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  • Artikel  (203)
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  • 1
    Digitale Medien
    Digitale Medien
    Crystal structure of Pt(S2COEt)2 (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 707-710 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; platinum ; xanthate ; square planar
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystals of Pt(S2COEt)2 are orthorhombic, Pbca, with (at 20°C)a=7.799(3),b=7.368(6),c=20.588(7) Å.D cale=2.46g cm−3 forZ=4. The platinum atom resides on a crystallographic center of inversion and is bound to the four sulfur atoms of the xanthato ligand in a square planar geometry. The Pt−S distances are 2.313(6) and 2.320(7)Å with an intraligand S−Pt−S angle of 75.1(2)°.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01668235
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  • 2
    Digitale Medien
    Digitale Medien
    Crystal structure of tetrakisdiphenylammonium hexadecachlorotetrabismuthate(III) (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 841-844 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; bismuth chloride complexes ; diphenylammonium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01671080
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  • 3
    Digitale Medien
    Digitale Medien
    Crystal structure of a bulky cyclic sulfite (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 215-218 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; cyclic sulfite ; pentacycloundecane-8 ; 11-dione
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665171
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  • 4
    Digitale Medien
    Digitale Medien
    Structure of the pinacol formed via sodium-promoted reductive dimerization of 12-methyleneheptacyclo-[6.6.02,6.03,13.04,11.05,9.010,14]tetradecan-7-one (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 417-420 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; pinacol ; reductive dimerization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665280
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  • 5
    Digitale Medien
    Digitale Medien
    Crystal and molecular structure of 1-vinyl-3-methyl-imidazolium iodide, C6H9N2I (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 601-603 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; imidazolium ; vinyl
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01667031
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  • 6
    Digitale Medien
    Digitale Medien
    Molecular structure of 3-(3-oxo-bicyclo[2.2.1]hept-5-en-2-yl)-oxirane-2-carboxylic acid methyl ester (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 81-84 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; epoxy ester
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02018702
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  • 7
    Digitale Medien
    Digitale Medien
    Crystal structure of a highly hydrated tristrontium phosphate, Sr9(PO4)6·16H2O (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 341-346 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; hydrated phosphate ; layer-type structure ; strontium phosphate ; strontium phosphate hydrate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01677098
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  • 8
    Digitale Medien
    Digitale Medien
    Molecular structure of [(tBu)2Al(μ-NHtBu)]2 (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 563-567 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; aluminum ; amide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01668416
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  • 9
    Digitale Medien
    Digitale Medien
    Crystal structure of 5-(p-methoxyphenylamino)indane and AM1 calculations on N-arylamines derivatives, precursors of phenothiazine drugs (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 735-739 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; diphenyl amines ; AM1 calculations ; phenothiazines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021860410863
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  • 10
    Digitale Medien
    Digitale Medien
    Synthesis, characterization, and X-ray crystal structure of di-(2,4-imidazolidinedione-5-ethyl)disulfide, C10H14N4O4S2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 761-765 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; noncentrosymmetric ; disulfide ; imidazolidinedione ; homocystine hydantoin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021816628610
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  • 11
    Digitale Medien
    Digitale Medien
    Crystal structure of a macrocyclic tetraamine isocyanato zinc(II) complex (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 831-834 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; macrocyclic tetraamine ; isocyanato zinc(II) complex
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021831921283
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  • 12
    Digitale Medien
    Digitale Medien
    Synthesis and crystal structure of macrocyclic nickel(II) complex bridged by chromate (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 867-870 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; macrocyclic nickel(II) complex ; chromate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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−.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022890217250
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  • 13
    Digitale Medien
    Digitale Medien
    Synthesis, characterization, peripheral studies, and structural analysis of E-4-(N-methylanilino)-3-pentene-2-one, C12H15NO (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 899-903 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; ir/nmr ; β-amino-α ; β-unsaturaled ketone ; noncentrosemmtric ; enamino ketones
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022802619976
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  • 14
    Digitale Medien
    Digitale Medien
    The structure of N-(1H-benzo[d]imidazol-2-ylmethyl)-N-(2,6-dichlorophenyl)amine (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 145-147 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; benzimidazole ; antimicrobial activity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022497931783
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  • 15
    Digitale Medien
    Digitale Medien
    Synthesis and structural characterization of a novel polymeric praseodymium(III) complex with a new flexible double betaine (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 177-183 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; coordination polymer ; praseodymium(III) carboxylate complex ; double betaine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022414109261
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  • 16
    Digitale Medien
    Digitale Medien
    Crystal structures of three substituted pentacyclo[5.4.0.02,6.03,10.05,9]undecanes (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 251-258 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; pentacycloundecane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021893001351
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  • 17
    Digitale Medien
    Digitale Medien
    Molecular structure and absolute configuration of (+)-(1R, 2S, 6R, 7S, 1′R)-5-(1′-phenylethylamino)-endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-one (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 497-499 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; tricyclodecadienone ; enaminone ; resolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021733108852
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  • 18
    Digitale Medien
    Digitale Medien
    Molecular structure and absolute configuration of (−)-(1R, 2S, 6R, 7S, 2′S)-5-(2′-hydroxymethylpyrrolidin-1′-yl)-endo-tricyclo[5.2.1.02,6]deca-4,8-dien-3-one (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 493-495 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; tricyclodecadienone ; enaminone ; dynamic kinetic resolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021781024782
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  • 19
    Digitale Medien
    Digitale Medien
    The crystal structure of 5α,9α-peroxyergosta-7,22-dien-6-one-3β-ol acetate (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 239-241 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; ergosterol peroxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022486730643
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  • 20
    Digitale Medien
    Digitale Medien
    The crystal structure of hexabenzoylhexaazaisowurtzitane (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 593-596 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; cage compound ; hexabenzoylhexaazaisowurtzitane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022452707772
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  • 21
    Digitale Medien
    Digitale Medien
    Structural study of the molecular complex in crystals of brucine with pantolactone (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 121-125 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; brucine ; pantolactone ; molecular complex ; chiral resolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009543903373
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  • 22
    Digitale Medien
    Digitale Medien
    Crystal structure of Pt(S2COEt)2 (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 711-714 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; platinum ; xanthate ; square planar
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystals of Pt(S2COEt)2 are orthorhombic, Pbca, with (at 20°C)a=7.799(3),b=7.368(6),c=20.588(7) Å,D cale=2.46g cm−3 forZ=4. The platinum atom resides on a crystallographic center of inversion and is bound to the four sulfur atoms of the xanthato ligand in a square planar geometry. The Pt−S distances are 2.313(6) and 2.320(7) Å with an intraligand S−Pt−S angle of 75.1(2)°.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01668236
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  • 23
    Digitale Medien
    Digitale Medien
    Highly stereoselective sodium borohydride promoted reduction ofendo-5-acetyl-1,2,3,4-tetrachloro-7,7-dimethoxynorborn-2-ene (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 657-660 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; norbornene ; stereoselective reduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665972
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  • 24
    Digitale Medien
    Digitale Medien
    Structure of 2-acetoxy-1,2-di(1-adamantyl)ethanone (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 291-294 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; 1,2-di(1-adamantyl)ethene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01796052
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  • 25
    Digitale Medien
    Digitale Medien
    Structure of a PCU-derived pinacol formed via sodiumpromoted reductive dimerization of pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione monoethylene ketal (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 517-520 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; pinacol ; reductive dimerization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665710
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  • 26
    Digitale Medien
    Digitale Medien
    Crystal and molecular structure determination, TGA-DTA, and infrared and Raman spectra of rubidium nitroprusside, Rb2[Fe(CN)5NO] (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 325-330 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; rubidium nitroprusside ; IR ; Raman ; thermal analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01677095
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  • 27
    Digitale Medien
    Digitale Medien
    Thermodynamic vs. kinetic control in the Diels-Alder cycloaddition of cyclopentadiene to 2,3-dicyano-p-benzoquinone (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 281-286 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; cyclopentadiene ; 2,3-dicyano-p-benzoquinone ; Diels-Alder reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01677782
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  • 28
    Digitale Medien
