Self-sorting and Formation of Larger Assemblies

As shown in Section 5.5, bisloop or tetraloop tetra-ureas (8, 9) do not form homodimers, while monoloop compounds (e.g., 15) form selectively only one homodimer. These selectivities may be summarized as follows  

Tetra-urea molecules in which adjacent urea functions are covalently connected form only those dimers in which no overlapping of the loops occurs. 

If urea functions with bulky substituents are present, only those dimers can be formed in which the bulky residues need not thread through a loop. 

With the kind and size of loops studied so far, no exception to the first rule was found, while the situation is less clear for the second rule. The threading of a larger 

The self-assembled dendrimer carries 24 phthalimide groups (= protected amino groups) on its surface, which can be replaced also by other groups (e.g., dyes). Even larger structures should be available, using the whole spectrum of selectivities indicated above. 

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