In1.06Ho0.94Ge2O7: a thortveitite‐type compound

A new indium holmium digermanate, In_1.06Ho_0.94Ge₂O₇, with a thortveitite‐type structure, has been prepared as a polycrystalline powder material by high‐temperature solid‐state reaction. This new compound crystallizes in the monoclinic system (space group C2/c, No. 15). The structure was characterized by Rietveld refinement of powder laboratory X‐ray diffraction data. The In³⁺ and Ho³⁺ cations occupy the same octahedral site, forming a hexagonal arrangement on the ab plane. In their turn, the hexagonal arrangements of (In/Ho)O₆ octahedral layers are held together by sheets of isolated diortho groups comprised of double tetrahedra sharing a common vertex. In this compound, the Ge₂O₇ diortho groups lose the ideal D_3d point symmetry and also the C_2h point symmetry present in the thortveitite diortho groups. The Ge—O—Ge angle bridging the diortho groups is 160.2 (3)°, compared with 180.0° for Si—O—Si in thortveitite (Sc₂Si₂O₇). The characteristic mirror plane in the thortveitite space group (C2/m, No. 12) is not present in this new thortveitite‐type compound and the diortho groups lose the C_2h point symmetry, reducing to C₂.     

Ca7.96Cu0.04Ge5O18: a new calcium germanate with GeO4 and Ge3O10 units

The title compound, octa­calcium copper penta­germanium octa­deca­oxide, represents a new inter­mediate phase between CaO and GeO₂, and has not previously been reported in the literature. The structure consists of three different Ge sites, two of them on general 8d positions, site symmetry 1, one on special position 4d, site symmetry 2. Three of the five Ca sites occur on 8d positions, site symmtery 1, one Ca is on 4b with site symmetry and one Ca is on 4c with site symmetry 2. All nine O atoms have symmetry 1 (8d position). By sharing common edges, the Ca sites form infinite bands parallel to the c axis, and these bands are inter­connected by isolated GeO₄ and Ge₃O₁₀ units. These (100) layers are stacked along a in an ABAB… sequence, with the B layer being inverted and displaced along b/2.     

Cu(Cu0.44Cr4.56)Ge2O12: a close‐packed oxide with CuO4 tetra­hedra

The structure of copper(I,II) penta­chromium(III) germanate, Cu(Cu_0.44Cr_4.56)Ge₂O₁₂, contains one Cu position (m2m), one Ge position (m) and three Cr positions (2/m, m and 2). The close‐packed structure is described in terms of slabs of edge‐sharing Cr³⁺O₆ octa­hedra and isolated CuO₄ and GeO₄ tetra­hedra. These slabs are aligned parallel to the bc plane and are separated from each other by GeO₄ tetra­hedra along a. The tetra­hedral coordination observed for the Cu⁺/Cu²⁺ ions represents an unusual feature of the structure. The Cr—O and Cu—O bond lengths are compared with literature data.     

Ca3GeO4Cl2 with a norbergite‐like structure

The title compound, tricalcium monogermanate dichloride, is orthorhombic and consists of one distinct Ge site on special position 4c, site symmetry m, and two different Ca sites, Ca1 and Ca2, one on general position 8d, site symmetry 1, and the other on special position 4c. Two of the O atoms occupy the 4c position (symmetry m); the third O atom is situated on the general 8d position, symmetry 1, as is the one distinct Cl position. By sharing common edges, the distorted Ca1 octahedra form infinite crankshaft‐like chains parallel to the b direction. Along a and c, these chains are connected to one another via common corners, thereby forming a three‐dimensional framework of edge‐ and corner‐sharing Ca1O₄Cl₂ octahedra. Triangular prisms of Ca2O₄Cl₂ polyhedra and GeO₄ tetrahedra fill the interstitial space within the Ca1 polyhedral framework. Relationships between the structures of the title compound and the humite‐type materials norbergite (Mg₃SiO₄F₂) and Mn₃SiO₄F₂ are discussed.     

