Figure 2
Attractive [sigma]...[pi] (green) and repulsive [pi]...[pi] (red) interactions between two aromatic rings in three different arrangements: (a) parallel face-to-face, (b) parallel, offset and (c) T-shaped. For aromatic ring arrangements (b) and (c) are energetically favourable (the resultant force is weak attraction), while (a) is unfavourable (strong repulsion).  [article HTML]

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