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  • Articles  (173)
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  • Springer  (173)
  • American Geophysical Union
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  • 1
    Electronic Resource
    Electronic Resource
    Effect of fillers on the steady state rheological behaviour of liquid crystalline polymers (1998)
    Springer
    Rheologica acta 37 (1998), S. 463-469 
    Details
    ISSN: 1435-1528
    Keywords: Key words Polymeric liquid crystals ; anisotropy ; fillers ; string phases ; negative normal stresses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The effect of fillers on the flow curves of polymeric liquid crystals is investigated. Suspensions of polystyrene particles in liquid crystalline solutions of hydroxypropylcellulose (HPC) in water are used. By reducing the HPC concentration an isotropic solution can be prepared. It serves as a reference to isolate the effect of the isotropic/anisotropic structure of the suspending medium on the rheological behaviour. Suspensions in the isotropic solution behave as expected for filled viscoelastic matrices in general. In the anisotropic medium the shear rate rather than the shear stress seems to govern the changes in the relative viscosity. This behaviour is clearly different from isotropic viscoelastic media. The most dramatic effect however is that even small amounts of particles eliminate or drastically shift the region of negative normal stress differences. As far as the structure is concerned, microscopic observations show that particles align in anisotropic as well as in isotropic media. At rest or at relatively low shear stresses the liquid crystalline structure is, in the present case, hardly affected by the presence of the particles. If anything, it becomes more homogeneous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003970050133
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  • 2
    Electronic Resource
    Electronic Resource
    Leaky modes of channel waveguides with uniaxial anisotropy (1999)
    Springer
    Optical and quantum electronics 31 (1999), S. 733-749 
    Details
    ISSN: 1572-817X
    Keywords: anisotropy ; Leaky modes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract An exact numerical method for analyzing the propagation properties of leaky modes of inhomogeneous channel optical waveguides with a complex uniaxial diagonal permittivity tensor is developed. The method is based on solving the system of integro-differential equations formulated with respect to transversal components of the magnetic field and the longitudinal component of the electric field. Some results of investigation of leaky modes of diffused channel waveguides in LiNbO3 and LiTaO3 crystals are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006978311814
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal structure of tetrakisdiphenylammonium hexadecachlorotetrabismuthate(III) (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 841-844 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; bismuth chloride complexes ; diphenylammonium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [(C6H5)2NH2]4 +[Bi4Cl16]4− crystallizes in the triclinic space group $$P\bar 1$$ witha=11.835(2),b=12.393(2),c=12.625(3)Å, α=108.37(3), β=108.69(3), γ=96.00(3)° andD c=2.135 g cm−3 forZ=1. The [Bi4Cl16]4− anion is a centrosymmetric cluster of four distorted edge-sharing BiCl6 octahedra. The ranges of the Bi−Cl bonds are 2.484(4)–2.606(3)Å for Bi−Cl(terminal), 2.691(3)–2.956(4)Å for Bi-Cl(µ2), and 2.960(3)–3.120(4)Å for Bi-Cl(µ3). The cations and anions are held in place by weak hydrogen bonds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01671080
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  • 4
    Electronic Resource
    Electronic Resource
    Crystal structure of a bulky cyclic sulfite (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 215-218 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; cyclic sulfite ; pentacycloundecane-8 ; 11-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of the cyclic sulfite derived from the reaction of thionyl chloride withendo-8-hydroxy-exo-8-(endo-8′-hydroxypentacyclo[5.4.0.0.2,6.03,10.05,9]undec-exo-8′-yl)pentacyclo-[5.4.0.0.2,6.03,10.05,9]undecane is reported. All bond lengths and angles are consistent with the strained cage geometry. A static disorder of the terminal oxygen was found to be present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665171
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  • 5
    Electronic Resource
    Electronic Resource
    Structure of the pinacol formed via sodium-promoted reductive dimerization of 12-methyleneheptacyclo-[6.6.02,6.03,13.04,11.05,9.010,14]tetradecan-7-one (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 417-420 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; pinacol ; reductive dimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The pinacol resulting from sodium promoted reductive coupling of a methyleneheptacyclo-[6.6.02,6.03,13.04,11.05,9.010,14]tetradecanone possesses a conformation in which equivalent groups on the pinacol carbon are virtually perpendicular to each other. This rotation minimizes steric interactions, thus the geometries of all the fragments in the molecule are within expected values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665280
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  • 6
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of 1-vinyl-3-methyl-imidazolium iodide, C6H9N2I (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 601-603 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; imidazolium ; vinyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes with two independent molecules in the unit cell. The two molecules arecis-trans isomers. Crystal data: orthorhombic, P212121,a=7.0417(6),b=9.5341(9),c=25.411(2) Å,Z=8. The crystal structure has been solved by automated Patterson methods and refined toR=0.024 for 1843 observed reflections.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01667031
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular structure of 3-(3-oxo-bicyclo[2.2.1]hept-5-en-2-yl)-oxirane-2-carboxylic acid methyl ester (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 81-84 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; epoxy ester
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of an epoxy ester is described. The structure has been solved by vector search methods and refined by least squares methods toR 1=0.0372 [I〉2σ(I)]. The structure consists of two independent molecules in the asymmetric unit. These molecules are chemically the same. Crystal data: C11H12O4, triclinic, space group $$P\bar 1$$ ,a=10.324(3),b=10.553(7),c=10.869(5)Å, α=61.77(4), β=88.64(4), γ=88.16(6)°,V=1042.7(9)Å3,Z=4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02018702
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  • 8
    Electronic Resource
    Electronic Resource
    Crystal structure of a highly hydrated tristrontium phosphate, Sr9(PO4)6·16H2O (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 341-346 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; hydrated phosphate ; layer-type structure ; strontium phosphate ; strontium phosphate hydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of a highly hydrated tristrontium phosphate, nonastrontium hexakis(phosphate) hexadecahydrate, Sr9(PO4)6·16H2O, has been determined by single crystal X-ray diffraction. The crystals are monoclinic,a=15.203(2),b=6.488(1),c=18.984(7) Å, β=98.42(2)o, space groupP2/c (No. 13),Z=2,V=1852.3 Å3,d c =2.951 Mg·m−3. The structure was refined by full-matrix least-squares techniques toR=0.038,R w =0.051, for 2329 reflections with I≥3σ(I). The structure can be described in terms of a layer-type arrangement parallel to (100). One layer consists of a compact assembly of columns of Sr and PO4 ions in a pseudohexagonal arrangement resembling an apatitic structure. A second layer containing all the water molecules and one PO4 ion that occupies the interstitial space may be referred to as the hydrated layer. The structure has an overall similarity to that of octacalcium phosphate and can be considered as a model for amorphous calcium phosphate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01677098
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular structure of [(tBu)2Al(μ-NHtBu)]2 (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 563-567 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; aluminum ; amide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of [(tBu)2Al(μ-NHtBu)]2 has been determined. The unit cell contains two independent molecules with only slight variation in the orientation of thetert-butyl ligands. Crystal data: Triclinic, $$P\bar 1$$ ,a=9.0138(6),b=10.2944(8),c=15.791(1) Å, α=91.262(6), β=89.822(6), γ=106.141(6)°,V=1407.2(2) Å3,Z=2,R=0.039,R w=0.041.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01668416
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  • 10
    Electronic Resource
    Electronic Resource
    Crystal structure of 5-(p-methoxyphenylamino)indane and AM1 calculations on N-arylamines derivatives, precursors of phenothiazine drugs (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 735-739 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; diphenyl amines ; AM1 calculations ; phenothiazines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structural determination by X-ray crystallography of the titled N-arylamine 4a, as well as AM1 calculations on a series of derivatives (4b–c, 5a–c), are reported. The compound 4a is monoclinic P21/c with a = 7.656(3), b = 23.655(5), c = 7.686(9) Å, β = 112.59(6)°, V = 1285.2(2) Å3 and Z = 4. This structure has been used as a template for the building of some others derivatives used for AM1 calculations. The results show that the cyclization position on the aromatic rings, which can lead to two regioisomers, depends on the nature of the benzylic substituants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021860410863
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  • 11
    Electronic Resource
    Electronic Resource
    Synthesis, characterization, and X-ray crystal structure of di-(2,4-imidazolidinedione-5-ethyl)disulfide, C10H14N4O4S2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 761-765 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; noncentrosymmetric ; disulfide ; imidazolidinedione ; homocystine hydantoin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Di-(2,4-imidazolidinedione-5-ethyl)disulfide or homocystine hydantoin, C10H14N4O4S2 (I), crystallizes in the non-centrosymmetric space group P21 (No. 4) with two molecules in the unit cell with a = 7.132(1), b = 9.282(2), c = 10.770(2) Å and β = 105.68(1)°. The two imidazolidinedione rings are planar with a dihedral angle of 46.9°. The rings are joined by a diethyl disulfide bridge at chiral centers on the rings. The C-S-S-C torsion angle is −80°(−sc). The absolute stereochemistry of the chiral centers was determined to be (5S, 5′S), η = + 0.92 (11). Important bond distances include: S-S = 2.022(4); S-C (mean) = 1.809(8); and C=O (mean) = 1.224(7) Å. The compound is stabilized by a network of intermolecular carbonyl-to-amine hydrogen bonding and van der Waals cohesive forces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021816628610
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  • 12
    Electronic Resource
    Electronic Resource
    Crystal structure of a macrocyclic tetraamine isocyanato zinc(II) complex (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 831-834 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; macrocyclic tetraamine ; isocyanato zinc(II) complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The complex, [Zn(L)(NCO)]Cl · 3H2O (1) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane), has been synthesized and structurally characterized. 1 crystallizes in the monoclinic system, space group P21/n with a = 10.530(3), b = 9.315(2), c = 27.188(3) Å, β = 92.58(1)°, V = 2664.1(9)Å3, and Z = 4. The zinc atom is in a distorted squarepyramidal environment with the four nitrogen atoms of the macrocycle and one nitrogen atom of the isocyanate ligand.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021831921283
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  • 13
    Electronic Resource
    Electronic Resource
    Synthesis and crystal structure of macrocyclic nickel(II) complex bridged by chromate (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 867-870 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; macrocyclic nickel(II) complex ; chromate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A novel compound catena-(μ-CrO4-O,O′)[Ni(L1)Ni(L2)] 3H2O (1) (L1 = 3,5,10,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane and L2 = 2,5,9,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized for the first time and structurally characterized. 1 crystallizes in the triclinic space group Pī with a = 9.623(1), b = 10.084(1), c = 12.723 (3) Å, α = 66.74(2), β = 75.20(1), γ = 72.02(1)°, V = 1066.2(3) Å3, and Z = 2. The coordination environment around the Ni(II) ions is an axially elongated octahedron with the secondary amines of the isomeric ligands and two oxygen atoms of [CrO4]2−.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022890217250
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  • 14
    Electronic Resource
    Electronic Resource
    Synthesis, characterization, peripheral studies, and structural analysis of E-4-(N-methylanilino)-3-pentene-2-one, C12H15NO (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 899-903 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; ir/nmr ; β-amino-α ; β-unsaturaled ketone ; noncentrosemmtric ; enamino ketones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystallographic structural refinement of E-4-(N-methylanilino)-3-pentene-2-one (I) has been carried out by means of three-dimensional single-crystal X-ray diffractometry. The title compound crystallizes in space group C2 (No. 5,Z = 4). The lattice constants are a = 21.543(4), b = 6.433(1), c = 8.019(2) Å, and β = 97.82(3)°. Characterizations include physical property determinations and spectrometric identifications employing IR, 1H and 13C NMR, and X-ray powder analyses. The molecules in the crystal lattice are held together by van der Waals forces. Selected bond distances and angles are presented and discussed as well as synthesis and peripheral studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022802619976
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  • 15
    Electronic Resource
