A new polymorph of Cu3B2O6

A new polymorph of nonacopper(II) bis(orthoborate) bis(hexaoxodiborate), Cu₉(BO₃)₂(B₂O₆)₂, or Cu₃B₂O₆ with Z′ = 3, has a pseudo‐layered monoclinic structure containing BO₃ triangles and B₂O₆ units consisting of corner‐sharing BO₃ triangles and BO₄ tetrahedra. The compound was obtained during an investigation of the Li–Cu–B–O system. In contrast to the triclinic form of Cu₃B₂O₆, the layers are linked to one another by BO₄ tetrahedra.     

Synthesis, structural characterization and optical properties of a new cesium aluminum borate, Cs2Al2B2O7

A new borate, Cs₂Al₂B₂O₇, was synthesized by solid-state reaction. It crystallizes in the monoclinic space group P2₁/c with a=6.719(1) Å, b=7.121(1) Å, c=9.626(3) Å, β=115.3(1)°, and Z=2. In the structure, two AlO₄ tetrahedra and two BO₃ planar triangles are connected alternately by corner-sharing to from nearly planar [Al₂B₂O₁₀] rings, which are further linked via common O1 atom to generate layers in the bc plane. These layers then share the O3 atoms lying on a center of inversion to form a three-dimensional framework with Cs atoms residing in the channels. The IR spectrum confirms the presence of both BO₃ and AlO₄ groups and the UV-vis-IR diffuse reflectance spectrum indicates a band gap of about 4.13(2) eV.     

UPON SOME INORGANIC HETEROCYCLES IN THALLIUM (I) BORATES AND GERMANATES

Abstract

The structural study of some hydrated thallium (I) borates shows the existence of macroionic chains which can be considered as condensed heterocycles. In Tl [B₃O₄(OH)₂] 0.5H₂O, the unit is the well known B₃O₃ ring; it is formed by two BO₃ triangles (Δ) and one BO₄ tetrahedron (T); these units are linked to form an infinite chain; its shorthand notation is 3:∞¹ (2Δ + T). The structure of Tl₄ [B₇O₁₀(OH)₃ · OBO(OH)] H₂O contains a unit constituted by three B₃O₃ rings linked together by boron atoms; each ring is formed by two BO₄ tetrahedra and one BO₃ triangle; the corresponding fully hydrated polyanion is [B₇O₉(OH)₇]^4-. The chain is made up of units linked by BO₂(OH) triangles; the shorthand notation of this borate is: 7:∞¹ [(3Δ + 4T) + Δ].

The structure of Tl₈Ge₅O₁₄ is composed of isolated Ge₅O₁₄ units; they are formed by a crown of four GeO₄ tetrahedra linked by shared oxygens; two other oxygens of two of these GeO₄ tetrahedra belong also to a fifth GeO₄ tetrahedron which is located at the center of the crown.     

Syntheses and crystal structures of two new hydrated borates, Zn8[(BO3)3O2(OH)3] and Pb[B5O8(OH)]·1.5H2O

Two new hydrated borates, Zn₈[(BO₃)₃O₂(OH)₃] and Pb[B₅O₈(OH)]·1.5H₂O, have been prepared by hydrothermal reactions at 170 °C. Single-crystal X-ray structural analyses showed that Zn₈[(BO₃)₃O₂(OH)₃] crystallizes in a non-centrosymmetric space group R32 with a=8.006(2) Å, c=17.751(2) Å, Z=3 and Pb[B₅O₈(OH)]·1.5H₂O in a triclinic space group P1¯ with a=6.656(2) Å, b=6.714(2) Å, c=10.701(2) Å, α=99.07(2)°, β=93.67(2)°, γ=118.87(1)°, Z=2. Zn₈[(BO₃)₃O₂(OH)₃] represents a new structure type in which Zn-centered tetrahedra are connected via common vertices leading to helical ribbons _∞¹[Zn₈O₁₅(OH)₃]¹⁷⁻ that pack side by side and are further condensed through sharing oxygen atoms to form a three-dimensional _∞³[Zn₈O₁₁(OH)₃]⁹⁻ framework. The boron atoms are incorporated into the channels in the framework to complete the final structure. Pb[B₅O₈(OH)]·1.5H₂O is a layered compound containing double ring [B₅O₈(OH)]²⁻ building units that share exocyclic oxygen atoms to form a two-dimensional layer. Symmetry-center-related layers are stacked along the c-axis and held together by interlayer Pb²⁺ ions and water molecules via electrostatic and hydrogen bonding interactions. The IR spectra further confirmed the existence of both triangular BO₃ and OH groups in Zn₈[(BO₃)₃O₂(OH)₃], and BO₃, BO₄, OH groups as well as guest water molecules in Pb[B₅O₈(OH)]·1.5H₂O.     