    Digitale Medien
    Crystal and molecular structure of (2E,4S,10R)-4-hydroxy-2-undecen-10-olide (nor-patulolide C), C11H18O3 (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 305-308 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; undecen-olid ; nor-patulolide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01677787
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  • 29
    Digitale Medien
    Digitale Medien
    Crystal and molecular structure of diphenylphosphinylacetic acid (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 361-364 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; carboxylic acid ; phosphine oxide ; hydrogen bonding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01677101
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  • 30
    Digitale Medien
    Digitale Medien
    Tetracyclo[6.3.0.04,11.05,9]undecane-2,7-dione (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 425-428 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; tetracyclo[6.3.0.04,11.05,9]undecane-2,7-dione
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665823
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  • 31
    Digitale Medien
    Digitale Medien
    Crystal structure of strontium potassium arsenate octahydrate (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 741-746 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; hydrated ions ; ionic hydration ; strontium arsenate ; struvites ; struvite-type structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021812527701
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  • 32
    Digitale Medien
    Digitale Medien
    Crystal structures of a series of 3,7-bis-(arylazo)-1,3,5,7-tetraazabicyclo[3.3.1]nonanes (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 797-809 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; bicyclononane ; triazene ; bis-triazene ; nitrile substituent ; nitro substituent ; trifluoromethyl substituent ; hydrogen bonding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021823619465
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  • 33
    Digitale Medien
    Digitale Medien
    Characterization and structural analyses of trimethoxy and triethoxybenzo[b]thiophene (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 289-295 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; centrosymmetric ; methoxybenzo [b] thiophene ; estrogen receptor ; tubulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021853320007
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  • 34
    Digitale Medien
    Digitale Medien
    Synthesis and crystal structure of a polymeric erbium(III)–sodium(I) coordination complex of picolinic acid N-oxide (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 413-418 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; coordination polymer ; erbium(III)–sodium(I) carboxylate complex ; picolinic acid N-oxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022424511580
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  • 35
    Digitale Medien
    Digitale Medien
    Crystal structure and two-stage hydrolysis of dimethoxo (meso-tetra(4-methoxyphenylporphyrinato))tin(IV), Sn(tmpp)(OMe)2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 481-486 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; tin porphyrin ; two-stage hydrolysis ; methanolate ; trans equivalent axial ligand
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021776923873
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  • 36
    Digitale Medien
    Digitale Medien
    Synthesis and structural characterization of a novel polymeric gadolinium(III)–copper(II) complex of iminodiacetic acid (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 475-479 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; coordination polymer ; gadolinium(III)-copper(II) complex ; iminodiacetic acid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021724807035
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  • 37
    Digitale Medien
    Digitale Medien
    Structure of a deaza dimer of 4-methyl-3H-1,2,4-triazole-3,5(4H)-dione (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 15-18 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; dimer ; triazole
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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°.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009558912034
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  • 38
    Digitale Medien
    Digitale Medien
    Crystal structures of two substituted biphenyl derivatives: 5,5′-di t-butyl-2-2′-biphenyldiol and 5,5′-dimethyl-2,2′-biphenyldiol (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 157-161 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; biphenyl ; mutual orientation ; strong H-bonds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009509808535
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  • 39
    Digitale Medien
    Digitale Medien
    Synthesis, spectroscopic studies, and crystal structure of tris(tetra-n-butylammonium) hexakisisothiocyanatoindate(III) (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 317-321 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; indium complexes ; isothiocyanate complexes ; octahedral coordination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009525918781
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  • 40
    Digitale Medien
    Digitale Medien
    Crystal structures of a series of 3,8-di[-2-aryl-1-azenyl]-1,3,6,8-tetraazabicyclo[4.4.1]undecanes (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 145-156 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; bicycloundecane ; triazene ; bis-triazene ; nitro substituent ; carboalkoxy substituent ; π–π stacking
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009557724465
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  • 41
    Digitale Medien
    Digitale Medien
    Synthesis and crystal structure of 4,5-dibromo[2.1.1]triblattene (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 351-354 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; dibromotriblattene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009538321507
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  • 42
    Digitale Medien
    Digitale Medien
    Synthesis, crystal structure, and molecular modeling (AM1) of Methyl 6-chloro-4-(2-chlorophenyl)-5-formyl-2-methyl-1, 4-dihydropyridine-3-carboxylate (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 237-243 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; AM1 ; x-ray diffraction ; dihydropiridines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The synthesis and structural characterization of Methyl 6-chloro-4-(2-chlorophenyl)-5-formyl-2-methyl-1,4-dihydropyridine-3-carboxylate is described. The structure was refined to R1 = 0.0470 for 2665 reflections (with I 〉 2σ(I)). Crystal data: C15H13C12NO3, monoclinic,space group P21/c, a = 11.163(9), b = 14.484(8), c = 9.422(7) Å, V = 1512.9(19) Å3, Z = 4. The results of crystallographic and molecular modeling (AM1) were compared. The Cl atom attached to the phenyl group has two possible orientations, having 75% (sp) and 25% (ap) occupancy, respectively. The molecules in the crystal are held together by means of intermolecular hydrogen bonds of the type N=H...O and by C=H...O interactions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009539005669
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  • 43
    Digitale Medien
    Digitale Medien
    Synthesis and crystal structure of a tetranuclear manganese(IV) cluster [L4Mn4O6](ClO4)4·2H2O (L = 1,4,7-triazacyclononane) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 251-254 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; manganese(IV) cluster ; adamantane-shaped complex ; tetranuclear complex
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A tetranuclear manganese (IV) complex, [L4Mn4O6](ClO4)4·2H2O (1), with 1,4,7-triazacyclononane (L) as the capping ligands, has been synthesized and characterized by X-ray diffraction; monoclinic, space group P21/n with a = 21.335(6) Å, b = 11.387(3) Å, c = 21.788 (6) Å, β = 111.410 (6)°, V = 4928 (2) Å, Z = 4. Each manganese atom has a distorted octahedral environment comprised of three facially coordinated amine nitrogen atoms and three oxygen atoms, and the cation is an idealized tetrahedron. The Mn4O6 4+ cation corresponds to an adamantane skeleton.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009543106577
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  • 44
    Digitale Medien
    Digitale Medien
    Structure of a C2-symmetric bis(benzyloxy)trishomocubanone (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 747-750 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; trishomocubanone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01670329
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  • 45
    Digitale Medien
    Digitale Medien
    Crystal structure of ethyl 4-methylthio-3-phenyl-2-thioxo-2,3-dihydro-1,3-oxazole-5-carboxylate (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 237-240 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; 1,3-oxazoline-2-thione ; resonance structures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665176
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  • 46
    Digitale Medien
    Digitale Medien
    Synthesis and structure ofexo-11-cyano-endo-11-(trimethylsilyloxy)pentacyclo[5.4.0.02,6.03,10.05,9]undecan-8-one (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 267-271 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; pentacycloundecan-8-one ; pentacycloundecane-8,11-dione
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665182
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  • 47
    Digitale Medien
    Digitale Medien
    Structure of the product formed via Cu(I)-promoted oxidative dimerization ofexo-8-ethynylpentacyclo[5.4.0.02,6.03,10.05.9]undecan-endo-8-ol (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 543-547 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; diyne ; oxidative dimerization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01667022
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  • 48
    Digitale Medien
    Digitale Medien
    Crystal structure oftrans-tetrachlorobis[2-(2-1H-imidazolyl)-1H-imidazolium]cadmium(II), [Cd(H3biim)2Cl4] (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 695-699 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; 2,2'-bi-1H-imidazole ; cadmium chloride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01991966
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  • 49
    Digitale Medien
    Digitale Medien
    X-ray structures of two methoxybenzo[b]thiophenes (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 801-806 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; centrosymmetric ; methoxybenzo[b]thiophene ; estrogen receptor ; tubulin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01670312
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  • 50
    Digitale Medien
    Digitale Medien
    Reaction of vinylmagnesium bromide with hexacyclo[10.2.1.02,11.04,9.04,14.09,13]pentadeca-5,7-diene-3,10-dione: Transannular hemiketal formation (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 429-433 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; hexacyclopentadeca-5,7-diene-3,10-dione
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01665824
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  • 51
    Digitale Medien
    Digitale Medien
    The crystal and molecular structure of 6,8,15,16b,16c,17-hexahydro-16b,16c-diphenyl-7H,16H-6a,7a,15a,16a-tetraazanaphtho[5,6]azulano[2,1,8-ij]naptho[f]azulene-7,16-dione (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 365-368 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; receptor ; clip shaped molecule
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01677102
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  • 52
    Digitale Medien
    Digitale Medien
    Synthesis and X-ray analysis of 1-((1S)-phenylethyl)-azetidine-(2R)-piperidinamide (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 639-642 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; chiral auxiliaries
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01668624
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  • 53
    Digitale Medien
    Digitale Medien
