Use of chiral capillary electrophoresis and circular dichroism for the determination of absolute values of Îε for diimine transition metal complexes
ACS Citation
Herbert, B. J.; Carpenter, H. E.; Kane-Maguire, N.; Wheeler, J. F. Use of chiral capillary electrophoresis and circular dichroism for the determination of absolute values of Îε for diimine transition metal complexes. Anal. Chim. Acta 2004, 514, 27-35.
Version of Record
Abstract
Circular dichroism (CD) alone cannot be used to derive absolute values of Δε for optically active transition metal (TM) complexes in the frequent instances in which pure, resolved standards are unavailable. In the past, this has led to discrepancies in the literature regarding the most appropriate value for use in assessing optical purity. We have recently shown that capillary electrophoresis (CE), employing a chiral selecting agent in the buffer, is a highly effective means to fully resolve the Λ and Δ enantiomers of M(diimine)3]n+ complexes. In this extension to that work, CE peak areas for optically active (but not optically pure) TM complexes are used in combination with CD spectra that are independently obtained for the same samples to extrapolate absolute circular dichroism values, Δε, for the pure Δ and Λ isomers. Examples are provided for a variety of tris- and bis-diimine systems, including different coordinated metal (e.g., Cr, Ni, Ru, Co) and ligand (e.g., bipyridine, phenanthroline, oxalato, cyano, etc.) combinations rendering outer sphere complex charges of 0, +1, +2 and +3. Based on the absolute values for Δε presented in this report, accurate measurement of optical purity for a number of M(diimine)3]n+ and cis-M(diimine)2X2]n+ systems is now possible via routine CD analysis.
Source Name
Analytica Chimica Acta
Publication Date
1-1-2004
Volume
514
Issue
1
Page(s)
1304-1311
Document Type
Citation
Citation Type
Article