Volume 199, Issue 3-4

The crystal structure of 7-hydroxy-4′-methoxyisoflavone has been determined by single crystal X-ray analysis. The crystals are monoclinic, a = 3.854(1), b = 13.794(3), c = 11.955(2) Å. β = 96.30(3)°, space group P 2 1 , Z = 2. The structure was refined to R w = 0.066 by full-matrix least-squares methods, using 801 independent reflections measured with a single-crystal diffractometer. The methoxy group is slightly twisted. The γ -benzopyrone ring is almost planar and makes an angle of 134.1(2)° with the plane of the phenyl ring. The hydroxy group takes part in an intermolecular hydrogen bond.

The crystal structures of two photoisodrin addition compounds have been determined by X-ray diffraction. The structures of the compounds, a half-cage acetate and a dichloromethine adduct had previously been characterized by chemical analysis and are now confirmed. With the second there are two conformationally identical molecules in the asymmetric unit.

Crystal data: Be(IO 3 ) 2 · 2HIO 3 · 6H 2 O, M r = 818.73, orthorhombic, Pnam , a = 7.842(1), b = 8.613(1), c = 24.407(2) Å, V = 1648.5(5) Å 3 , Z = 4, D x = 3.299 g · cm −3 , Mo K α , λ = 0.70930 Å, μ = 75.7 cm −1 , F (000) = 1496, T =292 K, R = 0.030 for 3018 observed reflections with I > 3 σ ( I ). The iodic acid and iodate groups are arranged in along the b -axis corrugated slabs with the HIO 3 molecules at the crests and troughs. The channels between them are extended along the a -axis and filled with Be(H 2 O) 4 2+ cations and water molecules. All the structural fragments take part in a H-bonding scheme.

The computer program EXCALIBR (Bloss and Riess, 1973; Bloss, 1981, p. 202) has been rewritten and markedly improved. Like EXCALIBR, EXCALIBR II solves optical extinction data, as determined with a spindle stage, and determines the optic axial angle 2V and the orientation of the crystal's optical indicatrix. EXCALIBR II uses a modification to Joel's equation as a means of obtaining the optic axes of a crystal. The new algorithm eliminates the need to solve the extinction data, quartet by quartet, as the first step towards finding a solution, as required by EXCALIBR. Furthermore, EXCALIBR II successfully solves extinction data where one optic axis of a biaxial crystal is 90° to the spindle axis, an orientation that had thwarted its predecessor. EXCALIBR II also accurately determines the optical indicatrix orientation for uniaxial crystals. The new program runs 10 times faster than EXCALIBR. In addition, creating data files is simplified by free-formatted input. After solving extinction data for several different wavelengths and/or temperatures, EXCALIBR II calculates the angular change of each optic direction with wavelength and/or temperature along with the error on the angle. Using a simple t-test, it then computes a p-value to aid in the decision as to whether the optical direction truly exhibits dispersion. This is a more valid and sensitive procedure than the χ 2 test used by EXCALIBR, particularly because the covariance in each optic vector's coefficients are taken into consideration and the results are invariant to the vector's orientation.

Al(O,F) 2 crystallizes as a high temperature reaction product of fine granined Al-oxides and a PbF 2 -melt. The space group is that of rutile (TiO 2 ), P 4 2 / mnm with unit cell dimensions a = 4.627 Å, c = 3.005 Å and Z = 2. The structure refinement based on 64 independent reflections and full-matrix least-squares method yielded R = 0.0195 ( R w = 0.0102). The Alanion distances are 1.982(1) Å (equatorial) and 1.980(1) Å (apical), where the distortion of the anion-octahedron is reflected by the three different anion-anion-distances 2.579(2) Å (common edge), 2.802(2) Å, 3.005(2) Å and the equitorial angles (O,F) – Al – (O,F) within the octahedron are 81.3° and 98.7° respectively.

The crystal and molecular structures of N-formyl-C"'a-diethylglycine (1) and N-benzyloxycarbonyl-C α , α -diethylglycine (2) have been determined by X-ray diffraction techniques. The compounds possess the following parameters: (1) monoclinic, space group C 2/ c (No. 15), a = 12.062(2) Å, b = 7.675(1) Å, c = 19.609(2) Å, β = 92.0(2)°, and Z = 8; (2) monoclinic, space group P 2 1 / n (No. 14), a = 11.111(2) Å, b = 14.189(2) Å, c = 9.425(2) Å, [3 = 97.7(2)°, and Z = 4. The crystal structures were solved by direct methods. The least-squares refinements led to R values of 0.052 and 0.060 for 1595 and 1630 reflections with F ≥ 7 σ ( F ) for (1) and (2), respectively. The conformation of the C α , α -diethylglycyl residue is fully extended in the two derivatives. The dispositions of the amide group in (1) and of the urethane moiety in (2) are those commonly observed in analogous compounds.

