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  • Articles  (150)
  • Crystal structure  (59)
  • hydrogen bonding  (34)
  • Nitrogen fixation  (32)
  • Denitrification  (29)
  • Springer  (150)
  • 1995-1999  (150)
  • Geosciences  (150)
  • 1
    ISSN: 1572-8854
    Keywords: Crystal engineering ; hydrogen bonding ; acetonitrile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We report details of the synthesis and X-ray crystal structures of two new cocrystals that are sustained by the tetrahedral hydrogen bond donor [Mn(CO)3(μ3-OH)]4. [Mn(CO)3(μ3-OH)]4· 2(2,3,5,6-tetramethylpyrazine)·2H2O·2MeCN,a=21.503(3),b=12.674(1),c=17.318(2), β=102.15(2), C2/c,D calc=1.46 mg/m3,Z=4,4188 observed reflns,R f=0.047,R w=0.040; 1.[Mn(CO)3(μ3-OH)]4·4,4′-dipyridyl·2MeCn,a=16.942(6),b=12.395(2),c=18.790(6), β=114.88(3), C 2/c,D calc=1.60 mg/m3,Z=4,2430 observed reflns,R f=0.043,R w=0.051;2. 1 crystallizes as a 2-D grid, whereas2 forms 1-D strands. The hydrogen bond patterns exhibited by1 and2 are analyzed in the context of our earlier studies involving [Mn(CO)3(μ3-OH)]4 and other relevant literature.
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  • 2
    ISSN: 1572-8854
    Keywords: Tautomerism ; hydrogen bonding ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystals consisting of two distinct chemical entities, tautomers of each other, in exact 1∶1 ratio, have been obtained and their structure determined by X-ray analysis. The crystals of C9H11N3·C9H11N3 are monoclinic,P21/c,a=15.674(3),b=17.085(3),c=13.758(3)Å, β=90.78(2)°,Z=8. There are two hydroxylamine and two aminonitrone molecules in the asymmetric unit. Hydrogen bonds connect those molecules into chiral layers. Layers of opposite chirality alternate andthe crystal is centrosymmetric as a whole. Within those layers chains of tautomers joined by very strong O−H... O and strong N−H... N bonds can be recognized. Proton transfer along those chains with simultaneous rearrangement of π-bonds within the molecules would result in interconversion of tautomers and would affect chirality of the layer.
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  • 3
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    Journal of chemical crystallography 25 (1995), S. 841-844 
    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.
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  • 4
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    Journal of chemical crystallography 25 (1995), S. 215-218 
    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.
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  • 5
    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.
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  • 6
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    Journal of chemical crystallography 25 (1995), S. 569-571 
    ISSN: 1572-8854
    Keywords: PyrrolenineN-oxide ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2-Amino-5,5′-di(β-cyanoethyl)-1,2-pyrrolenineN-oxide monohydrate, C10H14N4O·H2O, crystallizes from MeCN in space group P212121 witha=7.0007(5),b=8.2998(6),c=20.8418(13) Å,V=1211.0(2) Å3,Z=4. The structure was refined toR=0.034 andR w=0.044 for 2325 observed reflections. The pyrrolenine ring adopts a nearly planar conformation, with maximum deviation from planarity 0.089(2) Å. The N−O distance is 1.345(2) Å. The water molecule bridges two pyrrolenine molecules via hydrogen bonds to theirN-oxide oxygen atoms, and also accepts a hydrogen bond from the NH2 group of another pyrrolenine molecule.
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  • 7
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    Journal of chemical crystallography 25 (1995), S. 601-603 
    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.
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  • 8
    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.
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  • 9
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    Journal of chemical crystallography 26 (1996), S. 747-752 
    ISSN: 1572-8854
    Keywords: Phosphine oxide ; quaternary ammonium ; water-soluble phosphine ; crystal structure ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound crystallizes in the centrosymmetric triclinic space group $$P\bar 1$$ withZ=4. The crystallographic asymmetric unit contains two independent cations; interatomic distances within these include P=O=1.47(1) and 1.47(1) Å, P−C6H5=1.78(2)–1.81(1)Å and P−CH2CH2NMe3 +=1.80(1) and 1.81(1) Å. The phosphine oxide moiety is involved in intermolecular hydrogen bonding ()...H−C, with O...H≥2.42Å) and the iodide is involved in I...H−C contacts with I...H≥3.10Å.
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  • 10
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    Journal of chemical crystallography 26 (1996), S. 341-346 
    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.
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  • 11
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    Journal of chemical crystallography 26 (1996), S. 563-567 
    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.
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  • 12
    ISSN: 1572-8854
    Keywords: Structure ; thiosemicarbazide ; infrared ; nmr ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structures of three alkyl derivatives of thiosemicarbazide are described: anti,Z-4,4-dimethyl-3-thiosemicarbazide (1), syn,E,Z-2,4-dimethyl-3-thiosemicarbazide (2), and syn,E-1-cyclopentano-3-thiosemicarbazone (3). Crystal data: for 1: triclinic, P-1 (#2), a = 5.802(1)Å, b = 6.935(1)Å, c = 8.104(2)Å, α = 78.35(1)°, β = 82.13(1)°, γ = 70.71(1)°, and Z = 2; for 2: orthorhombic, Pbca (#61), a = 9.417(3)Å, b = 8.624(2)Å, c = 15.169(3)Å, and Z = 8; for 3: triclinic, P-1 (#2), a = 6.068(3)Å, b = 8.145(4)Å, c = 8.666(5)Å, α = 83.75(4)°, β = 86.16(5)°, γ = 74.07(4)°, and Z = 2. In general, molecules are linked by N–H···S hydrogen bonds with sulfurs accepting two or three hydrogen bonds. Structures 2 and 3, which adopt the syn conformation, form N–H···N intramolecular hydrogen bonds. The solid-state structures are consistent with their infrared and proton nuclear magnetic resonance spectra.
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  • 13
    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.
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  • 14
    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.
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  • 15
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    Journal of chemical crystallography 28 (1998), S. 831-834 
    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.
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  • 16
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    Journal of chemical crystallography 28 (1998), S. 867-870 
    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−.
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  • 17
    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.
