Refinement of the crystal structure of Zn-containing greifensteinite

The crystal structure of Zn-containing greifensteinite from the Pirineus Mine (Minas Gerais, Brazil) was refined (R = 0.045, 562 reflections with |F| > 2σ(F)). The unit-cell parameters are a = 15.941(3) Å, b = 11.877(3) Å, c = 6.625(2) Å, β = 95.09(2)°; V = 1249.4 ų; sp. gr. C2/c; and Z = 2. The idealized formula is [Mn(Fe²⁺, Zn)₄]Ca₂Be₄(PO₄)₆(OH)₄ · 6H₂O. The mineral is isostructural with the previously studied monoclinic representatives of the roscherite group from different deposits and differs from these representatives in that it contains Zn in one of two octahedral positions.     

Investigation of the crystallization features,atomic structure,and microstructure of chromium-doped monticellite

A series of Cr⁴⁺:CaMgSiO₄ single crystals is grown using floating zone melting, and their microstructure, composition, and crystal structure are investigated. It is shown that regions with inclusions of second phases, such as forsterite, akermanite, MgO, and Ca₄Mg₂Si₃O₁₂, can form over the length of the sample. The composition of the single-phase regions of the single crystals varies from the stoichiometric monticellite CaMgSiO₄ to the solid solution Ca_{(1 ? x)}Mg_{(1 + x)}SiO₄(x = 0.22). The Cr:(Ca_0.88Mg_0.12)MgSiO₄ crystal is studied using X-ray diffraction. It is revealed that, in this case, the olivine-like orthorhombic crystal lattice is distorted to the monoclinic lattice with the parameters a = 6.3574(5) Å, b = 4.8164(4) Å, c = 11.0387(8) Å, β = 90.30(1)^o, Z = 4, V = 337.98 ų, and space group P2₁/c. In the monoclinic lattice, the M(1) position of the initial olivine structure is split into two nonequivalent positions with the center of symmetry, which are occupied only by Mg²⁺ cations with the average length of the Mg-O bond R _av = 2.128 Å. The overstoichiometric Mg²⁺ cations partially replace Ca²⁺ cations (in the M(2) position of the orthorhombic prastructure) with the average bond length of 2.347 Å in the [(Ca,Mg)-O₆] octahedron. The average distance in SiO₄ distorted tetrahedra is 1.541 Å.     

Pyroxenoids of pyroxmangite–pyroxferroite series from xenoliths of Bellerberg paleovolcano (Eifel,Germany): Chemical variations and specific features of cation distribution

The pyroxferroite and pyroxmangite from xenoliths of aluminous gneisses in the alkaline basalts of Bellerberg paleovulcano (Eifel, Germany) have been studied by electron-probe and X-ray diffraction methods and IR spectroscopy. The parameters of the triclinic unit cells are found to be a = 6.662(1) Å, b = 7.525(1) Å, c = 15.895(2) Å, α = 91.548(3)°, β = 96.258(3)°, and γ = 94.498(3)° for pyroxferroite and a = 6.661(3) Å, b = 7.513(3) Å, c = 15.877(7) Å, α = 91.870(7)°, β = 96.369(7)°, and γ = 94.724(7)° for pyroxmangite; sp. gr. \(P\overline 1 \). The crystallochemical formulas (Z = 2) are, respectively, ^M(1–2)(Mn_0.5Ca_0.4Na_0.1)₂^M(3–6)(Fe, Mn)₄^M7[Mg_0.6(Fe, Mn)_0.4][Si₇O₂₁] and ^M(1–3)(Mn, Fe)₃^M(4–6)[(Fe, Mn)_0.7Mg_0.3]₃^M7[Mg_0.5(Fe, Mn)_0.5][Si₇O₂₁]. For these and previously studied representatives of the pyroxmangite structural type, an analysis of the cation distribution over sites indicates wide isomorphism of Mn²⁺, Fe²⁺, and Mg in all cation M(1–7) sites and the preferred incorporation of Сa and Na into large seven-vertex M1O₇ and M2O₇ polyhedra and Mg into the smallest five-vertex M7O₅ polyhedron.     

