Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 78: Metal substrates: Adsorption of organic / bio molecules IV

O 78.6: Talk

Thursday, March 29, 2012, 17:15–17:30, A 053

Controlled rotation of single molecules and sub-angstöm determination of intrinsic molecular elasticity — •Rémy Pawlak¹, Sweetlana Fremy¹, Shigeki Kawai¹, Thilo Glatzel¹, Hongjuan Fang², Lesli-Anne Fendt², François Diederich², and Ernst Meyer¹ — ¹DepaDepartement of Physics, University of Basel, Switzerlandrtement of Physics, University of Basel, Switzerland — ²Laboratorium für Organische Chemie, ETH Zürich, Switzerland

Directed molecular repositioning is a key step towards the built-up of molecular machines. To artificially generate and control motion on a surface, molecules are generally excited by an exchange of light, chemical or electrical energy. Although the elasticity of molecular structures plays a role in all diffusion processes, such intrinsic properties are rather poorly known. Here, we explore by scanning probe microscopy directed manipulations of single porphyrin derivatives equipped with peripheral carbonitrile end groups confined on Cu(111). Using 3D-spectroscopic measurements with sub-angström precision, these chemical end-groups have been accurately identified as four reactive centers. By attaching the tip to one of them, a mechanical stress is applied until a directed motion of the whole molecule is induced. Depending on the selection of one of the CN end-groups, the molecule is either rotated clockwise or anticlockwise in a controlled way. The energy transferred between the molecule and the tip during this mechanically-induced manipulation, which is closely related to its diffusion energy, are directly quantified.