Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 20: Inorganic/Organic Interfaces: Growth III
O 20.9: Talk
Tuesday, March 17, 2015, 12:30–12:45, MA 005
Racemate versus conglomerate: Chiral pentahelicene on Cu(111) — •Anaïs Mairena1, Johannes Seibel1, Liying Ma1, Alix F. Tröster2, Konstantin Grenader2, Andreas Terfort2, and Karl-Heinz Ernst1,3 — 1Empa, Swiss Federal Laboratories for Materials Science and Technology, Dubendörf, Switzerland — 2Goethe Universität Frankfurt am Main, Germany — 3University of Zurich, Switzerland
We studied the 2D self-assembly of racemic pentahelicene ([5]H, C22H14) on Cu(111) with STM. Adsorption of [5]H leads to formation of homochiral pairs already at very low coverages, as observed with STM at 7 K. After deposition at room temperature and cooling to 50 K, two distinct long-range ordered structures have been observed at higher coverages (97% of ML). Both structures still have the homochiral pairs as building blocks. While one structure is racemic, i.e., it is composed of homochiral pairs with opposite handedness, the second structure consists of homochiral domains. At monolayer saturation coverage, only a conglomerate of homochiral domains prevails. The two types of homochiral domains are respectively tilted by + 15° and -15° compared to the Cu substrate. A surface-mediated selection mechanism is presented and discussed.