    Crystal structures of two 1,2-bis-(1-aryl-3-methyltriazene-3-yl-)ethanes with aryl substituents of opposite polarity (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 5-10 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; triazene ; bis-triazene ; nitrile substituent ; methoxy substituent ; hydrogen bonding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021714316063
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  • 54
    Digitale Medien
    Digitale Medien
    Crystal structures of the hydrated disodium and paraquat salts of 1,8-disulfonato-3,4,5,6-acridinetetracarboxylic acid (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 39-46 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; 1,8-disulfonato-3,4,5,6-acridinetetracarboxylic acid ; 3,4,5,6-tetracarboxyacridine-1,8-disulfonate ; paraquat ; hydrate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021726618789
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  • 55
    Digitale Medien
    Digitale Medien
    Crystal structures of four dibromomethylene-functionalized cage compounds (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 259-266 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; heptacyclotetradecane ; hexacyclotetradecane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021845118189
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  • 56
    Digitale Medien
    Digitale Medien
    A dinuclear cyano-bridged complex based on hexacyanoferrate(III) and samarium(III) nitrate: synthesis and crystal structure (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 303-307 
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    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; samarium(III) complexes ; iron(III) complexes ; cyanide-bridges ; dinuclear complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021857420915
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  • 57
    Digitale Medien
    Digitale Medien
    Gold(III)-pteridine compounds: synthesis, spectral, and X-ray diffraction studies on new adducts between sodium tetrabromoaurate(III) and lumazine derivatives (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 565-570 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; complexes ; pteridine ; lumazine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023252324268
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  • 58
    Digitale Medien
    Digitale Medien
    Molecular structure of AlH3[N(CH2CH2)3CH]2 (1998)
    Springer
    Journal of chemical crystallography 28 (1998), S. 649-651 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; aluminum ; hydride ; complex ; quinuclidine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022473312315
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  • 59
    Digitale Medien
    Digitale Medien
    Synthesis and crystal structure of a new lithium cyclohexaphosphate hydrate: Li6P6O18·10H2O (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 323-327 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; cyclohexaphosphate ; hydrate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009577902852
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  • 60
    Digitale Medien
    Digitale Medien
    Synthesis and structure of a bis(ethynyl)-substituted oxahexacyclic cage ether (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 347-349 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; pentacycloundecane ; triple bonds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009586204669
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  • 61
    Digitale Medien
    Digitale Medien
    A cobalt(II) complex with the N,N,O-tridentate ligand 6-amino-5-formyl-1,3-dimethyluracilato-benzoyl-hydrazone (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 283-286 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; complexes ; cobalt ; benzoylhydrazone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009565600126
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  • 62
    Digitale Medien
    Digitale Medien
    Synthesis and crystal structure of 4,4′-bis(4-pyridylethyl)biphenyl, noncovalently hydrogen bonded two-dimensional networks (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 641-646 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; hydrogen bonds ; 1H and 13C NMR ; FTIR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A new pyridine containing compound, 4,4′-bis(4-pyridylethyl)biphenyl 1, was synthesized and its structure was determined by X-ray crystallography. Two kinds of two-dimensional networks linked by hydrogen bonds were obtained with different crystal solvents: 1·2H2O, monoclinic, space group P21/n with a = 8.3280(10), b = 5.5990(10), c = 24.054(4) Å, β = 98.79(2)°, V = 1108.4(3) Å3, Z = 2, Dc = 1.200 g cm−3, R1 = 0.0558; 1·CH3OH·2H2O, triclinic, space group P-1 with a = 8.3310(10), b = 12.861(2), c = 13.111(2) Å, α = 64.110(10), β = 75.000(10), γ = 83.750(10)°, V = 1220.7(3) Å3, Z = 2, Dc = 1.177 g cm−3, R1 = 0.0529. It is interesting that in the hydrate the host molecule of 1 contains an essentially flat biphenyl section, while in the methanol complex the host molecule of 1 contains a substantial twist in the center of the biphenyl section. The compounds were also characterized by NMR and FTIR spectroscopies. The 1H and 13C NMR assignments for 1 were carried out by 2D NMR spectral measurements in acetonitrile-d 3.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011944115181
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  • 63
    Digitale Medien
    Digitale Medien
    X-ray crystal structures of [HB(3,4,5-Me3pz)3[2Zn, [H2B(3,4,5-Me3pz)2]Zn(μ-3,4,5-Me3pz)2Zn[H2B(3,4,5-Me3pz)2], and [H2B(pz)2]2Zn (pz = pyrazolyl ring) (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 665-670 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; poly(pyrazolyl)borate ligands ; zinc(II)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract [HB(3,4,5-Me3pz)3]2Zn (1) and [H2B(3,4,5-Me3pz)2]Zn(μ-3,4,5-Me3pz)2Zn[H2B(3,4,5-Me3pz)2] (2) are present in equal amounts in a crystal in the triclinic space group, P-1 with a = 11.5924(11) Å, b = 12.7799(12) Å, c = 15.7317(14) Å α = 107.905(2)° β = 96.796(2)°, γ = 105.786(2)°, and Z = 1. The structure of 1 is a trigonally distorted octahedron and is very similar to the structure of [HB(3,5-Me2pz)3]2Zn showing that the introduction of the third methyl group on the pyrazolyl ring does not impact on structure. [H2B(pz)2]2Zn (3) is orthorhombic, Pca2(1) with a = 10.1473(3) Å, b = 11.1117(2) Å, c = 14.1831(5) Å, α = β = γ = 90° and Z = 4. The zinc(II) centers in both 2 and 3 are similar and have pseudotetrahedral structures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011900300160
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  • 64
    Digitale Medien
    Digitale Medien
    Structure and properties of cobalt(II) complex with a tetraaza macrocycle containing 2-pyridylmethyl pendant arms (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 335-338 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; cobalt(II) complex ; tetraaza macrocycle ; 2-pyridylmethyl pendant arms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The complex [Co(L)]Cl2·10H2O (1) (L = 2,13,-bis(2-pyridylmethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane) has been synthesized and structurally characterized. Compound 1 crystallizes in the triclinic system, space group P-1 with a = 9.731(2) Å, b = 9.789(2) Å, c = 11.998(1) Å, α = 66.66(1)°, β = 76.95(1)°, γ = 87.99(2)°, V = 1020.4(3) Å3, and Z = 1. The crystal structure of 1 shows that the complex is centrosymmetric and the cobalt(II) ion has a slightly distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendent arms at the axial positions. Cyclic voltammetry for 1 undergoes reversible one-electron oxidation to the Co(III) and irreversible one-electron reduction to the Co(I).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009513308611
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  • 65
    Digitale Medien
    Digitale Medien
    Crystal structure of 2,3-dihydronaphto[2,3-b) [1,5] dioxepin (2000)
    Springer
    Journal of chemical crystallography 30 (2000), S. 459-462 
    Details
    ISSN: 1572-8854
    Schlagwort(e): Crystal structure ; chemical synthesis ; 2,3-dihydronaphto[2,3-b] [1,5) dioxepin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The X-ray single crystal structure of C13H12O2 compound was determined. It crystallizes in the orthorombic space group P212121 with a = 7.8847(7), b = 9.639(1), c = 13.432(2) Å, Z = 4 and V = 1020.8(3) Å3. The final R converged to 0.037 for 1763 independent reflexions. The title compound forms layers parallel to (1 0 0) planes and the three dimensional cohesion of the crystal is assumed by Van der Waals interactions. The molecule consists of two six-membered rings (A and B) and a seven-membered ring (C). A and B rings are planar, whereas the C ring has a chair conformation
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011399416154
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  • 66
    Digitale Medien
    Digitale Medien
    Physical processes in an Indian Ocean atoll (1998)
    Springer
    Coral reefs 17 (1998), S. 155-168 
    Details
    ISSN: 1432-0975
    Schlagwort(e): Key words Atoll hydrodynamics ; Lagoon ciculation ; Wave transformation ; Currents ; Physical processes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract  Detailed measurements of water levels, and tide and wave-induced currents were undertaken to examine physical processes and their relationship with morphology in the Cocos (Keeling) Islands, a medium sized atoll in the Indian Ocean. Results indicate that the atoll structure controls both lagoon circulation and the spatial pattern of energy distribution. Lagoon circulation is tide dominated (currents 16–31 cms-1) with flushing (2–5 days) of the lagoon occurring through the deep leeward passages. Wave- and tide-driven unidirectional flows through shallow passages (26–65 cms-1) are important mechanisms of ocean to lagoon water exchange and contribute up to 24% of the lagoon neap tide prism. Reef flats are dominated by wave energy (maximum velocity 140 cms-1, east) with measurements of the attenuation of wave energy between reef flats and shallow lagoon (80–90%) conforming to measurements from fringing and barrier reefs. Spectral analysis shows that the characteristics of wave energy vary on different sectors of the atoll, with gravity wave energy dominating the east, and infragravity wave energy dominating the southern reef flat and passages. Wave setup at the reef crest is considered to be responsible for an identified 0.1 m higher water level in the southern as opposed to eastern and northern atoll, which promotes higher reef flat growth. Transmission of gravity waves across reef flats requires threshold water depths of 0.65 (east) and 0.70 m (south). The higher southern reef is an effective filter of gravity wave energy for most tidal elevations. Differences in the type and magnitude of physical processes within the atoll are discussed with relation to geomorphic development on Cocos.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003380050110
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  • 67
    Digitale Medien
    Digitale Medien
    Late Pleistocene and Holocene lake fluctuations in the Sevier Lake basin, Utah, USA (1988)
    Springer
    Journal of paleolimnology 1 (1988), S. 9-21 
    Details
    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; Sevier Lake ; Great Basin ; western United States ; Lake Bonneville
