Average Orientation of Benzyl-d₅ Alkyl Ethers in Cationic Nematic Lyomesophases

Abstract

Deuterium quadrupole splittings from the aromatic ring of a series of linear benzyl-d 5 alkyl ethers, with alkyl chain length from 1 to 15 carbon atoms, have been measured using 2H-NMR spectroscopy. These molecules, 20% pentadeuteriated in the aromatic ring, were incorporated into type II cationic nematic lyotropic liquid crystals, made from tetradecyltrimethylammonium bromide (TDTMABr) and hexadecylpyridinium chloride (HDPyCl). Using these 2H quadrupole splittings, the two order parameters that completely describe the average orientation of the aromatic ring with respect to the direction of the magnetic field were estimated. Addition of these molecules did not have any appreciable effect on the integrity of either mesophase. An increase in the mobility of the Y molecular symmetry axis of the ring, on going from C1 to C2, is observed in both mesophases. This observation suggest that the aromatic ring plane of benzyl methyl ether is oriented nearly parallel to the bilayer surface, although in HDPyCl it seems to be more mobile. As the alkyl chain length increases, progressive incorporation of the aromatic ring into the superstructure is observed. The opposite tendency of the quadrupole splitting of water between TDTMABr and HDPyCl is explained in terms of the location and orientation of the aromatic ring of the guest molecules and the symmetry and solvation capabilities of the head groups.

Structure and Aggregation Number of a Lyotropic Liquid Crystal: A Fluorescence Quenching and Molecular Dynamics Study

“…DeOH-α- d 2 was prepared by reduction of the ethyl ester of decanoic acid with LiAlD 4 . The mesophase with bromide instead of chloride as counterion had been prepared before, and the composition employed in this work (with chloride) is very similar. Polarized light microscopy and 2 H NMR quadrupole splittings were employed to characterize the mesophase.…”

Average Orientation and Location of Benzyl Alcohol-d5 and Alkyl Benzyl-d5 Ethers in Anionic Nematic Lyotropic Liquid Crystals

“…These normalized quadrupole splittings will be independent of the particular effect of each added guest molecule on the integrity of the aggregate. Using previously reported values for the aromatic deuterium quadrupole coupling constant, electric field asymmetry parameter, and geometrical parameters, the two order parameters, S xx and S yy , which completely describe the average orientation of the aromatic ring, were calculated. , Figure shows the structure of the studied molecules and the labels of the molecular symmetry axes. The values of S xx and S yy appear in Table , while Figures and provide a graphical representation of these normalized order parameters for both NaDS and CsDS.…”

“…The ether series, 20% d 5 , was synthesized starting from a mixture of 80% benzyl alcohol and 20% benzyl alcohol- d 5 (99%), both commercially available reagents. More details of the procedure were described in a previous paper …”

“…In both cases, the symmetry axis of the ring is perpendicular to the bilayer surface. In addition, a nonionic aromatic ring, such as that found in benzyl methyl ether, appears to interact strongly in cationic liquid crystals formed from TDTMABr and seems to be oriented with the aromatic ring plane lying on the micellar surface, evidencing the existence of cation−π interaction …”

Differential Incorporation of l- and d-N-Acyl-1-phenyl-d5-2-aminopropane in a Cesium N-Dodecanoyl-l-alaninate Cholesteric Nematic Lyomesophase

“…One of the simplest methods to estimate the average alignment of ions and molecules in anisotropic media, such as an oriented bilayer, is by using order parameters derived from the 2 H NMR spectra of specifically labeled molecules. In the past, we have studied the solubilization process of a number of ions and molecules in cationic and anionic nematic lyotropic liquid crystals, using deuterium quadrupole splittings of deuterated aromatic rings. ,− In this work, we have employed 2 H NMR spectroscopy to measure the deuterium quadrupole splittings from the fully deuterated aromatic ring of two series of seven optical isomers each, l - and d - N -acyl-1-phenyl-2-aminopropane, 40% d 5 . Both series contain linear acyl substituents ranging from 1 to 10 carbon atoms and were dissolved in a nematic cholesteric lyomesophase prepared using cesium N -dodecanoyl- l -alaninate (CsD- l -Ala) as the main surfactant component, providing the chiral interface.…”