Crystal structures of double vanadates, Ca9 R(VO4)7 ⋅ III. R = Nd, Sm, Gd, or Ce

The crystal structures of Ca₉ R(VO₄)₇ (R = Nd (I), Sm (II), or Gd (III)) were studied by the Rietveld method. The compounds are isostructural to Ca₃(VO₄)₂ and are crystallized in the trigonal system (sp. gr. R3c, Z = 6). The unit-cell parameters are as follows: for I, a = 10.8720(5) Å, c = 38.121(1) Å; for II, a = 10.8652(5) Å, c = 38.098(1) Å; and for III, a = 10.8631(5) Å, c = 38.072(1) Å. In the structures of I and II, the M(1), M(2), and M(3) positions are statistically occupied by the rare-earth cations and calcium anions. In the structure of III, the Gd³⁺ cations occupy the _M(1) and _M(2) positions. The distributions of the R ³⁺ cations over the positions are characteristic of each structure. The composition of the cerium-ontaining compound Ca_9.81Ce_0.42(VO₄)₇ (a = 10.8552(5) Å, c = 38.037(1) Å) was refined and its crystal structure was solved from the X-ray powder data. In this compound, cerium atoms are in the oxidation states +3 and +4.     

Molecular structure and absolute configuration of (+)-(1R, 2S, 6R, 7S, 1′R)-5-(1′-phenylethylamino)-endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-one

The crystal and molecular structure of (+)-(1R, 2S, 6R, 7S, 1R)-5-(1-phenylethylamino)-endo-tricyclo[5.2.1.0^2,6]deca-4,8-dien-3-one is described. Based on the known absolute configuration (R) of the -phenylethylamine moiety the X-ray analysis revealed the absolute configuration of the title compound. The structure was refined to R ₁ = 0.0298 for 1950 reflections (with I > 2(I)). Crystal data: C₁₈H₁₉NO, monoclinic, space group P2₁, a = 6.7406(4), b = 9.959(2), c = 11.3123(8)Å, = 102.969(5), V = 740.0(2)ų, and Z = 2.     

Thermal conductivity of single crystals of Ba1–x R x F2 + x (R = La,Ce, Nd,or Gd) solid solutions

The thermal conductivity of single crystals of Ba_1–х R _х F_{2 + х} (R = La, Ce, Nd, or Gd) solid solutions has been experimentally investigated in the temperature range of 50–300 K. With an increase in the content of rare-earth elements, the thermal-conductivity behavior in these series changes from that characteristic of defect single crystals to the behavior typical of glasslike materials. The thermal-conductivity concentration dependences are almost identical, which can be explained by the same type of defect clusters arising upon heterovalent ion substitution.

     

The crystal and molecular structure of spiro[1-(S)-Br-3-(S)-H-4-(R)-l-(1′ R,2′ S,5′R)-menthyloxy-5-oxo-6-oxa-bicyclo[3.1.0]hexane-2,3′-(R)-(4′-(R)-diphenylmethoxy-5′-l-(1′ R,2′ S,5′ R)-menthyloxy-butyrolactone)]

Crystal structure of C₄₁H₅₃O₇Br has been determined by single-crystal X-ray diffraction. The compound crystalline in the orthorhombic space group P2₁2₁2₁, with a = 11.264(2), b = 12.058(2), c = 29.337(6) Å, Z = 4. The bond angles of cyclopropane moiety in the molecule are approximate to 60° and agree with theoretic values of the internal angles in a cyclopropane, and two chiral menthyloxy groups are located above and under the whole chiral molecule, respectively. The configuration of the pentacyclic lactone is shown as envelope form.     

Magnetic susceptibility of sodium rare-earth fluorites Na0.5 − x R 0.5 + x F2 + 2x (R = Dy, Ho, Er, Tm, Yb) and some ordered phases

Magnetic properties of the nonstoichiometric phases with the fluorite-type “defect” structure Na_0.4 R _0.6F_2.2 (R = Ho, Er, Tm, Yb) and Na_0.35Dy_0.65F_2.3 have been studied as well as some ordered phases with different distortions of the initial fluorite lattice (NaHo₂F₇, Na₇Tm₁₃F₄₆, NaYb₂F₇, and Na₇Yb₁₃F₄₆) and Na_1.5Dy_1.5F₆ with the gagarinite-type structure (NaCaYF₆). Magnetic susceptibility χ was measured with the aid of the Faraday balance in the temperature range from 20 to 300 K. The crystals with R= Dy, Ho, Er, Tm are paramagnetic; their temperature dependence χ is described by the Curie-Weiss law. It is shown that in the temperature range studied, magnetic susceptibility does not depend on the degree of order of Dy, Ho, Er, and Tm ions in the structure. Below 80 K, the temperature dependence of magnetic susceptibility of the the Yb³⁺-containing phases differs from the analogous dependence χ of an ideal paramagnetic crystal, which is assumed to be caused by the interaction of the crystalline field with Yb³⁺ ions.     

