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  • Chemistry  (63)
  • Crystal structure  (6)
  • Free radicals  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Die Kristallstruktur des Calciumazid-Dihydrates (1988)
    Springer
    Monatshefte für Chemie 119 (1988), S. 921-927 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Azide ; Calcium ; Crystal structure ; Dihydrate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Single crystals of Ca(N3)2·2 H2O have been prepared from aqueous solutions at room temperature. The crystals are monoclinic,a=1 159.0 (3),b=614.2 (2),c=785.5 (2) pm, β=106.52 (2)°,Z=4, space group P21/n. The crystal structure was determined by single crystal X-ray diffraction (1 109 Mo-Kα-reflexions,R=0.052). Calcium atoms are surrounded by four azide groups and four water molecules. The coordination polyhedra are antiprism which are sharing azide groups and water molecules to form layers. The lattice constants and powder pattern agree well with values reported earlier for Ca(N3)2 · 1.5 H2O [1]. It was also shown, that Sr(N3)2 · 2 H2O is isotypic with Ca(N3)2 · 2 H2O.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00810101
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  • 2
    Digitale Medien
    Digitale Medien
    Kristallstrukturen von drei Addukten des Zinkazides mit Dimethylpyridinen (1992)
    Springer
    Monatshefte für Chemie 123 (1992), S. 325-331 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Azide ; Crystal structure ; Dimethylpyridine ; Zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Three adducts of zinc azide with 2,4-/3,4- and 3,5-dimethylpyridine (DMP), respectively, were prepared and the crystal structures determined by single crystal X-ray diffraction methods. The three compounds crystallize in the monoclinic space group P21/c withZ=4: Zn(N3)2·2,4-DMP at 300 (2) K:a=1 098.6(4),b=1 600.2(6),c=608.8(3) pm, β=102.47(3)°;R=0.071 (R w =0.056). Zn(N3)2·3,4-DMP at 103 (3) K:a=1 102.1(3),b=1 649.0(4),c=611.8(1) pm, β=104.54(2)°;R=0.055 (R w =0.051). Zn(N3)2·3,5-DMP at 97 (3) K:a=602.1(2),b=2 037.9(7),c=853.8(3) pm, β=90.77(3)°;R=0.069 (R w =0.055). The molecular geometry is similar for the three adducts, but the packing of theDMP-molecules is different. The zinc atoms are surrounded by five nitrogen atoms, four belonging to the azide groups and one to theDMP-adduct. The trigonal bipyramidal shaped ZnN5-polyhedra share common edges to form chains.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00810944
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  • 3
    Digitale Medien
    Digitale Medien
    Low-temperature structural phase transition in SrMo6S8 studied by X-ray powder diffraction (1990)
    Springer
    Monatshefte für Chemie 121 (1990), S. 505-509 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Chevrel phases ; Crystal structure ; Phase transition ; X-ray analysis ; Rietveld refinement ; Powder diffraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Temperaturabhängigkeit der Gitterparameter und die Atomlagen der Tieftemperaturphase von SrMo6S8 wurden mittels Röntgenpulverdiffraktometrie bestimmt. Die rhomboedrische Hochtemperaturmodifikation (R $$\bar 3$$ ,a rh=6.5630(3)Å, αrh=88.9982(2)°,V rh=282.55(5)Å3,T=298 K) wandelt beiT 1=135(3) K in die trikline Tieftemperaturmodifikation (P $$\bar 1$$ ,a tr=6.481(1)Å,b tr=6.572(1)Å,c tr=6.611(1)Å, αtr=89.246(4)°, βtr=89.304(4)°, γtr=88.169(4)°,V tr=281.4(2)Å3,T=20 K) um. Die trikline Deformation ist stärker ausgeprägt als in der Ca-Verbindung und ähnlich jener der Ba- and Eu-Verbindung.