    Electronic Resource
    The structure of N-(1H-benzo[d]imidazol-2-ylmethyl)-N-(2,6-dichlorophenyl)amine (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 145-147 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; benzimidazole ; antimicrobial activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The N-(1H-benzo[d]imidazol-2-ylmethyl)-N-(2,6-dichlorophenyl)amine, C14H11N3Cl2, M r = 292.17, crystallizes in the orthorhombic space group Pbca with unit cell parameters a = 10.707(2), b = 9.615(2), c = 25.944(6) Å. The benzimidazole ring system is planar and makes a dihedral angle of 77.8(1)° with the phenyl ring. The structure is stabilized by an N–H···N hydrogen bond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022497931783
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  • 16
    Electronic Resource
    Electronic Resource
    Synthesis and structural characterization of a novel polymeric praseodymium(III) complex with a new flexible double betaine (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 177-183 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; coordination polymer ; praseodymium(III) carboxylate complex ; double betaine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A novel polymeric Pr(III) complex with a new double betaine, namely [{Pr(L1)1.5(H2O)2} n ][ClOli4]3 n ·nH2O (1) (L1 = 1,4-diazoniobicyclo[2,2,2]octane-1,4-dipropionate), has been synthesized and characterized by X-ray analysis. In the title complex, the Pr(III) atom is nine-coordinated by seven oxygen atoms from five L1 ligands and two aqua ligands. Each pair of adjacent praseodymium(III) atoms is linked by a pair of μ3 chelating and bridging carboxylate groups, thus forming an infinite metal···metal chain running parallel to the a direction, and such chains are cross-linked by flexible backbones of L1 ligands into a three-dimensional network with the perchlorate anions and lattice water molecules accommodated in the interstitial space. The title complex crystallizes in the monoclinic space group P21/n with a = 8.085(2), b = 14.316(3), c = 29.775(6) Å, β = 103.04(3)° and Z = 4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022414109261
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  • 17
    Electronic Resource
    Electronic Resource
    Crystal structures of three substituted pentacyclo[5.4.0.02,6.03,10.05,9]undecanes (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 251-258 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; pentacycloundecane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of three compounds formed via ultimate nucleophilic attack of unsaturated hydrocarbon fragments are reported. Geometries of the bis(vinyl)-, mono(vinyl), and bis(ethynyl)-substituted PCU species are unexceptional. The crystal structures are dictated by the availability of intermolecular hydrogen bonding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021893001351
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  • 18
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    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 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 497-499 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; tricyclodecadienone ; enaminone ; resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of (+)-(1R, 2S, 6R, 7S, 1′R)-5-(1′-phenylethylamino)-endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-one is described. Based on the known absolute configuration (R) of the α-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 〉 2σ(I)). Crystal data: C18H19NO, monoclinic, space group P21, a = 6.7406(4), b = 9.959(2), c = 11.3123(8)Å, β = 102.969(5), V = 740.0(2)Å3, and Z = 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021733108852
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  • 19
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    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 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 493-495 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; tricyclodecadienone ; enaminone ; dynamic kinetic resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of (−)-(1R, 2S, 6R, 7S, 2′S)-5-(2′-hydroxymethyl-pyrrolidin-1′-yl)-endo-tricyclo[5.2.1.02,6]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 〉 2σ(I)). Crystal data: C15H19NO2, monoclinic, space group P21, a = 6.0757(4), b = 11.3473(5), c = 9.5114(7)Å, β = 104.686(6)°, V = 634.32(7)Å3, and Z = 2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021781024782
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  • 20
    Electronic Resource
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    The crystal structure of 5α,9α-peroxyergosta-7,22-dien-6-one-3β-ol acetate (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 239-241 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; ergosterol peroxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Ergosterol acetate, in pyridine, reacts with hydrogen peroxide and catalytic amounts of FeCl3 to afford the unusual product 5α,9α-peroxyergosta-7,22-dien-6-one-3β-ol acetate. The peroxide, in the title structure, is seen to bridge the C5 and C9 positions of the sterol backbone. Crystal data: C30H44O5, orthorhombic, P212121, a = 6.552(2), b = 11.048(8), c = 37.60(2), V = 2772(3)Å3, Z = 4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022486730643
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  • 21
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    The crystal structure of hexabenzoylhexaazaisowurtzitane (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 593-596 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; cage compound ; hexabenzoylhexaazaisowurtzitane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of an interesting cage compound is described. Crystal data: C48H36N6O6·(CH3)2CO; monoclinic; space group: P2 1 /n; a = 14.948(3) Å, b = 15.079(3) Å, c = 19.539(4)Å, β = 93.93(3)°, V = 4394(2)Å3; and Z = 4.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022452707772
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    Structural study of the molecular complex in crystals of brucine with pantolactone (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 121-125 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; brucine ; pantolactone ; molecular complex ; chiral resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We have determined an X-ray crystal structure, a = 12.482(1), b = 14.349(1), c = 14.342(1) Å, orthorhombic, P212121 for a molecular complex of brucine with pantolactone. The crystal structure is composed of corrugated sheets of brucine molecules containing the guest pantolactone molecules. The conformational twist of the pyrrolidine ring in brucine may probably be important in projecting the amine N2 to provide a strong and specific binding site for a chiral complexation. The pseudo-equatorial orientation of the hydroxyl group of the pantolactone anchors itself for binding via hydrogen bonding. In the crystal packing, the pantolactone molecules form helices and the brucine molecules are attached to these helices by O=H···N hydrogen bonds.
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    Highly stereoselective sodium borohydride promoted reduction ofendo-5-acetyl-1,2,3,4-tetrachloro-7,7-dimethoxynorborn-2-ene (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 657-660 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; norbornene ; stereoselective reduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Racemicendo-5-acetyl-1,2,3,4-tetrachloro-7,7-dimethoxynorborn-2-ene was stereoselectively reduced by sodium borohydride to give only theS,S orR,R diastereomers. The crystal structure of the product displays no unusual features.
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    Structure of 2-acetoxy-1,2-di(1-adamantyl)ethanone (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 291-294 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; 1,2-di(1-adamantyl)ethene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of 2-acetoxy-1,2-di(1-adamantyl)ethanone is reported. The steric requirements of the two adamantyl groups affect the structure in three ways—a slight elongation of the central bond, a small expansion of the angles about the central bond, and a conformation in which the C(sp2)-connected adamantyl group virtually bisects the large substituents attached to the sp3 carbon.
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    Structure of a PCU-derived pinacol formed via sodiumpromoted reductive dimerization of pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione monoethylene ketal (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 517-520 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; pinacol ; reductive dimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The pinacol resulting from sodium promoted reductive coupling of pentacyclo[5.4.0.02,6.-03,10.05,9]undecane-8,11-dione monoethylene ketal possesses a conformation, dictated by intramolecular hydrogen bonding, that lies midway between eclipsed and staggered. The C−C and C−O distances in the pinacol unit are, respectively, longer and shorter than usual, and all parameters are as expected.
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    Crystal and molecular structure determination, TGA-DTA, and infrared and Raman spectra of rubidium nitroprusside, Rb2[Fe(CN)5NO] (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 325-330 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; rubidium nitroprusside ; IR ; Raman ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound, Rb2[Fe(CN)5NO], crystallizes in the space group P212121, witha=5.687(1),b=15.956(2),c=12.645(3) Å, andZ=4. Anions are in equivalent C1 sites (one per asymmetric unit) and are slightly distorted octahedra (C4v ideal symmetry). TGA and DTA curves and vibrational (infrared and Raman) spectra of Rb2[Fe(CN)5NO] were obtained. Results are interpreted in view of the crystal structure of the compound and the behavior of related substances.
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    Thermodynamic vs. kinetic control in the Diels-Alder cycloaddition of cyclopentadiene to 2,3-dicyano-p-benzoquinone (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 281-286 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; cyclopentadiene ; 2,3-dicyano-p-benzoquinone ; Diels-Alder reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Diels-Alder cycloaddition of cyclopentadiene (1a) to 2,3-dicyano-p-benzoquinone (2a), when performed in methanol solvent at ambient temperature, proceeds with kinetic control to afford 1α,4α,4aβ,8aβ-tetrahydro-5,8-dioxo-1,4-methanonaphthalene-4a,8a-dicarbonitrile (7, 77% yield). However, when this cycloaddition is performed by refluxing an equimolar solution of1a and2a in benzene for 3 h, the product of thermodynamic control, i.e., 1α,4α,4aα,8aα-tetrahydro-5,8-dioxo-1,4-methanonaphthalene-6,7-dicarbonitrile (3a) is obtained in 64% yield. The structure of3a was confirmed by an analysis of the reduced intramolecular photocyclization product,9.
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    Crystal and molecular structure of (2E,4S,10R)-4-hydroxy-2-undecen-10-olide (nor-patulolide C), C11H18O3 (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 305-308 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; undecen-olid ; nor-patulolide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The stereogeometry and absolute configuration of the title compound has been proved by an X-ray diffraction analysis. Crystal data: monoclinic, P21,a=7.7976(2),b=7.8288(2),c=8.9791(4) Å, β=90.331(4)o, Z=2. The crystal structure has been solved by vector search methods and refined toR=0.042 for 1798 observed reflections.
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    Crystal and molecular structure of diphenylphosphinylacetic acid (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 361-364 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; carboxylic acid ; phosphine oxide ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Diphenylphosphinylacetic acid crystallizes in the monoclinic space groupP2l/n with unit cell dimensionsa=5.6875(7),b=17.049(4),c=13.471(2) Å, β=93.36(1)° and Z=4. The molecular packing consists of hydrogen bonded chains arising from intermolecular interactions between a carboxylic acid hydroxyl group and an oxygen of an adjacent phosphine oxide moiety.
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    Tetracyclo[6.3.0.04,11.05,9]undecane-2,7-dione (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 425-428 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; tetracyclo[6.3.0.04,11.05,9]undecane-2,7-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The compound crystallizes in the triclinic space group, $$P\bar 1$$ , witha=6.7702(4),b=7.0180(4),c=9.1960(7) Å, α=92.457(6), β=96.150(6), γ=93.444(5)°, andZ=2. The structure contains a rather short intramolecular H...H contact of 2.26(4) Å.
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    Crystal structure of strontium potassium arsenate octahydrate (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 741-746 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; hydrated ions ; ionic hydration ; strontium arsenate ; struvites ; struvite-type structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of strontium potassium arsenate octahydrate, SrKAsO4·8H2O, has been determined by single crystal X-ray diffraction. The crystals are tetragonal, a = 7.144(1), c = 23.613(2) Å, space group I41md (No. 109), Z = 4, V = 1205.1(1) Å3, and d c = 2.258 g cm−3. All cations and anions in this compound are completely surrounded by water molecules. Sr2+ and K+ ions are each coordinated to eight water molecules arranged in an approximately square antiprism. The [Sr(H2O)8]2+ polyhedron shares one face of four water molecules with a [K(H2O)8]+ polyhedron forming O4-Sr-O4-K-O4 polyhedra. The O4-Sr-O4-K-O4 units are linked together through a pair of edge-sharing linkages of the outer water molecules, alternating along the a-axis and b-axis. The hydrated cation polyhedra appear to define the host lattice, which accommodates the AsO 4 3- ion in the interstitial space. The environment of the AsO 4 3- ion consists of 16 water molecules; each oxygen atom is the acceptor in hydrogen bonds from four water molecules. The pair distances associated with this environment may be used in investigations of the structure of hydrated 4 n- ions in solutions. Each water molecule is coordinated to one Sr and one K, and hydrogen bonded to two O atoms of two different AsO 4 3- ions. There is no hydrogen bonding between water molecules.
