We present enantioseparation of a series of racemic sulfoxides on three different amylose-based polysaccharide columns. Two of them have the amylose units modified with dimethylphenyl carbamoyl groups (Chiralpak AD-H and Chiralpak IA), while the third one possesses a carbamoyl moiety with an additional chiral centre (Chiralpak AS-H). The enantioseparation of selected analytes was achieved in high-performance liquid chromatography (HPLC) and the full analyte set was enantiomerically resolved using supercritical fluid chromatography (SFC). Comparing the results obtained in both modes, we show that enantioseparation under SFC conditions is superior to HPLC mode in terms of speed, while retaining excellent enantioselectivity and resolution. Faster elution of analytes was observed on increasing the polarity of the co-solvent (modifier) in the mobile phase. This trend is apparent in both chromatographic modes. Documenting the important role of the additional chiral centre, Chiralpak AS-H provided the best chromatographic parameters resulting in the enantioseparation of all analytes.

We present enantioseparation of a series of racemic sulfoxides on three different amylose-based polysaccharide columns. Two of them have the amylose units modified with dimethylphenyl carbamoyl groups (Chiralpak AD-H and Chiralpak IA), while the third one possesses a carbamoyl moiety with an additional chiral centre (Chiralpak AS-H). The enantioseparation of selected analytes was achieved in high-performance liquid chromatography (HPLC) and the full analyte set was enantiomerically resolved using supercritical fluid chromatography (SFC). Comparing the results obtained in both modes, we show that enantioseparation under SFC conditions is superior to HPLC mode in terms of speed, while retaining excellent enantioselectivity and resolution. Faster elution of analytes was observed on increasing the polarity of the co-solvent (modifier) in the mobile phase. This trend is apparent in both chromatographic modes. Documenting the important role of the additional chiral centre, Chiralpak AS-H provided the best chromatographic parameters resulting in the enantioseparation of all analytes.

Photosensitive liquid crystals are of contemporary interest not only from the scientific point of view but also for various applications. Herein we report the first photosensitive materials based on laterally substituted 3-hydroxybenzoic acid. The molecular self-assembly of these new materials was characterized using different physical techniques including differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements, electro-optical investigations and dielectric spectroscopy. We show that the number and position of azo units with respect to the lateral substitution on the molecular core significantly influence mesomorphic properties of the materials. Based on the position of the substituent, either non-polar or polar smectic C phases are formed. The optimum combination of both the structural elements results in an achiral material which shows a broad polymorphism and exhibits a stable dark-conglomerate crystalline phase with macroscopically chiral domains at room temperature. The structure of this phase differs from the previously described fluid sponge-like distorted smectic phases as well as from helical nano-filament phases, thus, adding new information on the possible variations in the nanostructures of this kind of phase. Moreover, the photosensitivity of these materials has been studied using 1H NMR spectroscopy.

•Modifier amount in supercritical CO2 marks boundaries between chromatographic modes.•Enantioseparation of acids, bases and ampholytes on chiral zwitterionic ion-exchanger.•The effect of intrinsic counter-ion and transient acid on analyte elution clarified.•Enhanced-fluidity chromatography - new area for optimization using zwitterionic phase.Major differences in the chromatographic performance of a zwitterion ion-exchange type (ZWIX) chiral stationary phase (CSP) in supercritical fluid chromatography (SFC) and high-performance liquid chromatography (HPLC) have been observed. To explain these differences, transition from HPLC to SFC conditions has been performed. The amount of a protic organic modifier in supercritical carbon dioxide (scCO2) was stepwise increased and the effect of this change studied using acidic, basic and ampholytic analytes. At the same time, the effect of various basic additives to the mobile phase and transient acidic buffer species, formed by the reaction of scCO2 with the organic modifier and additives, was assessed. Evidence is provided that a transient acid together with the intrinsic counter-ions present in the ZWIX selector structure drive the elution of analytes even when no buffer is employed. We show that the tested analytes can be enantioseparated under both SFC and HPLC conditions; the best conditions for the resolution of ampholytes are in the so-called enhanced-fluidity mobile phase region. As a consequence, subcritical fluid and enhanced-fluidity mobile phase regions seem to be chromatographic modes with a high potential for operating ZWIX CSPs.

The mechanistic aspects of the one-pot C-acylation of cyclic 1,3-diones are discussed. Using various substituted carboxylic acids, coupling agents and basic catalysts we aim to describe the process of direct transfer of an acyl group to the activated C-2 carbon of dimedone and 1,3-cyclohexanedione. The course of acylation was studied by high-performance liquid chromatography as well as on-line infrared spectroscopy. The results indicate that the direct acylation follows a nucleophilic acyl substitution mechanism rather than a nucleophilic attack on a ketene intermediate formed in situ from the activated carboxylic acid.

•The influence of modifier content in scCO2 on the in situ formed acid was evaluated.•Effect of additives on chromatographic performance in SFC/HPLC is described.•Step-wise modification of subcritical fluid with a modifier was studied.•Comparison of in situ formed buffer salt and related buffers in SFC mode is discussed.The performance of a strong cation exchange-type (SCX) chiral stationary phase (CSP) was evaluated with subcritical fluid chromatography (subFC) and high performance liquid chromatography (HPLC). The chromatographic conditions in subFC were optimized by changing the amount of polar organic modifier, concentration of a basic additive in the modifier, system pressure and temperature. In this way the concentration of in situ formed transient ionic species could be varied. The gradual change of the concentration of the transient buffer, i.e. gradient elution conditions in subFC, was found beneficial for separation of a mixture of racemic compounds. The strength and amount of the in situ formed buffer was estimated on the basis of comparative experiments in subSFC and HPLC.

All-organic paramagnetic liquid crystals offer the advantage of a long-range order of liquid crystalline phases and the magnetic properties of the individual molecules. In such systems, the magnetic properties can be modified by phase transition or the application of external fields. This manuscript reports on paramagnetic all-organic bent-core liquid crystals having the radical-bearing unit (TEMPO) in the terminal position of an elongating side arm. The mesomorphic properties of the materials are ensured by the optimized molecular structure. The paramagnetic nature of the mesogenic materials is investigated by electron paramagnetic resonance, the magnetic properties of the bulk materials are studied by SQUID magnetometry. It is shown that the materials preserve their magnetic properties within the whole temperature range of liquid crystalline behaviour. Moreover, a strong correlation between spin orientation and molecular alignment within different mesophases has been observed, however, SQUID measurements do not provide evidence about spin glass formation. Unlike materials presented thus far, the position of the spin unit has a plausible effect on the formation of mesophases leading to unique polymorphism of the studied paramagnetic compounds. For two six-ring hockey-stick-like compounds, polymorphism with four different mesophases, including two B1Rev-type phases, has been found in a broad temperature range (about 20 °C each). Thus, for the first time, such behaviour is described for all-organic paramagnetic bent-core liquid crystals.