Chromium‐based clinopyroxene‐type germanates NaCrGe2O6 and LiCrGe2O6 at 298 K

The structure analyses of sodium chromium digermanate, NaCrGe₂O₆, (I), and lithium chromium digermanate, LiCrGe₂O₆, (II), provide important structural information for the clinopyroxene family, and form part of our ongoing studies on the phase transitions and magnetic properties of clinopyroxenes. (I) shows C2/c symmetry at 298 K, contains one Na, one Cr (both site symmetry 2 on special position 4e), one Ge and three O‐atom positions (on general positions 8f) and displays the well known clinopyroxene topology. The basic units of the structure of (I) are infinite zigzag chains of edge‐sharing Cr³⁺O₆ octahedra (M1 site), infinite chains of corner‐sharing GeO₄ tetrahedra, connected to the M1 chains by common corners, and Na sites occupying interstitial space. (II) was found to have P2₁/c symmetry at 298 K. The structure contains one Na, one Cr, two distinct Ge and six O‐atom positions, all on general positions 4e. The general topology of the structure of (II) is similar to that of (I); however, the loss of the twofold symmetry makes it possible for two distinct tetrahedral chains, having different conformation states, to exist. While sodium is (6+2)‐fold coordinated, lithium displays a pure sixfold coordination. Structural details are given and chemical comparison is made between silicate and germanate chromium‐based clinopyroxenes.     

Rhombohedral boron subnitride,B13N2, by X‐ray powder diffraction

The structure of the title compound consists of distorted B₁₂ icosahedra linked by N—B—N chains. The compound crystallizes in the rhombohedral space group Rm (No. 166). The unit cell contains four symmetry‐independent atom sites, three of which are occupied by boron [in the 18h, 18h (site symmetry m) and 3b (site symmetry m) Wyckoff positions] and one by nitrogen (in the 6c Wyckoff position, site symmetry 3m). Two of the B atoms form the icosahedra, while N atoms link the icosahedra together. The main feature of the structure is that the 3b position is occupied by the B atom, which makes the structure different from those of B₆O, for which these atom sites are vacant, and B_4+xC_1−x, for which this position is randomly occupied by both B and C atoms.     

Die Kristallstruktur von Ag2Ge2O5: Eine neuartige Gerüststruktur von Ge2O52−

Crystal Structure of Ag₂Ge₂O₅: A New Ge₂O₅^2? Network Structure Ag₂Ge₂O₅ was prepared from the binary oxides at high O₂ pressures. Single crystal X-ray diffraction work indicated monoclinic symmetry (P2₁/c; a = 1101.3(2); b = 1006.3(1); c = 1221.9(3) pm; ß = 94.6(1)°). The structure was determined by direct methods (3372 independent structure factors) and refined to a conventional R value of 0.084. A new Ge₂O₅^2? network structure was found with germanium coordinated octahedrally (­d(Ge—O) = 188,7 pm) and tetrahedrally (­d(Ge—O) = 175,9 pm), in equal proportions, by oxygen. The polyhedra share vertices and edges, thus forming a three dimensional channel system, which is occupied by Ag⁺ ions. The shortest Ag—Ag distance of 284 pm, like the pale yellow colour of the compound, indicates Ag⁺—Ag⁺ interaction.     

Two scandium–biuret complexes: [Sc(C2H5N3O2)(H2O)5]Cl3·H2O and [Sc(C2H5N3O2)4](NO3)3

