Supramolecular Chirality and Self-Assembly

Self-assembly, self-recognition and replication may involve chiral components, as discussed on several instances above. This leads to some more general considerations about the role of molecular chirality in supramolecular species. 

Chirality is expressed on both the molecular and the supramolecular levels. Like a molecule, a supermolecule may exist in enantiomeric or diastereomeric forms. Supramolecular chirality results both from the properties of the components and from the way in which they associate. 

On the other hand, the association of two enantiomeric components yields an achiral supermolecule of meso type this may occur through a symmetrical bridging molecule in order to take care of the identical interaction sites at symmetry-related positions, as shown in the three-component supermolecule 187a the corresponding diastereomeric DL pair may also be obtained (see 187b). Thus, achiral components can associate into a chiral supermolecule and chiral components can give an achiral supermolecule. 

Molecular chirality also affects the way in which self-assembly from chiral components occurs and the nature of the resulting supermolecular architecture. Three cases may be distinguished  

Finally, one may note that catenated and knotted structures display topological chirality [8.280, 8.282c, 9.76, 9.178]. 

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