CdZn2KB2O6F,a new fluoride borate crystal

During an attempt to grow crystals of the nonlinear optical material Cd₃Zn₃B₄O₁₂ using a KBF₄ flux, crystals of a new cadmium dizinc potassium borate fluoride compound, CdZn₂KB₂O₆F, were unexpectedly isolated. The structure consists of layers constructed of distorted corner‐sharing ZnO₃F tetrahedra and BO₃ triangles. Both Zn and B reside on threefold rotation axes, while the F⁻ anion is located at a site of 3.2 symmetry. The Cd^II (site symmetry ) and K⁺ (site symmetry 3.2) ions occupy six‐ and nine‐coordinate interlayer sites, respectively. The BO₃ triangles and ZnO₃ pyramids from the ZnO₃F tetrahedra share bridging O atoms with each other to form an extended [ZnBO₃] layer parallel to (001). Although these layers are similar to the [MBO₃] layers seen in other compounds, they are uniquely bridged here by the Cd centres and F⁻ anions to form a three‐dimensional framework. In so doing, a series of channels is formed along the [010] direction and the K⁺ cations are found in these channels.     

Crystal Structure of SrAl2B2O7 and Eu Luminescence

The crystal structure of strontium dialuminodiborate SrAl₂B₂O₇ has been established by single-crystal X-ray diffraction methods. The compound crystallizes in the trigonal system (space group R c, Z=6) with cell parameters a=4.893(1) Å and c=47.78(1) Å. Aluminium and boron atoms are, respectively, in tetrahedral and triangular oxygen coordination. The assembly of Al₂O₇ units and BO₃ triangles forms double layers between which Sr²⁺ ions are located. The Eu²⁺-doped crystalline powder exhibits a luminescence band with maximum at 415 nm. Luminescence characteristics are compared to those of other strontium borates.     

La4B14O27: Ein Lanthan‐ultra‐Oxoborat mit Raumnetzstruktur

La₄B₁₄O₂₇: A Lanthanum ultra‐Oxoborate with a Framework Structure Single crystals of La₄B₁₄O₂₇ could be synthesized by the reaction of La₂O₃, LaCl₃ and B₂O₃ with an access of CsCl as fluxing agent in gastightly sealed platinum ampoules within twenty days at 710 °C and appear as colourless, transparent and waterresistant platelets. The new lanthanum oxoborate La₄B₁₄O₂₇ (monoclinic, C2/c; a = 1120.84(9), b = 641.98(6), c = 2537.2(2) pm, β = 100.125(8)°; Z = 4) is built of a three‐dimensional boron‐oxygen framework containing seven crystallographically different boron atoms. Four of these B³⁺ cations are surrounded by four O^2? anions tetrahedrally, whereas the other three have only three oxygen neighbours with nearly plane triangular coordination figures. Three of the [BO₄]^5? tetrahedra form [B₃O₉]^9? rings by cyclic vertex‐condensation, which are further linked via [BO₃]^3? units to infinite layers. Two of these layers connect via one [B₂O₇]^8? unit of two corner‐shared [BO₄]^5? tetrahedra to double layers, which themselves build up a three‐dimensional framework together with chains consisting of two [BO₄]^5? tetrahedra and one [BO₃]^3? triangle. One of the two crystallographically independent La³⁺ cations (La1) is surrounded by ten O^2? anions and resides within the oxoborate double layers. (La2)³⁺ shows a (8+2)‐fold coordination of O^2? anions and occupies channels along the [110] direction.     

