SIG #13

Special Interest Group
on Molecular Structure and Chemical Properties
of the European Crystallographic Association

Promoters: Carlo Mealli (Italy), Chick C. Wilson (UK), Fernando Lahoz (Spain)

Coordinator: Chick C. Wilson (UK)

Supporting ECA Council Individual Members: Luigi Nassimbeni (South Africa), Santiago Garcia Granda (Spain), Davide Viterbo (Italy), Claude Lecomte (France)

Aims and activities of the proposed SIG

It is no exaggeration to say that crystallography underpins much of structural chemistry. In the past four or five decades, molecular structure determination by crystallographic methods has given a tremendous push to the development of chemistry in its different branches (organic, inorganic, metallorganic, etc.). For a long time, a significant percentage of the participants at crystallographic meetings were molecular crystallographers. There are still many crystallographers operating in this area, as is evident from the many thousands of structures deposited in the CSD each year and by the growing number of diffractometers operated around the world. However, it is notable that the attendance of such crystallographers at meetings has decreased and we feel that this situation should be addressed. Molecular crystallographers are working in many of the cutting edge areas of materials design, tailoring molecular materials for physical properties etc, but often do not have a natural forum in which to present the implications of their work to best effect. In areas such as weak intermolecular interactions (crystal engineering), for example, there are quite rightly specialist interest groups representing these areas in a coherent way, reflecting the large amount of attention given to them by crystallographers. However, there is no doubt that strong covalent bonding has much more impact on chemical behavior and we believe that a forum for chemical crystallographers to explore trends in molecular structure is both timely and essential.

There is another pressing imperative for offering molecular crystallographers a coherent forum for their science. The availability of powerful equipment and software makes crystal structure solution an easy task also for the non expert, allowing many chemists to exploit X-ray methods as a characterization tool. However, most chemists have not been trained in extracting the chemical information implicit in the stereochemistry of their molecules. Obviously, this is a field for the expert crystallographer who knows how to obtain valuable information from the three-dimensionality of the structure and derive unique implications for the chemical-physical properties and reactivity of the molecules under study. Such observations can be further corroborated with a variety of interpretational approaches (statistical, quantum mechanical, electron density, etc.). This fundamental research topic should be maintained within and cultivated by the crystallographic community by providing an appropriate forum for discussion. In this manner a natural home could also be recreated for the many professional so-called service crystallographers, who provide structural results to chemists, but who also have unique structural insights to offer. By providing opportunities to discuss new and important aspects of this work at crystallographic meetings, such a forum could bring back an important group of crystallographers to the crystallographic community as a whole and enrich its life significantly.

The aim of the present SIG will be to propose appropriate themes for microsymposia where chemistry is seen through the eyes of the crystallographer. Given the diversity of interests in molecular chemistry the task is not trivial and we are of the opinion that this opportunity can be best exploited by creating a new SIG in this area, Molecular Structure and Chemical Properties.