Host-guest supramolecular

The photochemistry of vision provides us with an example of host-guest supramolecular photochemistry where the smaller 11-cis-retinal guest molecule is held within the internal cavity of the much larger protein host molecule (opsin) as a result of noncovalent bonding. 

Kawase, Oda, and coworkers have synthesized a unique series of belt-shaped paraphenylacetylene macrocydes 68-71 (Scheme 6.18A) and studied their host-guest supramolecular chemistry. The precursor polyenes 72-75 were synthesized using a modified McMurry reaction, and a subsequent bromination/dehydrobro-mination sequence with t-BuOK gave the desired SPMs 68-71. A 4 1 mixture of 72/74 gave the corresponding mixture of SPMs 68 and 70, which could be separated by GPC, while pure samples of 73 and 75 could be obtained to provide 69 and 71 directly [73,74]. Using the same bromination/dehydrobromination procedure, SPMs 76-78 were synthesized with 1,4- or 2,6-naphthylene units, respectively, at opposing positions (Scheme 6.18B). 

Macrocycles are a highly topical subject. They constitute a large spectrum of compounds involving both artifical substances and natural products such as crowns, cryptands, cyclophanes, porphyrins, or macrolides. The former initiated the exiting area of host-guest supramolecular chemistry, which was highlighted by the award of the Nobel Prize for Chemistry to D. J. Cram, J.-M. Lehn, and C. J. Pedersen in 1987 but is still developing enormously. Porphyrins and macrolides are important active substances. No wonder that macrocycles are of immediate interest and everyone wants to know how they can be synthesized efficiently. 

The first host-guest supramolecular system of EMFs was obtained by the incorporation of Dy Cs2 into calix[8]arene (C8A), which was compared with the better known [Ceo-CSA] [162]. Perhaps attributable to the larger sizes and different conformational changes, it is more difficult for Dy Cs2 to form a complex with C8 A than Ceo, as evidenced by the longer reaction time and lower yield. However, once formed, [Dy Cs2-C8A] is much more stable than the Ceo analog. 

Ubukata, T., Seki, T., and Ichimura, K. Surface relief gratings in host-guest supramolecular materials. Adv. Mater., 12, 1675 (2000). 

Fig. 2 General classification/nomenclature and descriptive terminology of host-guest supramolecular inclusion compounds...

The calixarenes are important molecular receptors and play a major role in host-guest supramolecular chemistry [162, 163, 163a], Their conic shape favors host-guest complexation of various hydrophobic molecules and the functionalized rim enables interaction with polar molecules. Modifieation of calixarenes by organometallic moieties can be achieved ... 

Damos FS, Luz RC, Tanaka AA, Kubota LT (2010) Dissolved oxygen amperometric sensor based on layer-by-layer assembly using host-guest supramolecular interactions. Anal Chim Acta 664(2) 144-150... 

A generic approach to the sensitive detection of noradrenalin and adrenalin catecholamines in a PDA-phospholipid matrix anchoring appropriate synthetic hosts was demonstrated using a fluorescence or visible color transition upon molecular recognition (Figure 16.9a) of catecholamines with specific host-guest supramolecular interactions. 

Some of the first host-guest supramolecular systems involved the encapsulation of metal ions (charged metal atoms) inside cyclic organic molecules ( macrocycles ). In these supramolecules, the metal ion sits inside the center of the macrocycle and is held in place by weak interactions between the metal ions and heteroatoms ( heteroatoms refers to the noncarbon and nonhydrogen atoms in the macrocycle). In this case, these weak interactions can be described, in a very basic sense, as the attraction of opposite charges. Metal ions... 

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