Acta Crystallographica Section B

Structural Science

Volume 53, Part 5 (October 1997)

Cover illustration: Contoured distribution of hydrogen bonds from N-H and O-H donors about the oxygen acceptors of the disulfate dianion. Data for the 232 hydrogen bonds (O...H > 2.62 Å) were computed from the Cambridge Structural Database and the required symmetry was applied to generate the final distribution. Courtesy of M. Verdonk and J. Cole

• research papers
• short communications
• books received

research papers

Acta Cryst. (1997). B53, 739-744    [doi:10.1107/S010876819700551X]

Electron Density in YTiO₃

J. R. Hester, K. Tomimoto, H. Noma, F. P. Okamura and J. Akimitsu

Synopsis: Room- and low-temperature experimental electron density studies of YTiO₃ provide information on interatomic interactions which may be significant for understanding the origins of ferromagnetic behaviour in that compound.

Acta Cryst. (1997). B53, 745-749    [doi:10.1107/S0108768197005739]

High-Pressure Study of h.c.p.-Argon

J. Wittlinger, R. Fischer, S. Werner, J. Schneider and H. Schulz

Synopsis: Depending on the loading procedure of diamond anvil cells, argon under pressure either crystallizes in f.c.c. or h.c.p. configurations. The elastic properties of the h.c.p. crystals are comparable to those with the f.c.c. structure.

Acta Cryst. (1997). B53, 750-761    [doi:10.1107/S0108768197005909]

Thermal Expansion of Chemical Bonds

I. D. Brown, A. Dabkowski and A. McCleary

Synopsis: Comparison of the observed thermal expansion of bonds with a semi-empirical model reveals the influence of bond strains and structural constraints in thermal expansion.

Acta Cryst. (1997). B53, 762-766    [doi:10.1107/S0108768197007842]

Radial Distribution of Electron Density in Magnetite, Fe₃O₄

S. Sasaki

Synopsis: From the observation of radial electron distributions in Fe₃O₄, the charge difference between sites A and B was found to be +0.46e, which is comparable to that between Fe³⁺ and [Fe²⁺Fe³⁺].

Acta Cryst. (1997). B53, 767-772    [doi:10.1107/S0108768197003789]

Crystal and Molecular Structure of Thiocarbonyl-ethoxo(tetraphenylporphyrinato)ruthenium(II), [Ru(TPP)(CS)(HOC₂H₅)]. A Case of Centrosymmetric-Noncentrosymmetric Ambiguity

T. J. Bartczak, K. Rachlewicz and L. Latos-Grazynski

Synopsis: The organometallic derivative of ruthenium TPP is planar with Ru^II ions forced to be in the plane of the macrocycle by the imposed crystallographic inversion symmetry.

Acta Cryst. (1997). B53, 773-779    [doi:10.1107/S0108768197005077]

[MPh₄][BPh₄], M = P, As and Sb

M. A. Lloyd and C. P. Brock

Synopsis: The salts [MPh₄][BPh₄], M = P, As and Sb, crystallize in a superlattice of the P-42₁c, Z^' = 1/4, structure known for the molecules MPh₄, M = C, Si, Ge, Sn and Pb. The basic P-42₁c arrangement is retained because the cations and anion are similar in size; the cell is enlarged to accommodate an ionic arrangement that is favorable electrostatically.

Acta Cryst. (1997). B53, 780-786    [doi:10.1107/S0108768197005089]

Retention of -4 Symmetry in Compounds Containing MAr₄ Molecules and Ions

M. A. Lloyd and C. P. Brock

Synopsis: MAr₄ molecules and ions often retain -4 symmetry in their crystals because the MAr₄ units fit together well to form columnar stacks and because the aryl groups fit together well around empty -4 sites.

Acta Cryst. (1997). B53, 787-794    [doi:10.1107/S0108768197005892]

Structure and Thermal Vibrations of Spermine Phosphate Hexahydrate from Neutron Diffraction Data at 125K

A. E. Cohen, B. M. Craven and W. T. Klooster

Synopsis: This structure may be relevant to the binding of spermine to nucleic acids since phosphate-phosphate distances are similar to those in -DNA. Neutron diffraction gives details of the H atoms, including those in an ice-like configuration of water molecules.

