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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 677-681 
    ISSN: 1572-8854
    Schlagwort(e): Anthraquinone ; crystal structure ; intramolecular hindrance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound crystallizes in the monoclinic space group, P21/c;a=12.938(1),b=11.041(1),c=19.285(2) Å, β=104.314(8)°,Z=4. Refinement based on 1660 unique observed reflections converged toR=0.054. The anthraquinone moiety is distorted due to intramolecular steric hindrance from the tosylate groups.
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  • 2
    ISSN: 1572-8854
    Schlagwort(e): Organoiron complex ; dinuclear complex ; crystal structure ; phosphonium ylid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound crystallizes in the centrosymmetric monoclinic space group P21/n withZ=4. The cation consists of two (η5-C5h5)Fe(CO) units which are linked via a metal-metal bond (Fe(1)−Fe(2)=2.530(1) Å), a bridging carbonyl ligand (Fe(1)−C(4)=1.912(8) Å. Fe(2)−C(4)=1.940(9) Å) and a bridging phosphonium ylid ligand (Fe(1)−C(1)=1.991(6) Å, Fe(2)−C(1)=1.985(6) Å and C(1)−P(1)=1.781(6) Å).
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 747-752 
    ISSN: 1572-8854
    Schlagwort(e): Phosphine oxide ; quaternary ammonium ; water-soluble phosphine ; crystal structure ; hydrogen bonding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound crystallizes in the centrosymmetric triclinic space group $$P\bar 1$$ withZ=4. The crystallographic asymmetric unit contains two independent cations; interatomic distances within these include P=O=1.47(1) and 1.47(1) Å, P−C6H5=1.78(2)–1.81(1)Å and P−CH2CH2NMe3 +=1.80(1) and 1.81(1) Å. The phosphine oxide moiety is involved in intermolecular hydrogen bonding ()...H−C, with O...H≥2.42Å) and the iodide is involved in I...H−C contacts with I...H≥3.10Å.
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 185-189 
    ISSN: 1572-8854
    Schlagwort(e): Solid-solid reaction ; inclusion compound ; p-toluidine ; cholic acid ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Cholic acid undergoes solid-solid reactions with some aromatic molecules to form inclusion compounds. Simple shaking of a mixture of powdered cholic acid andp-toluidine results in formation of the 1∶1 (host:guest) inclusion compound which has the same structure as that formed by conventional crystallization methods: monoclinic space groupP21 witha=13.577(4),b=8.078(2),c=14.182(6) Å, β=114.42(3)°,Z=2 andR 1=0.061 for 2680 unique reflections.
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  • 5
    ISSN: 1572-8854
    Schlagwort(e): Ruthenium(II) complex ; disordered structure ; crystal structure ; solvate ; triphenylphosphine ; bipyridyl
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The complexcis-[Ru{4,4′-(t-Bu)2bpy}2(PPh3)Cl+][ClO 4 − ·0.5(toluene)·0.5(MeCN), where 4,4′-(t-Bu)2bpy=4,4′-di(t-butyl)-2,2′-bipyridyl crystallizes with an ordered racemic mixture of the chiral cations in the centrosymmetric triclinic space group $$P\bar 1$$ (No. 2). The structure was refined toR=4.42% for those 6426 reflections with 20=5–50o and |F o|〉6σ(F). Ruthenium ligand distances are Ru−Cl=2.423(2)Å, Ru−PPh3=2.346(2)Å and Ru−N=2.056(4)–2.098(4)Å. Both the Ru(II)-containing cation and the perchlorate anion are ordered, but the toluene and acetonitrile exhibit an interesting type of scrambled disorder about the inversion center atx=1,y=1/2,z=0.
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  • 6
    ISSN: 1572-8862
    Schlagwort(e): Rhenium ; dirhenium complexes ; rhenium-rhenium multiple bonds ; isocyanide ligands ; carbonyl ligand ; structural isomers ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The monocarbonyl complex Re2Cl4(µ-dppm)2(CO) reacts with xylyl isocyanide in acetonitrile to afford the bioctahedral complex (CO)Cl2Re(µ-dppm)2 ReCl2(CNxyl), 2b. This is a different structural isomer from the edge-sharing bioctahedral complex Cl2Re(µ-Cl)(µ-dppm)2ReCl(CNxyl) or this same stoichiometry which A formed when acetone is be reaction solvent. The complex2b reacts with a further equivalent of xylNC in the presence of TlO3SCF3 in dichloromethane to form a red complex of composition [Re2Cl3(µ-dppm)2 (CO)(CNxyl)2]O3SCF3. 3, which has the open bioctahedral structure [(xylNC)2ClRe(µ-dppm)2ReCl2(CO)]O3SCF3. This is a third isomeric form of this dirhenium cation: the previously isolated green and yellow forms have edge-sharing bioctahedral structures. Crystal data for3 at 295 K: orthorhombic space group Pbca (No. 61) witha=22.654(5) Å,b=22.717(4) Å,c=27.324(4) A,V= 14061(7) Å3, andZ = 8. The structure was refined to R = 0.059 (R, = 0.134 ) for 14164 data. The Re-Re distance is 2.3833(8) Å.
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  • 7
    ISSN: 1572-8854
    Schlagwort(e): Ruthenium(II) ; bipyridyl ; phenyldi(o-tolyl)phosphine ; solvate ; hydrogen bonding ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The complexcis-[Ru(bpy)2{PPh(o-tolyl)2}Cl+][ClO4 −] crystallized from a solution in dichloromethane as the dichloromethane-water solvate. The structure was refined toR=4.5% for those 2433 reflections with |F o|〉6σ(|F o|). The octahedral Ru(II) cation is associated with metal-ligand distances as follows: Ru−Cl=2.434(3)Å, Ru-PPh(o-tol)2=2.382(2)Å, and Ru−N=2.037(7)–2.088(7)Å. The structure is stabilized by a hydrogen-bonded CH2Cl2...ClO4 −...H2O channel which incorporates adventitious water of crystallization.
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  • 8
    ISSN: 1572-8854
    Schlagwort(e): Silver ; stearate ; triphenylphosphine ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystal and molecular structure of [bis-triphenylphosphine-silver(I) stearate], [((C6H5)3P)2Ag(O2C(CH2)16CH3)], has been determined by single crystal X-ray analysis: the space group is PT witha=12.021(4),b=13.916(5)1,c=14.678(5) Å, α=95.952(5), β=101.249(6), γ=93.259(5)°,V=2388(2) Å3, andD calc=1.293 g/cm3 forZ=2. The silver is four coordinate: the carboxylate symmetrically chelates the silver while the triphenylphosphine ligands occupy the third and fourth coordination sites. The strong bonding nature of the phosphine ligands, as indicated by the Ag−P bond lengths, 2.446(3) and 2.424(3) Å, dominates the coordination sphere of the silver and forces the initial carboxylate ligand to rearrange from bridging to chelating resulting in weaker Ag−O bonds, as indicated by the extended Ag−O bond lengths, 2.399(8) and 2.449(8) Å. Unlike the free acid, the long hydrocarbon chain is not linear, and exhibits disorder in the lattice. The structure of the title complex explains the dramatic shift in solubility properties compared to the starting phosphine free silver carboxylate.