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Sevier Lake is the modern lake in the topographically closed Sevier Lake basin, and is fed primarily by the Sevier River. During the last 12 000 years, the Beaver River also was a major tributary to the lake. Lake Bonneville occupied the Sevier Desert until late in its regressive phase when it dropped to the Old River Bed threshold, which is the low point on the drainage divide between the Sevier Lake basin and the Great Salt Lake basin. Lake Gunnison, a shallow freshwater lake at 1390 m in the Sevier Desert, overflowed continuously from about 12 000 to 10 000 yr B.P., into the saline lake in the Great Salt Lake basin, which continued to contract. This contrast in hydrologic histories between the two basins may have been caused by a northward shift of monsoon circulation into the Sevier Lake basin, but not as far north as the Great Salt Lake basin. Increased summer precipitation and cloudiness could have kept the Sevier Lake basin relatively wet. By shortly after 10 000 yr B.P. Lake Gunnison had stopped overflowing and the Sevier and Beaver Rivers had begun depositing fine-grained alluvium across the lake bed. Sevier Lake remained at an altitude below 1381 m during the early and middle Holocene. Between 3000 and 2000 yr B.P. the lake expanded slightly to an altitude of about 1382.3 m. A second expansion, probably in the last 500 years, culminated at about 1379.8 m. In the mid 1800s the lake had a surface altitude of 1379.5 m. Sevier Lake was essentially dry (1376 m) from 1880 until 1982. In 1984–1985 the lake expanded to a 20th-century high of 1378.9 m in response to abnormally high snow-melt runoff in the Sevier River. The late Holocene high stands of Sevier Lake were most likely related to increased precipitation derived from westerly air masses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00202190
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  • 68
    Digitale Medien
    Digitale Medien
    Paleolimnological reconstruction of recent changes in assemblages of Cladocera from acidified lakes in the Adirondack Mountains (New York) (1994)
    Springer
    Journal of paleolimnology 11 (1994), S. 189-200 
    Details
    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; lake acidification ; Cladocera ; Chydoridae ; Adirondack Mountains
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Remains of Cladocera were examined in short sediment cores from three Adirondack lakes with mean pHs below 5 and a fourth with a mean pH of 6.5. These cores were collected as part of the Paleoecological Investigation of Recent Lake Acidification (PIRLA I) project. Historical and paleolimnological evidence suggests that pH has decreased in each of the acid lakes in recent decades. In all of the study cores, the greatest changes in net accumulation rates, assemblage composition, and species richness occurred in recently deposited sediments. The similar timing of events in all lakes suggests that a regional disturbance was responsible. In the three acid lakes, there was a strong association of changes in cladoceran assemblages and diatom, chrysophyte, and geochemical evidence of acidification. The occurrence of recent changes in non-acid Windfall Pond indicates that other factors may also have affected Cladocera in the study lakes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00686865
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  • 69
    Digitale Medien
    Digitale Medien
    A new method for the determination of absolute abundance of diatoms and other silt-sized sedimentary particles (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 171-179 
    Details
    ISSN: 1573-0417
    Schlagwort(e): diatoms ; methods ; absolute abundance ; microfossils ; paleolimnology ; paleoceanography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract The determination of absolute abundances of diatoms in paleolimnological and paleoceanographic studies is now becoming a routine step in diatom paleoecological investigations. Several distinct methods have been described for establishing absolute diatom abundance. Each of these methods has its own strengths and weaknesses. The most common weakness in diatom preparation methods is the use of aliquot subsampling from an assumed ‘well-mixed’ diatom suspension. Described here is a simple, efficient and inexpensive method that utilizes settling of diatoms through a 10 cm water column, which yields an effectively random distribution, and uses no aliquot subsampling. Only a few milligrams of sample are needed, permitting microstratigraphic analysis of, for example, individual varves. The method is shown to be both reproducible and accurate for sediments ranging in diatom concentration from less than 10 million to more than one billion diatoms per gram. Multiple slides or SEM stubs can be simultaneously prepared. The method works well for the analysis of most silt-sized microfossils or other sedimentary particles.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00678093
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  • 70
    Digitale Medien
    Digitale Medien
    Diatom-salinity relationships in 111 lakes from the Interior Plateau of British Columbia, Canada: the development of diatom-based models for paleosalinity reconstructions (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 197-221 
    Details
    ISSN: 1573-0417
    Schlagwort(e): diatoms ; paleolimnology ; paleoclimatology ; salinity ; athalassic ; British Columbia ; CCA ; transfer function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Diatoms were identified and enumerated from the surface sediments of 111 lakes, 45 from the Kamloops region and 66 from the Cariboo/Chilcotin region, located on the southern Interior Plateau of British Columbia, Canada. This paper is an extension of another study which investigated the relationship of diatoms to salinity and ionic composition in 65 lakes from the Cariboo/Chilcotin region. The 111 lakes spanned a large gradient in salinity, ranging from fresh through hypersaline (late-summer salinity values ranged from 0.04 to 369 g l−1), and included both carbonate- and sulphate-dominated lakes with sodium and magnesium as the dominant cations. The Kamloops region had more sulphate-dominated, hypersaline lakes and fewer carbonate-rich lakes than the Cariboo/Chilcotin region. Most lakes had higher salinities in the late-summer compared to the spring. Both salinity and brine-type were important variables that could explain the different diatom assemblages present in the lakes. The majority of diatom taxa had salinity optima in the freshwater to subsaline range (〈3 g l−1), and the taxa displayed a range of both narrow and broad tolerances along the salinity gradient. Weighted-averaging regression and calibration, and maximum likelihood techniques were used to develop salinity inference models from the diatom assemblages based on their relationship to the spring, late-summer and average lakewater salinity measurements. Simple weighted-averaging (WA) models generally produced the same or lower bootstrapped RMSEs of prediction than weighted-averaging with tolerance downweighting (WA(tol)) in the two regional and the combined datasets. Weighted averaging partial least squares (WA-PLS) showed little or no improvement in the predictive abilities of the datasets, as judged by the jackknifed RMSE of prediction. In all cases, the combined dataset of 102 lakes performed better than either of the smaller regional datasets, with relatively little difference between spring, average and late-summer salinity models. The maximum likelihood models gave lower apparent RMSEs of prediction in comparison to other methods; however, independent validation of this technique using methods such as bootstrapping were not undertaken because of the computer intensive nature of such analyses. These diatom-based salinity models are now available for reconstructing salinity and climatic trends from appropriately chosen closed-basin lakes in the Interior region of British Columbia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00678021
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  • 71
    Digitale Medien
    Digitale Medien
    A Holocene paleoenvironmental history of Lake Alexandria, South Australia (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 259-268 
    Details
    ISSN: 1573-0417
    Schlagwort(e): sediments ; 14C ; 210Pb ; diatoms ; geochemical analyses ; coastal paleoenvironments ; paleolimnology ; Nodularia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract An investigation of Holocene sediments within Lake Alexandrina, a shallow coastal lake at the mouth of the Murray River, South Australia, is presented based on a multidisciplinary approach.14C and210Pb radiometric dating methods are used to establish a geochronological framework for the last 7000 yr BP, and diatoms, sand-siltclay ratios, organic carbon, phosphorus and copper concentrations are used to infer paleoenvironmental changes. The diatom assemblages indicate a change from marine-brackish to oligosaline-freshwater conditions between 7000 and 6000 yr BP, with sea-level stabilisation and continuous barrier formation across the Murray mouth. Sand pulses after 2300 yr BP document sand spit formation in the lake and the commencement of extensive lacustrine sedimentation. In the past 100 years which include the advent of European settlement in the region, the short-term210Pb-based mass accumulation rate of 0.063 g cm−2 yr−1 is greater than that of the longer-term mean14C-based rate (0.023 g cm−2 yr−1), and high concentrations of phosphorus and copper correspond to historical records of blue-green algal blooms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00678024
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  • 72
    Digitale Medien
    Digitale Medien
    Paleohydrology and paleochemistry of Lake Manitoba, Canada: the isotope and ostracode records (1994)
    Springer
    Journal of paleolimnology 12 (1994), S. 269-282 
    Details
    ISSN: 1573-0417
    Schlagwort(e): Great Plains ; western Canada ; magnesian calcite ; Holocene ; paleolimnology ; stable isotopes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Lake Manitoba, the largest lake in the Prairie region of North America, contains a fine-grained sequence of late Pleistocene and Holocene sediment that documents a complex postglacial history. This record indicates that differential isostatic rebound and changing climate have interacted with varying drainage basin size and hydrologic budget to create significant variations in lake level and limnological conditions. During the initial depositional period in the basin, the Lake Agassiz phase (∼12–9 ka), δ18O of ostracodes ranged from −16‰ to −5‰ (PDB), implying the lake was variously dominated by cold, dilute glacial meltwater and warm to cold, slightly saline water.Candona subtriangulata, which prefers cold, dilute water, dominates the most negative δ18O intervals, when the basin was part of proglacial Lake Agassiz. At times during this early phase, the δ18O of the lake abruptly shifted to higher values; euryhaline taxa such asC. rawsoni orLimnocythere ceriotuberosa, and halobiont taxa such asL. staplini orL. sappaensis are dominant in these intervals. This positive covariance of isotope and ostracode records implies that the lake level episodically fell, isolating the Lake Manitoba basin from the main glacial lake. δ18O values from inorganic endogenic Mg-calcite in the post-Agassiz phase of Lake Manitoba trend from −4‰ at 8 ka to −11‰ at 4.5 ka. We interpret that this trend indicates a gradually increasing influence of isotopically low (−20‰ SMOW) Paleozoic groundwater inflow, although periods of increased evaporation during this time may account for zones of less negative isotopic values. The δ18O of this inorganic calcite abruptly shifts to higher values (−6‰) after ∼4.5 ka due to the combined effects of increased evaporative enrichment in a closed basin lake and the increased contribution of isotopically high surface water inflow on the hydrologic budget. After ∼2 ka, the δ18O of the Mg-calcite fluctuates between −13‰ and −7‰, implying short-term variability in the lake's hydrologic budget, with values indicating the lake varied from outflow-dominated to evaporation-dominated. The δ13C values of Mg-calcite remain nearly constant from 8 to 4.5 ka and then trend to higher values upward in the section. This pattern suggests primary productivity in the lake was initially constant but gradually increased after 4.5 ka.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00678025
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  • 73
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    Digitale Medien
    Paleolimnological analysis of Ullswater using testate amoebae (1995)
    Springer
    Journal of paleolimnology 13 (1995), S. 51-63 
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    ISSN: 1573-0417
