issue contents

ISSN: 2052-5206

June 2011 issue

Highlighted illustration

Cover illustration: The cover picture highlights an artefact in the electrostatic potential of the macrolide antibiotic roxithromycin as derived via multipole refinement of X-ray diffraction data.  Ignoring the hydrogen disorder (left) in the oxime chain leads to a falsely positive electrostatic potential there as a result of the multipole model's being flexible enough to fit the averaged electron density.  If the invariom formalism, which uses theoretical electron density, is applied to the disordered region (right) the artefact disappears.  A procedure for obtaining reliable electron density distributions in the presence of disorder has been proposed [Holstein et al. (2010). Acta Cryst. B66, 568-577].

research papers

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The crystal structure of mayenite (12CaO·7Al2O3) was determined including the local structure of the cage deformed by an O ion clathrated in two out of 12 cages.

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The superspace maximum entropy method (MEM) density in combination with structure refinements has been used to uncover the modulation in incommensurate Rb2ZnCl4 close to the lock-in transition. Modulated atomic displacement parameters (ADPs) and modulated anharmonic ADPs are found to form an intrinsic part of the modulation. Refined values for the displacement modulation function depend on the presence or absence of modulated ADPs in the model.

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A hitherto unknown phase of sodium titanate, NaTi3O6(OH)·2H2O, was identified as the intermediate species in the synthesis of TiO2 nanorods. This new phase, prepared as nanorods, was investigated by X-ray powder diffraction, thermogravimetry and high-resolution electron transmission microscopy. The structure was finally solved ab initio by electron diffraction data collected through automated diffraction tomography.

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Piezochromism in bianthrone is investigated using a combination of high-pressure single-crystal and powder diffraction, UV–vis spectroscopy and periodic density functional theory calculations.

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The structural and electronic aspects, in correlation with the hydrogen bonding, of two conformers of N-(4-methylphenyl)-N′,N′′-bis(morpholinyl) phosphoric triamide have been studied by X-ray crystallography and DFT calculations.

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The structure of the 2:1 charge-transfer complex of tetrathiafulvalene and bromanil, (C6H4S4)2–C6Br4O2, was determined at 293, 100 and 25 K. Orthogonal trimers are the building blocks of the crystal packing.

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Precise analysis of the charge-density distribution of 1-nitroindoline using R-free refinement for an optimal restraints scheme.

short communications

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The `bond valence (s)–bond length (r)' correlation reported earlier for H—O bonds has been closely approximated using the function s = (α − βr)1/γ, where α = 1.185 (10), β = 0.321 (8) and γ = 0.36.


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Obituary for Frank H. Herbstein
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