Invited Paper SS-MoA7
Racemization and Enantioselectivity on Metal Surfaces

Monday, October 19, 2015, 4:20 pm, Room 113

The last decade has seen a dramatic increase in research into chiral surface systems, driven by the growing demand for optically pure chemicals in drug manufacturing and, hence, a desire for enantioselective heterogeneous catalysts. These avoid the problem of phase separation inherent in homogeneous enantioselective processes which are predominantly used today. So far, significant success has been achieved by modifying achiral surfaces with chiral molecules thus creating stereo-selective reaction environments [1,2]. Alternatively, intrinsically chiral metal and mineral surfaces show enantioselective behavior without such modifiers [3,4], although these mechanisms are much less well understood. In our work we use synchrotron-based spectrocopies, such as XPS and NEXAFS, alongside LEED and temperature-programmed desorption to characterize the thermal stability, bond coordination and orientation of chiral probe molecules on achiral and intrinsically chiral model catalyst surfaces. The talk will present examples of adsorption systems on both types of surfaces. Particular emphasis is on small chiral amino acids (e.g. alanine, serine), which show razemization as well as enantioselectivity at several levels depending on the substrate and the length of the side-chain of the molecule [5-8].

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[3] C.F. McFadden, P.S. Cremer, A.J. Gellman, Langmuir 12 (1996) 2483.

[4] G. A. Attard, J. Phys. Chem. B 105 (2001)

[5] G. Held, M. Gladys, Topics in Catalysis, 48 (2008) 128;

[6] T. Eralp, A. Cornish, A. Shavorskiy, G. Held, Topics in Catalysis 54 (2011) 1414

[7] T. Eralp, A. Ievins, A. Shavorskiy, S. J. Jenkins, G. Held, JACS 134 (2012) 9615.

[8] S. Baldanza, A. Cornish, R. E. J. Nicklin, Z. V. Zheleva, G. Held, Surf. Sci. 629 (2014) 114.