The scandium(III) cations in the structures of pentaaqua(biuret‐κ²O,O′)scandium(III) trichloride monohydrate, [Sc(C₂H₅N₃O₂)(H₂O)₅]Cl₃·H₂O, (I), and tetrakis(biuret‐κ²O,O′)scandium(III) trinitrate, [Sc(C₂H₅N₃O₂)₄](NO₃)₃, (II), are found to adopt very different coordinations with the same biuret ligand. The roles of hydrogen bonding and the counter‐ion in the establishment of the structures are described. In (I), the Sc³⁺ cation adopts a fairly regular pentagonal bipyramidal coordination geometry arising from one O,O′‐bidentate biuret molecule and five water molecules. A dense network of N—H...Cl, O—H...O and O—H...Cl hydrogen bonds help to establish the packing, resulting in dimeric associations of two cations and two water molecules. In (II), the Sc³⁺ cation (site symmetry 2) adopts a slightly squashed square‐antiprismatic geometry arising from four O,O′‐bidentate biuret molecules. A network of N—H...O hydrogen bonds help to establish the packing, which features [010] chains of cations. One of the nitrate ions is disordered about an inversion centre. Both structures form three‐dimensional hydrogen‐bond networks.     

Cluster self-organization of germanate systems: Suprapolyhedral precursor clusters and self-assembly of K2Nd4Ge4O13(OH)4, K2YbGe4O10(OH), K2Sc2Ge2O7(OH)2, and KScGe2O6(PYR)

Geometric and topological analysis of all known types of K,TR germanates (TR = La-Lu, Y, Sc, In) is carried out with the use of computer techniques (the TOPOS 4.0 program package). Framework structures are represented as three-dimensional (3D) K,TR,Ge networks (graphs) with oxygen atoms removed. The following crystal-forming 2D TR,Ge networks are determined: for K₂Nd₄Ge₄O₁₃(OH)₄, this is TR 4 3 3 4 3 3 + T 4 3 4 3; for K₂YbGe₄O₁₀(OH), this is TR 6 6 3 6 + T 1 6 8 6 + T 2 3 6 8; for K₂Sc₂Ge₂O₇(OH)₂, this is TR 6 4 6 4 + T 6 4 6; and for KScGe₂O₆, TR 6 6 3 6 3 4 + T 1 6 3 6 + T 2 6 4 3. The full 3D reconstruction of the self-assembly mechanism of crystal structures is performed as follows: precursor cluster—primary chain—microlayer-microframework (supraprecursor). In K₂Nd₄Ge₄O₁₃(OH)₄, K₂Sc₂Ge₂O₇(OH)₂, and KScGe₂O₆, an invariant type of cyclic six-polyhedral precursor cluster is identified; this precursor clusters is built of TR octahedra, which are stabilized by atoms K. For K₂Nd₄Ge₄O₁₃(OH)₄, the type of cyclic four-polyhedral precursor cluster of tetrahedron-linked TR octatopes is identified. The cluster coordination number in a layer is six (the maximum possible value) only for anhydrous germanate KScGe₂O₆ (an analogue of pyroxene, PYR); in the other OH-containing germanates, this number is four. The mechanism of formation of Ge radicals in the form of groups Ge₂O₇ and Ge₄O₁₃, a chain GeO₃, and a tubular assembly of linked cyclic groups Ge₈O₂₀ is considered.     

Strontium magnesium phosphate,Sr2+xMg3−xP4O15 (x∼ 0.36), from laboratory X‐ray powder data

The previously unknown crystal structure of strontium magnesium phosphate, Sr_2+xMg_3−xP₄O₁₅ (x∼ 0.36), determined and refined from laboratory powder X‐ray diffraction data, represents a new structure type. The title compound was synthesized by high‐temperature solid‐state reaction and it crystallizes in the orthorhombic space group Cmcm. It was earlier thought to be stoichiometric Sr₂Mg₃P₄O₁₅, but our structural study indicates the nonstoichiometric composition. The asymmetric unit contains one Sr (site symmetry ..m on special position 8g), one M (= Mg 64%/Sr 36%; site symmetry 2/m.. on special position 4b), one Mg (site symmetry 2.. on special position 8e), two P (site symmetry m.. on special position 8f and site symmetry ..m on special position 8g), and six O sites [two on general positions 16h, two on 8g, one on 8f and one on special position 4c (site symmetry m2m)]. The nonstoichiometry is due to the mixing of magnesium and strontium ions on the M site. The structure consists of three‐dimensional networks of MgO₄ and PO₄ tetrahedra, and MO₆ octahedra with the other strontium ions occupying the larger cavities surrounded by ten O atoms. All the polyhedra are connected by corner‐sharing except the edge‐sharing MO₆ octahedra forming one‐dimensional arrangements along [001].     