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  • 9
    ISSN: 1572-8854
    Schlagwort(e): Ruthenium(II) complex ; organoruthenium compound ; bis(1,2-diphenylphosphino)ethane ligand ; ruthenium-nitro complex ; crystal structure ; cyclopentadienyl derivative ; methanol solvate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title complex crystallizes in the centrosymmetric monoclinic space group C2/c (No. 15) withZ=8. The structure was refined toR=4.49% for those 2745 independent reflections with 2θ=5–50o and |F σ|〉6σ(F). Ruthenium-ligand distances are as follows: Ru-P=2.284(2) and 2.286(2) Å, Ru-NO2=2.049(6) Å and Ru-C(Cp)=2.210(10)-2.246(9) Å. Bond lengths within the nitro ligand are N(1)-O(1)=1.226(10) Å and N(1)-O(2)=1.244(10) Å. The methanol of solvation is ordered but is subject to large thermal vibrational motions.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 461-465 
    ISSN: 1572-8854
    Schlagwort(e): Molecular dynamics ; crystal structure ; TOT clathrate ; thiophene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Tri-o-thymotide (TOT) forms a cage-type clathrate with the thiophene guest molecule in a host:guest ratio of 2∶1. This clathrate crystallizes in the trigonal system (space groupP3121). The unit cell, of dimensionsa=b=13.585(4),c=29.914(12)Å, contains 6 TOT and one thiophene molecule. The crystal structure, established by direct methods (R=0.053), indicates that the host cavity has an oblate-ellipsoid shape with a crystallographic twofold axis parallel to the largest dimension of the cage. The guest molecule within the cavity is disordered. Molecular dynamics simulations have been performed and indicate that the guest molecules have hindered molecular freedom around the shortest ellipsoid axis of the cavity, and may produce a dynamic disorder in the cage of the TOT clathrate.
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  • 11
    ISSN: 1572-8854
    Schlagwort(e): Ruthenium(II) complex ; tri-n-propylphosphine ; terpyridine ; ruthenium-nitro complex ; crystal structure ; disordered ligands
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The complexmer,trans-[Ru(NO2)(trpy)(PPr3) 2 + ][ClO 4 − ]crystallizes in the centrosymmetric orthorhombic space group Pnma withZ=4. Both the ruthenium(II) cation and the perchlorate ligand lie about crystallographic mirror planes. The nitro ligand is not coplanar with the Ru(trpy) moiety and suffers from two fold disorder about its Ru−N bond such that the two sets of oxygen atoms have symmetry-related sites above or below the crystallographic mirror plane. The n-propyl groups within the PPr3 ligands suffer from disorder of their C(α) and C(β) atoms but share common C(γ) sites. Ruthenium-ligand distances are: Ru−PPr3=2.398(2)Å, Ru−NO2=2.053(7) Å, Ru−N(trpy, outer)=2.078(6) and 2.092(6) Å and Ru−N(trpy, central) =1.965(6) Å.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 355-360 
    ISSN: 1572-8854
    Schlagwort(e): Chromium ; carbonyl ; arene ; acetal ; crystal structure ; conformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The structures of the (benzene dialkylacetal)tricarbonyl chromium complexes [η6-C6H5-CH(OR)2]Cr(CO)6 (R=Me,1; Et,2), are reported. The compounds were examined as part of a study of the conformations of the tripodal tricarbonylchromium group. For [η6-C6H5-CH(OMe)2]Cr(CO)3,1, monoclinic,P21/c (# 14),a=15.235(1) Å,b=6.5304(5) Å,c=12.702 Å, β=103.197(1)o,Z=4. For [η6-C6H5-CH(OEt)2]Cr(CO)3,2, monoclinic,P21/c (# 14),a=9.859(3) Å,b=10.547(3) Å,c=15.138(3) Å, β=108.42(2)o,Z=4. The data show that the molecules adopt the expected “three-legged piano stool” structure. The carbonyl ligands in1 adopt an eclipsed arrangement with respect to the arene ring and its substituent, while those in2 are staggered. These conformations are consistent with the notion that the acetal substituent behaves largely as an electroneutral group, or at most as a weak electronic acceptor.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 389-392 
    ISSN: 1572-8854
    Schlagwort(e): p-Methoxyphenyltelluro ; x-ray diffraction ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract C23H18TeO,M r=437.97, $$P\bar 1$$ ,a=9.940(2),b=13.664(3),c=7.895(2) Å, α=80.60(1), β=69.71(2), γ=75.95(1)°,V=972.0(4) Å3,Z=2,R=0.041 for 2668 observed reflections. The Te−C bond distances are 2.109(5)Å and the C−Te−C angle is 96.0(2)°. The phenyl rings are planar to within experimental accuracy, making dihedral angles of 64.6(2), 65.3(2) and 31.1(3)°.
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 403-406 
    ISSN: 1572-8854
    Schlagwort(e): Cyclotrithiazene ; arylaminophospine ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound (C6H5)2(OC4H8N)P=N−S3N3 crystallizes in the space group $$P\bar 1$$ with unit cell parametersa=9.3900(2),b=9.4747(1),c=11.3850(3) Å, α=95.73(4), β=96.85(6), γ=104.26(2)o, and Z=2. The tricoordinated sulfur of the cyclotrithiazene ring deviates from the mean plane of other skeletal atoms by 0.683(4) Å. The angle at this atom is the smallest in the ring and is enclosed by the longest S−N bonds observed in the ring.
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  • 15
    ISSN: 1572-8854
    Schlagwort(e): Copper(II) complex ; crystal structure ; coordination polymer ; betaine ; dicarboxylate ligand
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Three polymeric copper(II) complexes of a flexible double betaine, namely, [{Cu(L)Cl2(H2O)} n ]·2 n H2O (1), [{Cu(L)Br2(H2O)} n ]·2nH2O (2), and [{Cu(L)(H2O)4} n ](ClO4)2n ·2nH2O (3) [L=−O2CCH(Me3N+)CH2CH2CH(Me3N+CO2], have been prepared and characterized by singlecrystal X-ray analysis. Isomorphous complexes (1) and (2) crystallize in space groupC2/c (No. 15) witha=17.725(3),b=5.958(2),c=19.077(3) Å, β=110.70(1)o,V=1881.4(4) Å3, Z=4 anda=18.268(4),b=5.948(3),c=19.166(5) Å, β=109.08(2)o,V=1964.7(9) Å3, Z=4, respectively. Complex (3) belongs to space groupPĪ (No. 2) witha=6.203(1),b=9.293(2),c=12.035(2) Å, α=86.56(2), β=87.33(3), γ=71.23(2)o,V=655.4(2) Å3 and Z=1. The crystal structure of (1) and (2) features an infinite zigzag chain composed of an alternate arrangement of metal atoms and double betaines ligands, with each Cu(II) atom in a distorted CuX2O3 [X-Cl, Br] square-pyramidal geometry, and hydrogen bonding between adjacent chains leads to a layer structure concentrated the (200) family of planes. Complex (3) exhibits a layer structure corresponding to the (001) family of planes, in which neighboring chains constructed from the metal atoms and the double betaine ligands are cross-linked by hydrogen bonding between the aqua ligands. The Cu(II) atom is coordinated in a CuO6 octahedral geometry with Jahn-Teller distortion.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 503-508 
    ISSN: 1572-8854
    Schlagwort(e): Tin(IV) sodium(I) complex ; ethylenediaminetetraacetic acid ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract NaSn(OH)(edta)(H2O) is monoclinic, space groupP21/c, witha=9.747(3)Å,b=9.121(3)Å,c=16.430(6)Å, β=98.69(4)°, Å3, andZ=4. The coordination environment of Sn(IV) is a capped octahedron. Sn−O distances range from 1.990(6)Å to 2.351(7)Å. Na(I) is five coordinated to three different edta molecules. Na−O distances range from 2.283(9)Å to 2.414(7)Å. The edta ligand presents the E, G/R conformation. The crystal structure is composed of sheets parallel to (001): inside a sheet Sn(OH)(edta) molecules are connected to each other by the Na(I) interactions.
