MEKC with bile salt micelles for the enantiomeric separation of bis(8-((pyridine-2-methylene)amino) quinoline) iron(II) hexafluorophosphate: Kineticsand mechanism of the racemization

Unsymmetrical tridentate ligands can form meridional optical isomers in oct ahedral complexes. Micellar electrokinetic chromatography with sodium tauro chenodeoxycholate or glycochenodeoxycholate micelles is used to separate th e enantiomers of bis(8-((pyridine-2-methylene)amino)quinoline)iron(II) hexa fluorophosphate, Fe(PMAQ)(2)(PF6)(2), and it is used to follow the temperat ure dependence of the racemization of the isolated enantiomers. The racemiz ation is studied over a 20 degrees temperature range (60-80 degrees C), and at four different pH values (3.0, 4.45, 7.0, 9.0). Energies and entropies of activation are reported. There is no significant change in the energy of activation as a function of pH. Simple capillary electrophoretic instrumen tation with manual, electrokinetic injection, and ambient run temperature c onditions provides reliable kinetic data. Half-lives range from 28 to 640 m in. A mechanism involving a trigonal prism transition state is proposed for this racemization process. (C) 2000 John Wiley & Sons, Inc.