SOLVATES. CRYSTAL STRUCTURES, STATISTICS, EFFICIENCY OF CRYSTALLIZATION AND INTERACTIONS WITH DISSOLVED SUBSTANCES. Marek L. Glowka and Krystyna Kozlowska, Institute of General and Ecological Chemistry, Technical University of Lodz, ul. Zwirki 36, 90-924 Lodz, Poland

A good crystal is "to be or not to be" for an X-ray crystallographer. Getting a crystal from a friend (chemist, physicist or biologist) happens but usually we have to try hard ourselves to crystallize the "priceless" substance. As crystallization is still more art than science, it is very important to know not only solubilities of the compound but also scores of different solvents in question. Also interesting is the role of the solvent in formation of a crystal and frequency of solvate formation. The last problem is particularly important in case of active agents because solvent presence in the crystal may be dangerous for patients or makes the crystals unstable.

Is it possible to answer these important questions?

First we have looked at our crystallographic treasury, Cambridge Crystallographic Database. However, the Base is of limited help in this case, because:

-there is no information on crystallization trials from other solvents than the successful ones,

-there is no information on crystallization conditions at all (which is even worse),

-as solvates crystals often show disorder, they are frequently unpublished (crystallographic statistics is deformed),

-some groups of compounds are far more populated than others. We have also browsed through the crystallographic literature.

However laborious and tough, the task gave many practical information and surprising results, which will be presented.

The work was supported by projects No. 4.P05F.008.09 and 6.P206.005.07 from the State Committee for Scientific Research (KBN).