Supramolecules host-guest chemistry

Fig. 1 Definitions and overall scheme of supramolecular events (a) chemical host synthesis and formation of a supramolecule (host-guest inclusion compound) (b) endo- and exosupramolecular receptor-substrate (host-guest) chemistry and (c) formation of mono-and multimolecular inclusion compounds.

One type of supramolecule is a helicate, which has a double helix made of two chains held by copper ions along its axis. The structure is analogous to the double helix of DNA. See also host-guest chemistry. 

Because of their intellectual and practical importance, and their aesthetic beauty, chemists have longed to mimic such large, multimolecular complexes. The phrase supramolecular chemistry—chemistry beyond the molecule—has been coined to describe this field. Certainly, the host-guest systems we discussed above are simple examples of supramolecules, and the molecular recognition forces we ve enumerated will provide the driving force for assembly. But, when a large number of molecules assembles into one complex system, new issues arise. Here we will summarize some of the general issues associated with supramolecular chemistry, and then we will present some examples of especially successful or informative systems. 

Such complexes are sometimes called supramolecules. The choice of which molecule is the host and which is the guest is somewhat arbitrary, but the larger molecule is usually deemed the host. Enzyme-substrate complexes are a prime biochemical example of such interactions. Cram, Pedersen, and Lehn shared the 1987 Nobel Prize in chemistry for their pioneering work in the area of molecular recognition and supramolecular chemistry. The recent chemical literature is replete with examples in which NMR has been used to study such complexa-tion.6... 

In 1978, Jean-Marie Eehn introduced the modem concept of supramolecular chemistry, which he defined as the. . chemistry of molecular assemblies and of the inter-molecular bond, "" although the term itself made a much earlier appearance (in Webster s Dictionary in 1903). Traditionally, phrases such as "chemistry beyond the molecule." "the chemistry of the non-covalent bond," and non-molecular chemistry" or even "Lego chemistry" were also used to describe the field. In the beginning, supramolecules mainly comprised two components, a host and a guest, which interact with one another in a nonco-valent fashion (Fig. 1). The area rapidly evolved to... 

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