Supramolecular architecture of molecular crystals possessing shearing mechanical properties: columns versus layers

Abstract

The supramolecular architectures of crystals of substituted benzenes possessing shearing mechanical properties have been analyzed from the viewpoint of energy of intermolecular interactions. It is demonstrated that suggested earlier layered structure of these crystals do not correspond to the character of intermolecular interactions. Analysis of the topology of intermolecular interactions indicates that the crystals have a columnar supramolecular architecture with weak interactions between the columns. The presence of shearing mechanical properties is caused by localization of intercolumnar interactions within some layers and a relatively small (less than 12 kcal mol 21 ) barrier of shift of molecules within this layer.

Intermolecular interactions in molecular crystals: what’s in a name?

“…54 (We note that the interaction energies reported in ref. 52 for HCB are all $25% greater than the present CE-B3LYP results, but we cannot identify the origin of this difference).…”

“…51 HBB is isostructural with HCB but, unlike HCB, it only exhibits bending at elevated temperatures ($400 K). 48 These studies acknowledge the strongly anisotropic intermolecular interactions that are responsible for the mechanical behaviour of HCB, and although this anisotropy has been quantied for HCB using counterpoise- corrected BLYP-D/def2-TZVP energies for molecular pairs, 52 no comparison has been made with HBB. Here we use CE-B3LYP model energies, and the separate electrostatic and dispersion contributions, to investigate the interaction anisotropy in HCB and HBB using energy framework diagrams (Fig.…”

Is a Bent Crystal Still a Single Crystal?

“…[36][37][38][39][40][41] It is important to note that even though evolution of dislocations was not reported to occur it does not mean it did not occur. [36][37][38][39][40][41] It is important to note that even though evolution of dislocations was not reported to occur it does not mean it did not occur.…”

Energy frameworks: insights into interaction anisotropy and the mechanical properties of molecular crystals

“…20 For example, Shishkin et al concluded that the basic structural motif of substituted 1,3,5-trihalobenzenes is not a halogen bonded layer, but a strongly bonded stacked column. The present energy frameworks are less computationally demanding than energy-vector diagrams, and rather more self-explanatory.…”