Refined structure of afwillite from the northern Baikal region

The crystal structure of the mineral afwillite [Ca₁₂(H₂O)₈][SiO₄]₄[SiO₂(OH)₂]₄ from the northern Baikal region was refined in a triclinic unit cell with the following parameters: a = 16.330(2) Å, b = 5.6389(6) Å, c = 11.685(1) Å, α = 90.08(1)°, β = 126.446(2)°, γ = 89.95(1)°, and sp. gr. P1. The triclinic unit cell is related to the monoclinic unit cell determined earlier (sp. gr. Cc, a = 16.278(1) Å, b = 5.6321(4) Å, c = 13.236(1) Å, and β = 134.898(3)°) by the transformation matrix [?100/010/101]. The structural model was determined using the phase-correction procedure and refined anisotropically to R = 2.8% based on 3270 independent reflections with F > 3σ(F). The crystal-chemical formula of afwillite was revised. The characteristic features of the IR spectrum of afwillite were explained based on the structural data.     

The Fe<Superscript>2+</Superscript>/Fe<Superscript>3+</Superscript> ratio in natural and heat-treated iron-rich eudialytes

The structures of natural iron-rich eudialyte (specimen 3458 from the Khibiny massif, the Kola Peninsula) and two heat-treated samples of this mineral calcined at 700 and 800°C were determined by X-ray diffraction. The trigonal unit-cell parameters (sp. gr. R3m) are as follows: a = 14.2645(1) Å, c = 29.9635(5) Å; a = 14.1307(1) Å, c = 30.1229(3) Å; a = 14.1921(2) Å, c = 30.2417(5) Å, respectively. It was found that Fe³⁺ ions in the calcined eudialytes, as well as impurities in the starting specimen, occupy the square-pyramidal Fe³⁺(V) sites, whereas Fe²⁺ ions are in the planar-tetragonal Fe²⁺(IV) sites.     

Crystal structure and microtwinning of monoclinic La<Subscript>3</Subscript>SbZn<Subscript>3</Subscript>Ge<Subscript>2</Subscript>O<Subscript>14</Subscript> crystals of the langasite family

The crystal structure of monoclinic La₃SbZn₃Ge₂O₁₄ crystals from the langasite family is determined by X-ray diffraction analysis [a = 5.202(1) Å, b = 8.312(1) Å, c = 14.394(2) Å, β = 90.02(1)°, sp. gr. A2, Z = 2, and R/R _w = (5.2/4.6)%]. The structure is a derivative of the Ca₃Ga₂Ge₄O₁₄-type structure (a = 8.069 Å, c = 4.967 Å, sp. gr. P321, Z = 1). The crystal studied is a polysynthetic twin with the twin index n = 2, whose monoclinic components are related by pseudomerohedry by a threefold rotation axis of the supergroup P321.     

Synthesis,Crystal Structure and Spectral Properties of [Fe<Subscript>3</Subscript>(2,2′-bipy)<Subscript>6</Subscript>(ox)<Subscript>3</Subscript>]·12.25H<Subscript>2</Subscript>O Complex

A novel iron (II) complex of formula [Fe₃(2,2′-bipy)₆(ox)₃]·12.25H₂O (2,2′-bipy = 2,2′-bipyridine, ox = oxalate) has been prepared and structurally characterized by X-ray crystallography. In the complex, the metal atoms are six-coordinated in distorted octahedral environment. In the complex [Fe(ox)₃]^4? anions and water molecules are linked together into 1D chain structure by hydrogen interaction. The red crystal of the complex is monoclinic, space group P2₁/c, with a = 22.932(6) Å, b = 13.715(4) Å, c = 22.493(6) Å, β = 93.177(5)°, and V = 7063(3) Å³ with Z = 4.     

