%0 Generic
%A Yang, Mei
%A Mallick, Bert
%A Mudring, Anja-Verena
%D 2014
%T A Systematic Study on
the Mesomorphic Behavior of
Asymmetrical 1‑Alkyl-3-dodecylimidazolium Bromides
%U https://acs.figshare.com/articles/dataset/A_Systematic_Study_on_the_Mesomorphic_Behavior_of_Asymmetrical_1_Alkyl_3_dodecylimidazolium_Bromides/2309773
%R 10.1021/cg401396n.s002
%2 https://ndownloader.figshare.com/files/3947395
%K room temperature IL
%K nonclassical hydrogen bonds
%K C 2C
%K dodecyl side chain
%K ILC
%K bromide
%K 6C
%K NMR
%K compounds C 2C
%K crystal
%K mesophase formation
%K arrangement
%K imidazolium head groups
%X To
determine the essential parameters for mesophase formation in
imidazolium-based ionic liquids (ILs), a library of 1-alkyl-3-dodecylimidazolium
bromides was synthesized, abbreviated as CnC12, where 0 ≤ n ≤ 13, as the general notion is that a dodecyl side
chain would guarantee the formation of an ionic liquid crystal (ILC).
All salts were fully characterized by NMR spectroscopy and mass spectrometry.
Their thermal properties were recorded, and mesophase formation was
assessed. An odd–even effect is observed for 5 ≤ n ≤ 10 in the temperatures of melting transitions.
While the majority of this series, as expected, formed mesophases,
surprisingly compounds C2C12 and C6C12 could not be classified as
ILCs, the latter being a room temperature IL, while C2C12 is a crystalline
solid with melting point at 37 °C. The single crystal structure
of compound 1-ethyl-3-dodecylimidazolium bromide (C2C12) was successfully
obtained. Remarkably, the arrangement of imidazolium cores in the
structure is very complicated due to multiple nonclassical hydrogen
bonds between bromide anions and imidazolium head groups. In this
arrangement, neighboring imidazolium rings are forced by hydrogen
bonds to form a “face-to-face” conformation. This seems
to be responsible for the elimination of a mesophase. To conclude,
the general view of a dodecyl chain being a functional group to generate
a mesophase is not entirely valid.
%I ACS Publications