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  • Articles  (228)
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  • Springer  (228)
  • 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
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    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
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    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)
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    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)
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    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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    Coherence and correlation in laser excitation of semiconductor quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1315-1322 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Time resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The concept of coherence due to optical excitation of an ensemble of two-level atoms is relatively simple and well established. For the laser-excited electron-hole pairs or excitions in a semiconductor, the Pauli exclusion and the Coulomb interaction lead to the necessary evolution of the theory of coherence to incorporate the spin degree of freedom, the filling of phase space, the excitons and particularly, their correlation. We have developed two theoretical approaches: one using the Feynman diagrams and one in terms of a force-force correlation function. The former gives us a pictorial way to describe the optical processes and the latter gives us a prescription for computation beyond the perturbative approach. In this paper, we will attempt to use simple physical pictures based on our theory to describe the time development of the coherence, the role of correlation, the dependence on the polarization of light, and the nonlinear time-resolved optical experiments which measure the coherence.
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    Exciton dynamics in ZnSe/ZnS x Se1−x superlattices (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1429-1433 
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    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Localised single-particle electronic states (excluding impurities) ; Photoluminescence ; II–VI semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Time-resolved photoluminescence experiments in a wide carrier density range up to and beyond the threshold for stimulated emission in ZnSe/ZnS x Se1−x superlattices are presented. Different localisation mechanisms of free excitons are identified giving rise to different radiative recombination channels. At high carrier density localised energy states merge into miniband that allows for exciton-exciton interaction, such as screening of the free-exciton absorption and inelastic exciton-exciton scattering.
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    Size-dependent electron-hole exchange interaction in CdSe quantum dots (1995)
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    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1407-1412 
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    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Surface and interface electron states ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have investigated the fine structure of luminecence of CdSe nanocrystals observed with size-selective excitation. We show that the luminescence line closest to the laser arises from the recombination of the optically forbidden A-exciton. Radiative recombination occurs via a phonon-assisted virtual transition to theB-exciton state. The electron-hole exchange energy obtained from the experimental results strongly increases with decreasing nanocrystal size as expected from the increasing overlap of the electron and hole wave functions. The size dependence is in good agreement with the theoretical predictions.
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    Exciton states in In x Ga1−x As/GaAs double quantum wells: Normalized reflection spectra (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1423-1427 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Surface and interface electron states ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Normalized reflection spectra in GaInAs/GaAs quantum wells are shown for two sets of samples with different alloy concentration (x=9% and 18.5%) and well thickness ranging from 1.5 nm to 25 nm. All samples were grown on (001) GaAs surface by Molecular Beam Epitaxy and characterized by RHEED and X-ray reflection diffraction. Exciton envelope function in effective mass approximation and optical response in polaritonic schema are computed. Normalized reflection spectroscopy has shown itself to be a well suited technique in order to study structural and electronic properties of confined quantum structures.
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    URL: http://dx.doi.org/10.1007/BF02457221
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    Two-dimensional wannier excitons. Effects of a random adiabatic potential (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1447-1452 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Optical properties of thin films, surfaces, and layer structures (superlattices, heterojunctions, and multilayers) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We investigate the absorption spectrum and the distribution of radiative decay times for two-dimensional excitons in semiconductor quantum wells, as affected by an adiabatic white-noise random potential. Such a potential could result from atomic-scale fluctuations in the composition of an alloy semiconductor, or in quantum well thickness. We find in general that the shortest radiative decay time is directly proportional to the inhomogeneous width of the exciton line in absorption, itself proportional to the correlation parameter for the random potential.