Synthesis and Crystal Structure of Di-μ-chlorido-bis{chlorido[4-ethyl-<Emphasis Type="Italic">N</Emphasis>-(pyridin-2-ylmethylidene-κ<Emphasis Type="Italic">N</Emphasis>)aniline-κ<Emphasis Type="Italic">N</Emphasis>]mercury(II)}

The centrosymmetric dinuclear title complex [Hg₂Cl₄(dip)₂] was synthesized using the Schiff base bidentate ligand (E)-4-ethyl-N-(pyridine-2-ylmethylene)benzeneamine (dip) and mercury(II) chloride salts. It has been characterized by elemental analysis, X-ray diffraction, and UV-Visible and infrared spectroscopic techniques. The X-ray analysis shows that the title compound crystallizes in the monoclinic sp. gr. P2₁/n, Z = 2 with a = 7.8233(17) Å, b = 15.178(3) Å, c = 12.559(3) Å, β = 97.021(3)°. The Hg(II) ion has a distorted trigonal–bipyramidal coordination environment formed by the bischelating N-heterocyclic ligands, two bridging Cl atoms and one terminal Cl atom.     

Crystal structure of golyshevite

The crystal structure of golyshevite, a new calcium-and carbon-rich representative of the eudialyte group, was established by single-crystal X-ray diffraction analysis (sp. gr. R3m, a = 14.231(3) Å, c = 29.984(8) Å, R = 0.062, 1643 reflections with F > 3σ(F)). The idealized formula of golyshevite is (Na₁₀Ca₃)Ca₆Zr₃Fe₂SiNb[Si₃O₉]₂[Si₉O₂₇]₂(OH)₃(CO₃) · H₂O. This mineral is characterized by the presence of calcium atoms both in the octahedral positions of six-membered rings and in extraframework positions, where calcium prevails. CO₃ groups are present as the major additional anions. Carbon atoms randomly occupy two positions on the threefold z axis at a distance of 0.75 Å from each other and are coordinated by oxygen atoms arranged around the z axis.     

Crystal structure of low-symmetry rondorfite

The crystal structure of an aluminum-rich variety of the mineral rondorfite with the composition Ca₁₆[Mg₂(Si₇Al)(O₃₁OH)]Cl₄ from the skarns of the Verkhne-Chegemskoe plateau (the Kabardino-Balkarian Republic, the Northern Caucasus Region, Russia) was solved in the triclinic space group with the unit-cell parameters a = 15.100(2) Å, b = 15.110(2) Å, c = 15.092(2) Å, α = 90.06(1)°, β = 90.01(1)°, γ = 89.93(1)°, Z = 4, sp. gr. P1. The structural model consisting of 248 independent atoms was determined by the phase-correction method and refined to R = 3.8% with anisotropic displacement parameters based on all 7156 independent reflections with 7156 F > 3σ(F). The crystal structure is based on pentamers consisting of four Si tetrahedra linked by the central Mg tetrahedron. The structure can formally be refined in the cubic space group (a = 15.105 Å, sp. gr. Fd \(\overline 3 \), seven independent positions) with anisotropic displacement parameters to R = 2.74% based on 579 reflections with F > 3σ(F) without accounting for more than 1000 observed reflections, which are inconsistent with the cubic symmetry of the crystal structure.     