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  • 18
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    Journal of chemical crystallography 28 (1998), S. 931-933 
    ISSN: 1572-8854
    Keywords: Flavone ; hydrate ; hydrogen bonding ; X-ray crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of 7-hydroxyflavone monohydrate, C14H10O3 · H2O, is determined. The compound crystallizes in the monoclinic space group, P21/n with a = 3.801(3), b = 19.665(4), c = 16. 039(6), β = 93.69(3)°, and μ = 0.68 mm−1 for Z = 4. The phenyl ring of the flavone moiety is rotated 18.6(1)° out of the penzopyran plane, which is a typical value for flavones. In the crystal lattice, there are wide channels which are lined mainly by C–H groups. The water molecules enclosed in these channels are severely disordered.
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  • 19
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    Journal of chemical crystallography 28 (1998), S. 111-117 
    ISSN: 1572-8854
    Keywords: Di-hydroxymalonic acid ; hydrogen bonding ; crystal engineering ; supramolecular chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An examination of the crystal structures of di-hydroxy malonic acid 1 (P21/na = 5.384(2), b = 6.268(2), c = 14.354(8) Å, β = 103.57(3)°) and N-ethylbenzylammonium di-hydroxy hydrogenmalonate 2 (P212121 a = 13.373(2), b = 15.342(4), c = 18.741(4) Å,) has highlighted the influence of directional O–H···O interactions in the assembly of hydroxy-substituted dicarboxylic acids. The complementarity of carboxylic and hydroxy groups in 1 creates a very dense 3-D structure (D c = 1.919 g cm−3) through four O–H···O hydrogen bonds. In 2, the anions form infinite, spiraling chains created by head-to-tail O–H···O hydrogen bonds. Neighbouring chains are crosslinked into a complex 3-D anionic network with channels parallel to a and b. The cations are positioned within these channels and held in place via two N–H···O interactions.
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  • 20
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    Journal of chemical crystallography 28 (1998), S. 145-147 
    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.
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  • 21
    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.
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  • 22
    ISSN: 1572-8854
    Keywords: Cyclohexane ; alkyne ; hydrogen bonding ; X-ray crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of the title compound, C18H28O3, is determined. The hydrogen bond scheme does not follow considerations based on hierarchies of donor and acceptor strengths. The hydroxyl group of the molecule accepts only very weak C–H···O interactions.
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  • 23
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    Journal of chemical crystallography 28 (1998), S. 251-258 
    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.
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  • 24
    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.
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  • 25
    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.
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  • 26
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    Journal of chemical crystallography 28 (1998), S. 239-241 
    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.
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  • 27
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    Journal of chemical crystallography 28 (1998), S. 297-301 
    ISSN: 1572-8854
    Keywords: Crown ether ; hydrogen bonding ; alkylation ; biphenyl ; diols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl, 3, is presented. This molecule crystallizes in the monoclinic space group P21/n (a = 9.440(2), b = 12.679(3), c = 11.679(3) Å β = 94.60(2)° V = 1382.5(5) Å3; Z = 4). One of the unique features of the X-ray structure of 3 is the intramolecular hydrogen bonding. The hydrogens of the phenolic and hydroxy groups occupies bridging positions via hydrogen bonding to an ether oxygen (O1) and a phenolic oxygen (O4), respectively. This hydrogen bonding does not affect the interplanar angle between phenyl rings (49.34°), which is in the range expected for ortho-disubstituted biphenyl compounds. The hydrogen bonding of this type explains why it is difficult to alkylate both phenoxy groups of 2,2′-biphenol with tetrahydropyranyl protected 2-(2′-chloroethoxy)ethanol.
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  • 28
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    Journal of chemical crystallography 28 (1998), S. 593-596 
    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.
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  • 29
    ISSN: 1572-8854
    Keywords: 2-Benzoyloxy-4-hydroxybenzaldehyde ; 2,4-dihydroxybenzaldehyde ; hydrogen bonding ; x-ray structure
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    Topics: Geosciences , Physics
    Notes: Abstract 2,4-Dihydroxybenzaldehyde can be acylated at the 2 position if the more reactive 4 position is first protected as the methylmethoxy ether. Deprotection permits isolation of 2-benzoyloxy-4-hydroxybenzaldehyde. 2,4-Dihydroxybenzaldehyde, C7H6O3, crystallizes in P21/c, with a = 7.3762(6), b = 11.7455(9), c = 7.3149(6) Å, β = 90.533(2)°, Z = 4, and D X = 1.448 g cm−3. The individual molecules are characterized by an intramolecular hydrogen bond. The molecules form sheets with additional intermolecular hydrogen bonds. 2-Benzoyloxy-4-hydroxybenzaldehyde, C14H10O2, crystallizes in Pca21, with a = 24.2629(14), b = 3.8445(2), c = 12.3727(8) Å, Z = 4, and D X = 1.394 g cm−3. The molecules consist of two planar halves twisted by 51.63(5)° about the ester linkage. Intermolecular hydrogen bonding joins the molecules into ribbons approximately parallel to c.
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  • 30
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    Journal of chemical crystallography 29 (1999), S. 203-206 
    ISSN: 1572-8854
    Keywords: Manganese(III) ; Schiff base ; hydrogen bonding ; crystal structure ; Jahn-Teller distortion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The manganese complex, (Mn2(III)(salpa)2Cl2(H2O)2], has been prepared and its structure determined using x-ray crystallography. The dimer is a di-μ2-alkoxo complex which is a six-coordinate manganese dimer with unsupported alkoxide bridges and a rare example of a chloride- and water-containing manganese dimer. The complex crystallizes in the monoclinic space group P21/c with a = 9.315(5), b = 11.130(4), c = 11.637(5) Å, β = 104.33(3)°, V = 1169.0(9) Å3, and Z = 2. The structure comprises discrete binuclear clusters in which the metal atoms are bridged by two alkoxo oxygens of the salpa2− ligands. The Mn—O and Mn—N distances are in good agreement with those found for other manganese(III) Schiff base complexes. The Mn—Cl and Mn—O3 distances are 2.585(2) and 2.371(2) Å, respectively, and the Mn ··· Mn distance is 3.001(1) Å. In the crystal, there are two types of hydrogen bonding between the H2O molecule and the Cl atom with Cl ··· H(H2O) distance of 2.33(6) (intramolecule: −1 + x, y, −1 + z) and 2.68(6) Å (intermolecule: −1 + x, 0.5−y, −0.5 + z).
