Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 110: Molecular Films: Morphology, Electronics, Photovoltaics

O 110.2: Vortrag

Freitag, 24. März 2017, 11:00–11:15, GER 38

Heterochiral to Homochiral Transition in Pentahelicene 2D Crystallization Induced by Second-Layer Nucleation — •Anaïs Mairena1, Laura Zoppi2, Johannes Seibel1, Alix Tröster3, Konstantin Grenader3, Manfred Parschau1, Andreas Terfort3, and Karl-Heinz Ernst1,21Empa , Dübendorf, Switzerland — 2University Zürich, Zürich, Switzerland — 3Goethe-Universität, Frankfurt, Germany

Chirality is ubiquitous in the molecular world, but the principles of intermolecular recognition are still poorly understood. A promising approach towards a better understanding of chiral interactions is the study of self-assembly of chiral molecules on surfaces with submolecular-resolution scanning tunneling microscopy.

The self-assembly of helical racemic pentahelicene ([5]H, C22H14) on Cu(111) leads,at very low coverages to formation of non-covalently-bonded homochiral dimers. At coverages close to the monolayer (ML), two distinct long-range ordered structures have been observed. They both have homochiral dimers as building blocks. One structure consists of a conglomerate of homochiral domains, while the second structure is a racemate composed of homochiral pairs with opposite handedness. At full ML coverage only the racemic structure prevails. Above ML coverage, a transition from the denser racemate phase into the less dense homochiral conglomerate phase occurs. The observation of such transition in the 1st layer, induced by 2nd layer nucleation is unprecedented in surface science. It indicates a long-range chiral communication between 2nd layer islands and other areas on the surface.

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