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    Crystal structures of a series of 3,7-bis-(arylazo)-1,3,5,7-tetraazabicyclo[3.3.1]nonanes (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 797-809 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; bicyclononane ; triazene ; bis-triazene ; nitrile substituent ; nitro substituent ; trifluoromethyl substituent ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a series of 3,7-bis(arylazo)-1,3,5,7-tetraazabicyclo[3.3.1] nonanes (1a–d) have been determined by single crystal X-ray diffraction analysis. All four compounds have the same feature, that the tetraazabicyclononane unit assumes a cage-like structure with the aryltriazene moieties lying parallel to one another so that the aryl rings are held together by π – π stacking. Crystal data: 1a C17H18N10O4, triclinic, space group P − 1, a = 9.8899(10), b = 13.0845(13), c = 16.458(2) Å, α = 94.095(2)°, β = 107.004(2)°, γ = 111.027(2)°, V = 1863.5(3) Å3 and Z = 4; 1b, C19H18F6N8, orthorhombic, space group Pbca, a = 15.3210(8), b = 10.9512(6), c = 24.5698(13) Å, V = 4122.4(4) Å3 and Z = 8; 1c C19H18N10, monoclinic, space group P21/n a = 6.3742(6), b = 13.7343(13), c = 21.542(2)Å, β = 97.738(2)°, V = 1868.8(3) Å3, and Z = 4; 1d, C19H18N10, monoclinic, space group P21/c, a = 18.205(2), b = 17.398(2), c = 12.784(12) Å, β = 109.480(2)°, V = 3818.0(6) Å3, and Z = 8.
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    Characterization and structural analyses of trimethoxy and triethoxybenzo[b]thiophene (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 289-295 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; centrosymmetric ; methoxybenzo [b] thiophene ; estrogen receptor ; tubulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structures of two methoxybenzo [b] thiophenes have been determined by three-dimensional, single-crystal X-ray diffractometry. Both 3-(3′,4′,5′-trimethoxybenzoyl)-2-(4′-methoxyphenyl)-6-methoxybenzo[b]thiophene and 3-(3′,4′,5′-triethoxybenzoyl)-2-(4′-methoxyphenyl)-6-methoxybenzo[b]thiophene (hereafter referred to as I and II, respectively) crystallize in the triclinic centrosymmetric space group $$P \bar 1$$ (No. 2, C1) with two formula units per cell with a = 6.842(1) Å, b = 12.602(2) Å, c = 13.815(2) Å, α = 94.80(1)°, β = 98.27(2)°, and γ = 100.59(2)° and a = 10.600(1), b = 11.415(2), c = 12.137(2) Å, α = 94.57(1)°, β = 101.18(1)°, and γ = 110.45(1)°, respectively. The phase problems were solved by direct methods and the respective final full-matrix least-squares refinements converged to R = 0.039 and 0.068. The structures differ in the orientation of the trimethoxy and triethoxy groups of the benzoyl ligands. The molecules in the crystal lattice are held together by van der Waals forces. Selected bond distances, angles, and torsion angles are tabularized as well as reference to the synthesis of the title compounds and peripheral studies.
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    Synthesis and crystal structure of a polymeric erbium(III)–sodium(I) coordination complex of picolinic acid N-oxide (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 413-418 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; coordination polymer ; erbium(III)–sodium(I) carboxylate complex ; picolinic acid N-oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new Er(III)–Na(I) coordination polymer of stoichiometry [NaEr2L5(H2O)6(NO3)](NO3)·3.5H2O (HL = picolinic acid N-oxide) has been synthesized and characterized by single-crystal X-ray analysis. Crystals are triclinic, PĪ with a = 9.823(2), b = 12.453(2), c = 20.643(4) Å; α = 98.49(3), (β = 101.40(3), γ = 108.69(3)°; V = 2284(1) Å3; Z = 2. Of the two independent eight-coordinate erbium(III) ions in this complex, one is surrounded by four bidentate chelating L ligands, and the other by one bidentate chelating L ligand, four aqua ligands and two anti-carboxylate oxygen atoms from two neighboring [ErL4] units. The sodium(I) ion is in a distorted octahedral environment, being coordinated by a unidentate nitrate anion, three aqua ligands and two anti-carboxylate oxygen atoms from two adjacent [ErL4] units. The complex is built from zigzag chains of syn-anti carboxylate-bridged erbium(III) moieties directed in the a direction, which are cross-linked pairwise by aqua-bridgeddimericsodium(I) units. The resulting composite polymeric chains are further connected by hydrogen bonds to form a three-dimensional network.
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    Crystal structure and two-stage hydrolysis of dimethoxo (meso-tetra(4-methoxyphenylporphyrinato))tin(IV), Sn(tmpp)(OMe)2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 481-486 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; tin porphyrin ; two-stage hydrolysis ; methanolate ; trans equivalent axial ligand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In this work, we determine the crystal structure of dimethoxo(meso-tetra(4-methoxyphenylporphyrinato))tin(IV), Sn(tmpp)(OMe)2 (1). Experimental results indicate that the tin atom has an octahedral geometry. The geometry around the tin center has Sn(1)–O(5) = 2.020(6), Sn(1)–O(6) = 2.003(7) Å and an average Sn(1)–N = 2.10(1) Å. The two methoxo groups are unidentately coordinated to the tin(IV) atom. Two-stage hydrolysis of Sn(tmpp)(OMe)2 in CDCl3 was observed by 1H and 13C NMR spectroscopy. Compound (1) crystallizes in the space group P21/n with a = 14.7492(1), b = 19.2022(3), c = 16.0806(2) Å, β = 94.104(1)°, and Z = 4.
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    Synthesis and structural characterization of a novel polymeric gadolinium(III)–copper(II) complex of iminodiacetic acid (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 475-479 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; coordination polymer ; gadolinium(III)-copper(II) complex ; iminodiacetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A novel polymeric Gd2Cu3 complex of iminodiacetic acid (H2L1=NH{CH2COOH}2), namely, Gd2Cu3(L1)6, 1, has been synthesized and structurally characterized. In the title complex, the Gd3+ ion is nine-coordinated by six O atoms from three bidentate chelating carboxylate groups and three O atoms from three anti-anti bridging carboxylic groups of six L1 ligands; the Cu2+ ion is six-coordinated by four O and two N atoms from two chelating L1 ligands. Each pair of Gd(III) atoms is bridged by three L1 ligands, each of which also chelates with one copper(II) ion, thus forming a Gd2Cu3 cluster unit. Such cluster units are cross-linked by flexible L1 ligands into a three-dimensional coordination framework. The title complex crystallizes in the trigonal space group P-3c1 (No. 165) with a = b = 13.433(4), c = 14.770(6) Å; V = 2308(1) Å3; Dcalca = 1.859 g cm−3; Z = 2.
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    Structure of a deaza dimer of 4-methyl-3H-1,2,4-triazole-3,5(4H)-dione (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 15-18 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; dimer ; triazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the monoclinic space group, P21/n; a = 9.0024(5), b = 5.8135(3), c = 15.2232(8) Å, β = 91.153(4)° Z = 4; and R = 0.050 based on 853 observed, unique reflections. The structure consists of two fused five-membered triazole rings, oriented relative to each other at 152°.
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    Crystal structures of two substituted biphenyl derivatives: 5,5′-di t-butyl-2-2′-biphenyldiol and 5,5′-dimethyl-2,2′-biphenyldiol (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 157-161 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; biphenyl ; mutual orientation ; strong H-bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 5,5′-Di t-butyl-2,2′-biphenyldiol (I), C20H26O2, crystallizes in the orthorhombic space group P212121 with a = 18.243(2), b = 9.947(2), c = 9.685(3) Å, and Z = 4; 5,5′-dimethyl-2,2′-biphenyldiol (II), C14H14O2, crystallizes in the monoclinic space group P21/c with a = 9.959(2), b = 7.932(3), c = 15.392(2) Å, β = 105.43(2)°, and Z = 4. The aromatic rings are tilted by 52.7(1) and 43.8(1)° to each other in compounds (I) and (II), respectively. Strong intra- and inter-molecular H-bonds connect the molecules in the crystals.
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    Synthesis, spectroscopic studies, and crystal structure of tris(tetra-n-butylammonium) hexakisisothiocyanatoindate(III) (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 317-321 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; indium complexes ; isothiocyanate complexes ; octahedral coordination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The reaction of a 1:10 molar ratio between indium chloride and tetra-n-butylammonium thiocyanate in ethanol affords the complex [(n-C4H9)4N]3[In(NCS)6] (1), the structure of which has been established by X-ray diffraction. This compound crystallizes in the cubic space group Pa3¯ with eight formula units in the unit cell. The formula unit consists of three separate cationic tetra-n-butylammonium groups and an independent hexakisisothiocyanatoindium anionic group. The six near linear thiocyanate ligands coordinate octahedrally through the nitrogen atom to the indium metal center. The coordination of the n-butyl groups to the ammonium-nitrogen atom is tetrahedral. The complex has also been characterized by IR, 1H and 13C NMR, physical properties, and X-ray powder analysis.
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    Crystal structures of a series of 3,8-di[-2-aryl-1-azenyl]-1,3,6,8-tetraazabicyclo[4.4.1]undecanes (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 145-156 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; bicycloundecane ; triazene ; bis-triazene ; nitro substituent ; carboalkoxy substituent ; π–π stacking
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a series of 3,8-di[-2-aryl-1-azenyl]-1,3,6,8-tetraazabicyclo[4.4.1]undecanes (1–5) have been determined by single crystal X-ray diffraction analysis. In all five compounds, the tetraazabicycloundecane portion of the molecule assumes a cage-like, folded structure with the aryltriazene moieties aligned approximately parallel; the structure is held in the folded configuration by either intramolecular or intermolecular π–π stacking forces. Crystal data: 1 C19H22N10O4, monoclinic space group P21/c, a = 10.1846(7), b = 9.9556(7), c = 20.819(2) Å, β = 98.725(1)°, V = 2086.5 (3) Å3, Z = 4; 2 C23H28N8O4, triclinic, space group Pī, a = 6.7064(7), b = 12.9662(14), c = 14.054(2) Å, α = 94.796(2), β = 91.621(2), γ = 104.836(2)°, V = 1175.7(2) Å3, Z = 2; 3 C19H22N10O4, monoclinic, space group P21/c, a = 14.237(2), b = 13.520(2), c = 11.5805(12) Å, β = 113.514(2)°, V = 2044.0(4) Å3, Z = 4; 4 C21H22N10, monoclinic, space group C2/c, a = 54.247(3), b = 11.5531(7), c = 12.9670(7) Å, β = 95.710(1)°, V = 8086.4(8) Å3, Z = 16; 5 C25H32N8 04, monoclinic, space group P21/c, a = 10.2908(7), b = 16.5687(12), c = 15.1662(10) Å, β = 94,188(1)°, V = 2579.0(3) Å3, Z = 4.
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    Synthesis and crystal structure of 4,5-dibromo[2.1.1]triblattene (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 351-354 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; dibromotriblattene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reaction of 4-bromopentacyclo[7.3.0.02,7.03,11.06,10]dodec-11-ene (1) with Br2—CCl4 afforded 4,4,5-tribromopentacyclo[7.3.0.02,7.03,11.06,10]dodecane (2) in 89–94% yield. Subsequent treatment of 2 with KOt-Bu-t-BuOH resulted in competitive elimination of the elements of HBr and of Br2 with concomitant formation of 4,5-dibromopentacyclo[7.3.0.02,7.03,11.06,10]dodec-11-ene (3, 76%) and 1 (17%), respectively. The structure of 3 was established unequivocally via application of X-ray crystallographic methods. Crystal data for 3: monoclinic, C2/c, a = 9.895(1), b = 9.0963(7), c = 12.471(1) Å, β = 106.875(8)°, z = 4.
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  • 42
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    Synthesis, crystal structure, and molecular modeling (AM1) of Methyl 6-chloro-4-(2-chlorophenyl)-5-formyl-2-methyl-1, 4-dihydropyridine-3-carboxylate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 237-243 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; AM1 ; x-ray diffraction ; dihydropiridines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis and structural characterization of Methyl 6-chloro-4-(2-chlorophenyl)-5-formyl-2-methyl-1,4-dihydropyridine-3-carboxylate is described. The structure was refined to R1 = 0.0470 for 2665 reflections (with I 〉 2σ(I)). Crystal data: C15H13C12NO3, monoclinic,space group P21/c, a = 11.163(9), b = 14.484(8), c = 9.422(7) Å, V = 1512.9(19) Å3, Z = 4. The results of crystallographic and molecular modeling (AM1) were compared. The Cl atom attached to the phenyl group has two possible orientations, having 75% (sp) and 25% (ap) occupancy, respectively. The molecules in the crystal are held together by means of intermolecular hydrogen bonds of the type N=H...O and by C=H...O interactions.
