Fig. 6.

Crystal structures of DPPs. The red lines indicate H-bonds. (a) Structure of DPP, viewed down the [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12] plane. The linear-chain H-bonding pattern is characteristic of all three DPPs, but only in the case of DPP are the chains parallel to one another. (b) p-Br DPP viewed down the [0 2 0] plane. The staggered head-to-tail arrangement of H-bonded chains is shared by both p-Cl DPP and p-Br DPP. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)