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  • 31
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    Journal of chemical crystallography 29 (1999), S. 121-125 
    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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  • 32
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    Journal of chemical crystallography 29 (1999), S. 725-727 
    ISSN: 1572-8854
    Keywords: 2-thiouracil derivatives ; crystal structure ; S-methyl-thiouracil ; hydrogen bonding ; structural methylation and metallation effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2-S-Methylthiouracil crystallizes in the triclinic space group P $${\bar 1}$$ with unit cell dimensions a = 5.508(4), b = 7.175(3), c = 8.522(2) Å, α = 80.83(2), β = 80.43(3), γ = 76.86(3)°, and Z = 2. The molecule exists in the crystal in the lactam form and is essentially planar. The molecular packing consists of molecules linked in centrosymmetric hydrogen-bonded pairs. The effects of methylation and subsequent metallation on the 2-thiouracil structure are discussed.
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  • 33
    ISSN: 1572-8854
    Keywords: alkyne ; hydrogen bonding ; x-ray crystal structure
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    Topics: Geosciences , Physics
    Notes: Abstract In the x-ray crystal structure of the alkynol 5β-hydroxy-5α-ethynyl-10β-methyl-Δ1(9)-octalin-2-one [C13H16O2, Pbca, a = 10.244(7), b = 12.734(2), c = 17.125(2) Å, Z = 8], the hydroxyl and ethynyl groups are involved in a hydrogen bond arrangement C—C—H···O···H—O, which is supposed to be anticooperative, i.e., weaker than the sum of two isolated hydrogen bonds.
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  • 34
    ISSN: 1572-8854
    Keywords: Crystal structure ; norbornene ; stereoselective reduction
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    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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  • 35
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    Journal of chemical crystallography 25 (1995), S. 291-294 
    ISSN: 1572-8854
    Keywords: Crystal structure ; 1,2-di(1-adamantyl)ethene
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    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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  • 36
    ISSN: 1572-8854
    Keywords: Crystal structure ; pinacol ; reductive dimerization
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    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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  • 37
    ISSN: 1572-8854
    Keywords: Ruthenium(II) ; bipyridyl ; phenyldi(o-tolyl)phosphine ; solvate ; hydrogen bonding ; crystal structure
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    Topics: Geosciences , Physics
    Notes: Abstract The complexcis-[Ru(bpy)2{PPh(o-tolyl)2}Cl+][ClO4 −] crystallized from a solution in dichloromethane as the dichloromethane-water solvate. The structure was refined toR=4.5% for those 2433 reflections with |F o|〉6σ(|F o|). The octahedral Ru(II) cation is associated with metal-ligand distances as follows: Ru−Cl=2.434(3)Å, Ru-PPh(o-tol)2=2.382(2)Å, and Ru−N=2.037(7)–2.088(7)Å. The structure is stabilized by a hydrogen-bonded CH2Cl2...ClO4 −...H2O channel which incorporates adventitious water of crystallization.
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  • 38
    ISSN: 1572-8854
    Keywords: Crystal structure ; rubidium nitroprusside ; IR ; Raman ; thermal analysis
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    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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  • 39
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    Journal of chemical crystallography 26 (1996), S. 281-286 
    ISSN: 1572-8854
    Keywords: Crystal structure ; cyclopentadiene ; 2,3-dicyano-p-benzoquinone ; Diels-Alder reaction
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    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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  • 40
    ISSN: 1572-8854
    Keywords: Crystal structure ; undecen-olid ; nor-patulolide
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    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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  • 41
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    Journal of chemical crystallography 26 (1996), S. 483-487 
    ISSN: 1572-8854
    Keywords: Steroid conformation ; hydrogen bonding
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    Notes: Abstract The crystal structure of an orthorhombic polymorph of the title compound, crystallized by sublimation, has been determined. Dehydroepiandrosterone, C19H28O2, space groupP212121 witha=6.6408(4)b=11.4423(11)c=22.085(2)Å,V=1678.2(4)Å3,Z=4. The structure was refined toR=0.051 for 2645 observed reflections. The conformation of the molecule is similar to that found in other polymorphs and solvates, with a chair A ring, an 8β, 9α half-chair B ring, a chair C ring, and a 14α envelope D ring. Molecules are linked in chains by OH...O hydrogen bonds involving the carbonyl oxygen atom. The O...O distance is 2.855(3) Å, and the angle about H is 171(2)o.
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  • 42
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    Journal of chemical crystallography 26 (1996), S. 361-364 
    ISSN: 1572-8854
    Keywords: Crystal structure ; carboxylic acid ; phosphine oxide ; hydrogen bonding
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    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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  • 43
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    Journal of chemical crystallography 26 (1996), S. 425-428 
    ISSN: 1572-8854
    Keywords: Crystal structure ; tetracyclo[6.3.0.04,11.05,9]undecane-2,7-dione
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    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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  • 44
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    Journal of chemical crystallography 28 (1998), S. 741-746 
    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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  • 45
    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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  • 46
    ISSN: 1572-8854
    Keywords: M(acac)3 derivatives ; isomorphous ; β-diketonate ligands ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The molecular structures of Al(tfac)3 (1), Co(tfac)3 (2) (H-tfac = 1,1,1-trifluoroacetylacetone) and Cu(H2O)(fod)2 (3) (H-fod = 1,1,1,2,2,3,3-hepta-fluoro-7,7-dimethyloctane-4,6-dione) have been determined. The metal coordination spheres in compounds 1 and 2 are essentially the same as the respective M(acac)3 derivatives. Despite the isomorphous nature of the structures of compounds 1 and 2, the identity of the nearest intermolecular van der Waals contacts are altered by minor changes in the metal coordination sphere. The geometry about copper in compound 3 is close to that of an ideal square bipyramid with the β-diketonate ligands occupying the basal plane. The water ligand in each molecule of compound 3 is hydrogen bonded to an oxygen of a β-diketonate ligand on an adjacent molecule resulting in the formation of dimers, which form rods along the y-axis due to weak C–F···Cu interactions. Crystal data: (1) orthorhombic, Pca21, a = 14.949(3), b = 19.806(4), c = 13.624(3) Å, V = 4033(1) Å3, and Z = 8, and (2) orthorhombic, Pca21, a = 14.930(3), b = 19.620(4), c = 13.540(3) Å, V = 3966(1) Å3, and Z = 8,; (3) monoclinic, P21/c, a = 12.447(3), b = 10.486(2) c = 21.980(4) Å, β = 102.65(3)°, V = 2799(1) Å3, and Z = 4.