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    Synthesis and crystal structure of a tetranuclear manganese(IV) cluster [L4Mn4O6](ClO4)4·2H2O (L = 1,4,7-triazacyclononane) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 251-254 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; manganese(IV) cluster ; adamantane-shaped complex ; tetranuclear complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A tetranuclear manganese (IV) complex, [L4Mn4O6](ClO4)4·2H2O (1), with 1,4,7-triazacyclononane (L) as the capping ligands, has been synthesized and characterized by X-ray diffraction; monoclinic, space group P21/n with a = 21.335(6) Å, b = 11.387(3) Å, c = 21.788 (6) Å, β = 111.410 (6)°, V = 4928 (2) Å, Z = 4. Each manganese atom has a distorted octahedral environment comprised of three facially coordinated amine nitrogen atoms and three oxygen atoms, and the cation is an idealized tetrahedron. The Mn4O6 4+ cation corresponds to an adamantane skeleton.
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  • 44
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    Structure of a C2-symmetric bis(benzyloxy)trishomocubanone (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 747-750 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; trishomocubanone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of a bis(benzyloxy)trishomocubanone with molecular C2 symmetry reveals that substitution of benzyloxy groups has little effect on the trishomocubane cage.
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  • 45
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    Crystal structure of ethyl 4-methylthio-3-phenyl-2-thioxo-2,3-dihydro-1,3-oxazole-5-carboxylate (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 237-240 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; 1,3-oxazoline-2-thione ; resonance structures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound C13H13NO3S2 crystallizes in the triclinic space group $$P\bar 1$$ (Z=2) with lattice constantsa=8.382(2),b=10.042(2),c=10.134(2) Å, α=119.35(1)°, β=101.40(1)° and γ=90.54(1)°. The interplanar angle between the least squares planes of the 1,3-oxazoline ring and the phenyl ring amounts to 90.2°, thus hindering conjugation between the benzene and heterocyclic system. The observed bond parameters of the five-membered heterocycle suggest a significant contribution from a zwitterionic dipolar limiting structure [38.7(5)%] to the description of this ring system. The particular contributions of the resonance structures were estimated by calculations using the HOSE model on the base of the observed bond lengths.
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  • 46
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    Synthesis and structure ofexo-11-cyano-endo-11-(trimethylsilyloxy)pentacyclo[5.4.0.02,6.03,10.05,9]undecan-8-one (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 267-271 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; pentacycloundecan-8-one ; pentacycloundecane-8,11-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of an asymmetric pentacyclo[5.4.0.02,6.03,10.05,9]undecan-8,11-dione derivative is reported, in which Me3SiCN has been added across one of the keto groups. The cage structure demonstrates the expected effects of this addition.
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  • 47
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    Structure of the product formed via Cu(I)-promoted oxidative dimerization ofexo-8-ethynylpentacyclo[5.4.0.02,6.03,10.05.9]undecan-endo-8-ol (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 543-547 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; diyne ; oxidative dimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure consists of two acetyl-substituted PCU cages linked by a diyne fragment. The conformation about the linker is midway between staggered and eclipsed, and the acetyl groups are somewhat distorted due to the proximity to the bulky cage units.
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  • 48
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    Crystal structure oftrans-tetrachlorobis[2-(2-1H-imidazolyl)-1H-imidazolium]cadmium(II), [Cd(H3biim)2Cl4] (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 695-699 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; 2,2'-bi-1H-imidazole ; cadmium chloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The reaction between cadmium(II) chloride and 2,2'-bi-1H-imidazole (H2biim) in an acidic solution affords [Cd(H3biim)2Cl4] (H3biim=2-(2-1H-imidazolyl)-1H-imidazolium) in 63% yield. The compound crystallizes in the triclinic space groupP1, wherea=8.072(2),b=8.100(2),c=8.593(2) Å, α=75.89(2), β=62.94(2), γ=63.29(1)°,V=446.4(2) Å3, andZ=1. The central Cd atom exhibits an octahedral geometry composed of a Cl4N2 core. The Cd-N bond distance is 2.392(2) Å. Cd−Cl distances are 2.5919(9) and 2.671(1) Å.
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  • 49
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    X-ray structures of two methoxybenzo[b]thiophenes (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 801-806 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; centrosymmetric ; methoxybenzo[b]thiophene ; estrogen receptor ; tubulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structures of two methoxybenzo[b]thiophenes have been determined by three-dimensional, single-crystal X-ray diffractometry. Both 3-(4′-hydroxy-3′, 5′-dimethoxybenzoyl)-2-(4′-methoxyphenyl)-6-methoxybenzo[b]thiophene and 3-(2′,6′-dimethoxybenzoyl)-2-(4′-methoxyphenyl)-6-methoxybenzo[b]thiophene (hereafter referred to asI andII, respectively) crystallize in the monoclinic centrosymmetric space groupP21/n (No. 14, C 2h 5 ) with four formula units-per cell witha=6.866(1),b=28.638(2),c=11.830(2) Å, and β=105.52(1)° anda=9.328(1),b=7.977(1),c=29.650(4) Å, and β=97.87(1)°, respectively. The phase problems were solved by direct methods and the respective final full-matrix least-squares refinements converged toR=0.046 and 0.031. The structures differ in the positioning of the dimethoxy groups of the benzoyl ligands and the addition of a hydroxyl group inI. The molecules in the crystal lattice are held together by van der Waals forces plus the addition of hydrogen bonding in compoundI. Selected bond distances and angles and torsion angles are tabularized.
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  • 50
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    Reaction of vinylmagnesium bromide with hexacyclo[10.2.1.02,11.04,9.04,14.09,13]pentadeca-5,7-diene-3,10-dione: Transannular hemiketal formation (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 429-433 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; hexacyclopentadeca-5,7-diene-3,10-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reaction between vinylmagnesium bromide and the cage dione leads to attack of only one equivalent of Grignard and intramolecular nucleophilic attack on the second ketone. The product compound crystallizes in the monoclinic space group, P21/a, witha=9.509(1),b=11.071(2),c=12.492(4) Å, β=104.32(2)°, andZ=4.
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    The crystal and molecular structure of 6,8,15,16b,16c,17-hexahydro-16b,16c-diphenyl-7H,16H-6a,7a,15a,16a-tetraazanaphtho[5,6]azulano[2,1,8-ij]naptho[f]azulene-7,16-dione (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 365-368 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; receptor ; clip shaped molecule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a clip containing molecule is described. The structure was solved by vector search methods and refined by least squares methods toR l=0.0768 [I〉2σ(I)]. Crystal data: C40H30N4O2·HCCl3, triclinic, space group $$P\bar 1$$ ,a=9.302(2),b=12.981(2),c=15.765(2)Å, α=65.91(2)°, β=76.40(2)°, γ=80.15(1)°,V=1682.9(4)Å3, Z=2.
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    Synthesis and X-ray analysis of 1-((1S)-phenylethyl)-azetidine-(2R)-piperidinamide (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 639-642 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; chiral auxiliaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of a new azetidine-2-carboxylic amide derivative is described. The structure was solved by direct methods and refined by least squares methods toR1=0.0393 for 4264 reflections (withI〉2σ(I)) The structure consists of two independent molecules which are chemically the same with slight differences in geometry. Crystal data: C17H24N2O, monoclinic, space groupP21,a=8.3782(4),b=20.0342(13),c=9.7769(8) Å, β=109.687(6)°,V=1545.1(2)Å3,Z=4.
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    Crystal structures of two 1,2-bis-(1-aryl-3-methyltriazene-3-yl-)ethanes with aryl substituents of opposite polarity (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 5-10 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; triazene ; bis-triazene ; nitrile substituent ; methoxy substituent ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of 1,2-bis-{1-(2-cyanophenyl)-3-methyltriazen-3-yl-}ethane (1) and 1,2-bis-{1-(2-methoxyphenyl)-3-methyltriazen-3-yl-}ethane (2) have been determined by single crystal X-ray diffraction analysis. Bis-triazene (1) exists as the “staggered” conformation in the solid state, with an anti-anti configuration around the N2–N3 bond of the triazene units, whereas 2 assumes a “gauche” conformation with the syn-syn configuration in the triazene units. Crystal data: 1 C18H18N8, triclinic, space group P −1, a = 6.108(2), b = 8.118(3), c = 9.600(4)Å, α = 101.37(7)°, β = 96.47(7)°, γ = 102.71(5)°, V = 449.1(3)Å3, Z = 2; 2 C18H24N6O2, monoclinic, space group P 21/n, a = 13.119(5), b = 7.745(2), c = 19.201(2)Å, β = 96.47(7)°, V = 1910.3(9)Å3, Z = 4.
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    Crystal structures of the hydrated disodium and paraquat salts of 1,8-disulfonato-3,4,5,6-acridinetetracarboxylic acid (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 39-46 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; 1,8-disulfonato-3,4,5,6-acridinetetracarboxylic acid ; 3,4,5,6-tetracarboxyacridine-1,8-disulfonate ; paraquat ; hydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Two hydrated salts of 1,8-disulfonato-3,4,5,6-acridinetetracarboxylic acid, H2L, have been characterized by single-crystal X-ray analysis. Compound 1, Na2L·9 $$ - \frac{1}{2}$$ H2O, crystallizes in the monoclinic space group C2/c with a = 42.005(1), b = 6.838(1), c = 23.807 (1) Å, β = 122.71 (1)°, and Z = 8. Compound 2, (paraquat)L·2H2O, belongs to the triclinic space group $${P\bar 1}$$ with a = 9.940(1), b = 11.543(1), c = 14.033(1) Å, α = 105.45(1), β = 95.82(1), γ = 100.14(1)° and and Z = 2. All four carboxyl groups in the 3,4,5,6-tetracarboxyacridine-1,8-disulfonate dianion L2− are un-ionized. In 1 the distorted octahedrally coordinated sodium cations, the anions, and the lattice water molecules are joined together by hydrogen bonds to generate a three-dimensional network. In the crystal structure of 2, a host framework composed of L2− ions and water molecules accommodate the paraquat dications within two channel systems running parallel to the a and b axes.
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    Crystal structures of four dibromomethylene-functionalized cage compounds (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 259-266 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; heptacyclotetradecane ; hexacyclotetradecane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystal structures of four dibromomethylene-functionalized hexa- and heptacyclotetradecane cages are reported. 7-(Dibromomethylene)heptacyclo[6.6.0.02,6.03,13.04,11.05,9.010,14]tetradecane (3): orthorhombic, Pnma, a = 14.744(1), b = 11.237(1), c = 7.4625(7) Å Z = 4; R = 0.0531 for 504 observed reflections. 7,12-Bis(dibromomethylene)heptacyclo[6.6.0.02,6.03,13-04,11 .05,9.010,14]tetradecane (4): monoclinic, I2/a, a = 11.257(1), b = 9.5844(8), c = 13.884(2) Å, β = 92.254(8)° Z = 4; R = 0.0413 for 663 observed reflections. 10,14-bis(dibromomethylene)hexacyclo[6.6.0.02,6.03,13.04,11.05,9]tetradecane (6): monoclinic, P21/n, a = 8.118(1), b = 15.273(4), c = 12.826(3) Å, β = 104.20(1)° Z = 4; R = 0.0384 for 1392 observed reflections. 14-(dibromomethylene)hexacyclo[6.6.0.02,6.03,13.04,11.05,9]tetradecan-10-one (7): monoclinic, P21/n, a = 8.2879(7), b = 15.273(1), c = 10.0565(9) Å, β = 92.271(8)° Z = 4; R = 0.0320 for 1402 observed reflections. The functional groups lead to slight shortening of bond lengths.
