Crystal structure of a calcium sulfate-urea complex

The crystal structure of CaSO₄ · 4(CH₄N₂) has been determined from 2695 x-ray intensities measured on a diffractometer, and refined anisotropically to anR-factor of 0.059. The pseudotetragonal crystals contain linear chains of CaSO₄ which strongly resemble those in other CaSO₄ phases. A common dodecahedral coordination of calcium ions in all these phases is demonstrated, and its implications in the conversion from one phase to another is discussed.     

Crystal structure of triphenylphosphine oxide

The crystal structure of Triphenylphosphine Oxide, C₁₈H₁₅PO, was reinvestigated using Mo-K radiation =0.71069 Å,(Mo-K)=1.36 cm^–1.M _r=278.1, orthohombic,Pbca,a=29.089(3),b=9.1347(9),c=11.261(1) Å,V=2992.2 ų,Z=4,D _x=1.235 Mg m^–3. The structure was refined by full-matrix least-squares toR=0.040 andR _w=0.036 for 1848 unique reflections and 182 variables. Improved bond lengths and angles were obtained; O-P is 1.479(2) Å, weighted means of P-C is 1.803(1) Å, O-P-C is 112.6(1)° and C-P-C is 106.2(1)°.     

Crystal structure of calcium adipate monohydrate

The crystal structure of calcium adipate monohydrate, Ca(C₆H₈O₄)·H₂O, has been determined by single crystal X-ray diffraction study. The crystals are triclinic witha=5.8990(3),b=6.7985(5),c=10.8212(6)Å,=78.999(5),=81.831(5), and =82.971(5)°, space group P¯1,Z=2,V=419.65(8)ų,d _m=1.59,d _c=1.600 Mg m^–3. The structure was refined by full-matrix least-squares techniques toR=0.040,R _w=0.058 for 1283 reflections withI3(I). Ca is coordinated to seven oxygen atoms and the coordination polyhedron is best described as pentagonal bipyramid. The coordinations of the two carboxylate groups in adipate ion are quite different. One carboxylate group binds three different Ca ions forming a four-membered chelate ring with one Ca ion and unidentate bridge bonds to two other Ca ions. The other carboxylate group links to two Ca ions through unidentate bonds. The structure is highly polymeric, but with a layertype structure parallel to (001) with the hydrocarbon chains sandwiched between the polar regions consisting of Ca, carboxylate and water molecules.Certain commercial materials and equipment are identified in this paper to specify the experimental procedure. In no instance does such identification imply recommendation or endorsement by the National Institute of Standards and Technology or the ADA Health Foundation or that the material or equipment identified is necessarily the best available for the purpose.     

Crystal structure of aluminum sulfate hexadecahydrate and its morphology

A single‐crystal structure of aluminum sulfate hexadecahydrate (Al₂(SO₄)₃·16H₂O) was captured with a polarizing microscope. The structure was similar to a hexagonal plate and consistent with the predicted morphology derived from the modified AE model. An octagonal plate morphology was first obtained in a vacuum but was transformed into hexagonal plate‐like when the effect of the solvent with two disappearing {1 1 0} and {1 0 −1} faces was considered.     

Crystal structure of a pentanuclear gold-silver cluster complex

The title compound, [C₁₆H₃₆N]⁺[C₄₈H₃₀Au₃Ag₂]^–, crystallizes in the triclinic space groupP1^–1, witha=18.199(12),b=19.210(8),c=19.270(9)Å,=71.34(3)°=76.43(4)° =72.95(5)° andZ=4, with two independent molecules in the asymmetric unit. The structure was solved by direct methods and refined by full-matrix least squares methods toR=0.072 for 3739 observed reflections. The metal atoms have a trigonal-bipyramidal arrangement with the three Au atoms forming an equilateral triangle and two Ag atoms occupying apical positions. Each Au atom is -bonded to phenylethynyl ligands in a linear coordination. Each Ag atom is asymmetrically pi-bonded to three alkyne groups. The Au-Au distances lie in the range of 3.934–4.010 A, indicating the lack of Au-Au bond.     