(20R,22R)-6α,7α-Epoxy-5α,27-dihydroxy-1-oxowitha-2,24-dienolide in Leaves of Withania somnifera: Isolation and its Crystal Structure

Abstract  (20R,22R)-6α,7α-Epoxy-5α,27-dihydroxy-1-oxowitha-2,24-dienolide (27-hydroxy-withanolide B) was isolated from Withania somnifera. The structure of the withanolide was established by spectral analysis and X-ray diffraction studies. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters: a = 9.2163(3), b = 11.1828(4), c = 23.6146(9) ?, Z = 4. The crystal structure was refined to R = 0.0495 for 3,284 observed reflections. All the rings of the steroid skeleton are trans connected. Rings A and B exist in a half-chair conformation, ring C a chair, and five membered ring D is intermediate between a half-chair and an envelope. The δ-lactone ring E adopts a distorted sofa conformation. The twist along the length of the steroid nucleus is −6.5°. The characteristic pattern observed in the packing diagram is the appearance of twisted chains of molecules packed together to form layers. Index Abstract  Isolation and crystal structure analysis of (20R,22R)-6α,7α-epoxy-5α,27-dihydroxy-1-oxowitha-2,24-dienolide.      

Crystal Packing of Potentially Mesomorphic Azobenezene Derivatives R1–C6H4–N=N–C6H4–R2 (R1, R2 = CH3COO,C2H5O; CH2=C(CH3)COO,C2H5; C6H13COO,C2H5O)

Crystallography Reports - The structure and thermal properties of azobenzene derivatives R1–C6H4–N=N–C6H4–R2, where R1/R2 = CH3COO/C2H5O (I), CH2=C(CH3)COO/C2H5 (II), or...     

Molecular structure and absolute configuration of (−)-(1R, 2S, 6R, 7S, 2′S)-5-(2′-hydroxymethylpyrrolidin-1′-yl)-endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-one

The crystal and molecular structure of (–)-(1R, 2S, 6R, 7S, 2S)-5-(2-hydroxymethyl-pyrrolidin-1-yl)-endo-tricyclo[5.2.1.0^2,6]deca-4,8-dien-3-one is described. Knowing the absolute configuration of the prolinol moiety (S) the X-ray diffraction study established the absolute configuration of the title compound. The structure was refined to R ₁ = 0.0322 for 1237 reflections (with I > 2(I)). Crystal data: C₁₅H₁₉NO₂, monoclinic, space group P2₁, a = 6.0757(4), b = 11.3473(5), c = 9.5114(7)Å, = 104.686(6)°, V = 634.32(7)ų, and Z = 2.     

Crystal structures of [(η5-C5H4COOH)W(CO)3R] (R=Me,I)

The crystal structures of [(₅-C₅H₄COOH)W(CO)₃R] (R=Me, I) have been determined. They crystallize in two different monoclinic space groups. R=Me isP2₁/c,a=10.4833(6),b=8.0144(7),c=13.0731(6) , =93.147(4)°, andD(calc)=2.374 g-cm^–3 forZ=4. R=I isP2₁/n,a=7.814(2),b=13.075(4),c=11.097(4) , =91.75(2)°, andD(calc)=2.953 g-cm^–3 forZ=4. Both possess a four-legged piano stool geometry. The methyl ligand in the R=Me complex is disordered between two positions insyn oranti relative to the substituted carbon of the cyclopentadienyl ligand. The iodo ligand in the R=I complex is, however, exclusively insyn-position.     

Growth of R 2 Me(SO4)2 · 6H2O single crystals with due regard for solubility diagrams of the R 2SO4-MeSO4-H2O systems (R = K, NH4; Me = Ni, Co)

The optimum conditions for growing R ₂ Me(SO₄)₂ · 6H₂O crystals are found from the analysis of the _{R 2} ⁺ SO₄-Me ²⁺SO₄-H₂O systems (R = K, NH₄; Me = Ni, Co) in the temperature range from 55 to 25°C. A new economical technology for growth of single crystals of double sulfate hexahydrates is developed, which allows the use of starting presynthesized solutions of hydrated or anhydrous K, Ni, Co, and (NH₄) sulfates. Transparent K₂Ni(SO₄)₂ · 6H₂O, K₂Co(SO₄)₂ · 6H₂O, and (NH₄)₂Ni(SO₄)₂ · 6H₂O crystals (35–55) × (25–40) × 10 mm in size are grown on seeds by the method of slow cooling.     

