Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 46: Organic molecules on inorganic substrates: electronic, optical and other properties – Poster
O 46.11: Poster
Tuesday, March 10, 2026, 14:00–16:00, P2
Monolayers of Thiols with Very High Dipole Moments Show Surprisingly Small Work Function Changes — Michael Gärtner1, Andreas Terfort1, and •Michael Zharnikov1,2 — 1Institut für Anorganische und Analytische Chemie, Johann Wolfgang Goethe Universität Frankfurt, 60438 Frankfurt am Main, Germany — 2Angewandte Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany
The recently introduced concept of distributed dipoles in molecular self-assembly was combined with the standard dipolar tail group decoration in the context of electrostatic engineering of surfaces and interfaces by self-assembled monolayers (SAMs). To this end, thiol-anchored molecules, containing dipolar 2,5-bipyrimidine units within their molecular backbones, were decorated with either nitrile or dimethylamino tail groups and assembled on Au(111). The directions of the distributed and tail group dipoles were aligned either upwards or downwards to the anchor to achieve the maximum effect on the work function (WF) of the substrate. Despite a dense molecular packing and an upright molecular orientation, the decoration of the bipyrimidine thiols with the tail groups not only provided no WF gain but even had a detrimental effect in the dimethylamino case. This behavior is explained by the upside-down orientation of a part of the molecules in the SAMs, driven by the minimization of the energy associated with the strong dipole-dipole interaction between the SAM-forming molecules.
Keywords: self-assembled monolayers; work function; pyrimidine