Self-assembled supermolecules

Fig. 32. Hexameric self-assembled supermolecule involving self-recognition (198).

A secondary bond , as defined by Alcock [6-8], is an interaction between two atoms characterized by a distance longer than the sum of the covalent radii but shorter than the sum of the van der Waals radii of the corresponding atoms. Such secondary interactions are weaker than normal covalent or dative bonds, but strong enough to connect individual molecules and to modify the coordination geometry of the atoms involved. They are often present in a crystal, thus resulting in self-assembled supermolecules or supramolecular architectures. For gold complexes,... 

Metal ions with higher (>6) coordination numbers, such as lanthanides and actinides, have less predictable coordination geometries than lower-coordination-number transition metal and main group ions, while it is difficult to incorporate these ions into rationally designed self-assembled supermolecules, a number of structures have been reported. The unique electronic properties of the /-elements have been exploited in supramolecular complexes to generate functional molecular devices. ... 

The general tendency of organomercmy compounds is to form secondary-bond self-assembled supermolecules or supramolecular arrays through secondary bonds the subject will be treated in Section 4.2.1. 

A rich structural chemistry of self-assembled supermolecules is provided by or-ganoaluminum hydroxides. NMR studies have shown that hydrolysis of aluminum trialkyls, AIR3, produces dialkylaluminum hydroxides and aluminoxanes, which... 

Many organogallium-oxygen compounds are associated, self-assembled supermolecules. Their structure and chemistry have been reviewed [177-179]. 

It is worth mentioning that in [Bu GaS]6 the Ga-S interatomic distances in the six-membered rings (2.316-2.323 A) are shorter than those connecting them (2.379-2.392 A) in agreement with the view of this compound as a dimer of two authentic six-membered Gas S3 heterocycles. The facile interconversions of these cages [212] support their description as self-assembled supermolecules built from RGaS units (Scheme 3.1). 

Trinudear self-assembled supermolecules, 148, have been identified in dior-ganotin salicylaldoximates [452-454, 454a]. 

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