Application of chiral lanthanide-induced shift reagents to optically active cations: the use of tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorato]europium(III) to determine the enantiomeric purity of tris(phenanthroline)ruthenium(II) dichloride

Abstract

In non-polar solvents, chiral europium complexes provide attractive n.m.r. shift reagents to resolve spectra of optically active cations, and, in particular, for tris(phenanthroline)ruthenium dichloride, 1 H n.m.r. shift differences of up to 0.7 p.p.m. between isomers easily permit the determination of absolute enantiomeric purity.There has been considerable interest in the determination of enantiomeric purity by n.m.r. spectroscopy using chiral shift reagents. 1-4 Although lanthanide-induced shift reagents were first used to study cations in 1973, 5 chirallanthanide-induced shift reagents have been used only with neutral species. We report the application of chiral lanthanide-induced shift reagents to optically active cations. For the following study we employed tris(phenanthroline )ruthenium(n) complexes, [Ru(phen)3)2+, which we are currently using as chiral probes for DNA.6Tris(phenanthroline )ruthenium( n) dichloride was prepared as described by Lin et al. 7 and partially resolved by recrystalli-

Asymmetric Transformation of a Double-Stranded, Dicopper(I) Helicate Containing Achiral Bis(bidentate) Schiff Bases

“…It is surprising that the chiral LSR induced such a large chemical shift difference between the two possible diastereomers of the hexafluorophosphate salt of the complexes. The literature suggests that a small, nucleophilic anion (unlike the hexafluorophosphate) is necessary for the interaction of the chiral LSR with the anion in order that ion-pairing can occur …”

Rh(DIP)33+: a shape-selective metal complex which targets cruciforms

“…Enantiomers of [Rh(DIP)3]C13 were separated by a modified method of Gillard et al (17). The optical purity of both enantiomers was found to be greater than 90% by NMR experiments using a chiral shift reagent (18).…”

Enantioselective host–guest complexation of Ru(II) trisdiimine complexes using neutral and anionic derivatized cyclodextrins

“…Circular dichroism and optical rotary dispersion are two commonly used methods, however, these data do not give the absolute optical purity of the product. Absolute measures of enantiopurity require separation based-techniques such as chiral HPLC, capillary electrophoresis (CE), and other column-based separation methods [18-20] or spectroscopic methods such as NMR in the presence of chiral-shift reagents [7, 21]. All of these techniques rely, to a significant extent, on the formation of diastereomeric, non-covalent complexes (e.g.…”