmetric 3D framework structure containing 9- and 10-ring channels with the Ba2+ cations and CO32- anions at the center or on the edges of the channels. The two structures are two of the few examples where the carbonate groups are isolated and occupy their own independent sites.

High-Temperature, High-Pressure Hydrothermal Synthesis and Characterization of an Acentric Borate Fluoride: Ba2B5O9F·0.5H2O.

A new borate fluoride, Ba2B5O9F·0.5H2O, has been synthesized by high-temperature, high-pressure hydrothermal method, characterized by a combination of techniques and its structure determined by single-crystal X-ray diffraction. The compound crystallizes in the noncentrosymmetric space group P4̅ n2 (No. 118) and powder SHG measurements were performed to confirm the absence of a center of symmetry. Its crystal structure is formed of a new fundamental building block which shares oxygen atoms with neighboring blocks to form a 3D borate framework with 12- and 8-ring channels where the Ba2+ cations, F- anions, and water molecules are located. The structure is compared with those of minerals and synthetic borate fluoride and chlorides with similar framework compositions. The 11B MAS NMR experimental results are in accord with those from crystal structure analysis and the resonances in the spectrum are assigned. The presence of water was confirmed by IR spectroscopy, and its content and the thermal decomposition products were determined by thermogravimetric analysis and powder X-ray diffraction.

High-Temperature, High-Pressure Hydrothermal Synthesis, Crystal Structure, Thermal Stability, and Solid State NMR Spectroscopy of an Aluminum Borate, Ba[AlB4O8(OH)].

A new aluminum borate, Ba[AlB4O8(OH)], has been synthesized under high-temperature, high-pressure hydrothermal conditions at 550 °C and 1400 bar and its structure characterized by single-crystal X-ray diffraction, IR, and MAS 11B, and 27Al NMR spectroscopy. It crystallizes in the monoclinic space group P21/n with a = 7.0695(5) Å, b = 15.108(1) Å, c = 7.0746(5) Å, ß = 93.593(2)°, and Z = 4. Its 2D layer structure is formed of corner-sharing B4O8(OH) clusters and AlO4 tetrahedra with the charge-compensating Ba2+ cations between the layers. While the same in the framework composition, the title compound and the hydrate, Ba[AlB4O8(OH)]·H2O, differ greatly in structure. Although the title compound contains an OH group, it is thermally stable up to 740 °C and then decomposes into Ba2Al2B8O17, as indicated by high-temperature DSC/TG analysis and powder X-ray diffraction.

Two Polymorphs of an Organic-Zincophosphate Incorporating a Terephthalate Bridging Ligand in an Unusual Bonding Mode.

Two new polymorphs of a zinc phosphate incorporating the terephthalate organic ligand 1,4-benzenedicarboxylate (BDC), (H2DA)Zn2(cis-BDC)(HPO4)2 (1) and (H2DA)Zn2(trans-BDC)(HPO4)2 (2), where DA = 1,7-diaminoheptane, were synthesized via a hydro(solvo)thermal method at different reaction temperatures and structurally characterized by single-crystal X-ray diffraction. Interestingly, the BDC ligands, which adopt the bis-monodentate coordination model with a unusual cis type for compound 1 and with a trans linkage for compound 2, bridge the Zn atoms of the inorganic layers in the generation of two polymorphs with structural diversities (one kind of arrangement of the layered zincophosphate layer in 1; the flat and zigzag sheets of inorganic networks in 2). A simple method for tuning the optical luminescence of the title compound from blue, red, green, yellow, and pink to white emission by stirring powdered samples in lanthanide-cation-containing aqueous ethanol solutions at room temperature for 1-2 h is also presented.

Titanosilicates with Strong Phase-Matched Second Harmonic Generation Responses.

