New epsilon-Bi2O3 metastable polymorph

The new metastable epsilon-Bi2O3 polymorph has been prepared by hydrothermal treatment and structurally characterized. It shows strong relationships with the room temperature alpha form and the metastable beta form through rearrangements of [Bi2O3] columns formed by edge-sharing OBi4 tetrahedra. Its fully ordered crystal structure yields an ionic insulating character. It irreversibly transforms at 400 degrees C to the alpha form. The chemical analysis indicates its undoped bismuth oxide nature, then leading to the fifth characterized Bi2O3 polymorph to date.     

A novel crystal polymorph of volborthite,Cu3V2O7(OH)2·2H2O

A new polymorph of volborthite [tricopper(II) divanadium(V) heptaoxide dihydroxide dihydrate], Cu₃V₂O₇(OH)₂·2H₂O, has been discovered in a single crystal prepared by hydrothermal synthesis. X‐ray analysis reveals that the monoclinic structure has the space group C2/c at room temperature, which is different from that of the previously reported C2/m structure. Both structures have Cu₃O₆(OH)₂ layers composed of edge‐sharing CuO₄(OH)₂ octahedra, with V₂O₇ pillars and water molecules between the layers. The Cu atoms occupy two and three independent crystallographic sites in the C2/m and C2/c structures, respectively, likely giving rise to different magnetic interactions between Cu^II spins in the kagome lattices embedded in the Cu₃O₆(OH)₂ layers.     

Ba2Cd(B3O6)2: A Congruent‐Melting Compound with Isolated B3O6 Units

The single crystals of Ba₂Cd(B₃O₆)₂ were grown by the spontaneous crystallization method for the first time. They crystallize in the centrosymmetric trigonal space group R$\bar{3}$ with a = 7.143(3) Å, c = 17.405(16) Å, and Z = 3. The structure is characterized by isolated B₃O₆ units, and the Ba²⁺ and Cd²⁺ cations connect with B₃O₆ rings to form three dimensional structure. The TG/DSC and XRD results reveal that Ba₂Cd(B₃O₆)₂ melts congruently. First‐principles electronic structure calculation performed with the density functional theory (DFT) method shows that the calculated bandgaps are 4.66 eV, which is in good agreement with the UV/Vis/NIR experimental value 4.59 eV. The calculation shows that the Ba₂Cd(B₃O₆)₂ crystal has a large birefringence (Δn = 0.0875–0.0569 from 270 nm to 2600 nm), which demonstrates that Ba₂Cd(B₃O₆)₂ is a potential birefringence crystal.     

HYDROGENATION OF CO_2 OVER A YBa_2Cu_3O_(6～7) CATALYST

研究了ＹＢａＣｕ３Ｏ６～７超导催化剂上ＣＯ２的加氢制醇反应。考察了温度、压力和空速等条件对催化剂反应性能的影响。反应的主要产物是甲醇、ＣＯ和少量甲醚。利用ＸＰＳ、ＸＲＤ和ＡＦＭ等技术对催化剂的结构、铜的存在状态和反应活性位进行表征发现，在反应过程中，ＹＢａ２Ｃｕ３Ｏ６～７由ｏｒｔｈｏｍｂｉｃ相转变为ｔｅｔｒａｇｏｎａｌ相。反应活性位可能是Ｃｕ（Ｉ）物种。反应后催化剂颗粒的分散程度明显提高     

A new polymorph of FeAlO3 at high pressure

Synchrotron X-ray diffraction measurements confirmed that a new polymorph of FeAlO3 could be synthesized at about 1800 K and 72 GPa. This phase can be indexed on an orthorhombic cell and transforms into the trigonal form on release of pressure. The c/a ratio of about 2.71 of the trigonal phase suggests corundum structure of FeAlO3 rather than LiNbO3 or ilmenite structure. This conclusion also suggests that the high-pressure orthorhombic phase could be the Rh2O3(II) structure rather than the GdFeO3-type perovskite structure.     

Bixbyite-type V2O3--a metastable polymorph of vanadium sesquioxide

A metastable polymorph of vanadium sesquioxide was prepared by the reaction of vanadium trifluoride with a water-saturated gaseous mixture of 10 vol % hydrogen in argon. The new polymorph crystallizes in the bixbyite-type structure. At temperatures around 823 K a transformation to the well-known corundum-type phase is observed. Quantum-chemical calculations show that the bixbyite-type structure is about 9 kJ/mol less stable than the known corundum-based one. This result, in combination with the absence of imaginary modes in the phonon density of states, supports the classification of the bixbyite-type phase as a metastable V(2)O(3) polymorph. At ~50 K a paramagnetic to canted antiferromagnetic transition is detected.     

A charge-stabilized Jahn-Teller Distortion of the Mixed Valence System NaBa2Cu3O6

The crystal structure of NaBa₂M₃O₆ contains an unusual hexagonal prism composed of linked MO₄ squares. This unit is distorted in the M = Cu compound but undistorted in the M = Ni material. Electronic structure calculations show an orbital degeneracy and electronic stabilization on distortion of the hexagonal prism at the electron count appropriate for the Cu compound. The preferred distortion is determined by considering how the nature of both the occupied and unoccupied metal d orbitals are consistent with the metal oxidation states set by the stoichiometry. The results provide added insights into the nature of mixed valence compounds. The synthesis of Na₂BaM₃O₆ is encouraged.     

Synthesis and characterisation of a new high pressure polymorph of Cu2WS4

In this communication we report the synthesis and structural characterisation of a new body centred polymorph of Cu2WS4 prepared using hydrothermal methods. I-Cu2WS4 crystallises in space group I42m with cell parameters a = b = 5.44427(8), c = 10.0687(2) A and has a new structure type containing layers of edge-sharing CuS4 and WS4 tetrahedra.     

