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Download fileInfluence of Molecular Geometry on the Adsorption Orientation for Oligophenylene-Ethynylenes on Au(111)
journal contribution
posted on 2007-10-04, 00:00 authored by Sigrid Weigelt, Carsten Busse, Morten Nielsen, Kurt V. Gothelf, Erik Lægsgaard, Flemming Besenbacher, Trolle R. LinderothThe adsorption structures formed from a class of oligophenylene-ethynylenes on Au(111) under ultrahigh
vacuum conditions is compared based on high-resolution scanning tunneling microscopy (STM) measurements.
The molecules consist of three or four benzene rings connected by ethynylene spokes and are all functionalized
identically with an aldehyde, a hydroxyl, and a bulky tert-butyl group. Compounds with the conjugated spokes
placed in the para, meta, and threefold configurations were previously found to exclusively form molecular
layers with flat-lying adsorption geometries. In contrast, the associated compound with spokes in the ortho
configuration surprisingly differs in its adsorption by forming only structures with an upright adsorption
orientation. The packing density for the structures formed by the compound with the ortho configuration is
less dense than that in conventional self-assembled monolayers while still keeping the conducting backbone
in an upright orientation. These structures are thus interesting from the perspective of performing single-molecule conduction measurements on the oligophenylene-ethynylene backbones.