The search for new and efficient nonlinear optical (NLO) materials has been an active research because of their technological importance in laser applications. Although a large number of frequency-doubling oxides, phosphates, borates, and fluoride-containing borates were found, no transition-metal silicate with useful NLO properties has been reported. We have now synthesized and grown crystals of two new titanosilicates, Li2K4[(TiO)Si4O12] and Li2Rb4[(TiO)Si4O12], by using a flux and supercritical hydrothermal method. Their unique 3D framework structures contain highly compressed TiO5 square pyramids which are arranged one over the other to form infinite ···Ti-O···Ti-O straight chains with alternating short and long Ti-O distances. These two materials meet the requirements for efficient second harmonic generation including lack of center of inversion symmetry, large susceptibility, phase matching, transmitting at wavelengths of interest, resistant to laser damage, and thermally stable. These attributes make them very attractive for frequency-doubling materials.

K2Ca4[(UO2)(Si2O7)2]: A Uranyl Silicate with a One-Dimensional Chain Structure.

A new uranyl silicate, K2Ca4[(UO2)(Si2O7)2], with a 1D chain structure has been synthesized from a solution of mixed alkali- and alkaline-earth-metal cations under hydrothermal conditions at 550 °C and 1400 bar and characterized by single-crystal X-ray diffraction and photoluminescence spectroscopy. It crystallizes in the triclinic space group P1̅ (No. 2) with a = 6.6354(2) Å, b = 6.6791(2) Å, c = 9.6987(3) Å, α = 98.324(2)°, ß = 93.624(2)°, γ = 112.310(2)°, and Z = 1. Its crystal structure consists of a 1D chain of uranyl disilicate formed of corner-sharing UO6 tetragonal bipyramids and Si2O7 double groups. The adjacent chains are separated by K(+) and Ca(2+) cations. It is the first example of uranyl silicate with a 1D chain structure.

The first zinc phosphite with remarkable structural and functional transformations.

A new zinc phosphite exhibited remarkable structural transformations upon heat stimulation to convert into a dehydrated form (NCU-2a) and a new structure, NCU-2b. The gas adsorption properties of the materials as well as the luminescence properties of LED devices fabricated using these materials were also investigated.

Organic-inorganic hybrid zinc phosphate with 28-ring channels.

An organic-inorganic hybrid zinc phosphate with 28-ring channels was synthesized by use of an organic ligand instead of organic amine template under a hydro(solvo)thermal condition. This crystalline zinc phosphate contains large channels constructed from 28 zinc and phosphate tetrahedral units. The walls of the channels consist of two types of zincophosphate chains, in which the Zn atoms are coordinated by 2,4,5-tri(4-pyridyl)-imidazole ligands as pendent groups. This compound exhibits yellow emission and interesting properties of removing cobalt, cadmium, and mercury cations from aqueous solution. A new two-dimensional organic-inorganic hybrid zincophosphate was also obtained by changing the solvent mixture ratios in the synthesis.

High-temperature, high-pressure hydrothermal synthesis, characterization, and structural relationships of layered uranyl arsenates.

Five new uranyl arsenates, Na14[(UO2)5(AsO4)8]·2H2O (1), K6[(UO2)5O5(AsO4)2] (2a), K4[(UO2)3O2(AsO4)2] (2b), Rb4[(UO2)3O2(AsO4)2] (3), and Cs6[(UO2)5O2(AsO4)4] (4), were synthesized by high-temperature, high-pressure hydrothermal reactions at about 560 °C and 1440 bar and were characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and photoluminescence spectroscopy. Crystal data for compound 1: triclinic, P1, a = 7.0005(3) Å, b = 12.1324(4) Å, c = 13.7428(5) Å, α = 64.175(2)°, ß = 89.092(2)°, γ = 85.548(2)°, V = 1047.26(7) Å(3), Z = 1, R1 = 0.0185; compound 2a: monoclinic, P21/c, a = 6.8615(3) Å, b = 24.702(1) Å, c = 7.1269(3) Å, ß = 98.749(2)°, V = 1193.89(9) Å(3), Z = 2, R1 = 0.0225; compound 2b: monoclinic, P21/c, a = 6.7852(3) Å, b = 17.3640(8) Å, c = 7.1151(3) Å, ß = 98.801(3)°, V = 828.42(6) Å(3), Z = 2, R1 = 0.0269; compound 3: monoclinic, P21/m, a = 6.9783(3) Å, b = 17.4513(8) Å, c = 7.0867(3) Å, ß = 90.808(3)°, V = 862.94(7) Å(3), Z = 2, R1 = 0.0269; compound 4: triclinic, P1, a = 7.7628(3) Å, b = 9.3324(4) Å, c = 11.9336(4) Å, α = 75.611(2)°, ß = 73.136(2)°, γ = 86.329(2)°, V = 801.37(5) Å(3), Z = 1, R1 = 0.0336. The five compounds have layer structures consisting of uranyl square, pentagonal, and hexagonal bipyramids as well as AsO4 tetrahedra. Compound 1 contains chains of discrete uranyl square and pentagonal bipyramids, 2a contains three-polyhedron-wide ribbons of edge- and corner-sharing uranyl square and pentagonal bipyramids, 2b and 3 contain dimers of edge-shairing pentagonal bipyramids that share edges with hexagonal bipyramids to form chains, and 4 contains one-polyhedron-wide zigzag chains of edge-sharing uranyl polyhedra. The double sheet structure of 1 is new, but the chain topology has been observed in an organically templated uranyl sulfate. Compound 2b is a new geometrical isomer of the phosphuranylite group. The sheet anion topologies of 2a and 4 can be obtained by splitting the ß-U3O8-type sheet into complex chains and connecting the chains by arsenates.

