Molecular Structure Laboratory Chemistry Department

There are currently two Bruker-AXS instruments in the facility.

The instruments in the crystallography laboratory include:

• Bruker-AXS SMART 1000 CCD area detector on a platform goniometer with a Mo fine focus sealed-tube X-ray source (aka "Britney")
• Bruker-AXS P4 diffractometer with a SMART 1K CCD area detector and a Mo normal focus sealed-tube X-ray source (aka "Yzerman")

The instruments and the laboratory can be viewed on these digital pictures.

The single-crystal instruments are controlled by separate PC computers and are equipped with nitrogen-streaming low temperature devices. Data are routinely collected at 100(2) K on Britney and at 173(2) K on Yzerman. Data are analyzed on one of six Windows NT or Windows 2000 workstations. The Bruker-AXS SHELXTL™ programs and the Cambridge Structural Database™ are the software most often used in our crystallography laboratory. back to top

The X-ray structural determination begins by determining the unit cell parameters. These parameters are checked against the data in the Cambridge Structural Database. If the unit cell parameters match an entry in the CSD then the structural determination is terminated since you know exactly what the compound is. If the unit cell is unknown, a full dataset will be acquired and your structure solved unless otherwise requested. The sample will be given a code name that consists of the first three letters of your professor's last name and a number. You will need to reference that code in the future when requesting additional X-ray information.

The final report will contain all necessary X-ray data required for incorporating the data in a future publication. Typically, there are five to eight tables that include information on unit cell parameters and structural determination, atomic coordinates, interatomic distances and angles, torsion angles, anisotropic dispalecement coefficients, hydrogen bonds, and structure factor tables. An experimental will also be included. back to top

All samples should be submitted directly to the Lab Director Dr. Ilia Guzei. It is necessary to fill out a Submission Form to accompany your sample. If you are printing the submission form from the web make sure you print both sides (a double-sided sheet if possible), but you only need to fill out page 1. The sample vials should be properly labeled and the sample name indicated on the Submission Form. It is a good idea to label the vial rather than the vial cap.

• If the sample requires special handling make sure you mention it prior to submitting the Xtals.
• If the stability of the compound is unknown - submit it as air-sensitive.
• If the crystals can contain crystallization solvent - submit them in mother liquor. If you are unsure about this - submit Xtals in mother liquor.
• If a similar structure has been determined in your group but has not been published - write down the unit cell parameters on the submission form

I STRONGLY suggest you characterize your compound by other means (NMR, IR, MS) prior to submitting the sample. If you obtain you crystals from a solution it is necessary to run an NMR of the CRYSTALS rather than the solution from which crystals were grown. The NMR spectra of the mother solution and Xtals differ more often than most people realize. Also this may help avoid disappoinment resulting from submitting a known compound. back to top

Notes and Manuals

There are several manuals and instruction files of interest to people who will be solving structure on their own when collaborating with this laboratory. Please check out our Manual page for more information. back to top

• Unit cell determination - $ 20.00.
• A complete dataset (without structural solution and refinement) - $ 100.00.
• A complete dataset, structural solution and refinement (also see Co-authorship Policy) - $ 220.00

For all datasets acquired at low temperature the cost of liquid nitrogen is billed directly to the group. For the out-of-house customers there is an extra charge of $15. back to top

Co-authorship guidelines that will be followed at the Molecular Structure Laboratory are in accord with ACA regulations and with co-authorship policies accepted at the majority of crystallographic laboratories.

If the structural information is a major part of the intellectual content of the paper, and if this information has been derived primarily by X-ray diffraction, then the crystallography should be included in the paper and the crystallographer should be considered for co-authorship. Most papers that include metric parameters (i.e. distances and angles), ORTEP diagrams, and structural discussions would fall under this classification. I am encouraging collaborators to use my expertise in structural discussion (packing, hydrogen bonds, inter/intramolecular contacts, etc.), structure comparison, and database searching for relevant compounds. I will also assist in the preparation of, and review manuscripts that include my structural data. I would like the opportunity to review all papers that include structures solved by me before they are sent off for publication.

If crystallography is used only to confirm a structure that is well established by other means (NMR, mass spec, etc.), and if no structural details are given in the paper, only an acknowledgment is more appropriate. This would occur, for example, when the relative stereochemistry of an intermediate in a complex organic synthesis has been determined, or when the crystallographic experiment was routine and structural determination was straightforward. In such cases, the crystallographer would be willing to publish the structural results of the investigation in a crystallographic journal upon mutual agreement. An acknowledgement may also suffice in the cases when the X-ray experiment was standard and the structure solution straightforward.

The guidelines above are intended to help authors prepare manuscripts, facilitate their publication, and to protect the authors of manuscripts from errors in professional presentation of crystallographic results. back to top

Please include acknowledgements to the agencies that provided funding to purchase the instruments and computers.

• Structures determined between 1992 and 1995 (before the first ccd detector) should acknowledge funds from NSF grant CHE-9105497 and the University of Wisconsin.
• Structures determined between September 1995 and September 1998 should acknowledge funds from NSF grant CHE-9310428 and the University of Wisconsin.
• Structures determined since September 1998 should acknowledge funds from NSF grant CHE-9709005 and the University of Wisconsin. back to top