Stereochemical studies on chiral systems in two dimensions

Structural studies on two-dimensional films of chiral amphiphiles at the ai r-solution interface, as investigated in situ primarily by grazing incidenc e x-ray diffraction (GIXD) using synchrotron radiation, yielded the crystal line packing arrangement at almost the molecular level. Results regarding t hree different topics are described. (1) It has proven possible to establis h whether racemic mixtures of amphiphiles spread on water self-organize int o 2-D crystals in which the two enantiomers either form heterochiral domain s or spontaneously separate into enantiomorphous islands composed of homoch iral molecules. Diastereoisomeric acid-base interactions between two differ ent chiral amphiphiles were also used to achieve spontaneous chiral separat ion in two dimensions. (2) Ordered binding of solute molecules to the chira l amphiphiles could be applied in order to study their enantioselective int eractions with chiral solutes present in the aqueous subphase. (3) Crystall ine multilayer films of supramolecular architecture composed of water-solub le and water-insoluble chiral components may be formed at the air-solution interface and their packing arrangement determined by GIXD. Copyright (C) 2 000 John Wiley & Sons, Ltd.