Acta Crystallographica Section B

Structural Science

Volume 53, Part 2 (April 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
• book reviews
• books received

research papers

Acta Cryst. (1997). B53, 189-202    [doi:10.1107/S0108768196010336]

Effect of Habit Modification on Optical and X-ray Structures of Sodium Halate Mixed Crystals: The Etiology of Anomalous Double Refraction

G. Crundwell, P. Gopalan, A. Bakulin, M. L. Peterson and B. Kahr

Synopsis: The mixed crystals of the isomorphous salts NaClO₃ and NaBrO₃ were reinvestigated by X-ray diffraction. The noncubic structures that were determined address long-standing observations of anomalous birefringence in these materials.

Acta Cryst. (1997). B53, 203-220    [doi:10.1107/S0108768196012335]

A Modulation Wave Approach to the Structural Characterization of Three New Cristobalite-Related Sodium Magnesiosilicates

R. L. Withers, C. Lobo, J. G. Thompson, S. Schmid and R. Stranger

Synopsis: The crystal structures of three new cristobalite-related sodium magnesiosilicates are determined by Rietveld refinement from X-ray powder diffraction data. Good starting models for the structures were obtained prior to refinement via a modulation wave approach based on the ideal C9 cristobalite structure type and assuming regular SiO₄ and MgO₄ tetrahedra.

Acta Cryst. (1997). B53, 221-230    [doi:10.1107/S0108768196012955]

Rutile Superstructure of Sb_0.9V_1.1O₄

A. R. Landa-Cánovas, S. Hansen and K. Ståhl

Synopsis: The structure of Sb_0.9V_1.1O₄, which presents a new rutile superstructure, is determined by means of powder X-ray diffraction, electron diffraction and high-resolution electron microscopy techniques.

Acta Cryst. (1997). B53, 231-240    [doi:10.1107/S0108768196013043]

Two Crystal Structures Towards the Discotic Columnar Mesophase of (1,4,8,11,15,18,22,25-Octahexylphthalocyaninato)nickel

M. Helliwell, A. Deacon, K. J. Moon, A. K. Powell and M. J. Cook

Synopsis: The crystal structures of the title compound at 295 and 103K show a space group difference, which gives insight into the thermotropic transition to the liquid crystal mesophase. The 103K structure was determined to high precision, using SR and a CCD detector.

Acta Cryst. (1997). B53, 241-251    [doi:10.1107/S0108768196013663]

Conformational Analysis of Macrocyclic Ether Ligands. I. 1,4,7,10-Tetraoxacyclododecane and 1,4,7,10-Tetrathiacyclododecane

P. R. Raithby, G. P. Shields and F. H. Allen

Synopsis: Results from the Cambridge Structural Database have been used to perform conformational analyses on free and metal- coordinated 12-membered oxa and thia macrocycles. Conformational classifications established using symmetry-modified Jarvis-Patrick clustering are visualized in conformational space by principal component analysis plots.

Acta Cryst. (1997). B53, 252-261    [doi:10.1107/S0108768196012918]

Inclusion Compounds of Thiourea and Peralkylated Ammonium Salts. VI. Hydrogen-Bonded Host Lattices Constructed From Thiourea and Anions of Oxalic Acid and Fumaric Acid

Q. Li and T. C. W. Mak

Synopsis: In the crystal structure of tetra-n-butylammonium hydrogen oxalate-thiourea (1/2) the quaternary ammonium ions are sandwiched between puckered layers, which are constructed from thiourea-hydrogen oxalate ribbons. Three thiourea-quaternary ammonium fumarate (or hydrogen fumarate) complexes exhibit thiourea-anion lattices which are distinctly different from one another, depending on the stoichiometries and the presence of co-crystallized water molecules.

Acta Cryst. (1997). B53, 262-271    [doi:10.1107/S010876819601292X]

New Inclusion Compounds of Selenourea with Tetraethyl- and Tetra-n-propylammonium Halides

Q. Li and T. C. W. Mak

Synopsis: New inclusion compounds are described: (C₂H₅)₄NCl.2[(NH₂)₂CSe] has a layer-type selenourea-chloride host structure, isomorphous (n-C₃H₇)₄NX.3[(NH₂)₂CSe] (X = Cl, Br) feature an open-channel network constructed from wide seleno-urea-halide ribbons and (n-C₃H₇)₄NI.3[(NH₂)₂CSe] is characterized by a composite ribbon composed of a zigzag arrangement of selenourea molecules with iodide ions attached to both sides.

