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 of T = 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.

Interface Structure and Evolution of Dinaphthothienothiophene (DNTT) Films on Noble Metal Substrates

“…In a more general context, DNTT is also of particular interest because the lack of axial symmetry introduces a chirality when molecules adsorb flat lying (so called prochirality). This potentially adds another degree of freedom and complexity to the molecular film formation, as demonstrated in previous studies …”

Growing low-dimensional supramolecular crystals directly from 3D particles

“…Besides, it was found that the generated adsorbate structures are temporally and thermally stable. Further, it can be said that the QAC arrays are chemically and mechanically resistant, [26][27][28][29][30][31][32] and can be built up within minutes or even seconds. [20][21] Additionally, previous investigations have shown, that alkyd resin can be used to seal a QAC adsorbate layer, providing a resistant protection layer without damaging the supramolecular structures.…”

“…We exemplify our approach using the organic semiconductor quinacridone (QAC), a cheap and commercially available pigment with promising electrical properties, low toxicity, excellent physical and chemical stability and biocompatibility for applications within the living organism. [26][27][28][29][30][31][32] The chemical structure of a single QAC molecule is shown in Fig. 1.…”

Doping graphene via organic solid-solid wetting deposition

“…Eberle et al / Carbon 00 (2017) 000-000 7 into account. Since QAC crystals are thermally stable up to their melting point of 390 °C [46,52], a series of tests were performed where the virgin HOPGs covered with pure γQAC powder were heated up gently to different temperatures, as to trigger the OSWD process thermally. Results in this respect revealed, though generation of no supramolecular QAC structures for temperatures up to 160 °C, however, the detection of a significant surface coverage of 83 ± 13 % for samples being further heated up to 240 °C (refer Fig.…”

“…analysing the thermal annealing of a two-dimensional surface covering formed by QAC arrays exhibiting different orientations, however using Ag(111) as the substrate material [46]. Their results revealed that for a temperature range between 550 -570 K (i.e.…”