Similarities and differences in the structures of 5‐bromo‐6‐hydroxy‐7,8‐dimethylchroman‐2‐one and 6‐hydroxy‐7,8‐dimethyl‐5‐nitrochroman‐2‐one

The title compounds, C₁₁H₁₁BrO₃, (I), and C₁₁H₁₁NO₅, (II), respectively, are derivatives of 6‐hydroxy‐5,7,8‐trimethylchroman‐2‐one substituted at the 5‐position by a Br atom in (I) and by a nitro group in (II). The pyranone rings in both molecules adopt half‐chair conformations, and intramolecular O—H...Br [in (I)] and O—H...O_nitro [in (II)] hydrogen bonds affect the dispositions of the hydroxy groups. Classical intermolecular O—H...O hydrogen bonds are found in both molecules but play quite dissimilar roles in the crystal structures. In (I), O—H...O hydrogen bonds form zigzag C(9) chains of molecules along the a axis. Because of the tetragonal symmetry, similar chains also form along b. In (II), however, similar contacts involving an O atom of the nitro group form inversion dimers and generate R₂²(12) rings. These also result in a close intermolecular O...O contact of 2.686 (4) Å. For (I), four additional C—H...O hydrogen bonds combine with π–π stacking interactions between the benzene rings to build an extensive three‐dimensional network with molecules stacked along the c axis. The packing in (II) is much simpler and centres on the inversion dimers formed through O—H...O contacts. These dimers are stacked through additional C—H...O hydrogen bonds, and further weak C—H...O interactions generate a three‐dimensional network of dimer stacks.     

Two (+)‐α,4‐dimethyl‐2‐oxocyclo­hexaneacetic acids: hydrogen bonding in a terpenoid γ‐keto acid and in a diastereomeric lactol

The (+)‐(αS,1S,4R)‐diastereomer of the title structure, C₁₀H₁₆O₃, aggregates in the solid as non‐symmetric dimers with disorder in both carboxyl groups [O·O = 2.710 (5) and 2.638 (5) Å]. The two mol­ecules constituting the asymmetric unit pair around a pseudo‐twofold rotational axis and differ only slightly in their distances and angles, but one methyl group displays rotational disorder absent in the other mol­ecule. Five inter­molecular C—H·O close contacts exist, involving both ketone groups. The (+)‐(αR,1R,4R)‐diastereomer exists in the crystal in its closed‐ring lactol form, (3R,3aR,6R,7aR)‐2,3,3a,4,5,6,7,7a‐octa­hydro‐7a‐hydroxy‐3,6‐dimethyl­benzo[b]furan‐2‐one, C₁₀H₁₆O₃, and aggregates as hydrogen‐bonded catemers that extend from the hydroxyl group of one mol­ecule to the carbonyl group of a neighbor screw‐related along b [O·O = 2.830 (3) Å and O—H·O = 169°]. One close inter­molecular C—H·O contact exists involving the carbonyl group.     

Synthesis, crystal structure, and preliminary study of luminescent properties of InTbGe2O7

A new indium terbium germanate InTbGe₂O₇, which is a member of the thortveitite family, was prepared as a polycrystalline powder material by high-temperature solid-state reaction. This new compound crystallizes in the monoclinic system, space group C2/c (No. 15), with unit cell parameters a=6.8818(2) Å, b=8.8774(3) Å, c=9.7892(4) Å, β=101.401(1)°, V=586.25(4) ų and Z=4. Its structure was characterized by Rietveld refinement of powder laboratory X-ray diffraction data. It consists of octahedral sheets that are held together by sheets of isolated Ge₂O₇ diorthogroups composed of two tetrahedra sharing a common vertex. It contains only one octahedral site occupied by In³⁺ and Tb⁺³ cations. The characteristic mirror plane in the thortveitite (Sc₂Si₂O₇) space group (C2/m, No. 12) is not present in this new compound. Besides, in InTbGe₂O₇, the Ge–O–Ge angle bridging two diorthogroups is 156.8(2)° as compared to the one in thortveitite, which is 180°. On the other hand, luminescent properties were observed when it is excited with 376.5 nm wavelength. The luminescence spectrum shows typical transitions from the ⁵D₄ multiplet belonging to the trivalent terbium ion.     

