Combinatorial approach to enantiomeric discrimination: synthesis and (19)F NMR screening of a chiral ionic liquid-modified silane library.

A parallel library of chiral ionic liquid (CIL)-modified silanes as potential chiral selectors was synthesized, and their enantiomeric discrimination abilities were screened by use of (19)F NMR spectroscopy. The screening method allows for rapid identification of the most enantioselective members of the library and simultaneous investigation of their chiral recognition mechanisms. The library compounds were synthesized using quaternization and anion-exchange reactions. Three major parameters (type of chiral cations, anions, and linker chain lengths) were included and investigated during the synthesis and screening. As expected, the structure of the chiral cation was found to play an important role in determining chiral recognition abilities. In addition, several types of intermolecular interactions including ion-pair, hydrogen bonding, pi-pi stacking, dipole stacking, and steric interactions were found to impact chiral discrimination.