[O2Pb3]2(BO3)Br: An Oxidoborate Oxide Bromide with the ∞1[O2Pb3] Double Chains Based on Edge‐sharing OPb4 Tetrahedra

Through extensive research on the PbO / PbBr₂ / B₂O₃ system, a new single crystal of yellow lead‐containing oxyborate bromine, [O₂Pb₃]₂(BO₃)Br, was grown from the melt. It crystallizes in the centrosymmetric space group Cmcm (no. 63) of the orthorhombic system with the following unit cell dimensions: a = 9.5748(8) Å, b = 20.841(2) Å, c = 5.7696(5) Å, and Z = 4. The whole structure is characterized by an infinite one‐dimensional (1D) _∞¹[O₂Pb₃] double chain, which is based on the OPb₄ oxocentered tetrahedra and considered as the derivative of the continuous sheet of OPb₄ tetrahedra from the tetragonal modification of α‐PbO. The 1D _∞¹[O₂Pb₃] double chains are further bridged by the BO₃ units through common oxygen atoms to form two‐dimensional (2D) _∞¹[[(O₂Pb₃)(BO₃)] layers, with Br atoms situated between the layers. IR spectroscopy, UV/Vis/NIR diffuse reflectance spectroscopy, and thermal analysis were also performed on the reported material.     

K2Fe2B2O7: A transparent nonlinear optical crystal with frustrated magnetism

A new noncentrosymmetric ferroborate crystal, K₂Fe₂B₂O₇, has been grown from high temperature melt. Structure solution from single crystal X-ray diffraction shows that the title compound crystallizes in a trigonal space group P321 with cell dimensions of a=8.7475(12) Å and c=8.5124(17) Å. In the structure, FeO₄ tetrahedron shares its three basal oxygen atoms with BO₃ triangles forming a two-dimensional layer in the ab plane and the layers are connected by the apical Fe-O bonds along the c direction. The crystal is transparent in the visible and near infrared region from 500 to 2000 nm with three pronounced absorption bands ascribed to d-d transitions of tetrahedrally coordinated Fe³⁺ ions. Though, structurally analog to K₂Al₂B₂O₇, the further twisting of the BO₃ groups between adjacent layers reduces its optical nonlinearity to a second-harmonic generation intensity of about 0.4 times that of KDP. Spin-glass behavior is observed at 20 K which is probably due to geometrically magnetic frustration of the triangular Fe net in the ab plane.     

Synthesis and crystal structure of strontium borate Sr<Subscript>4</Subscript>B<Subscript>14</Subscript>O<Subscript>25</Subscript>

The new compound Sr₄B₁₄O₂₅ (4SrO · 7B₂O₃) corresponding to an oxide ratio of 4: 7 has been identified and synthesized in the SrO-B₂O₃ system. The crystal structure of the compound has been determined (space group Cmc2₁, a = 7.734(5) Å, b = 16.332(5) Å, c = 14.556(5) Å, Z = 4, 702 F(hkl), R = 0.078). The borate anions form a three-dimensional framework consisting of borate groups of two types: three-ring structures (2□, Δ) and BO₃ triangles. Layers formed by 14-membered rings composed of boron-oxygen tetrahedra and triangles packed within the layer according to the herringbone pattern can be distinguished in the framework. The strontium atoms are located on the mirror symmetry planes between these layers. The compound is metastable and decomposes, on long-term storage, into strontium di- and metaborate.     

RbMT3(BO3)2O3 (M=Ba,Sr; T=Al,Ga): New Double-Layered Oxyborates Constructed from [BO3] Triangles and [TO4] Tetrahedra

Four new alumino-/galloborates RbMT₃(BO₃)₂O₃ (M=Ba, Sr; T=Al, Ga) have been synthesized for the first time by using a high-temperature solution method. All the title compounds have Sr₂Be₂B₂O₇-like structures, in which the [BO₃] triangles and [TO₄] tetrahedra form the final double-layered configurations with the M- and Rb-site atoms located between and in the double layer, respectively. The structure evolution from Sr₂Be₂B₂O₇ to RbMT₃(BO₃)₂O₃ series is discussed. The broader energy bandgaps in Al-based borates when compared with Ga-based ones can be entirely attributed to the location of Al/Ga s orbitals near the Fermi surface. Both experimental and computational approaches were used to study their structure-property relationships.     