Cation location in Co(Met) 2 (NCS) 2 has been studied by X-ray powder diffraction data, using a modification of structure solution based on the use of indexed intensities reported by Marti, Soria and Cano (1977), where calculated non-observed intensities were estimated using the LAZY-PULVERIX program. Comparison of the powder patterns for this complex with those calculated for Ni(Met) 2 (NCS) 2 indicates that these complexes are probably isotypics. The Co–S and Co–N bond lengths are consistent with the values reported in the literature.

Structural changes in YBa 2 Cu 3 O 7− δ resulting from alloying with Au, Co, Fe and Ga are studied theoretically. A bond model for the various interatomic interactions yields results indicating that the tetragonal phase seemingly observed by X-ray diffraction experiments for YBa 2 (Cu 1− x M x ) 3 O 7 (M = Co, Fe; x > 0.03) consists of differently oriented orthorhombic domains. Doping with Co, Fe, Ga causes local oxygen redistribution, domain formation and uptake of excess oxygen, whereas Au impurities induce changes of the Cu(1)–O bond lengths. A generalized mean field model including short range atomic correlations is used to investigate the effect of temperature on the ordering of oxygen atoms in the doped Cu(1) basal plane. The calculated phase diagram suggests that the macroscopically tetragonal phase observed for x > 0.03 and y ≃ 0 transforms at temperatures T < 800 K into an orthorhombic phase if the oxygen content in YBa 2 (Cu 1− x M x ) 3 O 7− y , is reduced.

The crystal and molecular structures of 4,4-diethyl-oxazolidine-2,5-dione (1) and 3-(2'-nitrophenylsulfenyl)-4,4-di- n -propyl-oxazolidine-2,5-dione (2) have been determined by X-ray diffraction. The compounds possess the following parameters: (1) monoclinic, space group P 2 1 / n (No. 14), a = 8.931(1) Å, b = 11.749(2) Å, c = 7.867(1) Å, β = 98.0(2)°, and Z = 4; (2) triclinic, space group P [unk] (No. 2), a = 12.187(2) Å, b = 9.588(1) Å, c = 7.681(1) Å, α = 72.9(2)°, β = 73.0(2)°, γ = 84.9(2)°, Z = 2. The crystal structures were solved by direct methods. The least-squares refinements led to R values of 0.040 and 0.039 for 1144 and 2068 reflections with F ≥7 σ ( F ) for (1) and (2), respectively. The molecules of (1) are linked by intermolecular N1–H1… O2 = C2 hydrogen bonds along the y direction. The difference observed between the C1–O1 and C2–O1 distances within the heterocyclic moiety of (1) is not found in (2).

The crystal structure of the title compound (5) (C 34 H 38 N 4 O 3 , M w = 550.7) has been determined by X-ray diffraction methods in order to determine the influence of the carbomethoxy group on ring V upon the aggregation behaviour of chlorophylls. The crystals are green parallelpipeds and crystallize in the orthorhombic space group P 2 1 2 1 2 1 with a = 8.120(6), b = 14.431(10), c = 24.405(8) Å, F =2860(3)Å3, Z = 4, D = 1.27 9Mg/m 3 . λ (Mo K α ) = 0.71069 Å, μ = 0.077 mm −1 , F (000) 1176, 130 K. The final R value is 0.055 for 1338 observed reflections. The molecules are closely packed by interactions of the propionic ester side chains with each other and by close contacts of the C10-meso-proton with the carbonyl group on ring V.

The crystal structure of N-ethyl-1,8-naphthalimide, (C 14 H 11 NO 2 ), has been determined at 180 K. The colourless compound crystallizes in the monoclinic space group C 2/ c with unit cell dimensions a = 6.932(1), b = 18.663(4), c = 16.469(2) Å, β = 98.04(1)°, Z = 8 and D x = 1.418 Mg m −3 . The structure was solved by direct-methods and refined by a full-matrix least-squares procedure on 753 reflections to final R = 0.056. The molecule is essentially planar with the exception of the terminal methyl group which lies to one side of the plane and the two methylene H atoms which lie to the other side. The crystal structure determination enables the rationalization of the chemical reactivity of this class of compound.

Starting with only the chemical formula, La 2 NiO 4 , the phase diagram and the various structures it contains have been modelled using bond valences. The bonding graph is generated from the formula and is mapped into 3-dimensional space to give the archetypal K 2 NiF 4 structure. The inconsistencies between the requirement that the layers in this structure be commensurate and the requirement that the two bond valence network equations (the Valence Sum Rule and the Equal Valence Rule) be satisfied, leads to the prediction that, under different conditions, one of four different structures should be found. The stoichiometric material is predicted to transform with reducing temperature from a structure in space group F 4/ mmm through one in Bmab to (possibly) one in P 4 2 / ncm . A superstructure (e.g. 2 × 3 × 1 in space group Ibam ) with a composition La 2 NiO 4.17 is predicted for samples prepared in the presence of oxygen, corresponding to the observed orthorhombic (or tetragonal) interstitial phase. The model accounts for the miscibility gap observed between the stoichiometric and oxygen rich phases and indicates that all the structures are only marginally stable with the Ni–O bonds usually in compressive strain. The predicted structures (latice parameters and atomic positions) agree with those observed (where known) to within a few picometres.