Chromonic liquid crystals (CLC) are lyotropic phases formed by discotic mesogens in water. Simple chiral dopants such as amino acids have been reported to turn chromonic liquid crystals into their cholesteric counterparts. Here we report a chirality amplification effect in the nematic phase of a 9 wt% disodium cromoglycate (DSCG) lyotropic liquid crystal (LLC) upon doping with a water-soluble codeine derivative. The transition on cooling the isotropic to the nematic phase showed the presence of homochiral spindle-shaped droplets (tactoids). NMR DOSY experiments on a triple gradient probe revealed a small degree of diffusion anisotropy for the alkaloid embedded in the liquid crystal structure. These results in combination with XRD, CD and POM experiments agree with a supramolecular aggregation model based on simple columnar stacks.
Disodium Cromoglycate (DSCG), a lyotropic liquid crystal in water, is shown to be an amplifier of chirality when doped with small chiral molecules. Here, we study the behaviour of the DSCG nematic phase in the presence of three aminoacids with different degrees of protonation: L-Alanine, L-Arginine·HCl and L-Arginine. The results demonstrate that the sign of the helicity of the doped nematic phase (i.e., a cholesteric phase) depends on the sign of the Helical Twisting Power of the dopant.
Disodium Cromoglycate (DSCG), a lyotropic liquid crystal in water, is shown to be an amplifier of chirality when doped with small chiral molecules. Here, we study the behaviour of the DSCG nematic phase in the presence of three aminoacids with different degrees of protonation: L-Alanine, L-Arginine·HCl and L-Arginine. The results demonstrate that the sign of the helicity of the doped nematic phase (i.e., a cholesteric phase) depends on the sign of the Helical Twisting Power of the dopant.
The X-ray crystal structure of the gelator 1,3:2,4-dibenzylidene-D-sorbitol (DBS) is reported here. DBS is an important gelating molecule known for nearly 130 years, that has eluded crystallization until now. The crystal obtained presents an axial stacking of DBS molecules stabilized by both Van der Waals interactions and intermolecular hydrogen bonds of the side chain hydroxyl groups with either neighboring DBS or water molecules. The crystal structure shows definitive evidence for the frequently assumed “butterfly” type aggregation mode and experimentally proves the equatorial placement of the phenyl rings. The conformation of DBS has been analyzed in the crystal structure and compared with that determined in solution through NMR spectroscopy.
The X-ray crystal structure of the gelator 1,3:2,4-dibenzylidene-D-sorbitol (DBS) is reported here. DBS is an important gelating molecule known for nearly 130 years, that has eluded crystallization until now. The crystal obtained presents an axial stacking of DBS molecules stabilized by both Van der Waals interactions and intermolecular hydrogen bonds of the side chain hydroxyl groups with either neighboring DBS or water molecules. The crystal structure shows definitive evidence for the frequently assumed “butterfly” type aggregation mode and experimentally proves the equatorial placement of the phenyl rings. The conformation of DBS has been analyzed in the crystal structure and compared with that determined in solution through NMR spectroscopy.
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