KNiB4O6F3: A Layered Fluorooxoborate with Charge-Oriented Ordering

A layered fluorooxoborate, KNiB₄O₆F₃, contains a new (B₄O₆F₄)⁴⁻ group built of one planar (BO₃)³⁻ triangle and three tetrahedral (BO₃F)⁴⁻ units. Those units are joined together by sharing the oxygen atoms to form a 2-dimensinal (BO_3/2F)₃BO_3/2)_∞ layer. K⁺ and Ni²⁺ occupy on the sides with F⁻ and O²⁻ of the (BO_3/2F)₃BO_3/2)_∞ layer with a high (positive charge) to high (negative charge) and low to low coordination. Such kind of charge-oriented ordering is found to be governed by the stabilization energy of Coulomb interaction of the cations in certain sites. It is hoped that this mechanism of ordering may provide an additional tool for designing new structures with favourable properties, such as ferroelectrics or nonlinear optical materials.     

RbLi2Ga2(BO3)3

The structure of rubidium dilithium digallium tris­(borate), RbLi₂Ga₂(BO₃)₃, contains two‐dimensional sheets of open‐branched rings of GaO₄ tetrahedra and planar BO₃ triangles that are joined by LiO₄ tetrahedra to form a three‐dimensional framework. Ten‐coordinate Rb atoms lie on twofold axes and occupy channels within the framework that extend along the b axis.     

过渡金属硼酸盐K7{(BO3)Zn[B12O18(OH)6]}·H2O的合成与量子化学研究

通过水热的方法合成了一例新的过渡金属硼酸盐K7{(BO3)Zn[B12O18(OH)6]}·H2O(1),并对其进行了红外,热重,能谱以及X-射线单晶衍射和粉末衍射分析。晶体学测试结果表明,化合物1属于正交晶系,Pmn21空间群,晶胞参数a=1.236 51(4)nm,b=0.909 61(3)nm,c=1.304 05(5)nm,V=1.466 72(9)nm3,Z=2,R1=0.049 7,wR2=0.146 8。对{(BO3)Zn[B12O18(OH)6]}7-阴离子簇的量化分析显示此簇中的端基BO3基团对前线分子轨道的贡献最大。除端O原子外,BO3端基的原子电荷较其它B和O原子电荷低。     

A New Sodium Borate: Na[B6O8(OH)3]·6H2O·H3BO3

The structure of [B₆H₉NaO₁₄, H₃BO₃, 6H₂O] was determined by single‐crystal X‐ray diffraction and further analyzed by FTIR spectroscopy and differential thermal/thermogravimetric analysis. The asymmetric unit contains Na–O polyhedra (distorted octahedron), [B₆O₈(OH)₃]^– fundamental building blocks, one free water molecule and one free H₃BO₃ molecule. In the hexaborate anion, three B₃O₃ rings are linked by a common oxygen atom with five trigonal and one tetrahedral boron atoms. The hexaborate group is also linked to the oxygenated environment of the sodium atom by three other six‐membered rings, each of which involve two boron atoms, three oxygen atoms, and sodium as the joint atom.     

Synthesis and Crystal Structure of the First Fully Characterized Vanadoborate Na3[B6O9(VO4)]

Single crystals of synthetic Na₃VB₆O₁₃ were obtained by heating a mixture of Na₂CO₃.H₂O, V₂O₅, and H₃BO₃; its formula has been determined by the resolution of the structure from X-ray diffraction data. The compound is orthorhombic, space group P2₁2₁2₁; the unit cell parameters are a=7.723(7), b=10.155(4), c=12.505(4) Å, Z=4. The crystal structure was solved from 1535 reflections until R=0.029; it contains hexaborate units formed by three triangular BO₃ (3Δ) and three tetrahedral BO₄ (3T). These hexaborate groups are joined together to form sheets which are linked by VO₄ tetrahedra leading to a three-dimensional network. The shorthand notation of the vanadoborate ion is 6: ∞³ (3Δ+3T)+VO₄. The sodium atoms are inside the channels that exist in the compound, whose structural formula may be written Na₃[B₆O₉(VO₄)]. This compound melts incongruently; powder may be obtained by annealing a mixture of Na₂B₄O₇ and V₂O₅ at 630°C. It is the first vanadoborate for which the formula and the structure have been unambiguously established.     