Crystal structure of a (25R)-2α,3α-epoxy-5α-spirostan-6, 23-dione hemi-ethyl acetate solvate

The compound (25R)-2,3-epoxy-5-spirostan-6,23-dione, crystallizes as a hemi-ethyl acetate solvate, having two host molecules of similar conformation per molecule of ethyl acetate, in the asymmetric unit. The O atom of the epoxy group is -oriented. The presence of the epoxy group disturbs the chair conformation in the ring A of the steroidal nucleus. Ring A has a C5,C10 half-chair conformation. The six-membered rings B, C, and F have chair conformation as expected. The D ring adopts a C14-envelope conformation and the E ring is midway between a C22,O3 half-chair and a C22-envelope conformations. The A/B, B/C, and C/D ring junctions are trans. Crystal data: C₂₇H₃₈O₅·1/2C₄H₈O₂, Monoclinic, space group P2₁, a = 7.7363(18) b = 28.769(12) c = 12.038(6) Å, = 90.88(5), V = 2679.0(10) ų, Z = 4. The packing of the molecules is assumed to be dictated by van der Waals interactions and by intermolecular C—H ··· O hydrogen bonds.     

Comparison of the X-ray crystal structures of four closely related Mo(CO)5(R2PXR′) (R2 = OCH2CMe2CH2O, XR′ = S-2-Pr, NHC6H4-4-Me; R2 = Ph2, XR′ = NHC6H4-2-Me, OC6H4-4-SMe) complexes

The X-ray crystal structures of four closely related Mo(CO)₅(R₂PXR) (R₂ = OCH₂CMe₂CH₂O, XR = S-2-Pr, NHC₆H₄-4-Me; R₂ = Ph₂, XR = NHC₆H₄-2-Me, OC₆H₄-4-SMe) complexes have been determined. The R₂PXR ligands are oriented so that the P—X bond and one of the Mo—C bonds are nearly eclipsed. This results in the distortion of the octahedral coordination geometry via tilting of the Mo(CO)₅ group away from the XR group. As observed in related complexes, the Mo—C bond of the carbonyl trans to the phosphorus-donor group is shorter than are the Mo—C bonds of the carbonyls trans to carbonyls. In contrast, no significant differences were observed between the Mo—C bonds of carbonyls trans to phosphites and the Mo—C bonds of carbonyls trans to phosphinites. The conformations of the 1,3,2-dioxaphosphorinanes were distorted chairs with the P end of the chair significantly flattened relative to the seat of the chair. This conformation is similar to that which has been observed for 1,3,2-dioxaphosphorinanes in other transition metal complexes.     

293-K conductivity optimization for single crystals of solid electrolytes with tysonite structure (LaF3): I. Nonstoichiometric phases R 1−yCayF3−y (R = La-Lu,Y)

The systematic optimization of single-crystal fluoride-conducting solid electrolytes R _{1 ? y} Ca _y F_{3 ? y} with a tysonite type structure (LaF₃) with respect to the conductivity at room temperature, σ(293 K), is based on high-temperature measurements of σ(T) of stoichiometric fluorides of rare earth elements, RF₃ (R = La-Nd), in dependence of the radius \(R^{3 + } (r_{R^{3 + } } )\) ; two-component stoichiometric La_{1 ? y} R _y F₃ phases (R = Pr, Nd) in dependence on the average cation radius (r _cat ); and two-component nonstoichiometric phases R _{1 ? y} Ca _y F_{3 ? y} (R = La-Lu, Y) in dependence of the CaF₂ content. The optimization of the composition with respect to thermal stability is based on studying the phase diagrams of CaF₂-RF₃ systems and the behavior of R _{1 ? y} Ca _y F_{3 ? y} crystals upon heating when measuring temperature dependences σ(T). Singlecrystal samples of a number of investigated R _{1 ? y} Ca _y F_{3 ? y} compounds has σ(293 K) values high enough to be applied in solid-state electrochemical devices operating at room temperature (chemical sensors, fluorine-ion batteries, and accumulators) and in devices subjected to thermal cycling.     

Growth of Crystals of Solid Solutions with Tysonite Structure in the PbF2–RF3 Systems (R = Pr,Nd)

Crystallography Reports - Crystals of the R1 – yPbyF3 – y (R = Pr (0 ≤ y ≤ 0.09) or Nd (0 ≤ y ≤ 0.10)) solid solutions with a...     

