Two-dimensional separation of [7]helicene enantiomers on Cu(111).
The adsorption of heptahelicene, a helically shaped polyaromatic hydrocarbon (C(30)H(18)), on a Cu(111) surface was studied by means of thermal desorption mass spectrometry (TDMS) and low energy electron diffraction (LEED) at temperatures between 130-1,000 K under ultrahigh vacuum (UHV) conditions. The molecule in the monolayer remains intact up to 400 K. Above that temperature it decomposes in several steps into carbon and hydrogen, desorbing subsequently as H(2). In the saturated monolayer of the racemate the enantiomers are separated into two different domains on the surface which are mirror images of each other. After adsorption of one enantiomer only, no mirror domains were observed.
Ernst
K H
KH
Swiss Federal Laboratories for Materials Testing and Research (EMPA), Surface Technologies, Dübendorf, Switzerland. karl-heinz.ernst@empa.ch
Kuster
Y
Y
Fasel
R
R
Müller
M
M
Ellerbeck
U
U