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 515-518 
    ISSN: 1572-8854
    Schlagwort(e): Antiarrhythmic agent ; crystal structure ; absolute configuration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound crystallizes in the orthorhombic space groupP212121, withZ=4,a=4.770(1)Å,b=6.620(1)Å,c=37.550(7)Å,R=0.04. The most important factors affecting conformation of the molecules are: the protonation state of the N(9) atom andortho-substitution of the benzene ring in the acetanilide system. Protonation promotes an extended form of the molecule and 2,6-substitution forces a twist of at least 60° between the benzene ring and amide group planes. The resulting separation of lipophilic (xylidine) and amine groups, being two important pharmacophores, equals about 5Å in tocainide and all other structures comprising the amino-2,6-dimethylacetanilide system.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 553-557 
    ISSN: 1572-8854
    Schlagwort(e): Silver(I) complex ; synthesis ; crystal structure ; spectroscopic properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The reaction of [Ph3PAgI]4 with sodium phenylacetate in MeOH and CH2Cl2 at room temperature gave rise to a binuclear silver complex with triphenylphosphine and phenylacetate mixed ligands, [Ph3PAg(O2CCH2Ph)]2. The crystal and molecular structure of the complex has been determined by single crystal X-ray diffraction analysis. The space group is $$P\bar 1$$ witha=9.198(2),b=9.516(2),c=13.842(3) Å, α=102.00(3), β=108.34(3), γ=93.58(3)°,Z=1, andDc=1.506 g cm−3. The silver atoms are each coordinated by one phosphorus atom from triphenylphosphine and two oxygen atoms from the carboxylate groups in a T-shape. The complex is further characterized by its IR,1H, and31P NMR spectra.
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  • 19
    ISSN: 1572-8854
    Schlagwort(e): Ruthenium(II) complex ; tri-n-propylphosphine ; bipyridyl ; crystal structure ; disorder
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The complexcis-[Ru(bpy)2(PPr3)Cl+][ClO 4 − ] · 0.5 (toluene) crystallizes as a racemate in the monoclinic space group P21/n. Both the PPr3 ligand and the toluene of crystallization are subject to disorder. Ruthenium—ligand distances are: Ru−PPr3=2.348(2) Å, Ru−Cl=2.426(2) Å and Ru−N(bpy)=2.035(6)–2.112(5) Å.
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  • 20
    ISSN: 1572-8854
    Schlagwort(e): Ruthenium(II) complex ; terpyridine ; triphenylphosphine ; ruthenium-nitro complex ; crystal structure ; pseudo-lattice
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The complexmer,trans-[Ru(NO2)(trpy)(PPh3) 2 + ][PF 6 − ] crystallizes in the centrosymmetric monoclinic space groupP21/n withZ=4; the ruthenium atom lies close toy=1/4 and all data withh+l=2n+1 are systematically weak. The trpy ligand is not strictly planar, but has a “dish-like” geometry. The nitro ligand is rotated from the plane of the Ru(trpy) moiety, the N3Ru/NO2 interplanar angle being 32.5o. Ruthenium-ligand distances are: Ru−PPh3=2.418(4) Å and 2.429(4) Å, Ru−NO2=2.063(12) Å, Ru−N(trpy, outer)=2.100(12) Å and 2.116(12) Å and Ru−N(trpy, central)=2.004(11) Å.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 661-665 
    ISSN: 1572-8854
    Schlagwort(e): N,N′-bis(2-hydroxyphenyl)butanediamide ; crystal structure ; hydrolysis product
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The structure of N,N′-bis(2-hydroxyphenyl)butanediamide has been determined. The molecule consists of two 2-hydroxyphenyl moieties which are attached (at the 2 position) to the two nitrogens of the butanediamide. The compound C16H16N2O4 crystallizes in the monoclinic space group P21/c witha=5.576(1),b=4.8853(6),c=25.397(6) Å and β=90.58(1)°.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 691-694 
    ISSN: 1572-8854
    Schlagwort(e): Organotin ; crystal structure ; flavone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The 1∶1 adduct of chlorotriphenyltin with 2′,6′-dimethoxyflavone, (C35H29O4ClSn)Mr=667.78, crystallizes in the triclinic space groupP1 with the following data:a-9.094(2),b=12.369(3),c=14.674(3) Å, α=74.78(2), β=77.00(2), γ=73.06(3)°,V=1503.8(4) Å3,Z=2, Mo-Kα, μ=9, 8 cm−1,Dc=1.475 g cm−3, F(000)=676,T=293K. The structure was solved by direct-methods and has been refined to a finalR value (l〉3σ(I)) of 0.0301. The flavone coordinates to the tin atom through the carbonyl oxygen atom. The metal center exhibits a trigonal bipyramidal configuration with the three phenyl groups in equatorial positions.
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  • 23
    ISSN: 1572-8854
    Schlagwort(e): Betaine ; 4-dimethylaminopyridinioacetate ; hydrogen bonding ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The crystalline dihydrate and hydrochloride trihydrate of a new betaine, namely, L·2H2O (1) and [L2H]Cl·3H2O(2) (L=p-Me2NC5H4N+CH2CO2), have been synthesized and characterized by X-ray crystallography. Molecule L in compound1 [space groupPbcn, witha=15.732(3),b=7.894(2),c=18.304(4) Å, andZ=8] possesses approximateC s symmetry. The formation of hydrogen bonds by water molecules bridging neighboring carboxy oxygen atoms leads to an infinite two-dimensional network composed of a packing of two different kinds of 12-membered rings. In compound2 [space group PT witha=7.341(2),b=9.543(2),c=17.010(4) Å, α=82.43(2)°, δ=80.34(2)°, λ=74.05(2)°, andZ=2], the carboxylate groups of a pair of betaine molecules are bridged by a proton to form a dimeric cation L2H+ with a very strong asymmetric hydrogen bond of length 2.464(7) Å. The crystal structure features a hydrogen-bonded corrugated ribbon comprising an alternate arrangement of edge-sharing centrosymmetric (H2O)4(Cl−)2 and (H2O)4 rings running parallel to thea axis.