    Schlagwort(e): acidification ; England ; Holocene ; Lake District ; paleolimnology ; testate amoebae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Tests of testate amoebae extracted from samples of bottom sediments from 33 tarns in the English Lake District reveal a relationship between their distribution and physical-chemical parameters of the tarn waters.Nebela and several species ofDifflugia appear to prefer more acidic conditions, i.e., pH less than 6.2, while others such asCentropyxis, Lesquereusia and some species ofCyclopyxis andDifflugia are more common in lakes with pH's above that value. Using these data, and inferring rates of sedimentation from the densities of tests found in a 6-m core, a paleolimnological history for the past 11 000 years is presented for Ullswater (English Lake District). The record of testate amoebae, beginning shortly after deglaciation, depicts an uneven increase in acidity and a history of episodes of rapid and slow deposition that correlate reasonably well with paleoclimatological changes and anthropogenic alterations in the catchment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00678110
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  • 74
    Digitale Medien
    Digitale Medien
    Late holocene paleoclimatic and paleobiologic records from sediments of Devils Lake, North Dakota (1995)
    Springer
    Journal of paleolimnology 13 (1995), S. 193-207 
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    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; lake levels ; biogenic silica ; organic matter ; isotopes ; North Dakota
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract An 84 cm sediment core collected from the center of Devils Lake, North Dakota, was analyzed at 1-cm intervals for,210Pb,137Cs, sediment conductivity, the concentrations of, biogenic silica, total organic carbon, carbon to nitrogen ratio, and the carbon and nitrogen isotopic composition of the organic fraction. Variations in210Pb activities in the upper 20 centimeters indicate that sediment accumulations rates in Devils Lake are not constant, and that accumulation rates were highest during periods of high lake level. The mean sedimentation accumulation rate was calculated as 0.24 cm−1 yr. The137Cs profile is characterized by near-surface maximum concentrations, possibly the result of redistribution of137Cs during salinity excursions. Biogenic silica is strongly correlated to lake level in Devils Lake. Periods of low lake level (characterized by high sediment conductivity) correspond to low biogenic silica concentrations. The trends in biogenic silica are attributed to variations in diatom productivity in the lake and to variations in sediment accumulation rates. Based on biogenic silica content and the composition of organic matter in the sediment (total organic carbon, carbon:nitrogen ratio and the δ13C and δ15N composition of total organic matter), paleobiologic conditions of Devils Lake during low lake stands were characterized by, (1) decreased primary productivity, (2) decreased input of detrital organic matter, and (3) increased nitrogen availability. During the 350 years of sediment accumulation represented by the 84-cm sediment core Devils Lake has experienced two periods of sustained high lake level; one between about 130 and 170 years ago (1820 to 1860 A.D.) and the second between 270 and 310 years ago (1680 to 1720 A.D.). Devils Lake experienced a period of intense drying about 260 years ago (1720 A.D.).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00682764
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  • 75
    Digitale Medien
    Digitale Medien
    Diatom succession in an urban reservoir system (1996)
    Springer
    Journal of paleolimnology 15 (1996), S. 237-243 
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    ISSN: 1573-0417
    Schlagwort(e): reservoir ; diatom ; core ; sediments ; hydrology ; paleolimnology ; eutrophication
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract A 43 cm by 5 cm diameter sediment core sample was obtained from Ford Lake reservoir in Washtenaw County, Michigan, and sectioned at 1 cm intervals. The purpose of this study was to determine whether diatom communities in this reservoir have undergone quantifiable changes in abundance and composition since its creation. Thirty-one cm of this core appeared to represent material deposited since the creation of the reservoir based on changes in diatom abundance, the physical composition of the sediment and the change in biogenic SiO2 concentration. Fortyseven species of diatoms were identified total concentrations of diatom remains varied from 1×104 g-1 to 1×107 g-1. Prior to the establishment of the reservoir, the diatom flora was dominated by benthic taxa. Benthic diatoms were numerous throughout the entire core, but eutrophic taxa (e.g., Aulacoseira italica, Aulacoseira granulata, Stephanodiscus niagarae, Fragilaria crotonensis) dominated much of the core after the reservoir's creation. Total diatom density increased about tenfold in the about the first 10–15 years after the reservoir's creation before declining markedly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00213043
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  • 76
    Digitale Medien
    Digitale Medien
    Siliceous microfossil distribution in the surficial sediments of Lake Baikal (1995)
    Springer
    Journal of paleolimnology 14 (1995), S. 69-82 
    Details
    ISSN: 1573-0417
    Schlagwort(e): Russia ; Lake Baikal ; paleolimnology ; diatoms ; stomatocysts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Examination of surficial sediments at 16 stations shows minor, but consistent differences in the numbers and kinds of siliceous microfossils deposited in different regions of Lake Baikal. There is a general north-south decreasing trend in total microfossil abundance on a weight basis. Endemic plankton diatom species are the most abundant component of assemblages at all stations. Chrysophyte cysts are present at all stations, but most forms are more abundant at northern stations. Non-endemic plankton diatom species are most abundant at southern stations. Small numbers of benthic diatoms and sponge spicules are found in all samples. Although low numbers are present in offshore sediments, the benthic diatom flora is very diverse. Principal components analysis confirms primary north-south abundance trends and suggests further differentiation by station location and depth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00682594
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  • 77
    Digitale Medien
    Digitale Medien
    Temporal variations of fossil Cladocera in the sediments of Lake Orta (N. Italy) over the last 400 years (1995)
    Springer
    Journal of paleolimnology 14 (1995), S. 113-122 
    Details
    ISSN: 1573-0417
    Schlagwort(e): Cladocera remains ; paleolimnology ; climate ; pollution ; human impact ; Italy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract We use Cladocera remains in the sediments to reconstruct the longterm history of Lake Orta, a lake which experienced severe pollution from copper and ammonium sulphate, and started to recover during the last 15 years. Both human and natural impacts were detected over almost 400 years. Pollution was manifested by a dramatic decrease in the number of remains, in the planktonic/littoral (P/L) ratio, and in chydorid species diversity. Most species, even those most tolerant to stress, disappeared. The recolonization of biota was initially sustained by one species of chydorid,Chydorus sphaericus, which had a three-fold increase at the beginning of the 1980s, when studies on plankton recorded the development of a pelagic population. This fact, and the appearance in the sediments ofAlona quadrangularis, attest to the development of filamentous algae which was reported in studies on the plankton. The colonization of the lake by pelagic species came only in the last twelve years and was manifested also as a stabilization of the P/L ratio. Two other periods of disturbance were detected in the sediments: the first, at the end of the 19th century, was related to the introduction of exotic fish species; the second occurred during the second half of the 17th century. This event probably cannot be ascribed to human impact, but may be related to a decrease in temperature in that period (the Maunder Minimum).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00735477
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  • 78
    Digitale Medien
    Digitale Medien
    Late Holocene lake-level and lake development signals in Lower Herring Lake, Michigan (1996)
    Springer
    Journal of paleolimnology 15 (1996), S. 19-45 
    Details
    ISSN: 1573-0417
    Schlagwort(e): diatoms ; grain-size analysis ; lake-level changes ; Lake Michigan ; paleolimnology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Paleolimnological investigations of a marginal lake in the Lake Michigan basin revealed signals of long-term lake-level changes primarily controlled by climatic forces. Multiple analyses identified concurrent signals in sediment chemistry, grain size, and the microfossil record. Coarse-grained sediments, benthic diatoms, and nutrient response species increased as lake levels rose or fell. Finer sediments and higher percentages of taxa associated with stable thermocline conditions occurred during high-lake periods. Sedimentary evidence revealed corresponding strong high-lake signals c. 2500–2200, 1800–1500, 1170–730, and 500–280 BP. Low-lake periods occurred c. 1500–1170 and 700–500 B.P. An additional signal of lake-level decline was apparent beginning c. 280 BP but was interrupted by anthropogenic effects. Evidence of extreme low-lake levels (c. 1400–1300 BP), and signals for a medieval warming period (1030–910 BP) and the Maunder minimum (370–325 BP) indicate occurrence of short-lived dry climatic conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00176988
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  • 79
    Digitale Medien
    Digitale Medien
    A multi-proxy study of Holocene environmental change in the Maya Lowlands of Peten, Guatemala (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 139-159 
    Details
    ISSN: 1573-0417
    Schlagwort(e): geochemistry ; Guatemala ; Holocene ; lakesediment ; Maya ; magnetic susceptibility ; paleolimnology ; pollen ; stable isotopes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract We used multiple variables in a sediment core from Lake Peten-Itza, Peten, Guatemala, to infer Holocene climate change and human influence on the regional environment. Multiple proxies including pollen, stable isotope geochemistry, elemental composition, and magnetic susceptibility in samples from the same core allow differentiation of natural versus anthropogenic environmental changes. Core chronology is based on AMS 14C measurement of terrestrial wood and charcoal and thus avoids the vagaries of hard-water-lake error. During the earliest Holocene, prior to ∼9000 14C yr BP, the coring site was not covered by water and all proxies suggest that climatic conditions were relatively dry. Water covered the coring site by ∼9000 14C yr BP, coinciding with filling of other lakes in Peten and farther north on the Yucatan Peninsula. During the early Holocene (∼9000 to ∼6800 14C yr BP), pollen data suggest moist conditions, but high δ 18O values are indicative of relatively high E/P. This apparent discrepancy may be due to a greater fractional loss of the lake's water budget to evaporation during the early stages of lake filling. Nonetheless, conditions were moist enough to support semi-deciduous lowland forest. Decrease in δ 18O values and associated change in ostracod species at ∼6800 14C yr BP suggest a transition to even moister conditions. Decline in lowland forest taxa beginning ∼5780 14C yr BP may indicate early human disturbance. By ∼2800 14C yr BP, Maya impact on the environment is documented by accelerated forest clearance and associated soil erosion. Multiple proxies indicate forest recovery and soil stabilization beginning ∼1100 to 1000 14C yr BP, following the collapse of Classic Maya civilization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007968508262
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  • 80
    Digitale Medien
    Digitale Medien
    A preliminary investigation of siliceous microfossil succession in late Quaternary sediments from Lake Baikal, Siberia (1997)
    Springer
    Journal of paleolimnology 18 (1997), S. 189-206 
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    ISSN: 1573-0417
    Schlagwort(e): Lake Baikal ; Russia ; paleolimnology ; diatoms ; chrysophyte cysts ; climate change
