TY  - JOUR
A1  - Bauer, Monika
A1  - Hartmann, Lutz
A1  - Kleinpeter, Erich
A1  - Kuschel, Frank
A1  - Pithart, Cornelia
A1  - Weissflog, Wolfgang
T1  - Chiral Dopants Derived from Ephedrine/Pseudoephedrine: Structure and Medium Effects on the Helical Twisting Power
JF  - Molecular crystals and liquid crystals
N2  - Chiral dopants were obtained by acylation of enantiomerically pure ephedrine and pseudoephedrine with promesogenic carbonyl reagents. The products have been investigated with respect to their chiral transfer ability on nematic host matrices characterized by extreme differences of the dielectric anisotropy. It has been found that the medium dependence of the helicity induction nearly disappears at reduced temperatures. Based on variable temperature H-1 NMR studies on monoacylated homologues, the estimated coalescence temperatures and free activation enthalpies for the hindered rotation around C-N bonds could be correlated with the helical twisting power. Measurements by dielectric spectroscopy reveal the correlation between the molar mass of substituents linked to the chiral building block and the dynamic glass transition of corresponding chiral dopants. Furthermore, the effect of intramolecular and intermolecular hydrogen bonds has been studied by ATR-FTIR spectroscopy.
KW  - ephedrine/pseudoephedrine
KW  - Chiral dopants
KW  - ATR-FTIR
KW  - molecular structure
KW  - dielectric spectroscopy
KW  - H-1 NMR
Y1  - 2015
U6  - https://doi.org/10.1080/15421406.2014.949592
SN  - 1542-1406
SN  - 1563-5287
VL  - 608
IS  - 1
SP  - 14
EP  - 24
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  -