issue contents

ISSN: 2052-5206

February 2013 issue

Highlighted illustration

Cover illustration: Reduction of volumes of the voids in the crystal structures of DL-alanine and L-alanine on application of 6 GPa of pressure. Yellow voids are shown within the ball-and-stick structure models. The molecules as well as the topologies and symmetries of their packings are preserved over the whole pressure range of 0-6 GPa. See Fig. 4 in Tumanov & Boldyreva [(2012), Acta Cryst. B68, 412-423].

lead articles

Acta Cryst. (2013). B69, 1-16
doi: 10.1107/S2052519212051366
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The state-of-the-art charge-flipping algorithm is summarized, and its applications to various crystallographic problems connected with structure solution are reviewed.

research papers

Acta Cryst. (2013). B69, 17-29
doi: 10.1107/S205251921205110X
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The many superstructure phases of rare-earth oxides MnO2n − 2 are rationalized in terms of the `coordination defect model'.

Acta Cryst. (2013). B69, 30-35
doi: 10.1107/S2052519213000183
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Structural transformations in superlattices of Sb and P δ-layers upon annealing were studied in low-temperature grown GaAs. The combination of Sb and P δ-layers appears to be an effective tool for spatial patterning of arsenic nanoinclusions and prevention of the defect formation in the GaAs matrix.

Acta Cryst. (2013). B69, 36-42
doi: 10.1107/S2052519212046738
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The influence of inter- and intramolecular interactions in a range of palladium(II) β-diketonato complexes, as investigated by single-crystal X-ray crystallography, is presented in relation to solid-state packing modes, bond distances, hydrogen bonds and halogen interactions, while the `Venus fly trap' parameters of the 1,5-cyclooctadiene ligand are defined as a function of its bonding to the palladium(II) metal centre.

Acta Cryst. (2013). B69, 43-54
doi: 10.1107/S2052519212050439
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The structures of four halogen pseudoterpyridine ZnII complexes are analysed for the influence of very weak intermolecular interactions on their crystal packings.

Acta Cryst. (2013). B69, 62-69
doi: 10.1107/S2052519212047410
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The reaction of isophthaloyl dichloride with methyl 6-aminonicotinate yields `3 + 3' and `4 + 4' imide-linked macrocycles with the former representing a new macrocycle class (trezimide). The role of 2-aminopyridine in imide hinge formation and ultimately macrocyclization is pivotal to this one-step synthetic route into cyclic triimides (trezimides) and tetraimides (tennimides).

Acta Cryst. (2013). B69, 70-76
doi: 10.1107/S2052519212049329
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Polymorph (I) of dimethylurea (Fdd2) is the more stable modification at room temperature, where polymorph (II) (P21212) is metastable; the thermodynamic transition temperature lies between 253 K and room temperature.

Acta Cryst. (2013). B69, 77-85
doi: 10.1107/S2052519212051147
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The crystal structure of a high-pressure monoclinic polymorph (P2111) of chlorpropamide has been determined. It is formed at ∼ 2.8 GPa on hydrostatic compression of the orthorhombic stable α-polymorph (P212121) in saturated ethanol solution.

short communications

Acta Cryst. (2013). B69, 86-89
doi: 10.1107/S2052519212051500
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For the crystal structures of oxoborates, the value of ∼ 1.2 Å can be regarded as the lower physical limit for BIII—O bond lengths. The oxoborate crystal structures with BIII—O bond lengths shorter than ∼ 1.2 Å have been found to be either doubtful or clearly erroneous.
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