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Siliceous microfossil assemblage succession was analyzed in a 100 m sediment core from Lake Baikal, Siberia. The core was recovered from the lake's central basin at a water depth of 365 m. Microfossil abundance varied greatly within the intervals sampled, ranging from samples devoid of siliceous microfossils to samples with up to 3.49 × 1011 microfossils g-1 sediment. Fluctuations in abundance appear to reflect trends in the marine δ18O record, with peak microfossil levels generally representing climate optima. Microfossil taxa present in sampled intervals changed considerably with core depth. Within each sample a small number of endemic diatom species dominated the assemblage. Changes in dominant endemic taxa between sampled intervals ranged from extirpation of some taxa, to shifts in quantitative abundance. Differences in microfossil composition and the association of variations in abundance with climate fluctuations suggest rapid speciation in response to major climatic excursions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007924310688
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  • 81
    Digitale Medien
    Digitale Medien
    On diatom concentrations in lake sediments: results from an inter-laboratory comparison and other tests performed on a uniform sample (1997)
    Springer
    Journal of paleolimnology 18 (1997), S. 261-268 
    Details
    ISSN: 1573-0417
    Schlagwort(e): diatoms ; microfossil concentrations ; methods ; paleolimnology ; West Okoboji Lake ; Iowa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract The diatom concentration of a uniform lake sediment sample was estimated in 15 laboratories. Whilst 21 of 35 estimates were between 13 and 19 × 107 valves g-1, values ranged from 8.2 × 106 to 2.0 × 109 valves g-1. However, counts from replicate sediment digestions, replicate slide preparations from a single digested slurry, and multiple counts from an individual slide all yielded internally consistent results, with acceptably low coefficients of variation (±4.5–6.3%). Without greater efforts towards harmonization, for example by calibrating techniques to a standard of known concentration, reported diatom concentration values, as well as derived data such as diatom accumulation rates, are not directly comparable between most laboratories. This sharply contrasts the strong reproducibility of diatom relative frequency data. A calibration exercise, using the Eucalyptus pollen spike technique to estimate a known concentration of Lycopodium spores, demonstrates that this method performs best when approximately equal proportions of microfossils and introduced markers are counted.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007937300347
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  • 82
    Digitale Medien
    Digitale Medien
    A summary of past and recent plankton of Lake Winnipeg, Canada using algal fossil remains (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 297-307 
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    ISSN: 1573-0417
    Schlagwort(e): eutrophication ; algae ; bluegreen akinetes ; non-siliceousmicro fossils ; diatoms ; paleolimnology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Although the phytoplankton and protozoan assemblages of Lake Winnipeg are quite variable both, spatial and temporally, knowledge of their current distribution and ecology enables them to be used as indicators providing unique information concerning past and recent ecosystem conditions. Many of the main taxa have been similar throughout history although there have been dramatic changes in their abundance. Lake Winnipeg is currently very responsive to the climatic conditions in its drainage basin and it appears, historically, to have been a diatom-bluegreen algal lake with Tintinnids and thecate amoeba forming significant components of the protozoan community. A wide variety of microfossil remains have been used to infer past conditions in this large prairie lake. Microfossils reported from the long core 103 (8 m) taken from the north basin of LakeWinnipeg and short core Namao 7a taken from the south basin of the lake in August 1994 indicate that the lake has experienced several changes over its history. Diatom assemblages, low throughout the core 103 below 50 cm, except for a peak around 300–400 cm are virtually absent below 690–800 cm (Lake Agassiz). Stephanodiscus and Aulacoseira are the two major pelagic diatom genera represented throughout the lake's history. Species changes occur near the top of the core indicate increased anthropogenic eutrophication. Shallow water littoral taxa were never abundant at either coring sites. The presence of planktic cyanoprokaryote (cyanophyte, cyanobacteria, bluegreen algae) remains (akinetes) from 600 cm depth and the progressive increase in abundance from 400 cm to through the top 100 cm of the core indicates increasing phosphorus levels, warming summer temperatures and increasing summer nitrogen limitation in the lake. Nitrogen fixing bluegreens (especially Anabaena and Aphanizomenon akinetes) and the diatoms (Aulacoseira ambigua, A. granulata, A. islandica, S. binderanus, and S. niagarae) were abundant in the upper sediments and changes after 100 cm can be interpreted as the effects of human impact. These taxa indicative of increase eutrophication, in addition to S. agassizensis, Melosira varians and Cyclostephanos dubius, are representative of present day plankton. The short core Namao 7a was dated by Pb210 and the fossil remains also show a rise in the Aulacoseira (particularly A. granulata and A. ambigua) and bluegreen akinetes in the last 40 years as was seen in the upper sediments of the 103 core. There was an interesting peak in chrysophyte cysts during the 1930's which corresponds nicely with climatic conditions during this period. The fires accompaning the hot dry period in the mid 70's can be seen in the dramatic rise in charcoal during this period. Multiple types of micro fossils remains provides several useful tools for interpreting past lacustrine conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007990217568
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  • 83
    Digitale Medien
    Digitale Medien
    A diatom-conductivity transfer function for Spanish salt lakes (1998)
    Springer
    Journal of paleolimnology 19 (1998), S. 399-416 
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    ISSN: 1573-0417
    Schlagwort(e): saline lakes ; paleolimnology ; paleoclimate ; diatoms ; transfer functions ; Spain ; CCA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Diatom-salinity transfer functions for interpretation of palaeosalinity and palaeoclimate change have been developed successfully for parts of North America and North and East Africa, but there is a need for data-sets in other saline lake regions of the world. A data-set of 74 modern diatom samples and associated water chemistry data is described from Spain. The influence of conductivity and other environmental variables on diatom distribution is explored using canonical correspondence analysis (CCA) and partial CCAs. A transfer function is derived for conductivity (70 samples) whose apparent predictive ability is high (apparent r2 = 0.91). Performance under jackknifing is poor due to the heterogeneous nature of the data-set and poor coverage of the freshwater end of the salinity gradient. There is a lack of suitable low-salinity sites in Spain, and the accuracy of estimated salinity optima and tolerance ranges may be improved by merging this data-set with those of other regions. The Spanish transfer function has strong affinities with the African data-set and contributes important ecological data for diatom taxa which are absent or poorly represented in the modern flora of African lakes, and for which, in fossil material, there were previously no good modern analogues.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007934627134
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  • 84
    Digitale Medien
    Digitale Medien
    Early postglacial chironomid succession in southwestern British Columbia, Canada, and its paleoenvironmental significance (1989)
    Springer
    Journal of paleolimnology 2 (1989), S. 1-14 
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    ISSN: 1573-0417
    Schlagwort(e): British Columbia ; chironomids ; Pacific Northwest ; paleoclimate ; paleolimnology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Chironomids typical of cold, well-oxygenated, oligotrophic environments are common in late-Pleistocene deposits, but these taxa are rare in Holocene sediments of most small temperate lakes. Hypotheses to explain the demise of these taxa include variations in climate, lake trophic state, lake levels, terrestrial vegetation, and/or sediment composition. In southwestern British Columbia, this demise correlates with palynological evidence for a lodgepole pine decline, and for rapid climatic amelioration, at about 10 000 yr B.P. Faunal changes are poorly correlated with lithological boundaries. The similar timing of the declines among lakes suggests that a regional influence, climate, has possibly been the principal determinant of early chironomid faunal succession.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00156979
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  • 85
    Digitale Medien
    Digitale Medien
    Paleolimnological significance of spinose and non-spinose morphs of Pyrgophorus hibbardi (Leonard and Franzen, 1944) (1998)
    Springer
    Journal of paleolimnology 20 (1998), S. 99-102 
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    ISSN: 1573-0417
    Schlagwort(e): Pliocene ; Oklahoma ; Pyrgophorus hibbardi ; paleolimnology ; stable isotopes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract The basal portion of the Ogallala Formation (=‘Laverne Formation’) (Lower Pliocene) Beaver County, Oklahoma, contains an interesting assemblage of non-marine fossil molluscs that include both spinose and non-spinose forms of the aquatic gastropod species Pyrgophorus hibbardi. The origin and paleolimnological significance of the spinose morph has been a source of much conjecture that has influenced environmental reconstructions of this assemblage. In one hypothesis the spinose forms of P. hibbardi are assumed to be associated with brackish water conditions by analogy with some populations of a related hydrobiid Potamopyrgus jenkinsi. To test the hypothesis that the spinose forms lived under different water conditions than the non-spinose morphs, we analyzed 10 specimens each of the two varieties for stable oxygen and carbon isotope ratios in the shell aragonite. The mean isotope ratios for the smooth and spinose morphs show no significant difference (oxygen: t = 0.28, df = 18, P (T ≤ t) 0.78 n.s.; carbon: t = 0.96, df = 18, P (T ≤ t) 0.35 n.s). We conclude that the lack of a statistically significant difference between the means of the oxygen and carbon isotope values for the smooth and spinose morphs suggests that the two forms lived in waters having similar isotope signatures. The considerable range in oxygen isotope values recorded by both morphs of P. hibbardi, including values as high as 5–6‰, suggest that both morphs were associated with waters which were periodically evaporatively enriched in 18O.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007918626424
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  • 86
    Digitale Medien
    Digitale Medien
    Late Quaternary diatom response to vegetation and climate change in a subalpine lake in Banff National Park, Alberta (1998)
    Springer
    Journal of paleolimnology 20 (1998), S. 253-265 
    Details
    ISSN: 1573-0417
