DFT studies towards the understanding of catalytic chiral surfaces: the adsorption of highly flexible molecules on platinum

Angelo Vargas and Alfons Baiker

ETH Zurich Institute for Chemical and Bioengineering, Switzerland

Modification of transition metal catalysts by means of chiral molecules is an efficient and elegant method for the preparation of solid materials possessing enantioselective properties. The basis of the modification process is the adsorption of the chiral modifier to the metal surface to form chiral sites, within which the critical asymmetric interactions occur. The work here presented shows the recent advances in determining the topology of surface chiral sites obtained by adsorption of natural and substituted cinchona alkaloids on platinum, and their role as hydrogen transfer mediators. The mentioned alkaloids have a remarkable conformational complexity and the deriving structural flexibility is of fundamental importance for the understanding of the mechanisms of surface chiral recognition. The role of cinchona alkaloids surface conformations will therefore be discussed in relation to the enantioselectivity achieved during the asymmetric hydrogenation of activated ketones.

Key References

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Controlling the sense of enantioselection on surfaces by conformational changes of the adsorbed modifiers. A.Vargas, D. Ferri, N. Bonalumi, T. Mallat, A. Baiker, Angew. Chem. Int. Ed. 46 (2007) 3905

Catalytic Chiral Metal Surfaces Generated by Adsorption of O-phenyl Derivatives of Cinchonidine N. Bonalumi, A. Vargas, D. Ferri, A. Baiker J. Phys. Chem. C. In press