The Physical Chemistry Seminar Series at ISIC is organized by Prof. Ulrich Lorenz
Unless it is otherwise specified, the seminars take place on Thursday at 16.30 in BCH 2201.
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.
By: Dr. Tim Grüne
Spin based properties, applications, and devices are commonly related to magnetic effects and to magnetic materials. However, we found that chiral organic molecules act as spin filters for photoelectrons transmission, in electron transfer, and in electron transport.
The new effect, termed Chiral Induced Spin Selectivity (CISS),, was found, among others, in bio-molecules and in bio-systems. It has interesting implications for the production of new types of spintronics devices, and on electron transfer in biological systems. Recently we found that charge polarization in chiral molecules is accompanied by spin polarization. This finding shed new light on enantio-specific interactions and it opens the possibility to construct novel methods for enantio-separation.
 Göhler, B.; Hamelbeck, V.; Markus, T.Z.; Kettner, M.; Hanne, G.F.; Vager, Z.; Naaman, R.; Zacharias, H. Science 2011, 331, 894.  Mishra, D.; Markus, T.Z.; Naaman, R.; Kettner, M.; Göhler, B.; Zacharias, H.; Friedman, N.; Sheves, M.; Fontanesi, C. PNAS, 2013, 110, 14872.  Xie, Z.; Markus, T. Z.; Cohen, S. R.; Vager, Z.; Gutierrez, R.; Naaman, R. Nano Letters, 2011, 11, 4652.  Naaman, R.; Waldeck, D.H. J. Phys. Chem. Lett. (feature) 2012, 3, 2178.  R. Naaman, D. H. Waldeck, Spintronics and Chirality: Spin Selectivity in Electron Transport Through Chiral Molecules, Ann. Rev. Phys. Chem. 2015, 66, 263–81.  O. Ben Dor, S. Yochelis, A. Radko, K. Vankayala, E. Capua, A. Capua, S.-H. Yang, L. T. Baczewski, S. S. P. Parkin, R. Naaman, and Y. Paltiel, Nat. Comm. 2017, 8:14567.  K. Michaeli, V. Varade, R. Naaman, D. Waldeck, Journal of Physics: Condensed Matter, 2017, 29, 103002.  I. Carmeli, K. S. Kumar, O. Hieflero, C. Carmeli, R. Naaman, Angew. Chemie 2014, 53, 8953.  A. Kumar, E. Capua, M. K. Kesharwani, J. M. L. Martin, E. Sitbon, D. H. Waldeck, R.Naaman, PNAS, 2017, 114, 2474.
By: Prof. Ron Naaman
Weizmann Institute of Science
To be announced
By: Prof. Richard Saykally
University of California, USA