    Schlagwort(e): Late Quaternary ; diatoms ; climate change ; vegetation change ; shallow ; subalpine ; Crowfoot Lake ; Alberta ; paleolimnology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract The late Quaternary diatom record from subalpine Crowfoot Lake, Banff National Park, Alberta (lat. 51° 61′N; long. 116° 31′W) has been analyzed. Results are related to independently inferred vegetation and climate changes. No diatoms were found in the basal diamict that predates 11330 14C yr BP. Very few occur until ca. 10 10014 C yr BP probably due to the short time between de-glaciation and an advance of the Crowfoot Glacier during the ‘Younger Dryas Chron’. Initial pioneering species were characteristic of alkaline water and calcareous organic sediments. They appeared as sediments became organic and laminated suggesting increasing water clarity, and as the Pinus-dominated forest expanded and the climate warmed. After ca. 9060 14C yr BP diatom numbers increased rapidly, reaching a maximum prior to the Mazama tephra; they remained high until ca. 3500 14C yr BP. The period between ca. 9060 and 3500 14C yr saw timberline elevation increase and the dominance of xerophytic taxa. These are consistent with early to mid-Holocene warmth and aridity. Diatom productivity reflects the warm climate and presumably longer ice-free season, a stable catchment and transparent water. Decreases in diatom productivity coincide with a vegetation change with reduction of xerophytic taxa and the appearance of a closed Picea-Abies forest, hence a cooler, wetter climate at ca. 4100 to 3500 14C yr BP. The diatom numbers during the Neoglacial were of the same magnitude as prior to ca. 9060 14C yr BP. Small species of Fragilaria (overwhelmingly Fragilaria construens v. venter) became extremely dominant during the period of high diatom productivity, and remained so thereafter. Recovery of the lake appears to have been rapid after deposition of the Mazama tephra. Maximum occurrence of Cyclotella radiosa occurred ca. 8000 14C yr BP during the warm early Holocene and may reflect this warmer climate, a longer ice-free season than presently, perhaps less turbid water, or it may reflect a subtly higher nutrient status of the lake water. The diatom record of Crowfoot Lake has responded with sensitivity, particularly in terms of productivity, to the Holocene vegetation and climate changes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007978730349
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  • 87
    Digitale Medien
    Digitale Medien
    Paleolimnological evidence for the recent acidification of Llyn Hir, Dyfed, Wales (1989)
    Springer
    Journal of paleolimnology 2 (1989), S. 245-262 
    Details
    ISSN: 1573-0417
    Schlagwort(e): acidification ; diatoms ; sediment chemistry ; magnetic stratigraphy ; soot ; paleolimnology ; Wales
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract A variety of paleolimnological techniques, coupled with historical data on land-use and fisheries, are used to evaluate the magnitude, timing, and causes of acidification of Llyn Hir, a moorland lake in central Wales. pH reconstruction based on diatom analysis suggests a gradual decline in lakewater pH beginning ca. 1870 and intensifying in the mid-1930's, with a total decline of 1.1 pH units between 1870 and 1984. This pH decline correlates with increased sedimentary concentrations of carbonaceous particles, trace metals, and magnetic minerals, which indicate the local deposition of atmospherically transported products of fossil-fuel combustion. Pollen data and the historical record show no significant alterations in land-use or catchment vegetation, indicating that acidification of Llyn Hir is a result of the increased deposition of atmospheric pollutants, not of land-use and vegetation change.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00195475
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  • 88
    Digitale Medien
    Digitale Medien
    Reconstruction of Holocene paleoenvironments in the endorheic basin of Laguna de Gallocanta, Central Spain by investigation of mineralogical and geochemical characters from lacustrine sediments (1998)
    Springer
    Journal of paleolimnology 20 (1998), S. 217-234 
    Details
    ISSN: 1573-0417
    Schlagwort(e): bulk geochemistry ; Holocene ; lacustrine sediments ; paleoenvironments ; paleolimnology ; statistical methods
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract The paper involves detailed geochemical and mineralogical analysis of lacustrine sediments from a 95 cm core profile collected in the closed lake basin of the Laguna de Gallocanta, central Iberian Chain. The environmental and depositional changes are confirmed by: (1) variations in concentrations of SiO2, CaO and P2O5, (2) Fe2O3:MnO-ratios, (3) ς(CaO,MgO):SiO2-ratio, (4) statistical relationship of silica and phosphate content to metallic oxide content, (5) the Mg:Ca-ratio of protodolomites in relation to the position of the diffraction angle of dolomite's major diffraction peak (dol100, and (6) changes in mineralogical composition. Three sedimentary units were identifyed and characterized by their mineralogical and geochemical composition. The deposition of the underlying strata (section 1) occurred under sub-arid conditions. The environment changed to sub-humid conditions during deposition of the sediments in section 2 (post Middle Ages). Increasing aridity influenced the accumulation of the upper sediments (section 3). It is also proven that mineralogical analyses of lacustrine sediments allows mostly conclusions on the limnic environments during deposition. In contrast to this, geochemical features of lacustrine sediments indicate weathering and soil forming processes during deposition and the overall geomorphological system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007924000636
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  • 89
    Digitale Medien
    Digitale Medien
    High-resolution paleoecological analysis of recent disturbance in a southern Chilean Nothofagus forest (1998)
    Springer
    Journal of paleolimnology 20 (1998), S. 235-252 
    Details
    ISSN: 1573-0417
    Schlagwort(e): fire ; disturbance ; paleoecology ; paleolimnology ; pollen ; chrystophytes ; charcoal ; Chile
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract A 1600 year paleoecological record of environmental change is developed from a small lake in the Nothofagus forest of southern Chile (45.5°S, 72°W). High resolution fossil pollen, charcoal, sedimentological, and chrysophycean stomatocyst analyses are used to investigate the impacts of natural and anthropogenic disturbances on terrestrial and lacustrine environments. Chronological control is based on a combination of 210Pb and 14C dating. Temporal resolution during the past 150–200 yr is ca. 8 yr/sample. The macroscopic charcoal record correlates very closely with historical and dendroecological records of 20th century anthropogenic burning in this region. The chrysophyte stratigraphy indicates that this burning had immediate impacts on the lake itself, while the pollen record provides evidence for a succession of vegetation changes lagging slightly behind the disturbance. These palynological changes are very similar to the pollen signal of European disturbance in northeastern North America. Pre-European shifts in chrysophyte assemblages may be due to the influence of earthquake activity on the lake, though there is no corroborative evidence in the pollen or charcoal records. This study demonstrates that high resolution paleoecological methods can be used to help bridge the temporal gap between traditional ecological and paleoecological studies of environmental change in the temperate forests of southern South America.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007950905200
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  • 90
    Digitale Medien
    Digitale Medien
    Chrysophycean cysts in Sierra Nevada (California) lake sediments: paleoecological potential (1992)
    Springer
    Journal of paleolimnology 7 (1992), S. 73-94 
    Details
    ISSN: 1573-0417
    Schlagwort(e): acidification ; Chrysophyceae ; cyst ; paleolimnology ; Sierra Nevada ; statospore ; stomatocyst
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Thirty-three lakes in the Sierra Nevada range of California were investigated as part of a paleoecological study of the potential effects of acid deposition on sensitive lake/watershed ecosystems. Chrysophyte cysts from surface sediment samples were analyzed and compared with data on pH and alkalinity. This paper identifies the twenty-five dominant chrysophyte cyst taxa and provides information on their morphology, abundance, distribution and ecology. Chrysophycean cysts were generally abundant and well-preserved in lake sediments of our study sites. Twelve taxa occurred in more than twenty of the thirty-three lakes; these taxa were often quite abundant. In contrast, only nine taxa occurred in ten or fewer lakes. Abundance Weighted Mean (AWM) pH varied from 6.45 to 8.34 and AWM alkalinity varied from 46 to 588 μeq/L. We delineated pH preference categories, based on AWM pH values and frequency diagrams of cyst abundance vs. lake-water pH. We classified five taxa as acidophilous, nine as circumneutrals, six as alkaliphilous and five as indifferent. Given that the cyst types differ greatly in their abundance relative to pH and alkalinity, it is clear that they have potential for paleolimnological studies of Sierra lakes biogeochemistry.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00197032
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  • 91
    Digitale Medien
    Digitale Medien
    A simple, inexpensive piston corer for collecting undisturbed sediment/water interface profiles (1992)
    Springer
    Journal of paleolimnology 7 (1992), S. 157-161 
    Details
    ISSN: 1573-0417
    Schlagwort(e): coring device ; paleolimnology ; sediments
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00196870
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  • 92
    Digitale Medien
    Digitale Medien
    Simple gravity corer suitable for educators (1992)
    Springer
    Journal of paleolimnology 7 (1992), S. 253-255 
    Details
    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; paleoecology ; limnology ; coring ; sediments ; education
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Instructions for construction and use of a simple and inexpensive sediment coring device are presented. The sampler is suitable for use in high school and undergraduate science courses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00181717
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  • 93
    Digitale Medien
    Digitale Medien
    Stratigraphy of total metals in PIRLA sediment cores (1992)
    Springer
    Journal of paleolimnology 7 (1992), S. 191-214 
    Details
    ISSN: 1573-0417
    Schlagwort(e): geochemistry ; metals ; lake sediments ; paleolimnology ; United States
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Sediment cores from 30 low-alkalinity lakes in northern New England (NE), New York (NY), the northern Great Lakes States (NGLS) of Minnesota, Michigan, and Wisconsin, and Florida (FL) have been dated by 210Pb and analyzed for water and organic content, eight major elements (Al, Ti, Fe, Mn, Ca, Mg, Na, K) plus four trace metals (Pb, Zn, Cu, and V). Variations in the percentages of major elements through time are dominated by long-term independent variations in the abundance of SiO2, FeO, and to a lesser extent Ca and Al. Additional variations are caused by varying proportions of inorganic matter. Major variations in chemistry are generally unrelated to documented distrubances in the watersheds; most disturbances are minor fires or selective logging. Accelerated accumulation of Pb from atmospheric sources into sediment first occurs in sediment dated between 1800 and 1850 in NY and NE, slightly later in the NGLS region, and about 1900 in FL. Modern accumulation rates in all areas are comparable (ca. 1 to 4 μg cm−2 yr−1). Accumulation rates of Pb in some lakes have declined significantly from 1975 to 1985. Atmospheric deposition of anthropogenic Zn and Cu is also indicated by generally increasing accumulation rates in sediment cores, but the record is not as clear nor are chemical profiles in all lakes parallel to the trends in atmospheric emissions inferred on the basis of fossil fuel consumption, smelting, and other industrial activities. Inter-lake variations in profiles of Cu and Zn are large. Vanadium accumulation rates increase by the 1940s in NY and NE, but not until the 1950s in the NGLS region. This timing correlates with regional trends in the combustion of fuel oil, a major source of atmospheric V. Acidification of some of the lakes is suggested by decreases in the concentration and accumulation rates of Mn, Ca, and Zn in recent sediment, relative to other elements of catchment origin. The decreases generally occur slightly before the onset of acidification as indicated by diatoms. Increased sediment accumulation rates for Fe may indicate the acidification of watershed soils. The use of the accumulation rate of TiO2 as an indicator of rates of erosion and for normalization of trace metal accumulation rates is in question for lakes where the flux of TiO2 from the atmosphere varies and is a significant fraction of the total flux of TiO2 to the sediment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00181714
