Enantiomeric Separations of Ruthenium (II) Polypyridyl Complexes Using HPLC With Cyclofructan Chiral Stationary Phases

Abstract

The enantiomeric separation of 21 ruthenium (II) polypyridyl complexes was achieved with a novel class of cyclofructan-based chiral stationary phases (CSPs) in the polar organic mode. Aromatic derivatives on the chiral selectors proved to be essential for enantioselectivity. The R-napthylethyl carbamate functionalized cyclofructan 6 (LARIHC CF6-RN) column proved to be the most effective overall, while the dimethylphenyl carbamate cyclofructan 7 (LARIHC CF7-DMP) showed complementary selectivity. A combination of acid and base additives was necessary for optimal separations. The retention factor vs. acetonitrile/methanol ratio plot showed a U-shaped retention curve, indicating that different interactions take place at different polar organic solvent compositions. The separation results indicated that π-π interactions, steric effects, and hydrogen bonding contribute to the enantiomeric separation of ruthenium (II) polypyridyl complexes with cyclofructan chiral stationary phases in the polar organic mode.

Superficially Porous Particle Based Hydroxypropyl‐β‐cyclodextrin Stationary Phase for High‐Efficiency Enantiomeric Separations

“…Chiral HPLC (high‐performance liquid chromatography) column packing materials have long lagged behind achiral column materials in terms of developing media that can be used to produce high‐efficiency separations. The area of developing new chiral selectors with unique enantiomeric selectivities has seen important advances in recent years . Meanwhile, research, commercialization, and the application of new achiral HPLC columns over the past decade have focused on increasing chromatographic efficiencies.…”

Interactions between pyrazole derived enantiomers and Chiralcel OJ: Prediction of enantiomer absolute configurations and elution order by molecular dynamics simulations

“…The plot of retention factor vs. solvent ratio disclosed a U-shaped retention curve, indicating that different interactions are dominant in different mixture of polar organic solvents [54]. It was suggested that the main sites of Chiralcel OJ involved in the chiral separation are probably the polar carbonyl groups and the aromatic fragments of the ester functional group [53].…”

Enhanced Photostability of a Ruthenium(II) Polypyridyl Complex under Highly Oxidizing Aqueous Conditions by Its Partial Inclusion into a Cyclodextrin

“…An especially attractive feature of cyclodextrins is their ability to act as chiral shift reagents, and several examples are known where racemic mixtures of ruthenium complexes were separated by their application to solutions. [27] In our case, separation of a racemic mixture was not required, because two pure enantiomers were already on hand. However, we wanted to observe if -CD would be a good chiral shift agent for rac-2, and more importantly if the -2 and -2 enantiomers would display subtle 1 H shifts upon host-guest complexation.…”