High‐temperature phase of trans‐tetra­aqua­bis­(tri­fluoro­acetato‐O)­manganese(II)

The title compound, [Mn(CF₃COO)₂(H₂O)₄], crystallizes in the monoclinic space group C2/c. At about 215 K, it undergoes a reversible phase transition, which leads to crystal twinning. The crystal structure of the high‐temperature phase was determined at 220 K. The Mn²⁺ ion lies on a twofold axis and is octahedrally coordinated by two monodentate tri­fluoro­acetate ligands in apical positions and by four equatorial aqua ligands, two of which lie on the twofold axis. Hydro­gen‐bonding interactions connect the complex mol­ecules, generating a three–dimensional network.     

Magnetic Study of OrthomanganitesA1−xMnO3+y(A=La, Eu) with the Perovskite Structure

The crystal structure and magnetic properties of orthomanganitesA_1−xMnO_3+y(A=La, Eu;x≤0.2;y≤0.13) were investigated. It was shown that the increase of oxygen content leads to the transformation from the weak ferromagnetic to the ferromagnetic state in these compounds. The Curie temperatures of La_1−xMnO_3+yand freezing temperatures of magnetic clusters for Eu_1−xMnO_3+yin the samples with a deficit ofAcations are higher than those in parent compounds (withx=0). A mixed magnetic state involving ferro- and antiferromagnetic domains is suggested in the intermediate range ofx,yvalues. Arguments are presented to support the assumption that the magnetic properties in the lightly doped insulating regime are governed by superexchange via anions rather than by exchange via charge carriers.     

HgWO4 synthesized at high pressure and temperature

Crystals of mercury(II) tungstate(VI), HgWO₄, were grown in sealed gold tubes under an Ar atmosphere at 300 MPa and 973 K. The monoclinic crystal structure (C2/c) of HgWO₄ consists of zigzag chains of edge‐sharing WO₆ octahedra running along the c axis and layers of very distorted corner‐sharing HgO₆ octahedra in the bc plane. The Hg atom lies on an inversion centre and the W atom is on a twofold axis. No structural effects which can be ascribed to the high pressure used in the synthesis were found.     

catena‐Poly­[[(nitrato‐κ2O,O′)silver(I)]‐μ‐2,2′‐[1,4‐phenyl­enebis­(methyl­ene­thio)]­bis(5‐methyl‐1,3,4‐thia­diazo­le)‐κ2N3:N3′]

In the title complex, [Ag(NO₃)(C₁₄H₁₄N₄S₄)]_n, the Ag^I atom lies on a twofold axis and shows a distorted tetrahedral coordination, comprised of two N‐atom donors from two thia­diazole groups of separate ligands and two O‐atom donors from one nitrate ligand. Each bis­(thio­ether) ligand also lies on a twofold axis and bridges two adjacent Ag atoms to form an infinite chain along the c axis, with an Ag⋯Ag separation of 11.462 (4) Å. Adjacent one‐dimensional chains are further linked into double‐chain motifs through weak Ag⋯S and π–π stacking interactions.     

Poly­[[copper(II)‐di‐μ‐5‐amino­isophthalato(1–)‐κ4N:O] monohydrate]

The title compound, {[Cu(C₈H₆NO₄)₂]·H₂O}_n, was prepared by the hydro­thermal assembly of 5‐amino­isophthalic acid with copper nitrate. Single‐crystal X‐ray analysis shows that it has a two‐dimensional layer coordination framework, in which the unique Cu atom lies on an inversion centre and adopts a square‐planar geometry, coordinated to two N and two O atoms from symmetry‐related ligands. The water molecule lies on a twofold axis and there are hydrogen‐bonding interactions between the layers.     

Isomorphism in 1‐(2‐halidobenzyl)‐4‐[(E)‐2‐(3‐hydroxyphenyl)ethenyl]pyridinium halide hemihydrates (halide = Cl,Br)

The crystal structures of two (E)‐stilbazolium salts, namely 1‐(2‐chlorobenzyl)‐4‐[(E)‐2‐(3‐hydroxyphenyl)ethenyl]pyridinium chloride hemihydrate, C₂₀H₁₇ClNO⁺·Cl⁻·0.5H₂O, (I), and 1‐(2‐bromobenzyl)‐4‐[(E)‐2‐(3‐hydroxyphenyl)ethenyl]pyridinium bromide hemihydrate, C₂₀H₁₇BrNO⁺·Br⁻·0.5H₂O, (II), are isomorphous; the isostructurality index is 99.3%. In both salts, the azastyryl fragments are almost planar, while the rings of the benzyl groups are almost perpendicular to the azastyryl planes. The building blocks of the structures are twofold symmetric hydrogen‐bonded systems of two cations, two halide anions and one water molecule, which lies on a twofold axis. In the crystal structure, these blocks are connected by means of weaker interactions, viz. van der Waals, weak hydrogen bonding and stacking. This study illustrates the robustness of certain supramolecular motifs created by a spectrum of intermolecular interactions in generating these isomorphous crystal structures.     