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    URL: http://dx.doi.org/10.1007/BF02457225
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    Experimental evidence of the exciton centre-of-mass quantization in Zn1−x Cd x Se/ZnSe multiple quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1473-1479 
    Details
    ISSN: 0392-6737
    Keywords: Surface and interface electron states ; Excitons and related phenomena (including electron-hole drops) ; Polaritons (including photon-phonon and photon-magnon interactions) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report the evidence of exciton-polariton centre-of-mass quantization in II–VI quantum wells consisting of ternary alloy. Absorption and photoluminescence studies on Zn0.89Cd0.11Se/ZnSe quantum wells, covering the intermediate region between two- and three-dimensional exciton behaviour, exhibit distinct optical resonances in the high-energy tail of the free-exciton structure. We reproduce the well width dependence of the centre-of-mass states by modeling the optical response of the QWs with a thin-slab variational wave function, which takes into account non-adiabatic terms.
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    URL: http://dx.doi.org/10.1007/BF02457229
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    Interparticle interaction in spin-aligned and spin-degenerate exciton systems in II–VI quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1543-1547 
    Details
    ISSN: 0392-6737
    Keywords: Studies of specific magnetic materials ; Optical properties of thin films surfaces and layer structures (superlattices, heterojunctions and multilayers) ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Two qualitatively different e-h systems have been investigated in undoped CdTe/Cd0.88Mn0.12Te and Cd0.97Mn0.03 Te/Cd0.75Mn0.25 Te QWs at 2 K and magnetic fields up to 14 T, namely a strongly spin-depolarized system in the CdTe QW and a highly spin-polarized one in the Cd0.97Mn0.03 Te QW. The interaction of the spin-aligned excitons is repulsive. In contrast, in the spectra of a dense spin-depolarized excitonic system an additional well pronounced emission lineM was observed at approximately 5 meV below the excitonic line. This line is assigned to the emission of molecules consisting of excitons with opposite spins of both electrons and holes.
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    URL: http://dx.doi.org/10.1007/BF02457241
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    Coherent dynamics of excitonic and biexcitonic wave packets in semiconductor superlattices (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1573-1578 
    Details
    ISSN: 0392-6737
    Keywords: Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report on the observation of an electric-field-induced electric-dipole moment of biexcitonic molecules in a GaAs/Al0.3Ga0.7As superlattice. The macroscopic oscillating electric field, associated with the microscopic wave packet dipole moments, is monitored by time-resolved transmittive electro-optic sampling. The field dependence of the biexcitonic binding energy is detected by transient four-wave mixing. From these experiments, an ultrafast non-resonant excitation mechanism of biexcitons is inferred.
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    URL: http://dx.doi.org/10.1007/BF02457246
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    Bipolariton in quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1255-1264 
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    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Polaritons (including photon-photon and photon-magnon interactions) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We develop the bipolariton concept for a quasi-2D excitonic molecule (m) in quantum wells (QWLs). The bipolariton wave equation, which includes both the exciton-exciton (x-x) attraction and thex-photon (γ) coupling, is analysed. In the 2D bipolariton model, a quasi-2Dm exists in QWLs mainly as two quasi-boundsurface polaritons and, consequently, decays mainly into two outgoing surface polaritons. In quasi-2D GaAs QWLs the polariton renormalizations give rise to a «Mexican hat» structure in them dispersion at small momenta together with a considerable increase of both them effective binding energy ɛ m and the inversem radiative lifetimeГ m . A van Hove singularity in the joint density of polariton states is responsible for this effect.
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    URL: http://dx.doi.org/10.1007/BF02457197
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    Phonon-polariton interaction in a microcavity (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1657-1662 
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    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Polaritons (including photon-phonon and photon-magnon interactions) ; Dynamics of nonlinear optical systems ; optical instabilities, optical chaos, and optical spatio-temporal dynamics ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The linewidth of the microcavity exciton polariton is studied by onresonant and off-resonant photoluminescences. The two main contributions to the linewidth are caused by radiative loss and phonon scattering. The oscillator strength is found to be unmodified by the exciton-phonon coupling. Comparison is made between theory and experiment.
