Supramolecular synthons homosynthons

As outlined by Desiraju, crystal engineering strategies rely on the use of supramolecular synthons , or structural units within supermolecules that can be assembled using known synthetic operations , in order to achieve favourable erystal packings. Specifically, regarding organic-based moleeules, the supramolecular synthons can exist in two main types namely, homosynthons and heterosynthons (Scheme l). 

The most successful approach to the design of cocrystals is based on the identification of reliable snpramolec-nlar heterosynthons that will form in preference to any possible homosynthon. The CSD is an essential tool for finding these synthons and assessing synthon com-petition. Nevertheless, molecules that could form identical supramolecular synthons often differ in their tendency toward cocrystal formation. The low success rate of synthon-based screening experiments (about 20%) indicates that factors other than synthon complementarity should be considered. Known cocrystals contain information about these additional influences, and statistical analysis of cocrystal structures in the CSD has been used to identify them. 

There are two types of supramolecular synthons (Formula 5.1) supramolecular homosynthons, which are formed by self-eomplementary funetional groups e.g., carboxylic add dimers) and supramoleeular heterosynthons, which are formed by different, but complementary functional groups e.g., carboxylic acids and pyridine rings). Supramolecular heterosynthons that... 

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