Molybdenum Substitution for Improving the Charge Compensation and Activity of Li2MnO3

Lithium‐rich layer‐structured oxides xLi₂MnO₃? (1?x)LiMO₂ (0<x<1, M=Mn, Ni, Co, etc.) are interesting and potential cathode materials for high energy‐density lithium ion batteries. However, the characteristic charge compensation contributed by O^2? in Li₂MnO₃ leads to the evolution of oxygen during the initial Li⁺ ion extraction at high voltage and voltage fading in subsequent cycling, resulting in a safety hazard and poor cycling performance of the battery. Molybdenum substitution was performed in this work to provide another electron donor and to enhance the electrochemical activity of Li₂MnO₃‐based cathode materials. X‐ray diffraction and adsorption studies indicated that Mo⁵⁺ substitution expands the unit cell in the crystal lattice and weakens the Li?O and Mn?O bonds, as well as enhancing the activity of Li₂MnO₃ by lowering its delithiation potential and suppressing the release of oxygen. In addition, the chemical environment of O^2? ions in molybdenum‐substituted Li₂MnO₃ is more reversible than in the unsubstituted sample during cycling. Therefore molybdenum substitution is expected to improve the performances of the Li₂MnO₃‐based lithium‐rich cathode materials.     

Bis­[N‐(6‐amino‐3,4‐di­hydro‐3‐methyl‐5‐nitro­so‐4‐oxopyrimidin‐2‐yl)­glycyl­glycinato]­tri­aqua­calcium: ­coordination polymer chains linked by hydrogen bonds

In the title compound, [Ca(C₉H₁₁N₆O₅)₂(H₂O)₃], the Ca atom lies on a twofold rotation axis in C2/c and the three water mol­ecules are all disordered, each over two sites having equal occupancy. The anion acts as a bridging ligand between pairs of Ca sites on the same twofold axis, thus forming a one‐dimensional coordination polymer, with the chains lying along the twofold axes. These chains are linked by multiple O—H?O and N—H?O hydrogen bonds into a single three‐dimensional framework.     

Lithium and beryllium hypophosphites

The structures of monoclinic (C2/m) lithium di­hydrogenphosphate, LiH₂PO₂, and tetragonal (P4₁2₁2) beryllium bis(di­hydrogenphosphate), Be(H₂PO₂)₂, have been determined by single‐crystal X‐ray diffraction. The structures consist of layers of hypophosphite anions and metal cations in tetrahedral coordination by O atoms. Within the layers, the anions bridge four Li⁺ and two Be²⁺ cations, respectively. In LiH₂PO₂, the Li atom lies on a twofold axis and the H₂PO₂⁻ anion has the PO₂ atoms on a mirror plane. In Be(H₂PO₂)₂, the Be atom lies on a twofold axis and the H₂PO₂⁻ anion is in a general position.     

Tetra‐n‐butylammonium bis(2‐thioxo‐1,3‐dithiole‐4,5‐dithiolato‐κ2S4,S5)nickelate(III)

The crystal structure of the title compound, (C₁₆H₃₆N)[Ni(C₃S₅)₂], is isomorphous with that of the corresponding Pt complex but different from the structures reported for compounds of the same chemical composition, and so provides a new crystalline phase of this complex. The nickel complex anion has good planarity and lies on a crystallographic inversion centre. There is disorder in the two terminal C atoms of two of the butyl chains of the tetra‐n‐butyl­ammonium cation, the N atom of which is located on a twofold axis.     