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  • 94
    Digitale Medien
    Digitale Medien
    A review of factors that regulate carotenoid and chlorophyll deposition and fossil pigment abundance (1993)
    Springer
    Journal of paleolimnology 9 (1993), S. 109-127 
    Details
    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; carotenoid ; chlorophyll ; pigment ; sediment ; fossil ; degradation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Limnological surveys show that fossil pigment concentration is an accurate predictor of algal production. However, experimental and mass flux studies indicate that 〉90% of pigment is degraded to colourless compounds before permanent burial. To reconcile these views, this paper reviews current literature on pigment degradation and proposes a hierarchical control model for pigment deposition and fossil abundance. Over the widest range of production, pigment deposition and fossil concentration are proportional to algal standing crop. However, within a narrower range, the actual concentration of pigment in sediments is regulated by photo- and chemical oxidation. Three phases of loss exist: rapid oxidation in the water column (T1/2=days); slower post-depositional loss in surface sediments (T1/2=years); and very slow loss of double bonds in deep sediments (T1/2=centuries). Despite losses during deposition, fossil and algal abundance remain correlated through time, so long as there is no change in basin morphometry, light penetration, stratification or deepwater oxygen content. At the finest scale, food-web processes can increase the preservation of pigments from edible algae by incorporating pigments into feces that sink rapidly and bypass water column losses. As a consequence of selective loss during deposition and initial burial, carotenoid relative abundance is an unreliable measure of phytoplankton community composition. Instead, absolute concentration — scaled to the historical maximum — should be used for fossil interpretations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00677513
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  • 95
    Digitale Medien
    Digitale Medien
    Historical loading record of sulfur in an Adirondack Lake (1993)
    Springer
    Journal of paleolimnology 9 (1993), S. 243-256 
    Details
    ISSN: 1573-0417
    Schlagwort(e): sulfur ; sediments ; mathematical model ; paleolimnology ; non steady-state diagenesis ; Adirondack
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract A model for the distribution of sulfur in the sediments of a lake in the Adirondack Mountains, New York, is developed to gain insight into the timing and magnitude of anthropogenic increases in sulfur loading. Surficial sulfur concentrations are about 3500 µg g−1, increase to 6000–7000 µg g−1 at a depth of about 6 cm, and then decrease downcore to background levels of about 2500 µg g−1. Sulfate concentrations are about 60–80 µM in the overlying water and decrease rapidly below the sediment-water interface. This reflects assimilatory reduction and/or dissimilatory reduction of sulfate and incorporation into the inorganic and/or organic solid-phase fractions of the sediment. A mathematical model is constructed assuming sulfur is incorporated into sediments by burial of detrital organic matter and by diffusion of sulfate from the overlying water with subsequent fixation in the sediment. Several historical scenarios of atmospheric sulfate loading rates were examined as model boundary conditions. Model results are compared with observed sedimentary sulfur profiles. The observed sediment sulfur profiles are best described using model boundary conditions showing increases in lake water sulfate concentrations since about 1940. Assuming as much as a decade of retention of sulfate within the terrestrial portion of the ecosystem, this suggests that significant increases in sulfate deposition rates began sometime after 1930 in this relatively remote area.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00677216
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  • 96
    Digitale Medien
    Digitale Medien
    Paleolimnology of McNearney lake: an acidic lake in northern Michigan (1990)
    Springer
    Journal of paleolimnology 3 (1990), S. 13-34 
    Details
    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; diatoms ; diatom-inferred pH ; trace metals ; sulfur ; lakewater chemistry ; seepage lake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract McNearney Lake is an acidic (pH=4.4) lake in the Upper Peninsula of Michigan with low acid neutralizing capacity (ANC=-38 μeq L-1) and high SO inf4 sup2- and aluminium concentrations. Oligotrophy is indicated by high Secchi transparency and by low chlorophyll a, total phosphorus, and total nitrogen concentrations. The lake water is currently acidic because base cations are supplied to the lake water at a low rate and because SO inf4 sup2- from atmospheric deposition was not appreciably retained by the lake sediments or watershed and was present in the water column. This interdisciplinary paleolimnological study indicates that McNearney Lake is naturally acidic and has been so since at least 4000 years B.P., as determined from inferred-pH techniques based on contemporary diatom-pH relationships. Predicted pH values ranged from 4.7 to 5.0 over the 4000-year stratigraphy. Considerable shifts in species composition and abundance were observed in diatom stratigraphy, but present-day distributions indicate that all abundant taxa most frequently occur under acidic conditions, suggesting that factors other than pH are responsible for the shifts. The diatom-inferred pH technique as applied to McNearney Lake has too large an uncertainly and is not sensitive enough to determine the subtle recent changes in lakewater pH expected from changes in atmospheric deposition because: (1) McNearney Lake has the lowest pH in the contemporary diatom data set in the region and confidence intervals for pH predictions increase at the extremes of regressions; (2) other factors in addition to pH may be responsible for the diatom species distribution in the lake and in the entire northern Great Lakes region; (3) McNearney Lake has a well-buffered pH as a consequence of its low pH and high aluminium concentrations and is not expected to exhibit a large pH change as a result of changes in atmospheric deposition; and (4) atmospheric deposition in the region is modest and would not cause a pH shift large enough to be discernable in McNearney Lake. Elevated atmospheric deposition is indicated in recent sediments by Pb, V, and polycyclic aromatic hydrocarbon accumulation rates and to a lesser extent by those of Cu and Zn; however, these accumulation rates are substantially lower than those observed for acidified lakes in the northeastern United States. Although atmospheric loadings of materials associated with fossil fuel combustion have recently increased to McNearney Lake and apparently are continuing, the present study of the diatom subfossil record does not indicate a distinct, recent acidification (pH decrease).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00209297
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  • 97
    Digitale Medien
    Digitale Medien
    Drainage ditch erosion history as recorded in the varved sediment of a small lake in East Finland (1990)
    Springer
    Journal of paleolimnology 3 (1990), S. 161-169 
    Details
    ISSN: 1573-0417
    Schlagwort(e): paleolimnology ; artificial drainage ; ditch erosion ; sediment varves ; 210Pb-dating
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Short core stratigraphy of total N, P, Zn, Hg and diatoms were investigated in the varved sediment of Lake Heinälampi, a small 8 m deep pond in East Finland. The sediment has recently changed from organic mud to minerogenic silt. The presence of varved sediment offers independent control for 210Pb and 137Cs dates and these are in good agreement: the sediment quality initially changed around the year 1930 due to increaed field erosion, and the inflow of mineral matter was further increased by ditching of paludified forests in 1980. Diatom analysis reveals that eutrophication has occurred before and concurrent with the sedimentary change. The causes of eutrophication and the increased levels of Zn and Hg are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00414069
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  • 98
    Digitale Medien
    Digitale Medien
    The PIRLA project (Paleoecological Investigation of Recent Lake Acidification): an introduction to the synthesis of the project (1990)
    Springer
    Journal of paleolimnology 3 (1990), S. 187-194 
    Details
    ISSN: 1573-0417
    Schlagwort(e): acid deposition ; lake acidification ; paleolimnology ; North America
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Collected sets of papers synthesizing data derived from the PIRLA project (Paleoecological Investigation of Recent Lake Acidification) will appear in coming issues of the Journal of Paleolimnology. This paper is designed to highlight these forthcoming papers, review the development and objectives of PIRLA, and acknowledge the many who have supported PIRLA in so many crucial ways.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00219458
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  • 99
    Digitale Medien
    Digitale Medien
    Sequentially extracted metals in Adirondack lake sediment cores (1990)
    Springer
    Journal of paleolimnology 3 (1990), S. 243-252 
    Details
    ISSN: 1573-0417
    Schlagwort(e): trace metals ; aluminum ; sequential extraction ; acidic lakes ; paleolimnology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Metal deposition patterns have been examined in sediment cores from three lakes in the Adirondack region of New York (USA). Sequential chemical extraction of Al, Fe, Mn, Pb, and Zn has yielded information on their chemical nature and potential mechanisms involved in their deposition. Results indicate historical changes in watershed chemistry may have influenced metal chemistry in these lakes. Detailed descriptions of the chemical forms of metals in sediments is not possible due to the fact that extraction methods are only operational. However, in two systems known to have been acidified in recent time by acidic deposition (Big Moose L. & Deep L.), concentrations of labile Al (in C1−C4 fraction) increase after 1940–1950, corresponding with lake acidification as inferred from diatom assemblages. Temporal trends in the inputs of Pb in the C1−C4 fraction are also consistent with known historical changes in atmospheric Pb inputs to the region. Chemical stratigraphies of Fe and Mn are most likely dominated by internal biogeochemical cycling within sediments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00219460
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  • 100
    Digitale Medien
    Digitale Medien
    Utility of scaled chrysophytes for inferring lakewater pH in northern New England lakes (1990)
    Springer
    Journal of paleolimnology 3 (1990), S. 269-286 
    Details
    ISSN: 1573-0417
    Schlagwort(e): scaled chrysophytes ; pH reconstructions ; algal microfossils ; lake acidification ; paleolimnology ; New England ; CCA ; DCA ; PCA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Scaled chrysophytes in the surface sediments of 58 soft-water northern New England lakes were analyzed to assess their usefulness for inferring pH. The distributions of many taxa are correlated with lakewater pH and associated variables. Canonical correspondence analysis (CCA) and clustering grouped chrysophyte taxa according to their distributions along the pH gradient. For example, Chrysodidymus synuroideus, Mallomonas hindonii, and M. hamata commonly occur in acidic waters (pH〈5.5), whereas M. caudata and M. pseudocoronata are common in circumneutral to alkaline waters. Of the five predictive models developed to infer pH, CCA based calibration had the lowest standard error (0.35 pH units). A CCA based predictive model was also developed to infer total alkalinity. The study provides strong evidence that, in the absence of past measured pH data, stratigraphic studies of sedimentary chrysophyte scales will provide accurate reconstructions of pH in northern New England lakes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00219462
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