Crystal structure of complex natural aluminum magnesium calcium iron oxide

The structure of a new natural oxide found near the Tashelga River (Eastern Siberia) was studied by X-ray diffraction. The pseudo-orthorhombic unit cell parameters are a = 5.6973(1) Å, b = 17.1823(4) Å, c = 23.5718(5) Å, β = 90°, sp. gr. Pc. The structure was refined to R = 0.0516 based on 4773 reflections with |F| > 7σ(F) taking into account the twin plane perpendicular to the z axis (the twin components are 0.47 and 0.53). The crystal-chemical formula (Z = 4) is Ca₂Mg ₂ ^IV Fe ₂ ^(2+)IV [Al ₁₄ ^VI O₃₁(OH)][Al ₂ ^IV O][Al^IV]AL^IV(OH)], where the Roman numerals designate the coordination of the atoms. The structure of the mineral is based on wide ribbons of edge-sharing Al octahedra (an integral part of the spinel layer). The ribbons run along the shortest x axis and are inclined to the y and z axes. The adjacent ribbons are shifted with respect to each other along the y axis, resulting in the formation of step-like layers in which the two-ribbon thickness alternates with the three-ribbon thickness. Additional Al octahedra and Mg and Fe²⁺ tetrahedra are located between the ribbons. The layers are linked together to form a three-dimensional framework by Al tetrahedra, Ca polyhedra, and hydrogen bonds with the participation of OH groups.     

Refinement of the crystal structure of rhombohedral KU<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> as a representative of orthophosphates with the NaZr<Subscript>2</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> structure

The crystal structure of the high-temperature β modification of synthetic orthophosphate KU₂(PO₄)₃ was refined from powder X-ray diffraction data by the Rietveld method: sp. gr. \(R\bar 3c\), the unit-cell parameters a= 9.113(1) Å and c= 24.997(1) Å. The isotropic refinement converged to R _wp = 6.15, R _B = 2.14, R _F = 3.52, and S = 0.42. It was confirmed that β-KU₂(PO₄)₃ belongs to the structure type of sodium zirconium phosphate containing an actinide atom in a sixfold (octahedral) coordination formed by oxygen atoms, which is unusual for orthophosphates. The principal interatomic distances and bond angles in the structure are reported.     

Synthesis and Crystal Structure of a Four-coordinated Cobalt Complex with 1-Methylbenzimidazole

A four-coordinated complex, L₂Co(NCO)₂, (L = 1-methylbenzimidazole) has been synthesized and characterized by IR spectroscopy, elemental analyses, and single crystal X-ray diffraction. The crystal is monoclinic, a = 14.522(2) Å, b = 14.610(2) Å, c = 8.6850(13) Å, β = 92.037(3)°, Z = 4, sp. gr. P2₁/c. Bond lengths Co–N(L) are equal to 2.0165(16) and 2.0174(15) Å, Co–O(NCO) are 1.944(2) and 1.945(2) Å. Intermolecular C–H···O, C–H···N, and C–H···π interactions link the molecules into three-dimensional networks in the crystal.     

Crystal structure of the Na-, Ca-, Be-cordierite and crystallochemical regularities in the cordierite—sekaninaite series

The crystal structure of the beryllium-rich cordierite [(Na_0.28Ca_0.19)(H₂O)_0.92](Mg_1.86Fe _0.14 ^22? ) · { Al_3.39Be_0.61Si₅O₁₈} was established by X-ray diffraction analysis (IPDS Stoe diffractometer, λMoKα radiation, graphite monochromator, 2θ_max = 65°, R = 0.0186 for 1378 reflections): a = 16.850(3), b = 9.729(2), and c = 9.298(2) Å; V = 1524.3(4) ų, sp. gr. Cccm, Z = 4, and ρ_calcd = 2.655 g/cm³. The numbers of Mg and Fe atoms isomorphously occupying the octahedral positions, Al and Be atoms in tetrahedra, and Na and Ca atoms and H₂O molecules in the framework cavities are refined. The hydrogen atom is localized and its coordinates and thermal displacement parameters are refined. Based on the comparative crystallochemical analysis of cordierites from different locations and origins, the regularities relating the unit-cell parameters b and c and the distortion index to the features of the chemical composition of the minerals under study are shown.     