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    A dinuclear cyano-bridged complex based on hexacyanoferrate(III) and samarium(III) nitrate: synthesis and crystal structure (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 303-307 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; samarium(III) complexes ; iron(III) complexes ; cyanide-bridges ; dinuclear complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new complex, [Sm(DMF)4(H2O)4Fe(CN)6]·H2O (DMF = N, N-dimethylformamide), has been synthesized and characterized by X-ray single crystal structure and thermogravimetric analyses. The complex crystallizes in the P21/n space group, with lattice parameters a = 17.583(4) Å, b = 8.870(2) Å, c = 19.845(6) Å, β = 95.98(3)°, V = 3078(1) Å3, D x = 1.679 Mg m−3, D m = 1.65(1) Mg m−3, Z = 4. The molecular structure shows that a cyano-bridged bimetallic structure is obtained. The Sm atom is coordinated by eight oxygen atoms of four water molecules and four DMF molecules and one nitrogen atom of the bridging cyanide ligand. The iron atom assumes approximately an octahedral environment surrounded by six CN ligands. The hydrate water molecule is hydrogen-bonded to one of the O atoms bound to Sm. Each terminal CN ligand of the Fe(CN) 6 3− entity is hydrogen-bonded to some O atoms of water molecules. An infrared spectrum is also reported.
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    Gold(III)-pteridine compounds: synthesis, spectral, and X-ray diffraction studies on new adducts between sodium tetrabromoaurate(III) and lumazine derivatives (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 565-570 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; complexes ; pteridine ; lumazine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In aqueous hydrobromic medium, Na[AuCl4] reacts with 1,3-dimethyllumazine (1,3-dimethyl-pteridine-2,4(1H,3H)-dione, DLM) or 1,3,6,7-tetramethyllumazine (DLMD) to give three adducts with simplified formulas Na[AuBr4](DLMD), Na[AuBr4](DLM), and Na[AuBr4](DLM)2. These compounds have been characterized by means of analytical techniques, and IR and NMR spectroscopies. Single-crystal x-ray diffraction studies have been made on the Na[AuBr4](DLM)2 compound. The crystals belong to the orthorhombic Pbca space group, with a = 15.249(1), b = 15.238(2), c = 21.563(2) Å, Z = 8, and R = 0.053. The structure consists of planar [AuBr4]− anions and Na+ cations weakly linked to two crystallographically independent DLM molecules. The Na+ cation interacts weakly with four oxygen and one nitrogen atoms from four different pteridine molecules, its environment may be described as a very distorted square pyramid.
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    Molecular structure of AlH3[N(CH2CH2)3CH]2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 649-651 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; aluminum ; hydride ; complex ; quinuclidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reaction of AlH3[N(CH2CH2)3CH] with hexamethyltrisiloxane, (OSiMe2)3, gives rise to the bis-quinuclidine complex AlH3[N(CH2CH2)3CH]2, which has been characterized by 1H and 13C NMR spectroscopy and X-ray crystallography. The molecular structure of AlH3[N(CH2CH2)3CH]2 consists of a trigonal bipyramidal aluminum with axial coordination of the quinuclidine ligands. Crystal data: orthorhombic, space group Pbcn, a = 10.6895(9), b = 12.266(1), c = 12.3794(9) Å, V = 1623.2(2) Å3, and Z = 4.
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    Synthesis and crystal structure of a new lithium cyclohexaphosphate hydrate: Li6P6O18·10H2O (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 323-327 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; cyclohexaphosphate ; hydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis and crystal structure of a novel hydrate of lithium cyclohexaphosphate are reported. Li6P6O18·10H2O crystallizes in the space group C2/c with a = 15.113(5), b = 12.006(2), c = 15.892(2) Å, β = 122.85(2)°, and Z = 4. The structure consists of P6O18 ring layers stacked along the c direction in between which are located the lithiumions and water molecules. Two LiO4 tetrahedra share common edges with LiO5 pseudosquare pyramids to form two independant Li3O9 units. About 50% of the water molecules have fractional occupancy rates and form fragments of molecules. A linear relationship is established between the relative cell volume V/Z and the hydration degree, n, for all the known hydrates: Li6P6O18·nH2O.
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    Synthesis and structure of a bis(ethynyl)-substituted oxahexacyclic cage ether (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 347-349 
    Details
    ISSN: 1572-8854
    Keywords: Crystal structure ; pentacycloundecane ; triple bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Intramolecular dehydration of a cage-diol results in the title compound. This crystallizes in the monoclinic space group P21/c; a = 8.6403(8), b = 9.5698(7), c = 14.062(1) Å β = 107.47(7)° and Z = 4.
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    A cobalt(II) complex with the N,N,O-tridentate ligand 6-amino-5-formyl-1,3-dimethyluracilato-benzoyl-hydrazone (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 283-286 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; complexes ; cobalt ; benzoylhydrazone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of bis-(6-amino-5-formyl-1,3-dimethyluracilato benzoylhydrazone)cobalt(II) dimethylformamide solvate is described. This compound crystallizes in the triclinic system, space group P1¯, Z = 2 with a = 9.7368(8), b = 12.346(1), c = 17.184(1) Å, α = 78.372(6), β = 74.585(6), γ = 71.113(5)°, and V = 1869.0(3) Å3. The coordination polyhedron around the metal ion displays a slightly flattened M(NNO)2 octahedral shape. Both ligands bind in a trident fashion through the benzoylic oxygen atom, the hydrazone nitrogen atom closer to the uracil ring, and the deprotonated nitrogen atom of the amino group. The two ligands exhibit quite different conformations: one of them is almost planar, whereas the other is severely twisted.
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    Synthesis and crystal structure of 4,4′-bis(4-pyridylethyl)biphenyl, noncovalently hydrogen bonded two-dimensional networks (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 641-646 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; hydrogen bonds ; 1H and 13C NMR ; FTIR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A new pyridine containing compound, 4,4′-bis(4-pyridylethyl)biphenyl 1, was synthesized and its structure was determined by X-ray crystallography. Two kinds of two-dimensional networks linked by hydrogen bonds were obtained with different crystal solvents: 1·2H2O, monoclinic, space group P21/n with a = 8.3280(10), b = 5.5990(10), c = 24.054(4) Å, β = 98.79(2)°, V = 1108.4(3) Å3, Z = 2, Dc = 1.200 g cm−3, R1 = 0.0558; 1·CH3OH·2H2O, triclinic, space group P-1 with a = 8.3310(10), b = 12.861(2), c = 13.111(2) Å, α = 64.110(10), β = 75.000(10), γ = 83.750(10)°, V = 1220.7(3) Å3, Z = 2, Dc = 1.177 g cm−3, R1 = 0.0529. It is interesting that in the hydrate the host molecule of 1 contains an essentially flat biphenyl section, while in the methanol complex the host molecule of 1 contains a substantial twist in the center of the biphenyl section. The compounds were also characterized by NMR and FTIR spectroscopies. The 1H and 13C NMR assignments for 1 were carried out by 2D NMR spectral measurements in acetonitrile-d 3.
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    X-ray crystal structures of [HB(3,4,5-Me3pz)3[2Zn, [H2B(3,4,5-Me3pz)2]Zn(μ-3,4,5-Me3pz)2Zn[H2B(3,4,5-Me3pz)2], and [H2B(pz)2]2Zn (pz = pyrazolyl ring) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 665-670 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; poly(pyrazolyl)borate ligands ; zinc(II)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [HB(3,4,5-Me3pz)3]2Zn (1) and [H2B(3,4,5-Me3pz)2]Zn(μ-3,4,5-Me3pz)2Zn[H2B(3,4,5-Me3pz)2] (2) are present in equal amounts in a crystal in the triclinic space group, P-1 with a = 11.5924(11) Å, b = 12.7799(12) Å, c = 15.7317(14) Å α = 107.905(2)° β = 96.796(2)°, γ = 105.786(2)°, and Z = 1. The structure of 1 is a trigonally distorted octahedron and is very similar to the structure of [HB(3,5-Me2pz)3]2Zn showing that the introduction of the third methyl group on the pyrazolyl ring does not impact on structure. [H2B(pz)2]2Zn (3) is orthorhombic, Pca2(1) with a = 10.1473(3) Å, b = 11.1117(2) Å, c = 14.1831(5) Å, α = β = γ = 90° and Z = 4. The zinc(II) centers in both 2 and 3 are similar and have pseudotetrahedral structures.
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    Structure and properties of cobalt(II) complex with a tetraaza macrocycle containing 2-pyridylmethyl pendant arms (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 335-338 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; cobalt(II) complex ; tetraaza macrocycle ; 2-pyridylmethyl pendant arms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The complex [Co(L)]Cl2·10H2O (1) (L = 2,13,-bis(2-pyridylmethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane) has been synthesized and structurally characterized. Compound 1 crystallizes in the triclinic system, space group P-1 with a = 9.731(2) Å, b = 9.789(2) Å, c = 11.998(1) Å, α = 66.66(1)°, β = 76.95(1)°, γ = 87.99(2)°, V = 1020.4(3) Å3, and Z = 1. The crystal structure of 1 shows that the complex is centrosymmetric and the cobalt(II) ion has a slightly distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendent arms at the axial positions. Cyclic voltammetry for 1 undergoes reversible one-electron oxidation to the Co(III) and irreversible one-electron reduction to the Co(I).
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    Crystal structure of 2,3-dihydronaphto[2,3-b) [1,5] dioxepin (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 459-462 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; chemical synthesis ; 2,3-dihydronaphto[2,3-b] [1,5) dioxepin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray single crystal structure of C13H12O2 compound was determined. It crystallizes in the orthorombic space group P212121 with a = 7.8847(7), b = 9.639(1), c = 13.432(2) Å, Z = 4 and V = 1020.8(3) Å3. The final R converged to 0.037 for 1763 independent reflexions. The title compound forms layers parallel to (1 0 0) planes and the three dimensional cohesion of the crystal is assumed by Van der Waals interactions. The molecule consists of two six-membered rings (A and B) and a seven-membered ring (C). A and B rings are planar, whereas the C ring has a chair conformation
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    Near-perfect dipole parallel-alignment in the highly anisotropic crystal structure of 4-iodoacetophenone-(4-methoxyphenylethylidene) hydrazone (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 489-496 
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    ISSN: 1572-8854
    Keywords: Dipole parallel-alignment ; anisotropy ; arene–arene contacts ; intermolecular interactions ; nonlinear optics ; azines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the space group Pna2(1) with cell parameters a = 6.4606(3), b = 7.2155(3) and c = 33.5878(16) Å. The azine shows a gauche conformation about the N—N bond and there is an angle of 58.1° between the benzene rings of each azine. This conformation allows for two intermolecular arene–arene T-contacts between pairs of benzene rings. The characteristic structural motif features T-contact formation between like–substituted arene rings and this architecture results in a highly dipole-parallel aligned lattice. All azines are perfectly colinear within each layer and the orientations of the azines in different layers are nearly the same. The surfaces of the layers exhibit a quadrilateral kite-shaped arrangement of I-atoms and of OCH3-substituents. The layers pack such that the OCH3—carbon atoms are placed above the interstices between the I-atoms in the adjacent layer.
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    Point force and edge dislocation in a two-phase anisotropic medium (1996)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 47 (1996), S. 617-630 
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    ISSN: 1420-9039
    Keywords: Elasticity ; composite material ; Green's function ; plane problem ; anisotropy ; point force ; dislocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract Green's functions are derived for the in-plane deformation due to an in-plane point force and edge dislocation acting at a point in a plane of two joined semi-infinite anisotropic plates. The Lekhnitskii's complex potential approach is used, and a general expression of the solutions is obtained in closed-form. Including the case of an isotropic-anisotropic two-phase medium and the case of an isotropic-isotropic two-phase medium, the solutions are given for all possible combinations of materials with either s1 ≠ s2 or S1=s2, where si and s2 are the roots of the characteristic equation of the material.
