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Proceedings Paper

Supramolecular chiral films
Author(s): Karl-Heinz Ernst; Roman Fasel; Y. Kuster
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Paper Abstract

The self-assembly of racemic and enantiopure Heptahelicene, a helically shaped polyaromatic hydrocarbon (C30H18), on single-crystal surfaces was studied at temperatures between 150 K and 1000 K by means of surface sensitive methods like scanning tunneling microscopy (STM), temperature programmed desorption (TPD), low-energy electron diffraction (LEED), time-of-flight secondary mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy and diffraction (XPS, XPD), and Auger electron spectroscopy (AES). On Ni(111), Ni(100) and Cu(111), the molecule remains intact up to 450 K. Above that temperature it decomposes in several steps into carbon and hydrogen, the latter desorbing subsequently as H2. The adsorption of racemic Heptahelicene on Cu(111) leads to a two-dimensional enantiomeric separation into at least 20 nm wide homochiral domains. In the first monolayer, the adsorbate-substrate complex has a geometry in which the molecule is oriented with three terminal rings parallel to the surface. After adsorption of enantiopure Heptahelicene onto the stepped Cu(332) surface, an azimuthal alignment of the molecular spirals is observed, creating a single-phase orientational order. X-ray absorption studies (NEXAFS) using synchrotron radiation show for the molecule in the saturated monolayer on Ni(100) a tilted geometry.

Paper Details

Date Published: 24 June 2002
PDF: 10 pages
Proc. SPIE 4806, Complex Mediums III: Beyond Linear Isotropic Dielectrics, (24 June 2002); doi: 10.1117/12.472991
Show Author Affiliations
Karl-Heinz Ernst, Swiss Federal Labs. for Materials Testing and Research (Switzerland)
Roman Fasel, Swiss Federal Labs. for Materials Testing Research (Switzerland)
Y. Kuster, Swiss Federal Labs. for Materials Testing Research (Switzerland)

Published in SPIE Proceedings Vol. 4806:
Complex Mediums III: Beyond Linear Isotropic Dielectrics
Akhlesh Lakhtakia; Graeme Dewar; Martin W. McCall, Editor(s)

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