Tetrahedron Letters
Novel supramolecular liquid crystals: synthesis and mesomorphic
properties of calix[4]arene-cholesterol derivatives
a
a,b,
⇑
a
a
Hongyu Guo , Fafu Yang
, Weiwei Liu , Jianbin Lai
a
College of Chemistry and Chemical Engineering, Fujian Normal University, Fuzhou 350007, PR China
Fujian Key Laboratory of Polymer Materials, Fuzhou 350007, PR China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
The first calix[4]arene-cholesterol liquid crystals were designed and synthesized in yields of 50–80%.
Structural and conformational characterization of these new compounds had been achieved by NMR,
MS, and elemental analysis. Their liquid crystalline behaviors were studied by polarizing optical micros-
copy, differential scanning calorimetry, and X-ray diffraction. All calix[4]arene derivatives with two or
four cholesterol units show excellent mesomorphic properties of the columnar molecular arrangement
of the calixarenes bowlic columns with cholesterol units as ancillary lateral columns. The long spacer
and more cholesterol units were favorable for excellent mesophase.
Received 13 November 2014
Revised 14 December 2014
Accepted 29 December 2014
Available online xxxx
Keywords:
Calixarene
Cholesterol
Synthesis
Ó 2015 Published by Elsevier Ltd.
Mesophase
Since Reinitzer reported his famous article on cholesteric liquid
crystal (LC) in 1888, all kinds of LC materials were studied and
ent structures and interesting mesomorphic properties.24–27 These
researches suggested that the mesomorphic properties of calixa-
rene LCs were mainly controlled by the structures of liquid crystal
units. The spacers also made a difference on the molecular stacking
behaviors of mesophase. On the other hand, it was well-known
that cholesteric LCs have attracted considerable attention owing
to their unique properties, such as selective reflection of circularly
polarized light, high optical rotator power, circular dichroism and
1
exhibited diverse physical properties of broad interest for both
basic research and applied sciences, such as organic light-emitting
diodes, organic field-effect transistors, organic photovoltaic cells,
2
–6
and gas sensors.
From then on, the design and synthesis of var-
ious liquid crystalline materials are interesting and challenging
works for the chemists. Recently, much research attention was
paid to the macrocycle-based liquid crystals. The mesomorphic
properties of this kind of molecules could be tuned by the com-
plexation behaviors of macrocycle units. For examples, Cammidge
reported the triphenylene dimers containing a shape-persistent
conjugated macrocycle or crown ether macrocycle with interesting
mesomorphic properties.7 Peng and Laschat, respectively, also
studied the syntheses and properties of similar triphenylene
dimers containing conjugated macrocycle or crown ether macrocy-
2
8–31
electrooptic effect.
Cholesterol was used as an excellent
structural unit to construct all kinds of liquid crystalline materials
6
,32–34
with interesting mesomorphic properties.
Lately, two new
cholesteryl derivatives of calix[4]arene were described as
a
mechano-responsive molecular gels, but no liquid crystalline
,8
35
property was investigated. In the present study, we wish to
report the design, syntheses, and mesomorphic properties of the
first examples of cholesterol-based calixarene liquid crystals.
The synthetic routes for calix[4]arene-cholesterol liquid crystals
3a, 3b, 4a, and 4b are illustrated in Scheme 1. Due to the substi-
tuted patterns of calix[4]arene and the length of spacers making
9
,10
cle.
Our group also described an interesting example of cyclo-
11
dextrin-triphenylene liquid crystal lately.
Calixarenes, possessing tunable 3D-shaped cavities, are the
important supramolecular platforms after crown ether and cyclo-
2
4–27
great influences on mesomorphic properties,
1,3-bis-substi-
1
2
dextrin. Various calixarene derivatives with special properties
tuted and tetra-substituted calix[4]arenes with different alkyl
bridging chains were designed as target molecules. By reacting
were designed and synthesized up to now.1
3–17
Calixarene-based
liquid crystals were also studied by introducing the long alkyl
cholesterol with 2-chloroacetic acid or 4-chlorobutanoic acid in
chains on calixarene skeleton.1
8–23
Recently, our group presented
using N,N -dicyclohexylcarbodiimide (DCC) as coupling
0
2
CH Cl
2
series of triphenylene-based calixarene liquid crystals with differ-
reagent and 4-dimethylaminopyridine (DMAP) as catalyst, the
cholesterol chlorinated derivatives 2a and 2b were obtained in
yields of 90% and 88%, respectively. Subsequently, the novel choles-
terol-1,3-bis-substituted calix[4]arene derivatives 3a and 3b were
⇑
040-4039/Ó 2015 Published by Elsevier Ltd.
0