Users guide to the X-ray Diffraction Facility
at the University of Missouri- St. Louis.

            The UMSL X-ray diffraction facility is located in the Center for Nanoscience Building, a part of the Science Complex on the North campus. The facility is home to the state-of-the-art X-ray diffraction equipment for single crystal molecular structure determination as well as for powder diffraction analysis.

Please contact:
Nigam Rath (314-516-5333, rathn@umsl.edu) for single crystal sample submission
                                                            and
Frank May for submitting powder diffraction samples (314-516-5311, frank.l.may@umsl.edu).

            Single crystal X-ray Diffraction can provide detailed information about molecular structure up to atomic resolution. Using this technique it is possible to determine three-dimensional solid-state structure of organic, inorganic and organometallic compounds. Using this technique geometrical parameters such as bond angles, bond distances, torsion angles etc. can be determined precisely. Absolute structure determination can be carried out in the case of a resolved isomer of an optically active compounds. Currently, the facility is equipped with two single crystal X-ray diffraction systems with Charge Coupled Device (CCD) Area Detectors for data collection. The primary requirement for superior single crystal diffraction analysis is a good quality SINGLE CRYSTAL and there is no substitute for crystal quality. Crystals can be grown using various techniques. Some common methods of crystallization include slow evaporation, diffusion and sublimation. Some common crystal growth techniques have been described in the book Laboratory manual on Crystal Growth, by I. Tarjan and M. Matrai and on the web page: Tips for Growing Single Crystals

            An optimum single crystal should be approximately 0.1 to 0.3 mm along all the three dimensions. However, it is not possible to produce equidimensional crystals for most compounds. Depending on the nature of the sample, various crystal sizes can be accommodated for data collection. Therefore, users are advised to bring the sample to the X-ray laboratory so that the crystals can be visually screened under an optical microscope to check if they are acceptable for data collection.

            Information about stability of the crystals should be provided when submitting a sample. Air and moisture sensitive compounds, as well as crystals that tend to lose solvent of crystallization, will require special handling. These crystals can be screened and mounted (in almost all cases excepting extremely sensitive compounds) using a coating of a hydrocarbon oil (e.g., Paratone Oil). Many crystallographers have successfully used this method for handling unstable crystals. It is recommended that the users provide the sample in its mother liquor, under an inert atmosphere (nitrogen or argon) for these types of samples. Extremely sensitive crystals may need to be handled in a glove box or may have to be mounted in capillary tubes.

            It is possible to determine absolute structure of optically active compounds. The presence of a heavy atom (Z > 14) enhances the chances of determining absolute structure. Better quality data sets are required for absolute structure determination.

Form for submission of single crystal samples Please submit the sample with this form. (This form can be printed by using the print button on top of the browser)