INTERESTING INFORMATIONS FROM MODELING AND REFINEMENT OF DISORDERED MOLECULAR STRUCTURES. Hoong-Kun Fun and K.Sivakumar, X-Ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia

Nowadays crystal structure determination of small molecules is nearly an automated process with little or no human intervention due to the availability of high speed computers and sophisticated software packages. However it is non-trivial when problems are faced in individual cases where the structure has some form of disorder. This then needs the role of a crystallographer for the careful analysis of the refinement results and to carry out the next step with reasoning. Analysis of the mode of disorder and suitably carrying out the refinement with constraints and restraints come with experience. In our laboratory, we have come across many such occasions with different types of disorder existing in the molecular structures. Some examples of disorders are those due to the conformational flexibility of certain rings and mixture of two isomorphous structures. A detailed survey of the disordered cases encountered in our laboratory and how the structures were refined will be discussed. The presentation will also include how to identify the minor conformational components present in the structure and model them to get better structural information.