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  • 47
    ISSN: 1572-8854
    Keywords: Crystal structure ; centrosymmetric ; methoxybenzo [b] thiophene ; estrogen receptor ; tubulin
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    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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  • 48
    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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  • 49
    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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  • 50
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    Journal of chemical crystallography 28 (1998), S. 475-479 
    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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  • 51
    ISSN: 1572-8854
    Keywords: 1,10-Phenanthroline ; bis-phenanthrolineprotium ; adduct ; crystal structure ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Herzog's reported bis-1,10-phenanthrolineammonium perchlorate, [(phen)2(NH4)](ClO4) is in fact the known 2:1 adduct of l,10-phenanthroline (phen) with perchloric acid, [(phen)2H](CIO4). Its crystal structure, mode of formation, and properties are described. The compound crystallizes in the triclinic space group with $$P\bar 1$$ , a = 7.2510(8), b = 13.120(2), c = 22.083(12) Å, α = 77.4550(12), β = 84.45(2), γ = 82.204(14)°, V = 2026.7(6) Å3, Z = 4, and D c = 1.510 g cm−3. It contains cationic columns of alternating 1,10-phenanthroline and its conjugate acid.
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  • 52
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    Journal of chemical crystallography 29 (1999), S. 15-18 
    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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  • 53
    ISSN: 1572-8854
    Keywords: 3-Amino-1,2,4-triazole ; hydrogen bonding ; x-ray crystal structure
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    Topics: Geosciences , Physics
    Notes: Abstract 3-Amino-1,2,4-triazolium (3-AT) 5-nitrofuran-2-carboxylate has been prepared and its x-ray crystal structure reported (a = 12.363(3) Å, b = 12.5720(10) Å, c = 12.8550(10) Å, Pbca, orthorhombic, Z = 8, and D c = 1.604 mg m−3). The solid-state packing of this organic acid-base salt consists of a three-dimensional hydrogen-bonded network which exhibits a cage-like repeat unit involving both the N(2)–H and N(4)–H sites of 3-AT. A review of five such structures reveals that in all cases the carboxylate groups interact with either of these sites [and the N(31)H2] and form a R 2 2(8) graph set interaction. Analysis of all 3-AT complexes which form this interaction reveals that the hydrogen-bonding distances between the non-hydrogen atoms are not equal [av. 2.712(5) Å and 2.897(5) Å], with the shorter distance being the interaction between the heterocyclic nitrogen and the corresponding carboxylate oxygen. Furthermore, a review of the interactive modes of all 3-AT adducts has been undertaken.
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  • 54
    ISSN: 1572-8854
    Keywords: Melaminium dinitramide and melaminium nitrate ; melaminium salts ; dinitramide salt ; hydrogen bonding ; X-ray structure ; energetic materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Two energetic salts of the melaminium cation have been prepared and structurally characterized from room temperature X-ray single crystal diffraction data. Melaminium dinitramide (I), triclinic, P1¯, a = 6.6861(11), b = 6.9638(16), c = 10.447(2) Å , α = 99.07(3), β = 98.30(3), γ = 108.50(3)°, V = 445.6(2) Å3, and Z = 2. Melaminium nitrate (II), monoclinic, P21/c, a = 3.5789(7), b = 20.466(4), c = 10.060(2) Å, β = 94.01(2)°, V = 735.0(3) Å3, and Z = 4. The crystal structures of both salts show distinct monoprotonated melaminium cations and dinitramide- or nitrate anions, respectively. Efficient packing in the solid state is achieved by extensive hydrogen bonding between two-dimensional zigzag ribbons of the melaminium cations and the respective anions resulting in high densities of the solid state structures of 1.74 (I) and 1.71 g/cm3 (II).
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  • 55
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    Journal of chemical crystallography 29 (1999), S. 99-102 
    ISSN: 1572-8854
    Keywords: Isoflavone ; natural compound ; Dalbergia spinosa ; X-ray crystal structure ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of the plant isoflavone dalspinin from Dalbergia spinosa is determined. The compound, C17H12O7, is monoclinic in P21/n with a = 3.970(1), b = 23.607(5), c = 14.633(3) Å, β = 94.46(3)°, V = 1367.2(5) Å3, D calc = 1.595 g cm−1 and Z = 4. The molecular structure is characterized by a short intramolecular O–H···O=C hydrogen bond, and a large tilt angle of the two rigid ring systems with respect to each other. The intermolecular interactions in the crystal are discussed.
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  • 56
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    Journal of chemical crystallography 28 (1998), S. 581-584 
    ISSN: 1572-8854
    Keywords: Cyclohexane ; alkyne ; hydrogen bonding ; X-ray crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In the X-ray crystal structure of the alkynol 5β-hydroxy-5α-(prop-2-ynyl)-10β-methyl-Δ1(9)-octalin-2-one [C14H18O2, Pca2 1, a = 13.559(1), b = 7.960(2), c = 21.748(3) Å], the hydroxyl and propynyl groups form a hydrogen bond chain C---C-H⋯O-H⋯O which is supposed to be a cooperative arrangement. Quantum chemical calculations estimate cooperativity enhancement within the array to be 0.4 kcal/mol, which is only a small (but recognizable) effect.
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  • 57
    ISSN: 1572-8854
    Keywords: 1,4,10,13-Tetraoxa-7,16-diazacyclooctadecane ; 2,5-pyridinedicarboxylic acid ; 2,2′-dithiosalicylic acid ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A 1:2:2 complex of 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane with 2,5-pyridinedicarboxylic acid and water (1) and its 1:1:1.75 complex with 2,2′-dithiosalicylic acid and water (2) have been obtained and characterized by x-ray diffraction. C26H40N4O14 (1), triclinic, $$P\bar 1$$ , a = 9.574(1) Å, b = 9.632(1) Å, c = 9.723(1) Å, α = 112.70(1)°, β = 91.07(1)°, γ = 115.45(1)°, V = 728.35(13) Å3, Z = 1. C26H39.5N2O9.75S2 (2), M = 600.22, triclinic, $$P\bar 1$$ , a = 10.492(1) Å, b = 10.945(1) Å, c = 14.535(2) Å, α = 102.74(1)°, β = 109.08(1)°, γ = 90.68(1)°, V = 1532.2(3) Å3, Z = 2. In complex 1, both N-atoms of the macrocyclic ring are protonated. The following types of H-bonding have been found: (1) between protonated aza groups of the macrocycle and ionized carboxylic groups; (2) between the protonated aza groups and N-atoms of the pyridine nuclei (D–A distance slightly exceeds 3 Å); (3) between water molecules and C=O groups of the non-ionized carboxylic groups; and (4) between the nonionized and ionized groups of the carboxylic acid. The above interactions give rise to the formation of a developed supramolecular network in the crystals of 1. In complex 2, despite the presence of several types of hydrogen bonds involving the aza crown, 2,2′-dithiosalicylic acid and water, the aromatic anions are H-bound only to the two other components, and not to each other. The H-bonds found in complex 2 are between (1) one of the protonated aza groups and water, (2) protonated aza groups and O-atoms of the ionized carboxylic groups, (3) water molecule and carboxylic O-atom, (4) water molecule and sulfur atom, and (5) water molecule and O-atom of diaza-18-crown-6.