Molecular structures of chalcone podands: A prognosis of photoinduced transformations in the crystals

A series of chalcone podands with the propenone group in the ortho position of the bridging aryl substituent with respect to the oxyethylene fragment is synthesized. The influence of the preorganization of the chalcone podand molecules in crystals on their ability to participate in topochemical reactions is investigated. From analyzing the X-ray structural data, the highest probability of the solid-state photochemical [2 + 2]cycloaddition is predicted for podands with phenyl substituents and the oxyethylene fragment containing two or three oxygen atoms. The X-ray structural data for the chalcone podand C₃₂H₂₆O₄ (3a) are as follows: a = 7.904(9) Å, b = 14.92(2) Å, c = 21.30(3) Å, β = 91.7(1)°, monoclinic system, space group P2₁/c, Z = 4, V = 2510(5) ų, ρ = 1.26 g/cm³, and R = 0.046; C₃₄H₃₀O₅ (3b): a = 15.738(9) Å, b = 11.889(2) Å, c = 15.0830(15) Å, β = 105.47(14)°, monoclinic system, space group C2/c, Z = 4, V = 2720.0(9) ų, ρ = 1.266 g/cm³, and R = 0.0418; C₃₂H₂₄N₂O₈ (4a): a = 17.9416(18) Å, b = 10.9703(8) Å, c = 41.699(2) Å, β = 105.970(11)°, monoclinic system, space group P2₁/c, Z = 4, V = 2781.4(5) ų, ρ = 1.348 g/cm³, and R = 0.0426; C₃₆H₃₂N₂O₁₀ (4c): a = 7.6286(5)Å, b = 17.9398(10) Å, c = 11.5890(3)Å, β = 95.287(4)°, monoclinic system, space group P2₁/n, Z = 2, V = 1579.27(14) ų, ρ = 1.372 g/cm³, and R = 0.0377; and C₂₈H₂₂O₆ (5a): a = 15.6032(10) Å, b = 8.1131(5) Å, c = 17.7334(11) Å, β = 91.381(5)°, monoclinic system, space group C2/c, Z = 4, V = 2244.2(2) ų, ρ = 1.345 g/cm³, and R = 0.0309.     

Synthesis,Crystal Structure,and Free Radical Scavenging Activity of 4-Aminopyridinium 3,5-Dinitrobenzoate

The crystal structure of 4-aminopyridinium 3,5-dinitrobenzoate, C₁₂H₁₀O₆N₄, has been determined by single-crystal X-ray diffraction technique. The title compound crystallizes in the monoclinic sp. gr. P21/n with the unit cell parameters: a = 7.4726(3) Å, b = 23.0898(9) Å, c = 8.0744(4) Å, V = 1338.64(10) ų, Z = 4. The asymmetric unit of the compound consists of one 3,5-dinitrobenzoate anion and 4-aminopyridine cation. The adjacent anions and cations are linked through two N?H···O hydrogen bonds, N2?H2A···O5 and N₂?H2B···O6, to form an infinite chain of anions and cations, extended along the [010] direction.     

X-ray diffraction study of Rb<Subscript>2</Subscript>[(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>(CrO<Subscript>4</Subscript>)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>] · 4H<Subscript>2</Subscript>O

The compound Rb₂[(UO₂)₂(CrO₄)₃(H₂O)₂] · 4H₂O was studied by X-ray diffraction. The crystals are monoclinic, a = 10.695(2) Å, b = 14.684(3) Å, c = 14.125(3) Å, β = 108.396(4)°, sp. gr. P2₁/c, Z = 4, V = 2104.9(7) ų, and R = 0.0491. The main structural units are layers consisting of [(UO₂)₂(CrO₄)₃(H₂O)₂]^2? anions belonging to the crystal-chemical group A ₂ T ₂ ³ B ²M ₂ ¹ (A = UL ₂ ²⁺ , T ³ and B ² are CrO ₄ ^2? , and M ¹ is H₂O) of uranyl complexes. The uranium-containing layered groups are held together by electrostatic interactions with rubidium cations, as well as by hydrogen bonds with the participation of inner- and outer-sphere water molecules.     

