Supramolecular categories

The toolkit of interactions available for supramolecular polymers can be divided into the six categories fisted in Table 1.1 that includes hydrophobic interactions, which are dealt with in more detail in Chapter 2. 

One of the points made in Schwenz and Moore was that the physical chemistry laboratory should better reflect the range of activities found in current physical chemistry research. This is reflected in part by the inclusion of modem instrumentation and computational methods, as noted extensively above, but also by the choice of topics. A number of experiments developed since Schwenz and Moore reflect these current topics. Some are devoted to modem materials, an extremely active research area, that I have broadly construed to include semiconductors, nanoparticles, self-assembled monolayers and other supramolecular systems, liquid crystals, and polymers. Others are devoted to physical chemistry of biological systems. I should point out here, that with rare exceptions, I have not included experiments for the biophysical chemistry laboratory in this latter category, primarily because the topics of many of these experiments fall out of the range of a typical physical chemistry laboratory or lecture syllabus. Systems of environmental interest were well represented as well. 

Another well-represented category was that of self-assembled monolayers (SAMS) and other supramolecular systems. The experiments on the SAMS included studies of the surface pKa of one system (110), the kinetics and thermodynamics of the self-assembly process (111), and the characterization of the SAM surface by study of solution contact angles (112). The experiments on supramolecular systems included studies on chemical equilibria in such systems (113, 114, 115), the kinetics of inclusion phenomena (116), and the use of solvatochromic probes in studying inclusion phenomena (117). 

The supramolecular assemblies involving aggregated porphyrinoids similarly to other types of previously discussed systems could be reasonably divided into different categories on the basis of achiral, chiral monomeric, and dimeric porphyrinoids. Again, the simplest monomeric achiral porphyrinoids will be presented first. 

Supramolecular chemistry - broadly the chemistry of multicomponent molecular assemblies in which the component structural units are typically held together by a variety of weaker (non-covalent) interactions - has developed rapidly over recent years. Typically is used since, in a considerable number of systems, metal-donor bonds - often essentially covalent in nature - have also been employed to stitch together organic components into larger assemblies. Such metal-linked assemblies will be treated as part of the supramolecular realm in the present work (although not employed here, perhaps supermolecular is a better term for this category). 

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

At present, the known catenanes can be divided into two categories - those prepared by metal template synthesis and those synthesised in the absence of a metalion influence. A considerable number of catenanes of the first type have been prepared by Sauvage et al. as well as by a number of other workers. However, discussion on these important metal-ion-directed systems is deferred to the next chapter in which particular supramolecular assemblies produced by metal-ion-controlled procedures are discussed. 

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