Crystal structure of the tetranickel complex with Ipropanethiolate

The title complex [Ni₄(SPrⁱ)₈] was confirmed by single crystal X-ray crystal diffraction analysis. The crystals are monoclinic, space group P2/n with a = 12.760(3), b = 10.059(2), c = 14.484(3) Å, α = 90, β = 93.70(3), γ = 90°, V = 1855.3(6) ų, Z = 4, F(000) = 880, D_c = 1.496 g/cm³, μ = 2.463 mm^?1, the final R = 0.0352 and wR = 0.0580. A total of 18,588 reflections were collected, of which 4404 were independent (R_int = 0.0631). In the crystal packing diagram, intermolecular C—H···Ni hydrogen bonds stabilize the solid state of the title complex.     

Crystal destruction of zeolite NaA during ion exchange with magnesium and calcium ions

Extreme conditions of ion exchange like, for instance, highly concentrated solution, high temperature and a long time of exchange can cause destructions of crystals. Zeolites NaMgA are structurally degraded much more than zeolites NaCaA. Reason for the reduced stability of crystals in presence of alkaline earth ions is the proton concentration increased beyond the dissociation equilibrium of water owing to the formation of weakly dissociated alkaline earth ion hydroxides. The zeolite lattice is destroyed hydrolytically by the influence of protons.     

Crystal structure of lithium magnesium phosphate,LiMgPO4: Crystal chemistry of the olivine-type compounds

LiM_gPO₄ is orthorhombic, space groupPnma,a=10.147(2),b=5.909(2),c=4.692(2)×10^–10 m,D _m =3000(8),D _x =2980 kg m^–3,Z=4,R=4.8% for 1262 observed reflections. The structure contains tetrahedral PO₄ and octahedral LiO₆ and MgO₆ groups. It belongs to the ordered olivine-type structures, since the inversion site is occupied by Li⁺ ions and the mirror site is taken by Mg²⁺ ions. The distortion of polyhedra is caused mainly by the adjustment stresses between the different polyhedral dimensions and by the sharing of edges. Octahedral LiO₆ share six and MgO₆ share three common edges. The sharing of the O-O edges contributes to the stability of the bridging arrangements. The corresponding average distances of the O-O bridges are 2.432, 2.479, 2.883, and 3.028×10^–10 m, while the average O-O distances in the PO₄, MgO₆, and LiO₄ polyhedra are 2.512,2.921, and 3.015 × 10^–10 m, close to the ideal values 2.531, 2.970, and 3.026×10^–10 m respectively. The structure field of the olivine-type compounds plotted as a function of ionic radii in radius space is specified in relation to the-K₂SO₄, spinel, and K₄NiF₄ type structures. From the overlap of the structure fields, the high-pressure transformations of the olivine compounds are considered.     

Crystal structure of the charge transfer complex 9-cyclohexyladenine-iodine

The crystal structure of the charge-transfer complex of iodine with 9-cyclohexyladenine, C₁₁H₁₅I₂N₅, has been determined, and refined by three-dimensional least-squares techniques. The crystals are monoclinic:P2₁/c,Z = 4,a = 9·1728(7),b = 12·289(1),c = 13·596(1) Å, = 99·564 °(6). The finalR value for 3629 reflexions is 0·039. The iodine forms a charge-transfer bond with N(1) of the adeninering, with an N—I bond length of 2·520(3) Å. The I—I—N(1) arrangement is approximately linear (bond angle, 177·1 °). The I—I molecule makes an angle of 21·5 ° with the plane of the adenine ring.Supported by N. I. H. Development Award 5-K4-GM-42572.     

Crystal structure of an yttrium nitrate complex with tetramethylurea

An X-ray diffraction study of Y(NO₃)₃ · 3TMU crystals is performed (heavy-atom method, difference electron-density maps, H atoms in calculated positions, full-matrix anisotropic-isotropic (H) least-squares refinement). The crystals are monoclinic, a = 9.353(1) Å, b = 15.966(3) Å, c = 18.805(8) Å, β = 95.41(2)°, Z = 4, and space group P2₁/c. The structural units of the crystals are molecular complexes. The coordination number of the Y atom is nine due to three bidentate NO₃ groups and three monodentate tetramethylurea molecules. The mean Y-O bond lengths are 2.464 and 2.274 Å for NO₃ and tetramethylurea, respectively.     

