MECHANISMS OF MOLECULAR RECOGNITION - INVESTIGATIONS OF ORGANIC HOST GUEST COMPLEXES

Noncovalent interactions constitute the basis for information transfer between molecules in living systems as well as in synthetic supramolecular structures. Despite ever more accurate descriptions of biological systems and a dramatically increasing diversity of synthetic host guest complexes, a systematic and general understanding of the underlying intermolecular forces is still in its infancy. Organic chemistry makes possible the targeted construction of infinitely variable host compounds with multiple centers interacting in complementary ways. This in turn opens the door to systematic experimental analyses based on binding increments, which can be shown to have a high degree of additivity. Even in the case of relatively simple ion pairs, several mechanisms are at work simultaneously, and either entropy or enthalpy contributions may prove to be decisive. Nevertheless, it is possible to identify individual interactions and then use them to practical advantage in ways analogous to the free‐energy relationships of physical organic chemistry. Contributions due to solvophobic effects, to interactions with permanent and induced dipoles, and to hydrogen bonds lend themselves to a high degree of empirical quantification on the basis of classical physical‐chemical principles. Water as a solvent plays a special role due to its low polarizability, apart from hydrophobic effects. Quantification of pairwise interactions and ultimate control over them through manipulation of the microenvironment should prove useful not only in the design of new synthetic host–guest complexes but also, for example, in the rational development of biologically active substances, molecular switches (e.g., for sensor technology), and catalysts that function analogously to enzymes. The results should also assist in the planning and analysis of biochemical experiments including techniques of genetic engineering. Copyright © 1991 by VCH Verlagsgesellschaft mbH, Germany