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  • 24
    ISSN: 1572-8854
    Schlagwort(e): Bidentate ligand ; crystal structure ; pyrazolyl group ; hydrogen bonding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound lies on a site of C2 symmetry, with the two planar pyrazolyl moieties oriented at 86.1° to one another. The hydrogen atoms were located and refined.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 219-222 
    ISSN: 1572-8854
    Schlagwort(e): Steroid ; organometallic ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract 3α-Triphenylstannylcholest-5-ene (1) has been synthesised and its molecular structure has been determined by single crystal X-ray diffraction. Refinement in the triclinic space groupP1 witha=7.805(6),b=7.862(5),c=32.351(10)Å, α=90.87(8), β=94.77(8) and γ=101.15(4)o converged atR=0.063. One of the two crystallographically independent molecules in the unit cell has a patially disordered side chain. The bond lengths and valency angles about tin indicate some steric hindrance due to the proximity of one of the phenyl rings with the B ring of the steroid nucleus.
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 841-846 
    ISSN: 1572-8854
    Schlagwort(e): Cu(II) resorcylidene aminoguanidine ; synthesis ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The tridentate Schiff base, β-resorcylidene aminoguanidine (RAG)1 was synthesized from 2,4-dihydroxybenzaldehyde and aminoguanidine and complexed with copper(II) to form a copper(II)-β-resorcylidene aminoguanidine (Cu-RAG)2 complex. X-ray diffraction analysis of compound2 (orthorhombic, Pnma,a=11.674(1);b=6.7198(7);c=17.836(2) Å) revealed a square-planar copper(II) cation with a tridentate·ligand bound through two nitrogen atoms (N1 and N3) of the aminoguanidine moiety and an oxygen (O1) of the monodeprotonated dihydroxybenzaldehyde function. The remaining coordination site was occupied by chloride and the structure was rigidly planar as demanded by the restrictions of the crystallographic space group. The unit cell contents exhibited an extended sheet-like structure constructed via hydrogen bonds both intermolecularly and involving two water molecules (O3 and O4) also restricted by the same mirror symmetry. The remaining water (O5) provided for interlayer hydrogen bonding.
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  • 27
    ISSN: 1572-8854
    Schlagwort(e): Pyrazolyl group ; crystal structure ; bidentate ligand ; hydrogen bonding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound consists of two planar pyrazolyl fragments oriented at 73.0° to each other and linked to a common carbon atom. All hydrogen atoms were located unambiguously and their positions were refined.
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  • 28
    ISSN: 1572-8854
    Schlagwort(e): Ruthenium(II) complex ; bipyridyl ; diphenyl(o-tolyl)phosphine ; dichloromethane solvate ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The complexcis-[Ru(bpy)2 {PPh2(o-tol)}Cl][ClO4] crystallizes from dichloromethane as the sesqui-dichloromethane solvate. The complex crystallizes in the monoclinic space group P21/n with Z=4. The structure was refined toR=5.50% for those 2552 independent reflections with |F 0|〉6σ(|F 0|) The octahedral Ru(II) cation is associated with the following bond lengths: Ru-PPh2(o-tol)=2.360(3)Å. Ru−Cl=2.433(2)Å and Ru−N(bpy)=2.041(8)–2.095(8)Å. Both the perchlorate anion and the dichloromethane molecules of solvation exhibit large amplitudes of vibration. One dichloromethane molecule lies in a general position, the other lies about an inversion center and suffers from disorder.
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  • 29
    Digitale Medien
    Digitale Medien
    Springer
    Journal of chemical crystallography 26 (1996), S. 615-619 
    ISSN: 1572-8854
    Schlagwort(e): Disordered trifluoromethyl group ; quinoline ; crystal structure ; AM1 calculation ; mefloquine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The title compound crystallized in space groupPna21 with lattice constantsa=13.406(1),b=18.799 (4), andc=4.785(1). The molecule is essentially flat with only fluorine atoms, methylene hydrogen atoms, and the hydroxyl hydrogen atom out of the plane of the quinoline ring. Only one of the trifluoromethyl groups of the title compound is disordered following a pattern observed in other crystal structures. Quantum chemical calculations at the AM1 level are consistent with this phenomenon. Although the carbon atom of the fixed trifluoromethyl group is further from the quinoline nitrogen atom than the carbon atom of the disordered trifluoromethyl group, the fluorine atoms of the fixed trifluoromethyl group more closely approach the quinoline nitrogen atom by 0.3 Å if the C(8)−C(10) bond in the crystal structure is freely rotated.
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  • 30
    ISSN: 1572-8862
    Schlagwort(e): Niobium(III) ; edge-sharing bioctahedra ; di-p-tolylformamidinato ; thiomethoxide ; double-bond ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The reaction of NaEt3BH with Nb2(μ-SMe2)3Cl6 results in the transfer of a hydride ion to dimethylthioether with concomitant production of methane. Further reaction with potassium di-p-tolylformamidinate, KDTolF, yields Nb2(μ-SMe)2(μ-DTolF)2η2-DTolF:)2.2 toluene, 1. In the latter, two thiomethoxide ions and two DTolF groups bridge the trivalent niobium atoms. Each of the other two DTolF groups chelate a metal atom to give the molecule an edge-sharing bioctahedral structure, The niobium-niobium distance of 2.655(2) A is consistent with the presence of a double bond between the metal atoms.
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  • 31
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60 ; 52.90
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A radiofrequency excited atomic Xe slab laser with an active volume of 2 × 10 × 300 mm3 using a quartz envelope containing the laser-gas mixture shows a stable cw performance with an output power of almost 1 W. The free-running system oscillates, depending on gas composition and density, on several lines between 1.73 and 3.51 μm. Line competition phenomena are observed. Single-line oscillation yields more than 500 mW.
