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In this study, the apparent binding constants and limiting mobilities of the multiply charged complexes of the Δ- and Λ-enantiomers of Ru(II)- and Fe(II)-polypyridyl associates ([Ru(2,2'-bipyridine) 3 ] 2+ , [Ru(1,10-phenanthroline) 3 ] 2+ , and [Fe(1,10-phenanthroline) 3 ] 2+ ) with single-isomer 2,3-diacetylated-6-sulfated-cyclodextrins (CDs) (12Ac-6S-α-CD, 14Ac-7S-β-CD, and 16Ac-8S-γ-CD) were determined by ACE using uncorrected and ionic strength corrected actual mobilities of the species involved. Two limiting models were tested for the ionic strength correction of the actual mobilities based on an empirical relation for the ionic strength correction of multivalent ionic species. In model 1, the nominal values of the charge numbers (z S,nom ) and analytical concentrations (c S,nom ) of the above CD selectors in the BGEs were applied for calculation of the BGE ionic strength, as usual. In model 2, the CD selectors were considered as singly charged species (z S  = -1) with |z S,nom |-times higher concentrations in the BGE than their analytical concentrations (c S  = |z S,nom | × c S,nom ) in the calculation of the BGE ionic strength. In all three cases-with uncorrected actual mobilities as well as with actual mobilities corrected according to the two limiting models-the measured effective mobilities of the above enantiomers fit well the theoretical curves of their mobility dependences on the CD selectors concentrations in the BGE, with high average coefficients of determination (R 2  = 0.9890-0.9995). Nevertheless, the best physico-chemically meaningful values of the apparent binding constants and the limiting mobilities of the enantiomer-CDs complexes with low RSDs were obtained using the actual mobilities of the species involved corrected according to model 2., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

CE using randomly highly sulfated α-, β-, and γ-CDs (S-α-CD, S-β-CD, S-γ-CD), sulfobutylether-β-CD (SBE-β-CD), single isomer (6-O-sulfo) α-, β-, and γ-CDs, and their derivatives as stereoselectors was applied to chiral analysis of polypyridyl complexes of [Ru(bpy) 3 ] 2+ , [Ru(phen) 3 ] 2+ , and [Fe(phen) 3 ] 2+ (bpy = 2,2'-bipyridine; phen = 1,10 phenanthroline). The best separations of Δ- and Λ-enantiomers of the these complexes with high resolution (up to R 1,2  = 7.0) and short analysis times (10-20 min) were achieved in the BGE composed of 22 mM NaOH/35 mM H 3 PO 4 , pH 2.4, containing 1.5-6.0 mM S-α-CD or S-β-CD, or SBE-β-CD as chiral selectors. The developed method was applied to the assessment of enantiomeric purity of several samples of [Ru(bpy) 3 ] 2+ catalyst. CE experiments were performed in a homemade analyzer equipped with bare or hydroxypropylcellulose-coated fused-silica capillaries (total/effective length 40/29 cm, id/od 50/375 μm) and an UV absorption detector operating at 206 nm. In addition to chiral analysis, apparent binding constants of the complexes of [Ru(bpy) 3 ] 2+ , [Ru(phen) 3 ] 2+ , and [Fe(phen) 3 ] 2+ enantiomers with five sulfated CDs (S-α-CD, S-β-CD, S-γ-CD, SBE-β-CD, and 16Me-8S-γ-CD) were determined from the dependence of their effective electrophoretic mobilities on the concentration of the CDs in the BGE by nonlinear regression analysis. Calculated apparent binding constants of these complexes were found to be in the (1.10-4.66) × 10 3  L/mol range. Moreover, it was shown that at selected concentrations of some S-CDs and suppressed or very low electroosmotic flow, the exceptional enantioseparations with infinite resolution could be achieved., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Enantiomers of helical N-heteroaromatic dications, helquats, were separated by CE. An acidic 22/35 mM sodium/phosphate background electrolyte, pH 2.4, with addition of randomly sulfated α-, β- and γ- cyclodextrins allowed enantioresolution of a series of helquats, which comprised 5, 6 and 7 fused rings participating in the helical backbone. In general, at least one of the chiral selectors was found to provide baseline separation for 22 out of 24 helquats and partial separation for the remaining two. Individually, the sulfated γ-cyclodextrin turned out to separate 79% of the helquats, followed by the β- and α-congeners with 54 and 42% of the resolved compounds, respectively. Migration order of enantiomers was inspected for selected helquats and a relation of molecular size of the analytes to a cavity of the cyclodextrin selectors is discussed., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The enantiomers of diquats (DQs), a new class of functional organic molecules, were recently separated by capillary electrophoresis (CE) with high resolution up to 11.4 within 5–7 min using randomly sulfated α‐, β‐, and γ‐cyclodextrins (CDs) as chiral selectors. These results indicated strong interactions between dicationic diquats and multiply negatively charged sulfated CDs (S‐CDs). However, the binding strength of these interactions was not quantified. For that reason, in this study, affinity CE was applied for the determination of the binding constants and ionic mobilities of the complexes of DQ P‐ and M‐enantiomers with CD chiral selectors in an aqueous medium. The non‐covalent interactions of 10 pairs of DQ enantiomers with the above CDs were investigated in a background electrolyte (BGE) composed of 22 mM NaOH, 35 mM H3PO4, pH 2.5, and 0.0–1.0 mM concentrations of CDs. The average apparent binding constant and the average actual ionic mobility of the DQ‐CD complexes were determined by nonlinear regression analysis of the dependence of the effective mobility of DQ enantiomers on the concentration of CDs in the BGE. The complexes were found to be relatively strong with the averaged apparent binding constants in the range 13 600–547 400 L/mol. [ABSTRACT FROM AUTHOR]

Diquats, derivatives of the widely used herbicide diquat, represent a new class of functional organic molecules. A combination of their special electrochemical properties and axial chirality could potentially result in their important applications in supramolecular chemistry, chiral catalysis, and chiral analysis. However, prior to their practical applications, the diquats have to be prepared in enantiomerically pure forms and the enantiomeric purity of their P‐ and M‐isomers has to be checked. Hence, a chiral capillary electrophoresis (CE) method has been developed and applied for separation of P‐ and M‐enantiomers of 11 new diquats. Fast and better than baseline CE separations of enantiomers of all 11 diquats within a short time 5–7 min were achieved using acidic buffer, 22 mM NaOH, 35 mM H3PO4, pH 2.5, as a background electrolyte, and 6 mM randomly sulfated α‐, β‐, and γ‐cyclodextrins as chiral selectors. The most successful selector was sulfated γ‐cyclodextrin, which baseline separated the enantiomers of all 11 diquats, followed by sulfated β‐cyclodextrin and sulfated α‐cyclodextrin, which baseline separated enantiomers of 10 and nine diquats, respectively. Using this method, a high enantiopurity degree of the isolated P‐ and M‐enantiomers of three diquats with a defined absolute configuration was confirmed and their migration order was identified. [ABSTRACT FROM AUTHOR]

Racemic [5]helquat as a triflate salt has been synthesized using a robust, three-step procedure. Subsequent exchange of triflate anions for inexpensive (R,R)-dibenzoyltartrate anions viaan ion exchange resin afforded two diastereoisomeric salts. Crystallization led to the resolution of the helquat (ee > 98%). This is the first time that a non-racemic helquat has been obtained; its helicity having been assigned and its racemization barrier determined. Capillary electrophoresis with a sulfated β-cyclodextrin chiral selector is introduced for the first time as a straightforward method to analyze the enantiocomposition of charged, helicene-like species. [ABSTRACT FROM AUTHOR]