Notices

Acta C publishes virtual issues on polymorphism and absolute structure

[Aspirin polymorphs]

Following up on the success of its virtual issue on polymorphism (http://journals.iucr.org/special_issues/2011/polymorphism/), Acta Crystallographica Section C is planning to publish its second virtual issue towards the end of 2012. This next issue will include papers in which an absolute structure determination (successful or unsuccessful) is reported.

The concept of virtual issues of Section C is a new initiative designed to make it easier for readers to find papers relevant to their field of interest, thus increasing the visibility and impact of those papers, and consequently the attractiveness of the journal to authors. Online publishing readily facilitates the creation of virtual issues, which can be used to bring together and highlight papers on specific topics that have recently been published in the journal. The contents page of the virtual issue then provides suitable links to the original papers.

The unambiguous determination of absolute structure, particularly where the absolute configuration of an enantiomerically pure chiral molecule is needed, is important not only for synthetic and natural product chemists, who wish to fully characterize their products, but can be a critical step for the pharmaceutical industry, where opposite enantiomers of a drug can have quite different biological properties.

One of the remaining difficulties since the introduction of the ‘Flack parameter’ [Flack, H. D. (1983). Acta Cryst. A39, 876–881] has been a reliable absolute structure determination for materials containing only light atoms (e.g. C, H, N, O) when no other chemical or physical knowledge about the chirality of a substance is available. However, there have been recent advances in methods for evaluating the contribution of resonant scattering to reflection intensities (the Friedel differences), while the advent of dual radiation CCD diffractometers means that more laboratories once again have routine access to Cu Kα radiation, thereby allowing more successful absolute structure determinations to be carried out for light-atom structures. Therefore, the results of crystal structure determinations which demonstrate new successes and remaining limitations in the field of absolute structure determination are of particular interest.

Papers that have been accepted for publication between 1 January 2011 and 30 September 2012 will be included in the issue. Authors interested in contributing new papers for this virtual issue only need to submit their papers to Section C in the usual way in the coming months. These will be published shortly after they are accepted, as normal, and then collated into the virtual issue towards the end of the year. Authors do not need to make any special request to have their paper included. To submit an article, go to http://journals.iucr.org/c/services/submit.html.