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  - 
TY  - JOUR
A1  - Wojnarowska, Zaneta
A1  - Lange, Alyna
A1  - Taubert, Andreas
A1  - Paluch, Marian
T1  - Ion and proton transport in aqueous/nonaqueous acidic tonic liquids for fuel-cell applications-insight from high-pressure dielectric studies
JF  - ACS applied materials & interfaces / American Chemical Society
N2  - The use of acidic ionic liquids and solids as electrolytes in fuel cells is an emerging field due to their efficient proton conductivity and good thermal stability. Despite multiple reports describing conducting properties of acidic ILs, little is known on the charge-transport mechanism in the vicinity of liquid-glass transition and the structural factors governing the proton hopping. To address these issues, we studied two acidic imidazolium-based ILs with the same cation, however, different anions-bulk tosylate vs small methanesulfonate. High-pressure dielectric studies of anhydrous and water-saturated materials performed in the close vicinity of T-g have revealed significant differences in the charge-transport mechanism in these two systems being undetectable at ambient conditions. Thereby, we demonstrated the effect of molecular architecture on proton hopping, being crucial in the potential electrochemical applications of acidic ILs.
KW  - proton hopping
KW  - dielectric spectroscopy
KW  - high pressure
KW  - ion transport
KW  - acidic ionic liquids
Y1  - 2021
U6  - https://doi.org/10.1021/acsami.1c06260
SN  - 1944-8244
SN  - 1944-8252
VL  - 13
IS  - 26
SP  - 30614
EP  - 30624
PB  - American Chemical Society
CY  - Washington
ER  -