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  • 32
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.90
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report on some interesting aspects of the strong influence of the unexcited vapour zone inside a heatpipe on the observation of 366.6 and 380.0 nm UV diffuse bands of sodium. For a smaller unexcited sodium vapor zone, only the 366.6 nm band is observed, while for larger unexcited volumes, both 366.6 and 380.0 nm bands can be identified. Partial reabsorption of the 366.6 nm band leading to Stokes emission as 380.0 nm band appears most likely. Reduced power dependences observed for the 366.6 nm band, an indication of the Amplified Spontaneous Emission (ASE) nature of the emission, support this analysis. A simple kinetic for the system is discussed. The results are quite general and suggest some caution in the interpretation of the data from a number of Laser-Induced Fluorescence (LIF) experiments currently being reported.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 375-379 
    ISSN: 1432-0649
    Schlagwort(e): 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The pulse width of a synchronously pumped laser chiefly depends on the available cavity bandwidth and the pump-pulse duration. A functional form of this dependence was suggested in the literature. We present an alternate relation which is supported by analytical and numerical results, as well as by experimental results, obtained by us and by others.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 381-387 
    ISSN: 1432-0649
    Schlagwort(e): 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The capability of gated saturable absorbers for single-pulse selection is studied theoretically using the classical space-time-dependent rate-equation model. The dynamics of operation is followed experimentally by the well-known pump—probe technique. Comparing the theoretical and experimental results, it is found that gated saturable absorbers can efficiently be used for pulse forming and pulse selection of pulses longer than picosecond.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 427-430 
    ISSN: 1432-0649
    Schlagwort(e): 07.60 ; 07.65 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Saturated absorption spectroscopy was applied to study the line shape of the molecular iodineX(ν″ = 0,J″ = 13,15) →B(ν′ = 43,J′ = 12, 16) transition (λ = 514.5 nm) in a transversal magnetic field as high as 0.51 T. The Zeeman structure of several hyperfine structure (hfs) components was completely resolved and a detailed study of the second-order Zeeman shift and splitting was made. The anisotropic Magnetic Susceptibility (MS) of the molecular iodine both in theB(43) (X′ = 7.3 ± 1 × 10−34 J/Oe2) and theX(0) [χ″ = (0.6 ± 1) × 10−34 J/Oe2] states as well as the isotropic MS difference [χ′0 −χ″o = (2 ± 0.2) × 10−34 J/Oe2] was measured.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 357-365 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The plasma electrode design concept is applied for the first time to an HF laser. The discharge along the surface of a dielectric (sliding discharge) is used as a plasma cathode for the main laser discharge. The laser operates at atmospheric pressure with a gas mixture of He/SF6/C3H8. Details are presented on the efficiency of energy transfer, the dependence of laser performance on circuit parameters, gas mixture, relative energy loading and time delay between the plasma electrode and main discharges. The F atom production rate is estimated from the linear dependence of the output energy on the electric charge passed through the discharge. Output energies of 600 mJ were obtained at 1.6% efficiency from a small active discharge of 108 cm3 volume and 38 cm length, while the maximum specific input and output energies were 370 J/1 and 5.7 J/1, respectively. These values compare favourably with those reported in the literature for non-chain-reaction-type gas mixtures at 1 atm pressure and demonstrate that the plasma electrode design is a powerful scheme for developing gas-discharge lasers.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 473-477 
    ISSN: 1432-0649
    Schlagwort(e): 42.10 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report on optical limiting and z-scan in CS2 as a function of the pulse duration of 10 µm TEA CO2-laser radiation. We present a comprehensive and simple model for the shape of a laser pulse transmitted through this limiting device. For the first time, we propose the use of an optical limiting device for beam shaping.
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  • 38
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report a comparative study of a pulsed as well as continuous-wave (cw) injection seeding of a Ti:Sapphire laser pumped by aQ-switched frequency-doubled Nd3+:YAG laser for achieving narrow spectral bandwidth. The results have indicated that the Ti:Sapphire laser using either a pulsed or a cw injection seeding could achieve efficient energy extraction in a narrow spectral bandwidth. In the case of pulsed injection seeding, the injection energy required for the complete injection seeding critically depended upon the timing of the Ti:Sapphire laser with respect to the delayed onset of the slave laser. On the other hand, in the case of cw injection seeding, the spectral bandwidth of the Ti:Sapphire laser was efficiently narrowed down to approximately 0.01 cm−1 with an injection power of less than 1 mW. In both types of injection seeding, characteristics observed experimentally were compared with those obtained by a numerical simulation code based on the one-dimensional rate-equation model.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 63 (1996), S. 283-292 
    ISSN: 1432-0649
    Schlagwort(e): 07.65 ; 42.60 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Theoretical and experimental results for modulation absorption spectroscopy (with simultaneous amplitude and wavelength modulations) are given, with particular emphasis on the effects of pressure and modulation broadening. As expected, such broadening effects result in a loss of resolution of nearly overlapping lines, whether these are from one or more absorbing species. The effects of phase-sensitive detection at harmonics greater than the commonly used second are investigated. It is shown that when detection is performed at higher harmonics, one is able to counter the loss of resolution due to pressure and modulation broadening. Applications in measurements of congested spectra, and in the simultaneous measurement of more than one species, are discussed. Other general characteristics of signals obtained by using higher-harmonic detection are also discussed, together with corresponding applications.
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  • 40
    ISSN: 1432-0649
    Schlagwort(e): 7.65 ; 33.00 ; 42.60 ; 42.65 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new widely tunable source in the infrared for use in high-resolution spectroscopy and trace-gas detection is described. This spectroscopic source is based on Difference Frequency Generation (DFG) in gallium selenide (GaSe) and is continuously tunable in the 8.8–15.0 μm wavelength region. Such a DFG source operates at room temperature which makes it a useful alternative to a lead-salt diode-laser- based detection system that requires cryogenic temperatures and numerous individual diode lasers.
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  • 41
    ISSN: 1432-0649
    Schlagwort(e): 33.80 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The absorption of three linesP(30) (1037.4 cm−1),P(36) (1031.5 cm−1) andP(40) (1027.4cm−1) of the pulsed CO2 laser (0001–0200 transition) by SiF4 was examined at various pulse energies, pulse durations, temperatures, optical path lengths and pressures of this compound and several non-absorbing gases. In addition, the low-intensity infrared absorption spectrum of tetrafluorosilane was compared with high-intensity absorption data for all lines of the laser. The experimental dependences demonstrate nonlinear features of the absorption phenomena originating from the high power of the incident radiation and collisions of absorbing molecules with surroundings. These effects are included in the analytical formula, being an extended form of the Lambert-Beer law. which reasonably approximates all experimental data. The importance of the results obtained for understanding general features of multiphoton absorption and for revealing potential applications of SiF4 as a sensitizer for the infrared region is presented in brief.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 59-64 
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.65 ; 78.30
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract To investigate the full conversion of pump power to the Stokes waves in stimulated Raman scattering with a single-pass cell, unconverted pump energies have been analyzed in detail in relation to the first Stokes, second Stokes and first anti-Stokes energies. Adoption of a long focusing configuration with a high-pressure cell was found to be effective but insufficient to suppress the four-wave mixing effect, because a small amount of pump energy always remained undepleted. Comparison of the results using pump beams of various spectral and spatial mode characteristics from alexandrite and Nd:YAG lasers revealed that the spatial mode quality was the most critical parameter for full depletion of a pump pulse.
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  • 43
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A technique is proposed for injection-seeding control of tunable lasers. It is based on a combination of successive external injection and intracavity self-injection of radiation when the active medium is pumped by dual-step pulses. The technique is tested both experimentally (in the case of Nd:YAG-laser-pumped pulsed dye lasers) and numerically, using a model developed by us. Full conversion of the broadband spectrum into the injected line is achieved for an output energy greater by a factor of about 50 than that managed by means of the traditional injection-seeding technique under identical conditions.