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  • 58
    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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  • 59
    ISSN: 1572-8854
    Keywords: silver ; pyridinecarboxylate ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Silver(I) complexes of 6-methyl-2-pyridinecarboxylic acid (HL) have been prepared, and the crystal structure of [Ag(L)(LH)] has been determined from X-ray diffraction data. This complex crystallizes in the monoclinic space group P21/n, with a = 13.4055(13), b = 7.1012(7), c = 15.588(2) Å, β = 112.779(2)°, and Z = 4. Anionic [AgL2]− units are linked together by protons in approximately symmetrical linear O—H—O hydrogen bonds involving uncoordinated carboxylate oxygen atoms, to give polymeric chains. The most significant intermolecular interaction between adjacent parallel chains is offset ring stacking of pairs of aromatic rings with a perpendicular distance of 3.27 Å. The Ag coordination geometry is highly distorted tetrahedral, from two pyridine N atoms and two carboxylate O atoms, each ligand forming a five-membered chelate ring.
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  • 60
    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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  • 61
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    Journal of chemical crystallography 29 (1999), S. 1235-1237 
    ISSN: 1572-8854
    Keywords: multiple phenyl interactions ; hydrogen bonding ; X-ray crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The x-ray crystal structure of 3,3,3-triphenylpropionic acid is determined [space group triclinic P-1 (No. 2) with a = 9.789(8), b = 9.946(8), c = 10.058(7) Å, α = 65.71(6), β = 63.77(5), γ = 85.37(6)°, and D calc = 1.264 g cm−1 for Z = 2]. The molecules form molecular columns which are organized by alternate carboxylic acid dimers and sixfold phenyl embraces.
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  • 62
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    Journal of chemical crystallography 29 (1999), S. 145-156 
    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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  • 63
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    Journal of chemical crystallography 29 (1999), S. 351-354 
    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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  • 64
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    Journal of chemical crystallography 25 (1995), S. 747-750 
    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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  • 65
    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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  • 66
    ISSN: 1572-8854
    Keywords: Crystal structure ; pentacycloundecan-8-one ; pentacycloundecane-8,11-dione
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    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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  • 67
    ISSN: 1572-8854
    Keywords: Crystal structure ; diyne ; oxidative dimerization
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    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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  • 68
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    Journal of chemical crystallography 26 (1996), S. 695-699 
    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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  • 69
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    Journal of chemical crystallography 26 (1996), S. 801-806 
    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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  • 70
    ISSN: 1572-8854
    Keywords: Thiosemicarbazone ; 2-benzoylpyridine ; N4-substituted ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2-Benzoylpyridine N4-methyl-N4-phenylthiosemicarbazone, HBz4MePh, monoclinic,P2(1)/n a=9.141(2),b=18.507(4),c=11.401(2) Å, β=110.58(3)o,V=1805.6(9) Å3,Z=4, μ=1.655 mm−1. HBz4MePh crystallizes in a hydrogen bonded Z isomeric conformation with respect to the C7−N2 bond. The intramolecular hydrogen bond is between N3−H...N1, and the S atom isZ to the azomethine nitrogne, N2.
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  • 71
    ISSN: 1572-8854
    Keywords: Betaine ; 4-dimethylaminopyridinioacetate ; hydrogen bonding ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystalline dihydrate and hydrochloride trihydrate of a new betaine, namely, L·2H2O (1) and [L2H]Cl·3H2O(2) (L=p-Me2NC5H4N+CH2CO2), have been synthesized and characterized by X-ray crystallography. Molecule L in compound1 [space groupPbcn, witha=15.732(3),b=7.894(2),c=18.304(4) Å, andZ=8] possesses approximateC s symmetry. The formation of hydrogen bonds by water molecules bridging neighboring carboxy oxygen atoms leads to an infinite two-dimensional network composed of a packing of two different kinds of 12-membered rings. In compound2 [space group PT witha=7.341(2),b=9.543(2),c=17.010(4) Å, α=82.43(2)°, δ=80.34(2)°, λ=74.05(2)°, andZ=2], the carboxylate groups of a pair of betaine molecules are bridged by a proton to form a dimeric cation L2H+ with a very strong asymmetric hydrogen bond of length 2.464(7) Å. The crystal structure features a hydrogen-bonded corrugated ribbon comprising an alternate arrangement of edge-sharing centrosymmetric (H2O)4(Cl−)2 and (H2O)4 rings running parallel to thea axis.
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  • 72
    ISSN: 1572-8854
    Keywords: Bidentate ligand ; crystal structure ; pyrazolyl group ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound lies on a site of C2 symmetry, with the two planar pyrazolyl moieties oriented at 86.1° to one another. The hydrogen atoms were located and refined.
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  • 73
    ISSN: 1572-8854
    Keywords: Pyrazolyl group ; crystal structure ; bidentate ligand ; hydrogen bonding
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    Topics: Geosciences , Physics
    Notes: Abstract The title compound consists of two planar pyrazolyl fragments oriented at 73.0° to each other and linked to a common carbon atom. All hydrogen atoms were located unambiguously and their positions were refined.
