Chiral switching and chiral recognition for organic molecules on surfaces studied by UHV-STM

Trolle Linderoth

Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy

High-resolution Scanning Tunneling Microscopy under ultra-high vacuum conditions allows direct and detailed exploration of chiral adsorption and organisation for organic molecules on surfaces, including time-resolved studies of dynamic processes. Adsorption studies for the chiral amino acid cysteine on the Au(110)-(1x2) surface will be reviewed with focus on intermolecular chiral recognition in cysteine dimerisation [1] and clustering [2] as well as molecule-surface chiral recognition upon cysteine binding to chiral kink sites [3]. Secondly, recent results for the chiral ordering of a class of oligo-phenylene-ethynylenes on the Au(111) surface will be discussed [4,5]. These prochiral compounds can adsorb as both chiral and achiral surface conformers, and are surprisingly shown to be able to switch between these forms through thermally activated conformational changes after adsorption. The molecular tiling pattern is strongly correlated to the conformational chirality of the molecular constituents, and the chiral switching enables an efficient channel for chiral ordering on surfaces, termed chiral accommodation. The effects of varying molecular geometry and end-group chemistry have been systematically explored.

 

References 

[1] Chiral recognition in dimerization of adsorbed cysteine observed by scanning tunnelling microscopy, A. Kühnle, T. R. Linderoth, B. Hammer, and F. Besenbacher NATURE 415, 891 (2002).

[2] Self-assembly of Monodispersed, chiral nanoclusters of cysteine on the Au(110)-(1x2) surface, A.Kühnle, T.R. Linderoth and F. Besenbacher,  Journ. Am. Chem. Soc., 125 14680 (2003)

[3] Enantiospecific adsorption of cysteine at chiral kink sites on Au(110)-(1x2) A.Kühnle, T.R. Linderoth, and F.Besenbacher  Journ. Am. Chem. Soc. 128 1176 (2006)

[3] Chiral switching by spontaneous conformational change in adsorbed organic molecules, S. Weigelt, C. Busse, L. Petersen, E. Rauls, B. Hammer, K.V. Gothelf, F.Besenbacher, and T.R. Linderoth Nature Materials, 5 11 (2006)

[4] Chiral ordering and conformational dynamics for a class of oligo-phenylene-ethynylenes on Au(111), C. Busse,  S. Weigelt, L. Petersen, A. H. Thomsen, M. Nielsen, K. V. Gothelf, E. Lægsgaard, F. Besenbacher, and T. R. Linderoth, J. Phys. Chem. B, 111 5850 (2007)