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O: Fachverband Oberflächenphysik
O 19: Poster Session II: Organic molecules on inorganic substrates: Adsorption and growth II
O 19.1: Poster
Monday, March 1, 2021, 13:30–15:30, P
Stereoselective cyclodehydrogenetion of bishelicenes: preservation of handedness from helical to planar chirality — Bahaaeddin Irziqat1,2, •Aleksandra Cebrat1,2, Miloš Baljozović1, Kevin Martin3, Manfred Parschau1, Narcis Avarvari3, and Karl-Heinz Ernst1,2,4 — 1Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland — 2Department of Chemistry, University of Zurich, 8057 Zürich, Switzerland — 3Laboratoire Moltech-Anjou, CNRS-Université d'Angers, 49045 Angers, France — 4Nanosurf Laboratory, Institute of Physics, Czech Academy of Sciences, Cukrovarnická 10, Prague 6, Czechia
Here, we report the 2D chiral crystallization of 2,2'-bispentahelicene on Au(111) and its thermal-induced dehydrogenation studied with scanning tunneling microscopy. The low coverage deposition on Au(111) kept at 400 K, leads to formation of heterochiral zigzag chains of the (M,M)- and (P,P)-enantiomers along the herringbone reconstruction pattern. In the closed-packed monolayer, both enantiomers self-assemble into racemic phase. Due to its strong sterical overcrowding in its adsorbate state, the (P,M)-meso form was not observed on the surface. Upon annealing and subsequent cooling of the substrate, the characteristic twisted shape of bis[5]helicenes can no longer be observed and only 2D homochiral conglomerate domains of planar Sp- and Rp-coronocoronene can be distinguished. The transformation from helical to planar chiral molecules via dehydrogenation and loss of eight hydrogen atoms was confirmed by secondary ion mass spectrometry.