Synthesis and rapid enantiomeric separation of the chiral mixed ligand [5-(4-hydroxybutyl)-5′-methyl-2,2′-bipyridine]-bis(1,10-phenanthroline)-ruthenium(II) complex by electrokinetic chromatography

• Published in: Tetrahedron: asymmetry 2002-12, Vol.13 (24), p.2673-2678
• Main Authors: Holder, Elisabeth, Trapp, Gabriele, Grimm, Jost C., Schurig, Volker, Lindner, Ekkehard
• Format: Article
• Language: English
• ISSN: 0957-4166; 1362-511X
• DOI: 10.1016/S0957-4166(02)00753-X

The chiral complex [5-(4-hydroxybutyl)-5′-methyl-2,2′-bipyridine]-bis(1,10-phenanthroline)ruthenium(II)-bis(hexafluoroantimonate) was successfully synthesized and fully characterized by two-dimensional 1H and 13C{ 1H} NMR techniques (COSY and HMQC) as well as EA- and FAB-MS. A very fast separation of the Δ and Λ enantiomers with excellent efficiency and resolution was achieved by electrokinetic chromatography using anionic carboxymethyl-β-cyclodextrin as a chiral mobile phase additive. The optimum separation conditions were obtained with 50 mM borate buffer at pH 9 and 10 mg/ml of the chiral selector at 20°C. Attempts to separate the well known unmodified tris(2,2′-bipyridine)ruthenium(II) [Ru(bpy) 3] complex into its enantiomers under the same conditions were unsuccessful. The chiral modified mixed ligand [5-(4-hydroxybutyl)-5′-methyl-2,2′-bipyridine]-bis(1,10-phenanthroline)ruthenium(II) complex 3 was synthesized, characterized and separated into its constituent enantiomers by electrokinetic chromatography (EKC) using anionic carboxymethyl-β-cyclodextrin as a chiral mobile phase additive (CMPA). The described EKC separation offers the possibility of determining enantiomeric ratios with minute sample consumption, high efficiency and excellent resolution in approximately 100 s.