Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 29: Organic-Inorganic Hybrid Systems and Organic Films IV
O 29.7: Vortrag
Dienstag, 21. März 2017, 12:00–12:15, WIL A317
Surface-Assisted Diastereoselective Ullmann Coupling of Helicenes — •Christian Wäckerlin1, Jingyi Li1, Anaïs Mairena1, Kévin Martin2, Narcis Avarvari2, and Karl-Heinz Ernst1 — 1Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland — 2Laboratoire Moltech Anjou, Université d'Angers, Angers, France
Surfaces functionalized with covalently linked chiral molecules are highly desirable; to name two examples, for stereoselective catalysis or electron spin filtering. However, the way chiral molecules at surfaces interact with each other and assemble is still an open question. Here we report the Ullmann coupling of chiral 2-bromo[4]helicene monomers to helicene dimers on Cu(100). Such dimers can exist as three isomers, the two enantiomers [(P,P) and (M,M)] and the isomer (P,M) which is the diastereomer with respect to the two enantiomers. Using scanning tunneling microscopy (STM), we show that coupling is diastereoselective, i.e. we observe the enantiomers [(P,P) and (M,M)] but not the (P,M)-dimers. Moreover, the (P,P)- and (M,M)-dimers self-assemble and separate into enantiopure domains.