Discrete supramolecular assemblies

Figure 84 Chiral structures—the first examples of transition-metal-based discrete supramolecular assemblies with controlled stereochemistry.

During the last decades, several studies reported the preparation of synthetic discrete supramolecular assemblies (4-8), polymers (1-9), and hybrid materials (10-12) that possess bases of nucleic acids as side groups or chain-end, which are used as precursors to conceive self-organized hybrid materials at nanometric scale. 

Despite such impressive progress, considerable challenges still lie ahead, and the more signihcant challenge is to improve the stability of G-quartet dynamic aggregates in polymeric devices such as hlms or membranes to extend (address) the transport studies at macroscopic level. Several studies reported the preparation of discrete supramolecular assemblies of nucle-obases. However, the dynamic communication between the... 

R 442 F. Iborra, P. R. Cook and D. A. Jackson, Applying Microscopy to the Analysis of Nuclear Structure and Function , Methods, 2003,29,131 R 443 E. lengo, E. Zangrando and E. Alessio, Discrete Supramolecular Assemblies of Porphyrins Mediated by Coordination Compounds , Eur. J. Inorg. Chem., 2003,13, 2371... 

Ghosh and coworkers demonstrate that discrete supramolecular assemblies can be formed from leucine-zipper peptides tethered to a dendrimer core. These give fibrous structures when two complementary discrete dendrimer-peptide assemblies are combined this is one of the first examples where both discrete and repeated assemblies can be formed using the same system (Figure 18a). 

Schmittel M, Kalsani V (2005) Functional, Discrete, Nanoscale Supramolecular Assemblies. 245 1-53... 

The aim of this book is to provide the reader with an overview of interfacial supramolecular chemistry. Supramolecular assemblies of the kind considered in this text are truly interfacial, not only because they separate solid- and solution-phase components but also because they represent the junctions where biology, chemistry, physics and engineering meet. In true interfacial supramolecular systems, individual moieties, e.g. the supporting surface and an adsorbed luminophore, interact co-operatively to produce a new function or property. In addition, these two- and three-dimensional structures remain an important step in the evolution of structure from discrete molecules, to interacting assemblies, and finally to solids. In this last chapter, the future of interfacial assemblies will be briefly considered. This discussion will focus on the possibility of integrating such assemblies into practical devices and the identification of the important scientific challenges. 

Discrete supramolecular Pc-porphyrin-Pc assemblies have also been prepared using saddle distorted components, namely a protonated dodecaphenylporphyrin and octaphenyl Zn(II) phthalocyaninate complex, using 4-pyridinecarboxylate as a supramolecular linking unit. Both metal-ligand and hydrogen bonding interactions allow the assembly of the components [27],... 

There are two types of subjects in supramolecular chemistry (a) the supramolecular assemblies or systems, also called supramolecular arrays, that is, polymolecular entities that resultfrom the spontaneous association of a large undefined number of components, and (b) supermolecules, that is, well-defined discrete oligomolecular species that result from the intermolecular association of a few components... 

Owing to the enormous range of what can now be described as supramolecular chemistry, the present work will chiefly focus on discrete molecular assemblies. In particular, no attempt has been made to discuss the burgeoning field d of crystal engineering . Similarly, unless of particular relevance to the topic under discussion, higher oligomeric and polymeric systems, including most metal cluster and related compounds, have also been excluded from the discussion. 

In the following two chapters, we will explore two further major categories of discrete, non-metal-containing, supramolecular assemblies - namely, rotaxanes and the catenanes. 

As ligands for metal ions, 2,2 bipyridines find wide application in chemistry. They have been used in studies of supramolecular assembly,6 in bioinorganic contexts,7 and in polymeric materials,8 as well as in discrete small-molecule analogues. 

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