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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 111 (1989), S. 8936-8938 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 116 (1985), S. 607-623 
    ISSN: 1434-4475
    Keywords: 3,4-Dihydropyrromethenone ; Molecular conformation of 3,4-dihydropyrromethenones ; Phytochrome model compounds ; Temperature factor analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Molekül- und Kristallstruktur der beiden racemischen diastereomeren 3,4-Dihydropyrromethenonderivate1 und2 mit Konfigurationen (Z) und (E) wurden bei 93 K (1, 2) und bei Raumtemperatur (1) bestimmt. Aus einer Analyse der kristallographisch beobachteten Temperaturfaktoren wird auf eine Pseudorotations-Flexibilität des Pyrrolidinonringes im Kristall geschlossen. In beiden Verbindungen beobachtet man eine nahezu orthogonale Orientierung der beiden Fünfringe zueinander, die der Raumerfüllung der Substituenten in Positionen 1 und 3 des Pyrrolidinonringes zugeschrieben wird.
    Notes: Abstract The molecular and crystal structures of the two racemic diastereomeric 3,4-dihydropyrromethenone derivatives1 and2 of configurations (Z) and (E) were determined at 93 K (1, 2) and at room temperature (1). From an analysis of the crystallographically observed temperature coefficients a pseudorotation flexibility of the pyrrolidinone ring in the crystal is deduced. In both compounds a nearly orthogonal arrangement between the two heterocyclic ring systems is observed, which is ascribed to the steric bulk of the substituents in positions 1 and 3 of the pyrrolidinone ring.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 118 (1987), S. 1185-1194 
    ISSN: 1434-4475
    Keywords: Linear Pentapyrrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structure of the pentapyrrin1 was determined by X-ray diffraction methodes at two temperatures (298K and 97K). It is the first structure determination of a linear polypyrrole with more than four pyrrole rings. In the crystal, the molecule is located on a crystallographic two-fold axis, which passes through the central pyrrole ring. It assumes a helical overall-conformation, which is stabilized by intramolecular hydrogen bonding. The acidic proton at the nitrogen atom of the central pyrrolic ring is disordered, being observed with half occupancy at two symmetry-equivalent positions off the crystallographic diad. Attempts to remove the disorder by cooling to 97K were unsuccessful, since no indication for a phase transition was detected.
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  • 4
    ISSN: 1434-4475
    Keywords: Crystal structure of dihydrobilatriene-abc ; Dihydrobilatriene-abc ; Molecular geometry of dihydrobilatriene-abc ; Phytochrome model compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Molekül- und Kristallstruktur der beiden 2,3-Dihydrobilatriene-abc1 und2, welche Modelle für den Phytochromchromophor repräsentieren, wurden mittels Röntgenkristallstrukturanalyse bei 97 K bestimmt. Die Kristalle des Racemats1 enthalten ungeordnete Bereiche. Die beiden Moleküle besitzenall-(Z) Konfiguration und liegen im Kristall in helikaler Konformation vor. Die aciden Wasserstoffatome sind jeweils an den Stickstoffatomen der Ringe A, C und D lokalisiert. Die in genauen Tieftemperatur-Kristallstrukturen von vier Bilatrien-abc Derivaten beobachteten molekularen Geometrien der ungesättigten Heterocyclenringe werden zusammengefaßt.
    Notes: Abstract The molecular and crystal structures of the two 2,3-dihydrobilatrienes-abc1 and2, representing model compounds for the phytochrome chromophore, were determined by X-ray crystallography at 97 K. Crystals of the racemate1 contain disordered regions. Both molecules are found to be ofall-(Z) configuration, assuming a helical conformation. The acidic hydrogen atoms are localized at the nitrogen atoms of rings A, C and D. A summary of the geometries of unsaturated five-membered rings as observed in four accurate low-temperature crystal structures of bilatrienes-abc is given.
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  • 5
    ISSN: 1434-4475
    Keywords: 5,6-Epoxy- and 5,6-7,8-bisepoxy vitamin D3 ; Stereochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Epoxidation of vitamin D3 with benzonitrile ¦H2O2¦ KHCO3 (Payne's reagent) yields exclusively the 5,6-mono-oxirane2. Further epoxidation with the same reagent gives the 5,6-7,8-bisepoxide3 a. Its stereochemistry and therefore the stereochemistry of2 was established by single crystal X-ray analysis of thep-Brbenzoate3b. Thereby for the first time a directive effect of a homoallylic hydroxyl group during thePayne-epoxidation was established.
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  • 6
    ISSN: 1434-4475
    Keywords: Vitamin D3, 5,6-7,8-10,19-trisepoxide ; X-ray analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Complete epoxidation of vitamin D3 withPayne's reagent yields exclusively a 5,6-7,8-10,19-trisepoxide. Its stereochemistry was established by single X-ray analysis of itsp-Br-benzoate.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 118 (1987), S. 727-731 
    ISSN: 1434-4475
    Keywords: Azide ; Crystal structure ; Strontium ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sr(N3)2 · OC(NH2)2 was prepared by the reaction of Sr(N3)2 with urea in aqueous solution. The crystals are monoclinic,a=12.993 (4),b=7.177 (1),c=7.896 (1) Å, β=98.98 (1)°, space group P 21/a,N=4. The crystal structure was determined by single crystal X-ray methods and refined toR w=0.086. The crystal structure consists of [SrN6O2]-antiprism which are linked to form layers parallel 001.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 119 (1988), S. 1245-1249 
    ISSN: 1434-4475
    Keywords: Azide ; Calcium ; Crystal structure ; Tetramethylammonium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract [N(CH3)4]Ca(N3)3,M=240.29, was prepared from aqueous solutions of tetramethylammoniumazide with calciumazide at 298 K. The crystals are tetragonala=936.6(7) pm,c=694.7(5)pm, space group P4/nmm,Z=2, ρ(x)=1.31Mgm−3. The crystal structure was determined by single crystal x-ray diffraction (234 Mo-Kα-reflections, μ=0.469 mm−1,R=0.064). Calcium is octahedrally coordinated to six azide groups. The octahedra are connected via azide groups to a threedimensional array with the complex ammonium ions between. The terminal nitrogen atoms of the azide groups and the methyl groups are considerably disordered.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 119 (1988), S. 509-514 
    ISSN: 1434-4475
    Keywords: Azide ; Cesium ; Cobalt ; Complex ; Crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 119 (1988), S. 921-927 
    ISSN: 1434-4475
    Keywords: Azide ; Calcium ; Crystal structure ; Dihydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
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