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    URL: http://dx.doi.org/10.1007/BF02457259
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    Fast exciton and free-carrier kinetics in semiconductors: a Monte Carlo simulation (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1717-1722 
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    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The coupled dynamics of free carriers and excitons after non-resonant excitation with short laser pulses is investigated by means of an Ensemble Monte Carlo method which includes phonon-assisted formation and dissociation of free excitons. Simulations for bulk GaAs reveal that excitonic binding under participation of LO phonons is a very fast and effective process. The temporal rise of exciton luminescence depends on the particular excitation conditions and is determined by all interaction mechanisms in the system.
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    URL: http://dx.doi.org/10.1007/BF02457269
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    Exciton-photon coupling in GaAs bulk microcavities (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1747-1751 
    Details
    ISSN: 0392-6737
    Keywords: Polaritons (including photon-phonon and photon-magnon interactions) ; Excitons and related phenomena (including electron-hole drops) ; Quantum optics ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A great interest in the study of exciton-photon coupling in resonant optical media such as semiconductor microcavities is currently developing both in experiments and in theory. We investigate the spectral response of a new semiconductor quantum system in which the cavity material itself is the active medium. If the Fabry-Perot quasi-mode is carefully tuned on the excitonic transition of the cavity bulk material, strong exciton-photon coupling takes place and produces new features such as a Rabi-like splitting as large as that observed in quantum well microcavities and comparable optical absorption. In addition, the polaritonic spatial dispersion and the quantization of the centre-of-mass motion introduce remarkable fine structures which are absent in the quantum well case. We demonstrate the above effects from a spectroscopic analysis of GaAs cavities, using standard reflectance and photoluminescence techniques. The experimental results are further clarified with theoretical calculations performed with an adapted transfer-matrix approach. The case of semi-cavities is finally considered and a new way to control the exciton-photon interaction in our system is achieved tailoring the photonic wave function with a change in the reflectivity phase of the mirrors.
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    URL: http://dx.doi.org/10.1007/BF02457274
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    Theory of resonant rayleigh scattering of excitons in semiconductor quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1801-1805 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Electron states in low-dimensional structures (including quantum wells ; superlattices ; layer structures ; and intercalation compounds ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Disorder-induced Rayleigh scattering of excitons in quantum wells is investigated theoretically. For classical excitions (long-range spatial correlation), the disorder average can be performed exactly. For the full problem, a kinetic equation with «weak memory» for the excition distribution is derived which coincides with the classical result in the appropriate limit. The theoretical results are compared with recent experimental data on femtosecond time-resolved luminescence explaining well the finite rise time and the heavy-light-hole beating.
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    URL: http://dx.doi.org/10.1007/BF02457284
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    Excitons in microcavities: Cavity polariton photoluminescence (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1323-1332 
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    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Polaritons (including photon-phonon and photon-magnon interactions) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We present an extensive set of absorption and PL measurements on semiconductor microcavities in the strong-coupling regime. We observe strong coupling from 110 K to room temperature. We look at the behaviour of the photoluminescence for different exciton-photon detuning. We discuss this data using two different pictures, the first is a non-interacting (uncoupled) picture of an exciton in a cavity filter. The second model is that of a cavity polariton and this explains the observed dynamics in the strong-coupling regime. We show how the opposing needs of strong coupling and high photoluminescence extraction efficiency can be reconciled.
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    URL: http://dx.doi.org/10.1007/BF02457204
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    Binding energies of excitons in ionic quantum well structures (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1343-1347 
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    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Polarons and electron-phonon interactions ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; III-V compounds and systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have calculated the binding energies of excitons in quantum well structures based on ionic semiconductors by including the electron-hole interactions with the longitudinal-optical-phonon field. We have taken into account these interactions by using different effective interaction potentials between the electron and the hole as derived by Haken, Aldrich and Bajaj, and Pollman and Buttner. We have calculated the binding energies of excitons in several ionic quantum well structures as functions of well width using these effective potentials following a variational approach. We find that the values of the exciton binding energies calculated using these potentials are always larger than those, obtained using a Coloumb potential screened by static dielectric constant.