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    Nonlinear ray perturbation theory with its applications to ray tracing and inversion in anisotropic media (1996)
    Springer
    Pure and applied geophysics 148 (1996), S. 637-683 
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    ISSN: 1420-9136
    Keywords: Ray tracing ; kinematic inversion ; high-order perturbations ; sensitivity functions ; anisotropy ; cracks ; VSP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A comprehensive approach, based on the general nonlinear ray perturbation theory (Druzhinin, 1991), is proposed for both a fast and accurate uniform asymptotic solution of forward and inverse kinematic problems in anisotropic media. It has been developed to modify the standard ray linearization procedures when they become inconsistent, by providing a predictable truncation error of ray perturbation series. The theoretical background consists in a set of recurrent expressions for the perturbations of all orders for calculating approximately the body wave phase and group velocities, polarization, travel times, ray trajectories, paraxial rays and also the slowness vectors or reflected/transmitted waves in terms of elastic tensor perturbations. We assume that any elastic medium can be used as an unperturbed medium. A total 2-D numerical testing of these expressions has been established within the transverse isotropy to verify the accuracy and convergence of perturbation series when the elastic constants are perturbed. Seismological applications to determine crack-induced anisotropy parameters on VSP travel times for the different wave types in homogeneous and horizontally layered, transversally isotropic and orthorhombic structures are also presented. A number of numerical tests shows that this method is in general stable with respect to the choice of the reference model and the errors in the input data. A proof of uniqueness is provided by an interactive analysis of the sensitivity functions, which are also used for choosing optimum source/receiver locations. Finally, software has been developed for a desktop computer and applied to interpreting specific real VSP observations as well as explaining the results of physical modelling for a 3-D crack model with the estimation of crack parameters.
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    Petrofabric Investigation of Gabbros from the Oman Ophiolite: Comparison between AMS and Rock Fabric (2000)
    Springer
    Marine geophysical researches 21 (2000), S. 289-306 
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    ISSN: 1573-0581
    Keywords: Magnetic susceptibility ; anisotropy ; petrofabric ; Oman Ophiolite ; gabbros
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The anisotropy of magnetic susceptibility was measured on 42 gabbros sampled across a complete plutonic sequence from the Oman ophiolite. The rock fabrics, investigated in the field and through plagioclase crystallographic fabric measurements, were compared to the magnetic fabrics. This comparative study reveals that from the paleo-Moho to the top of the foliated gabbros level, 73% of the rocks display a good correspondence in orientation, between the magnetic and rock fabric orientation. In these rocks, the AMS is controlled by secondary magnetites located in the fracture network of the olivines, and probably, but to a lesser extent, by secondary magnetites located in the exsolution lamellae of the clinopyroxenes. The high correlation between the AMS ellipsoid orientation and the rock fabric orientation is explained by the fact that the magnetic foliation is essentially constrained by the orientation of the olivine fracture planes, which is in turn constrained by the orientation of the overall magmatic rock fabric. In contrast to the primary mineral phases, the orientation of magnetite crystals in these gabbros is not due to their alignment in a flowing magma, so their preferred orientation, although usually mimicking that of the rock fabric, does have not the same origin. Furthermore, given that the preferred orientation of the anisometric secondary magnetites is much less perfect than the preferred orientation of the plagioclases, no correlation between the shape and magnitude of the AMS and plagioclase fabrics can be established. In the uppermost levels of the sequence there is no correspondence between the magnetic and rock fabric orientation. The magnetism of these rocks is mainly carried by primary magnetite and ilmenite grains. These minerals occur as small and scattered interstitial grains that exhibit neither alignment nor parallelism with the pre-existing rock fabric. Hence, the anisotropy, shape and orientation of the AMS ellipsoid are independent of the rock fabric ellipsoid. Although in the Wadi Al Abyad gabbros, just like in other magnetite bearing rocks (Rochette et al., 1992; Archanjo et al., 1995), the AMS cannot be used to evaluate the shape and strength of the finite strain ellipsoid, it can be reliably used to get the orientation of the rock fabric ellipsoid when the AMS is controlled by secondary magnetites.
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    Investigation of electrical anisotropy in the deep borehole KTB (1995)
    Springer
    Surveys in geophysics 16 (1995), S. 37-46 
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    ISSN: 1573-0956
    Keywords: resistivity ; anisotropy ; deep borehole ; KTB ; ARI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Information about electrical anisotropy in and around the deep borehole of the German Continental Deep Drilling Program (KTB) has been acquired using three different methods: (1) Under surface temperature and pressure conditions, the azimuthal dependence of resistivity has been measured in horizontal planes perpendicular to the axes of drill cores. (2) Simulated in-situ conditions (high temperature and pressure) have been applied to mini cores drilled at different orientations to structural features such as foliation. The resistivity was then measured in the direction of the mini cores' long axes. (3) Under quasi-in-situ (downhole) conditions, the azimuthal dependence of resistivity has been measured in horizontal planes using the Azimuthal Resistivity Imager (ARI), a down hole logging tool. These investigations have shown that electrical anisotropy is strongly related to structural features. The anisotropy of gneisses is the highest due to the strong foliation (averaged anisotropy factor 2.8). Lamprophyres are most isotropic (factor 1.2). Most rocks from KTB are amphibolites with intermediate anisotropies (factor 1.3). The anisotropies measured under surface temperature and pressure conditions and quasi-in-situ conditions on amphibolites are approximately the same, whereas anisotropies under simulated in-situ conditions are partially higher. Furthermore, the anisotropies measured on the cm to m scale using the various methods outlined above shall be compared with large scale anisotropies of the km scale measured around KTB using Magneto Tellurics.
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    Anisotropy and Superconductivity in the DMET-TSeF System (1999)
    Springer
    Journal of superconductivity 12 (1999), S. 531-534 
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    ISSN: 1572-9605
    Keywords: Organic superconductor ; superconductivity ; anisotropy ; Fermi surface
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The electronic states have been studied in the quasi-one-dimensional DMET-TSeF system, which includes several superconductors and nonsuperconductors. The origin of the different ground states has been examined by using the tight-binding band calculation. The type of the superconductivity has been discussed, considering the electronic wave functions that constitute the Fermi surface.
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    Investigation of the Off-Diagonal Thermoelectric Effect on Textured YBa2Cu3O7−δ (1998)
    Springer
    Journal of superconductivity 11 (1998), S. 203-207 
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    ISSN: 1572-9605
    Keywords: Thermoelectricity ; high-T c texture superconductor ; anisotropy ; oxygen content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Both the off-diagonal Seebeck effect and the off-diagonal Peltier effect were investigated on the same textured sample YBa2Cu3O7−δ and with the use of the same experimental setup. The effectiveness of several kinds of heat-conductive media was studied for the measurement. The flatness of both the sample and the heat-conducting block, and the matching between them were found very important for the reduction of the heat resistance of the interfaces. A reasonable agreement was found between the off-diagonal Seebeck coefficient measured by the off-diagonal Seebeck effect and that by the off-diagonal Peltier effect. The steplike feature in the relation between the off-diagonal Seebeck coefficient and the annealing temperature may imply a nonmonotonous change of the Seebeck coefficient along the c axis (S c) with oxygen content.
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    Scaling of a Slope: The Erosion of Tilted Landscapes (1998)
    Springer
    Journal of statistical physics 93 (1998), S. 477-500 
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    ISSN: 1572-9613
    Keywords: Erosion ; anisotropy ; stochastic equation ; renormalization group
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We formulate a stochastic equation to model the erosion of a surface with fixed inclination. Because the inclination imposes a preferred direction for material transport, the problem is intrinsically anisotropic. At zeroth order, the anisotropy manifests itself in a linear equation that predicts that the prefactor of the surface height–height correlations depends on direction. The first higher order nonlinear contribution from the anisotropy is studied by applying the dynamic renormalization group. Assuming an inhomogeneous distribution of soil substrate that is modeled by a source of static noise, we estimate the scaling exponents at first order in an ε-expansion. These exponents also depend on direction. We compare these predictions with empirical measurements made from real landscapes and find good agreement. We propose that our anisotropic theory applies principally to small scales and that a previously proposed isotropic theory applies principally to larger scales. Lastly, by considering our model as a transport equation for a driven diffusive system, we construct scaling arguments for the size distribution of erosion “events” or “avalanches.” We derive a relationship between the exponents characterizing the surface anisotropy and the avalanche size distribution, and indicate how this result may be used to interpret previous findings of power-law size distributions in real submarine avalanches.
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    Phase Transitions in a Driven Lattice Gas with Anisotropic Interactions (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 981-996 
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    ISSN: 1572-9613
    Keywords: nonequilibrium ; driven diffusive systems ; lattice gas ; kinetic Ising model ; anisotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Ising lattice gas, with its well known equilibrium properties, displays a number of surprising phenomena when driven into nonequilibrium steady states. We study such a model with anisotropic interparticle interactions (J ||≠J ⊥), using both Monte Carlo simulations and high temperature series techniques. Under saturation drive, the shift in the transition temperature can be both positive and negative, depending on the ratio J ||/J ⊥! For finite drives, both first- and second-order transitions are observed. Some aspects of the phase diagram can be predicted by investigating the two-point correlation function at the first nontrivial order of a high-temperature series expansion.
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    Anisotropy of Interfaces in an Ordered HCP Binary Alloy (1999)
    Springer
    Journal of statistical physics 95 (1999), S. 1337-1360 
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    ISSN: 1572-9613
    Keywords: diffuse interfaces ; hexagonal close packing ; anisotropy ; mean-field theory ; Allen–Cahn equation ; interphase boundaries ; antiphase boundaries ; surface energy ; discrete free energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A multiple-order-parameter mean-field theory of ordering on a binary hexagonal- close-packed (HCP) crystal structure is developed, and adapted to provide a continuum formulation that incorporates the underlying symmetries of the HCP crystal in both the bulk and gradient energy terms of the free energy. The work is an extension of the previous treatment by Braun et al. [Phil. Trans. Roy. Soc. Lond. A 355:1787 (1997)] of order–disorder transitions on a face-centered-cubic crystal (FCC) lattice. The theory is used to compute the orientation dependence of the structure and energy of interphase and antiphase boundaries in ordering to the Cd3Mg and CdMg structures, which are the HCP analogs of Cu3Au and CuAu structures in FCC. As in the corresponding FCC case, the multiple order parameters do not form a vector. Anisotropy is a natural consequence of the underlying crystal symmetries and the multiple-order-parameter continuum formation presented here. The isotropy transverse to the sixfold axis expected for a scalar order parameter is not found.
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    Low-temperature (T〈180 K) relaxation processes and possible “electronic phase separation” in RBa2Cu3O6+x (R=Y, Tm, Lu) single crystals (1996)
    Springer
    JETP letters 63 (1996), S. 830-834 
    Details
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 74.72.Jt ; 64.75.+g ; 77.22.Gm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Low-temperature (120–180 K) relaxational effects are observed in oxygen-deficient RBa2Cu3O6+x (R=Y, Tm, Lu) single crystals. Isothermal holding of the crystals after rapid cooling increases their resistance. The characteristic times and the activation energy of the relaxation process, E a ≈0.46 eV, are determined. The possible relation between the observed effects and the appearance of “electronic phase separation” is discussed.
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    Shape of the Cu(2) NQR spectra in YBa2Cu3O7, TmBa2Cu3O7 and TmBa2Cu4O8 (1997)
    Springer
    JETP letters 66 (1997), S. 624-629 
    Details
    ISSN: 1090-6487
    Keywords: 76.60.Gv ; 74.72.Bk ; 74.72.Yg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a study of shape of the Cu(2) NQR spectra in YBa2Cu3O7, TmBa2Cum3O7, and TmBa2Cu4O8 compounds at temperatures of 4.2–300 K. The results of the quantitative analysis lead us to conclude that the shape of the Cu(2) NQR spectra in all the samples studied can be described in the framework of the “motional narrowing” model, which implies that the Cu(2) nucleus possesses two different NQR frequencies between which it can rapidly jump. The difference in frequencies seems to be related to the charge-stripe correlations in CuO2 planes resulting in a dynamical modulation of the electric field gradients at the Cu(2) nuclei.
