MS23-P10 Electron Crystallography greatly expands Organic and Inorganic X-ray Crystal Structure DeterminationX-ray crystallography is the main discipline in chemistry that provides the 3D
coordinates of molecules. The crystal structure is an essential aspect in many
fields in chemistry. Electrons offer a fascinating extension to X-rays. Crystals
smaller than the grains in icing sugar can be investigated too small for X-rays.
3D single crystal structures can be determinaed from powder, including cases
where crystal size affects the chemistry, like for catalysts and MOFs.
This application of electron crystallography (EC) is young and was made possible
with the adaption of the rotation method to. Many publications proof the
reliability of the coordinates from EC. Despite all these advantages, EC only
plays a niche role in structural chemistry: it accounts for much less than 1% of
all published 3D single crystal. This is in stark contrast to the number of
crystalline powders, that, like in the case of Novartis, exceeds the number of
available single crystals by a factor of 3-4.
One of the main reasons for this discrepancy could be the difference in methods
and software that are available to process and refine EC data. The combination
of PEDT and Jana2006 can improve the model R1-factor down to X-ray levels, and
produce the hydrogen atoms in a heavy atom structure with striking clarity.
However, this level of accuracy is not required for the average crystal
structure. In this presentation I report on our success to copy X-ray
crystallography onto EC. We mounted an EIGER X 1M hybrid pixel detector from
Dectris Ltd. to an electron microscope, collected data like with an inhouse
X-ray machine and used the methods many structural chemist are well familiar
with. We solved the structure of a new organic methylene blue derivative with a
unit cell volume of 9,000A3. From 17 fragments of a long needle-like crystal we
collected 60 degree wedges and processed all data sets within a few hours. The
structure solved with direct methods with default options. The data are accurate
enough to complete the model and even model a disordered BF4- solvent molecule.
We believe it is time to strongly advertise EC in all its flavours to the
Structural Chemistry community.References:
 Gruene et al. (2017), Chem. Eur. J. 24, 2384-2388
 Kolb et al. (2007), Ultramicroscopy, 107, 507-513
 Palatinus et al. (2017), Science, 355, 166-169
Keywords: (in)organic structural chemistry, electron crystallography