A new parameter for classification of polycyclic aromatic hydrocarbon crystalline motifs: a Hirshfeld surface investigation

作者：Schatschneider Bohdan^*; Phelps Jacob; Jezowski Sebastian

来源：CrystEngComm, 2011, 13(24): 7216-7223.

DOI：10.1039/c1ce05560g

The classical crystalline motif categorizations of polycyclic aromatic hydrocarbons (PAHs) have gained interest as of late as it was discovered that the ''defining'' crystallographic axis was not always the "shortest crystallographic axis'' as previously defined and that systems under pressure would exhibit a motif's typical axis length but not its typical interplanar angle (theta). Here we use Hirshfeld surfaces to investigate the relative percent of intermolecular close contact interactions existing within the four established crystalline PAH motifs under ambient and high pressures. It was discovered that the fraction of C center dot center dot center dot C interactions (C center dot center dot center dot C%) coupled with theta could ultimately define the structural motifs. A new parameter, the pi-degree parameter (pi degrees), which relates the amount of pi center dot center dot center dot pi interaction to the interplanar angle, was developed as a function of theta and C center dot center dot center dot C% in order to unambiguously categorize PAH motifs. A new motif, beta-herringbone (beta-HB), defining a subset of PAH structures with sigma-bound aromatic groups is defined. The new motif parameter was then used to investigate several high pressure and low temperature PAH structures and provided unambiguous motif categorization regardless of the "shortest crystallographic axis'', temperature, or pressure.

• 出版日期2011