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  • 74
    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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  • 75
    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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  • 76
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    Journal of chemical crystallography 26 (1996), S. 639-642 
    ISSN: 1572-8854
    Keywords: Crystal structure ; chiral auxiliaries
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    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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  • 77
    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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    Journal of chemical crystallography 28 (1998), S. 39-46 
    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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  • 79
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    Journal of chemical crystallography 28 (1998), S. 259-266 
    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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  • 80
    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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  • 81
    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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  • 82
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    Journal of chemical crystallography 28 (1998), S. 649-651 
    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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  • 83
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    Journal of chemical crystallography 29 (1999), S. 323-327 
    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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  • 84
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    Journal of chemical crystallography 29 (1999), S. 347-349 
    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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  • 85
    ISSN: 1572-8854
    Keywords: 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane ; 2,6-dihydroxyanthraquinone ; hydrogen bonding ; ribbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A 1:2:2 complex of diaza crown ether 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane, anthraflavic acid (2,6-dihydroxyanthraquinone) and water has been synthesized. The crystal is triclinic, P1, with a = 7.705(2), b = 10.871(2), c = 11.540(2) Å, α = 100.40(2), β = 91.38(2), γ = 98.01(2)°, Z = 1, and Dcalc = 1.375 mg m−3. The main feature of the crystal structure is the formation of a supramolecular sheet by hydrogen bonding of the anthraflavic monoanions, not only head-to-tail through the hydroxyl oxygens, but sideways through the quinone oxygens. This complex represents an intermediate case between total transfer of protons of a hydroxy-guest to crown N-atoms, and no transfer.
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  • 86
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    Journal of chemical crystallography 29 (1999), S. 355-358 
    ISSN: 1572-8854
    Keywords: Quinestrol ; sex steroid ; alkyne ; crystal structure ; solvent inclusion ; hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of the synthetic sex steroid quinestrol (3-O-cyclopentyl-17α-ethynylestradiol) as crystallized from ethanolic solution is determined. The asymmetric unit contains two steroid and one ethanol molecules. The conformation of the two steroid molecules differs in the orientation of the cyclopentane ring. The cocrystallized ethanol molecule facilitates formation of cooperative O—H···O hydrogen bonding. The title compound crystallizes in the monoclinic space group P21, with a = 13.950(6), b = 6.5945(8), c = 25.403(8) Å, β = 104.78(4)°, and D calc = 1.136 g cm−1 for Z = 4.
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  • 87
    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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  • 88
    ISSN: 1432-0789
    Keywords: Crop rotation ; Field pea ; Mineral N ; Nitrogen fixation ; immobilisation ; Pisum sativum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of soil incorporation with cereal straw (nil, 2.5, 5 and 10 t straw ha−1) and direct drilling on the proportion and amount of pea N derived from biological N fixation were investigated in three field experiments. Fixed N was determined by15N dilution using barley as a reference plant. The three sites were on acidic, red clay-loams in the cropping zone of southeastern Australia. Seasonal plant available soil N, as determined by the N accumulated in barley, was 31, 56 and 158 kg N ha−1, for the three sites. Incorporated straw reduced soil nitrate at sowing by 10–50 kg N ha−1 (0–30 cm), and 5 or 10 t straw ha−1 reduced barley uptake of N by 10–38 kg N ha−1. However, reducing plant available soil N was generally ineffective for increasing the N fixed by pea. Fixed N increased only at the site with the least plant-available N, and only one-third of the increase could be attributed to lower soil N uptake by pea. There was no evidence that direct drilling pea increased fixed N by decreasing crop uptake of soil N. It is proposed that a lower requirement for soil N by pea as compared to barley, and availability of mineral N beneath the soil layer treated with straw, minimise the effectiveness of straw incorporation for increasing the N fixed by pea.
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  • 89
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    Biology and fertility of soils 24 (1997), S. 111-117 
    ISSN: 1432-0789
    Keywords: Denitrification ; Acetylene inhibition method ; Nitrous oxide release ; Soilless plant culture ; Root growth ; Cucumis sativus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Denitrification measurements by means of the acetylene inhibition method require a continuous presence of acetylene to block the microbial reduction of N20 to N2. To examine the effect of such steady exposures on the growth of plants, roots of cucumber and tomato seedlings were treated with different acetylene concentrations. Acetylene concentrations of ≥1 vol% in the gas phase, which were necessary for complete inhibition of N2 formation, led to a significant retardation of root growth. This was partly due to trace amounts of ethylene contained in the acetylene gas which could not be removed with the usual prescrubbing through a sulfuric acid train. As a result of the growth impairment, oxygen consumption in the root zone decreased after 4 days of exposure. In order to avoid these side effects, the denitrification measurements in soilless cultures were performed on individual plants over a limited period of 2–3 days. The flow-through chamber method proved to be suitable for determining the gaseous N losses in a closed-loop system. It avoided greater air variations from the environmental conditions (substrate temperature, airflow and plant composition) and excluded errors in measurement caused by injury to roots and spatial variability of denitrification activity in the root medium. For exact estimation of the gaseous N losses, preceding 24-h acetylene fumigation was necessary. Subsequently at least three gas samples had to be taken throughout the day, because the N2O+N2 emissions were subject to a pronounced diurnal variability.
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  • 90
    ISSN: 1432-0789
    Keywords: Key words Crop rotation ; Field pea ; Mineral N ; Nitrogen fixation ; immobilisation ; Pisum sativum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of soil incorporation with cereal straw (nil, 2.5, 5 and 10 t straw ha–1) and direct drilling on the proportion and amount of pea N derived from biological N fixation were investigated in three field experiments. Fixed N was determined by 15N dilution using barley as a reference plant. The three sites were on acidic, red clay-loams in the cropping zone of southeastern Australia. Seasonal plant available soil N, as determined by the N accumulated in barley, was 31, 56 and 158 kg N ha–1, for the three sites. Incorporated straw reduced soil nitrate at sowing by 10–50 kg N ha–1 (0–30 cm), and 5 or 10 t straw ha–1 reduced barley uptake of N by 10–38 kg N ha–1. However, reducing plant available soil N was generally ineffective for increasing the N fixed by pea. Fixed N increased only at the site with the least plant-available N, and only one-third of the increase could be attributed to lower soil N uptake by pea. There was no evidence that direct drilling pea increased fixed N by decreasing crop uptake of soil N. It is proposed that a lower requirement for soil N by pea as compared to barley, and availability of mineral N beneath the soil layer treated with straw, minimise the effectiveness of straw incorporation for increasing the N fixed by pea.
