A theoretical investigation of conformational aspects of polymorphism. Part 2. Diarylamines

The crystal chemistry and torsional profiles of three polymorphic diarylamines have been compared and contrasted. Although they have similar potential energy surfaces (PESs) for the main rotatable bond, the torsional distribution of the observed polymorphs differs greatly. In particular there are reported crystal structures for some but not all of the molecules at various positions on the PES, some of which are either maxima or non-stationary points on the gas phase surface. We have explained the distribution of the observed torsion values and postulated new packing motifs based on those found in the other molecules. According to lattice energy calculations, some of these 'new polymorphs' are predicted to be more stable than those reported in the literature.