Figure 1. Aromatic ring arrangement categories.

Phenyl rings demonstrating the aromatic ring arrangement categorized in three groups: face-to-face π-stacking, offset π-stacking and no π-stacking. To help in the interpretation of the cut-offs applied to categorize each aromatic arrangement, only the angle between the plane normal of the rings is shown (image on the right), while all other distance cut-offs are pair-wise in nature.