Self-Recognition. Instructed System Paradigm

In addition to high efficiency, selectivity and cooperativity, another basic feature characterizing programmed supramolecular processes is self-recognition — the recognition of like from unlike, of self from non-self — embodied in the spontaneous selection and preferential assembly of like components in a mixture. 

With respect to inorganic self-assembly this would involve preferential binding of like metal ions by like ligands in a mixture of ligands and ions. Indeed, selective formation of helicates was obtained in mixtures of oligo-bipyridine strands of type 128-131 and 148 with suitable metal ions [9.173]. 

In both experiments, the desired helicates are generated from a mixture of starting compounds by self-assembly with self-recognition it involves the spontaneous selection and preferential binding of like metal ions by like ligand strands in a mixture to selectively assemble into the corresponding helicates. 

These considerations also apply to systems where binding involves interactions other than metal coordination, such as hydrogen bonding or donor-acceptor forces. Such is the case for the chiral selection occurring in the course of the self-assembly of homochiral helical strands (Section 9.4.2) and ribbons (Section 9.4.4) through hydrogen bonding. 

Along this line of thought, selective molecular and supramolecular reagents and catalysts may be considered to function as instructed reactive species possessing the ability to perform a transformation on a given substrate in a mixture of compounds. Similar considerations hold for transport processes. 

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