Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 6: Organic/bio Molecules on Metal Surfaces I

O 6.6: Vortrag

Montag, 31. März 2014, 11:45–12:00, TRE Phy

On the role of Entropy in conformational molecular switching of porphyrins on Cu(111) — Stefanie Ditze⁴, Michael Stark⁴, Florian Buchner⁴, Andre Aichert¹, Norbert Jux², Nicola Luckas³, Andreas Görling³, Wolfgang Hieringer³, Joachim Hornegger¹, Hans-Peter Steinrück⁴, and •Hubertus Marbach⁴ — ¹Lehrstuhl für Mustererkennung — ²Lehrstuhl für Organische Chemie II — ³Lehrstuhl für Theoretische Chemie — ⁴Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen

We observe and induce conformational switching of individual molecules via scanning tunneling microscopy (STM) at and close to room temperature. 2H-5,10,15,20-Tetrakis-(3,5-di-tert-butyl)-phenylporphyrin (2HTTBPP) adsorbed on Cu(111) forms a peculiar supramolecular ordered phase: the molecules arrange in alternating rows, with two distinct appearances in STM, which are assigned to concave and convex intramolecular conformations. Around room temperature, frequent bidirectional conformational switching of individual molecules from concave to convex and vice versa is observed. From the temperature dependence, detailed insights into the energy barriers and entropic contributions of the switching processes are deduced. With this contribution, we demonstrate that entropic effects can be a decisive factor for the self-assembly and the conformational switching behaviour of molecules at these temperatures.