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  • 91
    ISSN: 1432-0789
    Keywords: Key words Grassland ; Denitrification ; N-fertiliser ; Nitrification ; Nitrous oxide emissions ; Global warming ; Ozone layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aim was to investigate the effects of different N fertilisers on nitrous oxide (N2O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N2O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N2O flux and soil and environmental variables. The loss of N2O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2, 1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd year gave an average emission factor of 0.8% – lower than from application of either individual fertiliser. We suggest that similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed to minimise N2O emissions from agricultural land.
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  • 92
    ISSN: 1432-0789
    Keywords: Key words Grassland ; Spring barley ; Nitrification inhibitor ; Nitrous oxide emission ; Denitrification ; Global warming ; Ozone layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aims of this study were to assess the effectiveness of the nitrification inhibitors dicyandiamide (DCD) and nitrapyrin on reducing emissions of nitrous oxide (N2O) following application of NH4 + or NH4 +-forming fertilisers to grassland and spring barley. DCD was applied to grassland with N fertiliser applications in April and August in 1992 and 1993, inhibiting N2O emissions by varying amounts depending on the fertiliser form and the time of application. Over periods of up to 2 months following each application of DCD, emissions of N2O were reduced by 58–78% when applied with urea (U) and 41–65% when applied with ammonium sulphate (AS). Annual emissions (April to March) of N2O were reduced by up to 58% and 56% in 1992–1993 and 1993–1994, respectively. Applying DCD to ammonium nitrate (AN) fertilised grassland did not reduce emissions after the April 1993 fertilisation, but emissions following the August application were reduced. Nitrapyrin was only applied once, with the April fertiliser applications in 1992, reducing N2O emissions over the following 12 months by up to 40% when applied with U. When N fertiliser was applied in June without DCD, the DCD applied in April was still partly effective; N2O emissions were reduced 50%, 60% and 80% as effectively as the emissions following the April applications, for AS in 1993, U in 1992 and 1993, respectively. In 1992 the persistence of an inhibitory effect was greater for nitrapyrin than for DCD, increasing after the June fertiliser application as overall emissions from U increased. There was no apparent reduction in effectiveness following repeated applications of DCD over the 2 years. N2O emissions from spring barley, measured only in 1993, were lower than from grassland. DCD reduced emissions from applied U by 40% but there was no reduction with AN. The results demonstrate considerable scope for reducing emissions by applying nitrification inhibitors with NH4 + or NH4 +-forming fertilisers; this is especially so for crops such as intensively managed grass where there are several applications of fertiliser nitrogen per season, as the effect of inhibitors applied in April persists until after a second fertiliser application in June.
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  • 93
    ISSN: 1432-0789
    Keywords: Wetland rice soils ; Nitrogen fixation ; Sesbania rostrata ; PK fertilization ; Soil Mn ; Acetylene reduction assay ; ARA ; Green manure ; N dilution method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The performance of Sesbania rostrata varies widely from site to site. This makes it difficult to predict the N yield and biomass of this plant in marginally productive soils, and to arouse the interest of farmers in green manure technology. Three consecutive pot experiments were conducted in a greenhouse at the International Rice Research Institute (IRRI) to evaluate growth, nodulation, N2 fixation (C2H2 reduction assay and 15N dilution method), and N yield of 6-week-old S. rostrata on 13 physicochemically different wetland rice soils of the Philippines and on three artificial substrates. The performance of S. rostrata on the unfertilized controls was compared with two fertilizer treatments containing either P (100 mg P kg-1 dry soil) or P+K (100 mg P kg-1 and 200 mg K kg-1 dry soil). In the control soils and substrates, the N yield of S. rostrata varied between 20 and 470 mg N per pot, with the N rate from N2 fixation ranging between 0 and 95%. In three of the nutritionally poor soils even Mn toxicity symptoms apparently occurred with S. rostrata. P application alleviated these symptoms and increased the overall N yield considerably, mainly through increased biological N2 fixation. An additional increase in N yield was obtained by the PK treatment. Multiple regression analysis between soil characteristics and the N yield of S. rostrata showed that the original level of P (Olsen-extracted) and Mn in the soil accounted for 73% of the variance in biomass production by S. rostrata among the unfertilized soils and substrates.
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  • 94
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    Biology and fertility of soils 20 (1995), S. 147-150 
    ISSN: 1432-0789
    Keywords: Faba bean ; Water stress ; Nodulation ; Nitrogen fixation ; Leghaemoglobin ; Invertase ; Protease ; K fertilizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three-week-old nodulated faba bean plants were subjected to different levels of drought stress (onehalf, one-quarter, or one-eighth field capacity) for 5 weeks. Half the stressed plants were treated with KCl at 10 mg kg-1 soil or 150 mg kg-1 soil at the beginning of the drought stress. Nodulation and nitrogenase activity were significantly decreased by increasing drought stress. Leghaemoglobin and protein contents of nodule cytosol were also severely inhibited by drought sttess. This decline was attributed to the induction of protease activity. However, carbohydrate contents of the nodule cytosol increased significantly. This accumulation was attributed to a sharp decline in invertase activity and low use of sugar by the bacteroids We conclude that harmful effects of water deficits can be alleviated by increasing K+ supplementation.
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  • 95
    ISSN: 1432-0789
    Keywords: Leucaena ; Nodulation ; Nitrogen fixation ; Nitrogen use ; 15N ; Time course
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The dynamics of nodulation, N2-fixation and N use in Leucaena leucocephala cv. K28 over time was investigated in a screenhouse at 4, 8, 12 and 16 months after planting (MAP) using the 15N-labelling method. Leucaena had a consistently increasing pattern of nodulation, dry biomass and nitrogen yield. A sharp rise in nodulation was observed between 12 and 16 MAP, whereas for biomass, N accumulation and N2-fixation, and N2-fixation, an upward surge occurred between 4 and 12 months. Nodulation, N accumulation, N2-fixation and biomass yield all peaked at 16 MAP. Along with the steady increase in N2-fixation throughout the 16-month growth period, the % N derived from the atmosphere rose from 17.9% to 61.5%, 70.1% and 74%, equivalent to 191, 1623, 2395 and 3385 mg N2 fixed plant-1 at 4, 8, 12 and 16 MAP, respectively. Nitrogen assimilation from soil and fertilizer decreased inversely to the increase in symbiotic nitrogen fixation with time.