Real time study of hybrid sol-gel photopolymerization by UV light

Polycrystalline La_0.67 (Sr_1-x Cd _x )_0.33MnO₃ (LSCMO x = 0, 1/8, 2/8, 3/8, 4/8) films were fabricated on Si(100) single crystal substrates by the sol–gel and the rapid annealing process. According to the field-emission scan electron microscopy (FE-SEM) observation and X-ray (XRD) diffraction studies, all the samples are single phase. We also prepared a series of samples by fixing the ratio of La at 0.67. It is shown that with increase of the doping amount x in La_0.67(Sr_1-x Cd _x )_0.33MnO₃, the average A-site cation radius 〈A〉 decreases, the temperature of metal-insulator transition (T_MI) decreases monotonically, ρ and magnetoresistance (MR) values increase dramatically, which can be explained by the lattice effects. The enhanced MR effect at low temperature for the LSCMO film is attributed to the suppression of the spin dependent scattering of polarized electrons at the grain boundaries. The low-field magnetoresistance values under 0.3 T are observed to be 2.48% (x = 0) at 300 K and 37.5% (x = 4/8) at 85 K, respectively.     

catena‐Poly[bis(ethane‐1,2‐diammonium) [manganese(II)‐di‐μ‐phosphato‐κ4O:O′]]: a one‐dimensional manganese phosphate

The title compound, {(C₂H₁₀N₂)₂[Mn(PO₄)₂]}_n, contains anionic square‐twisted chains of formula [Mn(PO₄)₂]⁴⁻ constructed from corner‐sharing four‐membered rings of alternating MnO₄ and PO₄ units. The Mn and P atoms have distorted tetrahedral coordination and the Mn atom lies on a twofold axis. The linear manganese–phosphate chains are held together by hydrogen‐bonding interactions involving the framework O atoms and the H atoms of the ethane‐1,2‐diammonium cations, which lie in the interchain spaces.     

Aqua(4,4′‐oxy­dibenzoato‐κO)­cadmium(II)

The Cd atom in the polymeric title compound, [Cd(C₁₄H₈O₅)(H₂O)]_n, is linked to four carboxyl O atoms and a water mol­ecule in a five‐coordinate coordination polyhedron that is midway between a square pyramid and a trigonal bipyramid. The Cd atom and the water molecules both lie on the same twofold axis and the central O atom of the 4,4′‐oxydibenzoate moiety lies on another twofold axis. Covalent Cd—O bonds lead to the formation of a layer architecture perpendicular to the twofold axis, the layers being held together by hydrogen bonds in the third direction.     

A novel heterocyclic compound: catena‐poly[[[diaquasodium(I)]‐di‐μ‐aqua] hemi(1,5‐dihydroxy‐4,8,9‐trioxa‐2,6‐diazabicyclo[3.3.1]nona‐2,6‐diene‐3,7‐diolate)]

In the title compound, {[Na(H₂O)₄]₂(C₄H₂N₂O₇)}_n, the 1,5‐dihydroxy‐4,8,9‐trioxa‐2,6‐diazabicyclo[3.3.1]nona‐2,6‐diene‐3,7‐diolate anion lies across a twofold axis in the space group C2/c; there are two independent Na sites, one on a twofold axis and the other on a centre of inversion. Hydrogen bonds link the {[Na(H₂O)₄]⁺}_n chains and diolate anions into a three‐dimensional framework.     

cis‐Dicarbonyl‐cis‐dichlorido‐trans‐bis(triphenylphosphine‐κP)iridium(III) tetrafluoridoborate,formed by reaction of (cycloocta‐1,5‐diene)bis(triphenylphosphine)iridium tetrafluoridoborate with carbonyl fluoride in dichloromethane solution

The reaction between carbonyl fluoride and [Ir(COD)(PPh₃)₂]BF₄ (COD is cycloocta‐1,5‐diene) in dichloromethane solution affords the novel title iridium salt, [IrCl₂(C₁₈H₁₅P)₂(CO)₂]BF₄. The cation lies across a twofold rotation axis in the space group P2₁2₁2 and its structure confirms the presence in a cis relationship of two metal‐bound chlorides, while the phosphine ligands occupy a trans pair of sites. The anion also lies across a twofold rotation axis, and the F atoms are disordered over two sets of sites.     

