Turning Powder into Single Crystals: Application of 3D Electron Diffraction to Chemical Crystallography

The use of electrons for crystallography was discovered only a few decades after the work of von Laue and the Braggs. Unlike X-ray crystallography, inorganic, organic, and biological electron crystallography were developed rather independently. Until about 2000, electron crystallography in all three fields was essentially two dimensional: mostly thin layers were investigated. This changed with the work of the groups of Ute Kolb (Uni Mainz) and of Xiaodong Zou/Sven Hovmoeller (Uni Stockholm), who produced first results in 3D electron
crystallography based on the classial rotation method. This and similar developments have their origin in the material sciences, blended with elements from the rotation method.

Single Crystal 3D Electron crystallography of organic and macromolecular compounds benefits greatly from the developments in X-ray crystallography.  E.g. profile fitting and data scaling are concepts that are unusual in the crystallography of material science. For electron diffraction, these concepts reduce the impact of dynamic scattering. My work has focused on the methods development of electron crystallography with the perspective from structural chemistry. Modern X-ray integration software like XDS, SAINT, and DIALS bring new aspects into the field of electron crystallography. These programs produce reliable structures from crystals that are minute compared to samples used in X-ray crystallography.  This talk will present the results of the nanoArgovia project "A3EDPI". We mounted a DECTRIS EIGER detector onto a transmission
electron microscope and ensured fast and reliable determination of those parameters required for data processing with XDS. With this setup we created a prototype electron diffractometer. We determined the new structure of a methylene blue derivative, and extracted the structure of paracetamol out of the powder of Grippostad, taken to the TEM directly from the pharmacy. I will also present two newly developed types of sample support that overcome the missing wedge problem.