A new polymorph of dichloridotriphenylantimony

In a new polymorphic form of dichloridotriphenylantimony, [Sb(C₆H₅)₃Cl₂], there are two crystallographically unique molecules in the asymmetric unit and it has been determined that this polymorph is one of two kinetically favoured phases of pure dichloridotriphenylantimony, both of which have Z′ > 1. A third polymorph, corresponding to (C₆H₅)₃SbCl_1.8F_0.2, is also known and has Z′ = 2. By contrast, the thermodynamically preferred polymorph of pure (C₆H₅)₃SbCl₂ has Z′ = 1. A brief comparison of the known polymorphic forms of dichloridotriphenylantimony is presented.     

A new polymorph of physcion

The structure of the title compound, 7‐methoxy‐2‐methyl‐4,5‐dihydroxyanthracene‐9,10‐dione, C₁₆H₁₂O₅, was originally reported by Ulickýet al. [Acta Cryst. (1991). C 47 , 1879–1881] in the space group P2₁2₁2₁ [polymorph (Io)]. The new polymorph, (Im), crystallizes in the space group P2₁/c. The molecular structures are closely similar, with both –OH groups forming intramolecular hydrogen bonds to one of the neighbouring quinone O atoms, thus slightly lengthening this C=O bond; the pattern of C—C bond lengths in the ring system is consistent with some contribution from a resonance form with a negative charge at the hydrogen‐bonded quinone O atom and an aromatic region around its neighbouring C atoms. The packing of (Im) is simpler than the extensively crosslinked pattern of (Io), with molecular tapes connected by classical (but three‐centre) and `weak' hydrogen bonds, parallel to [20].     

Structure and magnetic properties of Pb2Cu3B4O11: a new copper borate featuring [Cu3O8]10- units

Pb2Cu3B4O11 crystallizes in the monoclinic space group P2/n (No. 13) with a = 6.8016(15) A, b = 4.7123(10) A, c = 14.614(3) A, beta = 97.089(3) degrees, and Z = 2. The crystal structure consists of infinite [Cu3O8]10- zigzag chains of alternating dimers and monomers. The magnetic susceptibility and specific heat capacity show spin-gap and Curie-Weiss behaviors that can be explained by a model of Cu(2)-Cu(2) dimers and isolated or weakly coupled Cu(1) monomers.     

A new polymorph of tetraphenyldiboroxane

A new polymorph of tetraphenyldiboroxane [or oxybis(diphenylborane)], C₂₄H₂₀B₂O, (Ia), has been found. It is monoclinic, like the already known form, (Ib), and can be refined in the same space group, namely P2₁/c, or in the equivalent setting P2₁/n. The molecular conformations of the two polymorphs differ in the rotations of two of the phenyl rings about the B—C bonds, leading to markedly different packing patterns and cell dimensions.     

Cu_3B_2O_6/CuB_2O_4单晶的制备及其可见光催化降解亚甲基蓝

以醋酸铜/硝酸铜和硼酸为原料,柠檬酸作发泡剂,采用溶胶-凝胶法制得了高纯度的单晶结构硼酸铜(Cu3B2O6/CuB2O4).利用X射线衍射(XRD)、扫描电镜(SEM)、高分辨率透射电镜(HRTEM)、热重-差热分析(TGDTA)等对样品进行了表征,并考察了Cu3B2O6/CuB2O4在可见光(400 nmλ1100 nm)下对亚甲基蓝(MB)溶液的催化降解性能.结果表明,两种结构的硼酸铜都具有良好的光催化性能.当亚甲基蓝的初始浓度为50 mg·L-1,催化剂用量为1 g·L-1,光照6 h后,CuB2O4对亚甲基蓝的光催化降解率为63.36%,Cu3B2O6对亚甲基蓝的光催化降解率为99.52%.紫外-可见漫反射光谱(UV-Vis DRS)结果表明,Cu3B2O6的中间能态宽度为1.78 eV,小于CuB2O4的中间能态宽度(1.95 eV),且Cu3B2O6的禁带宽度较窄(Eg=2.34 eV),不仅可以发生价带顶与中间能态的电子跃迁,同时可以发生禁带间的电子跃迁,所以Cu3B2O6比CuB2O4具有更高的可见光催化性能.     

Radiothermoluminescence of polycrystalline high-temperature superconducting YBa2Cu3O6.94, EuBa2Cu3O6.9, and SmBa2Cu3O6.9 samples

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, p. 1934, August, 1991.     

A new polymorph of 2‐methyl‐6‐nitroaniline

A new crystal form of 2‐methyl‐6‐nitroaniline, C₇H₈N₂O₂, crystallizing with Z′ = 2 in the space group P2₁/c, has been identified during screening for salts and cocrystals. The different N—H...O hydrogen‐bonding synthons result in linear V‐shaped chains in the new polymorph, rather than the helical chain arrangement seen in the known form where Z′ = 1. The presence of a second component during crystallization appears to have determined the resultant crystal form of 2‐methyl‐6‐nitroaniline.     

Formation of tricuprotetraborate 3CuO · 2B2O3 · 6H2O in aqueous solutions

The reaction of copper sulfate, boric acid, and sodium hydroxide in an aqueous solution was studied in relation to the molar ratio and concentration of components, solution pH, temperature, and reaction duration. The conditions under which tricuprotetraborate hexahydrate 3CuO · 2B₂O₃ · 6H₂O is formed were determined.