Spectroscopic investigations and analytical applications of enantiomeric interactions

Chiral recognition is an important subject in various fields including chemistry, biology, pharmaceutical, and medical sciences. Even though various chiral selectors have been developed for chiral separations in HPLC, Capillary Electrochromatography and Capillary Electrophoresis, compare to the large amount of available enantiomers, chiral selectors are still in great demand. Furthermore, to date, induced chiral separation mechanisms have not been thoroughly studied. Chiral ionic liquids (CILs) can be used as chiral solvents and may promote chiral discrimination. In Chapter 1, a group of over 15 pairs of CILs were synthesized through one step metathesis reaction. They were studied by NMR, LC-MS, DSC, TGA and X-Ray crystallography. X-Ray crystallography of some of the CILs indicates that C-H···O hydrogen bonds provide dominating forces for crystal packing. NMR studies show that enantiomers of these CIL pairs interact differently with tBuCQN-HCl which is a chiral selector. And chiral anions of these CILs have good chiral discrimination ability on racemic cations. And also, these CILs undergo aggregation in solution in a similar way as surfactants do. In Chaper 2, a new method based on a Near-Infrared spectrophotometric technique has been developed to determine critical micelle concentration (CMC) of surfactants in ionic liquids. Comparing to other CMC determination methods, this NIR method is universal, sensitive, nonintrusive and nonadditive. CMC values of various surfactants including CTAB, SDS, TritonX-100, Brij-35, Brij-700, Tween-20, SB-12, S133-10 and AOT in aqueous solvent, organic solvent or ionic liquids determined by this method agree very well with those determined by other methods. In Chapter 3, to approach the mechanism of chiral interaction, a new method based on UV-vis was developed. Chiral selector carbamoylated derivatives of quinine (tBuCQN) and 3,5-dinitrobenzoyl derivatives of Leucine (DNB-Leu) enantiomers were selected. Derivatives of Leucine were used as substrate. Binding constants of tBuCQN and these Leucine derivatives in solvents with different polarities were determined with either UV-vis or NMR spectroscopic methods to determine the function of different groups and solvent effects. Results obtained have been successfully applied to capillary electrophoresis for chiral separation with tBuCQN as a chiral selector