XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
321
T7: P–1
NMR analysis of chiral center of antiferroelectric liquid crystals
Anna Drzewicz
1
, Marzena Tykarska
1
, Mateusz Szala
1
, and Magdalena Żurowska
1
1
Institute of Chemistry, Faculty of Advanced Technologies and Chemistry, Military University of
Technology, Sylwester Kaliski Str. 2, 00-908 Warsaw, Poland, e-mail: anna.drzewicz@wat.edu.pl
The macroscopic helicoidal structure of chiral liquid crystals by the presence of assymetric
carbon atom has been created. The knowledge of helix parameters, like the helical pitch and the
helical twist sense, is useful in the display applications. Unfortunately Gray and McDonnell
theory, in which the helical twist sense depends on the type of absolute configuration of
assymetric carbon atom and its position relative to the rigid core, do not explain the inversion of
helical handedness. This phenomenon by the presence of different conformers promoting
opposite helical twist sense has been demystified [1–3].
The aim of this work was the analysis of NMR spectra of chiral liquid crystalline esters (Fig.
1), which allows to determine the conformer structures of tested compounds with different type
of the helicoidal structure in the antiferroelectric phase. These compounds differ in the length of
non-chiral and chiral chains as well as the substitution of the benzene ring by fluorine atoms.
As a result from the NMR spectra the bigger change of value of chemical shifts has been
obtained for chiral carbon atom on 13C NMR spectra and for proton directly connected with this
atom on 1H NMR spectra.
COOC*HC
m
H
2m+1
C
n
H
2n+1
C
3
F
7
CH
2
O(CH
2
)
r
O
X
2
COO
X
1
Fig. 1. The general structure of used compounds,
where m = 5 or 6; X = H or F; Y = H or F; r = 5 or 6; s = 1 or 2.
Keywords: liquid crystals; helical pitch; helical twist sense; NMR spectra
Acknowledgment
The research was conducted as a part of the project RMN 08 687.
References
[1] A. Slaney, I. Nishiyama, P. Styring, J.W. Goodby, J. Mater. Chem. 2(8) (1992) 805.
[2] B. Cieplak, A. Kocot, K. Merkel, R. Wrzalik, R. Praniuk, Ferroelectrics 311 (2004) 83.
[3] M. Tykarska, M. Czerwiński, Liq. Cryst. 43(4) (2016) 462.
XIV
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International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
322
T8: P–1
Non-covalent interactions between thio-caffeine derivatives
and water-soluble porphyrin in ethanol-water environment
Agnieszka Lipke
1
, Magdalena Makarska-Białokoz
1
, Arleta Sierakowska
2
,
and Beata Jasiewicz
2
1
Faculty of Chemistry, Maria Curie-Sklodowska University, M. Curie-Sklodowska Sq. 2, 20-031
Lublin, Poland, e-mail: makarska@hektor.umcs.lublin.pl, agnieszka.lipke@poczta.umcs.lublin.pl
2
Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland
The thio-caffeine derivatives were found to be highly potent cytoprotective agents, what
predestines this class of compounds to act as effective antioxidants for preventing oxidative-
stress induced diseases or artheriosclerosis [1]. Whereas water-soluble cationic porphyrins, the
group of fluorescent macrocyclic compounds presenting the specific spectroscopic and redox
properties, can play the role of sensing materials to detect different, especially biologically
active substances, presented in aqueous environment [2].
To determine the binding interactions and ability to form the non-covalent systems, the
association process between 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-
porphine tetra-p-tosylate (H
2
TTMePP) and a series of five structurally diverse thio-caffeine
analogues has been studied in ethanol-water solution, analyzing its absorption and steady-state
fluorescence spectra. The fluorescence lifetimes and the quantum yields of the porphyrin in the
systems studied were established as well. The fluorescence quenching effect observed during
interaction of this porphyrin with thio-caffeine compounds, as well as the order of binding and
fluorescence quenching constants suggest the existence of the mechanism of static quenching
due to the formation of non-covalent and non-fluorescent stacking complexes. The obtained
results can be potentially useful from scientific, therapeutic or environmental points of view.
Fig. 1. Quenching effect of 8-bromocaffeine (starting compound in thio-caffeine derivatives synthesis) on
5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine tetra p-tosylate (H2TTMePP)
Keywords: Thio-caffeine derivatives; Water-soluble porphyrin; Non-covalent interactions
Acknowledgment
The research was carried out with the equipment purchased thanks to the financial support of the European
Regional Development Fund in the framework of the Operational Program Development of Eastern Poland
2007-2013 (Contract No. POPW 01.03.00-06-017/09).
References
[1] B. Jasiewicz, A. Sierakowska, N. Wandyszewska, B. Warżajtis, U. Rychlewska, R. Wawrzyniak, L.
Mrówczyńska, Bioorg. Med. Chem. Lett. 26 (2016) 3994.
[2] M. Makarska-Białokoz, J. Fluoresc. 22 (2012) 1521.
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