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    URL: http://dx.doi.org/10.1007/BF02457207
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    Some new fundamental properties of GaN single-crystal films on SiC and sapphire substrates (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1509-1512 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; III-V Compounds and systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The reflectance spectra of GaN/6H-SiC, films and the absorption spectra of GaN/Al2O3 films were studied and several fundumental parameters of GaN-energy positions of exciton, resonances ω0, damping constants⩾s, longitudinal-transverse splittings ωLT and the oscillator, strengthsf of the exciton states were determined. A blue shift and broadening of the luminescence band were observed in the luminescence spectra of GaN quantum dots. The mean dot radius in the sample was estimated to be about 4.5nm.
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    URL: http://dx.doi.org/10.1007/BF02457235
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    Exciton dynamics within growth islands of GaAs/Al x Ga1−x As single quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1531-1536 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The localization dynamics of excitons within growth islands of GaAs/Al x Ga1−x As single quantum wells (SQW) have been investigated by time-resolved photoluminescence spectroscopy (TRPL). Several samples with different substrate misorientation and growth interruption times are compared with regard to the photoluminescence (PL) emission dynamics. For monolayer (ML) islands larger than the exciton radius,i.e. long growth interruption, the time evolution of the different PL peaks reflects the transfer of free excitons between growth islands as well as the localization within a single growth island. The samples with shorter growth interruption reveal a much less pronounced PL splitting due to ML islands. The dynamics appears to be mainly determined by exciton localization to thicker ML islands. The density of localization centres is larger for the sample grown on misoriented substrates.
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    URL: http://dx.doi.org/10.1007/BF02457239
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    Non-linear optics of hybrid excitons in organic-inorganic nanostructures (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1555-1559 
    Details
    ISSN: 0392-6737
    Keywords: Nonlinear optics ; Optical properties of thin films, surfaces, and thin layer structures (including superlattices, heterostructures, and intercalation compounds) ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary In a system comprising an organic layer coupled to a semiconductor layer, if the energy of the Frenkel exciton in the first is close to that of the Wannier exciton in the second, the lowest electronic excitations can be described as hybrid resonances. These new excitons give rise to very pronounced optical non-linearities because they have at the same time large oscillator strengths, typical of Frenkel excitons, and large radii, typical of Wannier excitons. The results of a microscopic calculation of the optical properties of such a system are presented and discussed: compared with the usual semiconductor quantum wells, enhancements of two orders of magnitude both in the size of the susceptibility (linear part) and in its relative change with increasing excitation density (Kerr non-linearity) are predicted.
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    URL: http://dx.doi.org/10.1007/BF02457243
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    Excitation energy dependence of the optical properties of InGaAs/GaAs quantum well heterostructures (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1383-1387 
    Details
    ISSN: 0392-6737
    Keywords: III–V semiconductors ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Excitons and related phenomena (including electron-hole drops) ; III–V compounds and systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report an experimental study on a large set of InGaAs/GaAs quantum well structures by means of continuous-wave photoluminescence and photoluminescence excitation. The luminescence spectrum at low temperature systematically exhibits a doublet structure whose lineshape is very sensitive to the excitation energy. Accordingly, the excitation spectra detected by monitoring the emission at the two different luminescence peaks have very different profiles, with peaks and/or dips which are not directly related to absorption resonances. As a matter of fact, the anomalies disappear when increasing the temperature or when using an optical bias with energy above the GaAs energy gap. In these cases, the excitation profiles recover the behaviour typical of 2D systems.