Crystal structure of a butyllithium 1,2-dipiperidinoethane dimer complex

The crystal structure of butyllithium solvated by 1,2-dipiperidinoethane, BuLi·DPE-6, which has been used as an initiator for a number of important commercial anionic polymerization reactions, is reported. The complex crystallizes from pentane as a centrosymmetric dimer in the monoclinic space group P2₁/n with a = 9.8619(12), b = 17.963(2), c = 10.3655(12) ?, β = 114.090(2)° and Z = 2. The dimer is located on a crystallographic inversion center. The crystal under investigation was found to be non-merohedrally twinned. In contrast to the two other dimeric BuLi complexes previously structurally characterized in the solid state, BuLi·DPE-6 has a planar central Li₂C₂ core. Semi-empirical (PM3) calculations were used to determine the lowest energy conformations of the dimer and also identified three structural motifs that affect Li₂C₂ dimer ring planarity.     

Crystal and molecular structure of the complex boron triferrocenyl-pyridine

The title compound is C₃₅H₃₂NBFe₃, monoclinic,P2₁/n,a=14.204 (4),b=11.582 (4),c=17.547 (6) Å,=101.46 (2)°. The structure was solved by the heavy-atom method and refined by least-squares techniques to anR factor of 0.037 for 3148 observed reflections. The X-ray study confirms that in the solid state the structure of the title compound is similar to that inferred from chemical and spectroscopic evidence. The B atom is coordinated by three ferrocenyl groups and a pyridine ring in a distorted tetrahedral array. The molecule has a nearly three-fold axis normal to the plane defined by the ferrocenyl groups. The B-N distance of 1.656 (5) Å is larger than that obtained for other compounds studied. Bond lengths and angles for the whole structure are all in accord with similar compounds. The pyridine and cyclopentadienyl rings are planar. The H atoms of the cyclopentadienyl rings are displaced significantly toward their corresponding Fe atom. The molecules in the crystal are packed at normal van der Waals distances. No unusually short intermolecular contacts are noted.     

Growth of aragonite calcium carbonate nanorods in the biomimetic anodic aluminum oxide template

In this study, a biomimetic template was prepared and applied for growing calcium carbonate (CaCO₃) nanorods whose shape and polymorphism were controlled. A biomimetic template was prepared by adsorbing catalytic dipeptides into the pores of an anodic aluminum oxide (AAO) membrane. Using this peptide-adsorbed template, mineralization and aggregation of CaCO₃ was carried out to form large nanorods in the pores. The nanorods were aragonite and had a structure similar to nanoneedle assembly. This aragonite nanorod formation was driven by both the AAO template and catalytic function of dipeptides. The AAO membrane pores promoted generation of aragonite polymorph and guided nanorod formation by guiding the nanorod growth. The catalytic dipeptides promoted the aggregation and further dehydration of calcium species to form large nanorods. Functions of the AAO template and catalytic dipeptides were verified through several control experiments. This biomimetic approach makes possible the production of functional inorganic materials with controlled shapes and crystalline structures.     

Optical properties of nanocomposites with iron core-iron oxide shell structure

Iron nanoparticles of diameter ∼5 nm were produced within a gel-derived silica glass by reducing a suitable gel composition. By heating these composites in the temperature range 573-973 K, Fe₃O₄ shells of a few nanometer thickness were grown around the iron nanoparticles. Three peaks were observed in the optical absorption spectra of the nanocomposites when they were dispersed in ethyl alcohol. The first one around 300 nm was caused by plasma resonance absorption of unoxidized iron particles; the second was shown to be due to the core-shell structure with different permittivities of the two regions and the third one was ascribed to a d-d transition. Detailed analyses of the second peak showed that the extracted values of electrical conductivity were below Mott’s minimum metallic conductivity for iron in the case of particles with diameters below ∼2.5 nm.     

Crystal and molecular structure of the 2,4,7-trinitrofluorenone-hexamethylbenzene charge-transfer complex

The crystal and molecular structure of the charge-transfer complex formed between 2,4,7-trinitrofluorenone and hexamethylbenzene has been determined by single-crystal X-ray diffraction techniques. The complex crystallizes with four charge-transfer pairs in a monoclinic cell (P2₁/c) of dimensionsa = 9.533(1),b = 14.944(2),c= 17.470(2) Å and = 113.18(1) °. The structure was solved by direct methods. The orderly packing of donor and acceptor molecules in parallel crystalline planes made the determination a severe test of direct methods techniques. The 2294 statistically significant reflections were refined to a final value ofR = 0.063. Estimated standard deviations were 0.004 Å in bond distances and 0.5 ° in bond angles among the non-hydrogen atoms. The acceptor and donor molecules lie in alternate (212) planes with a separation of 3.25 Å between the planes.     