Synthesis, crystal structure and optical properties of the new lead fluoride borate—Pb2BO3F

A new compound, Pb₂BO₃F, has been grown by high temperature solution method from the PbO–PbF₂–B₂O₃ system for the first time. The crystal structure of this compound has been identified by single crystal X-ray diffraction analysis. It crystallizes in the hexagonal system, space group P6₃/m (No. 176) with unit-cell parameters a=7.2460(3) Å, c=14.5521(17) Å, Z=6, V=661.69(9) ų. Its structure was solved by the direct methods and refined to R₁=0.0163 and wR₂=0.0367. The structure of Pb₂BO₃F consists of the distorted PbO₃F₂ groups and BO₃ triangles, which are all symmetric with each other in the gestalt structure to the extent that the Pb₂BO₃F compound crystallizes in the symmetric space group. The powder X-ray diffraction pattern of the Pb₂BO₃F has been measured. The BO₃ functional groups presented in the sample were identified by FTIR spectrum. The DTA curve of Pb₂BO₃F suggests that Pb₂BO₃F melts congruently at 448 °C.     

A new rubidium beryllium borate,RbBe4(BO3)3

Single crystals of a new rubdidium beryllium borate, RbBe₄(BO₃)₃, have been obtained by spontaneous nucleation from a high‐temperature melt. This new ortho­rhom­bic (Pnma) structure type contains [Be₂BO₄]⁻ rings, made of two BeO₄ tetra­hedra and one BO₃ triangle, which constitute the basic structural units. The m plane runs through the B and one of the O atoms and intersects the ring. These rings form chains in the a direction, which are connected in the b and c directions to form zeolite‐type cages in which the Rb⁺ cations are located, at sites of m symmetry.     

Crystal Structure of a New Form of Sodium Octoborate β-Na2B8O13

Single crystals of a new form of sodium octoborate, β-Na₂B₈O₁₃, were obtained fortuitously from a complex Na₂O-B₂O₃-P₂O₅ mixture, and studied. The compound is monoclinic, space group P2₁/c; the unit cell parameters are a=11.731(4) Å, b=7.880(3) Å, c=10.410(4) Å, β=99.883(3)°; Z=4. The crystal structure was solved from 1653 reflections until R₁=0.0444; it consists of two infinite, independent, and interleaved boron-oxygen networks containing a complex borate anion (B₈O₁₃)²⁻ formed by six BO₃ triangles (Δ) and two BO₄ tetrahedra (T), which can be viewed as a B₅O₁₀ group linked to a B₃O₇ group; this leads to a Fundamental Building Block (FBB) with the shorthand notation: 8: ∞³ [(5:4Δ+T)+(3:2Δ+T)]. This FBB is identical to that described in other octoborates such as α-Na₂B₈O₁₃ and Ag₂B₈O₁₃. However, some subtle differences exist in the interlinking of the octoborate anions found in these three compounds, which explains their different structure and unit cell parameters.     

Synthesis and Crystal Structure of Commensurate Polymorph of Ln4AlCu2B9O23 (Ln=Lu,Ho) and Refinement of Cu2Al6B4O17

Single crystals of new Cu,Lu(Ho)–alumoborate and known Cu,Al–borate were synthesized through reaction between CuB₂O₄ and LnBO₃ on the Al₂O₃ surface by annealing at 1100 °C. Structure of commensurate modification of Ln₄AlCu₂B₉O₂₃, (Ln = Lu,Ho), sp. gr. , was solved at room temperature. It was found that a low–temperature (110 K) modification possesses incommensurate modulations with modulation vector q =(0, 0, 0.132). The nonaborate block – [B₉O₂₃]^19– – 9[6T+3Δ] forms an isolated unique dense closed anionic unit. This block is terminated by Al–tetrahedrons in the chessboard pattern, resulting in formation of complex alumoborate layer [AlB₉O₂₃]^16–. Apical oxygen of central BO₃ triangle of the nonaborate block seems to be the source of modulations observed in low temperature polymorph. Cationic layers with the Ln and Cu atoms are alternating along c axis with anionic layers. The structure Cu₂Al₆B₄O₁₇, previously studied by the Rietveld method, was corroborated by single crystal data and was compared with LiAl₇B₄O₁₇.