Characteristics of planar and planar layer-stacked CHON-containing molecules

Abstract

Understanding the relationship between molecular composition/structure and crystal packing is a fundamental challenge in crystal engineering. Planar molecules and planar layer-stacking, as a special group of molecules and a special molecular stacking mode, respectively, occupy special positions in molecular materials. Herein, we constructed two data sets of 1612 planar CHON-containing molecules and a further 65 planar layer-stacked molecules under neither heated nor pressurized conditions, and obtained the composition and structure characteristics thereof. CO and CH molecules do not easily form planar and planar layered structures, respectively. The lowest requirement of the molecular symmetry of plane, C_s, constitutes the largest proportion for both the total planar molecules and the specially planar layer-stacked molecules. In general, high planarity tends to result in planar layer-stacking. Therein, intermolecular hydrogen bonding and the CO group appear frequently to maintain the layers. Still, they are not necessary for the stacking. Additionally, the molecules show packing coefficients (PCs) concentrated within 0.70–0.75, implying a decreasing interlayer distance accompanied by an increasing intralayer intermolecular sparsity. These characteristics of planar and planar layer-stacked CHON-containing molecules are expected to be useful for feature engineering in designing novel molecules.