Charge density analysis of supramolecular crystals
Dr. Alexandre Sobolev trained as a crystallographer in Russia, ultimately developing, from an undergraduate physics background, a chemical specialization in the 'small molecule' field. He rose to the Senior Research Scientist in charge of these activities in the Laboratory of Chemical Crystallography and Structure Analysis at the L. Ya. Karpov Physico-Chemical Research Institute (Moscow) over a period of twenty years. His achievements in this field are summarized in the Cambridge Crystallographic Data Base and Inorganic Crystal Structure Database and are readily examined there, as well as in more than two hundred associated primary publications.
Dr. Sobolev moved to Australia in 1992 join with the electron density studies research group at UWA (ARC research grant), initially to participate in the construction, programming and commissioning of a 'Larsen-type' single crystal Huber four-circle X-ray diffractometer operating at about 10 K, one of the very few in the world, and the only one in the Southern Hemisphere. The machine was required for the acquisition of very high-quality data for a charge/spin-density determination project. He was associated with that activity throughout the ensuing decade, and the outcomes are recorded in the full list of his publications.
At the same time, having experience and a strong background in the field of structural crystallography and crystal chemistry, Dr. Sobolev have frequently advised the faculty of the Chemistry Discipline on the suitability of their compounds for structure determination and on the interpretation of the results.
Currently Dr. Sobolev has held a position of Research Associate in the School of Biomedical, Biomolecular and Chemical Sciences at UWA, working in the field of X-ray structure analysis, concentrating on difficult or problem structures, consulting staff, teaching crystallography to PhD-students and advanced undergraduates involved.
X-ray molecular crystal structure analysis
During last decade, Dr. Sobolev’s most fruitful recent achievements have been done in the field of structural characterization of self-assembled Host-Guest macromolecular complexes, involving the crystal chemistry of supramolecular compounds in which the number of non-hydrogen atoms in the crystallographic asymmetric unit estimated in hundreds, intermediate between small molecule and protein crystallography. Here critical problems arise, connected with the physical properties of such crystals, where the dynamics of molecules in the crystal, their full or fragmentary disorder, the presence of a large number of solvent molecules and crystalline water molecules, lead to a significant decrease in quality of experimental X-ray data and the resolution of the structure. This, in consequence, requires considerable expertise and effort during the structure solving procedure and subsequent structure refinement. In this area, considerations of strategy of the X-ray experiment on crystals of such compounds are often comparable to those for electron charge density studies.