    Notizen: Abstract Lattice parameters as a function of temperature for, and atomic coordinates of the low-temperature phase of, SrMo6S8 are reported from X-ray powder diffraction. The structure transforms atT 1=135(3) K from the rhombohedral high-temperature modification (R $$\bar 3$$ ,a rh=6.5630 (3) Å, αrh=88.9982(2)°,V rh=282.55(5)Å3 at 298 K) into the triclinic low-temperature modification (P $$\bar 1$$ ,a tr=6.481(1)Å,b tr=6.572(1)Å,c tr=6.611(1)Å, αtr=89.246(4)°, βtr=89.304(4)°, γtr=88.169(4)°,V tr=281.4(2)Å3 at 20K). The triclinic distortion is larger than in the Ca analogue, and similar to the Ba and Eu analogues.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00810858
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  • 4
    Digitale Medien
    Digitale Medien
    Die Kristallstruktur von Cs5Eu(N3)8 (1990)
    Springer
    Monatshefte für Chemie 121 (1990), S. 781-786 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Azide ; Cesium ; Crystal structure ; Europium ; Rare earth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The crystal structure of pentacesium octaazidoeuropiate(III), Cs5Eu(N3)8, was determined by single crystal X-ray diffraction: orthorhombic,a=16.811(4),b=16.860(5),c=16.964(3)Å, space group Pbca,Z=8, 2 310 observed reflections,R=0.048. Europium atoms are coordinated to eight azide groups, the coordination polyhedra have no azide groups in common. Four cesium atoms are surrounded by eight, one by seven azide groups. The azide groups are symmetric with mean N-N-distances of 1.17(1)Å.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00808370
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  • 5
    Digitale Medien
    Digitale Medien
    Verfeinerung der Kristallstruktur des Dicaesium-Tetraazido-Zinkates Cs2Zn(N3)4 und die Kristallstrukturen komplexer Zinkazide (1990)
    Springer
    Monatshefte für Chemie 121 (1990), S. 91-97 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Azide ; Cesium ; Crystal structure ; Zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The crystal structure of dicesium-tetraazido-zincate, Cs2Zn(N3)4, has been refined from single crystal X-ray-diffractometer data. The previously reported orthorhombic structure, consisting of isolated Zn(N3)4-tetrahedra was confirmed and improved lattice parameters and atomic distances were determined. The azide groups are asymmetric and the coordination of central nitrogen atoms to cesium was observed. A table of structure data and mean atomic distances for fourteen zinc-azide compounds is added and the structures are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00809520
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  • 6
    Digitale Medien
    Digitale Medien
    Die Kristallstruktur eines polynuklearen Co(II)-Komplexes in Cs2[Co3(N3)8] (1988)
    Springer
    Monatshefte für Chemie 119 (1988), S. 509-514 
    Details
    ISSN: 1434-4475
    Schlagwort(e): Azide ; Cesium ; Cobalt ; Complex ; Crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Cs2[Co3(N3)8] crystallizes monoclinic,a=1 123.8 (3),b=568.4 (2),c=1 542.6 (4) pm, β=107.37 (2)°, space group P21/n,Z=2. The crystal structure was determined by single crystal X-ray diffraction,R w=0.069. Coatoms are coordinated octahedrally to six azide groups and form polynuclear complexes of composition [Co3(N3)8]2−. The complex anions share edges and are connected to infinite chains running along theb-axis direction. Cesium is irregularly surrounded by azide groups.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00809202
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  • 7
    Digitale Medien
    Digitale Medien
    Intramolecular Electron Transfer between 2,5-Dimethoxy-1,4-phenylene Units in [n.n]Paracyclophane Radical Cations (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 139-148 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Paracyclophanes ; Cyclic voltammetry ; Radical cations ; ESR/ENDOR spectroscopy ; Intramolecular electron transfer ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A range of [n.n]paracyclophane radical cations (4·+-12·+), in which two 2,5-dimethoxy-1,4-phenylene units are connected by alkano bridges of varying length, have been studied by ESR and ENDOR spectroscopy. In the [2.2]- and [3.3]paracyclophane radical cations 4·+-6·+, 10·+ and 11·+ the delocalization of the unpaired electron over both π-moieties and the distinct difference between the first and second oxidation potentials, ΔE = E20 - E10, are evidence for a strong intramolecular electronic interaction between the two electrophores. The [5.5] and [7.7] species (8·+ and 9·+) are localized radical cations at low temperature (ca. 220 K). At room temperature, the higher molecular flexibility leads to a significant increase in the number of internal collisions between the electrophores, resulting in a fast (ESR time scale) intramolecular electron transfer. The intermediate [4.4]paracyclophane radical cations 7·+ and 12·+ are apparently also localized radical cations. The close interplanar distance between the two π-moieties, however, facilitates their mutual contacts. In 7·+, the intramolecular electron transfer becomes fast on the ESR time scale at room temperature; in 12·+ the transfer is fast over the temperature range 200-300 K.