Molecular Recognition at Crystal Interfaces

Weissbuch, I., L. Addadi, M. Lahav, and L. Leiserowitz (1991), "Molecular Recognition at Crystal Interfaces", Science 253, 637-645. 

Weissbuch, I., Addadi, L., Lahav, M., and Leiserowitz, L. (1991) Molecular Recognition at Crystal Interfaces, Science 253, 637-645. 

I. Addadi, I. Weissbuch, M. Lahav and L. Leiserowitz. Molecular recognition at crystal interfaces. Science 253,1991, 637. 

In most cases, separation and purification via crystallization are highly selective due to the fact that molecular recognition process at the crystal-solution interface acts in such a way as to select the host molecules and reject impurities. However, sometimes the solute and impurity molecules are not discriminated at certain crystal faces, especially when the impurity has many of the structural and chemical characteristics of the primary solute but differs only in some specific way. A systematic approach toward understanding the effects of such impurities on crystal growth has been developed using the concept of tailor-made additives (Weissbuch et al. 2003). These additives are structurally similar to the solute molecules and are basically composed of two moieties. The first, known as the binder, has a similar structure (and stereochemistry) to that of the substrate molecule on the crystal surface where it adsorbs. The second, referred to as the perturber, is modified when compared with the substrate molecule and thus hinders the attachment of the oncoming solute molecules to the crystal surface. Several classic examples in the literature highlight this type of interaction mechanism in molecular crystals. 

Langmuir monolayers of calixarenes have also been studied for their ability to bind small organic molecules. Recently, we reported on the ability of Langmuir monolayers of an amphiphilic p-amidophenolcalix[4]arene derivative to interact with acetaminophen (APAP) [34, 49], an active pharmaceutical ingredient (API) widely used as analgesic and antipyretic, at the air-water interface. Interestingly, these calixarene-based surfaces act as templates for the interfacial crystallization of the pharmaceutical (Fig. 37.7) [34]. The similarity between the polar functions of the amphiphUe and the stmcture of APAP were shown to favor the molecular recognition event. 

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