Small-molecule single crystals can be studied with molybdenum or copper radiation. The MSG X-ray Crystallography Laboratory has a Bruker SMART APEX single-crystal diffractometer that is equipped with a Mo sealed-tube x-ray source, a graphite monochromator, MonoCap collimator and a SMART APEX charge-coupled device (CCD) area detector. This instrument is located in Malott Hall and permits high-resolution (>0.78 Å) structural studies for samples having larger crystals.
A state-of-the-art high-flux Bruker MicroSTAR high-brilliance microfocus Cu rotating anode X-ray generator permits data collection to 0.78 Å resolution on much smaller microcrystals and poorly-diffracting samples. This instrument is located on KU’s West Campus and gives data comparable to a second-generation synchrotron source. It has two CCD detectors with HELIOS or HELIOS MX high-brilliance multilayer optics. One detector has a 4K PLATINUM135 CCD detector mounted on a 4-circle Kappa goniometer and the other has an APEX II CCD detector mounted on a 3-circle goniometer.
Another Bruker-Nonius Proteum diffractometer has a Bruker SMART 6000 CCD area detector mounted on a 3-circle goniometer with a Bruker-Nonius FR591 Cu rotating anode x-ray source and Montel mirror optics . All four single-crystal diffractometers have Oxford Cryostream Low Temperature units and can be used for small-molecule single-crystal studies. The three CCD detectors with Cu rotating anode x-ray sources can also be used for macromolecular/protein single-crystal studies as well as qualitative powder diffraction studies using microgram quantities of powder.
Lab clients also have access to a Bruker D8 powder diffractometer that is housed in the KU Physics Department . This system uses a sealed tube Cu x-ray source and is equipped with a 1/4 circle Huber cradle. This instrument can be used to analyze the textures of materials and to examine thin films or identify phases for larger powder samples..
Most single-crystal studies are conducted at a temperature of 100K but studies can be performed at any temperature between room temperature and 80K. The single crystal small-molecule studies range from the use of x-ray crystallography as a routine analytical tool for identifying reaction products or determining relative stereochemistry to detailed studies of bonding subtleties in complex inorganic molecules and hydrogen-bonded organic species . Absolute configuration can be routinely determined using anomalous dispersion of Cu x-rays by heavier elements. Lab personnel will crystallize samples that are difficult for users to crystallize. If necessary, they will also chemically modify the molecules to give species that form more suitable single crystals.
Although the lab always prefers to work with single-domain specimens, it routinely determines structures for twinned samples with multiple domains when single-domain crystals cannot be obtained. The lab will also arrange for synchrotron or neutron-diffraction data to be \collected at national laboratories for studies that require even more sophisticated instrumentation than that available at KU. In-house structural results can usually be obtained within a few hours of the start of data collection.