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  • 44
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 241-247 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A commercial tunable excimer laser consists of an oscillator-amplifier combination. The oscillator produces high-quality light that is sent to the amplifier and is distributed throughout the amplifier cavity via Cassegrain optics. We describe here two alternative approaches, a “single-pass” configuration for use with KrF and a “triple-pass” configuration with ArF, both of which do away with the Cassegrain optics. In each approach, the beam energy is the same as with Cassegrain optics. For KrF, the changes provide better locking, a higher degree of linear polarization, and a better spatial beam homogeneity, but a poorer beam divergence. For ArF, there is also better beam homogeneity, but the locking efficiency and divergence are not as good as with Cassegrain optics.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 273-278 
    ISSN: 1432-0649
    Schlagwort(e): 07.65 ; 42.60 ; 42.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We discuss experimental and theoretical results which show that when wavelength-modulation spectroscopy is used to monitor concentration fluctuations of gaseous species, greater sensitivity may be obtained if one uses high-order detection. We also show that, depending on the ambient concentration being monitored, there are regions in which the commonly used second derivative would show a negligible variation of signal magnitude with concentration fluctuations, whereas measurement with a higher harmonic would result in a much improved signal. Theoretical results for the measurements of any transition that can be described by the Voigt profile are given. The technique discussed is illustrated by presenting the results of measurements of wavelength-modulation spectroscopy of lines in the oxygenA band. Different detection harmonic orders are suitable for different ambient concentrations, and a related criterion that helps in the determination of a suitable detection harmonic order is given.
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  • 46
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 63 (1996), S. 585-591 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The rotating hollow cylinder glass laser is one of the approaches for the generation of high average output powers scaling to kilowatt levels from solid-state laser materials. An analytical solution of the heat conduction equation is presented for a thin wall, infinitely long glass medium, with boundary conditions given by Newton's law of cooling. The theoretical result is applied to predict thermal effects of this geometry which ultimately limit the laser performance, and the design of such a laser. A flashlamp pumped rotating Nd-doped phosphate glass hollow cylinder laser has been demonstrated. An average power output of 300 W has been achieved at 3.8% slope efficiency and 2.6% overall efficiency. Our investigation shows that the development of a kilowatt average power rotating cylinder laser is feasible.
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 63 (1996), S. 463-466 
    ISSN: 1432-0649
    Schlagwort(e): 42.60 ; 42.55.Mv
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report on the generation of intensities of 1019 W/cm−2 by focusing the output beam of a table-top hybrid dye-excimer laser system operating at 248 nm. The laser system uses a pulsed dye laser and a single, commercially available excimer gain module. Considerations and optical arrangements for the optimization of the phase-front and the beam homogeneity of ultraviolet excimer amplifiers are presented.
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 63 (1996), S. 537-540 
    ISSN: 1432-0649
    Schlagwort(e): 42.65 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We experimentally demonstrate vector phase conjugation in Cr4+:YAG saturable absorber at 1.06μm with nanosecond pulses using degenerate four-wave mixing with linearly-polarized pump beams of arbitrary strengths. The experimental results show that the phase conjugate wave produced by this method can correct depolarisation induced by a birefringent medium.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 437-442 
    ISSN: 1432-0649
    Schlagwort(e): 42.55 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Under pumping with a 990 nm, 1 W laser diode, continuous-wave (cw) tunable laser emission in the 1.5 µm wavelength range was obtained from two different colour centres: Tl0(1) in NaCl:Tl+ and (F 2 + )H in NaCl:OH−. The results are compared to those recently obtained with a similar apparatus and Tl0(1) centres in KCl:Tl+. The highest output power (30 mW) and the broadest tuning range (1.48–1.68 µm) were achieved with (F 2 + )H centres.
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 77-82 
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 81.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The direct laser writing of graduation lines in Cr thin films on glass substrates has been investigated. The Nd-YAG laser and the astigmatic optical system have been used to write rectangular holes in the Cr film. The optimal writing parameters: the laser pulse energy, the Cr layer thickness and the substrate-objective distance were determined using the optoacoustic probe beam deflection method to detect the evaporation of the material. The evaporation is concluded to be the essential process in the laser writing of graduation lines. The rims formed by the surface tension gradient at the hole edges indicate that the laser writing of graduation lines is a typical two-phase removal process.
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 62 (1996), S. 197-202 
    ISSN: 1432-0630
    Schlagwort(e): 91.60 ; 82.40 ; 42.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The process of oxide removal in crystalline Ge using a pulsed ultraviolet laser has been studied by means of real-time reflectivity measurements with nanosecond resolution. The interaction of laser radiation with a clean, oxide-free surface has been characterized and the inhomogeneous and homogeneous energy density melting thresholds of c-Ge for 193 nm radiation have been determined. The values are 180 and 370 mJ/cm2, respectively. We have demonstrated that it is possible to remove an oxide overlayer by irradiation in vacuum and to produce a surface that shows the same response to laser radiation as a smooth, oxide-free, chemically cleaned surface. Under certain specific irradiation conditions it is even possible, after removing the oxide overlayer, to produce an enhanced crystalline quality in the near-surface region compared to that obtained upon chemical cleaning as evidenced by Rutherford backscattering/channeling measurements.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 63 (1996), S. 505-508 
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 81.40Z ; 81.60Z
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Ablation of submicron structures on copper and silicon by short ultraviolet laser pulses (0.5–50 ps, 248 nm) is presented. Features like periodic line structures with a line-spacing below 400 nm, and holes with characteristic sizes well below 1 µm are produced on the sample surface by single laser shot exposure. The structures are projection printed by a Schwarzschild-objective (N.A.=0.4) in air environment. The morphology of ablation sites made with different pulse durations (0.5 ps, 5 ps, 50 ps) is discussed in terms of thermal diffusion effects.
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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 63 (1996), S. 337-339 
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 81.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Surface topology changes in polyimide induced by single UV-laser pulses with pulse durations between 140 ns and 5 μs are investigated by means of atomic force microscopy. With increasing fluence three different regimes are found: (a) real material removal (ablation), (b) swelling of the irradiated area above the level of the untreated surface (hump formation) and (c) lowering of the irradiated area below the level of the untreated surface (dent formation). A detailed description of these topology changes is given and different formation processes are discussed.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 63 (1996), S. 87-90 
    ISSN: 1432-0630
    Schlagwort(e): 42.60 ; 81.60
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Single-shot laser ablation of polyimide has been investigated with UV-Ar+-laser radiation (λ = 270-315 nm) for pulse lengths between 140 ns and 5 µs. The irradiated polymer surface was studied with respect to its morphology and ablated depth by means of atomic force microscopy. The dependence of the ablation threshold on laser pulse-length and intensity can be tentatively interpreted on the basis of a thermal process and a (thermal or non-thermal) mechanism which diminishes the activation energy for the desorption of species from the surface.