Crystal structure and vibrational spectra of the methylmercury complex withl-alanine

The 11 methylmercury complex withl-alanine belongs to the orthorhombic space groupP2₁2₁2₁. The unit cell of dimensionsa=5.763(3),b=6.851(6),c=18.75(2) Å contains four molecules. The structure was refined on 584 nonzero reflections toR=0.050. The methylmercury ion has replaced an ammonium proton and is linearly bonded to the nitrogen atom. Mercury is also involved in secondary inter- and intramolecular contacts with carboxylate oxygen atoms. Infrared and Raman spectra of the amino-deuterated complex are discussed and compared with those of the undeuterated compound. A correlation is found between backbone conformation and the pattern of Hg-N and Hg-C bands in the Raman spectra.     

Crystal and molecular structure of a silver complex ofo-aminobenzenesulfonyl glycine

The silver complex ofo-aminobenzenesulfonyl glycine crystallizes in the monoclinic space groupP2₁/n with two molecules of HAg[C₆H₄(NH₂)SO₂-NHCH₂COO]₂ per unit cell of dimensionsa=5.73(2),b=12.16(1),c=13.94(3) Å, and =94.9(1) °. The structure has been solved by the heavy-atom technique using three-dimensional photographic data, and refined by full-matrix least-squares methods, leading to a finalR value of 0.102. The two aminobenzenesulfonyl glycine ligands in the complex are centrosym-metrically arranged with the silver atom at the center of symmetry. The silver atom is surrounded in an approximately square-planar arrangement by two nitrogens (one each from the amino groups attached to benzene rings) and two oxygens (one each from the carboxyl groups) at distances of 2.280 and 2.599 Å, respectively. The glycine in this complex is not a zwitterion. The molecules are held together by a three-dimensional network of hydrogen bonds of the type N-H O. Both the -amino nitrogen and that attached to the benzene ring take part in the formation of hydrogen bonds.     

The crystal structure of a magnesium(II) ethyl diglyme complex

Dibromo[1,1-oxybix[2-ethoxyethane]-O,O,O]-(tetrahydrofuran-O) magnesium, C₁₂H₂₆O₄MgBr₂, crystallizes in space group Pbca witha=7.402(1),b=16.726(2),c=29.248(3) Å,V=3620.9(12) ų,Z=8. The structure was refined toR=0.083 andR _w =0.055 for 1880 observed reflections. Magnesium is octahedrally coordinated by twocis bromine atoms and four oxygen atoms, three from the meridional ethyl diglyme and one from tetrahydrofuran. The Mg–Br distances are 2.614(3)trans to thf and 2.529(3) Åtrans to the central O of the diglyme. The Br–Mg–Br angle is 97.9(1)° and the Mg–O(thf) distance is 2.196(6) Å. The O–Mg–O bite angles subtended by the diglyme are 75.3(2) and 75.7(2)°. The Mg–O(ethyl diglyme) distances are 2.127(6), 2.136(6), and 2.090(6) Å.     

Crystal structure of the double magnesium zirconium orthophosphate at temperatures of 298 and 1023 K

Double magnesium zirconium orthophosphate Mg_0.5Zr₂(PO₄)₃ is synthesized by the sol-gel method. The compound prepared is characterized using electron probe microanalysis and X-ray diffraction. The crystal structure of the orthophosphate is refined by the Rietveld method in space group P2₁/n (Z = 4) at temperatures of 298 K [a = 12.4218(2) Å, b = 8.9025(2) Å, c = 8.8218(2) Å, β = 90.466(1)°] and 1023 K [a = 12.4273(5) Å, b = 8.9453(4) Å, c = 8.8405(4) Å, β = 90.320(3)°]. It is demonstrated that an increase in the temperature leads to an anisotropic expansion of the unit cell of the phosphate structure, but the structural type remains unchanged.