Hydrogen‐bonded bilayers in ­piperazinium(2+) bis(mandelate) bis(methanol) solvate

In the title compound, C₄H₁₂N₂²⁺·2C₈H₇O₃^?·2CH₄O, the cations lie across centres of inversion and are disordered over two orientations with equal occupancy; there are equal numbers of (R)‐ and (S)‐mandelate anions present (mandelate is α‐hydroxy­benzene­acetate). The anions and the neutral water mol­ecules are linked by O—H?O hydrogen bonds [O?O 2.658 (3) and 2.682 (3) Å, and O—H?O 176 and 166°] into deeply folded zigzag chains. Each orientation of the cation forms two symmetry‐related two‐centre N—H?O hydrogen bonds [N?O 2.588 (4) and 2.678 (4) Å, and N—H?O 177 and 171°] and two asymmetric, but planar, three‐centre N—H?(O)₂ hydrogen bonds [N?O 2.686 (4)–3.137 (4) Å and N—H?O 137–147°], and by means of these the cations link the anion/water chains into bilayers.     

Na2Ge3P3 and Na5Ge7P5 Comprising Heteroatomic Polyanions Mimicking the Structure of Fibrous Red Phosphorus

Recently lithium phosphidogermanates were discovered as fast lithium ion conductors for potential usage as solid electrolytes in all solid-state batteries. In this context we also studied sodium phosphidogermanates since sodium ion conductors are of equal interest. Na₂Ge₃P₃ and Na₅Ge₇P₅ both crystallize in the monoclinic space group C2/m with unit cell parameters of a = 17.639(4) Å, b = 3.6176(7) Å, c = 11.354(2) Å, β = 92.74(3)° and a = 16.168(5) Å, b = 3.6776(7) Å, c = 12.924(4) Å, β = 91.30(3)°, respectively. Both show linearly condensed 9-atom cages of four Ge / five P and five Ge / four P atoms, respectively. These cages contain Ge–Ge bonds and form one-dimensional tubes by sharing three atoms. The parallel tubes are paired through further Ge–Ge bonds. Both structures are closely related to the one of the fibrous type of crystalline red phosphorus. A comparison with other compounds such as NaGe₃P₃ and GeP reveals recurring structural motifs with a broad variety of connection patterns. According to the general formula Na_4+xGe_6+xP_6–x with x = 0 and 1, the two novel structures hint for the possibility of a variable Na content which might allow Na ion mobility.     

Effect of GeIon on Electrical Properties of (La0.1Ca0.9)(Mn1−xGex)O3

Orthorhombic perovskite-type (La_0.1Ca_0.9)(Mn_1−xGe_x)O₃was synthesized in the range (0.00≤x≤0.10). Since the ionic radius of the Ge⁴⁺ion is equal to that of the Mn⁴⁺ion, the (Mn, Ge)–O(1, 2) distances and the angles for (Mn, Ge)–O(1, 2)–(Mn, Ge) are independent of the composition (x). From the measurement of the electrical resistivity (ρ), all manganates exhibit a metal–insulator transition. With increasingx, the metal–insulator transition temperature (T_t) increases anddρ/dTdecreases. The cation–anion–cation overlap integrals are weakened by the Ge⁴⁺ion.     