    Materialart: Digitale Medien
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  • 55
    ISSN: 1572-9001
    Schlagwort(e): Cobalt complexes ; potassium squarate ; crystal structure ; molecular structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Compound (I), idealized as Br4Co3O14N8C16H41 (see text), crystallizes in the triclinic space groupP¯ 1 (No. 2) with cell constants ofa=7.4470(7),b=7.9648(4),c=15.2223(8),α=96.338(4)ℴΒ=93.504(6)ℴ,γ=112.894(6)ℴ,V=821.328 å3, and d(calc; MW=1065.97,z=1)=2.155 gm-cm−3. Data (3880 total reflections) were collected over the range 2ℴ ≤ 2θ ≤ 55ℴ and corrected for absorption (Μ=63.69 cm−1) using data from Psi scans. The unexpectedly isolated compound contains a [cis-Co(en)2Br(OH)]+ cation, while the anion contains a central Co(III) surrounded by two mondentate,trans-squarato ligands, twotrans-hydroxo, and two waters. The waters and hydroxy ligands were identified by determining, experimentally, the presence and positions of their respective hydrogens. Given the need for overall electroneutrality, one squarato ligand must be a dianion (Sq2−) and the other a monoanion (SqH−); however, since the ion bearing the squarato ligands sits at an inversion center, the hydrogen of the latter must be disordered. Refinement of the heavy atoms with anisotropic thermal parameters and fixed hydrogen positions (B's fixed at) led to the finalR(F) andR W(F) factors of 0.036 and 0.042, respectively. (I) was obtained during efforts to prepare [Co(en)2(squarate)]Br by the displacement of two chloro ligands from the coordination sphere of [cis-Co(en)2Cl2]Cl by K2 (squarate) followed by addition of NaBr. Compound (I) appears to be the first example of a coordination compound in which squarate2− and squarate H− anions are present as ligands to a transition metal ion. A search of the Cambridge file (to 1992) produced no known examples of Co(III) squarates. Thus, (I) appears to also be the first example of its kind.
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  • 56
    ISSN: 1572-9001
    Schlagwort(e): Protected tripeptide ; solution structure ; crystal structure ; X-ray analysis ; NMR analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The solid-state structure of Boc-Gly-Trp-Ala-OBut was determined by single-crystal X-ray diffraction analysis. The tripeptide gave crystals belonging to the orthorhombic systemP212121 and at 122.0(5) K:a=11.0663(12),b=14.107(2),c=17.275(2) Å,V=2697.0(5) Å3Z=4,R(F)=0.0259, andR w(F)=0.0695. The peptide adopts a type-Iβ-turn in the solid state with a single, rather weak, intramolecular hydrogen bond between the Boc-CO and Ala-NH groups (N⋯O 3.082(1) Å, 〈NH⋯O 167(1)°). The conformation of the Boc-Gly-Trp-Ala-OBut peptide has also been studied by1H NMR spectroscopy. The solvent and temperature dependencies of NH chemical shifts suggests that this hydrogen bond is broken and that all amide protons are solvent exposed in CDCl3 and (CD3)2SO.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 46 (1996), S. 719-731 
    ISSN: 1572-8943
    Schlagwort(e): aromatic polyimide fiber ; as-spun fiber ; crystallization ; crystal structure ; crystal unit cell ; draw ratio ; dry-jet wet spinning ; isotropic solution ; modulus ; self-elongation ; tensile strength ; thermal shrinkage stress ; thermal shrinkage strain ; thermomechnical analysis ; triclinic ; wide angle X-ray diffraction ; zone drawing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Three aromatic polyimides based on 3,3′,4,4′-biphenyl-tetracarboxylic dianhydride (BPDA) and three different diamines 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB), 2,2′-dimethyl-4, 4′-diaminophenyl (DMB) or 3,3′-dimethylbenzidine (OTOL) have been synthesized. These polyimides are soluble in hotp-chlorophenol,m-cresol or other phenolic solvents. Fibers have been spun from isotropic solutions using a dry-jet wet spinning method. The as-spun fibers generally exhibit low tensile properties, and can be drawn at elevated temperatures (〉380° C) up to a draw ratio of 10 times. Remarkable increases in tensile strength and modulus are achieved after drawing and annealing. The crystal structures of highly drawn fibers were determinedvia wide angle X-ray diffraction (WAXD). The crystal unit cell lattices have been determined to be monoclinic for BPDA-PFMB and triclinic for both BPDA-DMB and BPDA-OTOL. Thermomechanical analysis (TMA) was used to measure thermal shrinkage stress and strain. A selfelongation has been found in the temperature region around 450°C. This phenomenon can be explained as resulting from the structural development in the fibers as evidencedvia WAXD observations.
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  • 58
    ISSN: 1572-9001
    Schlagwort(e): Betaine ; sodium perchlorate ; crystal structure ; polymeric framework
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Three crystalline complexes of sodium perchlorate with different flexible double betaines [Na 2(L1)(ClO4)(H2O) n ](ClO4) n (1), [Na 3(L2)(ClO4)3(H2O)2 n ] (2), and [Na(L 3)(CH3OH)n]-(ClO4) n ·xnH2O (x=0.25) (3) [−O2CCH2N+Me2−(CH2) n -N+Me2CH2CO2 −,n=2 L1;n=3 L2;n=4 L3] have been synthesized and characterized by single-crystal X-ray structure analysis. Complex (1) comprises tetranuclear sodium units consolidated by betaine and aqua ligands, which are bridged by half of the ClO4 − anions to form layers matching the (200) planes, the remaining uncoordinated ClO4 − anions being accommodated between adjacent layers. Complex (2) possesses a double-layer polymeric structure with the sodium atoms bridged by ligand oxygen atoms to form columns running parallel to thea axis, which are interconnected by double-betaine ligands lying parallel to theac plane. All of the ClO4 − groups and water molecules are coordinated to the metal atoms. In complex (3) the chains composed of alternating eight-membered and four-membered metallocycles are cross-linked by the betaine ligands, which lie in the (020) and (01/1) families of planes, to yield a three-dimensional network. All of the ClO4 − groups and water molcules fill the resulting infinite channels running parallel to thea axis. Two unusual carboxylate coordination modes are identified, namelyμ 3-O andhapto-3-O plushapto-2-O′ in (1) and (2), respectively.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Russian chemical bulletin 45 (1996), S. 370-375 
    ISSN: 1573-9171
    Schlagwort(e): organic conductors ; bis(ethylenedithio)tetrathiafuIvalene ; mercury halides ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A new organic semiconductor, (ET)8[Hg4C112] · 2C6H6, obtained in the ET+-HgCl 3 − -PhF system has been studied by X-ray structural analysis. Radical cations of bis(ethylenedithio)tctrathiafulvalene (ET) in the organic layer of the structure are packed in stacks ofa-type. The average angle between the planes of ET cations from adjacent stacks is 50.1°. The anionic layer is formed by four-charge centrosymmetric [Hg4Cl12]4− complexes and benzene solvate molecules. A comparative crystal-chemical study of the salts obtained by the reaction in the ET+-HgX 3 − -PhY system (where X = Cl, Br, and I; Y = F, Cl, and Br) made it possible to reveal a substantial effect of the sizes of the X and Y atoms on the composition of the salts and on the structural characteristics of the layers, which are responsible for the various conductivities of these salts.
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  • 60
    ISSN: 1573-9171
    Schlagwort(e): substituted sulfur-containing cyclopentadienes ; cyclopentadienyl zirconium complexes ; dynamic behavior ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Chelating sulfur-containing cyclopentadienyl ligand tetramethyl(2-methylthioethyl)cyclopentadiene (1), was synthesized for the first time. Its sodium (2a) and lithium (2b) derivatives were isolated in the crystalline state. Starting from compound1 some novel ZrIV complexes were prepared: [tetramethyl(2-methylthioethyl)cyclopentadienylltriclllorozirconium (3), bis[tetramethyl(2-methylthioethyl)cyclopentadienylldichlorozirconium (4), and [pentamethylcyclopentadienyll [tetramethyl(2-methylthioethyl)cyclopentadienylldichlorozirconium (5). The crystal structures of3 and5 were determined by X-ray diffraction analysis. The dynamic behavior of complex3 in various solvents was investigated by1H and13C N MR spectroscopy. The S→Zr coordination bond was shown to exist in complex3 both in the crystalline state and in solution. No coordination of this type was found in compounds4 and5.
