Guest@host supramolecular chemistry

Since the pioneering work of Pedersen (1), Lehn (2), and Cram (3) on synthetic macrocyclic and macropolycyclic host systems such as the crown ethers, cryptands, and spherands, there has been an enormous development of the field of host-guest or supramolecular chemistry. Molecular hosts designed to bind inorganic and organic, charged and neutral guest species via cumulative, noncovalent interactions have all been reported and extensive reviews on this subject have appeared (4-8). 

Keywords Bio-organometallic chemistry Drug delivery Half-sandwich complexes Host-guest systems Supramolecular chemistry... 

Melchiorre F. Parisi graduated in Chemistry at the University of Messina and obtained a Ph.D. in Organic Chemistry from the University of Oxford, under the supervision of Professor Jack E. Baldwin, in 1986. Between 1987 and 1988, he worked as a postdoctoral research fellow with Professor Robert H. Abeles at Brandeis University (CNR-NATO, Advanced Fellowship Program). Fie currently holds the position of Associate Professor of Organic Chemistry at the University of Messina. His most recent research interests lie in the field of host-guest and supramolecular chemistry. 

There are thousands of discoveries in molecular science reported every year but very few of these are destined to promote a new generation of research activity. The serendipitous preparation of di-benzo-18-crown-6 1 by Pedersen in 1967 [1] and the subsequent discovery [1,2] that 1 and other crown ethers selectively complex biologically relevant alkali and alkaline earth cations was, however, the catalyst for a huge explosion of activity in the field of host-guest or supramolecular chemistry. The resulting inspired and innovative work by Lehn [3,4] on, in particular, the 3-dimensional bicyclic cryptands (e.g., 2) and by Cram [5] on chiral crown ethers and rigid spherands (e.g., 3) was recognised by the award to Pedersen... 

Perhaps the most efficient stimulus in cyclophane chemistry goes back to the discovery of crown ethers by C. J. Pedersen in 1967 [(1967) J Am Chem Soc 89 7017] being the starting signal for a very promising field of research called Host-Guest or Supramolecular Chemistry. Actually the first crown ether that was synthesized, dibenzo-18-crown-6, was a cyclophane. 

This entry to supramolecular chemistry allows one, at the same time, to develop a host-guest chemistry because the space inside the cucurbituril barrel is sufficient to confine small "guesf molecules. This is illustrated with the crystallization of the supramolecular adduct [W3S4(H20)8Cl](pyH ccuc) Cl4a 5.5 H2O with a pyridinium cation inside the cucurbituril cavity [48]. The introduction of guest molecules may vary the net charge on the assembly and consequently the whole packing in the solid state. 

In this decade, all chemistry research fields have adopted and/or applied the dendrimers and/or dendrimer methodologies. The table of contents of this series. Topics in Current Chemistry Dendrimers Volumes I-IV, clearly indicates this situation [1-4], that is, the concept of dendritic compounds has already been introduced in host-guest and/or supramolecular chemistry (Vol. I/Chap. 2, Vol. Il/Chaps. 3,4, Vol. IV/Chap. 3), chiral chemistry (Vol. I/Chap. 4), electrochemistry (Vol. I/Chap. 6, Vol. Ill/Chap. 3), heteroatom and/or organometalHc chemistries (Vol. I/Chap. 3, Vol. Il/Chaps. 2,5, and Vol. IV/Chap. 4), and carbohydrate chemistry (Vol. IV/Chap. 6), as well as applied in the field of medicine (Vol. Il/Chap. 6) and nanoscience (Vol. Ill/Chap. 4). The dendrimer methodology is expected to be used in future novel science as a conventional chemistry concept. 

Goshe, A.J., Steele, I.M., Ceccarelli, C., Rheingold, A.L. and Bosnich, B. (2002) Supramolecular chemistry and self-assembly special feature supramolecular recognition on the kinetic lability of thermodynamically stable host-guest association complexes. Proceedings of the... 

Supramolecular chemistry takes into consideration the weak and reversible non-covalent interactions between molecules, which include H-bond-ing, metal coordination, hydrophobic forces, van der Waals forces, n—n interactions, and covers different research fields, for example, molecular recognition, host-guest chemistry, mechanically interlocked and nanochemistry. 

The synthesis of the macrocycles 43 (Scheme 9) is an example of repetitive, highly stereoselective Diels-Alder reaction between bis-dienes 41 and bis-dienophiles 42, containing all oxo or methano bridges syn to one another. The consecutive inter- and intramolecular Diels-Alder reactions only succeed at high pressure. Obviously, both reactions are accelerated by pressure. The macrocycles are of interest in supramolecular chemistry (host-guest chemistry) because of their well-defined cavities with different sizes depending on the arene spacer-units. 

Keywords Supramolecular Chemistry m Host-Guest Chemistry m Self-Assembly... 

Keywords Constrictive Binding m Crown Ethers m Hemicarcerands a Host-Guest Chemistry a Noncovalent Interactions aRotaxanes a Self-Assembly a Slippage a Supramolecular Chemistry... 

Horticulture, high performance fibers in, 13 394. See also Agriculture Hostaflon TFA, 7 641 Hostaflon TFB, 7 641 Host compounds, in supramolecular chemistry, 24 29-30 Host-guest chemistry, 14 160 24 30... 

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