Regensburg 2013 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 52: Organic/bio Molecules on Metal Surfaces V
O 52.2: Vortrag
Mittwoch, 13. März 2013, 16:15–16:30, H38
Differences in Chiral Expression: Racemic and Enantiopure Heptahelicenes on Various Metal Surfaces — •Johannes Seibel1 and Karl-Heinz Ernst1,2 — 1Empa, Nanoscale Materials Science, Dübendorf, Switzerland, Dübendorf, Switzerland — 2University of Zürich, Zürich, Switzerland
Previous scanning tunneling microscopy (STM) studies[1,2,3] of racemic and enantiopure heptahelicenes (rac-[7H], M-[7H] or P-[7H]) on Cu(111) showed the formation of mirror domains. However, these domains consist of both enantiomers in an equal ratio and naturally, pure M- and P-[7H] form different structures. To investigate the influence of the metal surface on the two-dimensional ordering of heptahelicenes, we deposited rac-[7H] and M-[7H] on Cu(100), Ag(111) and Au(111). STM measurements reveal different expressions of chirality. On Ag(111) and Au(111) rac-[7H] forms a double-row structure similar to Cu(111), but no enantiomorphous domains are observed. Additionally, the structures of M-[7H] are very similar to the ones observed on Cu(111). In contrast to the structures on the 111-terminated surfaces containing both heptahelicene enantiomers, rac-[7H] on Cu(100) separates into enantiomorphous domains containing only M-[7H] or P-[7H], respectively.
[1] R. Fasel, M. Parschau and K.-H. Ernst, Nature 2006, 439, 449-452 [2] R. Fasel, M. Parschau and K.-H. Ernst, Angew. Chem. Int. Ed. 2003, 42, 5178-5181 [3] M. Parschau, R. Fasel and K.-H. Ernst, Cryst. Growth & Des. 2008, 8, 1890-1896