National Repository of Grey Literature 8 records found  Search took 0.01 seconds. 
Enantioseparation and estimation of racemization barriers of selected helquats and their derivatives by capillary electrophoresis using sulfated cyclodextrins as chiral selectors
Sázelová, Petra ; Koval, Dušan ; Severa, Lukáš ; Reyes Gutierrez, Paul Eduardo ; Jirásek, Michael ; Teplý, Filip ; Kašička, Václav
Anionic highly sulfated β- and γ-cyclodextrins (S-CDs) and single-isomer heptakis-(2,3-diacetyl-6-sulfato)-β-CD (14Ac-7S-β-CD) were used for chiral separation of [5], [6] and [7]-ring helquats and helquat styryl dyes by capillary electrophoresis (CE) in the background electrolyte composed of 22 mM NaOH/35 mM H3PO4, pH 2.4. The CE method was applied for monitoring of racemization of eight helquats and helical dyes. Rate constant k of conversion, half-life T1/2 of racemization, and activation Gibbs free energy ΔGǂ of interconversion of one enantiomer into the other were calculated from the dependence of natural logarithm of enantiomeric excess (ee) on time using linear regression analysis.
Estimation of binding constants of associates of Ru(II) and Fe(II) polypyridyl complexes with single-isomer sulfated cyclodextrins by capillary electrophoresis
Sázelová, Petra ; Koval, Dušan ; Severa, Lukáš ; Teplý, Filip ; Kašička, Václav
Capillary electrophoresis (CE) was applied for enantioseparations of [Ru(bpy)3]2+, [Ru(phen) 3]2+ and [Fe(phen) 3]2+ complexes and for the estimation of binding constants of their associates with selected single-isomer sulfated cyclodextrins (SCDs). The apparent binding constants of the complexes of [Ru(bpy)3]2+, [Ru(phen)3]2+, and [Fe(phen)3]2+ enantiomers with the above SCDs were determined from the dependence of their effective electrophoretic mobilities on the concentration of the SCDs in the background electrolyte. Calculated apparent binding constants were found to be smaller than those obtained for randomly sulfated SCDs.
Affinity capillary electrophoresis applied to chiral separations of diquats and to determination of the stability constants of their complexes with sulfated cyclodextrins
Kašička, Václav ; Bílek, Jan ; Koval, Dušan ; Sázelová, Petra ; Talele, Harish Ramesh ; Severa, Lukáš ; Reyes Gutierrez, Paul Eduardo ; Teplý, Filip
Affinity capillary electrophoresis (ACE) using an aqueous 22/35 mM sodium/phosphate buffer, pH 2.5, as the background electrolyte (BGE), and 6 mM randomly highly sulfated alpha-, beta- and gamma-cyclodextrins (CDs) as chiral selectors has been successfully applied for separation of (P)- and (M)-enantiomers of a series of eleven new diquats (DQs) and for estimation of the strength of their complexes with the above CDs. The apparent stability constants of the DQs-CDs complexes were determined from the simultaneous ACE measurements of the dependence of effective electrophoretic mobilities of (P)- and (M)-enantiomers of DQs on the concentrations of CDs in the BGE by nonlinear regression analysis. The DQs enantiomers formed strong complexes with all three types of CDs with the apparent stability constants in the range (7.80 547.4) × 103 L/mol.
Estimation of racemization barriers of selected helquats and their derivatives by capillary electrophoresis using sulfated cyclodextrins as chiral selectors
Sázelová, Petra ; Koval, Dušan ; Severa, Lukáš ; Reyes Gutierrez, Paul Eduardo ; Jirásek, Michael ; Teplý, Filip ; Kašička, Václav
The recently developed capillary electrophoretic (CE) method for chiral analysis of helquats (helical N-heteroaromatic dications) was applied to monitoring of racemization of selected helquats and helquat styryl dyes and for the determination of their racemization barriers, i.e. activation Gibbs free energy deltaG≠. deltaG≠ of analyzed compounds was found to be in the range 107.7 – 115.7 kJ/mol.
Chiral analysis of alfa-diimine Ru(II) and Fe(II) complexes by capillary electrophoresis using sulfated cyclodextrins as stereoselectors
Sázelová, Petra ; Koval, Dušan ; Severa, Lukáš ; Teplý, Filip ; Kašička, Václav
A fast and efficient capillary electrophoretic method was developed for enantioseparation of Ru(II) and Fe(II) polypyridyl complexes using anionic randomly sulfated alfa-, beta-, and gamma-cyclodextrins (S-alfa-CD, S-beta-CD, and S-gamma-CD) and their heptakis-(2,3-diacetyl-6-sulfato)-derivatives (Ac-S-alfa-CD, Ac-S-beta-CD, and Ac-S-gamma-CD) as chiral selectors. S-alfa-CD and S-gamma-CD were found to be the best chiral selectors providing high resolutions and short analysis times. The method was applied for the assessment of chiral purity of some batches of [Ru(bpy)3]2+ catalyst.
Capillary electrophoresis applied to chiral analysis of helquats and characterization of their intermediates and interconversion barriers using randomly and single isomer sulfated cyclodextrins as stereoselectors
Kašička, Václav ; Koval, Dušan ; Sázelová, Petra ; Severa, Lukáš ; Vávra, Jan ; Adriaenssens, Louis ; Sonawane, Manoj R. ; Teplý, Filip
Capillary electrophoresis in acidic sodium phosphate background electrolyte, pH 2.4, with randomly sulfated alfa-, beta- and gamma-cyclodextrins as chiral selectors was applied to fast, high-resolution separation of enantiomers of a series of 35 helquats, a new class of N-heteroaromatic dicationic helicene-like species. The developed methodology was employed for evaluation of preparative enantioresolution procedures of helquats, for monitoring their racemization and for determination of interconversion barrier of helquat enantiomers.
Capillary electrophoretic chiral analysis and estimation of helix inversion barrier of helquats using randomly sulfated cyclodextrins as chiral selectors
Kašička, Václav ; Koval, Dušan ; Sázelová, Petra ; Severa, Lukáš ; Adriaenssens, Louis ; Vávra, Jan ; Teplý, Filip
Capillary electrophoresis in acidic sodium phosphate background electrolyte, pH 2.4, with randomly sulfated alpha-, beta- and gamma-cyclodextrins as chiral selectors was employed for fast, high-resolution separation of enantiomers of a series of 24 helquats, a new class of N-heteroaromatic dicationic helicene-like species. The developed CE methodology will be utilized in the further investigation of helquats, e.g., in evaluation of their preparative enantioresolution procedures, in monitoring of their racemization and determination of interconversion barrier of helquat enantiomers.
Enantiomer separation and determination of helix inversion barrier of helical dications by capillary electrophoresis
Koval, Dušan ; Adriaenssens, Louis ; Severa, Lukáš ; Teplý, Filip ; Sázelová, Petra ; Kašička, Václav
Enantiomeric helical forms of dicationic helquats, a novel family of charged helicene-like molecules, have been separated by capillary electrophoresis (CE) using sodium-phosphate buffer, pH 2.5, as background electrolyte and sulfated beta- and gamma-cyclodextrins as chiral selectors. Additionally, CE was used to determine barrier to helix inversion of helquats.

See also: similar author names
1 Severa, L.
2 Severa, Libor
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