title: Quinacridone on Ag(111): Hydrogen Bonding versus Chirality.
abstract: Quinacridone (QA) has recently gained attention as an organic semiconductor with unexpectedly high performance in organic devices. The strong intermolecular connection via hydrogen bonds is expected to promote good structural order. When deposited on a substrate, another relevant factor comes into play, namely the 2D-chirality of the quinacridone molecules adsorbed on a surface. Scanning tunneling microscopy (STM) images of monolayer quinacridone on Ag(111) deposited at room temperature reveal the formation of quasi-one-dimensional rows of parallel quinacridone molecules. These rows are segmented into short stacks of a few molecules in which adjacent, flat-lying molecules of a single handedness are linked via hydrogen bonds. After annealing to a temperature ofT= 550-570 K, which is close to the sublimation temperature of bulk quinacridone, the structure changes into a stacking of heterochiral quinacridone dimers with a markedly different intermolecular arrangement. Electron diffraction (LEED) and photoelectron emission microscopy (PEEM) data corroborate the STM findings. These results illustrate how the effects of hydrogen bonding and chirality can compete and give rise to very different (meta)stable structures of quinacridone on surfaces.
authors.affiliation: Institute of Experimental Physics, Johannes Kepler University Linz , Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Wagner
authors.affiliation: Institute of Experimental Physics, Johannes Kepler University Linz , Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Györök
authors.affiliation: Institute of Experimental Physics, Johannes Kepler University Linz , Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Daniel
authors.initials: D
authors.lastname: Huber
authors.affiliation: Institute of Experimental Physics, Johannes Kepler University Linz , Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Peter
authors.initials: P
authors.lastname: Zeppenfeld
authors.affiliation: Linz Institute for Organic Solar Cells (LIOS), Johannes Kepler University Linz , Altenberger Str. 69, 4040 Linz, Austria.
authors.forename: Eric Daniel
authors.initials: ED
authors.lastname: Głowacki