Ligand-Exchange Chromatography of Chiral Compounds

Abstract

Ligand-exchange chromatography represents one of the most typical cases of complexation chromatography. Complexes dealt with in these processes comprise metal cations associated with ligands (anions or neutral molecules) that are capable of donating electron pairs onto the vacant orbitals of the metal. It is clear that thorough studies are required if understanding of the chiral recognition mechanism is desired. Thus far, reliable achievements in this direction have been attained only in ligand-exchange chromatography and charge-transfer chromatography. In chiral charge-transfer chromatography, initial attempts have been made to apply computational chemistry, calculating the absolute interaction energies of the chiral selector with two enantiomers, in order to correlate the obtained differences in the interaction energies with the experimental enantioselectivity of chiral chromatographic systems. Mechanism of chiral recognition of amino acid enantiomers during formation of diastereomeric sorption complexes in the resin phase has been the subject of thorough investigation.