X-Ray Crystallography

X-ray crystallography is an analytical technique which can determine the positions of atoms in a crystal and can be used to understand the solid state structure of a molecule. In addition, the handedness of a molecule can be determined for chiral compounds.

The XRCF is equipped with two Bruker single crystal diffractometers located in BI110. A Bruker AXS D8 KAPPA four-circle diffractometer using Mo radiation from a sealed-tube X-ray generator and a Bruker AXS D8 VENTURE four-circle diffractometer using either Mo or Cu radiation from ImuS micro-sources. Both are equipped with Oxford Cryosystems crystal cooling systems. Data are routinely collected at 100K unless otherwise dictated by the experiment.

The first step in obtaining a crystal structure is to grow X-ray quality crystals. Additional information on growing single crystals can be found in the Additional Resources page. Data collection times can vary widely depending on the size and quality of the crystals. Large well formed crystals can take as little as a few hours to collect, whereas small, poor quality, or weakly diffracting crystals can take a couple of days. In general, better crystals lead to better structures and we recommend spending time growing the best crystals possible.

Wait times for data collection vary depending on the number of samples to be collected but is typically less than a week.

Two things are needed to determine a structure:

1. Single crystals of the compound. Some common crystallization techniques can be found in the Additional Resources page. Note: When bringing the crystals do not remove the crystallization liquid as this can destroy the crystals.
2. A completed XRC Sample Submission Form should be filled out and either uploaded or brought to the lab.

For Air Stable Compounds

• Fill out the XRC queue
• Bring the crystals (clearly labeled) along with a completed XRC Sample Submission Form to the lab.
  • There is a drop off table located in BI 110 on the right of the door.
  • BI 110 can be entered using the keypad. If you need the code contact the director

For Air Sensitive Compounds

• Fill out the XRC queue
• You will be contacted when the instrument is available and arrangements will be made to handle your sample in the most appropriate manner.
• A completed XRC Sample Submission Form should be brought with your crystals or filled out in the lab.

Training

Individuals are encouraged to collect their own data. Anyone interested in collecting their own data should contact the director to discuss instrument training. The first step of the training will be to take the EHS X-Ray Diffraction safety course. Once completed we will familiarize you with the collection and processing of X-ray diffraction data.

In addition to data collection, training/help with data processing/refinement, including integration, absorption correction, structure solution, refinement is available by contacting the director, for those who refine their own structures.

Michael Takase teaches Ch122 which will go through the basics of crystallography theory and practical refinement.

Data Access and Processing

• Data should not be transferred by USB drive from the instrument computer.
• All data is saved to the XRCF data server which can be accessed as a Windows network drive or using SFTP (i.e. WinSCP or FileZilla).
• The facility maintains a number of computers which can be accessed remotely or in BI 128 to process the diffraction data.

Anyone interested in access to the XRCF computers or data server should contact the director.