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  • 61
    ISSN: 1573-9171
    Schlagwort(e): cyclopentadienes with oxygen-containing substituents ; cyclopentadienyl zirconium complexes ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Several novel zirconium(iv) complexes with the chelating oxygen-containing cyclopentadienyl ligand, tetramethyl(2-methoxyethyl)cyclopentadiene, have been synthesized. [η5:η1-Tetra-methyl(2-methyl)cyclopentadienyl]trichlorozirconium (2), bis[η5-tetramethyl(2-methoxyethyl)cyclopentadienyl]dichlorozirconium (3), [η5-pentamethylcyclopentadienyl][η5-tetra-methyl(2-methoxyethyl)cyclopentadienyl]dichlorozirconium (4), and [η5-tetra-methyl(2-methylthioethyl)cyclopentadienyl][η5-tetramethyl(2-methoxyethyl)-cyclopentadienyl]dichlorozirconium (5) have been prepared from the corresponding lithium cyclopentadienide (l). The crystal structure of cyclopentadienyl complex2 has been established by X-ray analysis. The coordination O→Zr bond in compound2 exists both in the crystalline state and in solutions. No coordination of this type was observed in complexes3–5. Synthesized complexes2–5 are discussed in comparison with their sulfur-containing analogs.
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Pharmaceutical research 13 (1996), S. 1003-1007 
    ISSN: 1573-904X
    Schlagwort(e): molecular simulation ; interfacial energy ; wettability ; crystal structure ; Monte Carlo method ; potential energy calculations ; contact angle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. This study describes the development and application of a molecular simulation technique for investigating the solid-liquid interface. It attempts to relate the molecular and crystal structure to the observed wettability of solids. Methods. Molecular simulations have been carried out for the crystal-water interface of a series of N-n-alkyl-D-gluconamide crystals using the Monte Carlo technique. The molecular system simulated consisted of a layer of water bounded by two crystal slabs. The interfacial potential energies were calculated for the crystal-water interactions and compared with experimental enthalpy values obtained from contact angle measurements. Results. The simulations clearly reveal the distinct hydrophilic and hydrophobic nature of the respective (010) and (010) faces of these compounds. The distribution of water at the interface observed in the simulations is in accord with the nature of the crystal faces. The calculated interfacial potential energies are in the right ball park, but consistently higher than the experimental values. The disparity, however, is justifiable, resulting from the highly simplified model simulated. Conclusions. Using the developed molecular simulation technique one can calculate the wettability of a solid given the crystal structure. This approach represents an important step towards the goal of engineering crystals with desired wettability characteristics.
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Colloid & polymer science 274 (1996), S. 1006-1011 
    ISSN: 1435-1536
    Schlagwort(e): Syndiotactic polypropylene ; cold stretching ; chain conformation ; crystal structure ; crystallization behavior
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The influence of the chain conformation on the crystallization behavior of cold-drawn syndiotactic polypropylene (sPP) has been investigated. The conformational and structural changes depending on drawing conditions and thermal treatments has been observed by x-ray diffraction, infra-red spectroscopy and modulated differential scanning calorimetry. A nucleation and crystal growth model is introduced, which explains the low crystallinity of cold-drawn sPP.
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  • 64
    ISSN: 1572-9605
    Schlagwort(e): Y0.4Pr0.6Ba2−xCaxCu3O7−δ ; superconductivity ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract Y0.4Pr0.6Ba2−xCaxCu3O7−δ polycrystalline samples were prepared and investigated. The Ca substitution led to a structural variation toward tetragonal symmetry, possibly due to the structural modification within the Cu(1)O layer. Superconductivity and metallic conduction were recovered whenx≥0.2, giving one more evidence for the existence of the ion-size effect at the Ba site.
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 26 (1996), S. 153-159 
    ISSN: 1573-1111
    Schlagwort(e): Cadmium cyanide ; crystal structure ; clathrate ; mineralomimetic chemistry ; dimethyl carbonate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Cd(CN)2·(CH3O)2CO (1) contains a mineralomimetic framework of Cd(CN)2 analogous to the low temperature form of cristobalite. The host framework is isostructural to those of previously reported Cd(CN)2·G compounds (G = CHCl2CH2Cl2, (CH3)2CHBr3). The dimethyl carbonate molecules in the adamantane-like cage display orientation disorder associated with the location of the carbonyl oxygen atom.
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  • 66
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 26 (1996), S. 119-126 
    ISSN: 1573-1111
    Schlagwort(e): Cyanocuprate(I) complex ; crystal structure ; three-dimensional framework ; bifurcated cyano group ; N-(2-aminoethyl)piperazine ; hydrogen-bond ; dimeric onium guest
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The title inclusion compound [{NH2(CH2CH2)2NCH2CH2NH2}2H][Cu4(CN)7] was obtained as single crystals from an aqueous solution containing CuCN, KCN, andN-(2-aminoethyl)piperazine. It crystallizes in the monoclinic space groupP2/n,a = 12.3829(9),b = 8.5970(9),c = 12.6633(7) Å, β = 109.984(5)°,z = 2,R = 0.035 for 2921 independent reflections. The inclusion structure is composed of the hydrogen-bonded dimeric onium guest [{NH2(CH2CH2)2NCH2CH2NH2}2H]3+ and the negatively-charged three-dimensional host [CU4(CN)7]3− in which the CN-bridged framework Cu(I) atoms are all tetrahedral. A polyacene-like one-dimensional array of hexagons cornered by Cu(I) atoms and edged by -CN- linkages is arrayed in parallel to theb axis and stacked approximately along the c axis. The Cu(I) corner shared in the one-dimensional array extends an N-coordinate CN group along the c axis to a pair of unshared Cu(I) corners for which the C end behaves as a bifurcated ligand to build up the three-dimensional host structure. The cavity is composed of two networks of the hexagons at the top and bottom and pillared by six 〉CN- groups and accommodates a dimeric guest ofN-(2-aminoethyl)piperazinium cations protonated at each 4-N with the cations being hydrogen-bonded to each other through the 2-NH2 groups sharing another H+.
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 26 (1996), S. 197-207 
    ISSN: 1573-1111
    Schlagwort(e): Crown ether ; nitromethane complex ; coordination isomers ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Single crystal X-ray diffraction analyses of two nitromethane complexes of furanotribenzo-21-crown-7 (1 and2) and the nitromethane complex of dibenzo-2l-crown-7 (3) are reported. The two nitromethane complexes1 and2 are polymorphic in that the macrocyclic ring adopts the ‘dentist's chair’ conformation in both structures, with a single nitromethane molecule coordinating to either the lower, concave (1) or upper, convex (2) face of the crown ether. Complex3 adopts an entirely different conformation with a coplanar arrangement of the crown ether oxygen atoms binding a single nitromethane molecule.
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