Local structure and stacking disorder of chloro(phthalocyaninato)aluminium

Abstract

Chloro(phthalocyaninato)aluminium [(CHN)AlCl, Pigment Blue 79] is a molecular compound which crystallizes in a layer structure with stacking disorder. Order-disorder theory was applied to analyse and explain the stacking disorder and to determine the symmetry operations, which generate subsequent layers from a given one. Corresponding ordered structural models were constructed and optimized by force field and dispersion-corrected density functional theory methods. The superposition of the four lowest-energy stackings lead to a structure in which every second double layer looks to be ordered; in the other double layers the molecules occupy one of two lateral positions. This calculated superposition structure agrees excellently with an (incomplete) experimental structure determined from single-crystal data. From the optimized ordered models, the stacking probabilities and the preferred local arrangements were derived. Packing effects such as the distortion of the molecules depending on the arrangement of neighbouring molecules could also be determined.

Analysis of diffuse scattering in electron diffraction data for the crystal structure determination of Pigment Orange 13, C32H24Cl2N8O2

“…Stacking faults are quite frequent in organic crystals, too. Examples include compact molecules such as tris(bicyclo[2.1.1]hexeno)benzene (Bu ¨rgi et al, 2005;Schmidt & Glinnemann, 2012), planar aromatic compounds such as the industrial hydrazone pigment Pigment Red 170 (Warshamanage et al, 2014;Teteruk et al, 2014), the pentacyclic pigment II -quinacridone (Gorelik et al, 2016), and the pyramid-shaped chloro(phthalocyaninato)aluminium (Czech et al, 2017). An unusual example is given by eniluracil, which produces a wide range of disordered structures with significant variability in physical properties, which mimics polymorphism (Copley et al, 2008).…”