Séminaire du Département de chimie
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|Molecules inside Molecules|
Julius Rebek (The Scripps Research Institute, USA)
23 janvier 2006
Molecular recognition is the science of weak, intermolecular forces acting on complementary surfaces. This lecture follows the course of research that elaborates synthetic structures with concave surfaces into receptors. These receptors are deep, open-ended cavitands that more or less surround their target molecules. Complementarity of size, shape and chemical surface and the proper filling of space are involved in the recognition of smaller structures. Cavitands outfitted with additional functionality are shown to give rise to extaordinary reactivity. An example of an amine in a receptor bearing an inwardly-directed carboxyl group is shown below.
As the synthetic receptors make contact with increasingly larger fractions of the targets’ surfaces, complete encapsulation is the result. The encapsulation complexes are held together by weak intermolecular forces and are dynamic: they form and dissipate on time scales ranging from milliseconds to days, long enough for many interactions - even reactions - to take place within them. New forms of stereoisomerism can be seen for molecules in the cramped quarters and reactive intermediates can be prevented from escaping. Larger capsular hosts, in which more than one guest can be accommodated provide nanometric chambers for bimolecular reactions. An example of new stereoismerism arising from encapsulation is shown below.
||Julius Rebek (The Scripps Research Institute, USA)|
The Skaggs Institute for Chemical Biology and Department of Chemistry, The Scripps Research Institute, USA