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    Linear low-temperature dependence of the surface impedance of a Ba0.6K0.4BiO3 single crystal (1996)
    Springer
    JETP letters 64 (1996), S. 832-838 
    Details
    ISSN: 1090-6487
    Keywords: 84.37.+q ; 74.72.Yg ; 74.72.Bk ; 74.72.Hs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The temperature dependences of the real part R s and the imaginary part X s of the surface impedance Z s =R s +iX s of the superconductor Ba0.6K0.4BiO3 (T c ≃30 K) are measured at a frequency of 9.4 GHz. Its temperature dependence Z s (T) and that of the complex conductivity σ s (T) can be described on the basis of a two-fluid model under two assumptions: The density of superconducting carriers increases linearly, and the relaxation time increases as a power law (∝1/T 5), with decreasing temperature T〈T c . This model also describes well the curves Z s (T) and σs (T) recently measured for YBa2Cu3O6.95 and Bi2Sr2CaCu2O8 single crystals.
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    Anisotropy of the superconducting properties of YBa2Cu3O7−x single crystals with reduced oxygen content (1998)
    Springer
    JETP letters 68 (1998), S. 332-337 
    Details
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 74.25.Fy ; 74.62.Bf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In an investigation of the resistivity anisotropy of YBa2Cu3O7−x single crystals with suboptimal oxygen content it is observed that the superconducting transition for the component ρc of the resistivity tensor is shifted to lower temperatures with respect to the transition for the component ρab. A similar shift is also observed for the transition in the temperature dependence of the dynamic magnetic susceptibility.
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    Subharmonic Shapiro steps and noise in high-T c superconductor Josephson junctions (1998)
    Springer
    JETP letters 68 (1998), S. 454-459 
    Details
    ISSN: 1090-6487
    Keywords: 74.50.+r ; 74.25.Fy ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An experimental investigation is made of the subharmonic Shapiro steps observed on the I-V curves of high-T c superconductor Josephson junctions and on the bias-voltage dependences of the rf noise and detector response when the junctions are subjected to external submillimeter radiation. Structures of this type are ordinarily described by a nonsinusoidal current-phase relation, which is why subharmonic steps appear. Numerical modeling of the processes occurring in a Josephson junction by means of a simple current-phase relation, as in the case of an SNS junction, gives good agreement with experiment. The width of the characteristic Josephson generation line of the junction was estimated on the basis of the noise dependences and the selective detector response. The width can be explained by taking into account the shot noise of the tunneling component of the conductivity. A model of the conductivity of a high-T c superconductor Josephson junction, consisting of a tunnel junction with microshorts possessing metallic conductivity, is discussed.
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    URL: http://dx.doi.org/10.1134/1.567889
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    A new optical method for measuring the electron-phonon interaction parameter λ〈Ω2〉 using the spectral dependence of the relaxation rate (1999)
    Springer
    JETP letters 70 (1999), S. 329-333 
    Details
    ISSN: 1090-6487
    Keywords: 78.47.+p ; 63.20.Kr ; 74.25.Jb ; 74.25.Kc ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spectral dependence of the electron-phonon relaxation rate γe−ph(ℏω) in metals is studied in pump-supercontinuum-probe (PSCP) experiments with femtosecond time resolution. Investigation of this spectral dependence, which exhibits a substantial slowing of the relaxation rate γe−ph(ℏω) near the Fermi level E F , using the parametrization γe−ph(ℏω)∝λ〈Ω2〉 (ℏω−E F )2 makes it possible to determine directly the electron-phonon interaction parameter λ〈Ω2〉. The parameter λ〈Ω2〉 for YBa2Cu3O7−δ is analyzed using this method.
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    URL: http://dx.doi.org/10.1134/1.568175
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    Stripe motion in CuO2 planes of Y1−x Pr x Ba2Cu3O7 as observed from the Cu(2) quadrupole resonance (1997)
    Springer
    JETP letters 65 (1997), S. 821-827 
    Details
    ISSN: 1090-6487
    Keywords: 61.72.Hh ; 74.72.Bk ; 74.80.−g ; 76.60.Gv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The NQR spectra of copper in the compounds YBa2Cu3O7, TmBa2Cu3O7, and Y0.9Pr0.1Ba2Cu3O7 at temperatures of 4.2–200 K are investigated by a pulsed NQR technique at frequencies of 28–33 MHz. Quantitative analysis of the spectra shows that the shape of the “plane” Cu(2) spectra is well described by using a model of 1D correlations of the charge and spin distribution in the CuO2 planes (stripe correlations). In the undoped superconductors the charge-spin stripe structure moves fast in the CuO2 planes, but doping the YBa2Cu3O7 lattice with praseodymium slows this motion down.
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    URL: http://dx.doi.org/10.1134/1.567452
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    Nature of the microwave response of a YBaCuO Josephson junction on a bicrystalline substrate (1996)
    Springer
    JETP letters 64 (1996), S. 454-459 
    Details
    ISSN: 1090-6487
    Keywords: 74.60.+r ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The response of YBaCuO Josephson junctions on a bicrystalline substrate to the action of microwave radiation is found to contain, besides the Josephson response, a contribution associated with the tunneling of quasiparticles through channels formed by localized states in the region of the Josephson junction. It is shown that this contribution is associated with an increase in the conduction through these channels under the action of the radiation on the junction.
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    URL: http://dx.doi.org/10.1134/1.567219
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  • 84
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    Anomalies of the electronic spin-lattice relaxation of Gd3+ in YBa2Cu4O8 and YBa2Cu3O6+x near 200 K (1999)
    Springer
    JETP letters 69 (1999), S. 610-615 
    Details
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 76.60.Es
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A sharp kink in the temperature dependence of the electronic spin-lattice relaxation rate near 200 K was found in the high-temperature superconductors YBa2Cu4O8 and YBa2Cu3O6+x . The effect is correlated with opening of a spin gap and microscopic phase separation.
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    URL: http://dx.doi.org/10.1134/1.567968
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    Characteristic features of the temperature dependence of the surface impedance of YBa2Cu3O6.95 single crystals (1997)
    Springer
    JETP letters 65 (1997), S. 938-944 
    Details
    ISSN: 1090-6487
    Keywords: 74.25.Nf ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The real and imaginary parts of the surface impedance Z s =R s +iX s of YBa2Cu3O6.95 single crystals are measured at a frequency ω/π=9.4 GHz. The quantities R s (T) and X s (T) are linear functions of temperature for T〈0.3T c (T c =93.5 K). A maximum of R s (T) and a plateau of X s (T) are observed in the interval 35〈T〈65 K. Our experimental data, just as all recent measurements of R s (T) in YBa2Cu3O6.95 single crystals in the temperature range 0〈T〈1.3T c , are described well in a two-fluid model which assumes electron-phonon scattering of quasiparticles.
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    URL: http://dx.doi.org/10.1134/1.567453
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    Anisotropy of normal resistivity in oxygen-deficient YBa2Cu3O7−x single crystals (2000)
    Springer
    JETP letters 72 (2000), S. 73-76 
    Details
    ISSN: 1090-6487
    Keywords: 74.25.Fy ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Temperature dependences of the resistivity tensor components ρab and ρc were measured for YBa2Cu3O7−x single crystals with different oxygen contents. The resistivity anisotropy ρc/ρab was found to grow exponentially with decreasing temperature. The results are compared with the predictions of different models describing transverse transport in the normal state of cuprate high-T c superconductors.
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    URL: http://dx.doi.org/10.1134/1.1312015
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  • 87
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    Spin susceptibility of neutron-irradiation-disordered YBa2Cu3O6.9 in the normal and superconducting states (1998)
    Springer
    JETP letters 67 (1998), S. 182-188 
    Details
    ISSN: 1090-6487
    Keywords: 61.80.Hg ; 76.60.Es ; 74.72.Bk ; 74.25.Nf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spin-spin relaxation rate 63 T 2 −1 of 63Cu nuclei in CuO2 layers is measured in the normal and superconducting states of the compound YBa2Cu3O6.9 (T c onset =94 K) subjected to radiation-induced disordering by a fast-neutron flux Φ to T c onset =68 K (Φ=7×1018 cm−2) and T c onset 〈4 K (Φ=12×1018 cm−2). It is found that as the structural disorder increases, the contribution of the indirect spin-spin interaction 63 T 2G −1 , which is related to the value of the spin susceptibility at the boundary of the Brillouin zone of the copper planes χs(q={π/a; π/a}), decreases slightly at the transition to the superconducting state for the initial sample and remains unchanged for the weakly disordered sample. This behavior of the short-wavelength contribution to the spin susceptibility attests to the stability of the x 2−y 2 symmetry of the energy gap against structural disorder, in accordance with proposed theoretical models of Cooper pairing for high-T c cuprates.
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    Antiferromagnetism in hydrated 123 compounds (1999)
    Springer
    JETP letters 69 (1999), S. 792-797 
    Details
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 74.25.Ha ; 75.50.Gg ; 76.60.Gv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Copper nuclear quadrupole resonance and zero-field nuclear magnetic resonance (ZFNMR) studies of YBa2Cu3O6.5 show that a magnetic phase appears in underdoped 123 superconductors treated in ambient moist air. The studies give convincing evidence that the “empty” CuO chains play the role of easy water insertion channels. The reaction occurs first in ordered regions of the crystallites. The final product of the reaction is a nonsuperconducting antiferromagnetic compound characterized by at least two types of magnetically ordered copper ions, with ZFNMR spectra in the frequency ranges 46–96 and 96–135 MHz, respectively. Even for powder samples fixed in an epoxy resin, this reaction is found to have partially occurred after a few years.
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    Effect of asymmetry of CuO2 layers in copper oxides on the anomalous neutron scattering near T c (1999)
    Springer
    JETP letters 69 (1999), S. 392-397 
    Details
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 61.12.Ex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Reasons for critical magnetic scattering of neutrons near T c in copper oxides with CuO2 layers whose nearest environment has no “up-down” symmetry are discussed. The intracrystalline electric field, which threads the CuO2 planes on account of the asymmetry, induces coupling between the spin and momentum of the current carriers. This coupling is shown to result in a manifestation of virtual Cooper pairs in the imaginary part of the spin susceptibility. Thus spin density fluctuations as well as current fluctuations should participate in the scattering. A way of experimentally distinguishing between the two mechanisms is pointed out.
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    URL: http://dx.doi.org/10.1134/1.568040
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    Anomalous behavior of the structural parameters of YBa2Cu4O8 single crystals at the transition to the superconducting state (1997)
    Springer
    JETP letters 66 (1997), S. 534-539 
    Details
    ISSN: 1090-6487
    Keywords: 61.50.Ks ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High-precision x-ray crystallographic studies of YBa2Cu4O8 single crystals (T c =70 K) are performed at eight temperatures in the interval 20–295 K. It is found that a number of structural parameters exhibit anomalous behavior near the superconducting transition of the crystal. A characteristic effect near the phase transition is the displacement of the O1 bridge atom that joins the Cu1 atom of the cuprate chain to the Cu2 atom of the cuprate plane. The shift of this oxygen toward the Cu2 atom is indicative of a change in the Cu2-O1 chemical bond and of charge transfer to the cuprate plane in the process of the transition of the crystal to the superconducting state.
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    URL: http://dx.doi.org/10.1134/1.567560
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    Theory of the pseudogap in the elementary excitation spectrum of the normal phase of bilayer cuprates (1997)
    Springer
    JETP letters 66 (1997), S. 569-574 
    Details
    ISSN: 1090-6487
    Keywords: 74.25.Jb ; 74.25.Gz ; 74.72.Bk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Solutions of the integral equations for the pseudogap in the elementary excitation spectrum of current carriers in bilayer cuprates are found. In the general case, the pseudogap possesses s + id symmetry, where the s component is determined by the interaction of holes via the phonon field and the d component is due to the superexchange interaction of the copper spins and the Coulomb-repulsion screened holes. The s and d components exhibit different temperature dependences. This fact enabled us to explain the characteristic features of the temperature behavior of the normal-phase spin susceptibility of lightly doped cuprates, specifically, for the compound YBa2Cu4O8 in the entire temperature interval T〉T c . The wave-number dependence of the pseudogap agrees with the photoemission data for Bi2Sr2CaCu2O8+y .
