TY - JOUR
T1 - Crystallization of Tyrian purple (6,6′-dibromoindigo) thin films
T2 - The impact of substrate surface modifications
AU - Truger, Magdalena
AU - Jones, Andrew O F
AU - Coclite, Anna Maria
AU - Pachmajer, Stefan
AU - Kriegner, Dominik
AU - Röthel, Christian
AU - Simbrunner, Josef
AU - Salzmann, Ingo
AU - Resel, Roland
PY - 2016/8/1
Y1 - 2016/8/1
N2 - The pigment 6,6′-dibromoindigo (Tyrian purple) shows strong intermolecular hydrogen bonds and the film formation is, therefore, expected to be influenced by the polar character of the substrate surface. Thin films of Tyrian purple were prepared by physical vapor deposition on a variety of substrates with different surface energies: from highly polar silicon dioxide surfaces to hydrophobic polymer surfaces. The crystallographic properties were investigated by X-ray diffraction techniques such as X-ray reflectivity and grazing incidence X-ray diffraction. In all cases, crystallites with "standing" molecules relative to the substrate surface were observed independently of the substrate surface energy. In the case of polymer surfaces, additional crystallites are formed containing "lying" molecules with their aromatic planes parallel to the substrate surface. Small differences in the crystallographic lattice constants were observed as a function of substrate surface energy, the corresponding small changes in the molecular packing are explained by a variation of the hydrogen bond geometries. This work reveals that despite the limited influence of the surface energy on the molecular orientation, the crystalline packing of Tyrian purple within thin films is altered and slightly different structures form.
AB - The pigment 6,6′-dibromoindigo (Tyrian purple) shows strong intermolecular hydrogen bonds and the film formation is, therefore, expected to be influenced by the polar character of the substrate surface. Thin films of Tyrian purple were prepared by physical vapor deposition on a variety of substrates with different surface energies: from highly polar silicon dioxide surfaces to hydrophobic polymer surfaces. The crystallographic properties were investigated by X-ray diffraction techniques such as X-ray reflectivity and grazing incidence X-ray diffraction. In all cases, crystallites with "standing" molecules relative to the substrate surface were observed independently of the substrate surface energy. In the case of polymer surfaces, additional crystallites are formed containing "lying" molecules with their aromatic planes parallel to the substrate surface. Small differences in the crystallographic lattice constants were observed as a function of substrate surface energy, the corresponding small changes in the molecular packing are explained by a variation of the hydrogen bond geometries. This work reveals that despite the limited influence of the surface energy on the molecular orientation, the crystalline packing of Tyrian purple within thin films is altered and slightly different structures form.
KW - A1. Polymorphism
KW - A1. X-ray diffraction
KW - A3. Organic thin films
KW - B1. Hydrogen-bonded pigments
UR - http://www.scopus.com/inward/record.url?scp=84973402433&partnerID=8YFLogxK
U2 - 10.1016/j.jcrysgro.2016.05.001
DO - 10.1016/j.jcrysgro.2016.05.001
M3 - Article
AN - SCOPUS:84973402433
SN - 0022-0248
VL - 447
SP - 73
EP - 79
JO - Journal of Crystal Growth
JF - Journal of Crystal Growth
ER -