Synthesis,Crystal Structure,and Topology–Symmetry Analysis of a New Modification of NaIn[IO<Subscript>3</Subscript>]<Subscript>4</Subscript>

Crystals of new iodate NaIn[IO₃]₄ were prepared by the hydrothermal synthesis. The unit cell parameters are a = 7.2672(2) Å, b = 15.2572(6) Å, c = 15.0208(6) Å, β = 101.517(3)°, sp. gr. P2₁/c. The formula was determined during the structure determination and refinement of a twinned crystal based on a set of reflections from the atomic planes of the major individual. The refinement with anisotropic displacement parameters was performed for both twin components to the final R factor of 0.050. The In and Na atoms are in octahedral coordination formed by oxygen atoms. The oxygen octahedra are arranged into columns by sharing edges, and the columns are connected by isolated umbrella-like [IO₃]^– groups to form layers. The new structure is most similar to the isoformular iodate NaIn[IO₃]₄, which crystallizes in the same sp. gr. P2₁/c and is structurally similar, but has a twice smaller unit cell and is characterized by another direction of the monoclinic axis. The structural similarity and difference between the two phases were studied by topologysymmetry analysis. The formation of these phases is related to different combinations of identical one-dimensional infinite chains of octahedra.     

Polymorphism of the borophosphate anion in K(Fe,Al)[BP<Subscript>2</Subscript>O<Subscript>8</Subscript>(OH)] and Rb(Al,Fe)[BP<Subscript>2</Subscript>O<Subscript>8</Subscript>(OH)] crystal structures

The crystal structure of two borophosphates, Rb(Al,Fe)[BP₂O₈(OH)] (a = 9.381(6), b = 8.398(5), c = 9.579(6) Å, β = 102.605(10)°, sp. gr. P2₁/c) and K(Fe,Al)[BP₂O₈(OH)] (a = 5.139(2), b = 8.065(4), c = 8.290(4)Å, α = 86.841(8)°, β = 80.346(8)°, γ = 86.622(8)°, sp. gr. P \(\bar 1\)), obtained by hydrothermal synthesis in the AlCl₃: FeCl₃: K₃PO₄(Rb₃PO₄): B₂O₃: H₂O system has been established using X-ray diffraction (Bruker Smart diffractometer, T = 100 K). Hydrogen atoms are located and their coordinates and thermal parameters are refined. It is shown that the polymorphism of the [BP₂O₈(OH)]^4? borophosphate anion has a morphotropic nature and is related to the substitutions both in the cationic part of the structure and in the octahedral position of the anionic mixed framework. The synthesis of new isotypic triclinic compounds under hydrothermal conditions is predicted.     

Synthesis and structure of Cs[UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(OH)] · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (<Emphasis Type="Italic">n</Emphasis> = 1.5 or 1)

The synthesis and single-crystal X-ray diffraction study of Cs[UO₂(SeO₄)(OH)] · 1.5H₂O (I) and Cs[UO₂(SeO₄)(OH)] · H₂O (II) are performed. Compound I crystallizes in the monoclinic crystal system, a = 7.2142(2) Å, b = 14.4942(4) Å, c = 8.9270(3) Å, β = 112.706(1)°, space group P2₁/m, Z = 4, and R = 0.0222. Compound II is monoclinic, a = 8.4549(2) Å, b = 11.5358(3) Å, c = 9.5565(2) Å, β = 113.273(1)°, space group P2₁/c, Z = 4, and R = 0.0219. The main structural units of crystals I and II are [UO₂(SeO₄)(OH)]^? layers which belong to the AT ³ M ² crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ , T ³ = SeO₄ ^2?, and M ² = OH^?). In structure I, johannite-like layers are found. Structure II is a topological isomer of I. The two structures differ in the number of U(VI) atoms bound to the central atom by all bridging ligands.