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    URL: http://dx.doi.org/10.1134/1.567547
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    Comparative studies of the NMR of thulium in Tm123 and Tm124 compounds: Evidence for structural and electronic phase separation (1996)
    Springer
    JETP letters 64 (1996), S. 398-403 
    Details
    ISSN: 1090-6487
    Keywords: 61.72.Hh ; 74.72.Bk ; 74.80.Bj ; 76.60.Lz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The nuclear magnetic relaxation of 169Tm in TmBa2Cu3O6+x (x=0.1–1.0, Δ x=0.1) and TmBa2Cu4O8 is studied at temperatures below 5 K. In all the samples, the Tm spin-lattice relaxation proceeds via intrinsic paramagnetic centers (PCs) like Cu2+ or copper-oxygen spin-polarized clusters. The experimental data for TmBa2Cu3O6+x support the idea of the structural (chemical) micro-phase separation in oxygen-deficient 123 compounds. Apparently, the samples with x⩾0.4 contain hole-poor nonsuperconducting regions, enriched with PCs, and hole-rich (PC-poor) superconducting regions. The volume fraction f n of the PC-rich phase reaches a maximum value of 0.85 at x=0.4 and decreases monotonically with increasing x (f n=0.5, 0.3, and 0.25 at x=0.5, 0.6, and 0.7, respectively). The Tm spin-lattice relaxation in the underdoped TmBa2Cu4O8 compound indicates that this sample, in contrast to oxygen-deficient TmBa2Cu3O6+x , has a homogeneous composition. However, the Tm spin-spin relaxation measurements reveal two sorts of the Tm nuclear spins in Tm124, having different NMR spectra and different relaxation times T 2. The latter result is evidence of electronic phase separation in CuO2 phases.
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    Commensurability oscillations and a new phase transition in YBa2Cu3Oy single crystals (1999)
    Springer
    JETP letters 69 (1999), S. 881-886 
    Details
    ISSN: 1090-6487
    Keywords: 74.72.Bk ; 75.60.Ej ; 74.25.Ha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Magnetization oscillations due to the commensurability of the vortex and crystal lattice periods in YBa2Cu3Oy (y=6.97±0.02) single crystals are investigated using a high angular resolution magnetometer. A sharp peak in the temperature dependence of the oscillation amplitude as well as other features in the behavior of the oscillation amplitude and of the irreversible magnetization are observed at T f ∼60 K. It is inferred that T f is the temperature of a transition of the solid vortex state to a smectic phase.
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    An infrared spectroscopic and single-crystal X-ray study of malayaite, CaSnSiO5 (1999)
    Springer
    Physics and chemistry of minerals 26 (1999), S. 546-553 
    Details
    ISSN: 1432-2021
    Keywords: Key words Malayaite ; Infrared spectroscopy ; Crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Powder infrared spectroscopy and X-ray diffraction techniques on single crystals were used to study the thermal behaviour of malayaite, CaSnSiO5. Infrared spectra show a discontinuity in the temperature evolution of phonon frequencies and absorbance near 500 K. However, crystal structure data collected at 300, 450, 550, 670, and 750 K show no evidence of a symmetry-breaking phase transition and no split positions. The most obvious change with heating is a tumbling motion of the SnO6 octahedra and an increase of the anisotropic displacement factors of Ca. The thermal evolution of the mean-square vibrational amplitude of the Ca atom shows a pronounced change in slope near 500 K. The evidence suggests that the 500 K anomaly in malayaite is more similar in character to the 825 K (β-γ) transition as opposed to the 496 K (α-β) transition in synthetic titanite.
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    Compression of witherite to 8 GPa and the crystal structure of BaCO3II (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 467-473 
    Details
    ISSN: 1432-2021
    Keywords: Key words Witherite ; High pressure ; Aragonite ; Crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Natural witherite (Ba0.99Sr0.01CO3) has been studied by single-crystal X-ray diffraction in the diamond anvil cell at eight pressures up to 8 GPa. At ambient pressure, cell dimensions are a = 5.3164(12) Å, b = 8.8921(19) Å, c = 6.4279(16) Å, and the structure was refined in space group Pmcn to R(F) = 0.020 from 2972 intensity data. The unit cell and atom position parameters for the orthorhombic cell were refined at pressures of 1.2, 2.0, 2.9, 3.9, 4.6, 5.5, 6.2, and 7.0 GPa. The volume-pressure data are used to calculate equation of state parameters K T0 = 50.4(12) GPa and K′ = 1.9(4). At approximately 7.2 GPa, a first-order transformation to space group P3¯1c was observed. Cell dimensions of the high-pressure phase at 7.2 GPa are a = 5.258(6) Å, c = 5.64(1) Å. The high pressure structure was determined and refined to R(F) = 0.06 using 83 intensity data, of which 15 were unique. This high-pressure phase appears to be more compressible than the orthorhombic phase with an estimated initial bulk modulus (K 7.2GPa) of 10 GPa.
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    Structure of Cu-bearing orthopyroxene, Mg(Cu.56,Mg.44)Si2O6, and behavior of Cu2+ in the orthopyroxene structure (1997)
    Springer
    Physics and chemistry of minerals 24 (1997), S. 463-476 
    Details
    ISSN: 1432-2021
    Keywords: Key words Cu2+-beearing orthopyroxene ; Orthopyroxene ; Crystal structure ; Jahn-Teller effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract  Cu-bearing pyroxene, Mg(Cu.56,Mg.44)Si2O6, has been synthesized by a flux method and crystal structure refinement has been performed by single crystal X-ray diffraction. It is found that the crystal structure is orthorhombic (space group Pbca) with unit cell dimensions of a=18.221(4), b=8.890(1), c=5.2260(7)Å and the cell volume of 846.5( )3Å3. In the M2-site one of the M-O bonds(M-O3B) is extremely expanded from 2.444(2) in enstatite to 2.732(2), thus the coordination polyhedron around M2-site is regarded as square pyramidal rather than square planar or octahedral. It is also found that the M1-site in the pyroxene structure is occupied almost exclusively by Mg, while the M2-site is almost evenly occupied by Mg and Cu. The observed extreme site preference shown by Cu2+ is unusual among the divalent cations with similar ionic sizes.
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    Pigment-protein interactions in Rhodobacter sphaeroides Y photochemical reaction center; comparison with other reaction center structures (1996)
    Springer
    European biophysics journal 24 (1996), S. 233-242 
    Details
    ISSN: 1432-1017
    Keywords: Bacterial reaction center ; Crystal structure ; Cofactor interactions ; Structure comparison ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Structural characteristics of pigments and cofactors are analyzed in the X-ray structure of the Rhodobacter sphaeroides (Y strain) photochemical reaction center, recently refined at 3 Å resolution (Arnoux B, Gaucher JF, Ducruix A and Reiss-Husson F (1995) Acta Cryst D51: 368–379). As several structures are now available for these pigment-protein complexes from various Rhodobacter sphaeroides strains and for Rhodopseudomonas viridis, a detailed comparison was done for highlighting converging structural results as well as for pointing to incidental differences. Comparison of mean plane orientations and distances, and also direct superposition of the pigment arrays, indicated that the best agreement between all the structures concerned the dimer and the bacteriopheophytin of the A branch. In the Y reaction center structure the pentacoordination of the Mg++ atoms of the bacteriochlorophylls, and the H bonding pattern of the porphyrin conjugated carbonyls are consistent with the better resolved Rhodobacter sphaeroides recently published structure (Ermler U, Fritzsch G, Buchanan SK and Michel H (1995) Structure 2:925–936). Discrepancies between the various Rhodobacter sphaeroides structures are larger for the quinones, particularly the secondary one. In the Y reaction center structure the phytyl and isoprenoid chains of the cofactors are defined and their local mobility was evaluated by analyzing the temperature factor and the density of neighbouring atoms. Significant differences were observed between the A and B branches, and, within each branch, from the dimer to the quinone molecules.
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    Computationally Efficient SH-Wave Modeling in Transversely Isotropic Media (2000)
    Springer
    Journal of nondestructive evaluation 19 (2000), S. 43-54 
    Details
    ISSN: 1573-4862
    Keywords: Ultrasonic testing ; modeling ; anisotropy ; shear horizontal wave ; field profile ; electromagnetic acoustic transducer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract Based on the description of shear horizontal (SH) wave propagation in arbitrarily oriented transversely isotropic media, radiation characteristics of ultrasonic transducers for this wave type are determined. The radiated wavefields are obtained by point source superposition, making use of an analytical relationship for the wave propagation direction as a function of the spatial coordinates. Approximate formulae are given for the radiation characteristics of circular and rectangular transducers in the far-field, which are in a form similar to the isotropic material case. Focusing on transversely isotropic weld metal specimens and unidirectional composites, numerical evaluation is performed for normal-incidence probes as well as for electromagnetic acoustic transducers.
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    URL: http://dx.doi.org/10.1023/A:1006645224237
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    Fluorescence of horse liver alcohol dehydrogenase using one- and two-photon excitation (1996)
    Springer
    Journal of fluorescence 6 (1996), S. 51-59 
    Details
    ISSN: 1573-4994
    Keywords: Fluorescence ; anisotropy ; one-photon excitation ; two-photon excitation ; anisotropy spectra ; horse liver alcohol dehydrogenase ; time-resolved fluorescence ; proteins ; tryptophan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examined the steady-state and time-resolved emission of liver alcohol dehydrogenase resulting from one-photon and two-photon excitation. Previous studies with one-photon excitation revealed that the two nonidentical tryptophan residues display different emission spectra and decay times. The use of two-photon excitation resulted in similar emission spectra, multiexponential intensity decays, time-resolved emission spectra, and anisotropy decays as was observed for one-photon excitation. These results suggest that both nonidentical tryptophan residues are excited to a similar extent for one- and two-photon excitation. However, the limiting anisotropy (r 0) with two-photon excitation from 585 to 610 nm is below 0.1 and appears distinct from that observed previously forN-acetyl-l-tryptophanamide.
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    URL: http://dx.doi.org/10.1007/BF00726726
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    Displacive phase transitions in C-centred clinopyroxenes: spodumene, LiScSi2O6 and ZnSiO3 (2000)
    Springer
    Physics and chemistry of minerals 27 (2000), S. 719-731 
    Details
    ISSN: 1432-2021
    Keywords: Key words Clinopyroxene ; Spodumene ; ZnSiO3 ; LiScSi2O6 ; Phase transition ; High-pressure ; Crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract The clinopyroxenes spodumene (LiAlSi2O6), LiScSi2O6 and ZnSiO3, all with space group C2/c at ambient conditions, were studied under high pressures by single-crystal X-ray diffraction in a diamond-anvil cell. Changes in the evolution of the unit-cell parameters, optical properties and the appearance of h + k odd reflections characteristic of a primitive lattice, indicate that all three pyroxenes undergo phase transitions. The transitions are mostly displacive in character, and are non-quenchable. Transition pressures are 3.19 GPa in spodumene, ∼0.6 GPa in LiScSi2O6 and 1.92 GPa in ZnSiO3. The space group of all three high-pressure phases was determined to be P21/c by structure refinement to single-crystal X-ray intensity data collected in the DAC. In the ZnSiO3 clinopyroxene the intermediate P21/c phase further transforms to a second C2/c phase (HP-C2/c) at 4.9 GPa (confirmed by structure refinement). The volume change at this transition is about 2.6%, three times larger than in the first phase transition, and typical of the P21/c→ HP-C2/c phase transitions found previously in MgSiO3, FeSiO3, etc. These results therefore provide the first direct evidence that the HP-C2/c and the HT-C2/c structures of pyroxenes are distinct polymorphs with the same space group. The phase transition from C2/c to P21/c symmetry in spodumene and LiScSi2O6 therefore occurs because the polymorphs stable at ambient conditions are isotypic to the high-temperature C2/c phases of clinopyroxenes such as pigeonite and clinoenstatite.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002690000116
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