A new polymorph of barium chloro­anilate trihydrate

Single crystals of a new polymorph of the title compound, barium(II) 3,6-di­chloro-2,5-di­hydroxy-1,4-benzo­quinone tri­hydrate, Ba²⁺·C₆Cl₂O₄²⁻·3H₂O, have been grown in sodium metasilicate gel. Each Ba²⁺ cation is coordinated by eight O atoms. The Ba²⁺ cations are bridged by an O atom of a ligand around the centre of symmetry at Wyckoff position 4a and by the O atom of a water mol­ecule around the centre of symmetry at Wyckoff position 4b, forming a sheet parallel to the (100) plane. Loose contacts are found around one of the water mol­ecules, as observed in the Cmca form.     

Determination des structures de deux ferrites mixtes nouveaux de formule BaLa2Fe2O7 et SrTb2Fe2O7

The structures of the two new ferrites BaLa₂Fe₂O₇ and SrTb₂Fe₂O₇ with tetragonal symmetry have been resolved by X-ray and neutron diffraction performed on powder samples. In both compounds the arrangement of atoms present a close resemblance with the idealized Sr₃Ti₂O₇ structure. It consists of a packing along the c axis of two different blocks. One is formed by the adjunction of two perovskite cells and the other one by a halved rocksalt Sr(Ba)O cell. The iron cation lattice is built by infinite double layers perpendicular to the c axis with the shortest Fe³⁺Fe³⁺ distances inside the double layers much shorter than between the layers. In BaLa₂Fe₂O₇, Ba²⁺ is located on a regular 12-coordinated site and La³⁺ in a regular 9-coordinated polyhedron. Fe³⁺ is surrounded by five oxygen neighbours at 1.98 Å, building a rather regular tetragonal pyramid, with a sixth oxygen at 2.25 Å. In SrTb₂Fe₂O₇, Sr has only eight close neighbours at ～2.80 Å and four more distant at 3.15 Å. Tb³⁺ has seven close neighbours, six building a distorted octahedron with the largest triangular face capped by the seventh oxygen. Fe³⁺ again has five neighbours, but due to the lowering of the symmetry, the square pyramid has become a distorted trigonal bipyramid.     

β‐Y2Si2O7, a new thortveitite‐type compound,determined at 100 and 280 K

A new form of Y₂Si₂O₇ (diyttrium heptaoxodisilicate) has been synthesized which is isotypic with thortveitite, Sc₂Si₂O₇, and crystallizes in the centrosymmetric space group C2/m, both at 100 and 280 K. The Y³⁺ cation occupies a distorted octahedral site, with Y—O bond lengths in the range 2.239 (2)–2.309 (2) Å. The SiO₄ tetrahedron is remarkably regular, with Si—O bond lengths in the range 1.619 (2)–1.630 (2) Å. The bridging O atom of the Si₂O₇ pyrosilicate group shows a large anisotropic displacement perpendicular to the Si—O bond. Changes in lattice and structural parameters upon cooling are small with, however, a distinct decrease of the anisotropic displacement of the briding O atom. Structure solution and refinement in the non‐centrosymmetric space group C2 are possible but do not yield a significantly different structure model. The Si—O—Si bond angle of the isolated Si₂O₇ groups is 179.2 (1)° at 280 K in C2 and 180° per symmetry in C2/m. The C2/m structure model is favoured.     

Lithium barium silicate,Li2BaSiO4, from synchrotron powder data

The structure of lithium barium silicate, Li₂BaSiO₄, has been determined from synchrotron radiation powder data. The title compound was synthesized by high‐temperature solid‐state reaction and crystallizes in the hexagonal space group P6₃cm. It contains two Li atoms, one Ba atom (both site symmetry ..m on special position 6c), two Si atoms [on special positions 4b (site symmetry 3..) and 2a (site symmetry 3.m)] and four O atoms (one on general position 12d, and three on special positions 6c, 4b and 2a). The basic units of the structure are (Li₆SiO₁₃)⁵⁻ units, each comprising seven tetrahedra sharing edges and vertices. These basic units are connected by sharing corners parallel to [001] and through sharing (SiO₄)⁴⁻ tetrahedra in (001). The relationship between the structures and luminescence properties of Li₂SrSiO₄, Li₂CaSiO₄ and the title compound is discussed.