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
Es. Okerberg et al., 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, J MICROCOL, 12(7), 2000, pp. 391-397
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.