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    URL: http://dx.doi.org/10.1007/BF02457214
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    Exciton recombination mechanism and binding energies in MOCVD-grown Zn1−x Cd x Se−ZnSe single quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1585-1593 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Optical properties of thin films surfaces and layer structures (superlattices, heterojunctions and multilayers) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report here on the study of the optical properties of ZnCdSe−ZnSe quantum structures elaborated by metalorganic chemical vapour deposition (MOCVD). The band structure is experimentally investigated by means of photoluminescence and photoreflectance. We have computed the exciton binding energies for heavy- and light-hole excitons in the context of a self-consistent two-parameter trial function. As a complement, we study the temperature dependence of the photoluminescence intensity under both direct and indirect photoexcitation in graded-index separate confinement heterostructures based on these materials.
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    URL: http://dx.doi.org/10.1007/BF02457248
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    Double 2s-1s resonance in LO-phonon-assisted secondary emission of excitions in CdTe/(Cd, Mn) Te MQW structures (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1787-1790 
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    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; II–VI compounds and other chalcogenides ; II–VI semiconductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report on the observation of the doubly resonant secondary emission involving 2s and 1s exciton states. The resonance conditions have been realized in CdTe/Cd1-xMnx Te quantum well structures by magnetic-field tuning of the 2s-1s energy spacing to the LO-phonon energy. Theoretical analysis shows the doubly resonant process to be indirect, with hot 1s excitons acting as intermediate states. It is concluded that the resonance width of 2.6 meV gives the 2s-exciton homogeneous linewidth governed by elastic scattering into the hot 1s exciton states.
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    URL: http://dx.doi.org/10.1007/BF02457281
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    Dynamics of excitons tunnelling in II–VI asymmetric double quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1277-1284 
    Details
    ISSN: 0392-6737
    Keywords: II–IV semiconductors ; Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Steady-state and picosecond photoluminescence experiments on CdTe/CdZnTe and CdTe/CdMnTe asymmetric double quantum wells are presented. An external magnetic field is used to tune the coupling between the two QWs by allowing resonances to occur between excitonic states. Very efficient tunnelling is found when an exciton from the high-energy QW can transfer either with the emission of an LO phonon or via the resonance with the 2s state of the low-energy QW.
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    URL: http://dx.doi.org/10.1007/BF02457199
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    Exciton-exciton interaction in quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1339-1342 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Time resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Fast initial decays of both the luminescence intensity and the circular luminescence polarization at high exciton densities, under resonant excitation, are reported for the first time. These fast decays are simultaneously initiated by the increase of the ellipticity of the photogenerating picosecond laser beam. The theory of the mechanism illustrates the driving role of the interexciton exchange interaction.
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    URL: http://dx.doi.org/10.1007/BF02457206
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    Excitons in quantum well wires: V-shaped wire, T-shaped wire and strain-induced lateral confinement (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1389-1393 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Surface and interface electron states ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We calculated the energy and the wave function of the exciton for i) a V-shaped quantum wire, ii) a T-shaped quantum wire and iii) a quantum wire resulting from strain-induced lateral confinement. The full Luttinger and Bir-Pikus Hamiltonian are taken into account in the three calculations. We used different parameters inside the well and at the barrier. The basis states |3/2m〉 are defined with respect to [110], the direction of the wire in the three kinds of structures, instead of the usual [001] direction. The hole dispersion curve allows one to define an effective mass which is to be introduced in the variational calculation of the exciton binding energy. We show that the hole is confined in a wire only in case i).
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    URL: http://dx.doi.org/10.1007/BF02457215
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    Edge magneto-exitons (ring excitons) in antidots (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1413-1416 
    Details
    ISSN: 0392-6737
    Keywords: Excitons and related phenomena (including electron-hole drops) ; Surface and interface electron states ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary An opening (antidot) in two-dimensional (2D) electron gas placed in a strong perpendicular magnetic field makes it possible the formation of ring-shaped excitons stemming from the skipping-states of electrons and holes. The binding energy of the ground state of such excitons is logarithmically larger than that of the «bulk» 2D excitons. The possibility of tunnelling electron to hole (or vice versa) around the antidot results in a shift for each of the excitons levels that oscillates with the magnetic field.
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    URL: http://dx.doi.org/10.1007/BF02457219
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