Rubidium dimolybdate,Rb2Mo2O7, and caesium dimolybdate,Cs2Mo2O7

The crystal structures of dirubidium hepta­oxodimolybdate, Rb₂Mo₂O₇, and dicaesium hepta­oxodimolybdate, Cs₂Mo₂O₇, in the space groups Ama2 and P2₁/c, respectively, have been determined for the first time by single‐crystal X‐ray diffraction. The structures represent two novel structure types of monovalent ion dimolybdates, A₂Mo₂O₇ (A = alkaline elements, NH₄, Ag or Tl). In the structure of Rb₂Mo₂O₇, Mo atoms are on a twofold axis, on a mirror plane and in a general position. One of the Rb atoms lies on a twofold axis, while three others are on mirror planes. Two O atoms attached to the Mo atom on a mirror plane are located on the same plane. Rubidium dimolybdate contains a new kind of infinite Mo–O chain formed from linked MoO₄ tetra­hedra and MoO₆ octa­hedra alternating along the a axis, with two terminal MoO₄ tetra­hedra sharing corners with each octa­hedron. The chains stack in the [001] direction to form channels of an approximately square section filled by ten‐coordinate Rb ions. Seven‐ and eight‐coordinate Rb atoms are located between chains connected by a c translation. In the structure of Cs₂Mo₂O₇, all atoms are in general positions. The MoO₆ octa­hedra share opposite corners to form separate infinite chains running along the c axis and strengthened by bridging MoO₄ tetra­hedra. The same Mo–O polyhedral chain occurs in the structure of Na₂Mo₂O₇. Eight‐ to eleven‐coordinate Cs atoms fill the space between the chains. The atomic arrangement of caesium dimolybdate has an ortho­rhom­bic pseudosymmetry that suggests a possible phase transition P2₁/c→Pbca at elevated temperatures.     

Bis(2‐amino­pyridine‐N)­bis­(benzoato‐O)­zinc

The crystal structure of the title compound, [Zn‐(C₇H₅O₂)₂(C₅H₆N₂)₂], is built of monomeric [Zn(2‐apy)₂(OBz)₂] mol­ecules (apy is amino­pyridine and OBz is benzoate). The Zn atom lies on a twofold symmetry axis and adopts a slightly distorted tetrahedral coordination. The Zn?O distances to the non‐coordinated O atoms are long at 2.872 (3) Å. Each non‐ligating carbonyl O atom of the benzoate anion accepts one intramolecular and one intermolecular hydrogen bond from the amino group. The mol­ecules form a chain along the c axis through intermolecular N—H?O hydrogen bonds between the amino and carboxyl groups.     

1,2‐Di­benzoyl­hydrazine

In the crystal structure of the title compound, C₁₄H₁₂N₂O₂, the molecule lies about a twofold axis; two carbonyl groups and the H atoms of the N—N bond are in a trans orientation with respect to each other. In the crystal, each mol­ecule is linked to the other and viceversa by intermolecular N—H?O hydrogen bonds between the amide hydrogen and the O atoms of neighbouring mol­ecules to form two ten‐membered rings, each of which has the graph‐set motif C4R(10). This extends as a polymeric chain along the c axis.     

Selective Alkane Oxidation by Manganese Oxide: Site Isolation of MnOx Chains at the Surface of MnWO4 Nanorods

The electronic and structural properties of vanadium‐containing phases govern the formation of isolated active sites at the surface of these catalysts for selective alkane oxidation. This concept is not restricted to vanadium oxide. The deliberate use of hydrothermal techniques can turn the typical combustion catalyst manganese oxide into a selective catalyst for oxidative propane dehydrogenation. Nanostructured, crystalline MnWO₄ serves as the support that stabilizes a defect‐rich MnO_x surface phase. Oxygen defects can be reversibly replenished and depleted at the reaction temperature. Terminating MnO_x zigzag chains on the (010) crystal planes are suspected to bear structurally site‐isolated oxygen defects that account for the unexpectedly good performance of the catalyst in propane activation.     

Synthesis,Crystal Structure and Properties of RbMnO2

RbMnO₂ was prepared via the azide/nitrate route. Stoichiometric mixtures of the precursers (Mn₂O₃, RbN₃ and RbNO₃) were heated in a special regime up to 600 °C and annealed at this temperature for 30 h in specially designed silver crucibles. Single crystals have been grown by annealing a 1:1 mixture of Rb₂O and MnO_x at 585 °C for 1200 h. According to the crystal structure determination Mn³⁺ is in a square‐pyramidal coordination by oxygen. These [MnO₅] units form double chains extending along the crystallographic c‐axis. RbMnO₂ shows Curie‐Weiss behaviour down to ～ 100 K. A fit of the susceptibility data yields an average value of the magnetic moment (per manganese atom) of μ_eff = 5.33 μ_B, and θ_p = –820 K. At 50 K and low field strength onset of ferromagnetic order due to spin canting has been observed.