Crystal and molecular structure of (3aR,8bS,5′R)3-[(2,5-dihydro-3-methyl-2-oxo-5-furanyl)oxymethylene]-3,3a,4,8b-tetrahydroindeno[1,2-b]furan-2-one

The stereogeometry and absolute configuration of the title compound has been proved by an X-ray diffraction analysis. Crystal data: monoclinic, C2,a=20.2528(4),b=6.7254(2),c=10.6748(2) Å, =94.699(3),Z=4. The crystal structure has been solved by vector search methods and refined toR ₁=0.053 for 2043 observed reflections.     

Formation and optical properties of (R2O or R′O)Nb2O5Ga2O3 glasses

Glass-forming tendencies of melts in the systems (alkali oxide or alkaline earth oxide)-Nb₂O₅Ga₂O₃ were examined by an ordinary crucible-melting technique. The glass-forming tendency increased with increasing radius of alkali or alkaline earth ion in the respective groups. Clear glasses were obtained on a practically useful scale in the systems (K₂O or Cs₂O)Nb₂O₅Ga₂O₃ and (SrO or BaO)Nb₂O₅Ga₂O₃. The infrared absorption spectra indicated that the Ga³⁺ ions in the glasses are tetrahedrally coordinated with oxygen ions. The glasses showed high optical transmissions from the ultraviolet region of 0.3 μm in wavelength to the infrared region of 7 μm, except for a region near 3 μm. The absorption near 3 μm, which is attributed to OH vibration, could be eliminated by replacing part of the carbonate in the raw materials with a fluoride and melting the mixture of raw materials in a dry N₂ gas atmosphere. The glass-forming tendencies of the melts and the optical transmissions of the glasses were discussed in terms of the glass structure.     

Intermetallic Compounds KnMm (М = Ag,Au, As,Sb, Bi,Ge, Sn,Pb): Geometrical and Topological Analysis,Cluster Precursors,and Self-Assembly of Crystal Structures

Crystallography Reports - A geometrical and topological analysis and simulation of the self-assembly of the crystal structures of intermetallic compounds formed in the K–M (M = Ag, Au, As,...     

Crystal growth and defect crystal structure of CdF2 and nonstoichiometric phases Cd1 − x R x F2 + x (R = rare earth element or in). 5. Crystal structure of as-grown Cd0.9R0.1F2.1 (R = La-Nd) single crystals: Nanoclusters of structural defects

As-grown Cd_0.9 R _0.1F_2.1 (R = La-Nd) crystals were assigned to the CaF₂ structure type and their structure was determined by X-ray diffraction. A new octacubic cluster of structural defects in Cd_0.9 R _0.1F_2.1 phases is proposed. The changes in the anionic motif of the Cd_0.9 R _0.1F_2.1 phase can be explained as a result of the formation of tetrahedral [Cd_{4 ? n} R _n F₂₆] and inverse octacubic [Cd_{14 ? n} R _n F₆₈] clusters with, respectively, tetrahedral and cuboctahedral anionic groups as cores. It is established that fluctuations of the La concentration in the cross section of a Cd_0.9La_0.1F_2.1 crystal boule do not exceed 2.7%.     

繁荣学术,服务产业,正五十,再出发

<正>疫情蔓延却挡不住时代悦动的脉搏,随着2022年新春钟声的敲响,《人工晶体学报》也迎来了创刊50周年。20世纪60年代后期,位于北京郊区的原国家建材局人工晶体研究所为了方便所内技术交流,创办了内部刊物《人工晶体译丛》,主要刊载所内技术人员翻译的国外相关领域最新进展。到1972年,期刊刊登范围逐步扩大,陆续刊出所内研究简报、研究论文等,同时也报道国内相关团队的研究近况,遂更名《人工晶体》。时值我国国防工业建设高潮,与国防工业关系密切的人工晶体材料正取得日新月异的发展,水晶、金刚石、云母三大合成晶体相继研发成功并走向市场,激光晶体、非线性光学晶体、闪烁晶体、压电晶体等一大批晶体合成成功,晶体界急需一本自己的专业期刊方便国内同行的交流。在老一辈晶体专家吴乾章等的共同倡议和努力下,《人工晶体》确定为中国硅酸盐学会晶体生长与材料专业委员会的代表会刊,从此走上时代舞台,肩负起传播中国晶体文化,引领中国晶体科技发展的历史使命。1989年,《人工晶体》更名《人工晶体学报》。