Acta Cryst. (1997). B53, 272-279    [doi:10.1107/S0108768196012426]

Revision of Ferroelastic Structures of n-Heptyl- and n-Octylammonium Dihydrogen Phosphate Crystals

J. Fábry, V. Petrícek, I. Císarová and J. Kroupa

Synopsis: The title compounds are ferroelastic. Some hydrogens in the structure are involved in asymmetric hydrogen bridges, which hop between the donor and acceptor oxygens during ferroelastic switching.

Acta Cryst. (1997). B53, 280-292    [doi:10.1107/S0108768196013419]

Structures of the Optically Active Monofluoro-Substituted Mandelic Acids: Relation to Their Racemic Counterparts and Thermochemical Properties

S. Larsen and K. Marthi

Synopsis: The hydrogen-bonding pattern in the crystal structures of the three optically active monofluoromandelic acids are compared internally and with those observed in their racemic analogues. The differences in the intermolecular interactions are related to the different appearance of the binary phase diagrams of the three acids.

Acta Cryst. (1997). B53, 293-299    [doi:10.1107/S0108768196013602]

Structures and Photochemistry of Inclusion Compounds of 9,10-Dihydro-9,10-ethenoanthracene-11,12-bis(diphenylphosphine Oxide)

T. Y. Fu, Z. Liu, G. Olovsson, J. R. Scheffer and J. Trotter

Synopsis: The crystal structures of four inclusion complexes are deter- mined and correlated with their photochemical reactivity; three of the complexes crystallize in a chiral space group and irradiation of single crystals produces chiral photoproducts.

Acta Cryst. (1997). B53, 300-305    [doi:10.1107/S0108768196013614]

Structures and Photochemistry of Inclusion Compounds of 9,10-Dihydro-9,10-ethenoanthracene-11,12-bis(diphenylmethanol)

T. Y. Fu, J. R. Scheffer and J. Trotter

Synopsis: Crystal structures have been determined for inclusion complexes of the host molecule 9,10-dihydro-9,10-ethenoanthracene- 11,12-bis(diphenylmethanol), with acetone, ethanol and toluene as guest solvent molecules. Different photoproducts are obtained from solution and solid-state photolyses; the solid-state reaction involves a relatively small amount of molecular rearrangement, for which a mechanism is proposed.

Acta Cryst. (1997). B53, 306-316    [doi:10.1107/S0108768196013729]

Effects of Crystal Packing on Photoinduced Proton-Transfer Processes of 2,4-Dinitrobenzylpyridine Derivatives

S. Khatib, M. Botoshansky and Y. Eichen

Synopsis: Three new crystal structures of 2,4-dinitrobenzylpyridine derivatives reveal the correlation between their photoactivity and the - interactions between the 2,4-dinitrophenyl group and other neighboring aromatic rings.

short communications

Acta Cryst. (1997). B53, 317-322    [doi:10.1107/S010876819601381X]

The perils of Cc revisited

R. E. Marsh

Synopsis: Approximately 10% of the structures listed in the Cambridge Structural Database as belonging to space group Cc are better described in other space groups, usually C2/c. Revised space groups, cell dimensions (where necessary) and atom coordinates have been derived for 98 such entries.

book reviews

Acta Cryst. (1997). B53, 323    [doi:10.1107/S0108768197099692]

Early transition metal clusters with -donor ligands edited by M. H. Chisholm

Acta Cryst. (1997). B53, 323-324    [doi:10.1107/S0108768197099680]

Metallomesogens - synthesis, properties and applications edited by J. L. Serrano

books received

Acta Cryst. (1997). B53, 324    [doi:10.1107/S0108768197099679]

Structural electron crystallography by D. Dorset

Acta Cryst. (1997). B53, 324    [doi:10.1107/S0108768197099667]

Introduction to crystallographic statistics by U. Shmuelli

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