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    On the Homoconjugation of Two Acceptor Groups (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1615-1623 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Homoconjugation ; Cyclovoltammetry ; ESR spectroscopy ; Diketones ; Heterocycles ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Cyclovoltammetric investigations have been carried out on 3,3,6,6-tetramethylcyclohexane-1,2,4,5-tetrone (4), bicyclo-[3.2.2]nonane-6,7,8,9-tetrone (5), and several of their congeners, such as 6,13-dihydro-6,6,13,13-tetramethylquin-oxalino[2.3-b]phenazine (13), 5,10-dihydro-5,5,10,10-tetra-methylpyrazino[2,3-g]quinoxaline (17), and 6,13-dihydro-6,13-propanoquinoxalino[2,3-b]phenazine (20). For 5 and 20 a large difference (ΔE° ≥400 mV) between the first and second reduction potentials was found. The ESR results of the radical anion 20•- are in support of a strong homoconjugation. ESR studies of 4•-, 13•-, and 17•- also reveal a symmetrical displacement of the unpaired electron over both acceptor groups on the ESR time scale which, however, based on the small potential difference ΔE° ≤ 200 mV can be most likely described to a fast electron exchange.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Isomeric Tetrakis(dimethylamino)naphthalenes: Syntheses, Structure-Dependence of Basicities, Crystal Structures, and Physical Properties (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1617-1622 
    Details
    ISSN: 1434-193X
    Schlagwort(e): Tetrakis(dimethylamino)naphthalenes ; Basicity ; Hydrogen bonds ; Cyclicvoltammetry ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---For comparison to the recently described 2,3,6,7-tetrakis(dimethylamino)naphthalene (1) the three isomers 2,3, and 4 were synthesized. The basicities of this group of isomers are strongly dependent upon the different mutual orientations of the pairs of dimethylamino substituents: only the isomers 3 and, partially, 4, both with dimethylamino groups in adjacent peri-positions of the naphthalene, are strong “proton sponges”. For the isomers 1 and 2 with the same number and kind of twofold dimethylamino substituents in neighbouring ortho-positions, however, no significant basicity increase is observed. To explain this difference between the two groups of isomers it is suggested that in the ortho-pairs of 1 and 2 the C-N bonds diverge considerably, leading to an increased N···N distance and consequently to less stable [N···H···N]+ hydrogen bonds in contrast to the parallel C-N bonds in the peri-substituted isomers 3 and 4. X-ray crystal structure analyses of the bases and of some of the salts derived therefrom were solved and are discussed. Cyclic voltammetry indicates that 1 to 4 are strong electron donors, reacting easily to radical cations or dications which with suitable acids have been obtained as salts.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Structural Characterization and Magnetic Behaviour of the Ferro-Antiferromagnetic Alternating Manganese-Azido Chain [Mn(3-Et,4-Mepy)2(μ-N3)2]n (3-Et,4-Mepy = 3-Ethyl-4-methylpyridine) (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 687-691 
    Details
    ISSN: 1434-1948
    Schlagwort(e): Bridging ligands ; Manganese ; Azido bridge ; Alternating chain ; Magnetic properties ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The ligands 3-ethyl-4-methylpyridine (3-Et,4-Mepy) and azide coordinate to MnII forming an alternating chain with the formula [Mn(3-Et,4-Mepy)2(μ-N3)2]n. This compound crystallizes in the space group P-1. The compound consists of chains of octahedrally coordinated manganese atoms alternately bridged by double end-to-end (μ1,3) and double end-on (μ1,1) azido bridges, which results in a structurally and magnetically alternating chain. The 3-ethyl-4-methylpyridine ligands are arranged trans, completing the six-fold coordination spheres of the manganese atoms. The Mn-Mn distances are distinctly different: Mn(1)-Mn(1A) = 5.149(3) Å (double end-to-end azido bridge) and Mn(1)-Mn(1B) = 3.402(2) Å (double end-on azido bridge). The magnetic properties of the compound, as studied in the temperature range 300-4 K, show bulk antiferromagnetic interaction. Fitting of the magnetic data by using an equation for alternating ferro-antiferromagnetic S = 5/2 1-D systems gives the parameters JAF = -13.7(1) cm-1, JF = 2.4(1) cm-1, g = 2.036(2).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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