New nanostructured zinc phosphite templated by cetyltrimethylammonium cations: synthesis, crystal structure, adsorption, and photoluminescence properties.

Nanostructured zinc phosphite templated by cetyltrimethylammonium (CTA(+)) cations was synthesized using a hydro(solvo)thermal method. This is the first example of a crystalline metal phosphite containing long carbon tails of the CTA(+) ions as templates in its structure, as is structurally characterized by single-crystal X-ray diffraction. The 2D inorganic structures with 4.8(2) topologies are constructed from the interconnection of tetrahedral ZnO3Br and HPO3 units, which are sandwiched between CTA(+) ion surfactants in a packing behavior of a largely lamellar liquid-crystalline structure to extend the interlayer d spacing to 28.05 Å. Adsorption experiment shows selective adsorption properties of 1-naphthol and a adsorption capacity of 0.17 mmol/mmol (CTA)ZnBr(HPO3). This compound has potential as an adsorbent for the removal of 1-naphthol pollutant from wastewater. In addition, the naphthol-adsorbed sample shows interesting luminescent properties that are different from that of an as-synthesized sample. The crystal structure, thermal stability, IR spectrum, adsorption, and photoluminescence properties have been studied.

High-temperature, high-pressure hydrothermal synthesis, crystal structures, and spectroscopic studies of a uranium(IV) phosphate (Na10U2P6O24) and the isotypic cerium(IV) phosphate (Na10Ce2P6O24).

A uranium(IV) phosphate, Na10U2P6O24, was synthesized under hydrothermal conditions at 570 °C and 160 MPa and structurally characterized by single-crystal X-ray diffraction. The valence state of uranium was established by UV-vis and U 4f X-ray photoelectron spectroscopy. The powder sample has a second-harmonic-generation signal, confirming the absence of a center of symmetry in the structure. The structure contains UO8 snub-disphenoidal polyhedra that are linked to monophosphate tetrahedra by vertex and edge sharing such that a three-dimensional framework with intersecting 12-sided circular and rectangular channels is formed. All 10 sodium sites are situated inside the channels and are fully occupied. This is the first uranium(IV) phosphate synthesized under high-temperature, high-pressure hydrothermal conditions. The isotypic cerium(IV) phosphate, Na10Ce2P6O24, was also synthesized under the same hydrothermal conditions. It is the first structurally characterized Ce(IV) phosphate with a P/Ce ratio of 3. Crystal data of Na10U2P6O24: orthorhombic, P212121 (No. 19), a = 6.9289(3) Å, b = 16.1850(7) Å, c = 18.7285(7) Å, V = 2100.3(2) Å(3), Z = 4, R1 = 0.0304, and wR2 = 0.0522. Crystal data of Na10Ce2P6O24: orthorhombic, P2(1)2(1)2(1) (No. 19), a = 6.9375(14) Å, b = 16.215(3) Å, c = 18.765(4) Å, V = 2111.0(7) Å(3), Z = 4, R1 = 0.0202, and wR2 = 0.0529.

