Orientational effects of h-bonding in the chirality transfer from (2R,3R)-(-)-2,3-butandiol to polar nematic liquid crystal

The dielectric and orientational properties of solutions of chiral (2R, 3R) - (-) 2,3-butanediol and its racemic mixture in a liquid-crystalline mixture of alkoxycyanobiphenyls (CB6) were studied. The introduction of the chiral diol leads to the formation of a spiral nematic mesophase with the formation of a "fingerprints" texture. The introduction of dopants was shown to be accompanied by a decrease in the dielectric anisotropy of the mesophase. (2R, 3R) - (-) 2,3-butanediol provides the most noticeable decrease as a result of chiral phase induction. From the NMR spectroscopy data, an increase in the ordering of the nematic phase during modification was observed. On the base of Kirkwood's correlation parameter analysis a change in associative state of the mesophase concerned with the formation of H-complexes alkoxycyanobiphenyl-butanediol was shown. By the of quantum chemical calculations, optimized structures of 1:1 and 2:1 supermolecules were obtained, their dipole moments and C-13 NMR spectra were calculated. By comparing these data with experimental spectra, a conclusion was made about the predominance of trimolecular complexes with hydrogen bond. (C) 2018 Elsevier B.V. All rights reserved.