Helical polymers, supramolecular assembl

A novel one-dimensional helical polymer resembling DNA and composed of heterodinuclear subunits containing Pt - Ag dative bonds has been synthesized. The design and utilization of supramolecular metal-metal bonded assemblies such as those shown above can be expected to be an area of intense research effort in the future (see Semiconductor Interfaces). 

Self-assembled structures are supramolecular assemblies of covalent backbones structured through intra- and interchain noncovalent interactions. These secondary structures arise from steric constraints and a network of weak interactions (i.e., hydrogen or Van der Waals bonding, dipole-dipole or amphiphilic interactions). Helical morphologies are stiU rarely represented in these artificial species but the control of the heHx sense, and a better knowledge of the chiral amplification mechanism, is highly desirable due to their potential use in many applications. For example, helically chiral polymers can be used as chiral stationary phases for HPLC or for catalysis. 

Chiral amphfication via the majority rule is an interesting phenomenon and has been known for covalent helical polymers.However, its history for supramolecular assembly is just short. The attempted coassembly of the enantiomers of 2 (Figure 1) is one of the first examples whose stereochemical feature follows the majority rule. 

Fig. 3 Jim Heck s models. A helical polymer backbone induced by the supramolecular column assembled from tapered dendrons jacketing the backbone (left) and a tubular helical polymer without a polymer backbone (right)...

The design and synthesis of supramolecular architectures with parallel control over shape and dimensions is a challenging task in current organic chemistry [13, 14], The information stored at a molecular level plays a key role in the process of self-assembly. Recent examples of nanoscopic supramolecular complexes from outside the dendrimer held include hydrogen-bonded rosettes [15,16], polymers [17], sandwiches [18, 19] and other complexes [20-22], helicates [23], grids [24], mushrooms [25], capsules [26] and spheres [27]. 

Hairy rigid rod polymers, in which flexible side chains are attached to a rigid core, present attractive properties [9.155]. A supramolecular version of such materials may be the triple helical supramolecular species described above (Figure 41), which presents the features of a hairy cylinder. Similarly, the components 176 and 177 bearing long R chains yield self-assembled, supramolecular hairy rigid rods. 

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