Mixed-valence uranium(V,VI) and uranyl oxyhydroxides synthesized under high-temperature, high-pressure hydrothermal conditions: Na5[U5O16(OH)2] and Na5[U5O17(OH)].

An unusaul mixed-valence uranium(V,VI) oxyhydroxide, Na5[U5O16(OH)2], was synthesized via reduction of UO2(2+) with zinc under hydrothermal conditions at 570 °C and 150 MPa. Its structure consists of extended sheets of edge-sharing U(VI) pentagonal bipyramids and U(V) square bipyramids. The overall anion topology is the same as that of the uranyl mineral sayrite, but the squares are populated by U(V)(OH)2(3+) ions. The valence state of uranium was confirmed by X-ray photoelectron spectroscopy. A hydrothermal reaction without zinc under the same reaction conditions yielded a uranyl oxyhydroxide, Na5[U5O17(OH)], with a new sheet structure. The sheet anion topology, which is closely related to that of the mixed-valence compound, contains chains of edge-sharing pentagons as well as dimers of corner-sharing squares.

High-temperature, high-pressure hydrothermal synthesis and characterization of a salt-inclusion mixed-valence uranium(V,VI) silicate: [Na9F2][(U(V)O2)(U(VI)O2)2(Si2O7)2].

A salt-inclusion mixed-valence uranium(V,VI) silicate, [Na9F2][(U(V)O2)(U(VI)O2)2(Si2O7)2], was synthesized under hydrothermal conditions at 585 °C and 160 MPa and structurally characterized by powder and single-crystal X-ray diffraction (XRD). The valence states of uranium were established by U 4f X-ray photoelectron spectroscopy (XPS). The structure contains two-dimensional (2D) sheets of uranyl disilicate with the composition [UO2Si2O7], which are connected by U(1)(V)O6 tetragonal bipyramids to form thick layers. The Na(+) cations are located at sites in the intralayer and interlayer regions. In addition to Na(+) cations, the interlayer region also contains F(-) anions such that infinite chains with the formula FNa1/1Na4/2 are formed. The same type of chain was observed in K2SnO3. The title compound is not only the first example of salt-inclusion metal silicate synthesized under high-temperature, high-pressure hydrothermal conditions, as well as the first salt-inclusion mixed-valence uranium silicate, but it is also the first mixed-valence uranium(V,VI) silicate in the literature. Crystal data: [Na9F2][(U(V)O2)(U(VI)O2)2(Si2O7)2], triclinic, P1 (No. 2), a = 5.789(1) Å, b = 7.423(2) Å, c = 12.092(2) Å, α = 90.75(3)°, ß = 96.09(3)°, γ = 90.90(3)°, V = 516.5(2) Å(3), Z = 1, R1 = 0.0241, and wR2 = 0.0612.

Flux synthesis, crystal structure, and photoluminescence of a heterometallic uranyl-europium germanate with U═O-Eu linkage: K4[(UO2)Eu2(Ge2O7)2].

Crystals of a uranyl-europium germanate, K4[(UO2)Eu2(Ge2O7)2], have been grown at high temperature from a KF-MoO3 flux and structurally characterized by single-crystal X-ray diffraction. The structure contains PaCl5-type chains formed of edge-sharing EuO7 pentagonal bipyramids that are connected by digermanate groups such that layers of europium germanate are formed. Neighboring layers are further linked by UO6 tetragonal bipyramids through uranyl ion oxygen atoms to generate a 3D framework with 6-ring channels where the K(+) cations are located. The structure contains an unusual heterometallic U═O-Eu linkage. Photoluminescence studies show strong red emission at room temperature. The relative intensities of the (5)D0 → (7)F1 and (5)D0 → (7)F2 transitions confirm that the europium site lacks an inversion center. All of the emission lines show similar decay curves, which can be well-fitted by a single exponential decay function with radiative lifetimes of 0.53 ± 0.03 ms. No emission is observed in the region from 450 to 550 nm typical of the uranyl cation, indicating that, upon uranyl excitation, the energy is either transferred to the Eu(3+) centers or lost to nonradiative processes.