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  • 96
    ISSN: 1432-0789
    Keywords: Mungbean ; Vigna radiata ; Nitrogen fixation ; Hydrogen uptake ; Mutation ; Nitrosoguanidine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract H2 uptake activity was well distributed in Rhizobium sp. strains isolated from nodules of mung-bean (Vigna radiata L.). Two effective strains, RMP1 und RMP2, exhibiting significantly higher H2 uptake activity were subjected to mutagenesis with nitrosoguanidine. The respective mutation frequencies were 0.18 and 0.19%. Three Hup- mutants each of RMP1 und RMP2 were compared with the wild-type parent strains under pot culture experiments to evaluate the significance of the H2 uptake system in biological N2 fixation. Nodulation capabilities, plant growth characteristics, and the chlorophyll content of the leaves were significantly reduced in the plants treated with Hup- mutants. Nitrogenase activity in Hup- nodules was reduced by 8–41%. Similarly, N accumulation was also reduced singificantly.
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  • 97
    ISSN: 1432-0789
    Keywords: Herbaspirillum ; Endophytes of Gramineae ; Diazotrophs ; Survival in soil ; Nitrogen fixation ; sugarcane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Since the first description of Herbaspirillum seropedicae in 1986, few data have been published on this diazotroph, possibly due to difficulties in isolating it from soil. In the present study we found that this bacterium seems to be an obligate endophyte which has been isolated from roots, stems, and leaves of a large number of samples of more than 10 different species of the Gramineae family, but only exceptionally from other plants. H. rubrisubalbicans, previously misnamed as “Pseudomonas” rubrisubalbicans, and known as a mild pathogen of sugarcane causing mottled stripe disease, confirms the endophytie habitat of this genus. This species occurs in roots, stems, and leaves of sugarcane and seems to be restricted to this crop. Inoculation of strains from both species into soil in high numbers resulted in a rapid decline in their numbers. In only 30 days the population of Herbaspirillum spp. in soil decreased below detection limits (〈100 cells g-1). When sorghum was planted in this soil, the bacteria reappeared and multiplied within the plant tissues.
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  • 98
    ISSN: 1432-0789
    Keywords: Key words Acetylene reduction assay ; Anabaena sp. ; Ammonium ; Cyanobacteria ; Nitrogen fixation ; Wetland rice fields ; Nitrogenase activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Short- and long-term experiments were conducted in the rice fields of Valencia, Spain, to determine the ecological significance of ammonium on nitrogen fixation. A significant inhibition of nitrogenase activity by ammonium, at concentrations higher than 0.5mM, was observed after 8h of incubation in short-term experiments done with a bloom of the N2-fixing cyanobacterium Anabaena sp. In a second set of short-term experiments for in situ assays of nitrogenase activity in the field, a significant correlation between nitrogenase activity and the number of N2-fixing cyanobacteria in soil was found. No significant inhibition of nitrogenase activity by ammonium at concentrations up to 2mM was observed in these assays after 24h of incubation. This lack of inhibition was probably due to the rapid decrease in ammonium content in the flood water. Only 5% of the ammonium initially added remained in the water 24h later. In the long-term experiments, nitrogenase activity was assayed in plots fertilized with 0, 70 and 140kgNha–1, over the cultivation cycle, for 5 years. A partial inhibition of nitrogenase activity by deep-placed N fertilizers was observed. Differences were only significant in 2 years. Mean results from 5 years only showed significant differences between plots fertilized with 0 and 140kgNha–1. The partial inhibition of nitrogenase activity by ammonium increased over the cultivation cycle. Inhibition was only significant in September, at the end of the cultivation cycle.
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  • 99
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 25 (1997), S. 407-415 
    ISSN: 1432-0789
    Keywords: Key wordsBradyrhizobium japonicum ; Bradyrhizobium elkanii ; Genetic variability ; Glycine max ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Several years of research have shown that there is a high genetic and physiological variability among Bradyrhizobium japonicum strains, culminating in a subdivision into two bacterial genotypes, and the description of the new species B. elkanii. In Brazil, large-scale soybean inoculation started in 1960 and today 15 million doses of inoculants are sold per year for an estimated area of 12 million ha. Efforts have been made to find strains able to fix high amounts of N2 under Brazilian soil conditions, but few laboratories cover basic studies on N2 fixation, such as strain classification into the two Bradyrhizobium species. In this study several characteristics of 40 soybean Bradyrhizobium strains, including 4 reference strains of B. japonicum (genotype I) species, 3 of B. elkanii (genotype II) and 1 of a mixed genotype were evaluated. The parameters analysed in vitro were: colony morphology, serological grouping, intrinsic resistance to antibiotics, synthesis of indole acetic acid, expression of hydrogenase activity and growth in a medium enriched with asparagine. In vivo, analyses performed included the nodulation of Rj 4 soybean cultivar Hill and the detection of symptoms caused by rhizobitoxine. These evaluations allowed a phenotypic grouping which positioned most of the strains utilized in Brazilian inoculants and studies, as well as some new strains isolated from the Cerrado region, within the species B. elkanii. However, environmental stresses and adaptation of Bradyrhizobium strains to the soil caused a large physiological and genetic variability in some isolates from the Cerrado soils in relation to the putative parental strain introduced 15 years ago, placing these isolates in an intermediate position between the two Bradyrhizobium species.
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  • 100
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 27 (1998), S. 60-64 
    ISSN: 1432-0789
    Keywords: Key words Acacia spp. ; Bradyrhizobium ; Rhizobium ; Nitrogen fixation ; Nitrogen accumulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Endosymbionts from the Ethiopian highland acacia species Acacia abyssinica, A. negrii and A. etbaica, and the lowland species A. nilotica, A. prasinata, A.senegal, A. seyal, A. tortilis and Faidherbia (Acacia) albida were isolated and characterized. Seven tree species were found to be nodulated by species of both Rhizobium and Bradyrhizobium. F. (Acacia) albida and A. senegal were nodulated by only Bradyrhizobium or Rhizobium, respectively. In A. abyssinica, both genera were isolated from the same nodule, whereas in A. nilotica and A. tortilis, both strains were isolated from different nodules of the same plant. The nitrogen fixation (acetylene reduction) activities varied considerably and showed no correlation with the nitrogen content of the plant. Highland species were as effective as lowland plants, thus demonstrating good potential for soil reclamation. The endosymbionts isolated proved rather promiscuous, efficiently nodulating other Acacia spp. and some tropical grain legumes, but did not nodulate temperate legumes.
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