Acta Cryst. (1997). B53, 795-802    [doi:10.1107/S0108768197007829]

A New Study of the Acid Rhodo Complex Salt [(NH₃)₅CrOHCr(NH₃)₅]Cl₅.H₂O Shows That the Crystals are Orthorhombic

P. Harris, H. Birkedal, S. Larsen and H. U. Güdel

Synopsis: This diffraction study of the acid rhodo complex chloride salt has shown that the previously assigned tetragonal symmetry is caused by twinning and that the correct space group is P2₁2₁2₁. The presence of two independent dimers in the crystal is in agreement with the spectroscopic and magnetic measurements.

Acta Cryst. (1997). B53, 803-811    [doi:10.1107/S0108768197007775]

Structural and Thermodynamic Relationships Between Optically Active and Racemic Compounds. The Crystal Structures of Optically Active Chloro- and Bromo-Substituted 3-Hydroxy-3-phenylpropionic Acids

S. Larsen and K. Marthi

Synopsis: The crystal structures of the optically active meta chloro- and bromo-substituted 3-hydroxy-3-phenylpropionic acids are compared with their racemic counterparts. The observed structural differences are related to differences in fusion enthalpy and entropy.

Acta Cryst. (1997). B53, 812-821    [doi:10.1107/S010876819601525X]

Structural Studies of a Series of Organic Non-Linear Optical Materials

J. C. Cole, J. M. Cole, G. H. Cross, M. Farsari, J. A. K. Howard and M. Szablewski

Synopsis: Low-temperature X-ray diffraction studies of four new organic non-linear optical materials [tetracyanoquinodimethane (TCNQ) derivatives] are reported and complete a series of five related compounds. The structures demonstrate varying degrees of quinoidal and zwitterionic ground state behaviour.

Acta Cryst. (1997). B53, 822-830    [doi:10.1107/S0108768197005417]

Definitive Structural Characterization of the Conventional Low-Temperature Host Structure in Urea Inclusion Compounds

L. Yeo and K. D. M. Harris

Synopsis: Structural properties of the 1,10-dibromodecane-urea and 1,12-dibromododecane-urea inclusion compounds have been determined by single crystal X-ray diffraction for both the high- and low-temperature phases. This represents the first accurate and reliable report of the conventional low-temperature structure of urea inclusion compounds.

Acta Cryst. (1997). B53, 831-837    [doi:10.1107/S0108768197005521]

Structure Analysis of C₆₀ Low-Temperature Phase by Electron Crystallography with Cryo-TEM

T. Ogawa, S. Isoda and T. Kobayashi

Synopsis: The crystal structure of C₆₀ at liquid helium temperature was examined by electron diffraction using an imaging plate and cryo-TEM. The R factor could be reduced a certain amount by assuming a multi-component crystal.

Acta Cryst. (1997). B53, 838-842    [doi:10.1107/S0108768197005703]

Application of Wallach's Rule in a Comparison of the X-ray Crystal Structures of the Racemate and the (S) Enantiomer of (1-Hydroxy-3-phenyl-2-propenyl) Dimethylphosphonate

V. J. Blazis, K. J. Koeller, N. P. Rath and C. D. Spilling

Synopsis: X-ray structure determination of the racemate and the (S) enantiomer of (1-hydroxy-3-phenyl-2-propenyl) dimethyl- phosphonate provides an example of validating Wallach's rule. The calculated density of the racemate was found to be 6.1% greater than the (S) enantiomer.

Acta Cryst. (1997). B53, 843-848    [doi:10.1107/S0108768197006174]

Neutron Diffraction Study of Aromatic Hydrogen Bonds: 5-Ethynyl-5H-dibenzo[a,d]cyclohepten-5-ol at 20K

T. Steiner, S. A. Mason and M. Tamm

Synopsis: One of the benzyl groups accepts intermolecular hydrogen bonds from a hydroxyl and an ethynyl group, one to each face of the ring. The geometry of these interactions is precisely determined.

short communications

Acta Cryst. (1997). B53, 849    [doi:10.1107/S0108768197099606]

Li⁺/Na⁺ -alumina: a combined single-crystal neutron and X-ray diffraction study. Erratum

K. Edström, T. Gustafsson, J. O. Thomas and G. C. Farrington

Synopsis: Correction to Acta Cryst. (1997). B53 631-638.

books received

Acta Cryst. (1997). B53, 850    [doi:10.1107/S010876819709959X]

Collected works of Dorothy Crowfoot Hodgkin. Vol. I. Insulin. Vol. II. Cholestrol, penicillin and other antibiotics. Vol. III. General crystallography and essays edited by G. G. Dodson, J. P. Glusker, S. Ramaseshan and K. Venkatesan

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